diff --git a/integration/proxy/proxy_helpers.go b/integration/proxy/proxy_helpers.go
index 726568e34d46e..7fff7e9a54100 100644
--- a/integration/proxy/proxy_helpers.go
+++ b/integration/proxy/proxy_helpers.go
@@ -53,7 +53,7 @@ import (
 	"github.com/gravitational/teleport/api/utils/retryutils"
 	"github.com/gravitational/teleport/integration/helpers"
 	"github.com/gravitational/teleport/lib"
-	"github.com/gravitational/teleport/lib/auth"
+	"github.com/gravitational/teleport/lib/auth/join"
 	"github.com/gravitational/teleport/lib/auth/state"
 	"github.com/gravitational/teleport/lib/client"
 	"github.com/gravitational/teleport/lib/defaults"
@@ -664,7 +664,7 @@ func mustRegisterUsingIAMMethod(t *testing.T, proxyAddr utils.NetAddr, token str
 	require.NoError(t, err)
 
 	node := uuid.NewString()
-	_, err = auth.Register(context.TODO(), auth.RegisterParams{
+	_, err = join.Register(context.TODO(), join.RegisterParams{
 		Token: token,
 		ID: state.IdentityID{
 			Role:     types.RoleNode,
diff --git a/lib/auth/auth.go b/lib/auth/auth.go
index aedc4938cffa4..0ec085c293db6 100644
--- a/lib/auth/auth.go
+++ b/lib/auth/auth.go
@@ -52,7 +52,6 @@ import (
 	"github.com/gravitational/trace"
 	"github.com/jonboulle/clockwork"
 	"github.com/prometheus/client_golang/prometheus"
-	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/exporters/otlp/otlptrace"
 	"golang.org/x/crypto/bcrypt"
 	"golang.org/x/crypto/ssh"
@@ -155,8 +154,6 @@ const (
 		"(hint: use 'tctl get roles' to find roles that need updating)"
 )
 
-var tracer = otel.Tracer("github.com/gravitational/teleport/lib/auth")
-
 var ErrRequiresEnterprise = services.ErrRequiresEnterprise
 
 // ServerOption allows setting options as functional arguments to Server
diff --git a/lib/auth/bot_test.go b/lib/auth/bot_test.go
index e53e445ceafaf..4c54114a96522 100644
--- a/lib/auth/bot_test.go
+++ b/lib/auth/bot_test.go
@@ -42,6 +42,7 @@ import (
 	machineidv1pb "github.com/gravitational/teleport/api/gen/proto/go/teleport/machineid/v1"
 	"github.com/gravitational/teleport/api/types"
 	"github.com/gravitational/teleport/lib/auth/authclient"
+	"github.com/gravitational/teleport/lib/auth/join"
 	"github.com/gravitational/teleport/lib/auth/machineid/machineidv1"
 	"github.com/gravitational/teleport/lib/auth/state"
 	"github.com/gravitational/teleport/lib/auth/testauthority"
@@ -118,7 +119,7 @@ func TestRegisterBotCertificateGenerationCheck(t *testing.T) {
 	tlsPublicKey, err := tlsca.MarshalPublicKeyFromPrivateKeyPEM(sshPrivateKey)
 	require.NoError(t, err)
 
-	certs, err := Register(ctx, RegisterParams{
+	certs, err := join.Register(ctx, join.RegisterParams{
 		Token: token.GetName(),
 		ID: state.IdentityID{
 			Role: types.RoleBot,
@@ -191,7 +192,7 @@ func TestRegisterBotCertificateGenerationStolen(t *testing.T) {
 	tlsPublicKey, err := tlsca.MarshalPublicKeyFromPrivateKeyPEM(sshPrivateKey)
 	require.NoError(t, err)
 
-	certs, err := Register(ctx, RegisterParams{
+	certs, err := join.Register(ctx, join.RegisterParams{
 		Token: token.GetName(),
 		ID: state.IdentityID{
 			Role: types.RoleBot,
@@ -267,7 +268,7 @@ func TestRegisterBotCertificateExtensions(t *testing.T) {
 	tlsPublicKey, err := tlsca.MarshalPublicKeyFromPrivateKeyPEM(sshPrivateKey)
 	require.NoError(t, err)
 
-	certs, err := Register(ctx, RegisterParams{
+	certs, err := join.Register(ctx, join.RegisterParams{
 		Token: token.GetName(),
 		ID: state.IdentityID{
 			Role: types.RoleBot,
diff --git a/lib/auth/join/iam/endpoints.go b/lib/auth/join/iam/endpoints.go
new file mode 100644
index 0000000000000..3434ce30228b1
--- /dev/null
+++ b/lib/auth/join/iam/endpoints.go
@@ -0,0 +1,91 @@
+// Teleport
+// Copyright (C) 2024 Gravitational, Inc.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package iam
+
+import "sync"
+
+var (
+	// ValidSTSEndpoints holds a sorted list of all known valid public endpoints for
+	// the AWS STS service. You can generate this list by running
+	// $ go run github.com/nklaassen/sts-endpoints@latest --go-list
+	// Update aws-sdk-go in that package to learn about new endpoints.
+	ValidSTSEndpoints = sync.OnceValue(func() []string {
+		return []string{
+			"sts-fips.us-east-1.amazonaws.com",
+			"sts-fips.us-east-2.amazonaws.com",
+			"sts-fips.us-west-1.amazonaws.com",
+			"sts-fips.us-west-2.amazonaws.com",
+			"sts.af-south-1.amazonaws.com",
+			"sts.amazonaws.com",
+			"sts.ap-east-1.amazonaws.com",
+			"sts.ap-northeast-1.amazonaws.com",
+			"sts.ap-northeast-2.amazonaws.com",
+			"sts.ap-northeast-3.amazonaws.com",
+			"sts.ap-south-1.amazonaws.com",
+			"sts.ap-south-2.amazonaws.com",
+			"sts.ap-southeast-1.amazonaws.com",
+			"sts.ap-southeast-2.amazonaws.com",
+			"sts.ap-southeast-3.amazonaws.com",
+			"sts.ap-southeast-4.amazonaws.com",
+			"sts.ca-central-1.amazonaws.com",
+			"sts.ca-west-1.amazonaws.com",
+			"sts.cn-north-1.amazonaws.com.cn",
+			"sts.cn-northwest-1.amazonaws.com.cn",
+			"sts.eu-central-1.amazonaws.com",
+			"sts.eu-central-2.amazonaws.com",
+			"sts.eu-north-1.amazonaws.com",
+			"sts.eu-south-1.amazonaws.com",
+			"sts.eu-south-2.amazonaws.com",
+			"sts.eu-west-1.amazonaws.com",
+			"sts.eu-west-2.amazonaws.com",
+			"sts.eu-west-3.amazonaws.com",
+			"sts.il-central-1.amazonaws.com",
+			"sts.me-central-1.amazonaws.com",
+			"sts.me-south-1.amazonaws.com",
+			"sts.sa-east-1.amazonaws.com",
+			"sts.us-east-1.amazonaws.com",
+			"sts.us-east-2.amazonaws.com",
+			"sts.us-gov-east-1.amazonaws.com",
+			"sts.us-gov-west-1.amazonaws.com",
+			"sts.us-iso-east-1.c2s.ic.gov",
+			"sts.us-iso-west-1.c2s.ic.gov",
+			"sts.us-isob-east-1.sc2s.sgov.gov",
+			"sts.us-west-1.amazonaws.com",
+			"sts.us-west-2.amazonaws.com",
+		}
+	})
+
+	GlobalSTSEndpoints = sync.OnceValue(func() []string {
+		return []string{
+			"sts.amazonaws.com",
+			// This is not a real endpoint, but the SDK will select it if
+			// AWS_USE_FIPS_ENDPOINT is set and a region is not.
+			"sts-fips.aws-global.amazonaws.com",
+		}
+	})
+
+	FIPSSTSEndpoints = sync.OnceValue(func() []string {
+		return []string{
+			"sts-fips.us-east-1.amazonaws.com",
+			"sts-fips.us-east-2.amazonaws.com",
+			"sts-fips.us-west-1.amazonaws.com",
+			"sts-fips.us-west-2.amazonaws.com",
+			"sts.us-gov-east-1.amazonaws.com",
+			"sts.us-gov-west-1.amazonaws.com",
+		}
+	})
+)
diff --git a/lib/auth/join/iam/iam.go b/lib/auth/join/iam/iam.go
new file mode 100644
index 0000000000000..241d4ec7800c3
--- /dev/null
+++ b/lib/auth/join/iam/iam.go
@@ -0,0 +1,161 @@
+// Teleport
+// Copyright (C) 2024 Gravitational, Inc.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package iam
+
+import (
+	"bytes"
+	"context"
+	"log/slog"
+	"slices"
+	"strings"
+
+	awssdk "github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/aws/endpoints"
+	"github.com/aws/aws-sdk-go/aws/session"
+	"github.com/aws/aws-sdk-go/service/sts"
+	"github.com/gravitational/trace"
+
+	cloudaws "github.com/gravitational/teleport/lib/cloud/imds/aws"
+)
+
+const (
+	// AWS SignedHeaders will always be lowercase
+	// https://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-auth-using-authorization-header.html#sigv4-auth-header-overview
+	challengeHeaderKey = "x-teleport-challenge"
+)
+
+type stsIdentityRequestConfig struct {
+	regionalEndpointOption endpoints.STSRegionalEndpoint
+	fipsEndpointOption     endpoints.FIPSEndpointState
+}
+
+type stsIdentityRequestOption func(cfg *stsIdentityRequestConfig)
+
+func WithRegionalEndpoint(useRegionalEndpoint bool) stsIdentityRequestOption {
+	return func(cfg *stsIdentityRequestConfig) {
+		if useRegionalEndpoint {
+			cfg.regionalEndpointOption = endpoints.RegionalSTSEndpoint
+		} else {
+			cfg.regionalEndpointOption = endpoints.LegacySTSEndpoint
+		}
+	}
+}
+
+func WithFIPSEndpoint(useFIPS bool) stsIdentityRequestOption {
+	return func(cfg *stsIdentityRequestConfig) {
+		if useFIPS {
+			cfg.fipsEndpointOption = endpoints.FIPSEndpointStateEnabled
+		} else {
+			cfg.fipsEndpointOption = endpoints.FIPSEndpointStateDisabled
+		}
+	}
+}
+
+// getEC2LocalRegion returns the AWS region this EC2 instance is running in, or
+// a NotFound error if the EC2 IMDS is unavailable.
+func getEC2LocalRegion(ctx context.Context) (string, error) {
+	imdsClient, err := cloudaws.NewInstanceMetadataClient(ctx)
+	if err != nil {
+		return "", trace.Wrap(err)
+	}
+
+	if !imdsClient.IsAvailable(ctx) {
+		return "", trace.NotFound("IMDS is unavailable")
+	}
+
+	region, err := imdsClient.GetRegion(ctx)
+	return region, trace.Wrap(err)
+}
+
+func newSTSClient(ctx context.Context, cfg *stsIdentityRequestConfig) (*sts.STS, error) {
+	awsConfig := awssdk.Config{
+		UseFIPSEndpoint:     cfg.fipsEndpointOption,
+		STSRegionalEndpoint: cfg.regionalEndpointOption,
+	}
+	sess, err := session.NewSessionWithOptions(session.Options{
+		SharedConfigState: session.SharedConfigEnable,
+		Config:            awsConfig,
+	})
+	if err != nil {
+		return nil, trace.Wrap(err)
+	}
+
+	stsClient := sts.New(sess)
+
+	if slices.Contains(GlobalSTSEndpoints(), strings.TrimPrefix(stsClient.Endpoint, "https://")) {
+		// If the caller wants to use the regional endpoint but it was not resolved
+		// from the environment, attempt to find the region from the EC2 IMDS
+		if cfg.regionalEndpointOption == endpoints.RegionalSTSEndpoint {
+			region, err := getEC2LocalRegion(ctx)
+			if err != nil {
+				return nil, trace.Wrap(err, "failed to resolve local AWS region from environment or IMDS")
+			}
+			stsClient = sts.New(sess, awssdk.NewConfig().WithRegion(region))
+		} else {
+			const msg = "Attempting to use the global STS endpoint for the IAM join method. " +
+				"This will probably fail in non-default AWS partitions such as China or GovCloud, or if FIPS mode is enabled. " +
+				"Consider setting the AWS_REGION environment variable, setting the region in ~/.aws/config, or enabling the IMDSv2."
+			slog.InfoContext(ctx, msg)
+		}
+	}
+
+	if cfg.fipsEndpointOption == endpoints.FIPSEndpointStateEnabled &&
+		!slices.Contains(ValidSTSEndpoints(), strings.TrimPrefix(stsClient.Endpoint, "https://")) {
+		// The AWS SDK will generate invalid endpoints when attempting to
+		// resolve the FIPS endpoint for a region that does not have one.
+		// In this case, try to use the FIPS endpoint in us-east-1. This should
+		// work for all regions in the standard partition. In GovCloud, we should
+		// not hit this because all regional endpoints support FIPS. In China or
+		// other partitions, this will fail, and FIPS mode will not be supported.
+		const msg = "AWS SDK resolved invalid FIPS STS endpoint. " +
+			"Attempting to use the FIPS STS endpoint for us-east-1."
+		slog.InfoContext(ctx, msg, "resolved", stsClient.Endpoint)
+		stsClient = sts.New(sess, awssdk.NewConfig().WithRegion("us-east-1"))
+	}
+
+	return stsClient, nil
+}
+
+// CreateSignedSTSIdentityRequest is called on the client side and returns an
+// sts:GetCallerIdentity request signed with the local AWS credentials
+func CreateSignedSTSIdentityRequest(ctx context.Context, challenge string, opts ...stsIdentityRequestOption) ([]byte, error) {
+	cfg := &stsIdentityRequestConfig{}
+	for _, opt := range opts {
+		opt(cfg)
+	}
+
+	stsClient, err := newSTSClient(ctx, cfg)
+	if err != nil {
+		return nil, trace.Wrap(err)
+	}
+
+	req, _ := stsClient.GetCallerIdentityRequest(&sts.GetCallerIdentityInput{})
+	// set challenge header
+	req.HTTPRequest.Header.Set(challengeHeaderKey, challenge)
+	// request json for simpler parsing
+	req.HTTPRequest.Header.Set("Accept", "application/json")
+	// sign the request, including headers
+	if err := req.Sign(); err != nil {
+		return nil, trace.Wrap(err)
+	}
+	// write the signed HTTP request to a buffer
+	var signedRequest bytes.Buffer
+	if err := req.HTTPRequest.Write(&signedRequest); err != nil {
+		return nil, trace.Wrap(err)
+	}
+	return signedRequest.Bytes(), nil
+}
diff --git a/lib/auth/join/join.go b/lib/auth/join/join.go
new file mode 100644
index 0000000000000..367b091612ac5
--- /dev/null
+++ b/lib/auth/join/join.go
@@ -0,0 +1,796 @@
+// Teleport
+// Copyright (C) 2024 Gravitational, Inc.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package join
+
+import (
+	"context"
+	"crypto/tls"
+	"crypto/x509"
+	"log/slog"
+	"os"
+	"slices"
+	"time"
+
+	"github.com/gravitational/trace"
+	"github.com/jonboulle/clockwork"
+	log "github.com/sirupsen/logrus"
+	"go.opentelemetry.io/otel"
+	"golang.org/x/net/http2"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/credentials"
+
+	"github.com/gravitational/teleport"
+	"github.com/gravitational/teleport/api/breaker"
+	"github.com/gravitational/teleport/api/client"
+	"github.com/gravitational/teleport/api/client/proto"
+	"github.com/gravitational/teleport/api/constants"
+	apidefaults "github.com/gravitational/teleport/api/defaults"
+	"github.com/gravitational/teleport/api/metadata"
+	"github.com/gravitational/teleport/api/observability/tracing"
+	"github.com/gravitational/teleport/api/types"
+	"github.com/gravitational/teleport/api/utils/aws"
+	"github.com/gravitational/teleport/lib/auth/authclient"
+	"github.com/gravitational/teleport/lib/auth/join/iam"
+	"github.com/gravitational/teleport/lib/auth/state"
+	"github.com/gravitational/teleport/lib/circleci"
+	"github.com/gravitational/teleport/lib/cloud/imds/azure"
+	"github.com/gravitational/teleport/lib/cloud/imds/gcp"
+	"github.com/gravitational/teleport/lib/defaults"
+	"github.com/gravitational/teleport/lib/githubactions"
+	"github.com/gravitational/teleport/lib/gitlab"
+	"github.com/gravitational/teleport/lib/kubernetestoken"
+	"github.com/gravitational/teleport/lib/spacelift"
+	"github.com/gravitational/teleport/lib/srv/alpnproxy/common"
+	"github.com/gravitational/teleport/lib/tlsca"
+	"github.com/gravitational/teleport/lib/tpm"
+	"github.com/gravitational/teleport/lib/utils"
+)
+
+var tracer = otel.Tracer("github.com/gravitational/teleport/lib/auth/join")
+
+// HostCredentials is an interface for a client that can be used to get host
+// credentials. This interface is needed because lib/client cannot be imported
+// in lib/auth due to circular imports.
+type HostCredentials func(context.Context, string, bool, types.RegisterUsingTokenRequest) (*proto.Certs, error)
+
+// AzureParams is the parameters specific to the azure join method.
+type AzureParams struct {
+	// ClientID is the client ID of the managed identity for Teleport to assume
+	// when authenticating a node.
+	ClientID string
+}
+
+// RegisterParams specifies parameters
+// for first time register operation with auth server
+type RegisterParams struct {
+	// Token is a secure token to join the cluster
+	Token string
+	// ID is identity ID
+	ID state.IdentityID
+	// AuthServers is a list of auth servers to dial
+	AuthServers []utils.NetAddr
+	// ProxyServer is a proxy server to dial
+	ProxyServer utils.NetAddr
+	// AdditionalPrincipals is a list of additional principals to dial
+	AdditionalPrincipals []string
+	// DNSNames is a list of DNS names to add to x509 certificate
+	DNSNames []string
+	// PublicTLSKey is a server's public key to sign
+	PublicTLSKey []byte
+	// PublicSSHKey is a server's public SSH key to sign
+	PublicSSHKey []byte
+	// CipherSuites is a list of cipher suites to use for TLS client connection
+	CipherSuites []uint16
+	// CAPins are the SKPI hashes of the CAs used to verify the Auth Server.
+	CAPins []string
+	// CAPath is the path to the CA file.
+	CAPath string
+	// GetHostCredentials is a client that can fetch host credentials.
+	GetHostCredentials HostCredentials
+	// Clock specifies the time provider. Will be used to override the time anchor
+	// for TLS certificate verification.
+	// Defaults to real clock if unspecified
+	Clock clockwork.Clock
+	// JoinMethod is the joining method used for this register request.
+	JoinMethod types.JoinMethod
+	// ec2IdentityDocument is used for Simplified Node Joining to prove the
+	// identity of a joining EC2 instance.
+	ec2IdentityDocument []byte
+	// AzureParams is the parameters specific to the azure join method.
+	AzureParams AzureParams
+	// CircuitBreakerConfig defines how the circuit breaker should behave.
+	CircuitBreakerConfig breaker.Config
+	// FIPS means FedRAMP/FIPS 140-2 compliant configuration was requested.
+	FIPS bool
+	// IDToken is a token retrieved from a workload identity provider for
+	// certain join types e.g GitHub, Google.
+	IDToken string
+	// Expires is an optional field for bots that specifies a time that the
+	// certificates that are returned by registering should expire at.
+	// It should not be specified for non-bot registrations.
+	Expires *time.Time
+	// Insecure trusts the certificates from the Auth Server or Proxy during registration without verification.
+	Insecure bool
+}
+
+func (r *RegisterParams) checkAndSetDefaults() error {
+	if r.Clock == nil {
+		r.Clock = clockwork.NewRealClock()
+	}
+
+	if err := r.verifyAuthOrProxyAddress(); err != nil {
+		return trace.BadParameter("no auth or proxy servers set")
+	}
+
+	return nil
+}
+
+func (r *RegisterParams) verifyAuthOrProxyAddress() error {
+	haveAuthServers := len(r.AuthServers) > 0
+	haveProxyServer := !r.ProxyServer.IsEmpty()
+
+	if !haveAuthServers && !haveProxyServer {
+		return trace.BadParameter("no auth or proxy servers set")
+	}
+
+	if haveAuthServers && haveProxyServer {
+		return trace.BadParameter("only one of auth or proxy server should be set")
+	}
+
+	return nil
+}
+
+// Register is used to generate host keys when a node or proxy are running on
+// different hosts than the auth server. This method requires provisioning
+// tokens to prove a valid auth server was used to issue the joining request
+// as well as a method for the node to validate the auth server.
+func Register(ctx context.Context, params RegisterParams) (certs *proto.Certs, err error) {
+	ctx, span := tracer.Start(ctx, "Register")
+	defer func() { tracing.EndSpan(span, err) }()
+
+	if err := params.checkAndSetDefaults(); err != nil {
+		return nil, trace.Wrap(err)
+	}
+	// Read in the token. The token can either be passed in or come from a file
+	// on disk.
+	token, err := utils.TryReadValueAsFile(params.Token)
+	if err != nil {
+		return nil, trace.Wrap(err)
+	}
+
+	// add EC2 Identity Document to params if required for given join method
+	switch params.JoinMethod {
+	case types.JoinMethodEC2:
+		if !aws.IsEC2NodeID(params.ID.HostUUID) {
+			return nil, trace.BadParameter(
+				`Host ID %q is not valid when using the EC2 join method, `+
+					`try removing the "host_uuid" file in your teleport data dir `+
+					`(e.g. /var/lib/teleport/host_uuid)`,
+				params.ID.HostUUID)
+		}
+		params.ec2IdentityDocument, err = utils.GetRawEC2IdentityDocument(ctx)
+		if err != nil {
+			return nil, trace.Wrap(err)
+		}
+	case types.JoinMethodGitHub:
+		params.IDToken, err = githubactions.NewIDTokenSource().GetIDToken(ctx)
+		if err != nil {
+			return nil, trace.Wrap(err)
+		}
+	case types.JoinMethodGitLab:
+		params.IDToken, err = gitlab.NewIDTokenSource(os.Getenv).GetIDToken()
+		if err != nil {
+			return nil, trace.Wrap(err)
+		}
+	case types.JoinMethodCircleCI:
+		params.IDToken, err = circleci.GetIDToken(os.Getenv)
+		if err != nil {
+			return nil, trace.Wrap(err)
+		}
+	case types.JoinMethodKubernetes:
+		params.IDToken, err = kubernetestoken.GetIDToken(os.Getenv, os.ReadFile)
+		if err != nil {
+			return nil, trace.Wrap(err)
+		}
+	case types.JoinMethodGCP:
+		params.IDToken, err = gcp.GetIDToken(ctx)
+		if err != nil {
+			return nil, trace.Wrap(err)
+		}
+	case types.JoinMethodSpacelift:
+		params.IDToken, err = spacelift.NewIDTokenSource(os.Getenv).GetIDToken()
+		if err != nil {
+			return nil, trace.Wrap(err)
+		}
+	}
+
+	type registerMethod struct {
+		call func(ctx context.Context, token string, params RegisterParams) (*proto.Certs, error)
+		desc string
+	}
+
+	registerThroughAuth := registerMethod{registerThroughAuth, "with auth server"}
+	registerThroughProxy := registerMethod{registerThroughProxy, "via proxy server"}
+
+	registerMethods := []registerMethod{registerThroughAuth, registerThroughProxy}
+
+	if !params.ProxyServer.IsEmpty() {
+		log.WithField("proxy-server", params.ProxyServer).Debugf("Registering node to the cluster.")
+
+		registerMethods = []registerMethod{registerThroughProxy}
+
+		if proxyServerIsAuth(params.ProxyServer) {
+			log.Debugf("The specified proxy server appears to be an auth server.")
+		}
+	} else {
+		log.WithField("auth-servers", params.AuthServers).Debugf("Registering node to the cluster.")
+
+		if params.GetHostCredentials == nil {
+			log.Debugf("Missing client, it is not possible to register through proxy.")
+			registerMethods = []registerMethod{registerThroughAuth}
+		} else if authServerIsProxy(params.AuthServers) {
+			log.Debugf("The first specified auth server appears to be a proxy.")
+			registerMethods = []registerMethod{registerThroughProxy, registerThroughAuth}
+		}
+	}
+
+	var collectedErrs []error
+	for _, method := range registerMethods {
+		log.Infof("Attempting registration %s.", method.desc)
+		certs, err := method.call(ctx, token, params)
+		if err != nil {
+			collectedErrs = append(collectedErrs, err)
+			log.WithError(err).Debugf("Registration %s failed.", method.desc)
+			continue
+		}
+		log.Infof("Successfully registered %s.", method.desc)
+		return certs, nil
+	}
+	return nil, trace.NewAggregate(collectedErrs...)
+}
+
+// authServerIsProxy returns true if the first specified auth server
+// to register with appears to be a proxy.
+func authServerIsProxy(servers []utils.NetAddr) bool {
+	if len(servers) == 0 {
+		return false
+	}
+	port := servers[0].Port(0)
+	return port == defaults.HTTPListenPort || port == teleport.StandardHTTPSPort
+}
+
+// proxyServerIsAuth returns true if the address given to register with
+// appears to be an auth server.
+func proxyServerIsAuth(server utils.NetAddr) bool {
+	port := server.Port(0)
+	return port == defaults.AuthListenPort
+}
+
+// registerThroughProxy is used to register through the proxy server.
+func registerThroughProxy(
+	ctx context.Context,
+	token string,
+	params RegisterParams,
+) (certs *proto.Certs, err error) {
+	ctx, span := tracer.Start(ctx, "registerThroughProxy")
+	defer func() { tracing.EndSpan(span, err) }()
+
+	switch params.JoinMethod {
+	case types.JoinMethodIAM, types.JoinMethodAzure, types.JoinMethodTPM:
+		// IAM and Azure join methods require gRPC client
+		conn, err := proxyJoinServiceConn(ctx, params, params.Insecure)
+		if err != nil {
+			return nil, trace.Wrap(err)
+		}
+		defer conn.Close()
+
+		joinServiceClient := client.NewJoinServiceClient(proto.NewJoinServiceClient(conn))
+		switch params.JoinMethod {
+		case types.JoinMethodIAM:
+			certs, err = registerUsingIAMMethod(ctx, joinServiceClient, token, params)
+		case types.JoinMethodAzure:
+			certs, err = registerUsingAzureMethod(ctx, joinServiceClient, token, params)
+		case types.JoinMethodTPM:
+			certs, err = registerUsingTPMMethod(ctx, joinServiceClient, token, params)
+		default:
+			return nil, trace.BadParameter("unhandled join method %q", params.JoinMethod)
+		}
+
+		if err != nil {
+			return nil, trace.Wrap(err)
+		}
+	default:
+		// The rest of the join methods use GetHostCredentials function passed through
+		// params to call proxy HTTP endpoint
+		var err error
+		certs, err = params.GetHostCredentials(ctx,
+			getHostAddresses(params)[0],
+			params.Insecure,
+			types.RegisterUsingTokenRequest{
+				Token:                token,
+				HostID:               params.ID.HostUUID,
+				NodeName:             params.ID.NodeName,
+				Role:                 params.ID.Role,
+				AdditionalPrincipals: params.AdditionalPrincipals,
+				DNSNames:             params.DNSNames,
+				PublicTLSKey:         params.PublicTLSKey,
+				PublicSSHKey:         params.PublicSSHKey,
+				EC2IdentityDocument:  params.ec2IdentityDocument,
+				IDToken:              params.IDToken,
+				Expires:              params.Expires,
+			})
+		if err != nil {
+			return nil, trace.Wrap(err)
+		}
+	}
+	return certs, nil
+}
+
+// registerThroughAuth is used to register through the auth server.
+func registerThroughAuth(
+	ctx context.Context, token string, params RegisterParams,
+) (certs *proto.Certs, err error) {
+	ctx, span := tracer.Start(ctx, "registerThroughAuth")
+	defer func() { tracing.EndSpan(span, err) }()
+
+	var client *authclient.Client
+	// Build a client for the Auth Server with different certificate validation
+	// depending on the configured values for Insecure, CAPins and CAPath.
+	switch {
+	case params.Insecure:
+		log.Warnf("Insecure mode enabled. Auth Server cert will not be validated and CAPins and CAPath value will be ignored.")
+		client, err = insecureRegisterClient(params)
+	case len(params.CAPins) != 0:
+		// CAPins takes precedence over CAPath
+		client, err = pinRegisterClient(ctx, params)
+	case params.CAPath != "":
+		client, err = caPathRegisterClient(params)
+	default:
+		// We fall back to insecure mode here - this is a little odd but is
+		// necessary to preserve the behavior of registration. At a later date,
+		// we may consider making this an error asking the user to provide
+		// Insecure, CAPins or CAPath.
+		client, err = insecureRegisterClient(params)
+	}
+	if err != nil {
+		return nil, trace.Wrap(err)
+	}
+	defer client.Close()
+
+	switch params.JoinMethod {
+	// IAM and Azure methods use unique gRPC endpoints
+	case types.JoinMethodIAM:
+		certs, err = registerUsingIAMMethod(ctx, client, token, params)
+	case types.JoinMethodAzure:
+		certs, err = registerUsingAzureMethod(ctx, client, token, params)
+	case types.JoinMethodTPM:
+		certs, err = registerUsingTPMMethod(ctx, client, token, params)
+	default:
+		// non-IAM join methods use HTTP endpoint
+		// Get the SSH and X509 certificates for a node.
+		certs, err = client.RegisterUsingToken(
+			ctx,
+			&types.RegisterUsingTokenRequest{
+				Token:                token,
+				HostID:               params.ID.HostUUID,
+				NodeName:             params.ID.NodeName,
+				Role:                 params.ID.Role,
+				AdditionalPrincipals: params.AdditionalPrincipals,
+				DNSNames:             params.DNSNames,
+				PublicTLSKey:         params.PublicTLSKey,
+				PublicSSHKey:         params.PublicSSHKey,
+				EC2IdentityDocument:  params.ec2IdentityDocument,
+				IDToken:              params.IDToken,
+				Expires:              params.Expires,
+			})
+	}
+	return certs, trace.Wrap(err)
+}
+
+// proxyJoinServiceConn attempts to connect to the join service running on the
+// proxy. The Proxy's TLS cert will be verified using the host's root CA pool
+// (PKI) unless the --insecure flag was passed.
+func proxyJoinServiceConn(
+	ctx context.Context, params RegisterParams, insecure bool,
+) (*grpc.ClientConn, error) {
+	tlsConfig := utils.TLSConfig(params.CipherSuites)
+	tlsConfig.Time = params.Clock.Now
+	// set NextProtos for TLS routing, the actual protocol will be h2
+	tlsConfig.NextProtos = []string{string(common.ProtocolProxyGRPCInsecure), http2.NextProtoTLS}
+
+	if insecure {
+		tlsConfig.InsecureSkipVerify = true
+		log.Warnf("Joining cluster without validating the identity of the Proxy Server.")
+	}
+
+	// Check if proxy is behind a load balancer. If so, the connection upgrade
+	// will verify the load balancer's cert using system cert pool. This
+	// provides the same level of security as the client only verifies Proxy's
+	// web cert against system cert pool when connection upgrade is not
+	// required.
+	//
+	// With the ALPN connection upgrade, the tunneled TLS Routing request will
+	// skip verify as the Proxy server will present its host cert which is not
+	// fully verifiable at this point since the client does not have the host
+	// CAs yet before completing registration.
+	alpnConnUpgrade := client.IsALPNConnUpgradeRequired(ctx, getHostAddresses(params)[0], insecure)
+	if alpnConnUpgrade && !insecure {
+		tlsConfig.InsecureSkipVerify = true
+		tlsConfig.VerifyConnection = verifyALPNUpgradedConn(params.Clock)
+	}
+
+	dialer := client.NewDialer(
+		ctx,
+		apidefaults.DefaultIdleTimeout,
+		apidefaults.DefaultIOTimeout,
+		client.WithInsecureSkipVerify(insecure),
+		client.WithALPNConnUpgrade(alpnConnUpgrade),
+	)
+
+	conn, err := grpc.Dial(
+		getHostAddresses(params)[0],
+		grpc.WithContextDialer(client.GRPCContextDialer(dialer)),
+		grpc.WithUnaryInterceptor(metadata.UnaryClientInterceptor),
+		grpc.WithStreamInterceptor(metadata.StreamClientInterceptor),
+		grpc.WithTransportCredentials(credentials.NewTLS(tlsConfig)),
+	)
+	return conn, trace.Wrap(err)
+}
+
+func getHostAddresses(params RegisterParams) []string {
+	if !params.ProxyServer.IsEmpty() {
+		return []string{params.ProxyServer.String()}
+	}
+
+	return utils.NetAddrsToStrings(params.AuthServers)
+}
+
+// verifyALPNUpgradedConn is a tls.Config.VerifyConnection callback function
+// used by the tunneled TLS Routing request to verify the host cert of a Proxy
+// behind a L7 load balancer.
+//
+// Since the client has not obtained the cluster CAs at this point, the
+// presented cert cannot be fully verified yet. For now, this function only
+// checks if "teleport.cluster.local" is present as one of the DNS names and
+// verifies the cert is not expired.
+func verifyALPNUpgradedConn(clock clockwork.Clock) func(tls.ConnectionState) error {
+	return func(server tls.ConnectionState) error {
+		for _, cert := range server.PeerCertificates {
+			if slices.Contains(cert.DNSNames, constants.APIDomain) && clock.Now().Before(cert.NotAfter) {
+				return nil
+			}
+		}
+		return trace.AccessDenied("server is not a Teleport proxy or server certificate is expired")
+	}
+}
+
+// insecureRegisterClient attempts to connects to the Auth Server using the
+// CA on disk. If no CA is found on disk, Teleport will not verify the Auth
+// Server it is connecting to.
+func insecureRegisterClient(params RegisterParams) (*authclient.Client, error) {
+	log.Warnf("Joining cluster without validating the identity of the Auth " +
+		"Server. This may open you up to a Man-In-The-Middle (MITM) attack if an " +
+		"attacker can gain privileged network access. To remedy this, use the CA pin " +
+		"value provided when join token was generated to validate the identity of " +
+		"the Auth Server or point to a valid Certificate via the CA Path option.")
+
+	tlsConfig := utils.TLSConfig(params.CipherSuites)
+	tlsConfig.Time = params.Clock.Now
+	tlsConfig.InsecureSkipVerify = true
+
+	client, err := authclient.NewClient(client.Config{
+		Addrs: getHostAddresses(params),
+		Credentials: []client.Credentials{
+			client.LoadTLS(tlsConfig),
+		},
+		CircuitBreakerConfig: params.CircuitBreakerConfig,
+	})
+	if err != nil {
+		return nil, trace.Wrap(err)
+	}
+
+	return client, nil
+}
+
+// pinRegisterClient first connects to the Auth Server using a insecure
+// connection to fetch the root CA. If the root CA matches the provided CA
+// pin, a connection will be re-established and the root CA will be used to
+// validate the certificate presented. If both conditions hold true, then we
+// know we are connecting to the expected Auth Server.
+func pinRegisterClient(
+	ctx context.Context, params RegisterParams,
+) (*authclient.Client, error) {
+	// Build a insecure client to the Auth Server. This is safe because even if
+	// an attacker were to MITM this connection the CA pin will not match below.
+	tlsConfig := utils.TLSConfig(params.CipherSuites)
+	tlsConfig.InsecureSkipVerify = true
+	tlsConfig.Time = params.Clock.Now
+	authClient, err := authclient.NewClient(client.Config{
+		Addrs: getHostAddresses(params),
+		Credentials: []client.Credentials{
+			client.LoadTLS(tlsConfig),
+		},
+		CircuitBreakerConfig: params.CircuitBreakerConfig,
+	})
+	if err != nil {
+		return nil, trace.Wrap(err)
+	}
+	defer authClient.Close()
+
+	// Fetch the root CA from the Auth Server. The NOP role has access to the
+	// GetClusterCACert endpoint.
+	localCA, err := authClient.GetClusterCACert(ctx)
+	if err != nil {
+		return nil, trace.Wrap(err)
+	}
+	certs, err := tlsca.ParseCertificatePEMs(localCA.TLSCA)
+	if err != nil {
+		return nil, trace.Wrap(err)
+	}
+
+	// Check that the SPKI pin matches the CA we fetched over a insecure
+	// connection. This makes sure the CA fetched over a insecure connection is
+	// in-fact the expected CA.
+	err = utils.CheckSPKI(params.CAPins, certs)
+	if err != nil {
+		return nil, trace.Wrap(err)
+	}
+
+	for _, cert := range certs {
+		// Check that the fetched CA is valid at the current time.
+		err = utils.VerifyCertificateExpiry(cert, params.Clock)
+		if err != nil {
+			return nil, trace.Wrap(err)
+		}
+
+	}
+	log.Infof("Joining remote cluster %v with CA pin.", certs[0].Subject.CommonName)
+
+	// Create another client, but this time with the CA provided to validate
+	// that the Auth Server was issued a certificate by the same CA.
+	tlsConfig = utils.TLSConfig(params.CipherSuites)
+	tlsConfig.Time = params.Clock.Now
+	certPool := x509.NewCertPool()
+	for _, cert := range certs {
+		certPool.AddCert(cert)
+	}
+	tlsConfig.RootCAs = certPool
+
+	authClient, err = authclient.NewClient(client.Config{
+		Addrs: getHostAddresses(params),
+		Credentials: []client.Credentials{
+			client.LoadTLS(tlsConfig),
+		},
+		CircuitBreakerConfig: params.CircuitBreakerConfig,
+	})
+	if err != nil {
+		return nil, trace.Wrap(err)
+	}
+
+	return authClient, nil
+}
+
+func caPathRegisterClient(params RegisterParams) (*authclient.Client, error) {
+	tlsConfig := utils.TLSConfig(params.CipherSuites)
+	tlsConfig.Time = params.Clock.Now
+
+	cert, err := readCA(params.CAPath)
+	if err != nil && !trace.IsNotFound(err) {
+		return nil, trace.Wrap(err)
+	}
+
+	// If we're unable to read the file at CAPath, we fall back to insecure
+	// registration. This preserves the existing behavior. At a later date,
+	// we may wish to consider changing this to return an error - but this is a
+	// breaking change.
+	if trace.IsNotFound(err) {
+		log.Warnf("Falling back to insecurely joining because a missing or empty CA Path was provided.")
+		return insecureRegisterClient(params)
+	}
+
+	certPool := x509.NewCertPool()
+	certPool.AddCert(cert)
+	tlsConfig.RootCAs = certPool
+
+	log.Infof("Joining remote cluster %v, validating connection with certificate on disk.", cert.Subject.CommonName)
+
+	client, err := authclient.NewClient(client.Config{
+		Addrs: getHostAddresses(params),
+		Credentials: []client.Credentials{
+			client.LoadTLS(tlsConfig),
+		},
+		CircuitBreakerConfig: params.CircuitBreakerConfig,
+	})
+	if err != nil {
+		return nil, trace.Wrap(err)
+	}
+
+	return client, nil
+}
+
+type joinServiceClient interface {
+	RegisterUsingIAMMethod(ctx context.Context, challengeResponse client.RegisterIAMChallengeResponseFunc) (*proto.Certs, error)
+	RegisterUsingAzureMethod(ctx context.Context, challengeResponse client.RegisterAzureChallengeResponseFunc) (*proto.Certs, error)
+	RegisterUsingTPMMethod(
+		ctx context.Context,
+		initReq *proto.RegisterUsingTPMMethodInitialRequest,
+		solveChallenge client.RegisterTPMChallengeResponseFunc,
+	) (*proto.Certs, error)
+}
+
+func registerUsingTokenRequestForParams(token string, params RegisterParams) *types.RegisterUsingTokenRequest {
+	return &types.RegisterUsingTokenRequest{
+		Token:                token,
+		HostID:               params.ID.HostUUID,
+		NodeName:             params.ID.NodeName,
+		Role:                 params.ID.Role,
+		AdditionalPrincipals: params.AdditionalPrincipals,
+		DNSNames:             params.DNSNames,
+		PublicTLSKey:         params.PublicTLSKey,
+		PublicSSHKey:         params.PublicSSHKey,
+		Expires:              params.Expires,
+	}
+}
+
+// registerUsingIAMMethod is used to register using the IAM join method. It is
+// able to register through a proxy or through the auth server directly.
+func registerUsingIAMMethod(
+	ctx context.Context, joinServiceClient joinServiceClient, token string, params RegisterParams,
+) (*proto.Certs, error) {
+	log.Infof("Attempting to register %s with IAM method using regional STS endpoint", params.ID.Role)
+	// Call RegisterUsingIAMMethod and pass a callback to respond to the challenge with a signed join request.
+	certs, err := joinServiceClient.RegisterUsingIAMMethod(ctx, func(challenge string) (*proto.RegisterUsingIAMMethodRequest, error) {
+		// create the signed sts:GetCallerIdentity request and include the challenge
+		signedRequest, err := iam.CreateSignedSTSIdentityRequest(ctx, challenge,
+			iam.WithFIPSEndpoint(params.FIPS),
+			iam.WithRegionalEndpoint(true),
+		)
+		if err != nil {
+			return nil, trace.Wrap(err)
+		}
+
+		// send the register request including the challenge response
+		return &proto.RegisterUsingIAMMethodRequest{
+			RegisterUsingTokenRequest: registerUsingTokenRequestForParams(token, params),
+			StsIdentityRequest:        signedRequest,
+		}, nil
+	})
+	if err != nil {
+		log.WithError(err).Infof("Failed to register %s using regional STS endpoint", params.ID.Role)
+		return nil, trace.Wrap(err)
+	}
+
+	log.Infof("Successfully registered %s with IAM method using regional STS endpoint", params.ID.Role)
+	return certs, nil
+}
+
+// registerUsingAzureMethod is used to register using the Azure join method. It
+// is able to register through a proxy or through the auth server directly.
+func registerUsingAzureMethod(
+	ctx context.Context, client joinServiceClient, token string, params RegisterParams,
+) (*proto.Certs, error) {
+	certs, err := client.RegisterUsingAzureMethod(ctx, func(challenge string) (*proto.RegisterUsingAzureMethodRequest, error) {
+		imds := azure.NewInstanceMetadataClient()
+		if !imds.IsAvailable(ctx) {
+			return nil, trace.AccessDenied("could not reach instance metadata. Is Teleport running on an Azure VM?")
+		}
+		ad, err := imds.GetAttestedData(ctx, challenge)
+		if err != nil {
+			return nil, trace.Wrap(err)
+		}
+		accessToken, err := imds.GetAccessToken(ctx, params.AzureParams.ClientID)
+		if err != nil {
+			return nil, trace.Wrap(err)
+		}
+
+		return &proto.RegisterUsingAzureMethodRequest{
+			RegisterUsingTokenRequest: registerUsingTokenRequestForParams(token, params),
+			AttestedData:              ad,
+			AccessToken:               accessToken,
+		}, nil
+	})
+	return certs, trace.Wrap(err)
+}
+
+// registerUsingTPMMethod is used to register using the TPM join method. It
+// is able to register through a proxy or through the auth server directly.
+func registerUsingTPMMethod(
+	ctx context.Context,
+	client joinServiceClient,
+	token string,
+	params RegisterParams,
+) (*proto.Certs, error) {
+	log := slog.Default()
+
+	initReq := &proto.RegisterUsingTPMMethodInitialRequest{
+		JoinRequest: registerUsingTokenRequestForParams(token, params),
+	}
+
+	attestation, close, err := tpm.Attest(ctx, log)
+	if err != nil {
+		return nil, trace.Wrap(err)
+	}
+	defer func() {
+		if err := close(); err != nil {
+			log.WarnContext(ctx, "Failed to close TPM", "error", err)
+		}
+	}()
+
+	initReq.AttestationParams = tpm.AttestationParametersToProto(
+		attestation.AttestParams,
+	)
+	// Get the EKKey or EKCert. We want to prefer the EKCert if it is available
+	// as this is signed by the manufacturer.
+	switch {
+	case attestation.Data.EKCert != nil:
+		log.DebugContext(
+			ctx,
+			"Using EKCert for TPM registration",
+			"ekcert_serial", attestation.Data.EKCert.SerialNumber,
+		)
+		initReq.Ek = &proto.RegisterUsingTPMMethodInitialRequest_EkCert{
+			EkCert: attestation.Data.EKCert.Raw,
+		}
+	case attestation.Data.EKPub != nil:
+		log.DebugContext(
+			ctx,
+			"Using EKKey for TPM registration",
+			"ekpub_hash", attestation.Data.EKPubHash,
+		)
+		initReq.Ek = &proto.RegisterUsingTPMMethodInitialRequest_EkKey{
+			EkKey: attestation.Data.EKPub,
+		}
+	default:
+		return nil, trace.BadParameter("tpm has neither ekkey or ekcert")
+	}
+
+	// Submit initial request to the Auth Server.
+	certs, err := client.RegisterUsingTPMMethod(
+		ctx,
+		initReq,
+		func(
+			challenge *proto.TPMEncryptedCredential,
+		) (*proto.RegisterUsingTPMMethodChallengeResponse, error) {
+			// Solve the encrypted credential with our AK to prove possession
+			// and obtain the solution we need to complete the ceremony.
+			solution, err := attestation.Solve(tpm.EncryptedCredentialFromProto(
+				challenge,
+			))
+			if err != nil {
+				return nil, trace.Wrap(err, "activating credential")
+			}
+			return &proto.RegisterUsingTPMMethodChallengeResponse{
+				Solution: solution,
+			}, nil
+		},
+	)
+	return certs, trace.Wrap(err)
+}
+
+// readCA will read in CA that will be used to validate the certificate that
+// the Auth Server presents.
+func readCA(path string) (*x509.Certificate, error) {
+	certBytes, err := utils.ReadPath(path)
+	if err != nil {
+		return nil, trace.Wrap(err)
+	}
+	cert, err := tlsca.ParseCertificatePEM(certBytes)
+	if err != nil {
+		return nil, trace.Wrap(err, "failed to parse certificate at %v", path)
+	}
+	return cert, nil
+}
diff --git a/lib/auth/join/join_test.go b/lib/auth/join/join_test.go
new file mode 100644
index 0000000000000..7e32eb55438c2
--- /dev/null
+++ b/lib/auth/join/join_test.go
@@ -0,0 +1,328 @@
+// Teleport
+// Copyright (C) 2024 Gravitational, Inc.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package join
+
+import (
+	"context"
+	"crypto/tls"
+	"errors"
+	"net"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/gravitational/trace"
+	"github.com/jonboulle/clockwork"
+	"github.com/stretchr/testify/require"
+	"golang.org/x/crypto/ssh"
+
+	headerv1 "github.com/gravitational/teleport/api/gen/proto/go/teleport/header/v1"
+	machineidv1pb "github.com/gravitational/teleport/api/gen/proto/go/teleport/machineid/v1"
+	"github.com/gravitational/teleport/api/types"
+	apievents "github.com/gravitational/teleport/api/types/events"
+	"github.com/gravitational/teleport/lib/auth"
+	"github.com/gravitational/teleport/lib/auth/machineid/machineidv1"
+	"github.com/gravitational/teleport/lib/auth/state"
+	"github.com/gravitational/teleport/lib/auth/testauthority"
+	"github.com/gravitational/teleport/lib/defaults"
+	"github.com/gravitational/teleport/lib/events"
+	"github.com/gravitational/teleport/lib/fixtures"
+	"github.com/gravitational/teleport/lib/modules"
+	"github.com/gravitational/teleport/lib/tlsca"
+	"github.com/gravitational/teleport/lib/utils"
+)
+
+func TestMain(m *testing.M) {
+	modules.SetInsecureTestMode(true)
+	os.Exit(m.Run())
+}
+
+func newTestTLSServer(t testing.TB) *auth.TestTLSServer {
+	as, err := auth.NewTestAuthServer(auth.TestAuthServerConfig{
+		Dir:   t.TempDir(),
+		Clock: clockwork.NewFakeClockAt(time.Now().Round(time.Second).UTC()),
+	})
+	require.NoError(t, err)
+
+	srv, err := as.NewTestTLSServer()
+	require.NoError(t, err)
+
+	t.Cleanup(func() {
+		err := srv.Close()
+		if errors.Is(err, net.ErrClosed) {
+			return
+		}
+		require.NoError(t, err)
+	})
+
+	return srv
+}
+
+// TestRegister_Bot tests that a provision token can be used to generate
+// renewable certificates for a non-interactive user.
+func TestRegister_Bot(t *testing.T) {
+	t.Parallel()
+	ctx := context.Background()
+
+	srv := newTestTLSServer(t)
+
+	bot, err := machineidv1.UpsertBot(ctx, srv.Auth(), &machineidv1pb.Bot{
+		Metadata: &headerv1.Metadata{
+			Name: "test",
+		},
+		Spec: &machineidv1pb.BotSpec{
+			Roles: []string{},
+		},
+	}, srv.Clock().Now(), "")
+	require.NoError(t, err)
+
+	later := srv.Clock().Now().Add(4 * time.Hour)
+
+	goodToken := newBotToken(t, "good-token", bot.Metadata.Name, types.RoleBot, later)
+	expiredToken := newBotToken(t, "expired", bot.Metadata.Name, types.RoleBot, srv.Clock().Now().Add(-1*time.Hour))
+	wrongKind := newBotToken(t, "wrong-kind", "", types.RoleNode, later)
+	wrongUser := newBotToken(t, "wrong-user", "llama", types.RoleBot, later)
+	invalidToken := newBotToken(t, "this-token-does-not-exist", bot.Metadata.Name, types.RoleBot, later)
+
+	err = srv.Auth().UpsertToken(ctx, goodToken)
+	require.NoError(t, err)
+	err = srv.Auth().UpsertToken(ctx, expiredToken)
+	require.NoError(t, err)
+	err = srv.Auth().UpsertToken(ctx, wrongKind)
+	require.NoError(t, err)
+	err = srv.Auth().UpsertToken(ctx, wrongUser)
+	require.NoError(t, err)
+
+	privateKey, publicKey, err := testauthority.New().GenerateKeyPair()
+	require.NoError(t, err)
+	sshPrivateKey, err := ssh.ParseRawPrivateKey(privateKey)
+	require.NoError(t, err)
+	tlsPublicKey, err := tlsca.MarshalPublicKeyFromPrivateKeyPEM(sshPrivateKey)
+	require.NoError(t, err)
+
+	for _, test := range []struct {
+		desc      string
+		token     types.ProvisionToken
+		assertErr require.ErrorAssertionFunc
+	}{
+		{
+			desc:      "OK good token",
+			token:     goodToken,
+			assertErr: require.NoError,
+		},
+		{
+			desc:      "NOK expired token",
+			token:     expiredToken,
+			assertErr: require.Error,
+		},
+		{
+			desc:      "NOK wrong token kind",
+			token:     wrongKind,
+			assertErr: require.Error,
+		},
+		{
+			desc:      "NOK token for wrong user",
+			token:     wrongUser,
+			assertErr: require.Error,
+		},
+		{
+			desc:      "NOK invalid token",
+			token:     invalidToken,
+			assertErr: require.Error,
+		},
+	} {
+		t.Run(test.desc, func(t *testing.T) {
+			start := srv.Clock().Now()
+			certs, err := Register(ctx, RegisterParams{
+				Token: test.token.GetName(),
+				ID: state.IdentityID{
+					Role: types.RoleBot,
+				},
+				AuthServers:  []utils.NetAddr{*utils.MustParseAddr(srv.Addr().String())},
+				PublicTLSKey: tlsPublicKey,
+				PublicSSHKey: publicKey,
+			})
+			test.assertErr(t, err)
+
+			if err == nil {
+				require.NotEmpty(t, certs.SSH)
+				require.NotEmpty(t, certs.TLS)
+
+				// ensure token was removed
+				_, err = srv.Auth().GetToken(ctx, test.token.GetName())
+				require.True(t, trace.IsNotFound(err), "expected not found error, got %v", err)
+
+				// ensure cert is renewable
+				x509, err := tlsca.ParseCertificatePEM(certs.TLS)
+				require.NoError(t, err)
+				id, err := tlsca.FromSubject(x509.Subject, later)
+				require.NoError(t, err)
+				require.True(t, id.Renewable)
+
+				// Check audit event
+				evts, _, err := srv.Auth().SearchEvents(ctx, events.SearchEventsRequest{
+					From:       start,
+					To:         srv.Clock().Now(),
+					EventTypes: []string{events.BotJoinEvent},
+					Limit:      1,
+					Order:      types.EventOrderDescending,
+				})
+				require.NoError(t, err)
+				require.Len(t, evts, 1)
+				evt, ok := evts[0].(*apievents.BotJoin)
+				require.True(t, ok)
+				require.Equal(t, events.BotJoinEvent, evt.Type)
+				require.Equal(t, events.BotJoinCode, evt.Code)
+				require.EqualValues(t, types.JoinMethodToken, evt.Method)
+			}
+		})
+	}
+}
+
+// TestRegister_Bot_Expiry checks that bot certificate expiry can be set, and
+// does not exceed the limit.
+func TestRegister_Bot_Expiry(t *testing.T) {
+	t.Parallel()
+	ctx := context.Background()
+
+	srv := newTestTLSServer(t)
+	privateKey, publicKey, err := testauthority.New().GenerateKeyPair()
+	require.NoError(t, err)
+	sshPrivateKey, err := ssh.ParseRawPrivateKey(privateKey)
+	require.NoError(t, err)
+	tlsPublicKey, err := tlsca.MarshalPublicKeyFromPrivateKeyPEM(sshPrivateKey)
+	require.NoError(t, err)
+
+	validExpires := srv.Clock().Now().Add(time.Hour * 6)
+	tooGreatExpires := srv.Clock().Now().Add(time.Hour * 24 * 365)
+	tests := []struct {
+		name           string
+		requestExpires *time.Time
+		expectTTL      time.Duration
+	}{
+		{
+			name:           "unspecified defaults",
+			requestExpires: nil,
+			expectTTL:      defaults.DefaultRenewableCertTTL,
+		},
+		{
+			name:           "valid value specified",
+			requestExpires: &validExpires,
+			expectTTL:      time.Hour * 6,
+		},
+		{
+			name:           "value exceeding limit specified",
+			requestExpires: &tooGreatExpires,
+			// MaxSessionTTL set in createBotRole is 12 hours, so this cap will
+			// apply instead of the defaults.MaxRenewableCertTTL specified
+			// in generateInitialBotCerts.
+			expectTTL: 12 * time.Hour,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			botName := t.Name()
+			_, err = machineidv1.UpsertBot(ctx, srv.Auth(), &machineidv1pb.Bot{
+				Metadata: &headerv1.Metadata{
+					Name: botName,
+				},
+				Spec: &machineidv1pb.BotSpec{
+					Roles:  []string{},
+					Traits: []*machineidv1pb.Trait{},
+				},
+			}, srv.Clock().Now(), "")
+			require.NoError(t, err)
+			tok := newBotToken(t, t.Name(), botName, types.RoleBot, srv.Clock().Now().Add(time.Hour))
+			require.NoError(t, srv.Auth().UpsertToken(ctx, tok))
+
+			certs, err := Register(ctx, RegisterParams{
+				Token: tok.GetName(),
+				ID: state.IdentityID{
+					Role: types.RoleBot,
+				},
+				AuthServers:  []utils.NetAddr{*utils.MustParseAddr(srv.Addr().String())},
+				PublicTLSKey: tlsPublicKey,
+				PublicSSHKey: publicKey,
+				Expires:      tt.requestExpires,
+			})
+			require.NoError(t, err)
+			x509, err := tlsca.ParseCertificatePEM(certs.TLS)
+			require.NoError(t, err)
+			id, err := tlsca.FromSubject(x509.Subject, x509.NotAfter)
+			require.NoError(t, err)
+
+			ttl := id.Expires.Sub(srv.Clock().Now())
+			require.Equal(t, tt.expectTTL, ttl)
+		})
+	}
+}
+
+func newBotToken(t *testing.T, tokenName, botName string, role types.SystemRole, expiry time.Time) types.ProvisionToken {
+	t.Helper()
+	token, err := types.NewProvisionTokenFromSpec(tokenName, expiry, types.ProvisionTokenSpecV2{
+		Roles:   []types.SystemRole{role},
+		BotName: botName,
+	})
+	require.NoError(t, err, "could not create bot token")
+	return token
+}
+
+func TestVerifyALPNUpgradedConn(t *testing.T) {
+	t.Parallel()
+
+	srv := newTestTLSServer(t)
+	proxy, err := auth.NewServerIdentity(srv.Auth(), "test-proxy", types.RoleProxy)
+	require.NoError(t, err)
+
+	tests := []struct {
+		name       string
+		serverCert []byte
+		clock      clockwork.Clock
+		checkError require.ErrorAssertionFunc
+	}{
+		{
+			name:       "proxy verified",
+			serverCert: proxy.TLSCertBytes,
+			clock:      srv.Clock(),
+			checkError: require.NoError,
+		},
+		{
+			name:       "proxy expired",
+			serverCert: proxy.TLSCertBytes,
+			clock:      clockwork.NewFakeClockAt(srv.Clock().Now().Add(defaults.CATTL + time.Hour)),
+			checkError: require.Error,
+		},
+		{
+			name:       "not proxy",
+			serverCert: []byte(fixtures.TLSCACertPEM),
+			clock:      srv.Clock(),
+			checkError: require.Error,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			serverCert, err := utils.ReadCertificates(test.serverCert)
+			require.NoError(t, err)
+
+			test.checkError(t, verifyALPNUpgradedConn(test.clock)(tls.ConnectionState{
+				PeerCertificates: serverCert,
+			}))
+		})
+	}
+}
diff --git a/lib/auth/join_iam.go b/lib/auth/join_iam.go
index b52a8b6b35b81..6668a3449b8b5 100644
--- a/lib/auth/join_iam.go
+++ b/lib/auth/join_iam.go
@@ -27,12 +27,7 @@ import (
 	"net/http"
 	"net/url"
 	"slices"
-	"strings"
 
-	awssdk "github.com/aws/aws-sdk-go/aws"
-	"github.com/aws/aws-sdk-go/aws/endpoints"
-	"github.com/aws/aws-sdk-go/aws/session"
-	"github.com/aws/aws-sdk-go/service/sts"
 	"github.com/coreos/go-semver/semver"
 	"github.com/gravitational/trace"
 
@@ -40,7 +35,7 @@ import (
 	"github.com/gravitational/teleport/api/client"
 	"github.com/gravitational/teleport/api/client/proto"
 	"github.com/gravitational/teleport/api/types"
-	cloudaws "github.com/gravitational/teleport/lib/cloud/imds/aws"
+	"github.com/gravitational/teleport/lib/auth/join/iam"
 	"github.com/gravitational/teleport/lib/utils"
 	"github.com/gravitational/teleport/lib/utils/aws"
 )
@@ -71,7 +66,7 @@ const (
 // against a static list of known valid endpoints. We will need to update this
 // list as AWS adds new regions.
 func validateSTSHost(stsHost string, cfg *iamRegisterConfig) error {
-	valid := slices.Contains(validSTSEndpoints, stsHost)
+	valid := slices.Contains(iam.ValidSTSEndpoints(), stsHost)
 	if !valid {
 		return trace.AccessDenied("IAM join request uses unknown STS host %q. "+
 			"This could mean that the Teleport Node attempting to join the cluster is "+
@@ -81,10 +76,10 @@ func validateSTSHost(stsHost string, cfg *iamRegisterConfig) error {
 			"Following is the list of valid STS endpoints known to this auth server. "+
 			"If a legitimate STS endpoint is not included, please file an issue at "+
 			"https://github.com/gravitational/teleport. %v",
-			stsHost, validSTSEndpoints)
+			stsHost, iam.ValidSTSEndpoints())
 	}
 
-	if cfg.fips && !slices.Contains(fipsSTSEndpoints, stsHost) {
+	if cfg.fips && !slices.Contains(iam.FIPSSTSEndpoints(), stsHost) {
 		return trace.AccessDenied("node selected non-FIPS STS endpoint (%s) for the IAM join method", stsHost)
 	}
 
@@ -393,124 +388,3 @@ func (a *Server) RegisterUsingIAMMethod(
 	certs, err = a.generateCerts(ctx, provisionToken, req.RegisterUsingTokenRequest, nil)
 	return certs, trace.Wrap(err)
 }
-
-type stsIdentityRequestConfig struct {
-	regionalEndpointOption endpoints.STSRegionalEndpoint
-	fipsEndpointOption     endpoints.FIPSEndpointState
-}
-
-type stsIdentityRequestOption func(cfg *stsIdentityRequestConfig)
-
-func withRegionalEndpoint(useRegionalEndpoint bool) stsIdentityRequestOption {
-	return func(cfg *stsIdentityRequestConfig) {
-		if useRegionalEndpoint {
-			cfg.regionalEndpointOption = endpoints.RegionalSTSEndpoint
-		} else {
-			cfg.regionalEndpointOption = endpoints.LegacySTSEndpoint
-		}
-	}
-}
-
-func withFIPSEndpoint(useFIPS bool) stsIdentityRequestOption {
-	return func(cfg *stsIdentityRequestConfig) {
-		if useFIPS {
-			cfg.fipsEndpointOption = endpoints.FIPSEndpointStateEnabled
-		} else {
-			cfg.fipsEndpointOption = endpoints.FIPSEndpointStateDisabled
-		}
-	}
-}
-
-// createSignedSTSIdentityRequest is called on the client side and returns an
-// sts:GetCallerIdentity request signed with the local AWS credentials
-func createSignedSTSIdentityRequest(ctx context.Context, challenge string, opts ...stsIdentityRequestOption) ([]byte, error) {
-	cfg := &stsIdentityRequestConfig{}
-	for _, opt := range opts {
-		opt(cfg)
-	}
-
-	stsClient, err := newSTSClient(ctx, cfg)
-	if err != nil {
-		return nil, trace.Wrap(err)
-	}
-
-	req, _ := stsClient.GetCallerIdentityRequest(&sts.GetCallerIdentityInput{})
-	// set challenge header
-	req.HTTPRequest.Header.Set(challengeHeaderKey, challenge)
-	// request json for simpler parsing
-	req.HTTPRequest.Header.Set("Accept", "application/json")
-	// sign the request, including headers
-	if err := req.Sign(); err != nil {
-		return nil, trace.Wrap(err)
-	}
-	// write the signed HTTP request to a buffer
-	var signedRequest bytes.Buffer
-	if err := req.HTTPRequest.Write(&signedRequest); err != nil {
-		return nil, trace.Wrap(err)
-	}
-	return signedRequest.Bytes(), nil
-}
-
-func newSTSClient(ctx context.Context, cfg *stsIdentityRequestConfig) (*sts.STS, error) {
-	awsConfig := awssdk.Config{
-		UseFIPSEndpoint:     cfg.fipsEndpointOption,
-		STSRegionalEndpoint: cfg.regionalEndpointOption,
-	}
-	sess, err := session.NewSessionWithOptions(session.Options{
-		SharedConfigState: session.SharedConfigEnable,
-		Config:            awsConfig,
-	})
-	if err != nil {
-		return nil, trace.Wrap(err)
-	}
-
-	stsClient := sts.New(sess)
-
-	if slices.Contains(globalSTSEndpoints, strings.TrimPrefix(stsClient.Endpoint, "https://")) {
-		// If the caller wants to use the regional endpoint but it was not resolved
-		// from the environment, attempt to find the region from the EC2 IMDS
-		if cfg.regionalEndpointOption == endpoints.RegionalSTSEndpoint {
-			region, err := getEC2LocalRegion(ctx)
-			if err != nil {
-				return nil, trace.Wrap(err, "failed to resolve local AWS region from environment or IMDS")
-			}
-			stsClient = sts.New(sess, awssdk.NewConfig().WithRegion(region))
-		} else {
-			log.Info("Attempting to use the global STS endpoint for the IAM join method. " +
-				"This will probably fail in non-default AWS partitions such as China or GovCloud, or if FIPS mode is enabled. " +
-				"Consider setting the AWS_REGION environment variable, setting the region in ~/.aws/config, or enabling the IMDSv2.")
-		}
-	}
-
-	if cfg.fipsEndpointOption == endpoints.FIPSEndpointStateEnabled &&
-		!slices.Contains(validSTSEndpoints, strings.TrimPrefix(stsClient.Endpoint, "https://")) {
-		// The AWS SDK will generate invalid endpoints when attempting to
-		// resolve the FIPS endpoint for a region that does not have one.
-		// In this case, try to use the FIPS endpoint in us-east-1. This should
-		// work for all regions in the standard partition. In GovCloud, we should
-		// not hit this because all regional endpoints support FIPS. In China or
-		// other partitions, this will fail, and FIPS mode will not be supported.
-		log.Infof("AWS SDK resolved FIPS STS endpoint %s, which does not appear to be valid. "+
-			"Attempting to use the FIPS STS endpoint for us-east-1.",
-			stsClient.Endpoint)
-		stsClient = sts.New(sess, awssdk.NewConfig().WithRegion("us-east-1"))
-	}
-
-	return stsClient, nil
-}
-
-// getEC2LocalRegion returns the AWS region this EC2 instance is running in, or
-// a NotFound error if the EC2 IMDS is unavailable.
-func getEC2LocalRegion(ctx context.Context) (string, error) {
-	imdsClient, err := cloudaws.NewInstanceMetadataClient(ctx)
-	if err != nil {
-		return "", trace.Wrap(err)
-	}
-
-	if !imdsClient.IsAvailable(ctx) {
-		return "", trace.NotFound("IMDS is unavailable")
-	}
-
-	region, err := imdsClient.GetRegion(ctx)
-	return region, trace.Wrap(err)
-}
diff --git a/lib/auth/join_test.go b/lib/auth/join_test.go
index 9e207f9667a3f..6ce94edcc0ab6 100644
--- a/lib/auth/join_test.go
+++ b/lib/auth/join_test.go
@@ -34,6 +34,7 @@ import (
 	"github.com/gravitational/teleport/api/types"
 	apievents "github.com/gravitational/teleport/api/types/events"
 	"github.com/gravitational/teleport/api/utils/sshutils"
+	"github.com/gravitational/teleport/lib/auth/join"
 	"github.com/gravitational/teleport/lib/auth/machineid/machineidv1"
 	"github.com/gravitational/teleport/lib/auth/state"
 	"github.com/gravitational/teleport/lib/auth/testauthority"
@@ -371,7 +372,7 @@ func TestRegister_Bot(t *testing.T) {
 	} {
 		t.Run(test.desc, func(t *testing.T) {
 			start := srv.Clock().Now()
-			certs, err := Register(ctx, RegisterParams{
+			certs, err := join.Register(ctx, join.RegisterParams{
 				Token: test.token.GetName(),
 				ID: state.IdentityID{
 					Role: types.RoleBot,
@@ -474,7 +475,7 @@ func TestRegister_Bot_Expiry(t *testing.T) {
 			tok := newBotToken(t, t.Name(), botName, types.RoleBot, srv.Clock().Now().Add(time.Hour))
 			require.NoError(t, srv.Auth().UpsertToken(ctx, tok))
 
-			certs, err := Register(ctx, RegisterParams{
+			certs, err := join.Register(ctx, join.RegisterParams{
 				Token: tok.GetName(),
 				ID: state.IdentityID{
 					Role: types.RoleBot,
diff --git a/lib/auth/register.go b/lib/auth/register.go
index 24e48594d6bc4..b425bdf8c3ff2 100644
--- a/lib/auth/register.go
+++ b/lib/auth/register.go
@@ -20,44 +20,15 @@ package auth
 
 import (
 	"context"
-	"crypto/tls"
-	"crypto/x509"
-	"log/slog"
-	"os"
-	"slices"
-	"time"
 
 	"github.com/gravitational/trace"
-	"github.com/jonboulle/clockwork"
-	"golang.org/x/net/http2"
-	"google.golang.org/grpc"
-	"google.golang.org/grpc/credentials"
 
-	"github.com/gravitational/teleport"
-	"github.com/gravitational/teleport/api/breaker"
-	"github.com/gravitational/teleport/api/client"
 	"github.com/gravitational/teleport/api/client/proto"
-	"github.com/gravitational/teleport/api/constants"
-	apidefaults "github.com/gravitational/teleport/api/defaults"
-	"github.com/gravitational/teleport/api/metadata"
-	"github.com/gravitational/teleport/api/observability/tracing"
 	"github.com/gravitational/teleport/api/types"
-	"github.com/gravitational/teleport/api/utils/aws"
 	"github.com/gravitational/teleport/lib/auth/authclient"
 	"github.com/gravitational/teleport/lib/auth/native"
 	"github.com/gravitational/teleport/lib/auth/state"
-	"github.com/gravitational/teleport/lib/circleci"
-	"github.com/gravitational/teleport/lib/cloud/imds/azure"
-	"github.com/gravitational/teleport/lib/cloud/imds/gcp"
 	"github.com/gravitational/teleport/lib/defaults"
-	"github.com/gravitational/teleport/lib/githubactions"
-	"github.com/gravitational/teleport/lib/gitlab"
-	"github.com/gravitational/teleport/lib/kubernetestoken"
-	"github.com/gravitational/teleport/lib/spacelift"
-	"github.com/gravitational/teleport/lib/srv/alpnproxy/common"
-	"github.com/gravitational/teleport/lib/tlsca"
-	"github.com/gravitational/teleport/lib/tpm"
-	"github.com/gravitational/teleport/lib/utils"
 )
 
 // LocalRegister is used to generate host keys when a node or proxy is running
@@ -104,739 +75,6 @@ func LocalRegister(id state.IdentityID, authServer *Server, additionalPrincipals
 	return identity, nil
 }
 
-// AzureParams is the parameters specific to the azure join method.
-type AzureParams struct {
-	// ClientID is the client ID of the managed identity for Teleport to assume
-	// when authenticating a node.
-	ClientID string
-}
-
-// RegisterParams specifies parameters
-// for first time register operation with auth server
-type RegisterParams struct {
-	// Token is a secure token to join the cluster
-	Token string
-	// ID is identity ID
-	ID state.IdentityID
-	// AuthServers is a list of auth servers to dial
-	AuthServers []utils.NetAddr
-	// ProxyServer is a proxy server to dial
-	ProxyServer utils.NetAddr
-	// AdditionalPrincipals is a list of additional principals to dial
-	AdditionalPrincipals []string
-	// DNSNames is a list of DNS names to add to x509 certificate
-	DNSNames []string
-	// PublicTLSKey is a server's public key to sign
-	PublicTLSKey []byte
-	// PublicSSHKey is a server's public SSH key to sign
-	PublicSSHKey []byte
-	// CipherSuites is a list of cipher suites to use for TLS client connection
-	CipherSuites []uint16
-	// CAPins are the SKPI hashes of the CAs used to verify the Auth Server.
-	CAPins []string
-	// CAPath is the path to the CA file.
-	CAPath string
-	// GetHostCredentials is a client that can fetch host credentials.
-	GetHostCredentials HostCredentials
-	// Clock specifies the time provider. Will be used to override the time anchor
-	// for TLS certificate verification.
-	// Defaults to real clock if unspecified
-	Clock clockwork.Clock
-	// JoinMethod is the joining method used for this register request.
-	JoinMethod types.JoinMethod
-	// ec2IdentityDocument is used for Simplified Node Joining to prove the
-	// identity of a joining EC2 instance.
-	ec2IdentityDocument []byte
-	// AzureParams is the parameters specific to the azure join method.
-	AzureParams AzureParams
-	// CircuitBreakerConfig defines how the circuit breaker should behave.
-	CircuitBreakerConfig breaker.Config
-	// FIPS means FedRAMP/FIPS 140-2 compliant configuration was requested.
-	FIPS bool
-	// IDToken is a token retrieved from a workload identity provider for
-	// certain join types e.g GitHub, Google.
-	IDToken string
-	// Expires is an optional field for bots that specifies a time that the
-	// certificates that are returned by registering should expire at.
-	// It should not be specified for non-bot registrations.
-	Expires *time.Time
-	// Insecure trusts the certificates from the Auth Server or Proxy during registration without verification.
-	Insecure bool
-}
-
-func (r *RegisterParams) checkAndSetDefaults() error {
-	if r.Clock == nil {
-		r.Clock = clockwork.NewRealClock()
-	}
-
-	if err := r.verifyAuthOrProxyAddress(); err != nil {
-		return trace.BadParameter("no auth or proxy servers set")
-	}
-
-	return nil
-}
-
-func (r *RegisterParams) verifyAuthOrProxyAddress() error {
-	haveAuthServers := len(r.AuthServers) > 0
-	haveProxyServer := !r.ProxyServer.IsEmpty()
-
-	if !haveAuthServers && !haveProxyServer {
-		return trace.BadParameter("no auth or proxy servers set")
-	}
-
-	if haveAuthServers && haveProxyServer {
-		return trace.BadParameter("only one of auth or proxy server should be set")
-	}
-
-	return nil
-}
-
-// CredGetter is an interface for a client that can be used to get host
-// credentials. This interface is needed because lib/client can not be imported
-// in lib/auth due to circular imports.
-type HostCredentials func(context.Context, string, bool, types.RegisterUsingTokenRequest) (*proto.Certs, error)
-
-// Register is used to generate host keys when a node or proxy are running on
-// different hosts than the auth server. This method requires provisioning
-// tokens to prove a valid auth server was used to issue the joining request
-// as well as a method for the node to validate the auth server.
-func Register(ctx context.Context, params RegisterParams) (certs *proto.Certs, err error) {
-	ctx, span := tracer.Start(ctx, "Register")
-	defer func() { tracing.EndSpan(span, err) }()
-
-	if err := params.checkAndSetDefaults(); err != nil {
-		return nil, trace.Wrap(err)
-	}
-	// Read in the token. The token can either be passed in or come from a file
-	// on disk.
-	token, err := utils.TryReadValueAsFile(params.Token)
-	if err != nil {
-		return nil, trace.Wrap(err)
-	}
-
-	// add EC2 Identity Document to params if required for given join method
-	switch params.JoinMethod {
-	case types.JoinMethodEC2:
-		if !aws.IsEC2NodeID(params.ID.HostUUID) {
-			return nil, trace.BadParameter(
-				`Host ID %q is not valid when using the EC2 join method, `+
-					`try removing the "host_uuid" file in your teleport data dir `+
-					`(e.g. /var/lib/teleport/host_uuid)`,
-				params.ID.HostUUID)
-		}
-		params.ec2IdentityDocument, err = utils.GetRawEC2IdentityDocument(ctx)
-		if err != nil {
-			return nil, trace.Wrap(err)
-		}
-	case types.JoinMethodGitHub:
-		params.IDToken, err = githubactions.NewIDTokenSource().GetIDToken(ctx)
-		if err != nil {
-			return nil, trace.Wrap(err)
-		}
-	case types.JoinMethodGitLab:
-		params.IDToken, err = gitlab.NewIDTokenSource(os.Getenv).GetIDToken()
-		if err != nil {
-			return nil, trace.Wrap(err)
-		}
-	case types.JoinMethodCircleCI:
-		params.IDToken, err = circleci.GetIDToken(os.Getenv)
-		if err != nil {
-			return nil, trace.Wrap(err)
-		}
-	case types.JoinMethodKubernetes:
-		params.IDToken, err = kubernetestoken.GetIDToken(os.Getenv, os.ReadFile)
-		if err != nil {
-			return nil, trace.Wrap(err)
-		}
-	case types.JoinMethodGCP:
-		params.IDToken, err = gcp.GetIDToken(ctx)
-		if err != nil {
-			return nil, trace.Wrap(err)
-		}
-	case types.JoinMethodSpacelift:
-		params.IDToken, err = spacelift.NewIDTokenSource(os.Getenv).GetIDToken()
-		if err != nil {
-			return nil, trace.Wrap(err)
-		}
-	}
-
-	type registerMethod struct {
-		call func(ctx context.Context, token string, params RegisterParams) (*proto.Certs, error)
-		desc string
-	}
-
-	registerThroughAuth := registerMethod{registerThroughAuth, "with auth server"}
-	registerThroughProxy := registerMethod{registerThroughProxy, "via proxy server"}
-
-	registerMethods := []registerMethod{registerThroughAuth, registerThroughProxy}
-
-	if !params.ProxyServer.IsEmpty() {
-		log.WithField("proxy-server", params.ProxyServer).Debugf("Registering node to the cluster.")
-
-		registerMethods = []registerMethod{registerThroughProxy}
-
-		if proxyServerIsAuth(params.ProxyServer) {
-			log.Debugf("The specified proxy server appears to be an auth server.")
-		}
-	} else {
-		log.WithField("auth-servers", params.AuthServers).Debugf("Registering node to the cluster.")
-
-		if params.GetHostCredentials == nil {
-			log.Debugf("Missing client, it is not possible to register through proxy.")
-			registerMethods = []registerMethod{registerThroughAuth}
-		} else if authServerIsProxy(params.AuthServers) {
-			log.Debugf("The first specified auth server appears to be a proxy.")
-			registerMethods = []registerMethod{registerThroughProxy, registerThroughAuth}
-		}
-	}
-
-	var collectedErrs []error
-	for _, method := range registerMethods {
-		log.Infof("Attempting registration %s.", method.desc)
-		certs, err := method.call(ctx, token, params)
-		if err != nil {
-			collectedErrs = append(collectedErrs, err)
-			log.WithError(err).Debugf("Registration %s failed.", method.desc)
-			continue
-		}
-		log.Infof("Successfully registered %s.", method.desc)
-		return certs, nil
-	}
-	return nil, trace.NewAggregate(collectedErrs...)
-}
-
-// authServerIsProxy returns true if the first specified auth server
-// to register with appears to be a proxy.
-func authServerIsProxy(servers []utils.NetAddr) bool {
-	if len(servers) == 0 {
-		return false
-	}
-	port := servers[0].Port(0)
-	return port == defaults.HTTPListenPort || port == teleport.StandardHTTPSPort
-}
-
-// proxyServerIsAuth returns true if the address given to register with
-// appears to be an auth server.
-func proxyServerIsAuth(server utils.NetAddr) bool {
-	port := server.Port(0)
-	return port == defaults.AuthListenPort
-}
-
-// registerThroughProxy is used to register through the proxy server.
-func registerThroughProxy(
-	ctx context.Context,
-	token string,
-	params RegisterParams,
-) (certs *proto.Certs, err error) {
-	ctx, span := tracer.Start(ctx, "registerThroughProxy")
-	defer func() { tracing.EndSpan(span, err) }()
-
-	switch params.JoinMethod {
-	case types.JoinMethodIAM, types.JoinMethodAzure, types.JoinMethodTPM:
-		// IAM and Azure join methods require gRPC client
-		conn, err := proxyJoinServiceConn(ctx, params, params.Insecure)
-		if err != nil {
-			return nil, trace.Wrap(err)
-		}
-		defer conn.Close()
-
-		joinServiceClient := client.NewJoinServiceClient(proto.NewJoinServiceClient(conn))
-		switch params.JoinMethod {
-		case types.JoinMethodIAM:
-			certs, err = registerUsingIAMMethod(ctx, joinServiceClient, token, params)
-		case types.JoinMethodAzure:
-			certs, err = registerUsingAzureMethod(ctx, joinServiceClient, token, params)
-		case types.JoinMethodTPM:
-			certs, err = registerUsingTPMMethod(ctx, joinServiceClient, token, params)
-		default:
-			return nil, trace.BadParameter("unhandled join method %q", params.JoinMethod)
-		}
-
-		if err != nil {
-			return nil, trace.Wrap(err)
-		}
-	default:
-		// The rest of the join methods use GetHostCredentials function passed through
-		// params to call proxy HTTP endpoint
-		var err error
-		certs, err = params.GetHostCredentials(ctx,
-			getHostAddresses(params)[0],
-			params.Insecure,
-			types.RegisterUsingTokenRequest{
-				Token:                token,
-				HostID:               params.ID.HostUUID,
-				NodeName:             params.ID.NodeName,
-				Role:                 params.ID.Role,
-				AdditionalPrincipals: params.AdditionalPrincipals,
-				DNSNames:             params.DNSNames,
-				PublicTLSKey:         params.PublicTLSKey,
-				PublicSSHKey:         params.PublicSSHKey,
-				EC2IdentityDocument:  params.ec2IdentityDocument,
-				IDToken:              params.IDToken,
-				Expires:              params.Expires,
-			})
-		if err != nil {
-			return nil, trace.Wrap(err)
-		}
-	}
-	return certs, nil
-}
-
-func getHostAddresses(params RegisterParams) []string {
-	if !params.ProxyServer.IsEmpty() {
-		return []string{params.ProxyServer.String()}
-	}
-
-	return utils.NetAddrsToStrings(params.AuthServers)
-}
-
-// registerThroughAuth is used to register through the auth server.
-func registerThroughAuth(
-	ctx context.Context, token string, params RegisterParams,
-) (certs *proto.Certs, err error) {
-	ctx, span := tracer.Start(ctx, "registerThroughAuth")
-	defer func() { tracing.EndSpan(span, err) }()
-
-	var client *authclient.Client
-	// Build a client for the Auth Server with different certificate validation
-	// depending on the configured values for Insecure, CAPins and CAPath.
-	switch {
-	case params.Insecure:
-		log.Warnf("Insecure mode enabled. Auth Server cert will not be validated and CAPins and CAPath value will be ignored.")
-		client, err = insecureRegisterClient(params)
-	case len(params.CAPins) != 0:
-		// CAPins takes precedence over CAPath
-		client, err = pinRegisterClient(ctx, params)
-	case params.CAPath != "":
-		client, err = caPathRegisterClient(params)
-	default:
-		// We fall back to insecure mode here - this is a little odd but is
-		// necessary to preserve the behavior of registration. At a later date,
-		// we may consider making this an error asking the user to provide
-		// Insecure, CAPins or CAPath.
-		client, err = insecureRegisterClient(params)
-	}
-	if err != nil {
-		return nil, trace.Wrap(err)
-	}
-	defer client.Close()
-
-	switch params.JoinMethod {
-	// IAM and Azure methods use unique gRPC endpoints
-	case types.JoinMethodIAM:
-		certs, err = registerUsingIAMMethod(ctx, client, token, params)
-	case types.JoinMethodAzure:
-		certs, err = registerUsingAzureMethod(ctx, client, token, params)
-	case types.JoinMethodTPM:
-		certs, err = registerUsingTPMMethod(ctx, client, token, params)
-	default:
-		// non-IAM join methods use HTTP endpoint
-		// Get the SSH and X509 certificates for a node.
-		certs, err = client.RegisterUsingToken(
-			ctx,
-			&types.RegisterUsingTokenRequest{
-				Token:                token,
-				HostID:               params.ID.HostUUID,
-				NodeName:             params.ID.NodeName,
-				Role:                 params.ID.Role,
-				AdditionalPrincipals: params.AdditionalPrincipals,
-				DNSNames:             params.DNSNames,
-				PublicTLSKey:         params.PublicTLSKey,
-				PublicSSHKey:         params.PublicSSHKey,
-				EC2IdentityDocument:  params.ec2IdentityDocument,
-				IDToken:              params.IDToken,
-				Expires:              params.Expires,
-			})
-	}
-	return certs, trace.Wrap(err)
-}
-
-// proxyJoinServiceConn attempts to connect to the join service running on the
-// proxy. The Proxy's TLS cert will be verified using the host's root CA pool
-// (PKI) unless the --insecure flag was passed.
-func proxyJoinServiceConn(
-	ctx context.Context, params RegisterParams, insecure bool,
-) (*grpc.ClientConn, error) {
-	tlsConfig := utils.TLSConfig(params.CipherSuites)
-	tlsConfig.Time = params.Clock.Now
-	// set NextProtos for TLS routing, the actual protocol will be h2
-	tlsConfig.NextProtos = []string{string(common.ProtocolProxyGRPCInsecure), http2.NextProtoTLS}
-
-	if insecure {
-		tlsConfig.InsecureSkipVerify = true
-		log.Warnf("Joining cluster without validating the identity of the Proxy Server.")
-	}
-
-	// Check if proxy is behind a load balancer. If so, the connection upgrade
-	// will verify the load balancer's cert using system cert pool. This
-	// provides the same level of security as the client only verifies Proxy's
-	// web cert against system cert pool when connection upgrade is not
-	// required.
-	//
-	// With the ALPN connection upgrade, the tunneled TLS Routing request will
-	// skip verify as the Proxy server will present its host cert which is not
-	// fully verifiable at this point since the client does not have the host
-	// CAs yet before completing registration.
-	alpnConnUpgrade := client.IsALPNConnUpgradeRequired(ctx, getHostAddresses(params)[0], insecure)
-	if alpnConnUpgrade && !insecure {
-		tlsConfig.InsecureSkipVerify = true
-		tlsConfig.VerifyConnection = verifyALPNUpgradedConn(params.Clock)
-	}
-
-	dialer := client.NewDialer(
-		ctx,
-		apidefaults.DefaultIdleTimeout,
-		apidefaults.DefaultIOTimeout,
-		client.WithInsecureSkipVerify(insecure),
-		client.WithALPNConnUpgrade(alpnConnUpgrade),
-	)
-
-	conn, err := grpc.Dial(
-		getHostAddresses(params)[0],
-		grpc.WithContextDialer(client.GRPCContextDialer(dialer)),
-		grpc.WithUnaryInterceptor(metadata.UnaryClientInterceptor),
-		grpc.WithStreamInterceptor(metadata.StreamClientInterceptor),
-		grpc.WithTransportCredentials(credentials.NewTLS(tlsConfig)),
-	)
-	return conn, trace.Wrap(err)
-}
-
-// verifyALPNUpgradedConn is a tls.Config.VerifyConnection callback function
-// used by the tunneled TLS Routing request to verify the host cert of a Proxy
-// behind a L7 load balancer.
-//
-// Since the client has not obtained the cluster CAs at this point, the
-// presented cert cannot be fully verified yet. For now, this function only
-// checks if "teleport.cluster.local" is present as one of the DNS names and
-// verifies the cert is not expired.
-func verifyALPNUpgradedConn(clock clockwork.Clock) func(tls.ConnectionState) error {
-	return func(server tls.ConnectionState) error {
-		for _, cert := range server.PeerCertificates {
-			if slices.Contains(cert.DNSNames, constants.APIDomain) && clock.Now().Before(cert.NotAfter) {
-				return nil
-			}
-		}
-		return trace.AccessDenied("server is not a Teleport proxy or server certificate is expired")
-	}
-}
-
-// insecureRegisterClient attempts to connects to the Auth Server using the
-// CA on disk. If no CA is found on disk, Teleport will not verify the Auth
-// Server it is connecting to.
-func insecureRegisterClient(params RegisterParams) (*authclient.Client, error) {
-	log.Warnf("Joining cluster without validating the identity of the Auth " +
-		"Server. This may open you up to a Man-In-The-Middle (MITM) attack if an " +
-		"attacker can gain privileged network access. To remedy this, use the CA pin " +
-		"value provided when join token was generated to validate the identity of " +
-		"the Auth Server or point to a valid Certificate via the CA Path option.")
-
-	tlsConfig := utils.TLSConfig(params.CipherSuites)
-	tlsConfig.Time = params.Clock.Now
-	tlsConfig.InsecureSkipVerify = true
-
-	client, err := authclient.NewClient(client.Config{
-		Addrs: getHostAddresses(params),
-		Credentials: []client.Credentials{
-			client.LoadTLS(tlsConfig),
-		},
-		CircuitBreakerConfig: params.CircuitBreakerConfig,
-	})
-	if err != nil {
-		return nil, trace.Wrap(err)
-	}
-
-	return client, nil
-}
-
-// readCA will read in CA that will be used to validate the certificate that
-// the Auth Server presents.
-func readCA(path string) (*x509.Certificate, error) {
-	certBytes, err := utils.ReadPath(path)
-	if err != nil {
-		return nil, trace.Wrap(err)
-	}
-	cert, err := tlsca.ParseCertificatePEM(certBytes)
-	if err != nil {
-		return nil, trace.Wrap(err, "failed to parse certificate at %v", path)
-	}
-	return cert, nil
-}
-
-// pinRegisterClient first connects to the Auth Server using a insecure
-// connection to fetch the root CA. If the root CA matches the provided CA
-// pin, a connection will be re-established and the root CA will be used to
-// validate the certificate presented. If both conditions hold true, then we
-// know we are connecting to the expected Auth Server.
-func pinRegisterClient(
-	ctx context.Context, params RegisterParams,
-) (*authclient.Client, error) {
-	// Build a insecure client to the Auth Server. This is safe because even if
-	// an attacker were to MITM this connection the CA pin will not match below.
-	tlsConfig := utils.TLSConfig(params.CipherSuites)
-	tlsConfig.InsecureSkipVerify = true
-	tlsConfig.Time = params.Clock.Now
-	authClient, err := authclient.NewClient(client.Config{
-		Addrs: getHostAddresses(params),
-		Credentials: []client.Credentials{
-			client.LoadTLS(tlsConfig),
-		},
-		CircuitBreakerConfig: params.CircuitBreakerConfig,
-	})
-	if err != nil {
-		return nil, trace.Wrap(err)
-	}
-	defer authClient.Close()
-
-	// Fetch the root CA from the Auth Server. The NOP role has access to the
-	// GetClusterCACert endpoint.
-	localCA, err := authClient.GetClusterCACert(ctx)
-	if err != nil {
-		return nil, trace.Wrap(err)
-	}
-	certs, err := tlsca.ParseCertificatePEMs(localCA.TLSCA)
-	if err != nil {
-		return nil, trace.Wrap(err)
-	}
-
-	// Check that the SPKI pin matches the CA we fetched over a insecure
-	// connection. This makes sure the CA fetched over a insecure connection is
-	// in-fact the expected CA.
-	err = utils.CheckSPKI(params.CAPins, certs)
-	if err != nil {
-		return nil, trace.Wrap(err)
-	}
-
-	for _, cert := range certs {
-		// Check that the fetched CA is valid at the current time.
-		err = utils.VerifyCertificateExpiry(cert, params.Clock)
-		if err != nil {
-			return nil, trace.Wrap(err)
-		}
-
-	}
-	log.Infof("Joining remote cluster %v with CA pin.", certs[0].Subject.CommonName)
-
-	// Create another client, but this time with the CA provided to validate
-	// that the Auth Server was issued a certificate by the same CA.
-	tlsConfig = utils.TLSConfig(params.CipherSuites)
-	tlsConfig.Time = params.Clock.Now
-	certPool := x509.NewCertPool()
-	for _, cert := range certs {
-		certPool.AddCert(cert)
-	}
-	tlsConfig.RootCAs = certPool
-
-	authClient, err = authclient.NewClient(client.Config{
-		Addrs: getHostAddresses(params),
-		Credentials: []client.Credentials{
-			client.LoadTLS(tlsConfig),
-		},
-		CircuitBreakerConfig: params.CircuitBreakerConfig,
-	})
-	if err != nil {
-		return nil, trace.Wrap(err)
-	}
-
-	return authClient, nil
-}
-
-func caPathRegisterClient(params RegisterParams) (*authclient.Client, error) {
-	tlsConfig := utils.TLSConfig(params.CipherSuites)
-	tlsConfig.Time = params.Clock.Now
-
-	cert, err := readCA(params.CAPath)
-	if err != nil && !trace.IsNotFound(err) {
-		return nil, trace.Wrap(err)
-	}
-
-	// If we're unable to read the file at CAPath, we fall back to insecure
-	// registration. This preserves the existing behavior. At a later date,
-	// we may wish to consider changing this to return an error - but this is a
-	// breaking change.
-	if trace.IsNotFound(err) {
-		log.Warnf("Falling back to insecurely joining because a missing or empty CA Path was provided.")
-		return insecureRegisterClient(params)
-	}
-
-	certPool := x509.NewCertPool()
-	certPool.AddCert(cert)
-	tlsConfig.RootCAs = certPool
-
-	log.Infof("Joining remote cluster %v, validating connection with certificate on disk.", cert.Subject.CommonName)
-
-	client, err := authclient.NewClient(client.Config{
-		Addrs: getHostAddresses(params),
-		Credentials: []client.Credentials{
-			client.LoadTLS(tlsConfig),
-		},
-		CircuitBreakerConfig: params.CircuitBreakerConfig,
-	})
-	if err != nil {
-		return nil, trace.Wrap(err)
-	}
-
-	return client, nil
-}
-
-type joinServiceClient interface {
-	RegisterUsingIAMMethod(ctx context.Context, challengeResponse client.RegisterIAMChallengeResponseFunc) (*proto.Certs, error)
-	RegisterUsingAzureMethod(ctx context.Context, challengeResponse client.RegisterAzureChallengeResponseFunc) (*proto.Certs, error)
-	RegisterUsingTPMMethod(
-		ctx context.Context,
-		initReq *proto.RegisterUsingTPMMethodInitialRequest,
-		solveChallenge client.RegisterTPMChallengeResponseFunc,
-	) (*proto.Certs, error)
-}
-
-func registerUsingTokenRequestForParams(token string, params RegisterParams) *types.RegisterUsingTokenRequest {
-	return &types.RegisterUsingTokenRequest{
-		Token:                token,
-		HostID:               params.ID.HostUUID,
-		NodeName:             params.ID.NodeName,
-		Role:                 params.ID.Role,
-		AdditionalPrincipals: params.AdditionalPrincipals,
-		DNSNames:             params.DNSNames,
-		PublicTLSKey:         params.PublicTLSKey,
-		PublicSSHKey:         params.PublicSSHKey,
-		Expires:              params.Expires,
-	}
-}
-
-// registerUsingIAMMethod is used to register using the IAM join method. It is
-// able to register through a proxy or through the auth server directly.
-func registerUsingIAMMethod(
-	ctx context.Context, joinServiceClient joinServiceClient, token string, params RegisterParams,
-) (*proto.Certs, error) {
-	log.Infof("Attempting to register %s with IAM method using regional STS endpoint", params.ID.Role)
-	// Call RegisterUsingIAMMethod and pass a callback to respond to the challenge with a signed join request.
-	certs, err := joinServiceClient.RegisterUsingIAMMethod(ctx, func(challenge string) (*proto.RegisterUsingIAMMethodRequest, error) {
-		// create the signed sts:GetCallerIdentity request and include the challenge
-		signedRequest, err := createSignedSTSIdentityRequest(ctx, challenge,
-			withFIPSEndpoint(params.FIPS),
-			withRegionalEndpoint(true),
-		)
-		if err != nil {
-			return nil, trace.Wrap(err)
-		}
-
-		// send the register request including the challenge response
-		return &proto.RegisterUsingIAMMethodRequest{
-			RegisterUsingTokenRequest: registerUsingTokenRequestForParams(token, params),
-			StsIdentityRequest:        signedRequest,
-		}, nil
-	})
-	if err != nil {
-		log.WithError(err).Infof("Failed to register %s using regional STS endpoint", params.ID.Role)
-		return nil, trace.Wrap(err)
-	}
-
-	log.Infof("Successfully registered %s with IAM method using regional STS endpoint", params.ID.Role)
-	return certs, nil
-}
-
-// registerUsingAzureMethod is used to register using the Azure join method. It
-// is able to register through a proxy or through the auth server directly.
-func registerUsingAzureMethod(
-	ctx context.Context, client joinServiceClient, token string, params RegisterParams,
-) (*proto.Certs, error) {
-	certs, err := client.RegisterUsingAzureMethod(ctx, func(challenge string) (*proto.RegisterUsingAzureMethodRequest, error) {
-		imds := azure.NewInstanceMetadataClient()
-		if !imds.IsAvailable(ctx) {
-			return nil, trace.AccessDenied("could not reach instance metadata. Is Teleport running on an Azure VM?")
-		}
-		ad, err := imds.GetAttestedData(ctx, challenge)
-		if err != nil {
-			return nil, trace.Wrap(err)
-		}
-		accessToken, err := imds.GetAccessToken(ctx, params.AzureParams.ClientID)
-		if err != nil {
-			return nil, trace.Wrap(err)
-		}
-
-		return &proto.RegisterUsingAzureMethodRequest{
-			RegisterUsingTokenRequest: registerUsingTokenRequestForParams(token, params),
-			AttestedData:              ad,
-			AccessToken:               accessToken,
-		}, nil
-	})
-	return certs, trace.Wrap(err)
-}
-
-// registerUsingTPMMethod is used to register using the TPM join method. It
-// is able to register through a proxy or through the auth server directly.
-func registerUsingTPMMethod(
-	ctx context.Context,
-	client joinServiceClient,
-	token string,
-	params RegisterParams,
-) (*proto.Certs, error) {
-	log := slog.Default()
-
-	initReq := &proto.RegisterUsingTPMMethodInitialRequest{
-		JoinRequest: registerUsingTokenRequestForParams(token, params),
-	}
-
-	attestation, close, err := tpm.Attest(ctx, log)
-	if err != nil {
-		return nil, trace.Wrap(err)
-	}
-	defer func() {
-		if err := close(); err != nil {
-			log.WarnContext(ctx, "Failed to close TPM", "error", err)
-		}
-	}()
-
-	initReq.AttestationParams = tpm.AttestationParametersToProto(
-		attestation.AttestParams,
-	)
-	// Get the EKKey or EKCert. We want to prefer the EKCert if it is available
-	// as this is signed by the manufacturer.
-	switch {
-	case attestation.Data.EKCert != nil:
-		log.DebugContext(
-			ctx,
-			"Using EKCert for TPM registration",
-			"ekcert_serial", attestation.Data.EKCert.SerialNumber,
-		)
-		initReq.Ek = &proto.RegisterUsingTPMMethodInitialRequest_EkCert{
-			EkCert: attestation.Data.EKCert.Raw,
-		}
-	case attestation.Data.EKPub != nil:
-		log.DebugContext(
-			ctx,
-			"Using EKKey for TPM registration",
-			"ekpub_hash", attestation.Data.EKPubHash,
-		)
-		initReq.Ek = &proto.RegisterUsingTPMMethodInitialRequest_EkKey{
-			EkKey: attestation.Data.EKPub,
-		}
-	default:
-		return nil, trace.BadParameter("tpm has neither ekkey or ekcert")
-	}
-
-	// Submit initial request to the Auth Server.
-	certs, err := client.RegisterUsingTPMMethod(
-		ctx,
-		initReq,
-		func(
-			challenge *proto.TPMEncryptedCredential,
-		) (*proto.RegisterUsingTPMMethodChallengeResponse, error) {
-			// Solve the encrypted credential with our AK to prove possession
-			// and obtain the solution we need to complete the ceremony.
-			solution, err := attestation.Solve(tpm.EncryptedCredentialFromProto(
-				challenge,
-			))
-			if err != nil {
-				return nil, trace.Wrap(err, "activating credential")
-			}
-			return &proto.RegisterUsingTPMMethodChallengeResponse{
-				Solution: solution,
-			}, nil
-		},
-	)
-	return certs, trace.Wrap(err)
-}
-
 // ReRegisterParams specifies parameters for re-registering
 // in the cluster (rotating certificates for existing members)
 type ReRegisterParams struct {
diff --git a/lib/auth/register_test.go b/lib/auth/register_test.go
deleted file mode 100644
index 5f1d248ace8f1..0000000000000
--- a/lib/auth/register_test.go
+++ /dev/null
@@ -1,78 +0,0 @@
-/*
- * Teleport
- * Copyright (C) 2023  Gravitational, Inc.
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Affero General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU Affero General Public License for more details.
- *
- * You should have received a copy of the GNU Affero General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- */
-
-package auth
-
-import (
-	"crypto/tls"
-	"testing"
-	"time"
-
-	"github.com/jonboulle/clockwork"
-	"github.com/stretchr/testify/require"
-
-	"github.com/gravitational/teleport/api/types"
-	"github.com/gravitational/teleport/lib/defaults"
-	"github.com/gravitational/teleport/lib/fixtures"
-	"github.com/gravitational/teleport/lib/utils"
-)
-
-func TestVerifyALPNUpgradedConn(t *testing.T) {
-	t.Parallel()
-
-	auth := newTestTLSServer(t)
-	proxy, err := NewServerIdentity(auth.Auth(), "test-proxy", types.RoleProxy)
-	require.NoError(t, err)
-
-	tests := []struct {
-		name       string
-		serverCert []byte
-		clock      clockwork.Clock
-		checkError require.ErrorAssertionFunc
-	}{
-		{
-			name:       "proxy verified",
-			serverCert: proxy.TLSCertBytes,
-			clock:      auth.Clock(),
-			checkError: require.NoError,
-		},
-		{
-			name:       "proxy expired",
-			serverCert: proxy.TLSCertBytes,
-			clock:      clockwork.NewFakeClockAt(auth.Clock().Now().Add(defaults.CATTL + time.Hour)),
-			checkError: require.Error,
-		},
-		{
-			name:       "not proxy",
-			serverCert: []byte(fixtures.TLSCACertPEM),
-			clock:      auth.Clock(),
-			checkError: require.Error,
-		},
-	}
-
-	for _, test := range tests {
-		t.Run(test.name, func(t *testing.T) {
-			serverCert, err := utils.ReadCertificates(test.serverCert)
-			require.NoError(t, err)
-
-			test.checkError(t, verifyALPNUpgradedConn(test.clock)(tls.ConnectionState{
-				PeerCertificates: serverCert,
-			}))
-		})
-	}
-}
diff --git a/lib/auth/sts_endpoints.go b/lib/auth/sts_endpoints.go
deleted file mode 100644
index c0884fb1a2bd4..0000000000000
--- a/lib/auth/sts_endpoints.go
+++ /dev/null
@@ -1,85 +0,0 @@
-/*
- * Teleport
- * Copyright (C) 2023  Gravitational, Inc.
- *
- * This program is free software: you can redistribute it and/or modify
- * it under the terms of the GNU Affero General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU Affero General Public License for more details.
- *
- * You should have received a copy of the GNU Affero General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- */
-
-package auth
-
-var (
-	// validSTSEndpoints holds a sorted list of all known valid public endpoints for
-	// the AWS STS service. You can generate this list by running
-	// $ go run github.com/nklaassen/sts-endpoints@latest --go-list
-	// Update aws-sdk-go in that package to learn about new endpoints.
-	validSTSEndpoints = []string{
-		"sts-fips.us-east-1.amazonaws.com",
-		"sts-fips.us-east-2.amazonaws.com",
-		"sts-fips.us-west-1.amazonaws.com",
-		"sts-fips.us-west-2.amazonaws.com",
-		"sts.af-south-1.amazonaws.com",
-		"sts.amazonaws.com",
-		"sts.ap-east-1.amazonaws.com",
-		"sts.ap-northeast-1.amazonaws.com",
-		"sts.ap-northeast-2.amazonaws.com",
-		"sts.ap-northeast-3.amazonaws.com",
-		"sts.ap-south-1.amazonaws.com",
-		"sts.ap-south-2.amazonaws.com",
-		"sts.ap-southeast-1.amazonaws.com",
-		"sts.ap-southeast-2.amazonaws.com",
-		"sts.ap-southeast-3.amazonaws.com",
-		"sts.ap-southeast-4.amazonaws.com",
-		"sts.ca-central-1.amazonaws.com",
-		"sts.ca-west-1.amazonaws.com",
-		"sts.cn-north-1.amazonaws.com.cn",
-		"sts.cn-northwest-1.amazonaws.com.cn",
-		"sts.eu-central-1.amazonaws.com",
-		"sts.eu-central-2.amazonaws.com",
-		"sts.eu-north-1.amazonaws.com",
-		"sts.eu-south-1.amazonaws.com",
-		"sts.eu-south-2.amazonaws.com",
-		"sts.eu-west-1.amazonaws.com",
-		"sts.eu-west-2.amazonaws.com",
-		"sts.eu-west-3.amazonaws.com",
-		"sts.il-central-1.amazonaws.com",
-		"sts.me-central-1.amazonaws.com",
-		"sts.me-south-1.amazonaws.com",
-		"sts.sa-east-1.amazonaws.com",
-		"sts.us-east-1.amazonaws.com",
-		"sts.us-east-2.amazonaws.com",
-		"sts.us-gov-east-1.amazonaws.com",
-		"sts.us-gov-west-1.amazonaws.com",
-		"sts.us-iso-east-1.c2s.ic.gov",
-		"sts.us-iso-west-1.c2s.ic.gov",
-		"sts.us-isob-east-1.sc2s.sgov.gov",
-		"sts.us-west-1.amazonaws.com",
-		"sts.us-west-2.amazonaws.com",
-	}
-
-	globalSTSEndpoints = []string{
-		"sts.amazonaws.com",
-		// This is not a real endpoint, but the SDK will select it if
-		// AWS_USE_FIPS_ENDPOINT is set and a region is not.
-		"sts-fips.aws-global.amazonaws.com",
-	}
-
-	fipsSTSEndpoints = []string{
-		"sts-fips.us-east-1.amazonaws.com",
-		"sts-fips.us-east-2.amazonaws.com",
-		"sts-fips.us-west-1.amazonaws.com",
-		"sts-fips.us-west-2.amazonaws.com",
-		"sts.us-gov-east-1.amazonaws.com",
-		"sts.us-gov-west-1.amazonaws.com",
-	}
-)
diff --git a/lib/auth/tls_test.go b/lib/auth/tls_test.go
index 972a2e34532ad..df0618c8d7a0a 100644
--- a/lib/auth/tls_test.go
+++ b/lib/auth/tls_test.go
@@ -57,6 +57,7 @@ import (
 	apiutils "github.com/gravitational/teleport/api/utils"
 	"github.com/gravitational/teleport/api/utils/sshutils"
 	"github.com/gravitational/teleport/lib/auth/authclient"
+	"github.com/gravitational/teleport/lib/auth/join"
 	"github.com/gravitational/teleport/lib/auth/state"
 	"github.com/gravitational/teleport/lib/auth/testauthority"
 	"github.com/gravitational/teleport/lib/authz"
@@ -3394,7 +3395,7 @@ func TestRegisterCAPin(t *testing.T) {
 	caPin := caPins[0]
 
 	// Attempt to register with valid CA pin, should work.
-	_, err = Register(ctx, RegisterParams{
+	_, err = join.Register(ctx, join.RegisterParams{
 		AuthServers: []utils.NetAddr{utils.FromAddr(testSrv.Addr())},
 		Token:       token,
 		ID: state.IdentityID{
@@ -3412,7 +3413,7 @@ func TestRegisterCAPin(t *testing.T) {
 
 	// Attempt to register with multiple CA pins where the auth server only
 	// matches one, should work.
-	_, err = Register(ctx, RegisterParams{
+	_, err = join.Register(ctx, join.RegisterParams{
 		AuthServers: []utils.NetAddr{utils.FromAddr(testSrv.Addr())},
 		Token:       token,
 		ID: state.IdentityID{
@@ -3429,7 +3430,7 @@ func TestRegisterCAPin(t *testing.T) {
 	require.NoError(t, err)
 
 	// Attempt to register with invalid CA pin, should fail.
-	_, err = Register(ctx, RegisterParams{
+	_, err = join.Register(ctx, join.RegisterParams{
 		AuthServers: []utils.NetAddr{utils.FromAddr(testSrv.Addr())},
 		Token:       token,
 		ID: state.IdentityID{
@@ -3446,7 +3447,7 @@ func TestRegisterCAPin(t *testing.T) {
 	require.Error(t, err)
 
 	// Attempt to register with multiple invalid CA pins, should fail.
-	_, err = Register(ctx, RegisterParams{
+	_, err = join.Register(ctx, join.RegisterParams{
 		AuthServers: []utils.NetAddr{utils.FromAddr(testSrv.Addr())},
 		Token:       token,
 		ID: state.IdentityID{
@@ -3482,7 +3483,7 @@ func TestRegisterCAPin(t *testing.T) {
 	require.Len(t, caPins, 2)
 
 	// Attempt to register with multiple CA pins, should work
-	_, err = Register(ctx, RegisterParams{
+	_, err = join.Register(ctx, join.RegisterParams{
 		AuthServers: []utils.NetAddr{utils.FromAddr(testSrv.Addr())},
 		Token:       token,
 		ID: state.IdentityID{
@@ -3527,7 +3528,7 @@ func TestRegisterCAPath(t *testing.T) {
 	require.NoError(t, err)
 
 	// Attempt to register with nothing at the CA path, should work.
-	_, err = Register(ctx, RegisterParams{
+	_, err = join.Register(ctx, join.RegisterParams{
 		AuthServers: []utils.NetAddr{utils.FromAddr(testSrv.Addr())},
 		Token:       token,
 		ID: state.IdentityID{
@@ -3556,7 +3557,7 @@ func TestRegisterCAPath(t *testing.T) {
 	require.NoError(t, err)
 
 	// Attempt to register with valid CA path, should work.
-	_, err = Register(ctx, RegisterParams{
+	_, err = join.Register(ctx, join.RegisterParams{
 		AuthServers: []utils.NetAddr{utils.FromAddr(testSrv.Addr())},
 		Token:       token,
 		ID: state.IdentityID{
diff --git a/lib/service/connect.go b/lib/service/connect.go
index bc61b4b1a5679..eeee5ebb9fb92 100644
--- a/lib/service/connect.go
+++ b/lib/service/connect.go
@@ -45,6 +45,7 @@ import (
 	"github.com/gravitational/teleport/lib"
 	"github.com/gravitational/teleport/lib/auth"
 	"github.com/gravitational/teleport/lib/auth/authclient"
+	"github.com/gravitational/teleport/lib/auth/join"
 	"github.com/gravitational/teleport/lib/auth/native"
 	"github.com/gravitational/teleport/lib/auth/state"
 	"github.com/gravitational/teleport/lib/client"
@@ -442,7 +443,7 @@ func (process *TeleportProcess) firstTimeConnect(role types.SystemRole) (*Connec
 			dataDir = process.Config.DataDir
 		}
 
-		registerParams := auth.RegisterParams{
+		registerParams := join.RegisterParams{
 			Token:                token,
 			ID:                   id,
 			AuthServers:          process.Config.AuthServerAddresses(),
@@ -464,12 +465,12 @@ func (process *TeleportProcess) firstTimeConnect(role types.SystemRole) (*Connec
 			Insecure:             lib.IsInsecureDevMode(),
 		}
 		if registerParams.JoinMethod == types.JoinMethodAzure {
-			registerParams.AzureParams = auth.AzureParams{
+			registerParams.AzureParams = join.AzureParams{
 				ClientID: process.Config.JoinParams.Azure.ClientID,
 			}
 		}
 
-		certs, err := auth.Register(process.ExitContext(), registerParams)
+		certs, err := join.Register(process.ExitContext(), registerParams)
 		if err != nil {
 			if utils.IsUntrustedCertErr(err) {
 				return nil, trace.WrapWithMessage(err, utils.SelfSignedCertsMsg)
diff --git a/lib/tbot/service_bot_identity.go b/lib/tbot/service_bot_identity.go
index f193b2542bc12..11418705398d6 100644
--- a/lib/tbot/service_bot_identity.go
+++ b/lib/tbot/service_bot_identity.go
@@ -33,8 +33,8 @@ import (
 	"github.com/gravitational/teleport/api/client/proto"
 	"github.com/gravitational/teleport/api/types"
 	"github.com/gravitational/teleport/api/utils/retryutils"
-	"github.com/gravitational/teleport/lib/auth"
 	"github.com/gravitational/teleport/lib/auth/authclient"
+	"github.com/gravitational/teleport/lib/auth/join"
 	"github.com/gravitational/teleport/lib/auth/state"
 	"github.com/gravitational/teleport/lib/client"
 	"github.com/gravitational/teleport/lib/reversetunnelclient"
@@ -403,7 +403,7 @@ func botIdentityFromToken(ctx context.Context, log *slog.Logger, cfg *config.Bot
 	}
 
 	expires := time.Now().Add(cfg.CertificateTTL)
-	params := auth.RegisterParams{
+	params := join.RegisterParams{
 		Token: token,
 		ID: state.IdentityID{
 			Role: types.RoleBot,
@@ -439,12 +439,12 @@ func botIdentityFromToken(ctx context.Context, log *slog.Logger, cfg *config.Bot
 	}
 
 	if params.JoinMethod == types.JoinMethodAzure {
-		params.AzureParams = auth.AzureParams{
+		params.AzureParams = join.AzureParams{
 			ClientID: cfg.Onboarding.Azure.ClientID,
 		}
 	}
 
-	certs, err := auth.Register(ctx, params)
+	certs, err := join.Register(ctx, params)
 	if err != nil {
 		return nil, trace.Wrap(err)
 	}