Add support for openssh comments when generating a private key

.changes/unreleased/ENHANCEMENTS-20230803-094241.yaml

@@ -0,0 +1,6 @@
+kind: ENHANCEMENTS
+body: 'resource/tls_private_key: add openssh_comment attribute
+  data-source/tls_public_key: add openssh_comment attribute'
+time: 2023-08-03T09:42:41.390232535Z
+custom:
+  Issue: "395"

docs/data-sources/public_key.md

@@ -43,6 +43,7 @@ data "tls_public_key" "private_key_openssh-example" {
 
 - `algorithm` (String) The name of the algorithm used by the given private key. Possible values are: `RSA`, `ECDSA`, `ED25519`.
 - `id` (String) Unique identifier for this data source: hexadecimal representation of the SHA1 checksum of the data source.
+- `openssh_comment` (String) The OpenSSH comment.
 - `public_key_fingerprint_md5` (String) The fingerprint of the public key data in OpenSSH MD5 hash format, e.g. `aa:bb:cc:...`. Only available if the selected private key format is compatible, as per the rules for `public_key_openssh` and [ECDSA P224 limitations](../../docs#limitations).
 - `public_key_fingerprint_sha256` (String) The fingerprint of the public key data in OpenSSH SHA256 hash format, e.g. `SHA256:...`. Only available if the selected private key format is compatible, as per the rules for `public_key_openssh` and [ECDSA P224 limitations](../../docs#limitations).
 - `public_key_openssh` (String) The public key, in  [OpenSSH PEM (RFC 4716)](https://datatracker.ietf.org/doc/html/rfc4716) format. This is also known as ['Authorized Keys'](https://www.ssh.com/academy/ssh/authorized_keys/openssh#format-of-the-authorized-keys-file) format. This is not populated for `ECDSA` with curve `P224`, as it is [not supported](../../docs#limitations). **NOTE**: the [underlying](https://pkg.go.dev/encoding/pem#Encode) [libraries](https://pkg.go.dev/golang.org/x/crypto/ssh#MarshalAuthorizedKey) that generate this value append a `\n` at the end of the PEM. In case this disrupts your use case, we recommend using [`trimspace()`](https://www.terraform.io/language/functions/trimspace).

docs/resources/private_key.md

@@ -53,6 +53,7 @@ resource "tls_private_key" "ed25519-example" {
 ### Optional
 
 - `ecdsa_curve` (String) When `algorithm` is `ECDSA`, the name of the elliptic curve to use. Currently-supported values are: `P224`, `P256`, `P384`, `P521`. (default: `P224`).
+- `openssh_comment` (String) Comment to add to the OpenSSH key (default: `""`).
 - `rsa_bits` (Number) When `algorithm` is `RSA`, the size of the generated RSA key, in bits (default: `2048`).
 
 ### Read-Only

internal/provider/common_key.go

@@ -14,6 +14,7 @@ import (
 	"crypto/x509"
 	"encoding/pem"
 	"fmt"
+	"strings"
 
 	"github.com/hashicorp/terraform-plugin-framework/diag"
 	"github.com/hashicorp/terraform-plugin-framework/path"
@@ -201,6 +202,15 @@ func setPublicKeyAttributes(ctx context.Context, s *tfsdk.State, prvKey crypto.P
 		sshPubKeyBytes := ssh.MarshalAuthorizedKey(sshPubKey)
 
 		pubKeySSH = string(sshPubKeyBytes)
+
+		// Manually add the comment as MarshalAuthorizedKeys ignores it: https://github.com/golang/go/issues/46870
+		var comment *string
+		diags.Append(s.GetAttribute(ctx, path.Root("openssh_comment"), &comment)...)
+
+		if comment != nil {
+			pubKeySSH = fmt.Sprintf("%s %s\n", strings.TrimSuffix(pubKeySSH, "\n"), *comment)
+		}
+
 		pubKeySSHFingerprintMD5 = ssh.FingerprintLegacyMD5(sshPubKey)
 		pubKeySSHFingerprintSHA256 = ssh.FingerprintSHA256(sshPubKey)
 	}

internal/provider/data_source_public_key.go

@@ -69,6 +69,10 @@ func (d *publicKeyDataSource) Schema(ctx context.Context, req datasource.SchemaR
 				Description: "The name of the algorithm used by the given private key. " +
 					fmt.Sprintf("Possible values are: `%s`. ", strings.Join(supportedAlgorithmsStr(), "`, `")),
 			},
+			"openssh_comment": schema.StringAttribute{
+				Computed:    true,
+				Description: "The OpenSSH comment.",
+			},
 			"public_key_pem": schema.StringAttribute{
 				Computed: true,
 				Description: "The public key, in [PEM (RFC 1421)](https://datatracker.ietf.org/doc/html/rfc1421) format. " +

internal/provider/models.go

@@ -65,6 +65,7 @@ type certificateSubjectModel struct {
 
 type privateKeyResourceModel struct {
 	Algorithm                  types.String `tfsdk:"algorithm"`
+	OpenSSHComment             types.String `tfsdk:"openssh_comment"`
 	RSABits                    types.Int64  `tfsdk:"rsa_bits"`
 	ECDSACurve                 types.String `tfsdk:"ecdsa_curve"`
 	PrivateKeyPem              types.String `tfsdk:"private_key_pem"`

internal/provider/resource_private_key.go

@@ -61,6 +61,13 @@ func (r *privateKeyResource) Schema(_ context.Context, req resource.SchemaReques
 			},
 
 			// Optional attributes
+			"openssh_comment": schema.StringAttribute{
+				Optional: true,
+				PlanModifiers: []planmodifier.String{
+					stringplanmodifier.RequiresReplace(),
+				},
+				MarkdownDescription: "Comment to add to the OpenSSH key (default: `\"\"`).",
+			},
 			"rsa_bits": schema.Int64Attribute{
 				Optional: true,
 				Computed: true,
@@ -159,6 +166,10 @@ func privateKeyResourceSchemaV1() schema.Schema {
 			},
 
 			// Optional attributes
+			"openssh_comment": schema.StringAttribute{
+				Optional:            true,
+				MarkdownDescription: "Comment to add to the OpenSSH key (default: `\"\"`).",
+			},
 			"rsa_bits": schema.Int64Attribute{
 				Optional:            true,
 				Computed:            true,
@@ -318,12 +329,11 @@ func (r *privateKeyResource) Create(ctx context.Context, req resource.CreateRequ
 	tflog.Debug(ctx, "Marshalling private key to OpenSSH PEM (if supported)")
 	newState.PrivateKeyOpenSSH = types.StringValue("")
 	if prvKeySupportsOpenSSHMarshalling(prvKey) {
-		openSSHKeyPemBlock, err := openssh.MarshalPrivateKey(prvKey, "")
+		openSSHKeyPemBlock, err := openssh.MarshalPrivateKey(prvKey, newState.OpenSSHComment.ValueString())
 		if err != nil {
 			res.Diagnostics.AddError("Unable to marshal private key into OpenSSH format", err.Error())
 			return
 		}
-
 		newState.PrivateKeyOpenSSH = types.StringValue(string(pem.EncodeToMemory(openSSHKeyPemBlock)))
 	}
 

internal/provider/resource_private_key_test.go

@@ -401,3 +401,29 @@ func TestAccPrivateKeyED25519_UpgradeFromVersion3_4_0(t *testing.T) {
 		},
 	})
 }
+
+func TestOpenSSHComment(t *testing.T) {
+	r.UnitTest(t, r.TestCase{
+		ProtoV5ProviderFactories: protoV5ProviderFactories(),
+		Steps: []r.TestStep{
+			{
+				Config: `
+					resource "tls_private_key" "test" {
+						algorithm = "ED25519"
+						openssh_comment = "test@test"
+					}
+				`,
+				Check: r.ComposeAggregateTestCheckFunc(
+					tu.TestCheckPEMFormat("tls_private_key.test", "private_key_pem", PreamblePrivateKeyPKCS8.String()),
+					tu.TestCheckPEMFormat("tls_private_key.test", "public_key_pem", PreamblePublicKey.String()),
+					tu.TestCheckPEMFormat("tls_private_key.test", "private_key_openssh", PreamblePrivateKeyOpenSSH.String()),
+					tu.TestCheckPEMFormat("tls_private_key.test", "private_key_pem_pkcs8", PreamblePrivateKeyPKCS8.String()),
+					r.TestMatchResourceAttr("tls_private_key.test", "public_key_openssh", regexp.MustCompile(`^ssh-ed25519 `)),
+					r.TestMatchResourceAttr("tls_private_key.test", "public_key_openssh", regexp.MustCompile(` test@test\n$`)),
+					r.TestMatchResourceAttr("tls_private_key.test", "public_key_fingerprint_md5", regexp.MustCompile(`^([abcdef\d]{2}:){15}[abcdef\d]{2}`)),
+					r.TestMatchResourceAttr("tls_private_key.test", "public_key_fingerprint_sha256", regexp.MustCompile(`^SHA256:`)),
+				),
+			},
+		},
+	})
+}