dsa.go

//go:build !cmd_go_bootstrap

package openssl

// #include "goopenssl.h"
import "C"
import (
	"runtime"
	"unsafe"
)

// SupportsDSA returns true if the OpenSSL library supports DSA.
func SupportsDSA() bool {
	ctx := C.go_openssl_EVP_PKEY_CTX_new_id(C.GO_EVP_PKEY_DSA, nil)
	if ctx == nil {
		return false
	}
	C.go_openssl_EVP_PKEY_CTX_free(ctx)
	return true
}

// DSAParameters contains the DSA parameters.
type DSAParameters struct {
	P, Q, G BigInt
}

// PrivateKeyDSA represents a DSA private key.
type PrivateKeyDSA struct {
	DSAParameters
	X, Y BigInt

	// _pkey MUST NOT be accessed directly. Instead, use the withKey method.
	_pkey C.GO_EVP_PKEY_PTR
}

func (k *PrivateKeyDSA) finalize() {
	C.go_openssl_EVP_PKEY_free(k._pkey)
}

func (k *PrivateKeyDSA) withKey(f func(C.GO_EVP_PKEY_PTR) C.int) C.int {
	defer runtime.KeepAlive(k)
	return f(k._pkey)
}

// PublicKeyDSA represents a DSA public key.
type PublicKeyDSA struct {
	DSAParameters
	Y BigInt

	// _pkey MUST NOT be accessed directly. Instead, use the withKey method.
	_pkey C.GO_EVP_PKEY_PTR
}

func (k *PublicKeyDSA) finalize() {
	C.go_openssl_EVP_PKEY_free(k._pkey)
}

func (k *PublicKeyDSA) withKey(f func(C.GO_EVP_PKEY_PTR) C.int) C.int {
	defer runtime.KeepAlive(k)
	return f(k._pkey)
}

// GenerateParametersDSA generates a set of DSA parameters.
func GenerateParametersDSA(l, n int) (DSAParameters, error) {
	// The DSA parameters are generated by creating a new DSA key and
	// extracting the domain parameters from it.

	// Generate a new DSA key context and set the known parameters.
	ctx := C.go_openssl_EVP_PKEY_CTX_new_id(C.GO_EVP_PKEY_DSA, nil)
	if ctx == nil {
		return DSAParameters{}, newOpenSSLError("EVP_PKEY_CTX_new_id failed")
	}
	defer C.go_openssl_EVP_PKEY_CTX_free(ctx)
	if C.go_openssl_EVP_PKEY_paramgen_init(ctx) != 1 {
		return DSAParameters{}, newOpenSSLError("EVP_PKEY_paramgen_init failed")
	}
	if C.go_openssl_EVP_PKEY_CTX_ctrl(ctx, C.GO_EVP_PKEY_DSA, -1, C.GO_EVP_PKEY_CTRL_DSA_PARAMGEN_BITS, C.int(l), nil) != 1 {
		return DSAParameters{}, newOpenSSLError("EVP_PKEY_CTX_ctrl failed")
	}
	if C.go_openssl_EVP_PKEY_CTX_ctrl(ctx, C.GO_EVP_PKEY_DSA, -1, C.GO_EVP_PKEY_CTRL_DSA_PARAMGEN_Q_BITS, C.int(n), nil) != 1 {
		return DSAParameters{}, newOpenSSLError("EVP_PKEY_CTX_ctrl failed")
	}
	var pkey C.GO_EVP_PKEY_PTR
	if C.go_openssl_EVP_PKEY_paramgen(ctx, &pkey) != 1 {
		return DSAParameters{}, newOpenSSLError("EVP_PKEY_paramgen failed")
	}
	defer C.go_openssl_EVP_PKEY_free(pkey)

	// Extract the domain parameters from the generated key.
	var p, q, g C.GO_BIGNUM_PTR
	switch vMajor {
	case 1:
		dsa := getDSA(pkey)
		if vMinor == 0 {
			C.go_openssl_DSA_get0_pqg_backport(dsa, &p, &q, &g)
		} else {
			C.go_openssl_DSA_get0_pqg(dsa, &p, &q, &g)
		}
	case 3:
		defer func() {
			C.go_openssl_BN_free(p)
			C.go_openssl_BN_free(q)
			C.go_openssl_BN_free(g)
		}()
		if C.go_openssl_EVP_PKEY_get_bn_param(pkey, _OSSL_PKEY_PARAM_FFC_P, &p) != 1 ||
			C.go_openssl_EVP_PKEY_get_bn_param(pkey, _OSSL_PKEY_PARAM_FFC_Q, &q) != 1 ||
			C.go_openssl_EVP_PKEY_get_bn_param(pkey, _OSSL_PKEY_PARAM_FFC_G, &g) != 1 {
			return DSAParameters{}, newOpenSSLError("EVP_PKEY_get_bn_param")
		}
	default:
		panic(errUnsupportedVersion())
	}

	return DSAParameters{
		P: bnToBig(p),
		Q: bnToBig(q),
		G: bnToBig(g),
	}, nil
}

// NewPrivateKeyDSA creates a new DSA private key from the given parameters.
func NewPrivateKeyDSA(params DSAParameters, x, y BigInt) (*PrivateKeyDSA, error) {
	if x == nil || y == nil {
		panic("x and y must not be nil")
	}
	pkey, err := newDSA(params, x, y)
	if err != nil {
		return nil, err
	}
	k := &PrivateKeyDSA{params, x, y, pkey}
	runtime.SetFinalizer(k, (*PrivateKeyDSA).finalize)
	return k, nil
}

// NewPublicKeyDSA creates a new DSA public key from the given parameters.
func NewPublicKeyDSA(params DSAParameters, y BigInt) (*PublicKeyDSA, error) {
	if y == nil {
		panic("y must not be nil")
	}
	pkey, err := newDSA(params, nil, y)
	if err != nil {
		return nil, err
	}
	k := &PublicKeyDSA{params, y, pkey}
	runtime.SetFinalizer(k, (*PublicKeyDSA).finalize)
	return k, nil
}

// GenerateKeyDSA generates a new private DSA key using the given parameters.
func GenerateKeyDSA(params DSAParameters) (x, y BigInt, err error) {
	pkey, err := newDSA(params, nil, nil)
	if err != nil {
		return nil, nil, err
	}
	defer C.go_openssl_EVP_PKEY_free(pkey)
	var bx, by C.GO_BIGNUM_PTR
	switch vMajor {
	case 1:
		dsa := getDSA(pkey)
		if vMinor == 0 {
			C.go_openssl_DSA_get0_key_backport(dsa, &by, &bx)
		} else {
			C.go_openssl_DSA_get0_key(dsa, &by, &bx)
		}
	case 3:
		defer func() {
			C.go_openssl_BN_clear_free(bx)
			C.go_openssl_BN_free(by)
		}()
		if C.go_openssl_EVP_PKEY_get_bn_param(pkey, _OSSL_PKEY_PARAM_PUB_KEY, &by) != 1 ||
			C.go_openssl_EVP_PKEY_get_bn_param(pkey, _OSSL_PKEY_PARAM_PRIV_KEY, &bx) != 1 {
			return nil, nil, newOpenSSLError("EVP_PKEY_get_bn_param")
		}
	default:
		panic(errUnsupportedVersion())
	}
	return bnToBig(bx), bnToBig(by), nil
}

// SignDSA signs a hash (which should be the result of hashing a larger message).
func SignDSA(priv *PrivateKeyDSA, hash []byte) ([]byte, error) {
	return evpSign(priv.withKey, 0, 0, 0, hash)
}

// VerifyDSA verifiessig using the public key, pub.
func VerifyDSA(pub *PublicKeyDSA, hash []byte, sig []byte) bool {
	return evpVerify(pub.withKey, 0, 0, 0, sig, hash) == nil
}

func newDSA(params DSAParameters, x, y BigInt) (C.GO_EVP_PKEY_PTR, error) {
	switch vMajor {
	case 1:
		return newDSA1(params, x, y)
	case 3:
		return newDSA3(params, x, y)
	default:
		panic(errUnsupportedVersion())
	}
}

func newDSA1(params DSAParameters, x, y BigInt) (pkey C.GO_EVP_PKEY_PTR, err error) {
	checkMajorVersion(1)

	dsa := C.go_openssl_DSA_new()
	if dsa == nil {
		return nil, newOpenSSLError("DSA_new failed")
	}
	defer func() {
		if pkey == nil {
			C.go_openssl_DSA_free(dsa)
		}
	}()

	p, q, g := bigToBN(params.P), bigToBN(params.Q), bigToBN(params.G)
	var ret C.int
	if vMinor == 0 {
		ret = C.go_openssl_DSA_set0_pqg_backport(dsa, p, q, g)
	} else {
		ret = C.go_openssl_DSA_set0_pqg(dsa, p, q, g)
	}
	if ret != 1 {
		C.go_openssl_BN_free(p)
		C.go_openssl_BN_free(q)
		C.go_openssl_BN_free(g)
		return nil, newOpenSSLError("DSA_set0_pqg failed")
	}
	if y != nil {
		pub, priv := bigToBN(y), bigToBN(x)
		if vMinor == 0 {
			ret = C.go_openssl_DSA_set0_key_backport(dsa, pub, priv)
		} else {
			ret = C.go_openssl_DSA_set0_key(dsa, pub, priv)
		}
		if ret != 1 {
			C.go_openssl_BN_free(pub)
			C.go_openssl_BN_clear_free(priv)
			return nil, newOpenSSLError("DSA_set0_key failed")
		}
	} else {
		if C.go_openssl_DSA_generate_key(dsa) != 1 {
			return nil, newOpenSSLError("DSA_generate_key failed")
		}
	}
	pkey = C.go_openssl_EVP_PKEY_new()
	if pkey == nil {
		return nil, newOpenSSLError("EVP_PKEY_new failed")
	}
	if C.go_openssl_EVP_PKEY_assign(pkey, C.GO_EVP_PKEY_DSA, unsafe.Pointer(dsa)) != 1 {
		C.go_openssl_EVP_PKEY_free(pkey)
		return nil, newOpenSSLError("EVP_PKEY_assign failed")
	}
	return pkey, nil
}

func newDSA3(params DSAParameters, x, y BigInt) (C.GO_EVP_PKEY_PTR, error) {
	checkMajorVersion(3)

	bld, err := newParamBuilder()
	if err != nil {
		return nil, err
	}
	defer bld.finalize()

	bld.addBigInt(_OSSL_PKEY_PARAM_FFC_P, params.P, false)
	bld.addBigInt(_OSSL_PKEY_PARAM_FFC_Q, params.Q, false)
	bld.addBigInt(_OSSL_PKEY_PARAM_FFC_G, params.G, false)
	selection := C.int(C.GO_EVP_PKEY_KEYPAIR)
	if y != nil {
		bld.addBigInt(_OSSL_PKEY_PARAM_PUB_KEY, y, false)
		if x == nil {
			selection = C.int(C.GO_EVP_PKEY_PUBLIC_KEY)
		}
	}
	if x != nil {
		bld.addBigInt(_OSSL_PKEY_PARAM_PRIV_KEY, x, true)
	}
	bldparams, err := bld.build()
	if err != nil {
		return nil, err
	}
	defer C.go_openssl_OSSL_PARAM_free(bldparams)
	pkey, err := newEvpFromParams(C.GO_EVP_PKEY_DSA, selection, bldparams)
	if err != nil {
		return nil, err
	}
	if y != nil {
		return pkey, nil
	}
	// pkey doesn't contain the public component, but the crypto/dsa package
	// expects it to be always there. Generate a new key using pkey as domain
	// parameters placeholder.
	defer C.go_openssl_EVP_PKEY_free(pkey)
	ctx := C.go_openssl_EVP_PKEY_CTX_new_from_pkey(nil, pkey, nil)
	if ctx == nil {
		return nil, newOpenSSLError("EVP_PKEY_CTX_new_from_pkey")
	}
	defer C.go_openssl_EVP_PKEY_CTX_free(ctx)
	if C.go_openssl_EVP_PKEY_keygen_init(ctx) != 1 {
		return nil, newOpenSSLError("EVP_PKEY_keygen_init")
	}
	var gkey C.GO_EVP_PKEY_PTR
	if C.go_openssl_EVP_PKEY_keygen(ctx, &gkey) != 1 {
		return nil, newOpenSSLError("EVP_PKEY_keygen")
	}
	return gkey, nil
}

// getDSA returns the DSA from pkey.
// If pkey does not contain an DSA it panics.
// The returned key should not be freed.
func getDSA(pkey C.GO_EVP_PKEY_PTR) (key C.GO_DSA_PTR) {
	if vMajor == 1 && vMinor == 0 {
		if key0 := C.go_openssl_EVP_PKEY_get0(pkey); key0 != nil {
			key = C.GO_DSA_PTR(key0)
		}
	} else {
		key = C.go_openssl_EVP_PKEY_get0_DSA(pkey)
	}
	if key == nil {
		panic("pkey does not contain an DSA")
	}
	return key
}