add func to verify rsa signature

rsa.go

@@ -18,6 +18,7 @@ package openssl
 import "C"
 import (
 	"errors"
+	"strings"
 	"unsafe"
 )
 
@@ -75,3 +76,81 @@ func VerifyRecoverRSASignature(publicKey, signature []byte) ([]byte, error) {
 	recoveredBytes := C.GoBytes(unsafe.Pointer(rout), C.int(routlen))
 	return recoveredBytes, nil
 }
+
+// VerifyRSASignature verifies that a signature is valid for some data and a Public Key
+// - Parameter publicKey: The OpenSSL EVP_PKEY public key in DER format
+// - Parameter signature: The signature to verify in DER format
+// - Parameter data: The data used to generate the signature
+// - Parameter digest: The name of the digest to use. The currently supported values are: sha1, sha224, sha256, sha384, sha512, ripemd160, rsassapss
+// - Returns: True if the signature was verified
+func VerifyRSASignature(publicKey, signature, data []byte, digest string) (bool, error) {
+	digest = strings.ToLower(digest)
+	digestName := "sha256"	
+	switch {
+	case strings.Contains(digest, "sha1"):
+		digestName = "sha1"
+	case strings.Contains(digest, "sha224"):
+		digestName = "sha224"
+	case strings.Contains(digest, "sha256"), strings.Contains(digest, "rsassapss"):
+		digestName = "sha256"
+	case strings.Contains(digest, "sha384"):
+		digestName= "sha384"
+	case strings.Contains(digest, "sha512"):
+		digestName = "sha512"
+	case strings.Contains(digest, "ripemd160"):
+		digestName = "ripemd160"
+	}
+	md, err := GetDigestByName(digestName)
+	if err != nil {
+		return false, err
+	}
+
+	inf := C.BIO_new(C.BIO_s_mem())
+	if inf == nil {
+		return false, errors.New("failed allocating input buffer")
+	}
+	defer C.BIO_free(inf)
+	_, err = asAnyBio(inf).Write(publicKey)
+	if err != nil {
+		return false, err
+	}
+	pubKey := C.d2i_PUBKEY_bio(inf, nil)
+	if pubKey == nil {
+		return false, errors.New("failed to load public key")
+	}
+	defer C.EVP_PKEY_free(pubKey)
+	ctx := C.EVP_PKEY_CTX_new(pubKey, nil)
+	if ctx == nil {
+		return false, errors.New("failed to setup context")
+	}
+	defer C.EVP_PKEY_CTX_free(ctx)
+
+	mdctx := C.EVP_MD_CTX_new()
+	defer C.EVP_MD_CTX_free(mdctx)
+
+	nRes := C.EVP_DigestVerifyInit(mdctx, &ctx, md.ptr, nil, pubKey)
+	if nRes != 1 {
+		return false, errors.New("unable to init digest verify")
+	}
+
+	if strings.Contains(digestName, "rsassapss") {
+		if C.X_EVP_PKEY_CTX_ctrl_str(ctx, C.CString("rsa_padding_mode"), C.CString("pss") ) <= 0 {
+			return false, errors.New("failed to set rsa padding mode")
+		}
+		if C.X_EVP_PKEY_CTX_ctrl_str(ctx, C.CString("rsa_pss_saltlen"), C.CString("auto")) <= 0 {
+			return false, errors.New("failed to set rsa pss saltlen")
+		}
+	}
+
+	nRes = C.EVP_DigestUpdate(mdctx, unsafe.Pointer((*C.uchar)(&data[0])), C.size_t(len(data)))
+	if nRes != 1 {
+		return false, errors.New("unable to update digest")
+	}
+
+	nRes = C.EVP_DigestVerifyFinal(mdctx, (*C.uchar)(&signature[0]), C.size_t(len(signature)))
+	if nRes != 1 {
+		return false, nil
+	}
+
+	return true, nil
+}

shim.c

@@ -741,6 +741,10 @@ int X_EVP_PKEY_CTX_set_rsa_padding(EVP_PKEY_CTX *ctx, int pad) {
 	return EVP_PKEY_CTX_set_rsa_padding(ctx, pad);
 }
 
+int X_EVP_PKEY_CTX_ctrl_str(EVP_PKEY_CTX *ctx, const char *type, const char *value) {
+	return EVP_PKEY_CTX_ctrl_str(ctx, type, value);
+}
+
 size_t X_HMAC_size(const HMAC_CTX *e) {
 	return HMAC_size(e);
 }

shim.h

@@ -156,6 +156,7 @@ extern const EVP_CIPHER *X_EVP_CIPHER_CTX_cipher(EVP_CIPHER_CTX *ctx);
 extern int X_EVP_CIPHER_CTX_encrypting(const EVP_CIPHER_CTX *ctx);
 extern int X_EVP_PKEY_CTX_set_ec_paramgen_curve_nid(EVP_PKEY_CTX *ctx, int nid);
 extern int X_EVP_PKEY_CTX_set_rsa_padding(EVP_PKEY_CTX *ctx, int pad);
+extern int X_EVP_PKEY_CTX_ctrl_str(EVP_PKEY_CTX *ctx, const char *type, const char *value);
 
 /* HMAC methods */
 extern size_t X_HMAC_size(const HMAC_CTX *e);