diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index dbef6aa21..56633464b 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -1633,6 +1633,11 @@ int mbedtls_ssl_tls13_start_handshake_msg( mbedtls_ssl_context *ssl,
*/
int mbedtls_ssl_tls13_process_certificate( mbedtls_ssl_context *ssl );
+/*
+ * Generic handler of Certificate Verify
+ */
+int mbedtls_ssl_tls13_process_certificate_verify( mbedtls_ssl_context *ssl );
+
/*
* Write TLS 1.3 handshake message tail
*/
diff --git a/library/ssl_tls13_client.c b/library/ssl_tls13_client.c
index 0fb09c4ce..6e16c07ba 100644
--- a/library/ssl_tls13_client.c
+++ b/library/ssl_tls13_client.c
@@ -1584,7 +1584,12 @@ static int ssl_tls1_3_process_server_certificate( mbedtls_ssl_context *ssl )
*/
static int ssl_tls1_3_process_certificate_verify( mbedtls_ssl_context *ssl )
{
- MBEDTLS_SSL_DEBUG_MSG( 1, ( "%s hasn't been implemented", __func__ ) );
+ int ret;
+
+ ret = mbedtls_ssl_tls13_process_certificate_verify( ssl );
+ if( ret != 0 )
+ return( ret );
+
mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_SERVER_FINISHED );
return( 0 );
}
diff --git a/library/ssl_tls13_generic.c b/library/ssl_tls13_generic.c
index c8601ce17..e484b7966 100644
--- a/library/ssl_tls13_generic.c
+++ b/library/ssl_tls13_generic.c
@@ -23,14 +23,15 @@
#if defined(MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL)
+#include <string.h>
+
#include "mbedtls/error.h"
#include "mbedtls/debug.h"
+#include "mbedtls/oid.h"
+#include "mbedtls/platform.h"
#include "ssl_misc.h"
-#include <mbedtls/debug.h>
-#include <mbedtls/oid.h>
-#include <mbedtls/platform.h>
-
+#include "ssl_tls13_keys.h"
int mbedtls_ssl_tls1_3_fetch_handshake_msg( mbedtls_ssl_context *ssl,
unsigned hs_type,
@@ -217,8 +218,374 @@ int mbedtls_ssl_tls13_write_sig_alg_ext( mbedtls_ssl_context *ssl,
return( 0 );
}
+/*
+ * The ssl_tls13_create_verify_structure() creates the verify structure.
+ * As input, it requires the transcript hash.
+ *
+ * The caller has to ensure that the buffer has size at least
+ * SSL_VERIFY_STRUCT_MAX_SIZE bytes.
+ */
+static void ssl_tls13_create_verify_structure( unsigned char *transcript_hash,
+ size_t transcript_hash_len,
+ unsigned char *verify_buffer,
+ size_t *verify_buffer_len,
+ int from )
+{
+ size_t idx = 0;
+
+ /* RFC 8446, Section 4.4.3:
+ *
+ * The digital signature [in the CertificateVerify message] is then
+ * computed over the concatenation of:
+ * - A string that consists of octet 32 (0x20) repeated 64 times
+ * - The context string
+ * - A single 0 byte which serves as the separator
+ * - The content to be signed
+ */
+ uint8_t const verify_padding_val = 0x20;
+ size_t const verify_padding_len = 64;
+
+ memset( verify_buffer + idx, verify_padding_val, verify_padding_len );
+ idx += verify_padding_len;
+
+ if( from == MBEDTLS_SSL_IS_CLIENT )
+ {
+ memcpy( verify_buffer + idx, MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( client_cv ) );
+ idx += MBEDTLS_SSL_TLS1_3_LBL_LEN( client_cv );
+ }
+ else
+ { /* from == MBEDTLS_SSL_IS_SERVER */
+ memcpy( verify_buffer + idx, MBEDTLS_SSL_TLS1_3_LBL_WITH_LEN( server_cv ) );
+ idx += MBEDTLS_SSL_TLS1_3_LBL_LEN( server_cv );
+ }
+
+ verify_buffer[idx++] = 0x0;
+
+ memcpy( verify_buffer + idx, transcript_hash, transcript_hash_len );
+ idx += transcript_hash_len;
+
+ *verify_buffer_len = idx;
+}
+
#endif /* MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED */
+/*
+ * STATE HANDLING: Read CertificateVerify
+ */
+/* Macro to express the length of the verify structure length.
+ *
+ * The structure is computed per TLS 1.3 specification as:
+ * - 64 bytes of octet 32,
+ * - 33 bytes for the context string
+ * (which is either "TLS 1.3, client CertificateVerify"
+ * or "TLS 1.3, server CertificateVerify"),
+ * - 1 byte for the octet 0x0, which servers as a separator,
+ * - 32 or 48 bytes for the Transcript-Hash(Handshake Context, Certificate)
+ * (depending on the size of the transcript_hash)
+ *
+ * This results in a total size of
+ * - 130 bytes for a SHA256-based transcript hash, or
+ * (64 + 33 + 1 + 32 bytes)
+ * - 146 bytes for a SHA384-based transcript hash.
+ * (64 + 33 + 1 + 48 bytes)
+ *
+ */
+#define SSL_VERIFY_STRUCT_MAX_SIZE ( 64 + \
+ 33 + \
+ 1 + \
+ MBEDTLS_MD_MAX_SIZE \
+ )
+/* Coordinate: Check whether a certificate verify message is expected.
+ * Returns a negative value on failure, and otherwise
+ * - SSL_CERTIFICATE_VERIFY_SKIP
+ * - SSL_CERTIFICATE_VERIFY_READ
+ * to indicate if the CertificateVerify message should be present or not.
+ */
+#define SSL_CERTIFICATE_VERIFY_SKIP 0
+#define SSL_CERTIFICATE_VERIFY_READ 1
+static int ssl_tls13_process_certificate_verify_coordinate(
+ mbedtls_ssl_context *ssl )
+{
+ if( mbedtls_ssl_tls1_3_some_psk_enabled( ssl ) )
+ return( SSL_CERTIFICATE_VERIFY_SKIP );
+
+#if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED)
+ if( ssl->session_negotiate->peer_cert == NULL )
+ return( SSL_CERTIFICATE_VERIFY_SKIP );
+ return( SSL_CERTIFICATE_VERIFY_READ );
+#else
+ MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+ return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+#endif /* MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED */
+}
+
+#if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED)
+static int ssl_tls13_process_certificate_verify_parse( mbedtls_ssl_context *ssl,
+ const unsigned char *buf,
+ const unsigned char *end,
+ const unsigned char *verify_buffer,
+ size_t verify_buffer_len )
+{
+ int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+ const unsigned char *p = buf;
+ uint16_t algorithm;
+ const uint16_t *tls13_sig_alg = ssl->conf->tls13_sig_algs;
+ size_t signature_len;
+ mbedtls_pk_type_t sig_alg;
+ mbedtls_md_type_t md_alg;
+ unsigned char verify_hash[MBEDTLS_TLS1_3_MD_MAX_SIZE];
+ size_t verify_hash_len;
+
+ /*
+ * struct {
+ * SignatureScheme algorithm;
+ * opaque signature<0..2^16-1>;
+ * } CertificateVerify;
+ */
+ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 2 );
+ algorithm = MBEDTLS_GET_UINT16_BE( p, 0 );
+ p += 2;
+
+ /* RFC 8446 section 4.4.3
+ *
+ * If the CertificateVerify message is sent by a server, the signature algorithm
+ * MUST be one offered in the client's "signature_algorithms" extension unless
+ * no valid certificate chain can be produced without unsupported algorithms
+ *
+ * RFC 8446 section 4.4.2.2
+ *
+ * If the client cannot construct an acceptable chain using the provided
+ * certificates and decides to abort the handshake, then it MUST abort the handshake
+ * with an appropriate certificate-related alert (by default, "unsupported_certificate").
+ *
+ * Check if algorithm in offered signature algorithms. Send `unsupported_certificate`
+ * alert message on failure.
+ */
+ while( 1 )
+ {
+ /* Found algorithm in offered signature algorithms */
+ if( *tls13_sig_alg == algorithm )
+ break;
+
+ if( *tls13_sig_alg == MBEDTLS_TLS13_SIG_NONE )
+ {
+ /* End of offered signature algorithms list */
+ MBEDTLS_SSL_DEBUG_MSG( 1,
+ ( "signature algorithm(%04x) not in offered"
+ "signature algorithms ",
+ ( unsigned int ) algorithm ) );
+ MBEDTLS_SSL_PEND_FATAL_ALERT(
+ MBEDTLS_SSL_ALERT_MSG_UNSUPPORTED_CERT,
+ MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
+ return MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE;
+ }
+
+ tls13_sig_alg++;
+ }
+
+ /* We currently only support ECDSA-based signatures */
+ switch( algorithm )
+ {
+ case MBEDTLS_TLS13_SIG_ECDSA_SECP256R1_SHA256:
+ md_alg = MBEDTLS_MD_SHA256;
+ sig_alg = MBEDTLS_PK_ECDSA;
+ break;
+ case MBEDTLS_TLS13_SIG_ECDSA_SECP384R1_SHA384:
+ md_alg = MBEDTLS_MD_SHA384;
+ sig_alg = MBEDTLS_PK_ECDSA;
+ break;
+ case MBEDTLS_TLS13_SIG_ECDSA_SECP521R1_SHA512:
+ md_alg = MBEDTLS_MD_SHA512;
+ sig_alg = MBEDTLS_PK_ECDSA;
+ break;
+ default:
+ MBEDTLS_SSL_DEBUG_MSG( 1, ( "Certificate Verify: Unknown signature algorithm." ) );
+ MBEDTLS_SSL_PEND_FATAL_ALERT(
+ MBEDTLS_SSL_ALERT_MSG_UNSUPPORTED_CERT,
+ MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
+ return( MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
+ }
+
+ MBEDTLS_SSL_DEBUG_MSG( 3, ( "Certificate Verify: Signature algorithm ( %04x )",
+ ( unsigned int ) algorithm ) );
+
+ /*
+ * Check the certificate's key type matches the signature alg
+ */
+ if( !mbedtls_pk_can_do( &ssl->session_negotiate->peer_cert->pk, sig_alg ) )
+ {
+ MBEDTLS_SSL_DEBUG_MSG( 1, ( "signature algorithm doesn't match cert key" ) );
+ MBEDTLS_SSL_PEND_FATAL_ALERT(
+ MBEDTLS_SSL_ALERT_MSG_UNSUPPORTED_CERT,
+ MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
+ return( MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
+ }
+
+ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, 2 );
+ signature_len = MBEDTLS_GET_UINT16_BE( p, 0 );
+ p += 2;
+ MBEDTLS_SSL_CHK_BUF_READ_PTR( p, end, signature_len );
+
+ /* Hash verify buffer with indicated hash function */
+ switch( md_alg )
+ {
+#if defined(MBEDTLS_SHA256_C)
+ case MBEDTLS_MD_SHA256:
+ verify_hash_len = 32;
+ if( ( ret = mbedtls_sha256( verify_buffer,
+ verify_buffer_len,
+ verify_hash,
+ 0 ) ) != 0 )
+ {
+ MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_sha256", ret );
+ MBEDTLS_SSL_PEND_FATAL_ALERT(
+ MBEDTLS_SSL_ALERT_MSG_UNSUPPORTED_CERT,
+ MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
+ return( MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
+ }
+ break;
+#endif /* MBEDTLS_SHA256_C */
+
+#if defined(MBEDTLS_SHA384_C)
+ case MBEDTLS_MD_SHA384:
+ verify_hash_len = 48;
+ if( ( ret = mbedtls_sha512( verify_buffer,
+ verify_buffer_len,
+ verify_hash,
+ 1 ) ) != 0 )
+ {
+ MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_sha384", ret );
+ MBEDTLS_SSL_PEND_FATAL_ALERT(
+ MBEDTLS_SSL_ALERT_MSG_UNSUPPORTED_CERT,
+ MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
+ return( MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
+ }
+ break;
+#endif /* MBEDTLS_SHA384_C */
+
+#if defined(MBEDTLS_SHA512_C)
+ case MBEDTLS_MD_SHA512:
+ verify_hash_len = 64;
+ if( ( ret = mbedtls_sha512( verify_buffer,
+ verify_buffer_len,
+ verify_hash,
+ 0 ) ) != 0 )
+ {
+ MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_sha512", ret );
+ MBEDTLS_SSL_PEND_FATAL_ALERT(
+ MBEDTLS_SSL_ALERT_MSG_UNSUPPORTED_CERT,
+ MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
+ return( MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
+ }
+ break;
+#endif /* MBEDTLS_SHA512_C */
+
+ default:
+ MBEDTLS_SSL_DEBUG_MSG( 1, ( "Certificate Verify: Unknown signature algorithm." ) );
+ MBEDTLS_SSL_PEND_FATAL_ALERT(
+ MBEDTLS_SSL_ALERT_MSG_UNSUPPORTED_CERT,
+ MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
+ return( MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
+ }
+
+ MBEDTLS_SSL_DEBUG_BUF( 3, "verify hash", verify_hash, verify_hash_len );
+
+ if( ( ret = mbedtls_pk_verify_ext( sig_alg, NULL,
+ &ssl->session_negotiate->peer_cert->pk,
+ md_alg, verify_hash, verify_hash_len,
+ buf, signature_len ) ) != 0 )
+ {
+ MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_pk_verify_ext", ret );
+
+ /* RFC 8446 section 4.4.3
+ *
+ * If the verification fails, the receiver MUST terminate the handshake
+ * with a "decrypt_error" alert.
+ */
+ MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_DECRYPT_ERROR, ret );
+
+ return( ret );
+ }
+
+ return( ret );
+}
+#endif /* MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED */
+
+int mbedtls_ssl_tls13_process_certificate_verify( mbedtls_ssl_context *ssl )
+{
+ int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+
+ /* Coordination step */
+ MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> parse certificate verify" ) );
+
+ MBEDTLS_SSL_PROC_CHK_NEG( ssl_tls13_process_certificate_verify_coordinate( ssl ) );
+
+#if defined(MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED) // TBD: double-check
+ if( ret == SSL_CERTIFICATE_VERIFY_READ )
+ {
+ unsigned char verify_buffer[SSL_VERIFY_STRUCT_MAX_SIZE];
+ size_t verify_buffer_len;
+ unsigned char transcript[MBEDTLS_TLS1_3_MD_MAX_SIZE];
+ size_t transcript_len;
+ unsigned char *buf;
+ size_t buf_len;
+
+ /* Need to calculate the hash of the transcript first
+ * before reading the message since otherwise it gets
+ * included in the transcript
+ */
+ ret = mbedtls_ssl_get_handshake_transcript( ssl,
+ ssl->handshake->ciphersuite_info->mac,
+ transcript, sizeof( transcript ),
+ &transcript_len );
+ if( ret != 0 )
+ {
+ MBEDTLS_SSL_PEND_FATAL_ALERT(
+ MBEDTLS_SSL_ALERT_MSG_INTERNAL_ERROR,
+ MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+ return( ret );
+ }
+
+ MBEDTLS_SSL_DEBUG_BUF( 3, "handshake hash", transcript, transcript_len );
+
+ /* Create verify structure */
+ ssl_tls13_create_verify_structure( transcript,
+ transcript_len,
+ verify_buffer,
+ &verify_buffer_len,
+ !ssl->conf->endpoint );
+
+ MBEDTLS_SSL_PROC_CHK(
+ mbedtls_ssl_tls1_3_fetch_handshake_msg( ssl,
+ MBEDTLS_SSL_HS_CERTIFICATE_VERIFY, &buf, &buf_len ) );
+
+ /* Process the message contents */
+ MBEDTLS_SSL_PROC_CHK(
+ ssl_tls13_process_certificate_verify_parse( ssl,
+ buf, buf + buf_len, verify_buffer, verify_buffer_len ) );
+
+ mbedtls_ssl_tls1_3_add_hs_msg_to_checksum( ssl,
+ MBEDTLS_SSL_HS_CERTIFICATE_VERIFY, buf, buf_len );
+ }
+ else
+#endif /* MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED */
+ if( ret == SSL_CERTIFICATE_VERIFY_SKIP )
+ {
+ MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= skip parse certificate verify" ) );
+ }
+ else
+ {
+ MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
+ return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+ }
+
+
+cleanup:
+
+ MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= parse certificate verify" ) );
+ return( ret );
+}
+
/*
*
* STATE HANDLING: Incoming Certificate, client-side only currently.