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tls13: Try reasonable sig alg for CertificateVerify signature

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Instead of fully validating beforehand
signature algorithms with regards to the
private key, do minimum validation and then
just try to compute the signature. If it
fails try another reasonable algorithm if any.

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
This commit is contained in:
Ronald Cron 2022-09-16 13:44:49 +02:00
parent 38391bf9b6
commit 067a1e735e
2 changed files with 79 additions and 140 deletions
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191
library/ssl_tls13_generic.c
View file

@ -923,83 +923,13 @@ int mbedtls_ssl_tls13_check_sig_alg_cert_key_match( uint16_t sig_alg,
return( 0 );
}
#if defined(MBEDTLS_USE_PSA_CRYPTO)
static psa_algorithm_t ssl_tls13_select_sig_alg_to_psa_alg( uint16_t sig_alg )
{
switch( sig_alg )
{
case MBEDTLS_TLS1_3_SIG_ECDSA_SECP256R1_SHA256:
return( PSA_ALG_ECDSA( PSA_ALG_SHA_256 ) );
case MBEDTLS_TLS1_3_SIG_ECDSA_SECP384R1_SHA384:
return( PSA_ALG_ECDSA( PSA_ALG_SHA_384 ) );
case MBEDTLS_TLS1_3_SIG_ECDSA_SECP521R1_SHA512:
return( PSA_ALG_ECDSA( PSA_ALG_SHA_512 ) );
case MBEDTLS_TLS1_3_SIG_RSA_PSS_RSAE_SHA256:
return( PSA_ALG_RSA_PSS( PSA_ALG_SHA_256 ) );
case MBEDTLS_TLS1_3_SIG_RSA_PSS_RSAE_SHA384:
return( PSA_ALG_RSA_PSS( PSA_ALG_SHA_384 ) );
case MBEDTLS_TLS1_3_SIG_RSA_PSS_RSAE_SHA512:
return( PSA_ALG_RSA_PSS( PSA_ALG_SHA_512 ) );
case MBEDTLS_TLS1_3_SIG_RSA_PKCS1_SHA256:
case MBEDTLS_TLS1_3_SIG_RSA_PKCS1_SHA384:
case MBEDTLS_TLS1_3_SIG_RSA_PKCS1_SHA512:
return( PSA_ALG_RSA_PKCS1V15_CRYPT );
default:
return( 0 );
}
}
#endif /* MBEDTLS_USE_PSA_CRYPTO */
MBEDTLS_CHECK_RETURN_CRITICAL
static int ssl_tls13_select_sig_alg_for_certificate_verify(
mbedtls_ssl_context *ssl,
mbedtls_pk_context *own_key,
uint16_t *algorithm )
{
uint16_t *sig_alg = ssl->handshake->received_sig_algs;
#if defined(MBEDTLS_USE_PSA_CRYPTO)
psa_algorithm_t psa_alg = 0;
#endif /* MBEDTLS_USE_PSA_CRYPTO */
*algorithm = MBEDTLS_TLS1_3_SIG_NONE;
for( ; *sig_alg != MBEDTLS_TLS1_3_SIG_NONE ; sig_alg++ )
{
#if defined(MBEDTLS_USE_PSA_CRYPTO)
psa_alg = ssl_tls13_select_sig_alg_to_psa_alg( *sig_alg );
#endif /* MBEDTLS_USE_PSA_CRYPTO */
if( mbedtls_ssl_sig_alg_is_offered( ssl, *sig_alg ) &&
mbedtls_ssl_tls13_sig_alg_for_cert_verify_is_supported( *sig_alg ) &&
mbedtls_ssl_tls13_check_sig_alg_cert_key_match( *sig_alg, own_key )
#if defined(MBEDTLS_USE_PSA_CRYPTO)
&& psa_alg != 0 &&
mbedtls_pk_can_do_ext( own_key, psa_alg,
PSA_KEY_USAGE_SIGN_HASH ) == 1
#endif /* MBEDTLS_USE_PSA_CRYPTO */
)
{
MBEDTLS_SSL_DEBUG_MSG( 3,
( "select_sig_alg_for_certificate_verify:"
"selected signature algorithm %s [%04x]",
mbedtls_ssl_sig_alg_to_str( *sig_alg ),
*sig_alg ) );
*algorithm = *sig_alg;
return( 0 );
}
}
MBEDTLS_SSL_DEBUG_MSG( 2,
( "select_sig_alg_for_certificate_verify:"
"no suitable signature algorithm found" ) );
return( -1 );
}
MBEDTLS_CHECK_RETURN_CRITICAL
static int ssl_tls13_write_certificate_verify_body( mbedtls_ssl_context *ssl,
unsigned char *buf,
unsigned char *end,
size_t *out_len )
{
int ret;
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
unsigned char *p = buf;
mbedtls_pk_context *own_key;
@ -1007,14 +937,9 @@ static int ssl_tls13_write_certificate_verify_body( mbedtls_ssl_context *ssl,
size_t handshake_hash_len;
unsigned char verify_buffer[ SSL_VERIFY_STRUCT_MAX_SIZE ];
size_t verify_buffer_len;
mbedtls_pk_type_t pk_type = MBEDTLS_PK_NONE;
mbedtls_md_type_t md_alg = MBEDTLS_MD_NONE;
psa_algorithm_t psa_algorithm = PSA_ALG_NONE;
uint16_t algorithm = MBEDTLS_TLS1_3_SIG_NONE;
uint16_t *sig_alg = ssl->handshake->received_sig_algs;
size_t signature_len = 0;
unsigned char verify_hash[PSA_HASH_MAX_SIZE];
size_t verify_hash_len;
psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
*out_len = 0;
@ -1047,64 +972,78 @@ static int ssl_tls13_write_certificate_verify_body( mbedtls_ssl_context *ssl,
* opaque signature<0..2^16-1>;
* } CertificateVerify;
*/
ret = ssl_tls13_select_sig_alg_for_certificate_verify( ssl, own_key,
&algorithm );
if( ret != 0 )
/* Check there is space for the algorithm identifier (2 bytes) and the
* signature length (2 bytes).
*/
MBEDTLS_SSL_CHK_BUF_PTR( p, end, 4 );
for( ; *sig_alg != MBEDTLS_TLS1_3_SIG_NONE ; sig_alg++ )
{
MBEDTLS_SSL_DEBUG_MSG( 1,
( "signature algorithm not in received or offered list." ) );
psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
mbedtls_pk_type_t pk_type = MBEDTLS_PK_NONE;
mbedtls_md_type_t md_alg = MBEDTLS_MD_NONE;
psa_algorithm_t psa_algorithm = PSA_ALG_NONE;
unsigned char verify_hash[PSA_HASH_MAX_SIZE];
size_t verify_hash_len;
MBEDTLS_SSL_DEBUG_MSG( 1, ( "Signature algorithm is %s",
mbedtls_ssl_sig_alg_to_str( algorithm ) ) );
if( !mbedtls_ssl_sig_alg_is_offered( ssl, *sig_alg ) )
continue;
if( !mbedtls_ssl_tls13_sig_alg_for_cert_verify_is_supported( *sig_alg ) )
continue;
if( !mbedtls_ssl_tls13_check_sig_alg_cert_key_match( *sig_alg, own_key ) )
continue;
if( mbedtls_ssl_get_pk_type_and_md_alg_from_sig_alg(
*sig_alg, &pk_type, &md_alg ) != 0 )
{
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
}
/* Hash verify buffer with indicated hash function */
psa_algorithm = mbedtls_hash_info_psa_from_md( md_alg );
status = psa_hash_compute( psa_algorithm,
verify_buffer,
verify_buffer_len,
verify_hash, sizeof( verify_hash ),
&verify_hash_len );
if( status != PSA_SUCCESS )
return( psa_ssl_status_to_mbedtls( status ) );
MBEDTLS_SSL_DEBUG_BUF( 3, "verify hash", verify_hash, verify_hash_len );
if( ( ret = mbedtls_pk_sign_ext( pk_type, own_key,
md_alg, verify_hash, verify_hash_len,
p + 4, (size_t)( end - ( p + 4 ) ), &signature_len,
ssl->conf->f_rng, ssl->conf->p_rng ) ) != 0 )
{
MBEDTLS_SSL_DEBUG_MSG( 2, ( "CertificateVerify signature failed with %s",
mbedtls_ssl_sig_alg_to_str( *sig_alg ) ) );
MBEDTLS_SSL_DEBUG_RET( 2, "mbedtls_pk_sign_ext", ret );
continue;
}
MBEDTLS_SSL_DEBUG_MSG( 2, ( "CertificateVerify signature with %s",
mbedtls_ssl_sig_alg_to_str( *sig_alg ) ) );
break;
}
if( *sig_alg == MBEDTLS_TLS1_3_SIG_NONE )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "no suitable signature algorithm" ) );
MBEDTLS_SSL_PEND_FATAL_ALERT( MBEDTLS_SSL_ALERT_MSG_HANDSHAKE_FAILURE,
MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
return( MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE );
}
MBEDTLS_SSL_DEBUG_MSG( 2, ( "CertificateVerify with %s",
mbedtls_ssl_sig_alg_to_str( algorithm )) );
MBEDTLS_PUT_UINT16_BE( *sig_alg, p, 0 );
MBEDTLS_PUT_UINT16_BE( signature_len, p, 2 );
if( mbedtls_ssl_get_pk_type_and_md_alg_from_sig_alg(
algorithm, &pk_type, &md_alg ) != 0 )
{
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
}
*out_len = 4 + signature_len;
/* Check there is space for the algorithm identifier (2 bytes) and the
* signature length (2 bytes).
*/
MBEDTLS_SSL_CHK_BUF_PTR( p, end, 4 );
MBEDTLS_PUT_UINT16_BE( algorithm, p, 0 );
p += 2;
/* Hash verify buffer with indicated hash function */
psa_algorithm = mbedtls_hash_info_psa_from_md( md_alg );
status = psa_hash_compute( psa_algorithm,
verify_buffer,
verify_buffer_len,
verify_hash,sizeof( verify_hash ),
&verify_hash_len );
if( status != PSA_SUCCESS )
return( psa_ssl_status_to_mbedtls( status ) );
MBEDTLS_SSL_DEBUG_BUF( 3, "verify hash", verify_hash, verify_hash_len );
if( ( ret = mbedtls_pk_sign_ext( pk_type, own_key,
md_alg, verify_hash, verify_hash_len,
p + 2, (size_t)( end - ( p + 2 ) ), &signature_len,
ssl->conf->f_rng, ssl->conf->p_rng ) ) != 0 )
{
MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_pk_sign", ret );
return( ret );
}
MBEDTLS_PUT_UINT16_BE( signature_len, p, 0 );
p += 2 + signature_len;
*out_len = (size_t)( p - buf );
return( ret );
return( 0 );
}
int mbedtls_ssl_tls13_write_certificate_verify( mbedtls_ssl_context *ssl )