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add signature algorithms extension

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Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
This commit is contained in:
Jerry Yu 2021-08-31 15:41:21 +08:00
parent 6b64fe31ce
commit 7236994aa9
1 changed files with 53 additions and 4 deletions
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57
library/ssl_tls13_generic.c
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@ -107,11 +107,60 @@ int mbedtls_ssl_tls13_write_sig_alg_ext( mbedtls_ssl_context *ssl,
unsigned char *end,
size_t *olen )
{
((void) ssl);
((void) buf);
((void) end);
unsigned char *p = buf;
unsigned char *sig_alg_ptr; /* Start of supported_signature_algorithms */
size_t sig_alg_len = 0; /* Length of supported_signature_algorithms */
*olen = 0;
MBEDTLS_SSL_DEBUG_MSG( 3, ( "signature_algorithm extension is not available" ) );
/* Skip the extension on the client if all allowed key exchanges
* are PSK-based. */
#if defined(MBEDTLS_SSL_CLI_C)
if( ssl->conf->endpoint == MBEDTLS_SSL_IS_CLIENT &&
!mbedtls_ssl_conf_tls13_some_ephemeral_enabled( ssl ) )
{
return( 0 );
}
#endif /* MBEDTLS_SSL_CLI_C */
MBEDTLS_SSL_DEBUG_MSG( 3, ( "adding signature_algorithms extension" ) );
/* Check there is space for extension header */
MBEDTLS_SSL_CHK_BUF_PTR( p, end, 6 );
p += 6;
/*
* Write supported_signature_algorithms
*/
sig_alg_ptr = p;
for( const uint16_t *sig_alg = ssl->conf->tls13_sig_algs;
*sig_alg != MBEDTLS_TLS13_SIG_NONE; sig_alg++ )
{
MBEDTLS_SSL_CHK_BUF_PTR( p, end, 2 );
MBEDTLS_PUT_UINT16_BE( *sig_alg, p, 0 );
p += 2;
MBEDTLS_SSL_DEBUG_MSG( 3, ( "signature scheme [%x]", *sig_alg ) );
}
/* Length of supported_signature_algorithms*/
sig_alg_len = p - sig_alg_ptr;
if( sig_alg_len == 0 )
{
MBEDTLS_SSL_DEBUG_MSG( 1, ( "No signature algorithms defined." ) );
return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
}
/* Write extension_type */
MBEDTLS_PUT_UINT16_BE( MBEDTLS_TLS_EXT_SIG_ALG, buf, 0 );
/* Write extension_data_length */
MBEDTLS_PUT_UINT16_BE( sig_alg_len + 2, buf, 2 );
/* Write length of supported_signature_algorithms */
MBEDTLS_PUT_UINT16_BE( sig_alg_len, buf, 4 );
/* Output the total length of signature algorithms extension. */
*olen = p - buf;
ssl->handshake->extensions_present |= MBEDTLS_SSL_EXT_SIG_ALG;
return( 0 );
}