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ssl_tls13_client.c: alpn: Loop only once over protocol names

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This has although the benefit of getting rid of a
potential integer overflow (though very unlikely
and probably harmless).

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
This commit is contained in:
Ronald Cron
2022-03-09 10:48:18 +01:00
parent a0855a6d13
commit 13d8ea1dd9
1 changed files with 12 additions and 13 deletions
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25
library/ssl_tls13_client.c
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@ -128,7 +128,7 @@ static int ssl_tls13_write_alpn_ext( mbedtls_ssl_context *ssl,
size_t *olen ) size_t *olen )
{ {
unsigned char *p = buf; unsigned char *p = buf;
size_t alpnlen = 0; size_t protocol_name_len;
const char **cur; const char **cur;
*olen = 0; *olen = 0;
@ -138,13 +138,14 @@ static int ssl_tls13_write_alpn_ext( mbedtls_ssl_context *ssl,
MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, adding alpn extension" ) ); MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, adding alpn extension" ) );
for( cur = ssl->conf->alpn_list; *cur != NULL; cur++ )
alpnlen += strlen( *cur ) + 1;
MBEDTLS_SSL_CHK_BUF_PTR( p, end, 6 + alpnlen );
/* Check we have enough space for the extension type (2 bytes), the
* extension length (2 bytes) and the protocol_name_list length (2 bytes).
*/
MBEDTLS_SSL_CHK_BUF_PTR( p, end, 6 );
MBEDTLS_PUT_UINT16_BE( MBEDTLS_TLS_EXT_ALPN, p, 0 ); MBEDTLS_PUT_UINT16_BE( MBEDTLS_TLS_EXT_ALPN, p, 0 );
p += 2; /* Skip writing extension and list length for now */
p += 6;
/* /*
* opaque ProtocolName<1..2^8-1>; * opaque ProtocolName<1..2^8-1>;
@ -153,19 +154,17 @@ static int ssl_tls13_write_alpn_ext( mbedtls_ssl_context *ssl,
* ProtocolName protocol_name_list<2..2^16-1> * ProtocolName protocol_name_list<2..2^16-1>
* } ProtocolNameList; * } ProtocolNameList;
*/ */
/* Skip writing extension and list length for now */
p += 4;
for( cur = ssl->conf->alpn_list; *cur != NULL; cur++ ) for( cur = ssl->conf->alpn_list; *cur != NULL; cur++ )
{ {
/* /*
* mbedtls_ssl_conf_set_alpn_protocols() checked that the length of * mbedtls_ssl_conf_set_alpn_protocols() checked that the length of
* protocol names is less than 255. * protocol names is less than 255.
*/ */
*p = (unsigned char)strlen( *cur ); protocol_name_len = strlen( *cur );
memcpy( p + 1, *cur, *p ); MBEDTLS_SSL_CHK_BUF_PTR( p, end, 1 + protocol_name_len );
p += 1 + *p; *p++ = (unsigned char)protocol_name_len;
memcpy( p, *cur, protocol_name_len );
p += protocol_name_len;
} }
*olen = p - buf; *olen = p - buf;