lib/mbedtls
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Don't send back EtM extension if not using CBC

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This commit is contained in:
Manuel Pégourié-Gonnard
2014-11-04 15:44:06 +01:00
parent 08558e5b46
commit 78e745fc0a
2 changed files with 41 additions and 0 deletions
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17
library/ssl_srv.c
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@ -1721,6 +1721,8 @@ static void ssl_write_encrypt_then_mac_ext( ssl_context *ssl,
size_t *olen )
{
unsigned char *p = buf;
const ssl_ciphersuite_t *suite = NULL;
const cipher_info_t *cipher = NULL;
if( ssl->session_negotiate->encrypt_then_mac == SSL_EXTENDED_MS_DISABLED ||
ssl->minor_ver == SSL_MINOR_VERSION_0 )
@ -1729,6 +1731,21 @@ static void ssl_write_encrypt_then_mac_ext( ssl_context *ssl,
return;
}
/*
* RFC 7366: "If a server receives an encrypt-then-MAC request extension
* from a client and then selects a stream or Authenticated Encryption
* with Associated Data (AEAD) ciphersuite, it MUST NOT send an
* encrypt-then-MAC response extension back to the client."
*/
if( ( suite = ssl_ciphersuite_from_id(
ssl->session_negotiate->ciphersuite ) ) == NULL ||
( cipher = cipher_info_from_type( suite->cipher ) ) == NULL ||
cipher->mode != POLARSSL_MODE_CBC )
{
*olen = 0;
return;
}
SSL_DEBUG_MSG( 3, ( "server hello, adding encrypt then mac extension" ) );
*p++ = (unsigned char)( ( TLS_EXT_ENCRYPT_THEN_MAC >> 8 ) & 0xFF );