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Refactor for clearer correctness/security

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Manuel Pégourié-Gonnard 2015-01-13 10:59:51 +01:00
parent 8e4b3374d7
commit 352143fa1e
1 changed files with 56 additions and 56 deletions
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112
library/ssl_tls.c
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@ -1071,71 +1071,41 @@ static void ssl_mac( md_context_t *md_ctx, unsigned char *secret,
} }
#endif /* POLARSSL_SSL_PROTO_SSL3 */ #endif /* POLARSSL_SSL_PROTO_SSL3 */
#define MAC_NONE 0
#define MAC_PLAINTEXT 1
#define MAC_CIPHERTEXT 2
#if defined(POLARSSL_ARC4_C) || defined(POLARSSL_CIPHER_NULL_CIPHER) || \ #if defined(POLARSSL_ARC4_C) || defined(POLARSSL_CIPHER_NULL_CIPHER) || \
( defined(POLARSSL_CIPHER_MODE_CBC) && \ ( defined(POLARSSL_CIPHER_MODE_CBC) && \
( defined(POLARSSL_AES_C) || defined(POLARSSL_CAMELLIA_C) ) ) ( defined(POLARSSL_AES_C) || defined(POLARSSL_CAMELLIA_C) ) )
#define POLARSSL_SOME_MODES_USE_MAC #define POLARSSL_SOME_MODES_USE_MAC
#endif #endif
/*
* Is MAC applied on ciphertext, cleartext or not at all?
*/
#if defined(POLARSSL_SOME_MODES_USE_MAC)
static char ssl_get_mac_order( ssl_context *ssl,
const ssl_session *session,
cipher_mode_t mode )
{
#if defined(POLARSSL_ARC4_C) || defined(POLARSSL_CIPHER_NULL_CIPHER)
if( mode == POLARSSL_MODE_STREAM )
return( MAC_PLAINTEXT );
#endif
#if defined(POLARSSL_CIPHER_MODE_CBC) && \
( defined(POLARSSL_AES_C) || defined(POLARSSL_CAMELLIA_C) )
if( mode == POLARSSL_MODE_CBC )
{
#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC)
if( session != NULL && session->encrypt_then_mac == SSL_ETM_ENABLED )
{
SSL_DEBUG_MSG( 3, ( "using encrypt then mac" ) );
return( MAC_CIPHERTEXT );
}
#else
((void) ssl);
((void) session);
#endif
return( MAC_PLAINTEXT );
}
#else
((void) ssl);
((void) session);
#endif
return( MAC_NONE );
}
#endif /* POLARSSL_SOME_MODES_USE_MAC */
/* /*
* Encryption/decryption functions * Encryption/decryption functions
*/ */
static int ssl_encrypt_buf( ssl_context *ssl ) static int ssl_encrypt_buf( ssl_context *ssl )
{ {
size_t i; size_t i;
const cipher_mode_t mode = cipher_get_cipher_mode( cipher_mode_t mode;
&ssl->transform_out->cipher_ctx_enc ); int auth_done = 0;
SSL_DEBUG_MSG( 2, ( "=> encrypt buf" ) ); SSL_DEBUG_MSG( 2, ( "=> encrypt buf" ) );
if( ssl->session_out == NULL || ssl->transform_out == NULL )
{
SSL_DEBUG_MSG( 1, ( "should never happen" ) );
return( POLARSSL_ERR_SSL_INTERNAL_ERROR );
}
mode = cipher_get_cipher_mode( &ssl->transform_out->cipher_ctx_enc );
/* /*
* Add MAC before if needed * Add MAC before if needed
*/ */
#if defined(POLARSSL_SOME_MODES_USE_MAC) #if defined(POLARSSL_SOME_MODES_USE_MAC)
if( ssl_get_mac_order( ssl, ssl->session_out, mode ) == MAC_PLAINTEXT ) if( mode == POLARSSL_MODE_STREAM ||
( mode == POLARSSL_MODE_CBC
#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC)
&& ssl->session_out->encrypt_then_mac == SSL_ETM_DISABLED
#endif
) )
{ {
#if defined(POLARSSL_SSL_PROTO_SSL3) #if defined(POLARSSL_SSL_PROTO_SSL3)
if( ssl->minor_ver == SSL_MINOR_VERSION_0 ) if( ssl->minor_ver == SSL_MINOR_VERSION_0 )
@ -1170,6 +1140,7 @@ static int ssl_encrypt_buf( ssl_context *ssl )
ssl->transform_out->maclen ); ssl->transform_out->maclen );
ssl->out_msglen += ssl->transform_out->maclen; ssl->out_msglen += ssl->transform_out->maclen;
auth_done++;
} }
#endif /* AEAD not the only option */ #endif /* AEAD not the only option */
@ -1281,6 +1252,7 @@ static int ssl_encrypt_buf( ssl_context *ssl )
} }
ssl->out_msglen += taglen; ssl->out_msglen += taglen;
auth_done++;
SSL_DEBUG_BUF( 4, "after encrypt: tag", enc_msg + enc_msglen, taglen ); SSL_DEBUG_BUF( 4, "after encrypt: tag", enc_msg + enc_msglen, taglen );
} }
@ -1371,7 +1343,7 @@ static int ssl_encrypt_buf( ssl_context *ssl )
#endif #endif
#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC) #if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC)
if( ssl_get_mac_order( ssl, ssl->session_out, mode ) == MAC_CIPHERTEXT ) if( auth_done == 0 )
{ {
/* /*
* MAC(MAC_write_key, seq_num + * MAC(MAC_write_key, seq_num +
@ -1383,6 +1355,8 @@ static int ssl_encrypt_buf( ssl_context *ssl )
*/ */
unsigned char pseudo_hdr[13]; unsigned char pseudo_hdr[13];
SSL_DEBUG_MSG( 3, ( "using encrypt then mac" ) );
memcpy( pseudo_hdr + 0, ssl->out_ctr, 8 ); memcpy( pseudo_hdr + 0, ssl->out_ctr, 8 );
memcpy( pseudo_hdr + 8, ssl->out_hdr, 3 ); memcpy( pseudo_hdr + 8, ssl->out_hdr, 3 );
pseudo_hdr[11] = (unsigned char)( ( ssl->out_msglen >> 8 ) & 0xFF ); pseudo_hdr[11] = (unsigned char)( ( ssl->out_msglen >> 8 ) & 0xFF );
@ -1398,6 +1372,7 @@ static int ssl_encrypt_buf( ssl_context *ssl )
md_hmac_reset( &ssl->transform_out->md_ctx_enc ); md_hmac_reset( &ssl->transform_out->md_ctx_enc );
ssl->out_msglen += ssl->transform_out->maclen; ssl->out_msglen += ssl->transform_out->maclen;
auth_done++;
} }
#endif /* POLARSSL_SSL_ENCRYPT_THEN_MAC */ #endif /* POLARSSL_SSL_ENCRYPT_THEN_MAC */
} }
@ -1409,6 +1384,13 @@ static int ssl_encrypt_buf( ssl_context *ssl )
return( POLARSSL_ERR_SSL_INTERNAL_ERROR ); return( POLARSSL_ERR_SSL_INTERNAL_ERROR );
} }
/* Make extra sure authentication was performed, exactly once */
if( auth_done != 1 )
{
SSL_DEBUG_MSG( 1, ( "should never happen" ) );
return( POLARSSL_ERR_SSL_INTERNAL_ERROR );
}
for( i = 8; i > 0; i-- ) for( i = 8; i > 0; i-- )
if( ++ssl->out_ctr[i - 1] != 0 ) if( ++ssl->out_ctr[i - 1] != 0 )
break; break;
@ -1430,14 +1412,22 @@ static int ssl_encrypt_buf( ssl_context *ssl )
static int ssl_decrypt_buf( ssl_context *ssl ) static int ssl_decrypt_buf( ssl_context *ssl )
{ {
size_t i; size_t i;
const cipher_mode_t mode = cipher_get_cipher_mode( cipher_mode_t mode;
&ssl->transform_in->cipher_ctx_dec ); int auth_done = 0;
#if defined(POLARSSL_SOME_MODES_USE_MAC) #if defined(POLARSSL_SOME_MODES_USE_MAC)
size_t padlen = 0, correct = 1; size_t padlen = 0, correct = 1;
#endif #endif
SSL_DEBUG_MSG( 2, ( "=> decrypt buf" ) ); SSL_DEBUG_MSG( 2, ( "=> decrypt buf" ) );
if( ssl->session_in == NULL || ssl->transform_in == NULL )
{
SSL_DEBUG_MSG( 1, ( "should never happen" ) );
return( POLARSSL_ERR_SSL_INTERNAL_ERROR );
}
mode = cipher_get_cipher_mode( &ssl->transform_in->cipher_ctx_dec );
if( ssl->in_msglen < ssl->transform_in->minlen ) if( ssl->in_msglen < ssl->transform_in->minlen )
{ {
SSL_DEBUG_MSG( 1, ( "in_msglen (%d) < minlen (%d)", SSL_DEBUG_MSG( 1, ( "in_msglen (%d) < minlen (%d)",
@ -1534,6 +1524,7 @@ static int ssl_decrypt_buf( ssl_context *ssl )
return( ret ); return( ret );
} }
auth_done++;
if( olen != dec_msglen ) if( olen != dec_msglen )
{ {
@ -1583,11 +1574,13 @@ static int ssl_decrypt_buf( ssl_context *ssl )
* Authenticate before decrypt if enabled * Authenticate before decrypt if enabled
*/ */
#if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC) #if defined(POLARSSL_SSL_ENCRYPT_THEN_MAC)
if( ssl_get_mac_order( ssl, ssl->session_in, mode ) == MAC_CIPHERTEXT ) if( ssl->session_in->encrypt_then_mac == SSL_ETM_ENABLED )
{ {
unsigned char computed_mac[POLARSSL_SSL_MAX_MAC_SIZE]; unsigned char computed_mac[POLARSSL_SSL_MAX_MAC_SIZE];
unsigned char pseudo_hdr[13]; unsigned char pseudo_hdr[13];
SSL_DEBUG_MSG( 3, ( "using encrypt then mac" ) );
dec_msglen -= ssl->transform_in->maclen; dec_msglen -= ssl->transform_in->maclen;
ssl->in_msglen -= ssl->transform_in->maclen; ssl->in_msglen -= ssl->transform_in->maclen;
@ -1616,6 +1609,7 @@ static int ssl_decrypt_buf( ssl_context *ssl )
return( POLARSSL_ERR_SSL_INVALID_MAC ); return( POLARSSL_ERR_SSL_INVALID_MAC );
} }
auth_done++;
} }
#endif /* POLARSSL_SSL_ENCRYPT_THEN_MAC */ #endif /* POLARSSL_SSL_ENCRYPT_THEN_MAC */
@ -1674,7 +1668,7 @@ static int ssl_decrypt_buf( ssl_context *ssl )
padlen = 1 + ssl->in_msg[ssl->in_msglen - 1]; padlen = 1 + ssl->in_msg[ssl->in_msglen - 1];
if( ssl->in_msglen < ssl->transform_in->maclen + padlen && if( ssl->in_msglen < ssl->transform_in->maclen + padlen &&
ssl_get_mac_order( ssl, ssl->session_in, mode ) == MAC_PLAINTEXT ) auth_done == 0 )
{ {
#if defined(POLARSSL_SSL_DEBUG_ALL) #if defined(POLARSSL_SSL_DEBUG_ALL)
SSL_DEBUG_MSG( 1, ( "msglen (%d) < maclen (%d) + padlen (%d)", SSL_DEBUG_MSG( 1, ( "msglen (%d) < maclen (%d) + padlen (%d)",
@ -1766,10 +1760,8 @@ static int ssl_decrypt_buf( ssl_context *ssl )
* Authenticate if not done yet. * Authenticate if not done yet.
* Compute the MAC regardless of the padding result (RFC4346, CBCTIME). * Compute the MAC regardless of the padding result (RFC4346, CBCTIME).
*/ */
#if defined(POLARSSL_ARC4_C) || defined(POLARSSL_CIPHER_NULL_CIPHER) || \ #if defined(POLARSSL_SOME_MODES_USE_MAC)
( defined(POLARSSL_CIPHER_MODE_CBC) && \ if( auth_done == 0 )
( defined(POLARSSL_AES_C) || defined(POLARSSL_CAMELLIA_C) ) )
if( ssl_get_mac_order( ssl, ssl->session_in, mode ) == MAC_PLAINTEXT )
{ {
unsigned char tmp[POLARSSL_SSL_MAX_MAC_SIZE]; unsigned char tmp[POLARSSL_SSL_MAX_MAC_SIZE];
@ -1843,6 +1835,7 @@ static int ssl_decrypt_buf( ssl_context *ssl )
#endif #endif
correct = 0; correct = 0;
} }
auth_done++;
/* /*
* Finally check the correct flag * Finally check the correct flag
@ -1850,7 +1843,14 @@ static int ssl_decrypt_buf( ssl_context *ssl )
if( correct == 0 ) if( correct == 0 )
return( POLARSSL_ERR_SSL_INVALID_MAC ); return( POLARSSL_ERR_SSL_INVALID_MAC );
} }
#endif /* AEAD not the only option */ #endif /* POLARSSL_SOME_MODES_USE_MAC */
/* Make extra sure authentication was performed, exactly once */
if( auth_done != 1 )
{
SSL_DEBUG_MSG( 1, ( "should never happen" ) );
return( POLARSSL_ERR_SSL_INTERNAL_ERROR );
}
if( ssl->in_msglen == 0 ) if( ssl->in_msglen == 0 )
{ {