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Refactor cookie to prepare for external callbacks

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Also adds flexibility to the verification process.
This commit is contained in:
Manuel Pégourié-Gonnard 2014-07-23 11:09:27 +02:00 committed by Paul Bakker
parent 82202f0a9c
commit d7f9bc5091
2 changed files with 63 additions and 50 deletions
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6
include/polarssl/ssl.h
View File

@ -620,8 +620,10 @@ struct _ssl_handshake_params
#endif /* POLARSSL_X509_CRT_PARSE_C */ #endif /* POLARSSL_X509_CRT_PARSE_C */
#if defined(POLARSSL_SSL_PROTO_DTLS) #if defined(POLARSSL_SSL_PROTO_DTLS)
unsigned int msg_seq; /*!< DTLS handshake sequence number */ unsigned int msg_seq; /*!< DTLS handshake sequence number */
unsigned char *verify_cookie; /*!< cookie from HelloVerifyRequest */ unsigned char *verify_cookie; /*!< Cli: HelloVerifyRequest cookie
unsigned char verify_cookie_len; /*!< cookie length */ Srv: unused */
unsigned char verify_cookie_len; /*!< Cli: cookie length
Srv: flag for sending a cookie */
#endif #endif
/* /*

107
library/ssl_srv.c
View File

@ -1186,36 +1186,51 @@ int ssl_setup_hvr_key( ssl_context *ssl )
/* /*
* Generate cookie for DTLS ClientHello verification * Generate cookie for DTLS ClientHello verification
*/ */
static int ssl_cookie_generate( ssl_context *ssl ) static int ssl_cookie_write( void *ctx,
unsigned char **p, unsigned char *end,
const unsigned char *cli_id, size_t cli_id_len )
{ {
int ret; int ret;
unsigned char *cookie = ssl->handshake->verify_cookie;
unsigned char cookie_len;
unsigned char hmac_out[HVR_MD_LEN]; unsigned char hmac_out[HVR_MD_LEN];
md_context_t *hmac_ctx = (md_context_t *) ctx;
polarssl_free( cookie ); if( (size_t)( end - *p ) < HVR_MD_USE )
return( POLARSSL_ERR_SSL_BAD_INPUT_DATA );
cookie_len = HVR_MD_LEN; if( ( ret = md_hmac_reset( hmac_ctx ) ) != 0 ||
( ret = md_hmac_update( hmac_ctx, cli_id, cli_id_len ) ) != 0 ||
if( ( cookie = polarssl_malloc( cookie_len ) ) == NULL ) ( ret = md_hmac_finish( hmac_ctx, hmac_out ) ) != 0 )
{ {
SSL_DEBUG_MSG( 1, ( "malloc (%d bytes) failed\n", cookie_len ) );
return( POLARSSL_ERR_SSL_MALLOC_FAILED );
}
if( ( ret = md_hmac_reset( &ssl->hvr_hmac_ctx ) ) != 0 ||
( ret = md_hmac_update( &ssl->hvr_hmac_ctx,
ssl->cli_id, ssl->cli_id_len ) ) != 0 ||
( ret = md_hmac_finish( &ssl->hvr_hmac_ctx, hmac_out ) ) != 0 )
{
SSL_DEBUG_RET( 1, "md_hmac", ret );
return( POLARSSL_ERR_SSL_INTERNAL_ERROR ); return( POLARSSL_ERR_SSL_INTERNAL_ERROR );
} }
memcpy( cookie, hmac_out, HVR_MD_USE ); memcpy( *p, hmac_out, HVR_MD_USE );
*p += HVR_MD_USE;
ssl->handshake->verify_cookie = cookie; return( 0 );
ssl->handshake->verify_cookie_len = cookie_len; }
/*
* Check a cookie
*/
static int ssl_cookie_check( void *ctx,
const unsigned char *cookie, size_t cookie_len,
const unsigned char *cli_id, size_t cli_id_len )
{
unsigned char ref_cookie[HVR_MD_USE];
unsigned char *p = ref_cookie;
md_context_t *hmac_ctx = (md_context_t *) ctx;
if( cookie_len != HVR_MD_USE )
return( -1 );
if( ssl_cookie_write( hmac_ctx,
&p, p + sizeof( ref_cookie ),
cli_id, cli_id_len ) != 0 )
return( -1 );
if( safer_memcmp( cookie, ref_cookie, sizeof( ref_cookie ) ) != 0 )
return( -1 );
return( 0 ); return( 0 );
} }
@ -1516,31 +1531,18 @@ static int ssl_parse_client_hello( ssl_context *ssl )
buf + cookie_offset + 1, cookie_len ); buf + cookie_offset + 1, cookie_len );
#if defined(POLARSSL_SSL_DTLS_HELLO_VERIFY) #if defined(POLARSSL_SSL_DTLS_HELLO_VERIFY)
/* if( ssl_cookie_check( &ssl->hvr_hmac_ctx,
* Generate reference cookie content: buf + cookie_offset + 1, cookie_len,
* - used for verification below, ssl->cli_id, ssl->cli_id_len ) != 0 )
* - stored to be sent if verification fails
*/
if( ( ret = ssl_cookie_generate( ssl ) ) != 0 )
{ {
SSL_DEBUG_RET( 1, "ssl_cookie_generate", ret ); SSL_DEBUG_MSG( 2, ( "client hello, cookie verification failed" ) );
return( ret ); ssl->handshake->verify_cookie_len = 1;
} }
else
/* If the received cookie is OK, no need to send one */
if( cookie_len == ssl->handshake->verify_cookie_len &&
safer_memcmp( buf + cookie_offset + 1,
ssl->handshake->verify_cookie,
ssl->handshake->verify_cookie_len ) == 0 )
{ {
polarssl_free( ssl->handshake->verify_cookie ); SSL_DEBUG_MSG( 2, ( "client hello, cookie verification passed" ) );
ssl->handshake->verify_cookie = NULL;
ssl->handshake->verify_cookie_len = 0; ssl->handshake->verify_cookie_len = 0;
} }
SSL_DEBUG_MSG( 2, ( "client hello, cookie verification %s",
ssl->handshake->verify_cookie == NULL ?
"passed" : "failed" ) );
#else #else
/* We know we didn't send a cookie, so it should be empty */ /* We know we didn't send a cookie, so it should be empty */
if( cookie_len != 0 ) if( cookie_len != 0 )
@ -1549,7 +1551,7 @@ static int ssl_parse_client_hello( ssl_context *ssl )
return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO ); return( POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO );
} }
SSL_DEBUG_MSG( 2, ( "cookie verification disabled" ) ); SSL_DEBUG_MSG( 2, ( "client hello, cookie verification skipped" ) );
#endif #endif
} }
#endif /* POLARSSL_SSL_PROTO_DTLS */ #endif /* POLARSSL_SSL_PROTO_DTLS */
@ -2053,6 +2055,7 @@ static int ssl_write_hello_verify_request( ssl_context *ssl )
{ {
int ret; int ret;
unsigned char *p = ssl->out_msg + 4; unsigned char *p = ssl->out_msg + 4;
unsigned char *cookie_len_byte;
SSL_DEBUG_MSG( 2, ( "=> write hello verify request" ) ); SSL_DEBUG_MSG( 2, ( "=> write hello verify request" ) );
@ -2069,12 +2072,20 @@ static int ssl_write_hello_verify_request( ssl_context *ssl )
SSL_DEBUG_BUF( 3, "server version", (unsigned char *) p, 2 ); SSL_DEBUG_BUF( 3, "server version", (unsigned char *) p, 2 );
p += 2; p += 2;
SSL_DEBUG_BUF( 3, "cookie", ssl->handshake->verify_cookie, /* Skip length byte until we know the length */
ssl->handshake->verify_cookie_len ); cookie_len_byte = p++;
*p++ = ssl->handshake->verify_cookie_len;
memcpy( p, ssl->handshake->verify_cookie, if( ( ret = ssl_cookie_write( &ssl->hvr_hmac_ctx,
ssl->handshake->verify_cookie_len ); &p, ssl->out_buf + SSL_BUFFER_LEN,
p += ssl->handshake->verify_cookie_len; ssl->cli_id, ssl->cli_id_len ) ) != 0 )
{
SSL_DEBUG_RET( 1, "ssl_cookie_generate", ret );
return( ret );
}
*cookie_len_byte = (unsigned char)( p - ( cookie_len_byte + 1 ) );
SSL_DEBUG_BUF( 3, "cookie sent", cookie_len_byte + 1, *cookie_len_byte );
ssl->out_msglen = p - ssl->out_msg; ssl->out_msglen = p - ssl->out_msg;
ssl->out_msgtype = SSL_MSG_HANDSHAKE; ssl->out_msgtype = SSL_MSG_HANDSHAKE;
@ -2107,7 +2118,7 @@ static int ssl_write_server_hello( ssl_context *ssl )
#if defined(POLARSSL_SSL_DTLS_HELLO_VERIFY) #if defined(POLARSSL_SSL_DTLS_HELLO_VERIFY)
if( ssl->transport == SSL_TRANSPORT_DATAGRAM && if( ssl->transport == SSL_TRANSPORT_DATAGRAM &&
ssl->handshake->verify_cookie != NULL ) ssl->handshake->verify_cookie_len != 0 )
{ {
SSL_DEBUG_MSG( 2, ( "client hello was not authenticated" ) ); SSL_DEBUG_MSG( 2, ( "client hello was not authenticated" ) );
SSL_DEBUG_MSG( 2, ( "<= write server hello" ) ); SSL_DEBUG_MSG( 2, ( "<= write server hello" ) );