Support TLS_FALLBACK_SCSV.

[openssl.git] / ssl / ssl_lib.c

diff --git a/ssl/ssl_lib.c b/ssl/ssl_lib.c
index f779ce66d715dcd8c7e9bcd2dd8524770194130a..27819b452f52f58e44c08c74f6489be019503d0d 100644 (file)
--- a/ssl/ssl_lib.c
+++ b/ssl/ssl_lib.c
@@ -1464,12 +1464,14 @@ int ssl_cipher_list_to_bytes(SSL *s,STACK_OF(SSL_CIPHER) *sk,unsigned char *p,
        SSL_CIPHER *c;
        CERT *ct = s->cert;
        unsigned char *q;
-       int no_scsv = s->renegotiate;
+       int empty_reneg_info_scsv = !s->renegotiate;
        /* Set disabled masks for this session */
        ssl_set_client_disabled(s);
 
        if (sk == NULL) return(0);
        q=p;
+       if (put_cb == NULL)
+               put_cb = s->method->put_cipher_by_char;
 
        for (i=0; i<sk_SSL_CIPHER_num(sk); i++)
                {
@@ -1482,29 +1484,40 @@ int ssl_cipher_list_to_bytes(SSL *s,STACK_OF(SSL_CIPHER) *sk,unsigned char *p,
 #ifdef OPENSSL_SSL_DEBUG_BROKEN_PROTOCOL
                if (c->id == SSL3_CK_SCSV)
                        {
-                       if (no_scsv)
+                       if (!empty_reneg_info_scsv)
                                continue;
                        else
-                               no_scsv = 1;
+                               empty_reneg_info_scsv = 0;
                        }
 #endif
-               j = put_cb ? put_cb(c,p) : ssl_put_cipher_by_char(s,c,p);
+               j = put_cb(c,p);
                p+=j;
                }
-       /* If p == q, no ciphers and caller indicates an error. Otherwise
-        * add SCSV if not renegotiating.
-        */
-       if (p != q && !no_scsv)
+       /* If p == q, no ciphers; caller indicates an error.
+        * Otherwise, add applicable SCSVs. */
+       if (p != q)
                {
-               static SSL_CIPHER scsv =
+               if (empty_reneg_info_scsv)
                        {
-                       0, NULL, SSL3_CK_SCSV, 0, 0, 0, 0, 0, 0, 0, 0, 0
-                       };
-               j = put_cb ? put_cb(&scsv,p) : ssl_put_cipher_by_char(s,&scsv,p);
-               p+=j;
+                       static SSL_CIPHER scsv =
+                               {
+                               0, NULL, SSL3_CK_SCSV, 0, 0, 0, 0, 0, 0, 0, 0, 0
+                               };
+                       j = put_cb(&scsv,p);
+                       p+=j;
 #ifdef OPENSSL_RI_DEBUG
-               fprintf(stderr, "SCSV sent by client\n");
+                       fprintf(stderr, "TLS_EMPTY_RENEGOTIATION_INFO_SCSV sent by client\n");
 #endif
+                       }
+               if (s->mode & SSL_MODE_SEND_FALLBACK_SCSV)
+                       {
+                       static SSL_CIPHER scsv =
+                               {
+                               0, NULL, SSL3_CK_FALLBACK_SCSV, 0, 0, 0, 0, 0, 0, 0, 0, 0
+                               };
+                       j = put_cb(&scsv,p);
+                       p+=j;
+                       }
                }
 
        return(p-q);
@@ -1516,11 +1529,12 @@ STACK_OF(SSL_CIPHER) *ssl_bytes_to_cipher_list(SSL *s,unsigned char *p,int num,
        const SSL_CIPHER *c;
        STACK_OF(SSL_CIPHER) *sk;
        int i,n;
+
        if (s->s3)
                s->s3->send_connection_binding = 0;
 
        n=ssl_put_cipher_by_char(s,NULL,NULL);
-       if ((num%n) != 0)
+       if (n == 0 || (num%n) != 0)
                {
                SSLerr(SSL_F_SSL_BYTES_TO_CIPHER_LIST,SSL_R_ERROR_IN_RECEIVED_CIPHER_LIST);
                return(NULL);
@@ -1545,7 +1559,7 @@ STACK_OF(SSL_CIPHER) *ssl_bytes_to_cipher_list(SSL *s,unsigned char *p,int num,
 
        for (i=0; i<num; i+=n)
                {
-               /* Check for SCSV */
+               /* Check for TLS_EMPTY_RENEGOTIATION_INFO_SCSV */
                if (s->s3 && (n != 3 || !p[0]) &&
                        (p[n-2] == ((SSL3_CK_SCSV >> 8) & 0xff)) &&
                        (p[n-1] == (SSL3_CK_SCSV & 0xff)))
@@ -1565,6 +1579,23 @@ STACK_OF(SSL_CIPHER) *ssl_bytes_to_cipher_list(SSL *s,unsigned char *p,int num,
                        continue;
                        }
 
+               /* Check for TLS_FALLBACK_SCSV */
+               if ((n != 3 || !p[0]) &&
+                       (p[n-2] == ((SSL3_CK_FALLBACK_SCSV >> 8) & 0xff)) &&
+                       (p[n-1] == (SSL3_CK_FALLBACK_SCSV & 0xff)))
+                       {
+                       /* The SCSV indicates that the client previously tried a higher version.
+                        * Fail if the current version is an unexpected downgrade. */
+                       if (!SSL_ctrl(s, SSL_CTRL_CHECK_PROTO_VERSION, 0, NULL))
+                               {
+                               SSLerr(SSL_F_SSL_BYTES_TO_CIPHER_LIST,SSL_R_INAPPROPRIATE_FALLBACK);
+                               if (s->s3)
+                                       ssl3_send_alert(s,SSL3_AL_FATAL,SSL_AD_INAPPROPRIATE_FALLBACK);
+                               goto err;
+                               }
+                       continue;
+                       }
+
                c=ssl_get_cipher_by_char(s,p);
                p+=n;
                if (c != NULL)