Option to disable padding extension.
authorDr. Stephen Henson <steve@openssl.org>
Sun, 1 Jun 2014 15:08:18 +0000 (16:08 +0100)
committerDr. Stephen Henson <steve@openssl.org>
Sun, 1 Jun 2014 17:15:21 +0000 (18:15 +0100)
Add TLS padding extension to SSL_OP_ALL so it is used with other
"bugs" options and can be turned off.

This replaces SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG which is an ancient
option referring to SSLv2 and SSLREF.

PR#3336

doc/ssl/SSL_CTX_set_options.pod
ssl/ssl.h
ssl/t1_lib.c

index 4f990b2..e2548c3 100644 (file)
@@ -112,6 +112,12 @@ vulnerability affecting CBC ciphers, which cannot be handled by some
 broken SSL implementations.  This option has no effect for connections
 using other ciphers.
 
+=item SSL_OP_TLSEXT_PADDING
+
+Adds a padding extension to ensure the ClientHello size is never between
+256 and 511 bytes in length. This is needed as a workaround for some
+implementations.
+
 =item SSL_OP_ALL
 
 All of the above bug workarounds.
index 7d0c7bb..950212f 100644 (file)
--- a/ssl/ssl.h
+++ b/ssl/ssl.h
@@ -662,7 +662,7 @@ struct ssl_session_st
 /* Allow initial connection to servers that don't support RI */
 #define SSL_OP_LEGACY_SERVER_CONNECT                   0x00000004L
 #define SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG                0x00000008L
-#define SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG             0x00000010L
+#define SSL_OP_TLSEXT_PADDING                          0x00000010L
 #define SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER              0x00000020L
 #define SSL_OP_SAFARI_ECDHE_ECDSA_BUG                  0x00000040L
 #define SSL_OP_SSLEAY_080_CLIENT_DH_BUG                        0x00000080L
@@ -671,6 +671,8 @@ struct ssl_session_st
 
 /* Hasn't done anything since OpenSSL 0.9.7h, retained for compatibility */
 #define SSL_OP_MSIE_SSLV2_RSA_PADDING                  0x0
+/* Refers to ancient SSLREF and SSLv2, retained for compatibility */
+#define SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG             0x0
 
 /* Disable SSL 3.0/TLS 1.0 CBC vulnerability workaround that was added
  * in OpenSSL 0.9.6d.  Usually (depending on the application protocol)
index 0ba37da..c4e27b9 100644 (file)
@@ -1508,35 +1508,36 @@ unsigned char *ssl_add_clienthello_tlsext(SSL *s, unsigned char *p, unsigned cha
        s2n(TLSEXT_TYPE_encrypt_then_mac,ret);
        s2n(0,ret);
 #endif
-#ifdef TLSEXT_TYPE_padding
+
        /* Add padding to workaround bugs in F5 terminators.
         * See https://tools.ietf.org/html/draft-agl-tls-padding-03
         *
         * NB: because this code works out the length of all existing
         * extensions it MUST always appear last.
         */
-       {
-       int hlen = ret - (unsigned char *)s->init_buf->data;
-       /* The code in s23_clnt.c to build ClientHello messages includes the
-        * 5-byte record header in the buffer, while the code in s3_clnt.c does
-        * not. */
-       if (s->state == SSL23_ST_CW_CLNT_HELLO_A)
-               hlen -= 5;
-       if (hlen > 0xff && hlen < 0x200)
-               {
-               hlen = 0x200 - hlen;
-               if (hlen >= 4)
-                       hlen -= 4;
-               else
-                       hlen = 0;
+       if (s->options & SSL_OP_TLSEXT_PADDING)
+               {
+               int hlen = ret - (unsigned char *)s->init_buf->data;
+               /* The code in s23_clnt.c to build ClientHello messages
+                * includes the 5-byte record header in the buffer, while
+                * the code in s3_clnt.c does not.
+                */
+               if (s->state == SSL23_ST_CW_CLNT_HELLO_A)
+                       hlen -= 5;
+               if (hlen > 0xff && hlen < 0x200)
+                       {
+                       hlen = 0x200 - hlen;
+                       if (hlen >= 4)
+                               hlen -= 4;
+                       else
+                               hlen = 0;
 
-               s2n(TLSEXT_TYPE_padding, ret);
-               s2n(hlen, ret);
-               memset(ret, 0, hlen);
-               ret += hlen;
+                       s2n(TLSEXT_TYPE_padding, ret);
+                       s2n(hlen, ret);
+                       memset(ret, 0, hlen);
+                       ret += hlen;
+                       }
                }
-       }
-#endif
 
        if ((extdatalen = ret-p-2) == 0)
                return p;