RT3234: disable compression

CRIME protection: disable compression by default, even if OpenSSL is
compiled with zlib enabled. Applications can still enable compression by
calling SSL_CTX_clear_options(ctx, SSL_OP_NO_COMPRESSION), or by using
the SSL_CONF library to configure compression. SSL_CONF continues to
work as before:

SSL_CONF_cmd(ctx, "Options", "Compression") enables compression.

SSL_CONF_cmd(ctx, "Options", "-Compression") disables compression (now
no-op by default).

The command-line switch has changed from -no_comp to -comp.

Reviewed-by: Rich Salz <rsalz@openssl.org>

CHANGES

@@ -4,6 +4,12 @@
 
  Changes between 1.0.2f and 1.1.0  [xx XXX xxxx]
 
+  *) CRIME protection: disable compression by default, even if OpenSSL is
+     compiled with zlib enabled. Applications can still enable compression
+     by calling SSL_CTX_clear_options(ctx, SSL_OP_NO_COMPRESSION), or by
+     using the SSL_CONF library to configure compression.
+     [Emilia Käsper]
+
   *) The signature of the session callback configured with
      SSL_CTX_sess_set_get_cb was changed. The read-only input buffer
      was explicitly marked as 'const unsigned char*' instead of

apps/apps.h

@@ -285,7 +285,7 @@ void wait_for_async(SSL *s);
 # define OPT_S_ENUM \
         OPT_S__FIRST=3000, \
         OPT_S_NOSSL3, OPT_S_NOTLS1, OPT_S_NOTLS1_1, OPT_S_NOTLS1_2, \
-        OPT_S_BUGS, OPT_S_NOCOMP, OPT_S_ECDHSINGLE, OPT_S_NOTICKET, \
+        OPT_S_BUGS, OPT_S_COMP, OPT_S_ECDHSINGLE, OPT_S_NOTICKET, \
         OPT_S_SERVERPREF, OPT_S_LEGACYRENEG, OPT_S_LEGACYCONN, \
         OPT_S_ONRESUMP, OPT_S_NOLEGACYCONN, OPT_S_STRICT, OPT_S_SIGALGS, \
         OPT_S_CLIENTSIGALGS, OPT_S_CURVES, OPT_S_NAMEDCURVE, OPT_S_CIPHER, \
@@ -298,7 +298,7 @@ void wait_for_async(SSL *s);
         {"no_tls1_1", OPT_S_NOTLS1_1, '-' }, \
         {"no_tls1_2", OPT_S_NOTLS1_2, '-' }, \
         {"bugs", OPT_S_BUGS, '-' }, \
-        {"no_comp", OPT_S_NOCOMP, '-', "Don't use SSL/TLS-level compression" }, \
+        {"comp", OPT_S_COMP, '-', "Use SSL/TLS-level compression" }, \
         {"ecdh_single", OPT_S_ECDHSINGLE, '-' }, \
         {"no_ticket", OPT_S_NOTICKET, '-' }, \
         {"serverpref", OPT_S_SERVERPREF, '-' }, \
@@ -327,7 +327,7 @@ void wait_for_async(SSL *s);
         case OPT_S_NOTLS1_1: \
         case OPT_S_NOTLS1_2: \
         case OPT_S_BUGS: \
-        case OPT_S_NOCOMP: \
+        case OPT_S_COMP: \
         case OPT_S_ECDHSINGLE: \
         case OPT_S_NOTICKET: \
         case OPT_S_SERVERPREF: \

doc/ssl/SSL_CONF_cmd.pod

@@ -131,9 +131,9 @@ These options are deprecated, instead use B<-min_protocol> and B<-max_protocol>.
 
 Various bug workarounds are set, same as setting B<SSL_OP_ALL>.
 
-=item B<-no_comp>
+=item B<-comp>
 
-Disables support for SSL/TLS compression, same as setting B<SSL_OP_NO_COMPRESS>.
+Enables support for SSL/TLS compression, same as clearing B<SSL_OP_NO_COMPRESSION>.
 
 =item B<-no_ticket>
 
@@ -495,6 +495,10 @@ Disable TLS session tickets:
 
  SSL_CONF_cmd(ctx, "Options", "-SessionTicket");
 
+Enable compression:
+
+ SSL_CONF_cmd(ctx, "Options", "Compression");
+
 Set supported curves to P-256, P-384:
 
  SSL_CONF_cmd(ctx, "Curves", "P-256:P-384");

ssl/ssl_conf.c

@@ -581,7 +581,7 @@ static const ssl_conf_cmd_tbl ssl_conf_cmds[] = {
     SSL_CONF_CMD_SWITCH("no_tls1_1", 0),
     SSL_CONF_CMD_SWITCH("no_tls1_2", 0),
     SSL_CONF_CMD_SWITCH("bugs", 0),
-    SSL_CONF_CMD_SWITCH("no_comp", 0),
+    SSL_CONF_CMD_SWITCH("comp", 0),
     SSL_CONF_CMD_SWITCH("ecdh_single", SSL_CONF_FLAG_SERVER),
     SSL_CONF_CMD_SWITCH("no_ticket", 0),
     SSL_CONF_CMD_SWITCH("serverpref", SSL_CONF_FLAG_SERVER),
@@ -640,7 +640,7 @@ static const ssl_switch_tbl ssl_cmd_switches[] = {
     {SSL_OP_NO_TLSv1_1, 0},     /* no_tls1_1 */
     {SSL_OP_NO_TLSv1_2, 0},     /* no_tls1_2 */
     {SSL_OP_ALL, 0},            /* bugs */
-    {SSL_OP_NO_COMPRESSION, 0}, /* no_comp */
+    {SSL_OP_NO_COMPRESSION, 1}, /* comp */
     {SSL_OP_SINGLE_ECDH_USE, 0}, /* ecdh_single */
     {SSL_OP_NO_TICKET, 0},      /* no_ticket */
     {SSL_OP_CIPHER_SERVER_PREFERENCE, 0}, /* serverpref */

ssl/ssl_lib.c

@@ -2362,6 +2362,13 @@ SSL_CTX *SSL_CTX_new(const SSL_METHOD *meth)
      * deployed might change this.
      */
     ret->options |= SSL_OP_LEGACY_SERVER_CONNECT;
+    /*
+     * Disable compression by default to prevent CRIME. Applications can
+     * re-enable compression by configuring
+     * SSL_CTX_clear_options(ctx, SSL_OP_NO_COMPRESSION);
+     * or by using the SSL_CONF library.
+     */
+    ret->options |= SSL_OP_NO_COMPRESSION;
 
     return (ret);
  err:

util/TLSProxy/Proxy.pm

@@ -142,7 +142,7 @@ sub start
             or die "Failed to redirect stdout";
         open(STDERR, ">&STDOUT");
         my $execcmd = $self->execute
-            ." s_server -no_comp -rev -engine ossltest -accept "
+            ." s_server -rev -engine ossltest -accept "
             .($self->server_port)
             ." -cert ".$self->cert." -naccept ".$self->serverconnects;
         if ($self->ciphers ne "") {