Add SSL_COMPRESS_METHOD variable (included in +StdEnvVars) to note

the negotiated compression.

Reviewed by: wrowe, Maxime Petazzoni
Submitted by: Georg v. Zezschwitz <gvz 2scale.de>


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@209469 13f79535-47bb-0310-9956-ffa450edef68

docs/manual/mod/mod_ssl.xml

@@ -65,6 +65,7 @@ compatibility variables.</p>
 <tr><td><code>SSL_CIPHER_EXPORT</code></td>             <td>string</td>    <td><code>true</code> if cipher is an export cipher</td></tr>
 <tr><td><code>SSL_CIPHER_USEKEYSIZE</code></td>         <td>number</td>    <td>Number of cipher bits (actually used)</td></tr>
 <tr><td><code>SSL_CIPHER_ALGKEYSIZE</code></td>         <td>number</td>    <td>Number of cipher bits (possible)</td></tr>
+<tr><td><code>SSL_COMPRESS_METHOD</code></td>           <td>string</td>    <td>SSL compression method negotiated</td></tr>
 <tr><td><code>SSL_VERSION_INTERFACE</code></td>         <td>string</td>    <td>The mod_ssl program version</td></tr>
 <tr><td><code>SSL_VERSION_LIBRARY</code></td>           <td>string</td>    <td>The OpenSSL program version</td></tr>
 <tr><td><code>SSL_CLIENT_M_VERSION</code></td>          <td>string</td>    <td>The version of the client certificate</td></tr>

docs/manual/ssl/ssl_faq.xml

@@ -680,6 +680,7 @@ browsers complain that they cannot verify the server certificate?</title>
 <li><a href="#vhosts">HTTPS and name-based vhosts</a></li>
 <li><a href="#vhosts2">Why is it not possible to use Name-Based Virtual
 Hosting to identify different SSL virtual hosts?</a></li>
+<li><a href="#comp">How do I get SSL compression working?</a></li>
 <li><a href="#lockicon">The lock icon in Netscape locks very late</a></li>
 <li><a href="#msie">Why do I get I/O errors with MSIE clients?</a></li>
 <li><a href="#nn">Why do I get I/O errors with NS clients?</a></li>
@@ -804,6 +805,23 @@ Virtual Hosting to identify different SSL virtual hosts?</title>
     Use different port numbers for different SSL hosts.</p> 
 </section>
 
+<section id="comp"><title>How do I get SSL compression working?</title>
+<p>Although SSL compression negotiation was already defined in the specification
+of SSLv2 and TLS, it took until May 2004 when RFC 3749 defined DEFLATE as
+a negotiable standard compression method.
+</p>
+<p>OpenSSL 0.9.8 started to support this by default when compiled with the
+<code>zlib</code> option. If both the client and the server support compression,
+it will be used. However, most clients still try to initially connect with an
+SSLv2 Hello. As SSLv2 did not include an array of prefered compression algorithms
+in its handshake, compression can not be negotiated with these clients.
+If the client disables support for SSLv2, based on the used SSL library 
+a SSLv3 or TLS Hello might be sent and compression might be set up.
+You can verify if clients make use of SSL compression by logging the
+<code>%{SSL_COMPRESS_METHOD}x</code> variable.
+</p>
+</section>
+
 <section id="lockicon"><title>When I use Basic Authentication over HTTPS the lock icon in Netscape browsers
 still shows the unlocked state when the dialog pops up. Does this mean the
 username/password is still transmitted unencrypted?</title>

modules/ssl/ssl_engine_kernel.c

@@ -946,6 +946,7 @@ static const char *ssl_hook_Fixup_vars[] = {
     "SSL_VERSION_INTERFACE",
     "SSL_VERSION_LIBRARY",
     "SSL_PROTOCOL",
+    "SSL_COMPRESS_METHOD",
     "SSL_CIPHER",
     "SSL_CIPHER_EXPORT",
     "SSL_CIPHER_USEKEYSIZE",

modules/ssl/ssl_engine_vars.c

@@ -50,6 +50,7 @@ static char *ssl_var_lookup_ssl_cert_verify(apr_pool_t *p, conn_rec *c);
 static char *ssl_var_lookup_ssl_cipher(apr_pool_t *p, conn_rec *c, char *var);
 static void  ssl_var_lookup_ssl_cipher_bits(SSL *ssl, int *usekeysize, int *algkeysize);
 static char *ssl_var_lookup_ssl_version(apr_pool_t *p, char *var);
+static char *ssl_var_lookup_ssl_compress_meth(SSL *ssl);
 
 static int ssl_is_https(conn_rec *c)
 {
@@ -296,6 +297,9 @@ static char *ssl_var_lookup_ssl(apr_pool_t *p, conn_rec *c, char *var)
         if ((xs = SSL_get_certificate(ssl)) != NULL)
             result = ssl_var_lookup_ssl_cert(p, xs, var+7);
     }
+    else if (ssl != NULL && strcEQ(var, "COMPRESS_METHOD")) {
+        result = ssl_var_lookup_ssl_compress_meth(ssl);
+    }
     return result;
 }
 
@@ -711,6 +715,39 @@ const char *ssl_ext_lookup(apr_pool_t *p, conn_rec *c, int peer,
     return result;
 }
 
+static char *ssl_var_lookup_ssl_compress_meth(SSL *ssl)
+{
+    char *result = "NULL";
+#ifdef OPENSSL_VERSION_NUMBER
+#if (OPENSSL_VERSION_NUMBER >= 0x00908000)
+    SSL_SESSION *pSession = SSL_get_session(ssl);
+
+    if (pSession) {
+        switch (pSession->compress_meth) {
+        case 0:
+            /* default "NULL" already set */
+            break;
+
+            /* Defined by RFC 3749, deflate is coded by "1" */
+        case 1:
+            result = "DEFLATE";
+            break;
+
+            /* IANA assigned compression number for LZS */
+        case 0x40:
+            result = "LZS";
+            break;
+
+        default:
+            result = "UNKNOWN";
+            break;
+        }
+    }
+#endif
+#endif
+    return result;
+}
+
 /*  _________________________________________________________________
 **
 **  SSL Extension to mod_log_config