Implement paranoid mode for ZRTP.

Refer to the in-line documentation of enableParanoidMode flag in ZRTPTransformerEngine.java to read the full description.

src/net/java/sip/communicator/impl/neomedia/transform/zrtp/ZRTPTransformEngine.java

@@ -353,6 +353,39 @@ public void run()
 
     private boolean mitmMode = false;
 
+    /**
+     * Enable or disable paranoid mode.
+     * 
+     * The Paranoid mode controls the behaviour and handling of the SAS verify
+     * flag. If Panaoid mode is set to flase then ZRtp applies the normal 
+     * handling. If Paranoid mode is set to true then the handling is:
+     * 
+     * <ul>
+     * <li> Force the SAS verify flag to be false at srtpSecretsOn() callback.
+     *      This gives the user interface (UI) the indication to handle the SAS
+     *      as <b>not verified</b>. See implementation note below.</li>
+     * <li> Don't set the SAS verify flag in the <code>Confirm</code> packets,
+     *      thus the other also must report the SAS as <b>not verified</b>.</li>
+     * <li> ignore the <code>SASVerified()</code> function, thus do not set the
+     *      SAS to verified in the ZRTP cache. </li>
+     * <li> Disable the <b>Trusted PBX MitM</b> feature. Just send the 
+     *      <code>SASRelay</code> packet but do not process the relayed data.
+     *      This protects the user from a malicious "trusted PBX".</li>
+     * </ul>
+     * ZRtp performs alls other steps during the ZRTP negotiations as usual, in
+     * particular it computes, compares, uses, and stores the retained secrets.
+     * This avoids unnecessary warning messages. The user may enable or disable
+     * the Paranoid mode on a call-by-call basis without breaking the key 
+     * continuity data.
+     * 
+     * <b>Implementation note:</b></br>
+     * An application shall always display the SAS code if the SAS verify flag
+     * is <code>false</code>. The application shall also use mechanisms to 
+     * remind the user to compare the SAS code, for example useing larger fonts,
+     * different colours and other display features.
+     */
+    private boolean enableParanoidMode = false;
+
     private ZRTCPTransformer zrtcpTransformer = null;
 
     /**
@@ -503,7 +536,9 @@ public synchronized boolean initialize(String zidFilename,
             config = new ZrtpConfigure();
             config.setStandardConfig();
         }
-
+        if (enableParanoidMode) {
+            config.setParanoidMode(enableParanoidMode);
+        }
         zrtpEngine = new ZRtp(zf.getZid(), this, clientIdString, config, mitmMode);
 
         if (timeoutProvider == null)
@@ -1288,12 +1323,36 @@ public void setMitmMode(boolean mitmMode) {
         this.mitmMode = mitmMode;
     }
 
+    /**
+     * Enables or disables paranoid mode.
+     *
+     * For further explanation of paranoid mode refer to the documentation
+     * of ZRtp class.
+     * 
+     * @param yesNo
+     *    If set to true then paranoid mode is enabled.
+     */
+    public void setParanoidMode(boolean yesNo) {
+        enableParanoidMode = yesNo;
+    }
+    
+    /**
+     * Check status of paranoid mode.
+     * 
+     * @return
+     *    Returns true if paranoid mode is enabled.
+     */
+    public boolean isParanoidMode() {
+        return enableParanoidMode;
+    }
+
     /**
      * Check the state of the enrollment mode.
      *
      * If true then we will set the enrollment flag (E) in the confirm
-     * packets and performs the enrollment actions. A MitM (PBX) enrollment service sets this flagstarted this ZRTP
-     * session. Can be set to true only if mitmMode is also true.
+     * packets and performs the enrollment actions. A MitM (PBX) 
+     * enrollment service sets this flag.
+     * 
      * @return status of the enrollmentMode flag.
      */
     public boolean isEnrollmentMode() {
@@ -1308,7 +1367,7 @@ public boolean isEnrollmentMode() {
      *
      * If true then we will set the enrollment flag (E) in the confirm
      * packets and perform the enrollment actions. A MitM (PBX) enrollment
-     * service must sets this mode to true.
+     * service must set this mode to true.
      *
      * Can be set to true only if mitmMode is also true.
      *