Allow reconfiguration of compression and cipher settings in

mid-session in SSH2: this forces an immediate rekey to activate the
new settings. I'm not sure exactly what this will be useful for
(except possibly it might make comparative performance testing
easier?), but it has wonderful James Bond value for being able to
switch to a more secure cipher before doing anything sensitive :-)
If, that is, you weren't using the most secure one to begin with...

git-svn-id: svn://svn.tartarus.org/sgt/putty@5051 cda61777-01e9-0310-a592-d414129be87e

diff --git a/config.c b/config.c
index e269e1f..b1a49b6 100644 (file)
--- a/config.c
+++ b/config.c
@@ -1589,7 +1589,7 @@ void setup_config_box(struct controlbox *b, struct sesslist *sesslist,
        ctrl_settitle(b, "Connection/SSH",
                      "Options controlling SSH connections");
 
-       if (midsession) {
+       if (midsession && protcfginfo == 1) {
            s = ctrl_getset(b, "Connection/SSH", "disclaimer", NULL);
            ctrl_text(s, "Nothing on this panel may be reconfigured in mid-"
                      "session; it is only here so that sub-panels of it can "
@@ -1614,10 +1614,20 @@ void setup_config_box(struct controlbox *b, struct sesslist *sesslist,
                          HELPCTX(ssh_noshell),
                          dlg_stdcheckbox_handler,
                          I(offsetof(Config,ssh_no_shell)));
+       }
+
+       if (!midsession || protcfginfo != 1) {
+           s = ctrl_getset(b, "Connection/SSH", "protocol", "Protocol options");
+
            ctrl_checkbox(s, "Enable compression", 'e',
                          HELPCTX(ssh_compress),
                          dlg_stdcheckbox_handler,
                          I(offsetof(Config,compression)));
+       }
+
+       if (!midsession) {
+           s = ctrl_getset(b, "Connection/SSH", "protocol", "Protocol options");
+
            ctrl_radiobuttons(s, "Preferred SSH protocol version:", NO_SHORTCUT, 4,
                              HELPCTX(ssh_protocol),
                              dlg_stdradiobutton_handler,
@@ -1626,7 +1636,9 @@ void setup_config_box(struct controlbox *b, struct sesslist *sesslist,
                              "1", '1', I(1),
                              "2", '2', I(2),
                              "2 only", 'y', I(3), NULL);
+       }
 
+       if (!midsession || protcfginfo != 1) {
            s = ctrl_getset(b, "Connection/SSH", "encryption", "Encryption options");
            c = ctrl_draglist(s, "Encryption cipher selection policy:", 's',
                              HELPCTX(ssh_ciphers),

diff --git a/ssh.c b/ssh.c
index 0815ff3..a9e04bf 100644 (file)
--- a/ssh.c
+++ b/ssh.c
@@ -750,6 +750,7 @@ struct ssh_tag {
     unsigned long max_data_size;
     int kex_in_progress;
     long next_rekey, last_rekey;
+    char *deferred_rekey_reason;    /* points to STATIC string; don't free */
 };
 
 #define logevent(s) logevent(ssh->frontend, s)
@@ -4649,7 +4650,7 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
        int n_preferred_ciphers;
        const struct ssh2_ciphers *preferred_ciphers[CIPHER_MAX];
        const struct ssh_compress *preferred_comp;
-       int first_kex;
+       int got_session_id, activated_authconn;
        struct Packet *pktout;
     };
     crState(do_ssh2_transport_state);
@@ -4660,10 +4661,20 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
     s->csmac_tobe = s->scmac_tobe = NULL;
     s->cscomp_tobe = s->sccomp_tobe = NULL;
 
-    s->first_kex = 1;
+    s->got_session_id = s->activated_authconn = FALSE;
 
+    /*
+     * Be prepared to work around the buggy MAC problem.
+     */
+    if (ssh->remote_bugs & BUG_SSH2_HMAC)
+       s->maclist = buggymacs, s->nmacs = lenof(buggymacs);
+    else
+       s->maclist = macs, s->nmacs = lenof(macs);
+
+  begin_key_exchange:
     {
-       int i;
+       int i, j, commalist_started;
+
        /*
         * Set up the preferred key exchange. (NULL => warn below here)
         */
@@ -4691,10 +4702,7 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
                break;
            }
        }
-    }
 
-    {
-       int i;
        /*
         * Set up the preferred ciphers. (NULL => warn below here)
         */
@@ -4724,27 +4732,14 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
                break;
            }
        }
-    }
-
-    /*
-     * Set up preferred compression.
-     */
-    if (ssh->cfg.compression)
-       s->preferred_comp = &ssh_zlib;
-    else
-       s->preferred_comp = &ssh_comp_none;
-
-    /*
-     * Be prepared to work around the buggy MAC problem.
-     */
-    if (ssh->remote_bugs & BUG_SSH2_HMAC)
-       s->maclist = buggymacs, s->nmacs = lenof(buggymacs);
-    else
-       s->maclist = macs, s->nmacs = lenof(macs);
 
-  begin_key_exchange:
-    {
-       int i, j, commalist_started;
+       /*
+        * Set up preferred compression.
+        */
+       if (ssh->cfg.compression)
+           s->preferred_comp = &ssh_zlib;
+       else
+           s->preferred_comp = &ssh_comp_none;
 
        /*
         * Enable queueing of outgoing auth- or connection-layer
@@ -5116,7 +5111,7 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
     verify_ssh_host_key(ssh->frontend,
                        ssh->savedhost, ssh->savedport, ssh->hostkey->keytype,
                        s->keystr, s->fingerprint);
-    if (s->first_kex) {                       /* don't bother logging this in rekeys */
+    if (!s->got_session_id) {     /* don't bother logging this in rekeys */
        logevent("Host key fingerprint is:");
        logevent(s->fingerprint);
     }
@@ -5129,9 +5124,11 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
      * the session id, used in session key construction and
      * authentication.
      */
-    if (s->first_kex)
+    if (!s->got_session_id) {
        memcpy(ssh->v2_session_id, s->exchange_hash,
               sizeof(s->exchange_hash));
+       s->got_session_id = TRUE;
+    }
 
     /*
      * Send SSH2_MSG_NEWKEYS.
@@ -5249,14 +5246,25 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
     }
 
     /*
-     * Key exchange is over. Schedule a timer for our next rekey.
+     * Key exchange is over. Loop straight back round if we have a
+     * deferred rekey reason.
+     */
+    if (ssh->deferred_rekey_reason) {
+       logevent(ssh->deferred_rekey_reason);
+       pktin = NULL;
+       ssh->deferred_rekey_reason = NULL;
+       goto begin_key_exchange;
+    }
+
+    /*
+     * Otherwise, schedule a timer for our next rekey.
      */
     ssh->kex_in_progress = FALSE;
     ssh->last_rekey = GETTICKCOUNT();
     if (ssh->cfg.ssh_rekey_time != 0)
        ssh->next_rekey = schedule_timer(ssh->cfg.ssh_rekey_time*60*TICKSPERSEC,
                                         ssh2_timer, ssh);
-    
+
     /*
      * If this is the first key exchange phase, we must pass the
      * SSH2_MSG_NEWKEYS packet to the next layer, not because it
@@ -5265,10 +5273,10 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
      * exchange phases, we don't pass SSH2_MSG_NEWKEYS on, because
      * it would only confuse the layer above.
      */
-    if (!s->first_kex) {
+    if (s->activated_authconn) {
        crReturn(1);
     }
-    s->first_kex = 0;
+    s->activated_authconn = TRUE;
 
     /*
      * Now we're encrypting. Begin returning 1 to the protocol main
@@ -7366,6 +7374,7 @@ static const char *ssh_init(void *frontend_handle, void **backend_handle,
     ssh->queuelen = ssh->queuesize = 0;
     ssh->queueing = FALSE;
     ssh->qhead = ssh->qtail = NULL;
+    ssh->deferred_rekey_reason = NULL;
 
     *backend_handle = ssh;
 
@@ -7503,7 +7512,7 @@ static void ssh_free(void *handle)
 static void ssh_reconfig(void *handle, Config *cfg)
 {
     Ssh ssh = (Ssh) handle;
-    char *rekeying = NULL;
+    char *rekeying = NULL, rekey_mandatory = FALSE;
     unsigned long old_max_data_size;
 
     pinger_reconfig(ssh->pinger, &ssh->cfg, cfg);
@@ -7530,11 +7539,27 @@ static void ssh_reconfig(void *handle, Config *cfg)
            rekeying = "Initiating key re-exchange (data limit lowered)";
     }
 
-    if (rekeying && !ssh->kex_in_progress) {
-       do_ssh2_transport(ssh, rekeying, -1, NULL);
+    if (ssh->cfg.compression != cfg->compression) {
+       rekeying = "Initiating key re-exchange (compression setting changed)";
+       rekey_mandatory = TRUE;
+    }
+
+    if (ssh->cfg.ssh2_des_cbc != cfg->ssh2_des_cbc ||
+       memcmp(ssh->cfg.ssh_cipherlist, cfg->ssh_cipherlist,
+              sizeof(ssh->cfg.ssh_cipherlist))) {
+       rekeying = "Initiating key re-exchange (cipher settings changed)";
+       rekey_mandatory = TRUE;
     }
 
     ssh->cfg = *cfg;                  /* STRUCTURE COPY */
+
+    if (rekeying) {
+       if (!ssh->kex_in_progress) {
+           do_ssh2_transport(ssh, rekeying, -1, NULL);
+       } else if (rekey_mandatory) {
+           ssh->deferred_rekey_reason = rekeying;
+       }
+    }
 }
 
 /*