Support reconfiguration of key exchange in mid-session. The fiddly

[u/mdw/putty] / ssh.c

diff --git a/ssh.c b/ssh.c
index e619b59..e92eb1d 100644 (file)
--- a/ssh.c
+++ b/ssh.c
@@ -746,7 +746,7 @@ struct ssh_tag {
     unsigned long incoming_data_size, outgoing_data_size, deferred_data_size;
     unsigned long max_data_size;
     int kex_in_progress;
-    long next_rekey;
+    long next_rekey, last_rekey;
 };
 
 #define logevent(s) logevent(ssh->frontend, s)
@@ -5211,6 +5211,7 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen,
      * Key exchange is over. 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);
@@ -7213,7 +7214,7 @@ static void ssh2_timer(void *ctx, long now)
 {
     Ssh ssh = (Ssh)ctx;
 
-    if (!ssh->kex_in_progress &&
+    if (!ssh->kex_in_progress && ssh->cfg.ssh_rekey_time != 0 &&
        now - ssh->next_rekey >= 0) {
        do_ssh2_transport(ssh, "Initiating key re-exchange (timeout)",
                          -1, NULL);
@@ -7459,8 +7460,37 @@ static void ssh_free(void *handle)
 static void ssh_reconfig(void *handle, Config *cfg)
 {
     Ssh ssh = (Ssh) handle;
+    char *rekeying = NULL;
+    unsigned long old_max_data_size;
+
     pinger_reconfig(ssh->pinger, &ssh->cfg, cfg);
     ssh_setup_portfwd(ssh, cfg);
+
+    if (ssh->cfg.ssh_rekey_time != cfg->ssh_rekey_time &&
+       cfg->ssh_rekey_time != 0) {
+       long new_next = ssh->last_rekey + cfg->ssh_rekey_time*60*TICKSPERSEC;
+       long now = GETTICKCOUNT();
+
+       if (new_next - now < 0) {
+           rekeying = "Initiating key re-exchange (timeout shortened)";
+       } else {
+           ssh->next_rekey = schedule_timer(new_next - now, ssh2_timer, ssh);
+       }
+    }
+
+    old_max_data_size = ssh->max_data_size;
+    ssh->max_data_size = parse_blocksize(cfg->ssh_rekey_data);
+    if (old_max_data_size != ssh->max_data_size &&
+       ssh->max_data_size != 0) {
+       if (ssh->outgoing_data_size > ssh->max_data_size ||
+           ssh->incoming_data_size > ssh->max_data_size)
+           rekeying = "Initiating key re-exchange (data limit lowered)";
+    }
+
+    if (rekeying && !ssh->kex_in_progress) {
+       do_ssh2_transport(ssh, rekeying, -1, NULL);
+    }
+
     ssh->cfg = *cfg;                  /* STRUCTURE COPY */
 }