Factor out code for constructing lists of algorithms for SSH-2 KEXINIT.

diff --git a/ssh.c b/ssh.c
index 5b0957ef73e4f933e71af593a0755dca07358695..bc079e91754b8f6df64a61e7a973b42bc1f15e2c 100644 (file)
--- a/ssh.c
+++ b/ssh.c
@@ -5926,7 +5926,8 @@ static void ssh1_protocol(Ssh ssh, void *vin, int inlen,
 /*
  * Utility routine for decoding comma-separated strings in KEXINIT.
  */
-static int in_commasep_string(char *needle, char *haystack, int haylen)
+static int in_commasep_string(char const *needle, char const *haystack,
+                             int haylen)
 {
     int needlen;
     if (!needle || !haystack)         /* protect against null pointers */
@@ -5957,7 +5958,8 @@ static int in_commasep_string(char *needle, char *haystack, int haylen)
 /*
  * Similar routine for checking whether we have the first string in a list.
  */
-static int first_in_commasep_string(char *needle, char *haystack, int haylen)
+static int first_in_commasep_string(char const *needle, char const *haystack,
+                                   int haylen)
 {
     int needlen;
     if (!needle || !haystack)         /* protect against null pointers */
@@ -5975,6 +5977,19 @@ static int first_in_commasep_string(char *needle, char *haystack, int haylen)
     return 0;
 }
 
+/*
+ * Add a value to the comma-separated string at the end of the packet.
+ * If the value is already in the string, don't bother adding it again.
+ */
+static void ssh2_pkt_addstring_commasep(struct Packet *pkt, const char *data)
+{
+    if (in_commasep_string(data, (char *)pkt->data + pkt->savedpos,
+                          pkt->length - pkt->savedpos)) return;
+    if (pkt->length - pkt->savedpos > 0)
+       ssh_pkt_addstring_str(pkt, ",");
+    ssh_pkt_addstring_str(pkt, data);
+}
+
 
 /*
  * SSH-2 key creation method.
@@ -6070,7 +6085,7 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
   begin_key_exchange:
     ssh->pkt_kctx = SSH2_PKTCTX_NOKEX;
     {
-       int i, j, k, commalist_started;
+       int i, j, k;
 
        /*
         * Set up the preferred key exchange. (NULL => warn below here)
@@ -6168,16 +6183,11 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
            ssh2_pkt_addbyte(s->pktout, (unsigned char) random_byte());
        /* List key exchange algorithms. */
        ssh2_pkt_addstring_start(s->pktout);
-       commalist_started = 0;
        for (i = 0; i < s->n_preferred_kex; i++) {
            const struct ssh_kexes *k = s->preferred_kex[i];
            if (!k) continue;          /* warning flag */
-           for (j = 0; j < k->nkexes; j++) {
-               if (commalist_started)
-                   ssh2_pkt_addstring_str(s->pktout, ",");
-               ssh2_pkt_addstring_str(s->pktout, k->list[j]->name);
-               commalist_started = 1;
-           }
+           for (j = 0; j < k->nkexes; j++)
+               ssh2_pkt_addstring_commasep(s->pktout, k->list[j]->name);
        }
        /* List server host key algorithms. */
         if (!s->got_session_id) {
@@ -6186,11 +6196,8 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
              * we're prepared to cope with.
              */
             ssh2_pkt_addstring_start(s->pktout);
-            for (i = 0; i < lenof(hostkey_algs); i++) {
-                ssh2_pkt_addstring_str(s->pktout, hostkey_algs[i]->name);
-                if (i < lenof(hostkey_algs) - 1)
-                    ssh2_pkt_addstring_str(s->pktout, ",");
-            }
+            for (i = 0; i < lenof(hostkey_algs); i++)
+                ssh2_pkt_addstring_commasep(s->pktout, hostkey_algs[i]->name);
         } else {
             /*
              * In subsequent key exchanges, we list only the kex
@@ -6205,26 +6212,18 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
        /* List encryption algorithms (client->server then server->client). */
        for (k = 0; k < 2; k++) {
            ssh2_pkt_addstring_start(s->pktout);
-           commalist_started = 0;
            for (i = 0; i < s->n_preferred_ciphers; i++) {
                const struct ssh2_ciphers *c = s->preferred_ciphers[i];
                if (!c) continue;              /* warning flag */
-               for (j = 0; j < c->nciphers; j++) {
-                   if (commalist_started)
-                       ssh2_pkt_addstring_str(s->pktout, ",");
-                   ssh2_pkt_addstring_str(s->pktout, c->list[j]->name);
-                   commalist_started = 1;
-               }
+               for (j = 0; j < c->nciphers; j++)
+                   ssh2_pkt_addstring_commasep(s->pktout, c->list[j]->name);
            }
        }
        /* List MAC algorithms (client->server then server->client). */
        for (j = 0; j < 2; j++) {
            ssh2_pkt_addstring_start(s->pktout);
-           for (i = 0; i < s->nmacs; i++) {
-               ssh2_pkt_addstring_str(s->pktout, s->maclist[i]->name);
-               if (i < s->nmacs - 1)
-                   ssh2_pkt_addstring_str(s->pktout, ",");
-           }
+           for (i = 0; i < s->nmacs; i++)
+               ssh2_pkt_addstring_commasep(s->pktout, s->maclist[i]->name);
        }
        /* List client->server compression algorithms,
         * then server->client compression algorithms. (We use the
@@ -6233,25 +6232,18 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
            ssh2_pkt_addstring_start(s->pktout);
            assert(lenof(compressions) > 1);
            /* Prefer non-delayed versions */
-           ssh2_pkt_addstring_str(s->pktout, s->preferred_comp->name);
+           ssh2_pkt_addstring_commasep(s->pktout, s->preferred_comp->name);
            /* We don't even list delayed versions of algorithms until
             * they're allowed to be used, to avoid a race. See the end of
             * this function. */
-           if (s->userauth_succeeded && s->preferred_comp->delayed_name) {
-               ssh2_pkt_addstring_str(s->pktout, ",");
-               ssh2_pkt_addstring_str(s->pktout,
-                                      s->preferred_comp->delayed_name);
-           }
+           if (s->userauth_succeeded && s->preferred_comp->delayed_name)
+               ssh2_pkt_addstring_commasep(s->pktout,
+                                           s->preferred_comp->delayed_name);
            for (i = 0; i < lenof(compressions); i++) {
                const struct ssh_compress *c = compressions[i];
-               if (c != s->preferred_comp) {
-                   ssh2_pkt_addstring_str(s->pktout, ",");
-                   ssh2_pkt_addstring_str(s->pktout, c->name);
-                   if (s->userauth_succeeded && c->delayed_name) {
-                       ssh2_pkt_addstring_str(s->pktout, ",");
-                       ssh2_pkt_addstring_str(s->pktout, c->delayed_name);
-                   }
-               }
+               ssh2_pkt_addstring_commasep(s->pktout, c->name);
+               if (s->userauth_succeeded && c->delayed_name)
+                   ssh2_pkt_addstring_commasep(s->pktout, c->delayed_name);
            }
        }
        /* List client->server languages. Empty list. */