Restructure things so that a single entry in the KEX preference list can

correspond to multiple SSH-2 KEX algorithms.  We already do the equivalent
for cipher algorithms.

[originally from svn r6262]

ssh.c

@@ -4996,7 +4996,7 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
 	void *hkey;		       /* actual host key */
 	unsigned char exchange_hash[20];
 	int n_preferred_kex;
-	const struct ssh_kex *preferred_kex[KEX_MAX];
+	const struct ssh_kexes *preferred_kex[KEX_MAX];
 	int n_preferred_ciphers;
 	const struct ssh2_ciphers *preferred_ciphers[CIPHER_MAX];
 	const struct ssh_compress *preferred_comp;
@@ -5119,12 +5119,14 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
 	ssh2_pkt_addstring_start(s->pktout);
 	commalist_started = 0;
 	for (i = 0; i < s->n_preferred_kex; i++) {
-	    const struct ssh_kex *k = s->preferred_kex[i];
+	    const struct ssh_kexes *k = s->preferred_kex[i];
 	    if (!k) continue;	       /* warning flag */
-	    if (commalist_started)
+	    for (j = 0; j < k->nkexes; j++) {
-		ssh2_pkt_addstring_str(s->pktout, ",");
+		if (commalist_started)
-	    ssh2_pkt_addstring_str(s->pktout, s->preferred_kex[i]->name);
+		    ssh2_pkt_addstring_str(s->pktout, ",");
-	    commalist_started = 1;
+		ssh2_pkt_addstring_str(s->pktout, k->list[j]->name);
+		commalist_started = 1;
+	    }
 	}
 	/* List server host key algorithms. */
 	ssh2_pkt_addstring_start(s->pktout);
@@ -5241,13 +5243,17 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
 
 	preferred = NULL;
 	for (i = 0; i < s->n_preferred_kex; i++) {
-	    const struct ssh_kex *k = s->preferred_kex[i];
+	    const struct ssh_kexes *k = s->preferred_kex[i];
 	    if (!k) {
 		s->warn_kex = TRUE;
 	    } else {
-		if (!preferred) preferred = k->name;
+		for (j = 0; j < k->nkexes; j++) {
-		if (in_commasep_string(k->name, str, len))
+		    if (!preferred) preferred = k->list[j]->name;
-		    ssh->kex = k;
+		    if (in_commasep_string(k->list[j]->name, str, len)) {
+			ssh->kex = k->list[j];
+			break;
+		    }
+		}
 	    }
 	    if (ssh->kex)
 		break;
@@ -5528,7 +5534,7 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
     set_busy_status(ssh->frontend, BUSY_NOT);
 
     hash_string(ssh->kex->hash, ssh->exhash, s->hostkeydata, s->hostkeylen);
-    if (ssh->kex == &ssh_diffiehellman_gex) {
+    if (!ssh->kex->pdata) {
 	hash_uint32(ssh->kex->hash, ssh->exhash, s->pbits);
 	hash_mpint(ssh->kex->hash, ssh->exhash, s->p);
 	hash_mpint(ssh->kex->hash, ssh->exhash, s->g);
@@ -5717,7 +5723,7 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
      */
     freebn(s->f);
     freebn(s->K);
-    if (ssh->kex == &ssh_diffiehellman_gex) {
+    if (!ssh->kex->pdata) {
 	freebn(s->g);
 	freebn(s->p);
     }

ssh.h

@@ -206,6 +206,11 @@ struct ssh_kex {
     const struct ssh_hash *hash;
 };
 
+struct ssh_kexes {
+    int nkexes;
+    const struct ssh_kex *const *list;
+};
+
 struct ssh_signkey {
     void *(*newkey) (char *data, int len);
     void (*freekey) (void *key);
@@ -256,9 +261,9 @@ extern const struct ssh2_ciphers ssh2_blowfish;
 extern const struct ssh2_ciphers ssh2_arcfour;
 extern const struct ssh_hash ssh_sha1;
 extern const struct ssh_hash ssh_sha256;
-extern const struct ssh_kex ssh_diffiehellman_group1;
+extern const struct ssh_kexes ssh_diffiehellman_group1;
-extern const struct ssh_kex ssh_diffiehellman_group14;
+extern const struct ssh_kexes ssh_diffiehellman_group14;
-extern const struct ssh_kex ssh_diffiehellman_gex;
+extern const struct ssh_kexes ssh_diffiehellman_gex;
 extern const struct ssh_signkey ssh_dss;
 extern const struct ssh_signkey ssh_rsa;
 extern const struct ssh_mac ssh_hmac_md5;

sshdh.c

@@ -46,21 +46,48 @@ static const unsigned char P14[] = {
  */
 static const unsigned char G[] = { 2 };
 
-const struct ssh_kex ssh_diffiehellman_group1 = {
+static const struct ssh_kex ssh_diffiehellman_group1_sha1 = {
     "diffie-hellman-group1-sha1", "group1",
     P1, G, lenof(P1), lenof(G), &ssh_sha1
 };
 
-const struct ssh_kex ssh_diffiehellman_group14 = {
+static const struct ssh_kex *const group1_list[] = {
+    &ssh_diffiehellman_group1_sha1
+};
+
+const struct ssh_kexes ssh_diffiehellman_group1 = {
+    sizeof(group1_list) / sizeof(*group1_list),
+    group1_list
+};
+
+static const struct ssh_kex ssh_diffiehellman_group14_sha1 = {
     "diffie-hellman-group14-sha1", "group14",
     P14, G, lenof(P14), lenof(G), &ssh_sha1
 };
 
-const struct ssh_kex ssh_diffiehellman_gex = {
+static const struct ssh_kex *const group14_list[] = {
+    &ssh_diffiehellman_group14_sha1
+};
+
+const struct ssh_kexes ssh_diffiehellman_group14 = {
+    sizeof(group14_list) / sizeof(*group14_list),
+    group14_list
+};
+
+static const struct ssh_kex ssh_diffiehellman_gex_sha1 = {
     "diffie-hellman-group-exchange-sha1", NULL,
     NULL, NULL, 0, 0, &ssh_sha1
 };
 
+static const struct ssh_kex *const gex_list[] = {
+    &ssh_diffiehellman_gex_sha1
+};
+
+const struct ssh_kexes ssh_diffiehellman_gex = {
+    sizeof(gex_list) / sizeof(*gex_list),
+    gex_list
+};
+
 /*
  * Variables.
  */