X-Git-Url: https://git.distorted.org.uk/u/mdw/putty/blobdiff_plain/6bbce591e72352b2ce5e4915e7ab05f316083ab7..2ccb2fc83a62d8ded4b0287b72384ce22a83000c:/ssh.c

diff --git a/ssh.c b/ssh.c
index 520f6fa7..75610c67 100644
--- a/ssh.c
+++ b/ssh.c
@@ -462,10 +462,10 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 const static struct ssh_signkey *hostkey_algs[] = { &ssh_rsa, &ssh_dss };
 
 const static struct ssh_mac *macs[] = {
-    &ssh_sha1, &ssh_md5
+    &ssh_hmac_sha1, &ssh_hmac_md5
 };
 const static struct ssh_mac *buggymacs[] = {
-    &ssh_sha1_buggy, &ssh_md5
+    &ssh_hmac_sha1_buggy, &ssh_hmac_md5
 };
 
 static void *ssh_comp_none_init(void)
@@ -679,7 +679,8 @@ struct ssh_tag {
     const struct plug_function_table *fn;
     /* the above field _must_ be first in the structure */
 
-    SHA_State exhash, exhashbase;
+    char *v_c, *v_s;
+    void *exhash;
 
     Socket s;
 
@@ -704,7 +705,8 @@ struct ssh_tag {
     void *cs_comp_ctx, *sc_comp_ctx;
     const struct ssh_kex *kex;
     const struct ssh_signkey *hostkey;
-    unsigned char v2_session_id[20];
+    unsigned char v2_session_id[32];
+    int v2_session_id_len;
     void *kex_ctx;
 
     char *savedhost;
@@ -721,6 +723,7 @@ struct ssh_tag {
     struct ssh_channel *mainchan;      /* primary session channel */
     int exitcode;
     int close_expected;
+    int clean_exit;
 
     tree234 *rportfwds, *portfwds;
 
@@ -1266,7 +1269,8 @@ static struct Packet *ssh2_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
      * _Completely_ silly lengths should be stomped on before they
      * do us any more damage.
      */
-    if (st->len < 0 || st->pad < 0 || st->len + st->pad < 0) {
+    if (st->len < 0 || st->len > 35000 || st->pad < 4 ||
+	st->len - st->pad < 1 || (st->len + 4) % st->cipherblk != 0) {
 	bombout(("Incoming packet was garbled on decryption"));
 	ssh_free_packet(st->pktin);
 	crStop(NULL);
@@ -1559,21 +1563,21 @@ static int ssh_versioncmp(char *a, char *b)
 
 /*
  * Utility routines for putting an SSH-protocol `string' and
- * `uint32' into a SHA state.
+ * `uint32' into a hash state.
  */
-static void sha_string(SHA_State * s, void *str, int len)
+static void hash_string(const struct ssh_hash *h, void *s, void *str, int len)
 {
     unsigned char lenblk[4];
     PUT_32BIT(lenblk, len);
-    SHA_Bytes(s, lenblk, 4);
-    SHA_Bytes(s, str, len);
+    h->bytes(s, lenblk, 4);
+    h->bytes(s, str, len);
 }
 
-static void sha_uint32(SHA_State * s, unsigned i)
+static void hash_uint32(const struct ssh_hash *h, void *s, unsigned i)
 {
     unsigned char intblk[4];
     PUT_32BIT(intblk, i);
-    SHA_Bytes(s, intblk, 4);
+    h->bytes(s, intblk, 4);
 }
 
 /*
@@ -1651,8 +1655,6 @@ static unsigned char *ssh2_mpint_fmt(Bignum b, int *len)
     unsigned char *p;
     int i, n = (bignum_bitcount(b) + 7) / 8;
     p = snewn(n + 1, unsigned char);
-    if (!p)
-	fatalbox("out of memory");
     p[0] = 0;
     for (i = 1; i <= n; i++)
 	p[i] = bignum_byte(b, n - i);
@@ -1971,12 +1973,12 @@ void bndebug(char *string, Bignum b)
 }
 #endif
 
-static void sha_mpint(SHA_State * s, Bignum b)
+static void hash_mpint(const struct ssh_hash *h, void *s, Bignum b)
 {
     unsigned char *p;
     int len;
     p = ssh2_mpint_fmt(b, &len);
-    sha_string(s, p, len);
+    hash_string(h, s, p, len);
     sfree(p);
 }
 
@@ -2245,10 +2247,13 @@ static void ssh_detect_bugs(Ssh ssh, char *vstring)
 
     if (ssh->cfg.sshbug_rekey2 == FORCE_ON ||
 	(ssh->cfg.sshbug_rekey2 == AUTO &&
-	 (wc_match("OpenSSH_2.[0-4]*", imp) ||
+	 (wc_match("DigiSSH_2.0", imp) ||
+	  wc_match("OpenSSH_2.[0-4]*", imp) ||
 	  wc_match("OpenSSH_2.5.[0-3]*", imp) ||
 	  wc_match("Sun_SSH_1.0", imp) ||
-	  wc_match("Sun_SSH_1.0.1", imp)))) {
+	  wc_match("Sun_SSH_1.0.1", imp) ||
+	  /* All versions <= 1.2.6 (they changed their format in 1.2.7) */
+	  wc_match("WeOnlyDo-*", imp)))) {
 	/*
 	 * These versions have the SSH-2 rekey bug.
 	 */
@@ -2294,23 +2299,20 @@ static int do_ssh_init(Ssh ssh, unsigned char c)
 
     crBegin(ssh->do_ssh_init_crstate);
 
-    /* Search for the string "SSH-" in the input. */
-    s->i = 0;
-    while (1) {
-	static const int transS[] = { 1, 2, 2, 1 };
-	static const int transH[] = { 0, 0, 3, 0 };
-	static const int transminus[] = { 0, 0, 0, -1 };
-	if (c == 'S')
-	    s->i = transS[s->i];
-	else if (c == 'H')
-	    s->i = transH[s->i];
-	else if (c == '-')
-	    s->i = transminus[s->i];
-	else
-	    s->i = 0;
-	if (s->i < 0)
-	    break;
-	crReturn(1);		       /* get another character */
+    /* Search for a line beginning with the string "SSH-" in the input. */
+    for (;;) {
+	if (c != 'S') goto no;
+	crReturn(1);
+	if (c != 'S') goto no;
+	crReturn(1);
+	if (c != 'H') goto no;
+	crReturn(1);
+	if (c != '-') goto no;
+	break;
+      no:
+	while (c != '\012')
+	    crReturn(1);
+	crReturn(1);
     }
 
     s->vstrsize = 16;
@@ -2384,15 +2386,19 @@ static int do_ssh_init(Ssh ssh, unsigned char c)
         ssh_fix_verstring(verstring);
 
         if (ssh->version == 2) {
+	    size_t len;
             /*
              * Hash our version string and their version string.
              */
-            SHA_Init(&ssh->exhashbase);
-            sha_string(&ssh->exhashbase, verstring,
-                       strcspn(verstring, "\015\012"));
-            sha_string(&ssh->exhashbase, s->vstring,
-                       strcspn(s->vstring, "\015\012"));
-
+	    len = strcspn(verstring, "\015\012");
+	    ssh->v_c = snewn(len + 1, char);
+	    memcpy(ssh->v_c, verstring, len);
+	    ssh->v_c[len] = 0;
+	    len = strcspn(s->vstring, "\015\012");
+	    ssh->v_s = snewn(len + 1, char);
+	    memcpy(ssh->v_s, s->vstring, len);
+	    ssh->v_s[len] = 0;
+	    
             /*
              * Initialise SSH-2 protocol.
              */
@@ -2497,24 +2503,29 @@ static void ssh_gotdata(Ssh ssh, unsigned char *data, int datalen)
      * everything to s_rdpkt, and then pass the resulting packets
      * to the proper protocol handler.
      */
-    if (datalen == 0)
-	crReturnV;
-
-    /*
-     * Process queued data if there is any.
-     */
-    ssh_process_queued_incoming_data(ssh);
 
     while (1) {
-	while (datalen > 0) {
-	    if (ssh->frozen)
+	while (bufchain_size(&ssh->queued_incoming_data) > 0 || datalen > 0) {
+	    if (ssh->frozen) {
 		ssh_queue_incoming_data(ssh, &data, &datalen);
-
-	    ssh_process_incoming_data(ssh, &data, &datalen);
-
+		/* This uses up all data and cannot cause anything interesting
+		 * to happen; indeed, for anything to happen at all, we must
+		 * return, so break out. */
+		break;
+	    } else if (bufchain_size(&ssh->queued_incoming_data) > 0) {
+		/* This uses up some or all data, and may freeze the
+		 * session. */
+		ssh_process_queued_incoming_data(ssh);
+	    } else {
+		/* This uses up some or all data, and may freeze the
+		 * session. */
+		ssh_process_incoming_data(ssh, &data, &datalen);
+	    }
+	    /* FIXME this is probably EBW. */
 	    if (ssh->state == SSH_STATE_CLOSED)
 		return;
 	}
+	/* We're out of data. Go and get some more. */
 	crReturnV;
     }
     crFinishV;
@@ -2596,20 +2607,20 @@ static int ssh_closing(Plug plug, const char *error_msg, int error_code,
     Ssh ssh = (Ssh) plug;
     int need_notify = ssh_do_close(ssh, FALSE);
 
-    if (!error_msg && !ssh->close_expected) {
-        error_msg = "Server unexpectedly closed network connection";
+    if (!error_msg) {
+	if (!ssh->close_expected)
+	    error_msg = "Server unexpectedly closed network connection";
+	else
+	    error_msg = "Server closed network connection";
     }
 
     if (need_notify)
         notify_remote_exit(ssh->frontend);
 
-    if (error_msg) {
-	/* A socket error has occurred. */
+    if (error_msg)
 	logevent(error_msg);
+    if (!ssh->close_expected || !ssh->clean_exit)
 	connection_fatal(ssh->frontend, "%s", error_msg);
-    } else {
-        logevent("Server closed network connection");
-    }
     return 0;
 }
 
@@ -2656,8 +2667,6 @@ static const char *connect_to_host(Ssh ssh, char *host, int port,
     const char *err;
 
     ssh->savedhost = snewn(1 + strlen(host), char);
-    if (!ssh->savedhost)
-	fatalbox("Out of memory");
     strcpy(ssh->savedhost, host);
 
     if (port < 0)
@@ -2873,6 +2882,39 @@ static void ssh_agentf_callback(void *cv, void *reply, int replylen)
 }
 
 /*
+ * Client-initiated disconnection. Send a DISCONNECT if `wire_reason'
+ * non-NULL, otherwise just close the connection. `client_reason' == NULL
+ * => log `wire_reason'.
+ */
+static void ssh_disconnect(Ssh ssh, char *client_reason, char *wire_reason,
+			   int code, int clean_exit)
+{
+    char *error;
+    if (!client_reason)
+	client_reason = wire_reason;
+    if (client_reason)
+	error = dupprintf("Disconnected: %s", client_reason);
+    else
+	error = dupstr("Disconnected");
+    if (wire_reason) {
+	if (ssh->version == 1) {
+	    send_packet(ssh, SSH1_MSG_DISCONNECT, PKT_STR, wire_reason,
+			PKT_END);
+	} else if (ssh->version == 2) {
+	    struct Packet *pktout = ssh2_pkt_init(SSH2_MSG_DISCONNECT);
+	    ssh2_pkt_adduint32(pktout, code);
+	    ssh2_pkt_addstring(pktout, wire_reason);
+	    ssh2_pkt_addstring(pktout, "en");	/* language tag */
+	    ssh2_pkt_send_noqueue(ssh, pktout);
+	}
+    }
+    ssh->close_expected = TRUE;
+    ssh->clean_exit = clean_exit;
+    ssh_closing((Plug)ssh, error, 0, 0);
+    sfree(error);
+}
+
+/*
  * Handle the key exchange and user authentication phases.
  */
 static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
@@ -2977,8 +3019,6 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
     s->len = (hostkey.bytes > servkey.bytes ? hostkey.bytes : servkey.bytes);
 
     s->rsabuf = snewn(s->len, unsigned char);
-    if (!s->rsabuf)
-	fatalbox("Out of memory");
 
     /*
      * Verify the host key.
@@ -2990,8 +3030,6 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
 	int len = rsastr_len(&hostkey);
 	char fingerprint[100];
 	char *keystr = snewn(len, char);
-	if (!keystr)
-	    fatalbox("Out of memory");
 	rsastr_fmt(keystr, &hostkey);
 	rsa_fingerprint(fingerprint, sizeof(fingerprint), &hostkey);
 
@@ -3015,8 +3053,8 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
         ssh_set_frozen(ssh, 0);
 
         if (s->dlgret == 0) {
-            ssh->close_expected = TRUE;
-            ssh_closing((Plug)ssh, NULL, 0, 0);
+	    ssh_disconnect(ssh, "User aborted at host key verification",
+			   NULL, 0, TRUE);
 	    crStop(0);
         }
     }
@@ -3096,8 +3134,8 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
 	    }
             ssh_set_frozen(ssh, 0);
 	    if (s->dlgret == 0) {
-		ssh->close_expected = TRUE;
-		ssh_closing((Plug)ssh, NULL, 0, 0);
+		ssh_disconnect(ssh, "User aborted at cipher warning", NULL,
+			       0, TRUE);
 		crStop(0);
 	    }
         }
@@ -3171,9 +3209,7 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
 		     * get_line failed to get a username.
 		     * Terminate.
 		     */
-		    logevent("No username provided. Abandoning session.");
-		    ssh->close_expected = TRUE;
-                    ssh_closing((Plug)ssh, NULL, 0, 0);
+		    ssh_disconnect(ssh, "No username provided", NULL, 0, TRUE);
 		    crStop(1);
 		}
 	    } else {
@@ -3510,13 +3546,7 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
 		 * because one was supplied on the command line
 		 * which has already failed to work). Terminate.
 		 */
-		send_packet(ssh, SSH1_MSG_DISCONNECT,
-			    PKT_STR, "No more passwords available to try",
-			    PKT_END);
-		logevent("Unable to authenticate");
-		connection_fatal(ssh->frontend, "Unable to authenticate");
-		ssh->close_expected = TRUE;
-                ssh_closing((Plug)ssh, NULL, 0, 0);
+		ssh_disconnect(ssh, NULL, "Unable to authenticate", 0, FALSE);
 		crStop(1);
 	    }
 	} else {
@@ -4564,8 +4594,7 @@ static void ssh1_smsg_exit_status(Ssh ssh, struct Packet *pktin)
      * encrypted packet, we close the session once
      * we've sent EXIT_CONFIRMATION.
      */
-    ssh->close_expected = TRUE;
-    ssh_closing((Plug)ssh, NULL, 0, 0);
+    ssh_disconnect(ssh, NULL, NULL, 0, TRUE);
 }
 
 /* Helper function to deal with sending tty modes for REQUEST_PTY */
@@ -4919,26 +4948,26 @@ static int first_in_commasep_string(char *needle, char *haystack, int haylen)
 /*
  * SSH-2 key creation method.
  */
-static void ssh2_mkkey(Ssh ssh, Bignum K, unsigned char *H,
-		       unsigned char *sessid, char chr,
+static void ssh2_mkkey(Ssh ssh, Bignum K, unsigned char *H, char chr,
 		       unsigned char *keyspace)
 {
-    SHA_State s;
-    /* First 20 bytes. */
-    SHA_Init(&s);
+    const struct ssh_hash *h = ssh->kex->hash;
+    void *s;
+    /* First hlen bytes. */
+    s = h->init();
     if (!(ssh->remote_bugs & BUG_SSH2_DERIVEKEY))
-	sha_mpint(&s, K);
-    SHA_Bytes(&s, H, 20);
-    SHA_Bytes(&s, &chr, 1);
-    SHA_Bytes(&s, sessid, 20);
-    SHA_Final(&s, keyspace);
-    /* Next 20 bytes. */
-    SHA_Init(&s);
+	hash_mpint(h, s, K);
+    h->bytes(s, H, h->hlen);
+    h->bytes(s, &chr, 1);
+    h->bytes(s, ssh->v2_session_id, ssh->v2_session_id_len);
+    h->final(s, keyspace);
+    /* Next hlen bytes. */
+    s = h->init();
     if (!(ssh->remote_bugs & BUG_SSH2_DERIVEKEY))
-	sha_mpint(&s, K);
-    SHA_Bytes(&s, H, 20);
-    SHA_Bytes(&s, keyspace, 20);
-    SHA_Final(&s, keyspace + 20);
+	hash_mpint(h, s, K);
+    h->bytes(s, H, h->hlen);
+    h->bytes(s, keyspace, h->hlen);
+    h->final(s, keyspace + h->hlen);
 }
 
 /*
@@ -4951,6 +4980,8 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
     struct do_ssh2_transport_state {
 	int nbits, pbits, warn_kex, warn_cscipher, warn_sccipher;
 	Bignum p, g, e, f, K;
+	void *our_kexinit;
+	int our_kexinitlen;
 	int kex_init_value, kex_reply_value;
 	const struct ssh_mac **maclist;
 	int nmacs;
@@ -4963,9 +4994,9 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
 	char *hostkeydata, *sigdata, *keystr, *fingerprint;
 	int hostkeylen, siglen;
 	void *hkey;		       /* actual host key */
-	unsigned char exchange_hash[20];
+	unsigned char exchange_hash[32];
 	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;
@@ -5088,12 +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)
-		ssh2_pkt_addstring_str(s->pktout, ",");
-	    ssh2_pkt_addstring_str(s->pktout, s->preferred_kex[i]->name);
-	    commalist_started = 1;
+	    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;
+	    }
 	}
 	/* List server host key algorithms. */
 	ssh2_pkt_addstring_start(s->pktout);
@@ -5174,15 +5207,14 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
 	ssh2_pkt_adduint32(s->pktout, 0);
     }
 
-    ssh->exhash = ssh->exhashbase;
-    sha_string(&ssh->exhash, s->pktout->data + 5, s->pktout->length - 5);
+    s->our_kexinitlen = s->pktout->length - 5;
+    s->our_kexinit = snewn(s->our_kexinitlen, unsigned char);
+    memcpy(s->our_kexinit, s->pktout->data + 5, s->our_kexinitlen); 
 
     ssh2_pkt_send_noqueue(ssh, s->pktout);
 
     if (!pktin)
 	crWaitUntil(pktin);
-    if (pktin->length > 5)
-	sha_string(&ssh->exhash, pktin->data + 5, pktin->length - 5);
 
     /*
      * Now examine the other side's KEXINIT to see what we're up
@@ -5211,13 +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;
-		if (in_commasep_string(k->name, str, len))
-		    ssh->kex = k;
+		for (j = 0; j < k->nkexes; j++) {
+		    if (!preferred) preferred = k->list[j]->name;
+		    if (in_commasep_string(k->list[j]->name, str, len)) {
+			ssh->kex = k->list[j];
+			break;
+		    }
+		}
 	    }
 	    if (ssh->kex)
 		break;
@@ -5340,8 +5376,8 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
 	    }
 	    ssh_set_frozen(ssh, 0);
 	    if (s->dlgret == 0) {
-		ssh->close_expected = TRUE;
-		ssh_closing((Plug)ssh, NULL, 0, 0);
+		ssh_disconnect(ssh, "User aborted at kex warning", NULL,
+			       0, TRUE);
 		crStop(0);
 	    }
 	}
@@ -5365,8 +5401,8 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
 	    }
 	    ssh_set_frozen(ssh, 0);
 	    if (s->dlgret == 0) {
-		ssh->close_expected = TRUE;
-		ssh_closing((Plug)ssh, NULL, 0, 0);
+		ssh_disconnect(ssh, "User aborted at cipher warning", NULL,
+			       0, TRUE);
 		crStop(0);
 	    }
 	}
@@ -5390,12 +5426,22 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
 	    }
 	    ssh_set_frozen(ssh, 0);
 	    if (s->dlgret == 0) {
-		ssh->close_expected = TRUE;
-		ssh_closing((Plug)ssh, NULL, 0, 0);
+		ssh_disconnect(ssh, "User aborted at cipher warning", NULL,
+			       0, TRUE);
 		crStop(0);
 	    }
 	}
 
+	ssh->exhash = ssh->kex->hash->init();
+	hash_string(ssh->kex->hash, ssh->exhash, ssh->v_c, strlen(ssh->v_c));
+	hash_string(ssh->kex->hash, ssh->exhash, ssh->v_s, strlen(ssh->v_s));
+	hash_string(ssh->kex->hash, ssh->exhash,
+	    s->our_kexinit, s->our_kexinitlen);
+	sfree(s->our_kexinit);
+	if (pktin->length > 5)
+	    hash_string(ssh->kex->hash, ssh->exhash,
+		pktin->data + 5, pktin->length - 5);
+
 	if (s->ignorepkt) /* first_kex_packet_follows */
 	    crWaitUntil(pktin);                /* Ignore packet */
     }
@@ -5412,10 +5458,10 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
 	scbits = s->sccipher_tobe->keylen;
 	s->nbits = (csbits > scbits ? csbits : scbits);
     }
-    /* The keys only have 160-bit entropy, since they're based on
-     * a SHA-1 hash. So cap the key size at 160 bits. */
-    if (s->nbits > 160)
-	s->nbits = 160;
+    /* The keys only have hlen-bit entropy, since they're based on
+     * a hash. So cap the key size at hlen bits. */
+    if (s->nbits > ssh->kex->hash->hlen * 8)
+	s->nbits = ssh->kex->hash->hlen * 8;
 
     /*
      * If we're doing Diffie-Hellman group exchange, start by
@@ -5487,29 +5533,31 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
      * involve user interaction. */
     set_busy_status(ssh->frontend, BUSY_NOT);
 
-    sha_string(&ssh->exhash, s->hostkeydata, s->hostkeylen);
-    if (ssh->kex == &ssh_diffiehellman_gex) {
-	sha_uint32(&ssh->exhash, s->pbits);
-	sha_mpint(&ssh->exhash, s->p);
-	sha_mpint(&ssh->exhash, s->g);
+    hash_string(ssh->kex->hash, ssh->exhash, s->hostkeydata, s->hostkeylen);
+    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);
     }
-    sha_mpint(&ssh->exhash, s->e);
-    sha_mpint(&ssh->exhash, s->f);
-    sha_mpint(&ssh->exhash, s->K);
-    SHA_Final(&ssh->exhash, s->exchange_hash);
+    hash_mpint(ssh->kex->hash, ssh->exhash, s->e);
+    hash_mpint(ssh->kex->hash, ssh->exhash, s->f);
+    hash_mpint(ssh->kex->hash, ssh->exhash, s->K);
+    assert(ssh->kex->hash->hlen <= sizeof(s->exchange_hash));
+    ssh->kex->hash->final(ssh->exhash, s->exchange_hash);
 
     dh_cleanup(ssh->kex_ctx);
     ssh->kex_ctx = NULL;
 
 #if 0
     debug(("Exchange hash is:\n"));
-    dmemdump(s->exchange_hash, 20);
+    dmemdump(s->exchange_hash, ssh->kex->hash->hlen);
 #endif
 
     s->hkey = ssh->hostkey->newkey(s->hostkeydata, s->hostkeylen);
     if (!s->hkey ||
 	!ssh->hostkey->verifysig(s->hkey, s->sigdata, s->siglen,
-				 (char *)s->exchange_hash, 20)) {
+				 (char *)s->exchange_hash,
+				 ssh->kex->hash->hlen)) {
 	bombout(("Server's host key did not match the signature supplied"));
 	crStop(0);
     }
@@ -5539,8 +5587,8 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
     }
     ssh_set_frozen(ssh, 0);
     if (s->dlgret == 0) {
-        ssh->close_expected = TRUE;
-        ssh_closing((Plug)ssh, NULL, 0, 0);
+	ssh_disconnect(ssh, "User aborted at host key verification", NULL,
+		       0, TRUE);
         crStop(0);
     }
     if (!s->got_session_id) {     /* don't bother logging this in rekeys */
@@ -5557,8 +5605,11 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
      * authentication.
      */
     if (!s->got_session_id) {
+	assert(sizeof(s->exchange_hash) <= sizeof(ssh->v2_session_id));
 	memcpy(ssh->v2_session_id, s->exchange_hash,
 	       sizeof(s->exchange_hash));
+	ssh->v2_session_id_len = ssh->kex->hash->hlen;
+	assert(ssh->v2_session_id_len <= sizeof(ssh->v2_session_id));
 	s->got_session_id = TRUE;
     }
 
@@ -5594,11 +5645,11 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
      */
     {
 	unsigned char keyspace[40];
-	ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'C',keyspace);
+	ssh2_mkkey(ssh,s->K,s->exchange_hash,'C',keyspace);
 	ssh->cscipher->setkey(ssh->cs_cipher_ctx, keyspace);
-	ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'A',keyspace);
+	ssh2_mkkey(ssh,s->K,s->exchange_hash,'A',keyspace);
 	ssh->cscipher->setiv(ssh->cs_cipher_ctx, keyspace);
-	ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'E',keyspace);
+	ssh2_mkkey(ssh,s->K,s->exchange_hash,'E',keyspace);
 	ssh->csmac->setkey(ssh->cs_mac_ctx, keyspace);
     }
 
@@ -5652,11 +5703,11 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
      */
     {
 	unsigned char keyspace[40];
-	ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'D',keyspace);
+	ssh2_mkkey(ssh,s->K,s->exchange_hash,'D',keyspace);
 	ssh->sccipher->setkey(ssh->sc_cipher_ctx, keyspace);
-	ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'B',keyspace);
+	ssh2_mkkey(ssh,s->K,s->exchange_hash,'B',keyspace);
 	ssh->sccipher->setiv(ssh->sc_cipher_ctx, keyspace);
-	ssh2_mkkey(ssh,s->K,s->exchange_hash,ssh->v2_session_id,'F',keyspace);
+	ssh2_mkkey(ssh,s->K,s->exchange_hash,'F',keyspace);
 	ssh->scmac->setkey(ssh->sc_mac_ctx, keyspace);
     }
     logeventf(ssh, "Initialised %.200s server->client encryption",
@@ -5672,7 +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);
     }
@@ -5706,7 +5757,7 @@ static int do_ssh2_transport(Ssh ssh, void *vin, int inlen,
      * it would only confuse the layer above.
      */
     if (s->activated_authconn) {
-	crReturn(1);
+	crReturn(0);
     }
     s->activated_authconn = TRUE;
 
@@ -6021,8 +6072,6 @@ static void ssh2_msg_channel_close(Ssh ssh, struct Packet *pktin)
      * not running in -N mode.)
      */
     if (!ssh->cfg.ssh_no_shell && count234(ssh->channels) == 0) {
-	logevent("All channels closed. Disconnecting");
-#if 0
 	/*
 	 * We used to send SSH_MSG_DISCONNECT here,
 	 * because I'd believed that _every_ conforming
@@ -6034,14 +6083,7 @@ static void ssh2_msg_channel_close(Ssh ssh, struct Packet *pktin)
 	 * this is more polite than sending a
 	 * DISCONNECT. So now we don't.
 	 */
-	s->pktout = ssh2_pkt_init(SSH2_MSG_DISCONNECT);
-	ssh2_pkt_adduint32(s->pktout, SSH2_DISCONNECT_BY_APPLICATION);
-	ssh2_pkt_addstring(s->pktout, "All open channels closed");
-	ssh2_pkt_addstring(s->pktout, "en");	/* language tag */
-	ssh2_pkt_send_noqueue(ssh, s->pktout);
-#endif
-	ssh->close_expected = TRUE;
-	ssh_closing((Plug)ssh, NULL, 0, 0);
+	ssh_disconnect(ssh, "All channels closed", NULL, 0, TRUE);
     }
 }
 
@@ -6128,18 +6170,10 @@ static void ssh2_msg_channel_request(Ssh ssh, struct Packet *pktin)
      */
     c = find234(ssh->channels, &localid, ssh_channelfind);
     if (!c) {
-	char buf[80];
-	sprintf(buf, "Received channel request for nonexistent"
-		" channel %d", localid);
-	logevent(buf);
-	pktout = ssh2_pkt_init(SSH2_MSG_DISCONNECT);
-	ssh2_pkt_adduint32(pktout, SSH2_DISCONNECT_BY_APPLICATION);
-	ssh2_pkt_addstring(pktout, buf);
-	ssh2_pkt_addstring(pktout, "en");	/* language tag */
-	ssh2_pkt_send_noqueue(ssh, pktout);
-	connection_fatal(ssh->frontend, "%s", buf);
-	ssh->close_expected = TRUE;
-	ssh_closing((Plug)ssh, NULL, 0, 0);
+	char *buf = dupprintf("Received channel request for nonexistent"
+			      " channel %d", localid);
+	ssh_disconnect(ssh, NULL, buf, SSH2_DISCONNECT_PROTOCOL_ERROR, FALSE);
+	sfree(buf);
 	return;
     }
 
@@ -6349,7 +6383,7 @@ static void ssh2_msg_channel_open(Ssh ssh, struct Packet *pktin)
 	    }
 	}
     } else if (typelen == 22 &&
-	       !memcmp(type, "auth-agent@openssh.com", 3)) {
+	       !memcmp(type, "auth-agent@openssh.com", 22)) {
 	if (!ssh->agentfwd_enabled)
 	    error = "Agent forwarding is not enabled";
 	else {
@@ -6548,9 +6582,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 		     * get_line failed to get a username.
 		     * Terminate.
 		     */
-		    logevent("No username provided. Abandoning session.");
-		    ssh->close_expected = TRUE;
-                    ssh_closing((Plug)ssh, NULL, 0, 0);
+		    ssh_disconnect(ssh, "No username provided", NULL, 0, TRUE);
 		    crStopV;
 		}
 	    } else {
@@ -6858,7 +6890,8 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 			ssh2_pkt_addstring_start(s->pktout);
 			ssh2_pkt_addstring_data(s->pktout, s->pkblob, s->pklen);
 
-			s->siglen = s->pktout->length - 5 + 4 + 20;
+			s->siglen = s->pktout->length - 5 + 4 +
+			    ssh->v2_session_id_len;
                         if (ssh->remote_bugs & BUG_SSH2_PK_SESSIONID)
                             s->siglen -= 4;
 			s->len = 1;       /* message type */
@@ -6877,11 +6910,12 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 			s->q += 4;
 			/* Now the data to be signed... */
                         if (!(ssh->remote_bugs & BUG_SSH2_PK_SESSIONID)) {
-                            PUT_32BIT(s->q, 20);
+                            PUT_32BIT(s->q, ssh->v2_session_id_len);
                             s->q += 4;
                         }
-			memcpy(s->q, ssh->v2_session_id, 20);
-			s->q += 20;
+			memcpy(s->q, ssh->v2_session_id,
+			       ssh->v2_session_id_len);
+			s->q += ssh->v2_session_id_len;
 			memcpy(s->q, s->pktout->data + 5,
 			       s->pktout->length - 5);
 			s->q += s->pktout->length - 5;
@@ -7101,17 +7135,9 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 			 * command line which has already failed to
 			 * work). Terminate.
 			 */
-			s->pktout = ssh2_pkt_init(SSH2_MSG_DISCONNECT);
-			ssh2_pkt_adduint32(s->pktout,SSH2_DISCONNECT_BY_APPLICATION);
-			ssh2_pkt_addstring(s->pktout, "No more passwords available"
-					   " to try");
-			ssh2_pkt_addstring(s->pktout, "en");	/* language tag */
-			ssh2_pkt_send_noqueue(ssh, s->pktout);
-			logevent("Unable to authenticate");
-			connection_fatal(ssh->frontend,
-					 "Unable to authenticate");
-			ssh->close_expected = TRUE;
-                        ssh_closing((Plug)ssh, NULL, 0, 0);
+			ssh_disconnect(ssh, NULL, "Unable to authenticate",
+				       SSH2_DISCONNECT_AUTH_CANCELLED_BY_USER,
+				       FALSE);
 			crStopV;
 		    }
 		} else {
@@ -7185,16 +7211,19 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 		     * followed by everything so far placed in the
 		     * outgoing packet.
 		     */
-		    sigdata_len = s->pktout->length - 5 + 4 + 20;
+		    sigdata_len = s->pktout->length - 5 + 4 +
+			ssh->v2_session_id_len;
                     if (ssh->remote_bugs & BUG_SSH2_PK_SESSIONID)
                         sigdata_len -= 4;
 		    sigdata = snewn(sigdata_len, unsigned char);
                     p = 0;
                     if (!(ssh->remote_bugs & BUG_SSH2_PK_SESSIONID)) {
-                        PUT_32BIT(sigdata+p, 20);
+                        PUT_32BIT(sigdata+p, ssh->v2_session_id_len);
                         p += 4;
                     }
-		    memcpy(sigdata+p, ssh->v2_session_id, 20); p += 20;
+		    memcpy(sigdata+p, ssh->v2_session_id,
+			   ssh->v2_session_id_len);
+		    p += ssh->v2_session_id_len;
 		    memcpy(sigdata+p, s->pktout->data + 5,
 			   s->pktout->length - 5);
                     p += s->pktout->length - 5;
@@ -7262,18 +7291,10 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 		}
 		s->type = AUTH_TYPE_KEYBOARD_INTERACTIVE;
 	    } else {
-		c_write_str(ssh, "No supported authentication methods"
-			    " left to try!\r\n");
-		logevent("No supported authentications offered."
-			 " Disconnecting");
-		s->pktout = ssh2_pkt_init(SSH2_MSG_DISCONNECT);
-		ssh2_pkt_adduint32(s->pktout, SSH2_DISCONNECT_BY_APPLICATION);
-		ssh2_pkt_addstring(s->pktout, "No supported authentication"
-				   " methods available");
-		ssh2_pkt_addstring(s->pktout, "en");	/* language tag */
-		ssh2_pkt_send_noqueue(ssh, s->pktout);
-		ssh->close_expected = TRUE;
-                ssh_closing((Plug)ssh, NULL, 0, 0);
+		ssh_disconnect(ssh, NULL,
+			       "No supported authentication methods available",
+			       SSH2_DISCONNECT_NO_MORE_AUTH_METHODS_AVAILABLE,
+			       FALSE);
 		crStopV;
 	    }
 	}
@@ -7847,6 +7868,7 @@ static const char *ssh_init(void *frontend_handle, void **backend_handle,
     ssh->hostkey = NULL;
     ssh->exitcode = -1;
     ssh->close_expected = FALSE;
+    ssh->clean_exit = FALSE;
     ssh->state = SSH_STATE_PREPACKET;
     ssh->size_needed = FALSE;
     ssh->eof_needed = FALSE;
@@ -7872,6 +7894,8 @@ static const char *ssh_init(void *frontend_handle, void **backend_handle,
     ssh->do_ssh1_login_state = NULL;
     ssh->do_ssh2_transport_state = NULL;
     ssh->do_ssh2_authconn_state = NULL;
+    ssh->v_c = NULL;
+    ssh->v_s = NULL;
     ssh->mainchan = NULL;
     ssh->throttled_all = 0;
     ssh->v1_stdout_throttling = 0;
@@ -7999,6 +8023,8 @@ static void ssh_free(void *handle)
     sfree(ssh->do_ssh1_login_state);
     sfree(ssh->do_ssh2_transport_state);
     sfree(ssh->do_ssh2_authconn_state);
+    sfree(ssh->v_c);
+    sfree(ssh->v_s);
     if (ssh->crcda_ctx) {
 	crcda_free_context(ssh->crcda_ctx);
 	ssh->crcda_ctx = NULL;
@@ -8024,7 +8050,8 @@ static void ssh_reconfig(void *handle, Config *cfg)
     unsigned long old_max_data_size;
 
     pinger_reconfig(ssh->pinger, &ssh->cfg, cfg);
-    ssh_setup_portfwd(ssh, cfg);
+    if (ssh->portfwds)
+	ssh_setup_portfwd(ssh, cfg);
 
     if (ssh->cfg.ssh_rekey_time != cfg->ssh_rekey_time &&
 	cfg->ssh_rekey_time != 0) {
@@ -8071,7 +8098,7 @@ static void ssh_reconfig(void *handle, Config *cfg)
 }
 
 /*
- * Called to send data down the Telnet connection.
+ * Called to send data down the SSH connection.
  */
 static int ssh_send(void *handle, char *buf, int len)
 {
@@ -8228,7 +8255,7 @@ static const struct telnet_special *ssh_get_specials(void *handle)
 }
 
 /*
- * Send Telnet special codes. TS_EOF is useful for `plink', so you
+ * Send special codes. TS_EOF is useful for `plink', so you
  * can send an EOF and collect resulting output (e.g. `plink
  * hostname sort').
  */