X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=blobdiff_plain;f=ssh.c;h=616b87d3220f124f8bf6bdc0fdf705dc21bd06ae;hb=89da2ddf564a93414ee9ab2df3f053608094e417;hp=bc079e91754b8f6df64a61e7a973b42bc1f15e2c;hpb=fb14d1e1b8dce3c2610894ff0a8f84f73f835c43;p=PuTTY.git

diff --git a/ssh.c b/ssh.c
index bc079e91..616b87d3 100644
--- a/ssh.c
+++ b/ssh.c
@@ -77,6 +77,10 @@ static const char *const ssh2_disconnect_reasons[] = {
 #define BUG_CHOKES_ON_SSH2_IGNORE               512
 #define BUG_CHOKES_ON_WINADJ                   1024
 #define BUG_SENDS_LATE_REQUEST_REPLY           2048
+#define BUG_SSH2_OLDGEX                        4096
+
+#define DH_MIN_SIZE 1024
+#define DH_MAX_SIZE 8192
 
 /*
  * Codes for terminal modes.
@@ -185,7 +189,7 @@ static unsigned int ssh_tty_parse_boolean(char *s)
 #define translate(x) if (type == x) return #x
 #define translatek(x,ctx) if (type == x && (pkt_kctx == ctx)) return #x
 #define translatea(x,ctx) if (type == x && (pkt_actx == ctx)) return #x
-static char *ssh1_pkt_type(int type)
+static const char *ssh1_pkt_type(int type)
 {
     translate(SSH1_MSG_DISCONNECT);
     translate(SSH1_SMSG_PUBLIC_KEY);
@@ -230,7 +234,8 @@ static char *ssh1_pkt_type(int type)
     translate(SSH1_CMSG_AUTH_CCARD_RESPONSE);
     return "unknown";
 }
-static char *ssh2_pkt_type(Pkt_KCtx pkt_kctx, Pkt_ACtx pkt_actx, int type)
+static const char *ssh2_pkt_type(Pkt_KCtx pkt_kctx, Pkt_ACtx pkt_actx,
+                                 int type)
 {
     translatea(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE,SSH2_PKTCTX_GSSAPI);
     translatea(SSH2_MSG_USERAUTH_GSSAPI_TOKEN,SSH2_PKTCTX_GSSAPI);
@@ -248,6 +253,7 @@ static char *ssh2_pkt_type(Pkt_KCtx pkt_kctx, Pkt_ACtx pkt_actx, int type)
     translate(SSH2_MSG_NEWKEYS);
     translatek(SSH2_MSG_KEXDH_INIT, SSH2_PKTCTX_DHGROUP);
     translatek(SSH2_MSG_KEXDH_REPLY, SSH2_PKTCTX_DHGROUP);
+    translatek(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD, SSH2_PKTCTX_DHGEX);
     translatek(SSH2_MSG_KEX_DH_GEX_REQUEST, SSH2_PKTCTX_DHGEX);
     translatek(SSH2_MSG_KEX_DH_GEX_GROUP, SSH2_PKTCTX_DHGEX);
     translatek(SSH2_MSG_KEX_DH_GEX_INIT, SSH2_PKTCTX_DHGEX);
@@ -352,9 +358,9 @@ static void ssh2_pkt_addmp(struct Packet *, Bignum b);
 static int ssh2_pkt_construct(Ssh, struct Packet *);
 static void ssh2_pkt_send(Ssh, struct Packet *);
 static void ssh2_pkt_send_noqueue(Ssh, struct Packet *);
-static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
+static int do_ssh1_login(Ssh ssh, const unsigned char *in, int inlen,
 			 struct Packet *pktin);
-static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
+static void do_ssh2_authconn(Ssh ssh, const unsigned char *in, int inlen,
 			     struct Packet *pktin);
 static void ssh2_channel_check_close(struct ssh_channel *c);
 static void ssh_channel_destroy(struct ssh_channel *c);
@@ -401,6 +407,7 @@ static void ssh_channel_destroy(struct ssh_channel *c);
 #define OUR_V2_PACKETLIMIT 0x9000UL
 
 const static struct ssh_signkey *hostkey_algs[] = {
+    &ssh_ecdsa_ed25519,
     &ssh_ecdsa_nistp256, &ssh_ecdsa_nistp384, &ssh_ecdsa_nistp521,
     &ssh_rsa, &ssh_dss
 };
@@ -680,11 +687,11 @@ struct Packet {
     const char *additional_log_text;
 };
 
-static void ssh1_protocol(Ssh ssh, void *vin, int inlen,
+static void ssh1_protocol(Ssh ssh, const void *vin, int inlen,
 			  struct Packet *pktin);
-static void ssh2_protocol(Ssh ssh, void *vin, int inlen,
+static void ssh2_protocol(Ssh ssh, const void *vin, int inlen,
 			  struct Packet *pktin);
-static void ssh2_bare_connection_protocol(Ssh ssh, void *vin, int inlen,
+static void ssh2_bare_connection_protocol(Ssh ssh, const void *vin, int inlen,
                                           struct Packet *pktin);
 static void ssh1_protocol_setup(Ssh ssh);
 static void ssh2_protocol_setup(Ssh ssh);
@@ -692,7 +699,8 @@ static void ssh2_bare_connection_protocol_setup(Ssh ssh);
 static void ssh_size(void *handle, int width, int height);
 static void ssh_special(void *handle, Telnet_Special);
 static int ssh2_try_send(struct ssh_channel *c);
-static void ssh2_add_channel_data(struct ssh_channel *c, char *buf, int len);
+static void ssh2_add_channel_data(struct ssh_channel *c,
+                                  const char *buf, int len);
 static void ssh_throttle_all(Ssh ssh, int enable, int bufsize);
 static void ssh2_set_window(struct ssh_channel *c, int newwin);
 static int ssh_sendbuffer(void *handle);
@@ -701,7 +709,7 @@ static unsigned long ssh_pkt_getuint32(struct Packet *pkt);
 static int ssh2_pkt_getbool(struct Packet *pkt);
 static void ssh_pkt_getstring(struct Packet *pkt, char **p, int *length);
 static void ssh2_timer(void *ctx, unsigned long now);
-static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
+static void do_ssh2_transport(Ssh ssh, const void *vin, int inlen,
 			      struct Packet *pktin);
 static void ssh2_msg_unexpected(Ssh ssh, struct Packet *pktin);
 
@@ -763,6 +771,7 @@ struct ssh_tag {
     const struct ssh2_cipher *cscipher, *sccipher;
     void *cs_cipher_ctx, *sc_cipher_ctx;
     const struct ssh_mac *csmac, *scmac;
+    int csmac_etm, scmac_etm;
     void *cs_mac_ctx, *sc_mac_ctx;
     const struct ssh_compress *cscomp, *sccomp;
     void *cs_comp_ctx, *sc_comp_ctx;
@@ -857,9 +866,10 @@ struct ssh_tag {
     /* SSH-1 and SSH-2 use this for different things, but both use it */
     int protocol_initial_phase_done;
 
-    void (*protocol) (Ssh ssh, void *vin, int inlen,
+    void (*protocol) (Ssh ssh, const void *vin, int inlen,
 		      struct Packet *pkt);
-    struct Packet *(*s_rdpkt) (Ssh ssh, unsigned char **data, int *datalen);
+    struct Packet *(*s_rdpkt) (Ssh ssh, const unsigned char **data,
+                               int *datalen);
     int (*do_ssh_init)(Ssh ssh, unsigned char c);
 
     /*
@@ -929,7 +939,7 @@ struct ssh_tag {
     unsigned long max_data_size;
     int kex_in_progress;
     unsigned long next_rekey, last_rekey;
-    char *deferred_rekey_reason;    /* points to STATIC string; don't free */
+    const char *deferred_rekey_reason;
 
     /*
      * Fully qualified host name, which we need if doing GSSAPI.
@@ -1287,7 +1297,8 @@ static void ssh1_log_outgoing_packet(Ssh ssh, struct Packet *pkt)
  * Update the *data and *datalen variables.
  * Return a Packet structure when a packet is completed.
  */
-static struct Packet *ssh1_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
+static struct Packet *ssh1_rdpkt(Ssh ssh, const unsigned char **data,
+                                 int *datalen)
 {
     struct rdpkt1_state_tag *st = &ssh->rdpkt1_state;
 
@@ -1542,7 +1553,8 @@ static void ssh2_log_outgoing_packet(Ssh ssh, struct Packet *pkt)
     pkt->length += (pkt->body - pkt->data);
 }
 
-static struct Packet *ssh2_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
+static struct Packet *ssh2_rdpkt(Ssh ssh, const unsigned char **data,
+                                 int *datalen)
 {
     struct rdpkt2_state_tag *st = &ssh->rdpkt2_state;
 
@@ -1561,7 +1573,7 @@ static struct Packet *ssh2_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
     st->maclen = ssh->scmac ? ssh->scmac->len : 0;
 
     if (ssh->sccipher && (ssh->sccipher->flags & SSH_CIPHER_IS_CBC) &&
-	ssh->scmac) {
+	ssh->scmac && !ssh->scmac_etm) {
 	/*
 	 * When dealing with a CBC-mode cipher, we want to avoid the
 	 * possibility of an attacker's tweaking the ciphertext stream
@@ -1573,6 +1585,11 @@ static struct Packet *ssh2_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
 	 * length, so we just read data and check the MAC repeatedly,
 	 * and when the MAC passes, see if the length we've got is
 	 * plausible.
+         *
+         * This defence is unnecessary in OpenSSH ETM mode, because
+         * the whole point of ETM mode is that the attacker can't
+         * tweak the ciphertext stream at all without the MAC
+         * detecting it before we decrypt anything.
 	 */
 
 	/* May as well allocate the whole lot now. */
@@ -1627,6 +1644,71 @@ static struct Packet *ssh2_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
 	st->pktin->data = sresize(st->pktin->data,
 				  st->pktin->maxlen + APIEXTRA,
 				  unsigned char);
+    } else if (ssh->scmac && ssh->scmac_etm) {
+	st->pktin->data = snewn(4 + APIEXTRA, unsigned char);
+
+        /*
+         * OpenSSH encrypt-then-MAC mode: the packet length is
+         * unencrypted.
+         */
+	for (st->i = st->len = 0; st->i < 4; st->i++) {
+	    while ((*datalen) == 0)
+		crReturn(NULL);
+	    st->pktin->data[st->i] = *(*data)++;
+	    (*datalen)--;
+	}
+	st->len = toint(GET_32BIT(st->pktin->data));
+
+	/*
+	 * _Completely_ silly lengths should be stomped on before they
+	 * do us any more damage.
+	 */
+	if (st->len < 0 || st->len > OUR_V2_PACKETLIMIT ||
+	    st->len % st->cipherblk != 0) {
+	    bombout(("Incoming packet length field was garbled"));
+	    ssh_free_packet(st->pktin);
+	    crStop(NULL);
+	}
+
+	/*
+	 * So now we can work out the total packet length.
+	 */
+	st->packetlen = st->len + 4;
+
+	/*
+	 * Allocate memory for the rest of the packet.
+	 */
+	st->pktin->maxlen = st->packetlen + st->maclen;
+	st->pktin->data = sresize(st->pktin->data,
+				  st->pktin->maxlen + APIEXTRA,
+				  unsigned char);
+
+	/*
+	 * Read the remainder of the packet.
+	 */
+	for (st->i = 4; st->i < st->packetlen + st->maclen; st->i++) {
+	    while ((*datalen) == 0)
+		crReturn(NULL);
+	    st->pktin->data[st->i] = *(*data)++;
+	    (*datalen)--;
+	}
+
+	/*
+	 * Check the MAC.
+	 */
+	if (ssh->scmac
+	    && !ssh->scmac->verify(ssh->sc_mac_ctx, st->pktin->data,
+				   st->len + 4, st->incoming_sequence)) {
+	    bombout(("Incorrect MAC received on packet"));
+	    ssh_free_packet(st->pktin);
+	    crStop(NULL);
+	}
+
+	/* Decrypt everything between the length field and the MAC. */
+	if (ssh->sccipher)
+	    ssh->sccipher->decrypt(ssh->sc_cipher_ctx,
+				   st->pktin->data + 4,
+				   st->packetlen - 4);
     } else {
 	st->pktin->data = snewn(st->cipherblk + APIEXTRA, unsigned char);
 
@@ -1760,7 +1842,8 @@ static struct Packet *ssh2_rdpkt(Ssh ssh, unsigned char **data, int *datalen)
     crFinish(st->pktin);
 }
 
-static struct Packet *ssh2_bare_connection_rdpkt(Ssh ssh, unsigned char **data,
+static struct Packet *ssh2_bare_connection_rdpkt(Ssh ssh,
+                                                 const unsigned char **data,
                                                  int *datalen)
 {
     struct rdpkt2_bare_state_tag *st = &ssh->rdpkt2_bare_state;
@@ -1973,7 +2056,7 @@ static void defer_packet(Ssh ssh, int pkttype, ...)
     s_wrpkt_defer(ssh, pkt);
 }
 
-static int ssh_versioncmp(char *a, char *b)
+static int ssh_versioncmp(const char *a, const char *b)
 {
     char *ae, *be;
     unsigned long av, bv;
@@ -2050,17 +2133,16 @@ static void ssh_pkt_addstring_start(struct Packet *pkt)
     ssh_pkt_adduint32(pkt, 0);
     pkt->savedpos = pkt->length;
 }
-static void ssh_pkt_addstring_str(struct Packet *pkt, const char *data)
-{
-    ssh_pkt_adddata(pkt, data, strlen(data));
-    PUT_32BIT(pkt->data + pkt->savedpos - 4, pkt->length - pkt->savedpos);
-}
 static void ssh_pkt_addstring_data(struct Packet *pkt, const char *data,
                                    int len)
 {
     ssh_pkt_adddata(pkt, data, len);
     PUT_32BIT(pkt->data + pkt->savedpos - 4, pkt->length - pkt->savedpos);
 }
+static void ssh_pkt_addstring_str(struct Packet *pkt, const char *data)
+{
+  ssh_pkt_addstring_data(pkt, data, strlen(data));
+}
 static void ssh_pkt_addstring(struct Packet *pkt, const char *data)
 {
     ssh_pkt_addstring_start(pkt);
@@ -2141,7 +2223,7 @@ static struct Packet *ssh2_pkt_init(int pkt_type)
  */
 static int ssh2_pkt_construct(Ssh ssh, struct Packet *pkt)
 {
-    int cipherblk, maclen, padding, i;
+    int cipherblk, maclen, padding, unencrypted_prefix, i;
 
     if (ssh->logctx)
         ssh2_log_outgoing_packet(ssh, pkt);
@@ -2182,10 +2264,12 @@ static int ssh2_pkt_construct(Ssh ssh, struct Packet *pkt)
     cipherblk = ssh->cscipher ? ssh->cscipher->blksize : 8;  /* block size */
     cipherblk = cipherblk < 8 ? 8 : cipherblk;	/* or 8 if blksize < 8 */
     padding = 4;
+    unencrypted_prefix = (ssh->csmac && ssh->csmac_etm) ? 4 : 0;
     if (pkt->length + padding < pkt->forcepad)
 	padding = pkt->forcepad - pkt->length;
     padding +=
-	(cipherblk - (pkt->length + padding) % cipherblk) % cipherblk;
+	(cipherblk - (pkt->length - unencrypted_prefix + padding) % cipherblk)
+        % cipherblk;
     assert(padding <= 255);
     maclen = ssh->csmac ? ssh->csmac->len : 0;
     ssh2_pkt_ensure(pkt, pkt->length + padding + maclen);
@@ -2193,16 +2277,30 @@ static int ssh2_pkt_construct(Ssh ssh, struct Packet *pkt)
     for (i = 0; i < padding; i++)
 	pkt->data[pkt->length + i] = random_byte();
     PUT_32BIT(pkt->data, pkt->length + padding - 4);
-    if (ssh->csmac)
-	ssh->csmac->generate(ssh->cs_mac_ctx, pkt->data,
-			     pkt->length + padding,
-			     ssh->v2_outgoing_sequence);
-    ssh->v2_outgoing_sequence++;       /* whether or not we MACed */
-
-    if (ssh->cscipher)
-	ssh->cscipher->encrypt(ssh->cs_cipher_ctx,
-			       pkt->data, pkt->length + padding);
+    if (ssh->csmac && ssh->csmac_etm) {
+        /*
+         * OpenSSH-defined encrypt-then-MAC protocol.
+         */
+        if (ssh->cscipher)
+            ssh->cscipher->encrypt(ssh->cs_cipher_ctx,
+                                   pkt->data + 4, pkt->length + padding - 4);
+        ssh->csmac->generate(ssh->cs_mac_ctx, pkt->data,
+                             pkt->length + padding,
+                             ssh->v2_outgoing_sequence);
+    } else {
+        /*
+         * SSH-2 standard protocol.
+         */
+        if (ssh->csmac)
+            ssh->csmac->generate(ssh->cs_mac_ctx, pkt->data,
+                                 pkt->length + padding,
+                                 ssh->v2_outgoing_sequence);
+        if (ssh->cscipher)
+            ssh->cscipher->encrypt(ssh->cs_cipher_ctx,
+                                   pkt->data, pkt->length + padding);
+    }
 
+    ssh->v2_outgoing_sequence++;       /* whether or not we MACed */
     pkt->encrypted_len = pkt->length + padding;
 
     /* Ready-to-send packet starts at pkt->data. We return length. */
@@ -2535,7 +2633,7 @@ static void *ssh_pkt_getdata(struct Packet *pkt, int length)
     return pkt->body + (pkt->savedpos - length);
 }
 static int ssh1_pkt_getrsakey(struct Packet *pkt, struct RSAKey *key,
-			      unsigned char **keystr)
+			      const unsigned char **keystr)
 {
     int j;
 
@@ -2811,6 +2909,18 @@ static void ssh_detect_bugs(Ssh ssh, char *vstring)
 	logevent("We believe remote version has SSH-2 ignore bug");
     }
 
+    if (conf_get_int(ssh->conf, CONF_sshbug_oldgex2) == FORCE_ON ||
+	(conf_get_int(ssh->conf, CONF_sshbug_oldgex2) == AUTO &&
+	 (wc_match("OpenSSH_2.[235]*", imp)))) {
+	/*
+	 * These versions only support the original (pre-RFC4419)
+	 * SSH-2 GEX request, and disconnect with a protocol error if
+	 * we use the newer version.
+	 */
+	ssh->remote_bugs |= BUG_SSH2_OLDGEX;
+	logevent("We believe remote version has outdated SSH-2 GEX");
+    }
+
     if (conf_get_int(ssh->conf, CONF_sshbug_winadj) == FORCE_ON) {
 	/*
 	 * Servers that don't support our winadj request for one
@@ -2823,11 +2933,15 @@ static void ssh_detect_bugs(Ssh ssh, char *vstring)
     if (conf_get_int(ssh->conf, CONF_sshbug_chanreq) == FORCE_ON ||
 	(conf_get_int(ssh->conf, CONF_sshbug_chanreq) == AUTO &&
 	 (wc_match("OpenSSH_[2-5].*", imp) ||
-	  wc_match("OpenSSH_6.[0-6]*", imp)))) {
+	  wc_match("OpenSSH_6.[0-6]*", imp) ||
+	  wc_match("dropbear_0.[2-4][0-9]*", imp) ||
+	  wc_match("dropbear_0.5[01]*", imp)))) {
 	/*
-	 * These versions have the SSH-2 channel request bug. 6.7 and
-	 * above do not:
+	 * These versions have the SSH-2 channel request bug.
+	 * OpenSSH 6.7 and above do not:
 	 * https://bugzilla.mindrot.org/show_bug.cgi?id=1818
+	 * dropbear_0.52 and above do not:
+	 * https://secure.ucc.asn.au/hg/dropbear/rev/cd02449b709c
 	 */
 	ssh->remote_bugs |= BUG_SENDS_LATE_REQUEST_REPLY;
 	logevent("We believe remote version has SSH-2 channel request bug");
@@ -2966,11 +3080,13 @@ static int do_ssh_init(Ssh ssh, unsigned char c)
     s->proto2 = ssh_versioncmp(s->version, "1.99") >= 0;
 
     if (conf_get_int(ssh->conf, CONF_sshprot) == 0 && !s->proto1) {
-	bombout(("SSH protocol version 1 required by user but not provided by server"));
+	bombout(("SSH protocol version 1 required by configuration but "
+		 "not provided by server"));
 	crStop(0);
     }
     if (conf_get_int(ssh->conf, CONF_sshprot) == 3 && !s->proto2) {
-	bombout(("SSH protocol version 2 required by user but not provided by server"));
+	bombout(("SSH protocol version 2 required by configuration but "
+		 "not provided by server"));
 	crStop(0);
     }
 
@@ -3133,7 +3249,7 @@ static int do_ssh_connection_init(Ssh ssh, unsigned char c)
 }
 
 static void ssh_process_incoming_data(Ssh ssh,
-				      unsigned char **data, int *datalen)
+				      const unsigned char **data, int *datalen)
 {
     struct Packet *pktin;
 
@@ -3145,7 +3261,7 @@ static void ssh_process_incoming_data(Ssh ssh,
 }
 
 static void ssh_queue_incoming_data(Ssh ssh,
-				    unsigned char **data, int *datalen)
+				    const unsigned char **data, int *datalen)
 {
     bufchain_add(&ssh->queued_incoming_data, *data, *datalen);
     *data += *datalen;
@@ -3155,7 +3271,7 @@ static void ssh_queue_incoming_data(Ssh ssh,
 static void ssh_process_queued_incoming_data(Ssh ssh)
 {
     void *vdata;
-    unsigned char *data;
+    const unsigned char *data;
     int len, origlen;
 
     while (!ssh->frozen && bufchain_size(&ssh->queued_incoming_data)) {
@@ -3178,7 +3294,7 @@ static void ssh_set_frozen(Ssh ssh, int frozen)
     ssh->frozen = frozen;
 }
 
-static void ssh_gotdata(Ssh ssh, unsigned char *data, int datalen)
+static void ssh_gotdata(Ssh ssh, const unsigned char *data, int datalen)
 {
     /* Log raw data, if we're in that mode. */
     if (ssh->logctx)
@@ -3291,6 +3407,14 @@ static int ssh_do_close(Ssh ssh, int notify_exit)
 	ssh->portfwds = NULL;
     }
 
+    /*
+     * Also stop attempting to connection-share.
+     */
+    if (ssh->connshare) {
+        sharestate_free(ssh->connshare);
+        ssh->connshare = NULL;
+    }
+
     return ret;
 }
 
@@ -3415,7 +3539,7 @@ static void ssh_sent(Plug plug, int bufsize)
  * Also places the canonical host name into `realhost'. It must be
  * freed by the caller.
  */
-static const char *connect_to_host(Ssh ssh, char *host, int port,
+static const char *connect_to_host(Ssh ssh, const char *host, int port,
 				   char **realhost, int nodelay, int keepalive)
 {
     static const struct plug_function_table fn_table = {
@@ -3622,7 +3746,7 @@ static void ssh_agentf_callback(void *cv, void *reply, int replylen)
 {
     struct ssh_channel *c = (struct ssh_channel *)cv;
     Ssh ssh = c->ssh;
-    void *sentreply = reply;
+    const void *sentreply = reply;
 
     c->u.a.outstanding_requests--;
     if (!sentreply) {
@@ -3655,7 +3779,8 @@ static void ssh_agentf_callback(void *cv, void *reply, int replylen)
  * 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,
+static void ssh_disconnect(Ssh ssh, const char *client_reason,
+                           const char *wire_reason,
 			   int code, int clean_exit)
 {
     char *error;
@@ -3739,7 +3864,7 @@ int verify_ssh_manual_host_key(Ssh ssh, const char *fingerprint,
 /*
  * Handle the key exchange and user authentication phases.
  */
-static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
+static int do_ssh1_login(Ssh ssh, const unsigned char *in, int inlen,
 			 struct Packet *pktin)
 {
     int i, j, ret;
@@ -3748,7 +3873,8 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
     struct do_ssh1_login_state {
 	int crLine;
 	int len;
-	unsigned char *rsabuf, *keystr1, *keystr2;
+	unsigned char *rsabuf;
+        const unsigned char *keystr1, *keystr2;
 	unsigned long supported_ciphers_mask, supported_auths_mask;
 	int tried_publickey, tried_agent;
 	int tis_auth_refused, ccard_auth_refused;
@@ -3757,7 +3883,7 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
 	void *publickey_blob;
 	int publickey_bloblen;
 	char *publickey_comment;
-	int publickey_encrypted;
+	int privatekey_available, privatekey_encrypted;
 	prompts_t *cur_prompt;
 	char c;
 	int pwpkt_type;
@@ -3863,6 +3989,7 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
         s->dlgret = verify_ssh_manual_host_key(ssh, fingerprint, NULL, NULL);
         if (s->dlgret == 0) {          /* did not match */
             bombout(("Host key did not appear in manually configured list"));
+            sfree(keystr);
             crStop(0);
         } else if (s->dlgret < 0) { /* none configured; use standard handling */
             ssh_set_frozen(ssh, 1);
@@ -3889,6 +4016,8 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
                                NULL, 0, TRUE);
                 crStop(0);
             }
+        } else {
+            sfree(keystr);
         }
     }
 
@@ -3916,7 +4045,7 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
 
     {
 	int cipher_chosen = 0, warn = 0;
-	char *cipher_string = NULL;
+	const char *cipher_string = NULL;
 	int i;
 	for (i = 0; !cipher_chosen && i < CIPHER_MAX; i++) {
 	    int next_cipher = conf_get_int_int(ssh->conf,
@@ -4088,20 +4217,24 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
     s->keyfile = conf_get_filename(ssh->conf, CONF_keyfile);
     if (!filename_is_null(s->keyfile)) {
 	int keytype;
-	logeventf(ssh, "Reading private key file \"%.150s\"",
+	logeventf(ssh, "Reading key file \"%.150s\"",
 		  filename_to_str(s->keyfile));
 	keytype = key_type(s->keyfile);
-	if (keytype == SSH_KEYTYPE_SSH1) {
+	if (keytype == SSH_KEYTYPE_SSH1 ||
+            keytype == SSH_KEYTYPE_SSH1_PUBLIC) {
 	    const char *error;
 	    if (rsakey_pubblob(s->keyfile,
 			       &s->publickey_blob, &s->publickey_bloblen,
 			       &s->publickey_comment, &error)) {
-		s->publickey_encrypted = rsakey_encrypted(s->keyfile,
-							  NULL);
+                s->privatekey_available = (keytype == SSH_KEYTYPE_SSH1);
+                if (!s->privatekey_available)
+                    logeventf(ssh, "Key file contains public key only");
+		s->privatekey_encrypted = rsakey_encrypted(s->keyfile,
+                                                           NULL);
 	    } else {
 		char *msgbuf;
-		logeventf(ssh, "Unable to load private key (%s)", error);
-		msgbuf = dupprintf("Unable to load private key file "
+		logeventf(ssh, "Unable to load key (%s)", error);
+		msgbuf = dupprintf("Unable to load key file "
 				   "\"%.150s\" (%s)\r\n",
 				   filename_to_str(s->keyfile),
 				   error);
@@ -4309,7 +4442,8 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
 	    if (s->authed)
 		break;
 	}
-	if (s->publickey_blob && !s->tried_publickey) {
+	if (s->publickey_blob && s->privatekey_available &&
+            !s->tried_publickey) {
 	    /*
 	     * Try public key authentication with the specified
 	     * key file.
@@ -4328,7 +4462,7 @@ static int do_ssh1_login(Ssh ssh, unsigned char *in, int inlen,
 		 */
 		char *passphrase = NULL;    /* only written after crReturn */
 		const char *error;
-		if (!s->publickey_encrypted) {
+		if (!s->privatekey_encrypted) {
 		    if (flags & FLAG_VERBOSE)
 			c_write_str(ssh, "No passphrase required.\r\n");
 		    passphrase = NULL;
@@ -5646,7 +5780,7 @@ int ssh_agent_forwarding_permitted(Ssh ssh)
     return conf_get_int(ssh->conf, CONF_agentfwd) && agent_exists();
 }
 
-static void do_ssh1_connection(Ssh ssh, unsigned char *in, int inlen,
+static void do_ssh1_connection(Ssh ssh, const unsigned char *in, int inlen,
 			       struct Packet *pktin)
 {
     crBegin(ssh->do_ssh1_connection_crstate);
@@ -5819,7 +5953,7 @@ static void do_ssh1_connection(Ssh ssh, unsigned char *in, int inlen,
 	ssh_special(ssh, TS_EOF);
 
     if (ssh->ldisc)
-	ldisc_send(ssh->ldisc, NULL, 0, 0);/* cause ldisc to notice changes */
+	ldisc_echoedit_update(ssh->ldisc);  /* cause ldisc to notice changes */
     ssh->send_ok = 1;
     ssh->channels = newtree234(ssh_channelcmp);
     while (1) {
@@ -5901,10 +6035,10 @@ static void ssh1_protocol_setup(Ssh ssh)
     ssh->packet_dispatch[SSH1_MSG_DEBUG] = ssh1_msg_debug;
 }
 
-static void ssh1_protocol(Ssh ssh, void *vin, int inlen,
+static void ssh1_protocol(Ssh ssh, const void *vin, int inlen,
 			  struct Packet *pktin)
 {
-    unsigned char *in=(unsigned char*)vin;
+    const unsigned char *in = (const unsigned char *)vin;
     if (ssh->state == SSH_STATE_CLOSED)
 	return;
 
@@ -6022,10 +6156,10 @@ static void ssh2_mkkey(Ssh ssh, Bignum K, unsigned char *H, char chr,
 /*
  * Handle the SSH-2 transport layer.
  */
-static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
+static void do_ssh2_transport(Ssh ssh, const void *vin, int inlen,
 			     struct Packet *pktin)
 {
-    unsigned char *in = (unsigned char *)vin;
+    const unsigned char *in = (const unsigned char *)vin;
     struct do_ssh2_transport_state {
 	int crLine;
 	int nbits, pbits, warn_kex, warn_cscipher, warn_sccipher;
@@ -6039,6 +6173,7 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
 	const struct ssh2_cipher *sccipher_tobe;
 	const struct ssh_mac *csmac_tobe;
 	const struct ssh_mac *scmac_tobe;
+        int csmac_etm_tobe, scmac_etm_tobe;
 	const struct ssh_compress *cscomp_tobe;
 	const struct ssh_compress *sccomp_tobe;
 	char *hostkeydata, *sigdata, *rsakeydata, *keystr, *fingerprint;
@@ -6222,8 +6357,15 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
 	/* 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++)
+	    for (i = 0; i < s->nmacs; i++) {
 		ssh2_pkt_addstring_commasep(s->pktout, s->maclist[i]->name);
+            }
+	    for (i = 0; i < s->nmacs; i++) {
+                /* For each MAC, there may also be an ETM version,
+                 * which we list second. */
+                if (s->maclist[i]->etm_name)
+                    ssh2_pkt_addstring_commasep(s->pktout, s->maclist[i]->etm_name);
+            }
 	}
 	/* List client->server compression algorithms,
 	 * then server->client compression algorithms. (We use the
@@ -6270,7 +6412,8 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
      * to.
      */
     {
-	char *str, *preferred;
+	char *str;
+        const char *preferred;
 	int i, j, len;
 
 	if (pktin->type != SSH2_MSG_KEXINIT) {
@@ -6401,9 +6544,25 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
 	for (i = 0; i < s->nmacs; i++) {
 	    if (in_commasep_string(s->maclist[i]->name, str, len)) {
 		s->csmac_tobe = s->maclist[i];
-		break;
+		s->csmac_etm_tobe = FALSE;
+                break;
 	    }
 	}
+        if (!s->csmac_tobe) {
+            for (i = 0; i < s->nmacs; i++) {
+                if (s->maclist[i]->etm_name &&
+                    in_commasep_string(s->maclist[i]->etm_name, str, len)) {
+                    s->csmac_tobe = s->maclist[i];
+                    s->csmac_etm_tobe = TRUE;
+                    break;
+                }
+            }
+        }
+        if (!s->csmac_tobe) {
+            bombout(("Couldn't agree a client-to-server MAC"
+                     " (available: %.*s)", len, str));
+	    crStopV;
+        }
 	ssh_pkt_getstring(pktin, &str, &len);    /* server->client mac */
         if (!str) {
             bombout(("KEXINIT packet was incomplete"));
@@ -6412,9 +6571,25 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
 	for (i = 0; i < s->nmacs; i++) {
 	    if (in_commasep_string(s->maclist[i]->name, str, len)) {
 		s->scmac_tobe = s->maclist[i];
-		break;
+		s->scmac_etm_tobe = FALSE;
+                break;
 	    }
 	}
+        if (!s->scmac_tobe) {
+            for (i = 0; i < s->nmacs; i++) {
+                if (s->maclist[i]->etm_name &&
+                    in_commasep_string(s->maclist[i]->etm_name, str, len)) {
+                    s->scmac_tobe = s->maclist[i];
+                    s->scmac_etm_tobe = TRUE;
+                    break;
+                }
+            }
+        }
+        if (!s->scmac_tobe) {
+            bombout(("Couldn't agree a server-to-client MAC"
+                     " (available: %.*s)", len, str));
+	    crStopV;
+        }
 	ssh_pkt_getstring(pktin, &str, &len);  /* client->server compression */
         if (!str) {
             bombout(("KEXINIT packet was incomplete"));
@@ -6573,7 +6748,7 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
          * If we're doing Diffie-Hellman group exchange, start by
          * requesting a group.
          */
-        if (!ssh->kex->pdata) {
+        if (dh_is_gex(ssh->kex)) {
             logevent("Doing Diffie-Hellman group exchange");
             ssh->pkt_kctx = SSH2_PKTCTX_DHGEX;
             /*
@@ -6581,8 +6756,19 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
              * much data.
              */
             s->pbits = 512 << ((s->nbits - 1) / 64);
-            s->pktout = ssh2_pkt_init(SSH2_MSG_KEX_DH_GEX_REQUEST);
-            ssh2_pkt_adduint32(s->pktout, s->pbits);
+            if (s->pbits < DH_MIN_SIZE)
+                s->pbits = DH_MIN_SIZE;
+            if (s->pbits > DH_MAX_SIZE)
+                s->pbits = DH_MAX_SIZE;
+            if ((ssh->remote_bugs & BUG_SSH2_OLDGEX)) {
+                s->pktout = ssh2_pkt_init(SSH2_MSG_KEX_DH_GEX_REQUEST_OLD);
+                ssh2_pkt_adduint32(s->pktout, s->pbits);
+            } else {
+                s->pktout = ssh2_pkt_init(SSH2_MSG_KEX_DH_GEX_REQUEST);
+                ssh2_pkt_adduint32(s->pktout, DH_MIN_SIZE);
+                ssh2_pkt_adduint32(s->pktout, s->pbits);
+                ssh2_pkt_adduint32(s->pktout, DH_MAX_SIZE);
+            }
             ssh2_pkt_send_noqueue(ssh, s->pktout);
 
             crWaitUntilV(pktin);
@@ -6627,7 +6813,8 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
         }
         set_busy_status(ssh->frontend, BUSY_CPU); /* cogitate */
         ssh_pkt_getstring(pktin, &s->hostkeydata, &s->hostkeylen);
-        s->hkey = ssh->hostkey->newkey(s->hostkeydata, s->hostkeylen);
+        s->hkey = ssh->hostkey->newkey(ssh->hostkey,
+                                       s->hostkeydata, s->hostkeylen);
         s->f = ssh2_pkt_getmp(pktin);
         if (!s->f) {
             bombout(("unable to parse key exchange reply packet"));
@@ -6635,6 +6822,13 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
         }
         ssh_pkt_getstring(pktin, &s->sigdata, &s->siglen);
 
+        {
+            const char *err = dh_validate_f(ssh->kex_ctx, s->f);
+            if (err) {
+                bombout(("key exchange reply failed validation: %s", err));
+                crStopV;
+            }
+        }
         s->K = dh_find_K(ssh->kex_ctx, s->f);
 
         /* We assume everything from now on will be quick, and it might
@@ -6642,8 +6836,12 @@ static void 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->pdata) {
+        if (dh_is_gex(ssh->kex)) {
+            if (!(ssh->remote_bugs & BUG_SSH2_OLDGEX))
+                hash_uint32(ssh->kex->hash, ssh->exhash, DH_MIN_SIZE);
             hash_uint32(ssh->kex->hash, ssh->exhash, s->pbits);
+            if (!(ssh->remote_bugs & BUG_SSH2_OLDGEX))
+                hash_uint32(ssh->kex->hash, ssh->exhash, DH_MAX_SIZE);
             hash_mpint(ssh->kex->hash, ssh->exhash, s->p);
             hash_mpint(ssh->kex->hash, ssh->exhash, s->g);
         }
@@ -6652,7 +6850,7 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
 
         dh_cleanup(ssh->kex_ctx);
         freebn(s->f);
-        if (!ssh->kex->pdata) {
+        if (dh_is_gex(ssh->kex)) {
             freebn(s->g);
             freebn(s->p);
         }
@@ -6662,14 +6860,7 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
                   ssh->kex->hash->text_name);
         ssh->pkt_kctx = SSH2_PKTCTX_ECDHKEX;
 
-        s->eckey = NULL;
-        if (!strcmp(ssh->kex->name, "ecdh-sha2-nistp256")) {
-            s->eckey = ssh_ecdhkex_newkey(ec_p256());
-        } else if (!strcmp(ssh->kex->name, "ecdh-sha2-nistp384")) {
-            s->eckey = ssh_ecdhkex_newkey(ec_p384());
-        } else if (!strcmp(ssh->kex->name, "ecdh-sha2-nistp521")) {
-            s->eckey = ssh_ecdhkex_newkey(ec_p521());
-        }
+        s->eckey = ssh_ecdhkex_newkey(ssh->kex);
         if (!s->eckey) {
             bombout(("Unable to generate key for ECDH"));
             crStopV;
@@ -6701,7 +6892,8 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
 
         ssh_pkt_getstring(pktin, &s->hostkeydata, &s->hostkeylen);
         hash_string(ssh->kex->hash, ssh->exhash, s->hostkeydata, s->hostkeylen);
-        s->hkey = ssh->hostkey->newkey(s->hostkeydata, s->hostkeylen);
+        s->hkey = ssh->hostkey->newkey(ssh->hostkey,
+                                       s->hostkeydata, s->hostkeylen);
 
         {
             char *publicPoint;
@@ -6750,7 +6942,8 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
         ssh_pkt_getstring(pktin, &s->hostkeydata, &s->hostkeylen);
         hash_string(ssh->kex->hash, ssh->exhash,
 		    s->hostkeydata, s->hostkeylen);
-	s->hkey = ssh->hostkey->newkey(s->hostkeydata, s->hostkeylen);
+	s->hkey = ssh->hostkey->newkey(ssh->hostkey,
+                                       s->hostkeydata, s->hostkeylen);
 
         {
             char *keydata;
@@ -6860,7 +7053,7 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
          * Authenticate remote host: verify host key. (We've already
          * checked the signature of the exchange hash.)
          */
-        s->fingerprint = ssh->hostkey->fingerprint(s->hkey);
+        s->fingerprint = ssh2_fingerprint(ssh->hostkey, s->hkey);
         logevent("Host key fingerprint is:");
         logevent(s->fingerprint);
         /* First check against manually configured host keys. */
@@ -6948,6 +7141,7 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
     if (ssh->cs_mac_ctx)
 	ssh->csmac->free_context(ssh->cs_mac_ctx);
     ssh->csmac = s->csmac_tobe;
+    ssh->csmac_etm = s->csmac_etm_tobe;
     ssh->cs_mac_ctx = ssh->csmac->make_context();
 
     if (ssh->cs_comp_ctx)
@@ -6979,8 +7173,9 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
 
     logeventf(ssh, "Initialised %.200s client->server encryption",
 	      ssh->cscipher->text_name);
-    logeventf(ssh, "Initialised %.200s client->server MAC algorithm",
-	      ssh->csmac->text_name);
+    logeventf(ssh, "Initialised %.200s client->server MAC algorithm%s",
+	      ssh->csmac->text_name,
+              ssh->csmac_etm ? " (in ETM mode)" : "");
     if (ssh->cscomp->text_name)
 	logeventf(ssh, "Initialised %s compression",
 		  ssh->cscomp->text_name);
@@ -7014,6 +7209,7 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
     if (ssh->sc_mac_ctx)
 	ssh->scmac->free_context(ssh->sc_mac_ctx);
     ssh->scmac = s->scmac_tobe;
+    ssh->scmac_etm = s->scmac_etm_tobe;
     ssh->sc_mac_ctx = ssh->scmac->make_context();
 
     if (ssh->sc_comp_ctx)
@@ -7044,8 +7240,9 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
     }
     logeventf(ssh, "Initialised %.200s server->client encryption",
 	      ssh->sccipher->text_name);
-    logeventf(ssh, "Initialised %.200s server->client MAC algorithm",
-	      ssh->scmac->text_name);
+    logeventf(ssh, "Initialised %.200s server->client MAC algorithm%s",
+	      ssh->scmac->text_name,
+              ssh->scmac_etm ? " (in ETM mode)" : "");
     if (ssh->sccomp->text_name)
 	logeventf(ssh, "Initialised %s decompression",
 		  ssh->sccomp->text_name);
@@ -7165,7 +7362,7 @@ static void do_ssh2_transport(Ssh ssh, void *vin, int inlen,
 /*
  * Add data to an SSH-2 channel output buffer.
  */
-static void ssh2_add_channel_data(struct ssh_channel *c, char *buf,
+static void ssh2_add_channel_data(struct ssh_channel *c, const char *buf,
 				  int len)
 {
     bufchain_add(&c->v.v2.outbuffer, buf, len);
@@ -7272,7 +7469,8 @@ static void ssh2_channel_init(struct ssh_channel *c)
 /*
  * Construct the common parts of a CHANNEL_OPEN.
  */
-static struct Packet *ssh2_chanopen_init(struct ssh_channel *c, char *type)
+static struct Packet *ssh2_chanopen_init(struct ssh_channel *c,
+                                         const char *type)
 {
     struct Packet *pktout;
 
@@ -7319,7 +7517,8 @@ static void ssh2_queue_chanreq_handler(struct ssh_channel *c,
  * the server initiated channel closure before we saw the response)
  * and the handler should free any storage it's holding.
  */
-static struct Packet *ssh2_chanreq_init(struct ssh_channel *c, char *type,
+static struct Packet *ssh2_chanreq_init(struct ssh_channel *c,
+                                        const char *type,
 					cchandler_fn_t handler, void *ctx)
 {
     struct Packet *pktout;
@@ -8029,7 +8228,7 @@ static void ssh2_msg_channel_request(Ssh ssh, struct Packet *pktin)
 		   !memcmp(type, "exit-signal", 11)) {
 
 	    int is_plausible = TRUE, is_int = FALSE;
-	    char *fmt_sig = "", *fmt_msg = "";
+            char *fmt_sig = NULL, *fmt_msg = NULL;
 	    char *msg;
 	    int msglen = 0, core = FALSE;
 	    /* ICK: older versions of OpenSSH (e.g. 3.4p1)
@@ -8152,10 +8351,11 @@ static void ssh2_msg_channel_request(Ssh ssh, struct Packet *pktin)
 		/* ignore lang tag */
 	    } /* else don't attempt to parse */
 	    logeventf(ssh, "Server exited on signal%s%s%s",
-		      fmt_sig, core ? " (core dumped)" : "",
-		      fmt_msg);
-	    if (*fmt_sig) sfree(fmt_sig);
-	    if (*fmt_msg) sfree(fmt_msg);
+		      fmt_sig ? fmt_sig : "",
+                      core ? " (core dumped)" : "",
+		      fmt_msg ? fmt_msg : "");
+	    sfree(fmt_sig);
+            sfree(fmt_msg);
 	    reply = SSH2_MSG_CHANNEL_SUCCESS;
 
 	}
@@ -8227,7 +8427,7 @@ static void ssh2_msg_channel_open(Ssh ssh, struct Packet *pktin)
     char *peeraddr;
     int peeraddrlen;
     int peerport;
-    char *error = NULL;
+    const char *error = NULL;
     struct ssh_channel *c;
     unsigned remid, winsize, pktsize;
     unsigned our_winsize_override = 0;
@@ -8640,7 +8840,7 @@ static void ssh2_response_authconn(struct ssh_channel *c, struct Packet *pktin,
         do_ssh2_authconn(c->ssh, NULL, 0, pktin);
 }
 
-static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
+static void do_ssh2_authconn(Ssh ssh, const unsigned char *in, int inlen,
 			     struct Packet *pktin)
 {
     struct do_ssh2_authconn_state {
@@ -8671,7 +8871,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 	int got_username;
 	void *publickey_blob;
 	int publickey_bloblen;
-	int publickey_encrypted;
+	int privatekey_available, privatekey_encrypted;
 	char *publickey_algorithm;
 	char *publickey_comment;
 	unsigned char agent_request[5], *agent_response, *agentp;
@@ -8777,10 +8977,12 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 	s->keyfile = conf_get_filename(ssh->conf, CONF_keyfile);
 	if (!filename_is_null(s->keyfile)) {
 	    int keytype;
-	    logeventf(ssh, "Reading private key file \"%.150s\"",
+	    logeventf(ssh, "Reading key file \"%.150s\"",
 		      filename_to_str(s->keyfile));
 	    keytype = key_type(s->keyfile);
-	    if (keytype == SSH_KEYTYPE_SSH2) {
+	    if (keytype == SSH_KEYTYPE_SSH2 ||
+                keytype == SSH_KEYTYPE_SSH2_PUBLIC_RFC4716 ||
+                keytype == SSH_KEYTYPE_SSH2_PUBLIC_OPENSSH) {
 		const char *error;
 		s->publickey_blob =
 		    ssh2_userkey_loadpub(s->keyfile,
@@ -8788,13 +8990,16 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 					 &s->publickey_bloblen, 
 					 &s->publickey_comment, &error);
 		if (s->publickey_blob) {
-		    s->publickey_encrypted =
+		    s->privatekey_available = (keytype == SSH_KEYTYPE_SSH2);
+                    if (!s->privatekey_available)
+                        logeventf(ssh, "Key file contains public key only");
+		    s->privatekey_encrypted =
 			ssh2_userkey_encrypted(s->keyfile, NULL);
 		} else {
 		    char *msgbuf;
-		    logeventf(ssh, "Unable to load private key (%s)", 
+		    logeventf(ssh, "Unable to load key (%s)", 
 			      error);
-		    msgbuf = dupprintf("Unable to load private key file "
+		    msgbuf = dupprintf("Unable to load key file "
 				       "\"%.150s\" (%s)\r\n",
 				       filename_to_str(s->keyfile),
 				       error);
@@ -9308,7 +9513,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 		}
 
 	    } else if (s->can_pubkey && s->publickey_blob &&
-		       !s->tried_pubkey_config) {
+		       s->privatekey_available && !s->tried_pubkey_config) {
 
 		struct ssh2_userkey *key;   /* not live over crReturn */
 		char *passphrase;	    /* not live over crReturn */
@@ -9359,7 +9564,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 		key = NULL;
 		while (!key) {
 		    const char *error;  /* not live over crReturn */
-		    if (s->publickey_encrypted) {
+		    if (s->privatekey_encrypted) {
 			/*
 			 * Get a passphrase from the user.
 			 */
@@ -9483,6 +9688,8 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
                     logevent("Sent public key signature");
 		    s->type = AUTH_TYPE_PUBLICKEY;
 		    key->alg->freekey(key->data);
+                    sfree(key->comment);
+                    sfree(key);
 		}
 
 #ifndef NO_GSSAPI
@@ -9920,7 +10127,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 		    int prompt_len; /* not live over crReturn */
 		    
 		    {
-			char *msg;
+			const char *msg;
 			if (changereq_first_time)
 			    msg = "Server requested password change";
 			else
@@ -10082,6 +10289,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
 
     /* Clear up various bits and pieces from authentication. */
     if (s->publickey_blob) {
+	sfree(s->publickey_algorithm);
 	sfree(s->publickey_blob);
 	sfree(s->publickey_comment);
     }
@@ -10313,7 +10521,7 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen,
      * Transfer data!
      */
     if (ssh->ldisc)
-	ldisc_send(ssh->ldisc, NULL, 0, 0);/* cause ldisc to notice changes */
+	ldisc_echoedit_update(ssh->ldisc);  /* cause ldisc to notice changes */
     if (ssh->mainchan)
 	ssh->send_ok = 1;
     while (1) {
@@ -10543,10 +10751,10 @@ static void ssh2_timer(void *ctx, unsigned long now)
     }
 }
 
-static void ssh2_protocol(Ssh ssh, void *vin, int inlen,
+static void ssh2_protocol(Ssh ssh, const void *vin, int inlen,
 			  struct Packet *pktin)
 {
-    unsigned char *in = (unsigned char *)vin;
+    const unsigned char *in = (const unsigned char *)vin;
     if (ssh->state == SSH_STATE_CLOSED)
 	return;
 
@@ -10566,10 +10774,10 @@ static void ssh2_protocol(Ssh ssh, void *vin, int inlen,
 	do_ssh2_authconn(ssh, in, inlen, pktin);
 }
 
-static void ssh2_bare_connection_protocol(Ssh ssh, void *vin, int inlen,
+static void ssh2_bare_connection_protocol(Ssh ssh, const void *vin, int inlen,
                                           struct Packet *pktin)
 {
-    unsigned char *in = (unsigned char *)vin;
+    const unsigned char *in = (const unsigned char *)vin;
     if (ssh->state == SSH_STATE_CLOSED)
 	return;
 
@@ -10590,7 +10798,8 @@ static void ssh_cache_conf_values(Ssh ssh)
  * Returns an error message, or NULL on success.
  */
 static const char *ssh_init(void *frontend_handle, void **backend_handle,
-			    Conf *conf, char *host, int port, char **realhost,
+			    Conf *conf,
+                            const char *host, int port, char **realhost,
 			    int nodelay, int keepalive)
 {
     const char *p;
@@ -10665,6 +10874,8 @@ static const char *ssh_init(void *frontend_handle, void **backend_handle,
     ssh->sent_console_eof = FALSE;
     ssh->got_pty = FALSE;
     ssh->bare_connection = FALSE;
+    ssh->X11_fwd_enabled = FALSE;
+    ssh->connshare = NULL;
     ssh->attempting_connshare = FALSE;
 
     *backend_handle = ssh;
@@ -10840,7 +11051,8 @@ static void ssh_free(void *handle)
 static void ssh_reconfig(void *handle, Conf *conf)
 {
     Ssh ssh = (Ssh) handle;
-    char *rekeying = NULL, rekey_mandatory = FALSE;
+    const char *rekeying = NULL;
+    int rekey_mandatory = FALSE;
     unsigned long old_max_data_size;
     int i, rekey_time;
 
@@ -10905,14 +11117,14 @@ static void ssh_reconfig(void *handle, Conf *conf)
 /*
  * Called to send data down the SSH connection.
  */
-static int ssh_send(void *handle, char *buf, int len)
+static int ssh_send(void *handle, const char *buf, int len)
 {
     Ssh ssh = (Ssh) handle;
 
     if (ssh == NULL || ssh->s == NULL || ssh->protocol == NULL)
 	return 0;
 
-    ssh->protocol(ssh, (unsigned char *)buf, len, 0);
+    ssh->protocol(ssh, (const unsigned char *)buf, len, 0);
 
     return ssh_sendbuffer(ssh);
 }
@@ -11120,7 +11332,7 @@ static void ssh_special(void *handle, Telnet_Special code)
 	}
     } else {
 	/* Is is a POSIX signal? */
-	char *signame = NULL;
+	const char *signame = NULL;
 	if (code == TS_SIGABRT) signame = "ABRT";
 	if (code == TS_SIGALRM) signame = "ALRM";
 	if (code == TS_SIGFPE)  signame = "FPE";
@@ -11237,7 +11449,8 @@ static void ssh_unthrottle(void *handle, int bufsize)
     ssh_process_queued_incoming_data(ssh);
 }
 
-void ssh_send_port_open(void *channel, char *hostname, int port, char *org)
+void ssh_send_port_open(void *channel, const char *hostname, int port,
+                        const char *org)
 {
     struct ssh_channel *c = (struct ssh_channel *)channel;
     Ssh ssh = c->ssh;
@@ -11319,13 +11532,19 @@ static int ssh_return_exitcode(void *handle)
 }
 
 /*
- * cfg_info for SSH is the currently running version of the
- * protocol. (1 for 1; 2 for 2; 0 for not-decided-yet.)
+ * cfg_info for SSH is the protocol running in this session.
+ * (1 or 2 for the full SSH-1 or SSH-2 protocol; -1 for the bare
+ * SSH-2 connection protocol, i.e. a downstream; 0 for not-decided-yet.)
  */
 static int ssh_cfg_info(void *handle)
 {
     Ssh ssh = (Ssh) handle;
-    return ssh->version;
+    if (ssh->version == 0)
+	return 0; /* don't know yet */
+    else if (ssh->bare_connection)
+	return -1;
+    else
+	return ssh->version;
 }
 
 /*