+ 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 */
+ }
+
+ if (ssh->kex->main_type == KEXTYPE_DH) {
+ /*
+ * Work out the number of bits of key we will need from the
+ * key exchange. We start with the maximum key length of
+ * either cipher...
+ */
+ {
+ int csbits, scbits;
+
+ csbits = s->cscipher_tobe->keylen;
+ scbits = s->sccipher_tobe->keylen;
+ s->nbits = (csbits > scbits ? csbits : scbits);
+ }
+ /* 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
+ * requesting a group.
+ */
+ if (!ssh->kex->pdata) {
+ logevent("Doing Diffie-Hellman group exchange");
+ ssh->pkt_kctx = SSH2_PKTCTX_DHGEX;
+ /*
+ * Work out how big a DH group we will need to allow that
+ * 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);
+ ssh2_pkt_send_noqueue(ssh, s->pktout);
+
+ crWaitUntil(pktin);
+ if (pktin->type != SSH2_MSG_KEX_DH_GEX_GROUP) {
+ bombout(("expected key exchange group packet from server"));
+ crStop(0);
+ }
+ s->p = ssh2_pkt_getmp(pktin);
+ s->g = ssh2_pkt_getmp(pktin);
+ if (!s->p || !s->g) {
+ bombout(("unable to read mp-ints from incoming group packet"));
+ crStop(0);
+ }
+ ssh->kex_ctx = dh_setup_gex(s->p, s->g);
+ s->kex_init_value = SSH2_MSG_KEX_DH_GEX_INIT;
+ s->kex_reply_value = SSH2_MSG_KEX_DH_GEX_REPLY;
+ } else {
+ ssh->pkt_kctx = SSH2_PKTCTX_DHGROUP;
+ ssh->kex_ctx = dh_setup_group(ssh->kex);
+ s->kex_init_value = SSH2_MSG_KEXDH_INIT;
+ s->kex_reply_value = SSH2_MSG_KEXDH_REPLY;
+ logeventf(ssh, "Using Diffie-Hellman with standard group \"%s\"",
+ ssh->kex->groupname);
+ }
+
+ logeventf(ssh, "Doing Diffie-Hellman key exchange with hash %s",
+ ssh->kex->hash->text_name);
+ /*
+ * Now generate and send e for Diffie-Hellman.
+ */
+ set_busy_status(ssh->frontend, BUSY_CPU); /* this can take a while */
+ s->e = dh_create_e(ssh->kex_ctx, s->nbits * 2);
+ s->pktout = ssh2_pkt_init(s->kex_init_value);
+ ssh2_pkt_addmp(s->pktout, s->e);
+ ssh2_pkt_send_noqueue(ssh, s->pktout);
+
+ set_busy_status(ssh->frontend, BUSY_WAITING); /* wait for server */
+ crWaitUntil(pktin);
+ if (pktin->type != s->kex_reply_value) {
+ bombout(("expected key exchange reply packet from server"));
+ crStop(0);
+ }
+ 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->f = ssh2_pkt_getmp(pktin);
+ if (!s->f) {
+ bombout(("unable to parse key exchange reply packet"));
+ crStop(0);
+ }
+ ssh_pkt_getstring(pktin, &s->sigdata, &s->siglen);
+
+ s->K = dh_find_K(ssh->kex_ctx, s->f);
+
+ /* We assume everything from now on will be quick, and it might
+ * involve user interaction. */
+ set_busy_status(ssh->frontend, BUSY_NOT);
+
+ 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);
+ }
+ hash_mpint(ssh->kex->hash, ssh->exhash, s->e);
+ hash_mpint(ssh->kex->hash, ssh->exhash, s->f);
+
+ dh_cleanup(ssh->kex_ctx);
+ freebn(s->f);
+ if (!ssh->kex->pdata) {
+ freebn(s->g);
+ freebn(s->p);
+ }
+ } else {
+ logeventf(ssh, "Doing RSA key exchange with hash %s",
+ ssh->kex->hash->text_name);
+ ssh->pkt_kctx = SSH2_PKTCTX_RSAKEX;
+ /*
+ * RSA key exchange. First expect a KEXRSA_PUBKEY packet
+ * from the server.
+ */
+ crWaitUntil(pktin);
+ if (pktin->type != SSH2_MSG_KEXRSA_PUBKEY) {
+ bombout(("expected RSA public key packet from server"));
+ crStop(0);
+ }
+
+ 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);
+
+ {
+ char *keydata;
+ ssh_pkt_getstring(pktin, &keydata, &s->rsakeylen);
+ s->rsakeydata = snewn(s->rsakeylen, char);
+ memcpy(s->rsakeydata, keydata, s->rsakeylen);
+ }
+
+ s->rsakey = ssh_rsakex_newkey(s->rsakeydata, s->rsakeylen);
+ if (!s->rsakey) {
+ sfree(s->rsakeydata);
+ bombout(("unable to parse RSA public key from server"));
+ crStop(0);
+ }
+
+ hash_string(ssh->kex->hash, ssh->exhash, s->rsakeydata, s->rsakeylen);
+
+ /*
+ * Next, set up a shared secret K, of precisely KLEN -
+ * 2*HLEN - 49 bits, where KLEN is the bit length of the
+ * RSA key modulus and HLEN is the bit length of the hash
+ * we're using.
+ */
+ {
+ int klen = ssh_rsakex_klen(s->rsakey);
+ int nbits = klen - (2*ssh->kex->hash->hlen*8 + 49);
+ int i, byte = 0;
+ unsigned char *kstr1, *kstr2, *outstr;
+ int kstr1len, kstr2len, outstrlen;
+
+ s->K = bn_power_2(nbits - 1);
+
+ for (i = 0; i < nbits; i++) {
+ if ((i & 7) == 0) {
+ byte = random_byte();
+ }
+ bignum_set_bit(s->K, i, (byte >> (i & 7)) & 1);
+ }
+
+ /*
+ * Encode this as an mpint.
+ */
+ kstr1 = ssh2_mpint_fmt(s->K, &kstr1len);
+ kstr2 = snewn(kstr2len = 4 + kstr1len, unsigned char);
+ PUT_32BIT(kstr2, kstr1len);
+ memcpy(kstr2 + 4, kstr1, kstr1len);
+
+ /*
+ * Encrypt it with the given RSA key.
+ */
+ outstrlen = (klen + 7) / 8;
+ outstr = snewn(outstrlen, unsigned char);
+ ssh_rsakex_encrypt(ssh->kex->hash, kstr2, kstr2len,
+ outstr, outstrlen, s->rsakey);
+
+ /*
+ * And send it off in a return packet.
+ */
+ s->pktout = ssh2_pkt_init(SSH2_MSG_KEXRSA_SECRET);
+ ssh2_pkt_addstring_start(s->pktout);
+ ssh2_pkt_addstring_data(s->pktout, (char *)outstr, outstrlen);
+ ssh2_pkt_send_noqueue(ssh, s->pktout);
+
+ hash_string(ssh->kex->hash, ssh->exhash, outstr, outstrlen);
+
+ sfree(kstr2);
+ sfree(kstr1);
+ sfree(outstr);
+ }
+
+ ssh_rsakex_freekey(s->rsakey);
+
+ crWaitUntil(pktin);
+ if (pktin->type != SSH2_MSG_KEXRSA_DONE) {
+ sfree(s->rsakeydata);
+ bombout(("expected signature packet from server"));
+ crStop(0);
+ }
+
+ ssh_pkt_getstring(pktin, &s->sigdata, &s->siglen);
+
+ sfree(s->rsakeydata);
+ }
+
+ 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);