1 files changed, 186 insertions, 0 deletions

diff --git a/kexgexs.c b/kexgexs.c
new file mode 100644
index 000000000..baebfcfb0
--- /dev/null
+++ b/kexgexs.c
@@ -0,0 +1,186 @@
+/*
+ * Copyright (c) 2000 Niels Provos.  All rights reserved.
+ * Copyright (c) 2001 Markus Friedl.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "includes.h"
+RCSID("$OpenBSD: kexgexs.c,v 1.1 2003/02/16 17:09:57 markus Exp $");
+
+#include "xmalloc.h"
+#include "key.h"
+#include "kex.h"
+#include "log.h"
+#include "packet.h"
+#include "dh.h"
+#include "ssh2.h"
+#include "compat.h"
+#include "monitor_wrap.h"
+
+void
+kexgex_server(Kex *kex)
+{
+        BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
+        Key *server_host_key;
+        DH *dh;
+        u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
+        u_int sbloblen, klen, kout, slen;
+        int min = -1, max = -1, nbits = -1, type;
+
+        if (kex->load_host_key == NULL)
+                fatal("Cannot load hostkey");
+        server_host_key = kex->load_host_key(kex->hostkey_type);
+        if (server_host_key == NULL)
+                fatal("Unsupported hostkey type %d", kex->hostkey_type);
+
+        type = packet_read();
+        switch (type) {
+        case SSH2_MSG_KEX_DH_GEX_REQUEST:
+                debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
+                min = packet_get_int();
+                nbits = packet_get_int();
+                max = packet_get_int();
+                min = MAX(DH_GRP_MIN, min);
+                max = MIN(DH_GRP_MAX, max);
+                break;
+        case SSH2_MSG_KEX_DH_GEX_REQUEST_OLD:
+                debug("SSH2_MSG_KEX_DH_GEX_REQUEST_OLD received");
+                nbits = packet_get_int();
+                min = DH_GRP_MIN;
+                max = DH_GRP_MAX;
+                /* unused for old GEX */
+                break;
+        default:
+                fatal("protocol error during kex, no DH_GEX_REQUEST: %d", type);
+        }
+        packet_check_eom();
+
+        if (max < min || nbits < min || max < nbits)
+                fatal("DH_GEX_REQUEST, bad parameters: %d !< %d !< %d",
+                    min, nbits, max);
+
+        /* Contact privileged parent */
+        dh = PRIVSEP(choose_dh(min, nbits, max));
+        if (dh == NULL)
+                packet_disconnect("Protocol error: no matching DH grp found");
+
+        debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
+        packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
+        packet_put_bignum2(dh->p);
+        packet_put_bignum2(dh->g);
+        packet_send();
+
+        /* flush */
+        packet_write_wait();
+
+        /* Compute our exchange value in parallel with the client */
+        dh_gen_key(dh, kex->we_need * 8);
+
+        debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
+        packet_read_expect(SSH2_MSG_KEX_DH_GEX_INIT);
+
+        /* key, cert */
+        if ((dh_client_pub = BN_new()) == NULL)
+                fatal("dh_client_pub == NULL");
+        packet_get_bignum2(dh_client_pub);
+        packet_check_eom();
+
+#ifdef DEBUG_KEXDH
+        fprintf(stderr, "dh_client_pub= ");
+        BN_print_fp(stderr, dh_client_pub);
+        fprintf(stderr, "\n");
+        debug("bits %d", BN_num_bits(dh_client_pub));
+#endif
+
+#ifdef DEBUG_KEXDH
+        DHparams_print_fp(stderr, dh);
+        fprintf(stderr, "pub= ");
+        BN_print_fp(stderr, dh->pub_key);
+        fprintf(stderr, "\n");
+#endif
+        if (!dh_pub_is_valid(dh, dh_client_pub))
+                packet_disconnect("bad client public DH value");
+
+        klen = DH_size(dh);
+        kbuf = xmalloc(klen);
+        kout = DH_compute_key(kbuf, dh_client_pub, dh);
+#ifdef DEBUG_KEXDH
+        dump_digest("shared secret", kbuf, kout);
+#endif
+        if ((shared_secret = BN_new()) == NULL)
+                fatal("kexgex_server: BN_new failed");
+        BN_bin2bn(kbuf, kout, shared_secret);
+        memset(kbuf, 0, klen);
+        xfree(kbuf);
+
+        key_to_blob(server_host_key, &server_host_key_blob, &sbloblen);
+
+        if (type == SSH2_MSG_KEX_DH_GEX_REQUEST_OLD)
+                min = max = -1;
+
+        /* calc H */                    /* XXX depends on 'kex' */
+        hash = kexgex_hash(
+            kex->client_version_string,
+            kex->server_version_string,
+            buffer_ptr(&kex->peer), buffer_len(&kex->peer),
+            buffer_ptr(&kex->my), buffer_len(&kex->my),
+            server_host_key_blob, sbloblen,
+            min, nbits, max,
+            dh->p, dh->g,
+            dh_client_pub,
+            dh->pub_key,
+            shared_secret
+        );
+        BN_clear_free(dh_client_pub);
+
+        /* save session id := H */
+        /* XXX hashlen depends on KEX */
+        if (kex->session_id == NULL) {
+                kex->session_id_len = 20;
+                kex->session_id = xmalloc(kex->session_id_len);
+                memcpy(kex->session_id, hash, kex->session_id_len);
+        }
+
+        /* sign H */
+        /* XXX hashlen depends on KEX */
+        PRIVSEP(key_sign(server_host_key, &signature, &slen, hash, 20));
+
+        /* destroy_sensitive_data(); */
+
+        /* send server hostkey, DH pubkey 'f' and singed H */
+        debug("SSH2_MSG_KEX_DH_GEX_REPLY sent");
+        packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
+        packet_put_string(server_host_key_blob, sbloblen);
+        packet_put_bignum2(dh->pub_key);        /* f */
+        packet_put_string(signature, slen);
+        packet_send();
+
+        xfree(signature);
+        xfree(server_host_key_blob);
+        /* have keys, free DH */
+        DH_free(dh);
+
+        kex_derive_keys(kex, hash, shared_secret);
+        BN_clear_free(shared_secret);
+
+        kex_finish(kex);
+}