- markus@cvs.openbsd.org 2003/02/16 17:09:57

     [kex.c kexdh.c kexgex.c kex.h sshconnect2.c sshd.c ssh-keyscan.c]
     split kex into client and server code, no need to link
     server code into the client; ok provos@

1 files changed, 138 insertions, 0 deletions

diff --git a/kexdhs.c b/kexdhs.c
new file mode 100644
index 00000000..f04bce82
--- /dev/null
+++ b/kexdhs.c
@@ -0,0 +1,138 @@
+/*
+ * 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: kexdhs.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 "monitor_wrap.h"
+
+void
+kexdh_server(Kex *kex)
+{
+	BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
+	DH *dh;
+	Key *server_host_key;
+	u_char *kbuf, *hash, *signature = NULL, *server_host_key_blob = NULL;
+	u_int sbloblen, klen, kout;
+	u_int slen;
+
+	/* generate server DH public key */
+	dh = dh_new_group1();
+	dh_gen_key(dh, kex->we_need * 8);
+
+	debug("expecting SSH2_MSG_KEXDH_INIT");
+	packet_read_expect(SSH2_MSG_KEXDH_INIT);
+
+	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);
+
+	/* 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("kexdh_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);
+
+	/* calc H */
+	hash = kex_dh_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,
+	    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 */
+	packet_start(SSH2_MSG_KEXDH_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);
+}