1 files changed, 256 insertions, 0 deletions
diff --git a/kexgexs.c b/kexgexs.c
new file mode 100644
index 0000000..dc9c0bc
--- /dev/null
+++ b/kexgexs.c
@@ -0,0 +1,256 @@
+/* $OpenBSD: kexgexs.c,v 1.35 2018/10/04 00:04:41 djm Exp $ */
+/*
+ * 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"
+
+#ifdef WITH_OPENSSL
+
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <string.h>
+#include <signal.h>
+
+#include <openssl/dh.h>
+
+#include "openbsd-compat/openssl-compat.h"
+
+#include "sshkey.h"
+#include "cipher.h"
+#include "digest.h"
+#include "kex.h"
+#include "log.h"
+#include "packet.h"
+#include "dh.h"
+#include "ssh2.h"
+#include "compat.h"
+#ifdef GSSAPI
+#include "ssh-gss.h"
+#endif
+#include "monitor_wrap.h"
+#include "dispatch.h"
+#include "ssherr.h"
+#include "sshbuf.h"
+#include "misc.h"
+
+static int input_kex_dh_gex_request(int, u_int32_t, struct ssh *);
+static int input_kex_dh_gex_init(int, u_int32_t, struct ssh *);
+
+int
+kexgex_server(struct ssh *ssh)
+{
+	ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_REQUEST,
+	    &input_kex_dh_gex_request);
+	debug("expecting SSH2_MSG_KEX_DH_GEX_REQUEST");
+	return 0;
+}
+
+static int
+input_kex_dh_gex_request(int type, u_int32_t seq, struct ssh *ssh)
+{
+	struct kex *kex = ssh->kex;
+	int r;
+	u_int min = 0, max = 0, nbits = 0;
+	const BIGNUM *dh_p, *dh_g;
+
+	debug("SSH2_MSG_KEX_DH_GEX_REQUEST received");
+	if ((r = sshpkt_get_u32(ssh, &min)) != 0 ||
+	    (r = sshpkt_get_u32(ssh, &nbits)) != 0 ||
+	    (r = sshpkt_get_u32(ssh, &max)) != 0 ||
+	    (r = sshpkt_get_end(ssh)) != 0)
+		goto out;
+	kex->nbits = nbits;
+	kex->min = min;
+	kex->max = max;
+	min = MAXIMUM(DH_GRP_MIN, min);
+	max = MINIMUM(DH_GRP_MAX, max);
+	nbits = MAXIMUM(DH_GRP_MIN, nbits);
+	nbits = MINIMUM(DH_GRP_MAX, nbits);
+
+	if (kex->max < kex->min || kex->nbits < kex->min ||
+	    kex->max < kex->nbits || kex->max < DH_GRP_MIN) {
+		r = SSH_ERR_DH_GEX_OUT_OF_RANGE;
+		goto out;
+	}
+
+	/* Contact privileged parent */
+	kex->dh = PRIVSEP(choose_dh(min, nbits, max));
+	if (kex->dh == NULL) {
+		sshpkt_disconnect(ssh, "no matching DH grp found");
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	debug("SSH2_MSG_KEX_DH_GEX_GROUP sent");
+	DH_get0_pqg(kex->dh, &dh_p, NULL, &dh_g);
+	if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_GROUP)) != 0 ||
+	    (r = sshpkt_put_bignum2(ssh, dh_p)) != 0 ||
+	    (r = sshpkt_put_bignum2(ssh, dh_g)) != 0 ||
+	    (r = sshpkt_send(ssh)) != 0)
+		goto out;
+
+	/* Compute our exchange value in parallel with the client */
+	if ((r = dh_gen_key(kex->dh, kex->we_need * 8)) != 0)
+		goto out;
+
+	debug("expecting SSH2_MSG_KEX_DH_GEX_INIT");
+	ssh_dispatch_set(ssh, SSH2_MSG_KEX_DH_GEX_INIT, &input_kex_dh_gex_init);
+	r = 0;
+ out:
+	return r;
+}
+
+static int
+input_kex_dh_gex_init(int type, u_int32_t seq, struct ssh *ssh)
+{
+	struct kex *kex = ssh->kex;
+	BIGNUM *shared_secret = NULL, *dh_client_pub = NULL;
+	const BIGNUM *pub_key, *dh_p, *dh_g;
+	struct sshkey *server_host_public, *server_host_private;
+	u_char *kbuf = NULL, *signature = NULL, *server_host_key_blob = NULL;
+	u_char hash[SSH_DIGEST_MAX_LENGTH];
+	size_t sbloblen, slen;
+	size_t klen = 0, hashlen;
+	int kout, r;
+
+	if (kex->load_host_public_key == NULL ||
+	    kex->load_host_private_key == NULL) {
+		r = SSH_ERR_INVALID_ARGUMENT;
+		goto out;
+	}
+	server_host_public = kex->load_host_public_key(kex->hostkey_type,
+	    kex->hostkey_nid, ssh);
+	server_host_private = kex->load_host_private_key(kex->hostkey_type,
+	    kex->hostkey_nid, ssh);
+	if (server_host_public == NULL) {
+		r = SSH_ERR_NO_HOSTKEY_LOADED;
+		goto out;
+	}
+
+	/* key, cert */
+	if ((dh_client_pub = BN_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((r = sshpkt_get_bignum2(ssh, dh_client_pub)) != 0 ||
+	    (r = sshpkt_get_end(ssh)) != 0)
+		goto out;
+
+	DH_get0_key(kex->dh, &pub_key, NULL);
+	DH_get0_pqg(kex->dh, &dh_p, NULL, &dh_g);
+
+#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));
+	DHparams_print_fp(stderr, kex->dh);
+	fprintf(stderr, "pub= ");
+	BN_print_fp(stderr, pub_key);
+	fprintf(stderr, "\n");
+#endif
+	if (!dh_pub_is_valid(kex->dh, dh_client_pub)) {
+		sshpkt_disconnect(ssh, "bad client public DH value");
+		r = SSH_ERR_MESSAGE_INCOMPLETE;
+		goto out;
+	}
+
+	klen = DH_size(kex->dh);
+	if ((kbuf = malloc(klen)) == NULL ||
+	    (shared_secret = BN_new()) == NULL) {
+		r = SSH_ERR_ALLOC_FAIL;
+		goto out;
+	}
+	if ((kout = DH_compute_key(kbuf, dh_client_pub, kex->dh)) < 0 ||
+	    BN_bin2bn(kbuf, kout, shared_secret) == NULL) {
+		r = SSH_ERR_LIBCRYPTO_ERROR;
+		goto out;
+	}
+#ifdef DEBUG_KEXDH
+	dump_digest("shared secret", kbuf, kout);
+#endif
+	if ((r = sshkey_to_blob(server_host_public, &server_host_key_blob,
+	    &sbloblen)) != 0)
+		goto out;
+	/* calc H */
+	hashlen = sizeof(hash);
+	if ((r = kexgex_hash(
+	    kex->hash_alg,
+	    kex->client_version_string,
+	    kex->server_version_string,
+	    sshbuf_ptr(kex->peer), sshbuf_len(kex->peer),
+	    sshbuf_ptr(kex->my), sshbuf_len(kex->my),
+	    server_host_key_blob, sbloblen,
+	    kex->min, kex->nbits, kex->max,
+	    dh_p, dh_g,
+	    dh_client_pub,
+	    pub_key,
+	    shared_secret,
+	    hash, &hashlen)) != 0)
+		goto out;
+
+	/* save session id := H */
+	if (kex->session_id == NULL) {
+		kex->session_id_len = hashlen;
+		kex->session_id = malloc(kex->session_id_len);
+		if (kex->session_id == NULL) {
+			r = SSH_ERR_ALLOC_FAIL;
+			goto out;
+		}
+		memcpy(kex->session_id, hash, kex->session_id_len);
+	}
+
+	/* sign H */
+	if ((r = kex->sign(server_host_private, server_host_public, &signature,
+	     &slen, hash, hashlen, kex->hostkey_alg, ssh->compat)) < 0)
+		goto out;
+
+	/* destroy_sensitive_data(); */
+
+	/* send server hostkey, DH pubkey 'f' and signed H */
+	if ((r = sshpkt_start(ssh, SSH2_MSG_KEX_DH_GEX_REPLY)) != 0 ||
+	    (r = sshpkt_put_string(ssh, server_host_key_blob, sbloblen)) != 0 ||
+	    (r = sshpkt_put_bignum2(ssh, pub_key)) != 0 ||     /* f */
+	    (r = sshpkt_put_string(ssh, signature, slen)) != 0 ||
+	    (r = sshpkt_send(ssh)) != 0)
+		goto out;
+
+	if ((r = kex_derive_keys_bn(ssh, hash, hashlen, shared_secret)) == 0)
+		r = kex_send_newkeys(ssh);
+ out:
+	explicit_bzero(hash, sizeof(hash));
+	DH_free(kex->dh);
+	kex->dh = NULL;
+	BN_clear_free(dh_client_pub);
+	if (kbuf) {
+		explicit_bzero(kbuf, klen);
+		free(kbuf);
+	}
+	BN_clear_free(shared_secret);
+	free(server_host_key_blob);
+	free(signature);
+	return r;
+}
+#endif /* WITH_OPENSSL */