Put ssh back into the repository
Change-Id: I23324372188fa6ed3f93a32b84365f5df6367590
diff --git a/kex.c b/kex.c
new file mode 100644
index 0000000..c65e28f
--- /dev/null
+++ b/kex.c
@@ -0,0 +1,610 @@
+/* $OpenBSD: kex.c,v 1.86 2010/09/22 05:01:29 djm Exp $ */
+/*
+ * Copyright (c) 2000, 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"
+
+#include <sys/param.h>
+
+#include <signal.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <openssl/crypto.h>
+
+#include "xmalloc.h"
+#include "ssh2.h"
+#include "buffer.h"
+#include "packet.h"
+#include "compat.h"
+#include "cipher.h"
+#include "key.h"
+#include "kex.h"
+#include "log.h"
+#include "mac.h"
+#include "match.h"
+#include "dispatch.h"
+#include "monitor.h"
+#include "roaming.h"
+
+#if OPENSSL_VERSION_NUMBER >= 0x00907000L
+# if defined(HAVE_EVP_SHA256)
+# define evp_ssh_sha256 EVP_sha256
+# else
+extern const EVP_MD *evp_ssh_sha256(void);
+# endif
+#endif
+
+/* prototype */
+static void kex_kexinit_finish(Kex *);
+static void kex_choose_conf(Kex *);
+
+/* Validate KEX method name list */
+int
+kex_names_valid(const char *names)
+{
+ char *s, *cp, *p;
+
+ if (names == NULL || strcmp(names, "") == 0)
+ return 0;
+ s = cp = xstrdup(names);
+ for ((p = strsep(&cp, ",")); p && *p != '\0';
+ (p = strsep(&cp, ","))) {
+ if (strcmp(p, KEX_DHGEX_SHA256) != 0 &&
+ strcmp(p, KEX_DHGEX_SHA1) != 0 &&
+ strcmp(p, KEX_DH14) != 0 &&
+ strcmp(p, KEX_DH1) != 0 &&
+ (strncmp(p, KEX_ECDH_SHA2_STEM,
+ sizeof(KEX_ECDH_SHA2_STEM) - 1) != 0 ||
+ kex_ecdh_name_to_nid(p) == -1)) {
+ error("Unsupported KEX algorithm \"%.100s\"", p);
+ xfree(s);
+ return 0;
+ }
+ }
+ debug3("kex names ok: [%s]", names);
+ xfree(s);
+ return 1;
+}
+
+/* put algorithm proposal into buffer */
+static void
+kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
+{
+ u_int i;
+
+ buffer_clear(b);
+ /*
+ * add a dummy cookie, the cookie will be overwritten by
+ * kex_send_kexinit(), each time a kexinit is set
+ */
+ for (i = 0; i < KEX_COOKIE_LEN; i++)
+ buffer_put_char(b, 0);
+ for (i = 0; i < PROPOSAL_MAX; i++)
+ buffer_put_cstring(b, proposal[i]);
+ buffer_put_char(b, 0); /* first_kex_packet_follows */
+ buffer_put_int(b, 0); /* uint32 reserved */
+}
+
+/* parse buffer and return algorithm proposal */
+static char **
+kex_buf2prop(Buffer *raw, int *first_kex_follows)
+{
+ Buffer b;
+ u_int i;
+ char **proposal;
+
+ proposal = xcalloc(PROPOSAL_MAX, sizeof(char *));
+
+ buffer_init(&b);
+ buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
+ /* skip cookie */
+ for (i = 0; i < KEX_COOKIE_LEN; i++)
+ buffer_get_char(&b);
+ /* extract kex init proposal strings */
+ for (i = 0; i < PROPOSAL_MAX; i++) {
+ proposal[i] = buffer_get_cstring(&b,NULL);
+ debug2("kex_parse_kexinit: %s", proposal[i]);
+ }
+ /* first kex follows / reserved */
+ i = buffer_get_char(&b);
+ if (first_kex_follows != NULL)
+ *first_kex_follows = i;
+ debug2("kex_parse_kexinit: first_kex_follows %d ", i);
+ i = buffer_get_int(&b);
+ debug2("kex_parse_kexinit: reserved %u ", i);
+ buffer_free(&b);
+ return proposal;
+}
+
+static void
+kex_prop_free(char **proposal)
+{
+ u_int i;
+
+ for (i = 0; i < PROPOSAL_MAX; i++)
+ xfree(proposal[i]);
+ xfree(proposal);
+}
+
+/* ARGSUSED */
+static void
+kex_protocol_error(int type, u_int32_t seq, void *ctxt)
+{
+ error("Hm, kex protocol error: type %d seq %u", type, seq);
+}
+
+static void
+kex_reset_dispatch(void)
+{
+ dispatch_range(SSH2_MSG_TRANSPORT_MIN,
+ SSH2_MSG_TRANSPORT_MAX, &kex_protocol_error);
+ dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
+}
+
+void
+kex_finish(Kex *kex)
+{
+ kex_reset_dispatch();
+
+ packet_start(SSH2_MSG_NEWKEYS);
+ packet_send();
+ /* packet_write_wait(); */
+ debug("SSH2_MSG_NEWKEYS sent");
+
+ debug("expecting SSH2_MSG_NEWKEYS");
+ packet_read_expect(SSH2_MSG_NEWKEYS);
+ packet_check_eom();
+ debug("SSH2_MSG_NEWKEYS received");
+
+ kex->done = 1;
+ buffer_clear(&kex->peer);
+ /* buffer_clear(&kex->my); */
+ kex->flags &= ~KEX_INIT_SENT;
+ xfree(kex->name);
+ kex->name = NULL;
+}
+
+void
+kex_send_kexinit(Kex *kex)
+{
+ u_int32_t rnd = 0;
+ u_char *cookie;
+ u_int i;
+
+ if (kex == NULL) {
+ error("kex_send_kexinit: no kex, cannot rekey");
+ return;
+ }
+ if (kex->flags & KEX_INIT_SENT) {
+ debug("KEX_INIT_SENT");
+ return;
+ }
+ kex->done = 0;
+
+ /* generate a random cookie */
+ if (buffer_len(&kex->my) < KEX_COOKIE_LEN)
+ fatal("kex_send_kexinit: kex proposal too short");
+ cookie = buffer_ptr(&kex->my);
+ for (i = 0; i < KEX_COOKIE_LEN; i++) {
+ if (i % 4 == 0)
+ rnd = arc4random();
+ cookie[i] = rnd;
+ rnd >>= 8;
+ }
+ packet_start(SSH2_MSG_KEXINIT);
+ packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
+ packet_send();
+ debug("SSH2_MSG_KEXINIT sent");
+ kex->flags |= KEX_INIT_SENT;
+}
+
+/* ARGSUSED */
+void
+kex_input_kexinit(int type, u_int32_t seq, void *ctxt)
+{
+ char *ptr;
+ u_int i, dlen;
+ Kex *kex = (Kex *)ctxt;
+
+ debug("SSH2_MSG_KEXINIT received");
+ if (kex == NULL)
+ fatal("kex_input_kexinit: no kex, cannot rekey");
+
+ ptr = packet_get_raw(&dlen);
+ buffer_append(&kex->peer, ptr, dlen);
+
+ /* discard packet */
+ for (i = 0; i < KEX_COOKIE_LEN; i++)
+ packet_get_char();
+ for (i = 0; i < PROPOSAL_MAX; i++)
+ xfree(packet_get_string(NULL));
+ (void) packet_get_char();
+ (void) packet_get_int();
+ packet_check_eom();
+
+ kex_kexinit_finish(kex);
+}
+
+Kex *
+kex_setup(char *proposal[PROPOSAL_MAX])
+{
+ Kex *kex;
+
+ kex = xcalloc(1, sizeof(*kex));
+ buffer_init(&kex->peer);
+ buffer_init(&kex->my);
+ kex_prop2buf(&kex->my, proposal);
+ kex->done = 0;
+
+ kex_send_kexinit(kex); /* we start */
+ kex_reset_dispatch();
+
+ return kex;
+}
+
+static void
+kex_kexinit_finish(Kex *kex)
+{
+ if (!(kex->flags & KEX_INIT_SENT))
+ kex_send_kexinit(kex);
+
+ kex_choose_conf(kex);
+
+ if (kex->kex_type >= 0 && kex->kex_type < KEX_MAX &&
+ kex->kex[kex->kex_type] != NULL) {
+ (kex->kex[kex->kex_type])(kex);
+ } else {
+ fatal("Unsupported key exchange %d", kex->kex_type);
+ }
+}
+
+static void
+choose_enc(Enc *enc, char *client, char *server)
+{
+ char *name = match_list(client, server, NULL);
+ if (name == NULL)
+ fatal("no matching cipher found: client %s server %s",
+ client, server);
+ if ((enc->cipher = cipher_by_name(name)) == NULL)
+ fatal("matching cipher is not supported: %s", name);
+ enc->name = name;
+ enc->enabled = 0;
+ enc->iv = NULL;
+ enc->key = NULL;
+ enc->key_len = cipher_keylen(enc->cipher);
+ enc->block_size = cipher_blocksize(enc->cipher);
+}
+
+static void
+choose_mac(Mac *mac, char *client, char *server)
+{
+ char *name = match_list(client, server, NULL);
+ if (name == NULL)
+ fatal("no matching mac found: client %s server %s",
+ client, server);
+ if (mac_setup(mac, name) < 0)
+ fatal("unsupported mac %s", name);
+ /* truncate the key */
+ if (datafellows & SSH_BUG_HMAC)
+ mac->key_len = 16;
+ mac->name = name;
+ mac->key = NULL;
+ mac->enabled = 0;
+}
+
+static void
+choose_comp(Comp *comp, char *client, char *server)
+{
+ char *name = match_list(client, server, NULL);
+ if (name == NULL)
+ fatal("no matching comp found: client %s server %s", client, server);
+ if (strcmp(name, "zlib@openssh.com") == 0) {
+ comp->type = COMP_DELAYED;
+ } else if (strcmp(name, "zlib") == 0) {
+ comp->type = COMP_ZLIB;
+ } else if (strcmp(name, "none") == 0) {
+ comp->type = COMP_NONE;
+ } else {
+ fatal("unsupported comp %s", name);
+ }
+ comp->name = name;
+}
+
+static void
+choose_kex(Kex *k, char *client, char *server)
+{
+ k->name = match_list(client, server, NULL);
+ if (k->name == NULL)
+ fatal("Unable to negotiate a key exchange method");
+ if (strcmp(k->name, KEX_DH1) == 0) {
+ k->kex_type = KEX_DH_GRP1_SHA1;
+ k->evp_md = EVP_sha1();
+ } else if (strcmp(k->name, KEX_DH14) == 0) {
+ k->kex_type = KEX_DH_GRP14_SHA1;
+ k->evp_md = EVP_sha1();
+ } else if (strcmp(k->name, KEX_DHGEX_SHA1) == 0) {
+ k->kex_type = KEX_DH_GEX_SHA1;
+ k->evp_md = EVP_sha1();
+#if OPENSSL_VERSION_NUMBER >= 0x00907000L
+ } else if (strcmp(k->name, KEX_DHGEX_SHA256) == 0) {
+ k->kex_type = KEX_DH_GEX_SHA256;
+ k->evp_md = evp_ssh_sha256();
+ } else if (strncmp(k->name, KEX_ECDH_SHA2_STEM,
+ sizeof(KEX_ECDH_SHA2_STEM) - 1) == 0) {
+ k->kex_type = KEX_ECDH_SHA2;
+ k->evp_md = kex_ecdh_name_to_evpmd(k->name);
+#endif
+ } else
+ fatal("bad kex alg %s", k->name);
+}
+
+static void
+choose_hostkeyalg(Kex *k, char *client, char *server)
+{
+ char *hostkeyalg = match_list(client, server, NULL);
+ if (hostkeyalg == NULL)
+ fatal("no hostkey alg");
+ k->hostkey_type = key_type_from_name(hostkeyalg);
+ if (k->hostkey_type == KEY_UNSPEC)
+ fatal("bad hostkey alg '%s'", hostkeyalg);
+ xfree(hostkeyalg);
+}
+
+static int
+proposals_match(char *my[PROPOSAL_MAX], char *peer[PROPOSAL_MAX])
+{
+ static int check[] = {
+ PROPOSAL_KEX_ALGS, PROPOSAL_SERVER_HOST_KEY_ALGS, -1
+ };
+ int *idx;
+ char *p;
+
+ for (idx = &check[0]; *idx != -1; idx++) {
+ if ((p = strchr(my[*idx], ',')) != NULL)
+ *p = '\0';
+ if ((p = strchr(peer[*idx], ',')) != NULL)
+ *p = '\0';
+ if (strcmp(my[*idx], peer[*idx]) != 0) {
+ debug2("proposal mismatch: my %s peer %s",
+ my[*idx], peer[*idx]);
+ return (0);
+ }
+ }
+ debug2("proposals match");
+ return (1);
+}
+
+static void
+kex_choose_conf(Kex *kex)
+{
+ Newkeys *newkeys;
+ char **my, **peer;
+ char **cprop, **sprop;
+ int nenc, nmac, ncomp;
+ u_int mode, ctos, need;
+ int first_kex_follows, type;
+
+ my = kex_buf2prop(&kex->my, NULL);
+ peer = kex_buf2prop(&kex->peer, &first_kex_follows);
+
+ if (kex->server) {
+ cprop=peer;
+ sprop=my;
+ } else {
+ cprop=my;
+ sprop=peer;
+ }
+
+ /* Check whether server offers roaming */
+ if (!kex->server) {
+ char *roaming;
+ roaming = match_list(KEX_RESUME, peer[PROPOSAL_KEX_ALGS], NULL);
+ if (roaming) {
+ kex->roaming = 1;
+ xfree(roaming);
+ }
+ }
+
+ /* Algorithm Negotiation */
+ for (mode = 0; mode < MODE_MAX; mode++) {
+ newkeys = xcalloc(1, sizeof(*newkeys));
+ kex->newkeys[mode] = newkeys;
+ ctos = (!kex->server && mode == MODE_OUT) ||
+ (kex->server && mode == MODE_IN);
+ nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
+ nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
+ ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
+ choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
+ choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
+ choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
+ debug("kex: %s %s %s %s",
+ ctos ? "client->server" : "server->client",
+ newkeys->enc.name,
+ newkeys->mac.name,
+ newkeys->comp.name);
+ }
+ choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
+ choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
+ sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
+ need = 0;
+ for (mode = 0; mode < MODE_MAX; mode++) {
+ newkeys = kex->newkeys[mode];
+ if (need < newkeys->enc.key_len)
+ need = newkeys->enc.key_len;
+ if (need < newkeys->enc.block_size)
+ need = newkeys->enc.block_size;
+ if (need < newkeys->mac.key_len)
+ need = newkeys->mac.key_len;
+ }
+ /* XXX need runden? */
+ kex->we_need = need;
+
+ /* ignore the next message if the proposals do not match */
+ if (first_kex_follows && !proposals_match(my, peer) &&
+ !(datafellows & SSH_BUG_FIRSTKEX)) {
+ type = packet_read();
+ debug2("skipping next packet (type %u)", type);
+ }
+
+ kex_prop_free(my);
+ kex_prop_free(peer);
+}
+
+static u_char *
+derive_key(Kex *kex, int id, u_int need, u_char *hash, u_int hashlen,
+ BIGNUM *shared_secret)
+{
+ Buffer b;
+ EVP_MD_CTX md;
+ char c = id;
+ u_int have;
+ int mdsz;
+ u_char *digest;
+
+ if ((mdsz = EVP_MD_size(kex->evp_md)) <= 0)
+ fatal("bad kex md size %d", mdsz);
+ digest = xmalloc(roundup(need, mdsz));
+
+ buffer_init(&b);
+ buffer_put_bignum2(&b, shared_secret);
+
+ /* K1 = HASH(K || H || "A" || session_id) */
+ EVP_DigestInit(&md, kex->evp_md);
+ if (!(datafellows & SSH_BUG_DERIVEKEY))
+ EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
+ EVP_DigestUpdate(&md, hash, hashlen);
+ EVP_DigestUpdate(&md, &c, 1);
+ EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
+ EVP_DigestFinal(&md, digest, NULL);
+
+ /*
+ * expand key:
+ * Kn = HASH(K || H || K1 || K2 || ... || Kn-1)
+ * Key = K1 || K2 || ... || Kn
+ */
+ for (have = mdsz; need > have; have += mdsz) {
+ EVP_DigestInit(&md, kex->evp_md);
+ if (!(datafellows & SSH_BUG_DERIVEKEY))
+ EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
+ EVP_DigestUpdate(&md, hash, hashlen);
+ EVP_DigestUpdate(&md, digest, have);
+ EVP_DigestFinal(&md, digest + have, NULL);
+ }
+ buffer_free(&b);
+#ifdef DEBUG_KEX
+ fprintf(stderr, "key '%c'== ", c);
+ dump_digest("key", digest, need);
+#endif
+ return digest;
+}
+
+Newkeys *current_keys[MODE_MAX];
+
+#define NKEYS 6
+void
+kex_derive_keys(Kex *kex, u_char *hash, u_int hashlen, BIGNUM *shared_secret)
+{
+ u_char *keys[NKEYS];
+ u_int i, mode, ctos;
+
+ for (i = 0; i < NKEYS; i++) {
+ keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, hashlen,
+ shared_secret);
+ }
+
+ debug2("kex_derive_keys");
+ for (mode = 0; mode < MODE_MAX; mode++) {
+ current_keys[mode] = kex->newkeys[mode];
+ kex->newkeys[mode] = NULL;
+ ctos = (!kex->server && mode == MODE_OUT) ||
+ (kex->server && mode == MODE_IN);
+ current_keys[mode]->enc.iv = keys[ctos ? 0 : 1];
+ current_keys[mode]->enc.key = keys[ctos ? 2 : 3];
+ current_keys[mode]->mac.key = keys[ctos ? 4 : 5];
+ }
+}
+
+Newkeys *
+kex_get_newkeys(int mode)
+{
+ Newkeys *ret;
+
+ ret = current_keys[mode];
+ current_keys[mode] = NULL;
+ return ret;
+}
+
+void
+derive_ssh1_session_id(BIGNUM *host_modulus, BIGNUM *server_modulus,
+ u_int8_t cookie[8], u_int8_t id[16])
+{
+ const EVP_MD *evp_md = EVP_md5();
+ EVP_MD_CTX md;
+ u_int8_t nbuf[2048], obuf[EVP_MAX_MD_SIZE];
+ int len;
+
+ EVP_DigestInit(&md, evp_md);
+
+ len = BN_num_bytes(host_modulus);
+ if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
+ fatal("%s: bad host modulus (len %d)", __func__, len);
+ BN_bn2bin(host_modulus, nbuf);
+ EVP_DigestUpdate(&md, nbuf, len);
+
+ len = BN_num_bytes(server_modulus);
+ if (len < (512 / 8) || (u_int)len > sizeof(nbuf))
+ fatal("%s: bad server modulus (len %d)", __func__, len);
+ BN_bn2bin(server_modulus, nbuf);
+ EVP_DigestUpdate(&md, nbuf, len);
+
+ EVP_DigestUpdate(&md, cookie, 8);
+
+ EVP_DigestFinal(&md, obuf, NULL);
+ memcpy(id, obuf, 16);
+
+ memset(nbuf, 0, sizeof(nbuf));
+ memset(obuf, 0, sizeof(obuf));
+ memset(&md, 0, sizeof(md));
+}
+
+#if defined(DEBUG_KEX) || defined(DEBUG_KEXDH) || defined(DEBUG_KEXECDH)
+void
+dump_digest(char *msg, u_char *digest, int len)
+{
+ int i;
+
+ fprintf(stderr, "%s\n", msg);
+ for (i = 0; i < len; i++) {
+ fprintf(stderr, "%02x", digest[i]);
+ if (i%32 == 31)
+ fprintf(stderr, "\n");
+ else if (i%8 == 7)
+ fprintf(stderr, " ");
+ }
+ fprintf(stderr, "\n");
+}
+#endif