Annotation of src/usr.bin/ssh/kex.c, Revision 1.27
1.1 markus 1: /*
2: * Copyright (c) 2000 Markus Friedl. All rights reserved.
3: *
4: * Redistribution and use in source and binary forms, with or without
5: * modification, are permitted provided that the following conditions
6: * are met:
7: * 1. Redistributions of source code must retain the above copyright
8: * notice, this list of conditions and the following disclaimer.
9: * 2. Redistributions in binary form must reproduce the above copyright
10: * notice, this list of conditions and the following disclaimer in the
11: * documentation and/or other materials provided with the distribution.
12: *
13: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23: */
24:
25: #include "includes.h"
1.27 ! markus 26: RCSID("$OpenBSD: kex.c,v 1.26 2001/04/03 19:53:29 markus Exp $");
1.18 markus 27:
28: #include <openssl/crypto.h>
1.1 markus 29:
30: #include "ssh2.h"
31: #include "xmalloc.h"
32: #include "buffer.h"
33: #include "bufaux.h"
1.7 markus 34: #include "packet.h"
1.1 markus 35: #include "compat.h"
1.18 markus 36: #include "cipher.h"
1.1 markus 37: #include "kex.h"
1.13 markus 38: #include "key.h"
1.18 markus 39: #include "log.h"
1.21 markus 40: #include "mac.h"
1.23 markus 41: #include "match.h"
1.26 markus 42: #include "dispatch.h"
1.1 markus 43:
1.7 markus 44: #define KEX_COOKIE_LEN 16
45:
1.26 markus 46: void kex_kexinit_finish(Kex *kex);
47: void kex_choose_conf(Kex *k);
48:
49: /* put algorithm proposal into buffer */
50: void
51: kex_prop2buf(Buffer *b, char *proposal[PROPOSAL_MAX])
1.1 markus 52: {
53: u_int32_t rand = 0;
54: int i;
1.26 markus 55:
56: buffer_clear(b);
1.7 markus 57: for (i = 0; i < KEX_COOKIE_LEN; i++) {
1.1 markus 58: if (i % 4 == 0)
59: rand = arc4random();
1.26 markus 60: buffer_put_char(b, rand & 0xff);
1.1 markus 61: rand >>= 8;
62: }
63: for (i = 0; i < PROPOSAL_MAX; i++)
1.26 markus 64: buffer_put_cstring(b, proposal[i]);
65: buffer_put_char(b, 0); /* first_kex_packet_follows */
66: buffer_put_int(b, 0); /* uint32 reserved */
1.1 markus 67: }
68:
1.26 markus 69: /* parse buffer and return algorithm proposal */
70: char **
71: kex_buf2prop(Buffer *raw)
1.7 markus 72: {
1.26 markus 73: Buffer b;
1.7 markus 74: int i;
1.26 markus 75: char **proposal;
1.7 markus 76:
1.26 markus 77: proposal = xmalloc(PROPOSAL_MAX * sizeof(char *));
1.7 markus 78:
1.26 markus 79: buffer_init(&b);
80: buffer_append(&b, buffer_ptr(raw), buffer_len(raw));
1.7 markus 81: /* skip cookie */
82: for (i = 0; i < KEX_COOKIE_LEN; i++)
1.26 markus 83: buffer_get_char(&b);
1.7 markus 84: /* extract kex init proposal strings */
85: for (i = 0; i < PROPOSAL_MAX; i++) {
1.26 markus 86: proposal[i] = buffer_get_string(&b,NULL);
87: debug2("kex_parse_kexinit: %s", proposal[i]);
1.7 markus 88: }
1.26 markus 89: /* first kex follows / reserved */
90: i = buffer_get_char(&b);
91: debug2("kex_parse_kexinit: first_kex_follows %d ", i);
92: i = buffer_get_int(&b);
93: debug2("kex_parse_kexinit: reserved %d ", i);
94: buffer_free(&b);
95: return proposal;
1.1 markus 96: }
97:
98: void
1.26 markus 99: kex_prop_free(char **proposal)
1.1 markus 100: {
101: int i;
1.26 markus 102:
103: for (i = 0; i < PROPOSAL_MAX; i++)
104: xfree(proposal[i]);
105: xfree(proposal);
1.1 markus 106: }
107:
1.26 markus 108: void
109: kex_protocol_error(int type, int plen, void *ctxt)
1.1 markus 110: {
1.26 markus 111: error("Hm, kex protocol error: type %d plen %d", type, plen);
112: }
1.1 markus 113:
1.26 markus 114: void
115: kex_send_newkeys(void)
116: {
117: packet_start(SSH2_MSG_NEWKEYS);
118: packet_send();
119: /* packet_write_wait(); */
120: debug("SSH2_MSG_NEWKEYS sent");
121: }
1.1 markus 122:
1.26 markus 123: void
124: kex_input_newkeys(int type, int plen, void *ctxt)
125: {
126: Kex *kex = ctxt;
127: int i;
1.19 stevesk 128:
1.26 markus 129: debug("SSH2_MSG_NEWKEYS received");
130: kex->newkeys = 1;
131: for (i = 30; i <= 49; i++)
132: dispatch_set(i, &kex_protocol_error);
133: buffer_clear(&kex->peer);
1.27 ! markus 134: /* buffer_clear(&kex->my); */
1.26 markus 135: kex->flags &= ~KEX_INIT_SENT;
136: }
1.1 markus 137:
1.26 markus 138: void
139: kex_send_kexinit(Kex *kex)
140: {
141: packet_start(SSH2_MSG_KEXINIT);
142: packet_put_raw(buffer_ptr(&kex->my), buffer_len(&kex->my));
143: packet_send();
144: debug("SSH2_MSG_KEXINIT sent");
145: kex->flags |= KEX_INIT_SENT;
1.1 markus 146: }
147:
1.26 markus 148: void
149: kex_input_kexinit(int type, int plen, void *ctxt)
1.11 provos 150: {
1.26 markus 151: char *ptr;
152: int dlen;
153: Kex *kex = (Kex *)ctxt;
1.11 provos 154:
1.26 markus 155: debug("SSH2_MSG_KEXINIT received");
1.11 provos 156:
1.26 markus 157: ptr = packet_get_raw(&dlen);
158: buffer_append(&kex->peer, ptr, dlen);
1.19 stevesk 159:
1.26 markus 160: kex_kexinit_finish(kex);
161: }
1.11 provos 162:
1.26 markus 163: Kex *
164: kex_start(char *proposal[PROPOSAL_MAX])
165: {
166: Kex *kex;
167: int i;
1.11 provos 168:
1.26 markus 169: kex = xmalloc(sizeof(*kex));
170: memset(kex, 0, sizeof(*kex));
171: buffer_init(&kex->peer);
172: buffer_init(&kex->my);
173: kex_prop2buf(&kex->my, proposal);
174: kex->newkeys = 0;
175:
176: kex_send_kexinit(kex); /* we start */
177: /* Numbers 30-49 are used for kex packets */
178: for (i = 30; i <= 49; i++)
179: dispatch_set(i, kex_protocol_error);
180:
181: dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
182: dispatch_set(SSH2_MSG_NEWKEYS, &kex_input_newkeys);
183: return kex;
1.11 provos 184: }
185:
1.26 markus 186: void
187: kex_kexinit_finish(Kex *kex)
1.1 markus 188: {
1.26 markus 189: if (!(kex->flags & KEX_INIT_SENT))
190: kex_send_kexinit(kex);
1.1 markus 191:
1.26 markus 192: kex_choose_conf(kex);
1.1 markus 193:
1.26 markus 194: switch(kex->kex_type) {
195: case DH_GRP1_SHA1:
196: kexdh(kex);
197: break;
198: case DH_GEX_SHA1:
199: kexgex(kex);
200: break;
201: default:
202: fatal("Unsupported key exchange %d", kex->kex_type);
1.1 markus 203: }
204: }
205:
206: void
207: choose_enc(Enc *enc, char *client, char *server)
208: {
1.23 markus 209: char *name = match_list(client, server, NULL);
1.1 markus 210: if (name == NULL)
211: fatal("no matching cipher found: client %s server %s", client, server);
1.12 markus 212: enc->cipher = cipher_by_name(name);
213: if (enc->cipher == NULL)
214: fatal("matching cipher is not supported: %s", name);
1.1 markus 215: enc->name = name;
216: enc->enabled = 0;
217: enc->iv = NULL;
218: enc->key = NULL;
219: }
220: void
221: choose_mac(Mac *mac, char *client, char *server)
222: {
1.23 markus 223: char *name = match_list(client, server, NULL);
1.1 markus 224: if (name == NULL)
225: fatal("no matching mac found: client %s server %s", client, server);
1.21 markus 226: if (mac_init(mac, name) < 0)
1.1 markus 227: fatal("unsupported mac %s", name);
1.21 markus 228: /* truncate the key */
229: if (datafellows & SSH_BUG_HMAC)
230: mac->key_len = 16;
1.1 markus 231: mac->name = name;
232: mac->key = NULL;
233: mac->enabled = 0;
234: }
235: void
236: choose_comp(Comp *comp, char *client, char *server)
237: {
1.23 markus 238: char *name = match_list(client, server, NULL);
1.1 markus 239: if (name == NULL)
240: fatal("no matching comp found: client %s server %s", client, server);
241: if (strcmp(name, "zlib") == 0) {
242: comp->type = 1;
243: } else if (strcmp(name, "none") == 0) {
244: comp->type = 0;
245: } else {
246: fatal("unsupported comp %s", name);
247: }
248: comp->name = name;
249: }
250: void
251: choose_kex(Kex *k, char *client, char *server)
252: {
1.23 markus 253: k->name = match_list(client, server, NULL);
1.1 markus 254: if (k->name == NULL)
255: fatal("no kex alg");
1.11 provos 256: if (strcmp(k->name, KEX_DH1) == 0) {
257: k->kex_type = DH_GRP1_SHA1;
258: } else if (strcmp(k->name, KEX_DHGEX) == 0) {
259: k->kex_type = DH_GEX_SHA1;
260: } else
1.1 markus 261: fatal("bad kex alg %s", k->name);
262: }
263: void
264: choose_hostkeyalg(Kex *k, char *client, char *server)
265: {
1.23 markus 266: char *hostkeyalg = match_list(client, server, NULL);
1.13 markus 267: if (hostkeyalg == NULL)
1.1 markus 268: fatal("no hostkey alg");
1.13 markus 269: k->hostkey_type = key_type_from_name(hostkeyalg);
270: if (k->hostkey_type == KEY_UNSPEC)
271: fatal("bad hostkey alg '%s'", hostkeyalg);
1.17 markus 272: xfree(hostkeyalg);
1.1 markus 273: }
274:
1.26 markus 275: void
1.27 ! markus 276: kex_choose_conf(Kex *kex)
1.1 markus 277: {
1.27 ! markus 278: Newkeys *newkeys;
1.26 markus 279: char **my, **peer;
280: char **cprop, **sprop;
1.27 ! markus 281: int nenc, nmac, ncomp;
1.1 markus 282: int mode;
283: int ctos; /* direction: if true client-to-server */
284: int need;
285:
1.27 ! markus 286: my = kex_buf2prop(&kex->my);
! 287: peer = kex_buf2prop(&kex->peer);
1.26 markus 288:
1.27 ! markus 289: if (kex->server) {
1.26 markus 290: cprop=peer;
291: sprop=my;
292: } else {
293: cprop=my;
294: sprop=peer;
295: }
1.1 markus 296:
297: for (mode = 0; mode < MODE_MAX; mode++) {
1.27 ! markus 298: newkeys = xmalloc(sizeof(*newkeys));
! 299: memset(newkeys, 0, sizeof(*newkeys));
! 300: kex->keys[mode] = newkeys;
! 301: ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
1.1 markus 302: nenc = ctos ? PROPOSAL_ENC_ALGS_CTOS : PROPOSAL_ENC_ALGS_STOC;
303: nmac = ctos ? PROPOSAL_MAC_ALGS_CTOS : PROPOSAL_MAC_ALGS_STOC;
304: ncomp = ctos ? PROPOSAL_COMP_ALGS_CTOS : PROPOSAL_COMP_ALGS_STOC;
1.27 ! markus 305: choose_enc (&newkeys->enc, cprop[nenc], sprop[nenc]);
! 306: choose_mac (&newkeys->mac, cprop[nmac], sprop[nmac]);
! 307: choose_comp(&newkeys->comp, cprop[ncomp], sprop[ncomp]);
1.2 markus 308: debug("kex: %s %s %s %s",
1.1 markus 309: ctos ? "client->server" : "server->client",
1.27 ! markus 310: newkeys->enc.name,
! 311: newkeys->mac.name,
! 312: newkeys->comp.name);
1.1 markus 313: }
1.27 ! markus 314: choose_kex(kex, cprop[PROPOSAL_KEX_ALGS], sprop[PROPOSAL_KEX_ALGS]);
! 315: choose_hostkeyalg(kex, cprop[PROPOSAL_SERVER_HOST_KEY_ALGS],
1.1 markus 316: sprop[PROPOSAL_SERVER_HOST_KEY_ALGS]);
317: need = 0;
318: for (mode = 0; mode < MODE_MAX; mode++) {
1.27 ! markus 319: newkeys = kex->keys[mode];
! 320: if (need < newkeys->enc.cipher->key_len)
! 321: need = newkeys->enc.cipher->key_len;
! 322: if (need < newkeys->enc.cipher->block_size)
! 323: need = newkeys->enc.cipher->block_size;
! 324: if (need < newkeys->mac.key_len)
! 325: need = newkeys->mac.key_len;
1.1 markus 326: }
1.7 markus 327: /* XXX need runden? */
1.27 ! markus 328: kex->we_need = need;
1.26 markus 329:
330: kex_prop_free(my);
331: kex_prop_free(peer);
332: }
333:
334: u_char *
1.27 ! markus 335: derive_key(Kex *kex, int id, int need, u_char *hash, BIGNUM *shared_secret)
1.26 markus 336: {
337: Buffer b;
338: EVP_MD *evp_md = EVP_sha1();
339: EVP_MD_CTX md;
340: char c = id;
341: int have;
342: int mdsz = evp_md->md_size;
343: u_char *digest = xmalloc(((need+mdsz-1)/mdsz)*mdsz);
344:
345: buffer_init(&b);
346: buffer_put_bignum2(&b, shared_secret);
347:
348: EVP_DigestInit(&md, evp_md);
349: EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b)); /* shared_secret K */
350: EVP_DigestUpdate(&md, hash, mdsz); /* transport-06 */
351: EVP_DigestUpdate(&md, &c, 1); /* key id */
1.27 ! markus 352: EVP_DigestUpdate(&md, kex->session_id, kex->session_id_len);
1.26 markus 353: EVP_DigestFinal(&md, digest, NULL);
354:
355: /* expand */
356: for (have = mdsz; need > have; have += mdsz) {
357: EVP_DigestInit(&md, evp_md);
358: EVP_DigestUpdate(&md, buffer_ptr(&b), buffer_len(&b));
359: EVP_DigestUpdate(&md, hash, mdsz);
360: EVP_DigestUpdate(&md, digest, have);
361: EVP_DigestFinal(&md, digest + have, NULL);
362: }
363: buffer_free(&b);
364: #ifdef DEBUG_KEX
365: fprintf(stderr, "key '%c'== ", c);
366: dump_digest("key", digest, need);
367: #endif
368: return digest;
1.1 markus 369: }
370:
1.27 ! markus 371: Newkeys *x_newkeys[MODE_MAX];
! 372:
1.23 markus 373: #define NKEYS 6
1.26 markus 374: void
1.27 ! markus 375: kex_derive_keys(Kex *kex, u_char *hash, BIGNUM *shared_secret)
1.1 markus 376: {
1.27 ! markus 377: Newkeys *newkeys;
1.15 markus 378: u_char *keys[NKEYS];
1.27 ! markus 379: int i, mode, ctos;
1.1 markus 380:
381: for (i = 0; i < NKEYS; i++)
1.27 ! markus 382: keys[i] = derive_key(kex, 'A'+i, kex->we_need, hash, shared_secret);
1.1 markus 383:
1.27 ! markus 384: debug("kex_derive_keys");
1.1 markus 385: for (mode = 0; mode < MODE_MAX; mode++) {
1.27 ! markus 386: newkeys = kex->keys[mode];
! 387: ctos = (!kex->server && mode == MODE_OUT) || (kex->server && mode == MODE_IN);
! 388: newkeys->enc.iv = keys[ctos ? 0 : 1];
! 389: newkeys->enc.key = keys[ctos ? 2 : 3];
! 390: newkeys->mac.key = keys[ctos ? 4 : 5];
! 391: x_newkeys[mode] = newkeys;
1.1 markus 392: }
1.27 ! markus 393: }
! 394:
! 395: Newkeys *
! 396: kex_get_newkeys(int mode)
! 397: {
! 398: return x_newkeys[mode];
1.1 markus 399: }
1.26 markus 400:
401: #if defined(DEBUG_KEX) || defined(DEBUG_KEXDH)
402: void
403: dump_digest(char *msg, u_char *digest, int len)
404: {
405: int i;
406:
407: fprintf(stderr, "%s\n", msg);
408: for (i = 0; i< len; i++){
409: fprintf(stderr, "%02x", digest[i]);
410: if (i%32 == 31)
411: fprintf(stderr, "\n");
412: else if (i%8 == 7)
413: fprintf(stderr, " ");
414: }
415: fprintf(stderr, "\n");
416: }
417: #endif
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