Annotation of src/usr.bin/ssh/cipher.c, Revision 1.89
1.89 ! djm 1: /* $OpenBSD: cipher.c,v 1.88 2013/04/19 01:06:50 djm Exp $ */
1.1 deraadt 2: /*
1.30 deraadt 3: * Author: Tatu Ylonen <ylo@cs.hut.fi>
4: * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5: * All rights reserved
1.26 markus 6: *
1.30 deraadt 7: * As far as I am concerned, the code I have written for this software
8: * can be used freely for any purpose. Any derived versions of this
9: * software must be clearly marked as such, and if the derived work is
10: * incompatible with the protocol description in the RFC file, it must be
11: * called by a name other than "ssh" or "Secure Shell".
1.26 markus 12: *
13: *
1.30 deraadt 14: * Copyright (c) 1999 Niels Provos. All rights reserved.
1.46 markus 15: * Copyright (c) 1999, 2000 Markus Friedl. All rights reserved.
1.26 markus 16: *
1.30 deraadt 17: * Redistribution and use in source and binary forms, with or without
18: * modification, are permitted provided that the following conditions
19: * are met:
20: * 1. Redistributions of source code must retain the above copyright
21: * notice, this list of conditions and the following disclaimer.
22: * 2. Redistributions in binary form must reproduce the above copyright
23: * notice, this list of conditions and the following disclaimer in the
24: * documentation and/or other materials provided with the distribution.
1.26 markus 25: *
1.30 deraadt 26: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
27: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
28: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
29: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
30: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
31: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
35: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.17 deraadt 36: */
1.1 deraadt 37:
1.81 deraadt 38: #include <sys/types.h>
1.1 deraadt 39:
1.80 stevesk 40: #include <openssl/md5.h>
41:
42: #include <string.h>
1.81 deraadt 43: #include <stdarg.h>
1.80 stevesk 44:
1.24 markus 45: #include "xmalloc.h"
1.42 markus 46: #include "log.h"
47: #include "cipher.h"
1.57 markus 48:
1.64 markus 49: extern const EVP_CIPHER *evp_ssh1_bf(void);
50: extern const EVP_CIPHER *evp_ssh1_3des(void);
51: extern void ssh1_3des_iv(EVP_CIPHER_CTX *, int, u_char *, int);
1.1 deraadt 52:
1.51 markus 53: struct Cipher {
54: char *name;
55: int number; /* for ssh1 only */
56: u_int block_size;
57: u_int key_len;
1.85 markus 58: u_int iv_len; /* defaults to block_size */
59: u_int auth_len;
1.74 djm 60: u_int discard_len;
1.82 markus 61: u_int cbc_mode;
1.56 markus 62: const EVP_CIPHER *(*evptype)(void);
1.88 djm 63: };
64:
65: static const struct Cipher ciphers[] = {
1.85 markus 66: { "none", SSH_CIPHER_NONE, 8, 0, 0, 0, 0, 0, EVP_enc_null },
67: { "des", SSH_CIPHER_DES, 8, 8, 0, 0, 0, 1, EVP_des_cbc },
68: { "3des", SSH_CIPHER_3DES, 8, 16, 0, 0, 0, 1, evp_ssh1_3des },
69: { "blowfish", SSH_CIPHER_BLOWFISH, 8, 32, 0, 0, 0, 1, evp_ssh1_bf },
70:
71: { "3des-cbc", SSH_CIPHER_SSH2, 8, 24, 0, 0, 0, 1, EVP_des_ede3_cbc },
72: { "blowfish-cbc",
73: SSH_CIPHER_SSH2, 8, 16, 0, 0, 0, 1, EVP_bf_cbc },
74: { "cast128-cbc",
75: SSH_CIPHER_SSH2, 8, 16, 0, 0, 0, 1, EVP_cast5_cbc },
76: { "arcfour", SSH_CIPHER_SSH2, 8, 16, 0, 0, 0, 0, EVP_rc4 },
77: { "arcfour128", SSH_CIPHER_SSH2, 8, 16, 0, 0, 1536, 0, EVP_rc4 },
78: { "arcfour256", SSH_CIPHER_SSH2, 8, 32, 0, 0, 1536, 0, EVP_rc4 },
79: { "aes128-cbc", SSH_CIPHER_SSH2, 16, 16, 0, 0, 0, 1, EVP_aes_128_cbc },
80: { "aes192-cbc", SSH_CIPHER_SSH2, 16, 24, 0, 0, 0, 1, EVP_aes_192_cbc },
81: { "aes256-cbc", SSH_CIPHER_SSH2, 16, 32, 0, 0, 0, 1, EVP_aes_256_cbc },
1.57 markus 82: { "rijndael-cbc@lysator.liu.se",
1.85 markus 83: SSH_CIPHER_SSH2, 16, 32, 0, 0, 0, 1, EVP_aes_256_cbc },
84: { "aes128-ctr", SSH_CIPHER_SSH2, 16, 16, 0, 0, 0, 0, EVP_aes_128_ctr },
85: { "aes192-ctr", SSH_CIPHER_SSH2, 16, 24, 0, 0, 0, 0, EVP_aes_192_ctr },
86: { "aes256-ctr", SSH_CIPHER_SSH2, 16, 32, 0, 0, 0, 0, EVP_aes_256_ctr },
87: { "aes128-gcm@openssh.com",
88: SSH_CIPHER_SSH2, 16, 16, 12, 16, 0, 0, EVP_aes_128_gcm },
89: { "aes256-gcm@openssh.com",
90: SSH_CIPHER_SSH2, 16, 32, 12, 16, 0, 0, EVP_aes_256_gcm },
1.47 markus 91:
1.85 markus 92: { NULL, SSH_CIPHER_INVALID, 0, 0, 0, 0, 0, 0, NULL }
1.32 markus 93: };
94:
95: /*--*/
1.1 deraadt 96:
1.88 djm 97: /* Returns a comma-separated list of supported ciphers. */
98: char *
99: cipher_alg_list(void)
100: {
101: char *ret = NULL;
102: size_t nlen, rlen = 0;
103: const Cipher *c;
104:
105: for (c = ciphers; c->name != NULL; c++) {
106: if (c->number != SSH_CIPHER_SSH2)
107: continue;
108: if (ret != NULL)
109: ret[rlen++] = '\n';
110: nlen = strlen(c->name);
111: ret = xrealloc(ret, 1, rlen + nlen + 2);
112: memcpy(ret + rlen, c->name, nlen + 1);
113: rlen += nlen;
114: }
115: return ret;
116: }
117:
1.54 markus 118: u_int
1.66 jakob 119: cipher_blocksize(const Cipher *c)
1.51 markus 120: {
121: return (c->block_size);
122: }
1.60 deraadt 123:
1.54 markus 124: u_int
1.66 jakob 125: cipher_keylen(const Cipher *c)
1.51 markus 126: {
127: return (c->key_len);
128: }
1.60 deraadt 129:
1.54 markus 130: u_int
1.85 markus 131: cipher_authlen(const Cipher *c)
132: {
133: return (c->auth_len);
134: }
135:
136: u_int
137: cipher_ivlen(const Cipher *c)
138: {
139: return (c->iv_len ? c->iv_len : c->block_size);
140: }
141:
142: u_int
1.66 jakob 143: cipher_get_number(const Cipher *c)
1.53 markus 144: {
145: return (c->number);
1.82 markus 146: }
147:
148: u_int
149: cipher_is_cbc(const Cipher *c)
150: {
151: return (c->cbc_mode);
1.53 markus 152: }
1.51 markus 153:
1.41 markus 154: u_int
1.34 markus 155: cipher_mask_ssh1(int client)
1.1 deraadt 156: {
1.41 markus 157: u_int mask = 0;
1.48 deraadt 158: mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */
1.34 markus 159: mask |= 1 << SSH_CIPHER_BLOWFISH;
160: if (client) {
161: mask |= 1 << SSH_CIPHER_DES;
1.32 markus 162: }
163: return mask;
1.1 deraadt 164: }
165:
1.88 djm 166: const Cipher *
1.32 markus 167: cipher_by_name(const char *name)
168: {
1.88 djm 169: const Cipher *c;
1.32 markus 170: for (c = ciphers; c->name != NULL; c++)
1.73 djm 171: if (strcmp(c->name, name) == 0)
1.32 markus 172: return c;
173: return NULL;
174: }
175:
1.88 djm 176: const Cipher *
1.32 markus 177: cipher_by_number(int id)
178: {
1.88 djm 179: const Cipher *c;
1.32 markus 180: for (c = ciphers; c->name != NULL; c++)
181: if (c->number == id)
182: return c;
183: return NULL;
184: }
1.24 markus 185:
186: #define CIPHER_SEP ","
187: int
188: ciphers_valid(const char *names)
189: {
1.88 djm 190: const Cipher *c;
1.69 avsm 191: char *cipher_list, *cp;
1.24 markus 192: char *p;
193:
1.27 markus 194: if (names == NULL || strcmp(names, "") == 0)
1.24 markus 195: return 0;
1.69 avsm 196: cipher_list = cp = xstrdup(names);
1.32 markus 197: for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
1.48 deraadt 198: (p = strsep(&cp, CIPHER_SEP))) {
1.32 markus 199: c = cipher_by_name(p);
200: if (c == NULL || c->number != SSH_CIPHER_SSH2) {
201: debug("bad cipher %s [%s]", p, names);
1.89 ! djm 202: free(cipher_list);
1.24 markus 203: return 0;
1.32 markus 204: } else {
1.36 markus 205: debug3("cipher ok: %s [%s]", p, names);
1.24 markus 206: }
207: }
1.36 markus 208: debug3("ciphers ok: [%s]", names);
1.89 ! djm 209: free(cipher_list);
1.24 markus 210: return 1;
211: }
212:
1.18 markus 213: /*
214: * Parses the name of the cipher. Returns the number of the corresponding
215: * cipher, or -1 on error.
216: */
1.1 deraadt 217:
1.4 provos 218: int
219: cipher_number(const char *name)
1.1 deraadt 220: {
1.88 djm 221: const Cipher *c;
1.27 markus 222: if (name == NULL)
223: return -1;
1.73 djm 224: for (c = ciphers; c->name != NULL; c++)
225: if (strcasecmp(c->name, name) == 0)
226: return c->number;
227: return -1;
1.1 deraadt 228: }
229:
1.32 markus 230: char *
231: cipher_name(int id)
1.1 deraadt 232: {
1.88 djm 233: const Cipher *c = cipher_by_number(id);
1.32 markus 234: return (c==NULL) ? "<unknown>" : c->name;
1.1 deraadt 235: }
236:
1.26 markus 237: void
1.88 djm 238: cipher_init(CipherContext *cc, const Cipher *cipher,
1.52 markus 239: const u_char *key, u_int keylen, const u_char *iv, u_int ivlen,
1.69 avsm 240: int do_encrypt)
1.16 markus 241: {
1.52 markus 242: static int dowarn = 1;
243: const EVP_CIPHER *type;
244: int klen;
1.74 djm 245: u_char *junk, *discard;
1.52 markus 246:
247: if (cipher->number == SSH_CIPHER_DES) {
248: if (dowarn) {
249: error("Warning: use of DES is strongly discouraged "
250: "due to cryptographic weaknesses");
251: dowarn = 0;
252: }
253: if (keylen > 8)
254: keylen = 8;
255: }
256: cc->plaintext = (cipher->number == SSH_CIPHER_NONE);
1.85 markus 257: cc->encrypt = do_encrypt;
1.52 markus 258:
1.32 markus 259: if (keylen < cipher->key_len)
260: fatal("cipher_init: key length %d is insufficient for %s.",
261: keylen, cipher->name);
1.85 markus 262: if (iv != NULL && ivlen < cipher_ivlen(cipher))
1.32 markus 263: fatal("cipher_init: iv length %d is insufficient for %s.",
264: ivlen, cipher->name);
265: cc->cipher = cipher;
1.52 markus 266:
267: type = (*cipher->evptype)();
268:
269: EVP_CIPHER_CTX_init(&cc->evp);
270: if (EVP_CipherInit(&cc->evp, type, NULL, (u_char *)iv,
1.69 avsm 271: (do_encrypt == CIPHER_ENCRYPT)) == 0)
1.52 markus 272: fatal("cipher_init: EVP_CipherInit failed for %s",
273: cipher->name);
1.85 markus 274: if (cipher_authlen(cipher) &&
275: !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_SET_IV_FIXED,
276: -1, (u_char *)iv))
277: fatal("cipher_init: EVP_CTRL_GCM_SET_IV_FIXED failed for %s",
278: cipher->name);
1.52 markus 279: klen = EVP_CIPHER_CTX_key_length(&cc->evp);
1.76 djm 280: if (klen > 0 && keylen != (u_int)klen) {
1.62 markus 281: debug2("cipher_init: set keylen (%d -> %d)", klen, keylen);
1.52 markus 282: if (EVP_CIPHER_CTX_set_key_length(&cc->evp, keylen) == 0)
283: fatal("cipher_init: set keylen failed (%d -> %d)",
284: klen, keylen);
285: }
286: if (EVP_CipherInit(&cc->evp, NULL, (u_char *)key, NULL, -1) == 0)
287: fatal("cipher_init: EVP_CipherInit: set key failed for %s",
288: cipher->name);
1.74 djm 289:
1.77 djm 290: if (cipher->discard_len > 0) {
1.74 djm 291: junk = xmalloc(cipher->discard_len);
292: discard = xmalloc(cipher->discard_len);
293: if (EVP_Cipher(&cc->evp, discard, junk,
294: cipher->discard_len) == 0)
295: fatal("evp_crypt: EVP_Cipher failed during discard");
296: memset(discard, 0, cipher->discard_len);
1.89 ! djm 297: free(junk);
! 298: free(discard);
1.74 djm 299: }
1.1 deraadt 300: }
1.21 markus 301:
1.83 markus 302: /*
303: * cipher_crypt() operates as following:
304: * Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'.
305: * Theses bytes are treated as additional authenticated data for
306: * authenticated encryption modes.
307: * En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'.
1.85 markus 308: * Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag.
309: * This tag is written on encryption and verified on decryption.
1.83 markus 310: * Both 'aadlen' and 'authlen' can be set to 0.
311: */
1.26 markus 312: void
1.83 markus 313: cipher_crypt(CipherContext *cc, u_char *dest, const u_char *src,
1.85 markus 314: u_int len, u_int aadlen, u_int authlen)
1.32 markus 315: {
1.85 markus 316: if (authlen) {
317: u_char lastiv[1];
318:
319: if (authlen != cipher_authlen(cc->cipher))
320: fatal("%s: authlen mismatch %d", __func__, authlen);
321: /* increment IV */
322: if (!EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_IV_GEN,
323: 1, lastiv))
324: fatal("%s: EVP_CTRL_GCM_IV_GEN", __func__);
325: /* set tag on decyption */
326: if (!cc->encrypt &&
327: !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_SET_TAG,
328: authlen, (u_char *)src + aadlen + len))
329: fatal("%s: EVP_CTRL_GCM_SET_TAG", __func__);
330: }
331: if (aadlen) {
332: if (authlen &&
333: EVP_Cipher(&cc->evp, NULL, (u_char *)src, aadlen) < 0)
334: fatal("%s: EVP_Cipher(aad) failed", __func__);
1.83 markus 335: memcpy(dest, src, aadlen);
1.85 markus 336: }
1.32 markus 337: if (len % cc->cipher->block_size)
1.83 markus 338: fatal("%s: bad plaintext length %d", __func__, len);
339: if (EVP_Cipher(&cc->evp, dest + aadlen, (u_char *)src + aadlen,
340: len) < 0)
341: fatal("%s: EVP_Cipher failed", __func__);
1.85 markus 342: if (authlen) {
343: /* compute tag (on encrypt) or verify tag (on decrypt) */
1.86 djm 344: if (EVP_Cipher(&cc->evp, NULL, NULL, 0) < 0) {
345: if (cc->encrypt)
346: fatal("%s: EVP_Cipher(final) failed", __func__);
347: else
348: fatal("Decryption integrity check failed");
349: }
1.85 markus 350: if (cc->encrypt &&
351: !EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_GET_TAG,
352: authlen, dest + aadlen + len))
353: fatal("%s: EVP_CTRL_GCM_GET_TAG", __func__);
354: }
1.21 markus 355: }
356:
1.26 markus 357: void
1.51 markus 358: cipher_cleanup(CipherContext *cc)
1.16 markus 359: {
1.52 markus 360: if (EVP_CIPHER_CTX_cleanup(&cc->evp) == 0)
361: error("cipher_cleanup: EVP_CIPHER_CTX_cleanup failed");
1.16 markus 362: }
1.1 deraadt 363:
1.32 markus 364: /*
365: * Selects the cipher, and keys if by computing the MD5 checksum of the
366: * passphrase and using the resulting 16 bytes as the key.
367: */
1.1 deraadt 368:
1.26 markus 369: void
1.88 djm 370: cipher_set_key_string(CipherContext *cc, const Cipher *cipher,
1.69 avsm 371: const char *passphrase, int do_encrypt)
1.16 markus 372: {
1.32 markus 373: MD5_CTX md;
1.41 markus 374: u_char digest[16];
1.32 markus 375:
376: MD5_Init(&md);
377: MD5_Update(&md, (const u_char *)passphrase, strlen(passphrase));
378: MD5_Final(digest, &md);
1.16 markus 379:
1.69 avsm 380: cipher_init(cc, cipher, digest, 16, NULL, 0, do_encrypt);
1.16 markus 381:
1.32 markus 382: memset(digest, 0, sizeof(digest));
383: memset(&md, 0, sizeof(md));
1.52 markus 384: }
1.53 markus 385:
1.54 markus 386: /*
1.53 markus 387: * Exports an IV from the CipherContext required to export the key
388: * state back from the unprivileged child to the privileged parent
389: * process.
390: */
391:
392: int
1.66 jakob 393: cipher_get_keyiv_len(const CipherContext *cc)
1.53 markus 394: {
1.88 djm 395: const Cipher *c = cc->cipher;
1.53 markus 396: int ivlen;
397:
398: if (c->number == SSH_CIPHER_3DES)
399: ivlen = 24;
400: else
401: ivlen = EVP_CIPHER_CTX_iv_length(&cc->evp);
402: return (ivlen);
403: }
404:
405: void
406: cipher_get_keyiv(CipherContext *cc, u_char *iv, u_int len)
407: {
1.88 djm 408: const Cipher *c = cc->cipher;
1.53 markus 409: int evplen;
410:
411: switch (c->number) {
412: case SSH_CIPHER_SSH2:
413: case SSH_CIPHER_DES:
414: case SSH_CIPHER_BLOWFISH:
415: evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
1.76 djm 416: if (evplen <= 0)
1.53 markus 417: return;
1.76 djm 418: if ((u_int)evplen != len)
1.58 markus 419: fatal("%s: wrong iv length %d != %d", __func__,
1.53 markus 420: evplen, len);
1.85 markus 421: if (cipher_authlen(c)) {
422: if (!EVP_CIPHER_CTX_ctrl(&cc->evp, EVP_CTRL_GCM_IV_GEN,
423: len, iv))
424: fatal("%s: EVP_CTRL_GCM_IV_GEN", __func__);
425: } else
426: memcpy(iv, cc->evp.iv, len);
1.63 markus 427: break;
428: case SSH_CIPHER_3DES:
429: ssh1_3des_iv(&cc->evp, 0, iv, 24);
1.53 markus 430: break;
431: default:
1.58 markus 432: fatal("%s: bad cipher %d", __func__, c->number);
1.53 markus 433: }
434: }
435:
436: void
437: cipher_set_keyiv(CipherContext *cc, u_char *iv)
438: {
1.88 djm 439: const Cipher *c = cc->cipher;
1.53 markus 440: int evplen = 0;
441:
442: switch (c->number) {
443: case SSH_CIPHER_SSH2:
444: case SSH_CIPHER_DES:
445: case SSH_CIPHER_BLOWFISH:
446: evplen = EVP_CIPHER_CTX_iv_length(&cc->evp);
447: if (evplen == 0)
448: return;
1.85 markus 449: if (cipher_authlen(c)) {
450: if (!EVP_CIPHER_CTX_ctrl(&cc->evp,
451: EVP_CTRL_GCM_SET_IV_FIXED, -1, iv))
452: fatal("%s: EVP_CTRL_GCM_SET_IV_FIXED failed",
453: __func__);
454: } else
455: memcpy(cc->evp.iv, iv, evplen);
1.63 markus 456: break;
457: case SSH_CIPHER_3DES:
458: ssh1_3des_iv(&cc->evp, 1, iv, 24);
1.53 markus 459: break;
460: default:
1.58 markus 461: fatal("%s: bad cipher %d", __func__, c->number);
1.53 markus 462: }
463: }
464:
465: #define EVP_X_STATE(evp) (evp).cipher_data
466: #define EVP_X_STATE_LEN(evp) (evp).cipher->ctx_size
467:
468: int
1.66 jakob 469: cipher_get_keycontext(const CipherContext *cc, u_char *dat)
1.53 markus 470: {
1.88 djm 471: const Cipher *c = cc->cipher;
1.59 markus 472: int plen = 0;
1.53 markus 473:
1.87 djm 474: if (c->evptype == EVP_rc4) {
1.59 markus 475: plen = EVP_X_STATE_LEN(cc->evp);
1.53 markus 476: if (dat == NULL)
1.59 markus 477: return (plen);
478: memcpy(dat, EVP_X_STATE(cc->evp), plen);
1.53 markus 479: }
480: return (plen);
481: }
482:
483: void
484: cipher_set_keycontext(CipherContext *cc, u_char *dat)
485: {
1.88 djm 486: const Cipher *c = cc->cipher;
1.53 markus 487: int plen;
488:
1.87 djm 489: if (c->evptype == EVP_rc4) {
1.53 markus 490: plen = EVP_X_STATE_LEN(cc->evp);
491: memcpy(EVP_X_STATE(cc->evp), dat, plen);
492: }
1.1 deraadt 493: }
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