Annotation of src/usr.bin/ssh/cipher.c, Revision 1.34
1.1 deraadt 1: /*
1.30 deraadt 2: * Author: Tatu Ylonen <ylo@cs.hut.fi>
3: * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4: * All rights reserved
1.26 markus 5: *
1.30 deraadt 6: * As far as I am concerned, the code I have written for this software
7: * can be used freely for any purpose. Any derived versions of this
8: * software must be clearly marked as such, and if the derived work is
9: * incompatible with the protocol description in the RFC file, it must be
10: * called by a name other than "ssh" or "Secure Shell".
1.26 markus 11: *
12: *
1.30 deraadt 13: * Copyright (c) 1999 Niels Provos. All rights reserved.
14: * Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
1.26 markus 15: *
1.30 deraadt 16: * Redistribution and use in source and binary forms, with or without
17: * modification, are permitted provided that the following conditions
18: * are met:
19: * 1. Redistributions of source code must retain the above copyright
20: * notice, this list of conditions and the following disclaimer.
21: * 2. Redistributions in binary form must reproduce the above copyright
22: * notice, this list of conditions and the following disclaimer in the
23: * documentation and/or other materials provided with the distribution.
1.26 markus 24: *
1.30 deraadt 25: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
26: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
27: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
28: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
29: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
30: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
31: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
32: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
33: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
34: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.17 deraadt 35: */
1.1 deraadt 36:
37: #include "includes.h"
1.33 markus 38: RCSID("$OpenBSD: cipher.c,v 1.32 2000/10/11 20:27:23 markus Exp $");
1.1 deraadt 39:
40: #include "ssh.h"
1.24 markus 41: #include "xmalloc.h"
1.8 deraadt 42:
1.25 markus 43: #include <openssl/md5.h>
1.1 deraadt 44:
1.32 markus 45:
46: /* no encryption */
47: void
48: none_setkey(CipherContext *cc, const u_char *key, u_int keylen)
49: {
50: }
51: void
52: none_setiv(CipherContext *cc, const u_char *iv, u_int ivlen)
53: {
54: }
55: void
56: none_crypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
57: {
58: memcpy(dest, src, len);
59: }
60:
61: /* DES */
62: void
63: des_ssh1_setkey(CipherContext *cc, const u_char *key, u_int keylen)
64: {
1.34 ! markus 65: static int dowarn = 1;
! 66: if (dowarn) {
! 67: error("Warning: use of DES is strongly discouraged "
! 68: "due to cryptographic weaknesses");
! 69: dowarn = 0;
! 70: }
1.32 markus 71: des_set_key((void *)key, cc->u.des.key);
72: }
73: void
74: des_ssh1_setiv(CipherContext *cc, const u_char *iv, u_int ivlen)
75: {
76: memset(cc->u.des.iv, 0, sizeof(cc->u.des.iv));
77: }
78: void
79: des_ssh1_encrypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
80: {
81: des_ncbc_encrypt(src, dest, len, cc->u.des.key, &cc->u.des.iv,
82: DES_ENCRYPT);
83: }
84: void
85: des_ssh1_decrypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
86: {
87: des_ncbc_encrypt(src, dest, len, cc->u.des.key, &cc->u.des.iv,
88: DES_DECRYPT);
89: }
90:
91: /* 3DES */
92: void
93: des3_setkey(CipherContext *cc, const u_char *key, u_int keylen)
94: {
95: des_set_key((void *) key, cc->u.des3.key1);
96: des_set_key((void *) (key+8), cc->u.des3.key2);
97: des_set_key((void *) (key+16), cc->u.des3.key3);
98: }
99: void
100: des3_setiv(CipherContext *cc, const u_char *iv, u_int ivlen)
101: {
102: memset(cc->u.des3.iv2, 0, sizeof(cc->u.des3.iv2));
103: memset(cc->u.des3.iv3, 0, sizeof(cc->u.des3.iv3));
104: if (iv == NULL)
105: return;
106: memcpy(cc->u.des3.iv3, (char *)iv, 8);
107: }
108: void
109: des3_cbc_encrypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
110: {
111: des_ede3_cbc_encrypt(src, dest, len,
112: cc->u.des3.key1, cc->u.des3.key2, cc->u.des3.key3,
113: &cc->u.des3.iv3, DES_ENCRYPT);
114: }
115: void
116: des3_cbc_decrypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
117: {
118: des_ede3_cbc_encrypt(src, dest, len,
119: cc->u.des3.key1, cc->u.des3.key2, cc->u.des3.key3,
120: &cc->u.des3.iv3, DES_DECRYPT);
121: }
122:
1.1 deraadt 123: /*
1.24 markus 124: * This is used by SSH1:
125: *
1.23 deraadt 126: * What kind of triple DES are these 2 routines?
1.1 deraadt 127: *
128: * Why is there a redundant initialization vector?
129: *
130: * If only iv3 was used, then, this would till effect have been
131: * outer-cbc. However, there is also a private iv1 == iv2 which
132: * perhaps makes differential analysis easier. On the other hand, the
133: * private iv1 probably makes the CRC-32 attack ineffective. This is a
134: * result of that there is no longer any known iv1 to use when
135: * choosing the X block.
136: */
137: void
1.32 markus 138: des3_ssh1_setkey(CipherContext *cc, const u_char *key, u_int keylen)
139: {
140: des_set_key((void *) key, cc->u.des3.key1);
141: des_set_key((void *) (key+8), cc->u.des3.key2);
142: if (keylen <= 16)
143: des_set_key((void *) key, cc->u.des3.key3);
144: else
145: des_set_key((void *) (key+16), cc->u.des3.key3);
146: }
147: void
148: des3_ssh1_encrypt(CipherContext *cc, u_char *dest, const u_char *src,
149: u_int len)
1.1 deraadt 150: {
1.16 markus 151: des_cblock iv1;
1.32 markus 152: des_cblock *iv2 = &cc->u.des3.iv2;
153: des_cblock *iv3 = &cc->u.des3.iv3;
1.1 deraadt 154:
1.16 markus 155: memcpy(&iv1, iv2, 8);
1.1 deraadt 156:
1.32 markus 157: des_cbc_encrypt(src, dest, len, cc->u.des3.key1, &iv1, DES_ENCRYPT);
1.16 markus 158: memcpy(&iv1, dest + len - 8, 8);
1.1 deraadt 159:
1.32 markus 160: des_cbc_encrypt(dest, dest, len, cc->u.des3.key2, iv2, DES_DECRYPT);
1.16 markus 161: memcpy(iv2, &iv1, 8); /* Note how iv1 == iv2 on entry and exit. */
1.1 deraadt 162:
1.32 markus 163: des_cbc_encrypt(dest, dest, len, cc->u.des3.key3, iv3, DES_ENCRYPT);
1.16 markus 164: memcpy(iv3, dest + len - 8, 8);
1.1 deraadt 165: }
166: void
1.32 markus 167: des3_ssh1_decrypt(CipherContext *cc, u_char *dest, const u_char *src,
168: u_int len)
1.1 deraadt 169: {
1.16 markus 170: des_cblock iv1;
1.32 markus 171: des_cblock *iv2 = &cc->u.des3.iv2;
172: des_cblock *iv3 = &cc->u.des3.iv3;
1.1 deraadt 173:
1.16 markus 174: memcpy(&iv1, iv2, 8);
1.1 deraadt 175:
1.32 markus 176: des_cbc_encrypt(src, dest, len, cc->u.des3.key3, iv3, DES_DECRYPT);
1.16 markus 177: memcpy(iv3, src + len - 8, 8);
1.1 deraadt 178:
1.32 markus 179: des_cbc_encrypt(dest, dest, len, cc->u.des3.key2, iv2, DES_ENCRYPT);
1.16 markus 180: memcpy(iv2, dest + len - 8, 8);
1.1 deraadt 181:
1.32 markus 182: des_cbc_encrypt(dest, dest, len, cc->u.des3.key1, &iv1, DES_DECRYPT);
1.16 markus 183: /* memcpy(&iv1, iv2, 8); */
184: /* Note how iv1 == iv2 on entry and exit. */
1.1 deraadt 185: }
186:
1.32 markus 187: /* Blowfish */
188: void
189: blowfish_setkey(CipherContext *cc, const u_char *key, u_int keylen)
190: {
191: BF_set_key(&cc->u.bf.key, keylen, (unsigned char *)key);
192: }
193: void
194: blowfish_setiv(CipherContext *cc, const u_char *iv, u_int ivlen)
195: {
196: if (iv == NULL)
197: memset(cc->u.bf.iv, 0, 8);
198: else
199: memcpy(cc->u.bf.iv, (char *)iv, 8);
200: }
201: void
202: blowfish_cbc_encrypt(CipherContext *cc, u_char *dest, const u_char *src,
203: u_int len)
204: {
205: BF_cbc_encrypt((void *)src, dest, len, &cc->u.bf.key, cc->u.bf.iv,
206: BF_ENCRYPT);
207: }
208: void
209: blowfish_cbc_decrypt(CipherContext *cc, u_char *dest, const u_char *src,
210: u_int len)
211: {
212: BF_cbc_encrypt((void *)src, dest, len, &cc->u.bf.key, cc->u.bf.iv,
213: BF_DECRYPT);
214: }
215:
1.1 deraadt 216: /*
1.24 markus 217: * SSH1 uses a variation on Blowfish, all bytes must be swapped before
1.1 deraadt 218: * and after encryption/decryption. Thus the swap_bytes stuff (yuk).
219: */
1.16 markus 220: static void
1.1 deraadt 221: swap_bytes(const unsigned char *src, unsigned char *dst_, int n)
222: {
1.16 markus 223: /* dst must be properly aligned. */
224: u_int32_t *dst = (u_int32_t *) dst_;
225: union {
226: u_int32_t i;
227: char c[4];
228: } t;
229:
230: /* Process 8 bytes every lap. */
231: for (n = n / 8; n > 0; n--) {
232: t.c[3] = *src++;
233: t.c[2] = *src++;
234: t.c[1] = *src++;
235: t.c[0] = *src++;
236: *dst++ = t.i;
237:
238: t.c[3] = *src++;
239: t.c[2] = *src++;
240: t.c[1] = *src++;
241: t.c[0] = *src++;
242: *dst++ = t.i;
243: }
1.1 deraadt 244: }
245:
1.32 markus 246: void
247: blowfish_ssh1_encrypt(CipherContext *cc, u_char *dest, const u_char *src,
248: u_int len)
249: {
250: swap_bytes(src, dest, len);
251: BF_cbc_encrypt((void *)dest, dest, len, &cc->u.bf.key, cc->u.bf.iv,
252: BF_ENCRYPT);
253: swap_bytes(dest, dest, len);
254: }
255: void
256: blowfish_ssh1_decrypt(CipherContext *cc, u_char *dest, const u_char *src,
257: u_int len)
1.4 provos 258: {
1.32 markus 259: swap_bytes(src, dest, len);
260: BF_cbc_encrypt((void *)dest, dest, len, &cc->u.bf.key, cc->u.bf.iv,
261: BF_DECRYPT);
262: swap_bytes(dest, dest, len);
263: }
1.1 deraadt 264:
1.32 markus 265: /* alleged rc4 */
266: void
267: arcfour_setkey(CipherContext *cc, const u_char *key, u_int keylen)
268: {
269: RC4_set_key(&cc->u.rc4, keylen, (u_char *)key);
270: }
271: void
272: arcfour_crypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
273: {
274: RC4(&cc->u.rc4, len, (u_char *)src, dest);
275: }
1.1 deraadt 276:
1.32 markus 277: /* CAST */
278: void
279: cast_setkey(CipherContext *cc, const u_char *key, u_int keylen)
280: {
281: CAST_set_key(&cc->u.cast.key, keylen, (unsigned char *) key);
282: }
283: void
284: cast_setiv(CipherContext *cc, const u_char *iv, u_int ivlen)
1.1 deraadt 285: {
1.32 markus 286: if (iv == NULL)
287: fatal("no IV for %s.", cc->cipher->name);
288: memcpy(cc->u.cast.iv, (char *)iv, 8);
1.22 markus 289: }
1.32 markus 290: void
291: cast_cbc_encrypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
1.22 markus 292: {
1.32 markus 293: CAST_cbc_encrypt(src, dest, len, &cc->u.cast.key, cc->u.cast.iv,
294: CAST_ENCRYPT);
1.1 deraadt 295: }
1.32 markus 296: void
297: cast_cbc_decrypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
1.22 markus 298: {
1.32 markus 299: CAST_cbc_encrypt(src, dest, len, &cc->u.cast.key, cc->u.cast.iv,
300: CAST_DECRYPT);
1.22 markus 301: }
1.1 deraadt 302:
1.32 markus 303: /*--*/
304:
305: Cipher ciphers[] = {
306: { "none",
307: SSH_CIPHER_NONE, 8, 0,
308: none_setkey, none_setiv,
309: none_crypt, none_crypt },
1.34 ! markus 310: { "des",
! 311: SSH_CIPHER_DES, 8, 8,
! 312: des_ssh1_setkey, des_ssh1_setiv,
! 313: des_ssh1_encrypt, des_ssh1_decrypt },
1.32 markus 314: { "3des",
315: SSH_CIPHER_3DES, 8, 16,
316: des3_ssh1_setkey, des3_setiv,
317: des3_ssh1_encrypt, des3_ssh1_decrypt },
318: { "blowfish",
319: SSH_CIPHER_BLOWFISH, 8, 16,
320: blowfish_setkey, blowfish_setiv,
321: blowfish_ssh1_encrypt, blowfish_ssh1_decrypt },
322:
323: { "3des-cbc",
324: SSH_CIPHER_SSH2, 8, 24,
325: des3_setkey, des3_setiv,
326: des3_cbc_encrypt, des3_cbc_decrypt },
327: { "blowfish-cbc",
328: SSH_CIPHER_SSH2, 8, 16,
329: blowfish_setkey, blowfish_setiv,
330: blowfish_cbc_encrypt, blowfish_cbc_decrypt },
331: { "cast128-cbc",
332: SSH_CIPHER_SSH2, 8, 16,
333: cast_setkey, cast_setiv,
334: cast_cbc_encrypt, cast_cbc_decrypt },
335: { "arcfour",
336: SSH_CIPHER_SSH2, 8, 16,
337: arcfour_setkey, none_setiv,
338: arcfour_crypt, arcfour_crypt },
339: { NULL, SSH_CIPHER_ILLEGAL, 0, 0, NULL, NULL, NULL, NULL }
340: };
341:
342: /*--*/
1.1 deraadt 343:
1.32 markus 344: unsigned int
1.34 ! markus 345: cipher_mask_ssh1(int client)
1.1 deraadt 346: {
1.32 markus 347: unsigned int mask = 0;
1.34 ! markus 348: mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */
! 349: mask |= 1 << SSH_CIPHER_BLOWFISH;
! 350: if (client) {
! 351: mask |= 1 << SSH_CIPHER_DES;
1.32 markus 352: }
353: return mask;
1.1 deraadt 354: }
355:
1.32 markus 356: Cipher *
357: cipher_by_name(const char *name)
358: {
359: Cipher *c;
360: for (c = ciphers; c->name != NULL; c++)
361: if (strcasecmp(c->name, name) == 0)
362: return c;
363: return NULL;
364: }
365:
366: Cipher *
367: cipher_by_number(int id)
368: {
369: Cipher *c;
370: for (c = ciphers; c->name != NULL; c++)
371: if (c->number == id)
372: return c;
373: return NULL;
374: }
1.24 markus 375:
376: #define CIPHER_SEP ","
377: int
378: ciphers_valid(const char *names)
379: {
1.32 markus 380: Cipher *c;
1.29 ho 381: char *ciphers, *cp;
1.24 markus 382: char *p;
383:
1.27 markus 384: if (names == NULL || strcmp(names, "") == 0)
1.24 markus 385: return 0;
1.29 ho 386: ciphers = cp = xstrdup(names);
1.32 markus 387: for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
1.29 ho 388: (p = strsep(&cp, CIPHER_SEP))) {
1.32 markus 389: c = cipher_by_name(p);
390: if (c == NULL || c->number != SSH_CIPHER_SSH2) {
391: debug("bad cipher %s [%s]", p, names);
1.24 markus 392: xfree(ciphers);
393: return 0;
1.32 markus 394: } else {
395: debug("cipher ok: %s [%s]", p, names);
1.24 markus 396: }
397: }
1.32 markus 398: debug("ciphers ok: [%s]", names);
1.24 markus 399: xfree(ciphers);
400: return 1;
401: }
402:
1.18 markus 403: /*
404: * Parses the name of the cipher. Returns the number of the corresponding
405: * cipher, or -1 on error.
406: */
1.1 deraadt 407:
1.4 provos 408: int
409: cipher_number(const char *name)
1.1 deraadt 410: {
1.32 markus 411: Cipher *c;
1.27 markus 412: if (name == NULL)
413: return -1;
1.32 markus 414: c = cipher_by_name(name);
415: return (c==NULL) ? -1 : c->number;
1.1 deraadt 416: }
417:
1.32 markus 418: char *
419: cipher_name(int id)
1.1 deraadt 420: {
1.32 markus 421: Cipher *c = cipher_by_number(id);
422: return (c==NULL) ? "<unknown>" : c->name;
1.1 deraadt 423: }
424:
1.26 markus 425: void
1.32 markus 426: cipher_init(CipherContext *cc, Cipher *cipher,
427: const u_char *key, u_int keylen, const u_char *iv, u_int ivlen)
1.16 markus 428: {
1.32 markus 429: if (keylen < cipher->key_len)
430: fatal("cipher_init: key length %d is insufficient for %s.",
431: keylen, cipher->name);
432: if (iv != NULL && ivlen < cipher->block_size)
433: fatal("cipher_init: iv length %d is insufficient for %s.",
434: ivlen, cipher->name);
435: cc->cipher = cipher;
436: cipher->setkey(cc, key, keylen);
437: cipher->setiv(cc, iv, ivlen);
1.1 deraadt 438: }
1.21 markus 439:
1.26 markus 440: void
1.32 markus 441: cipher_encrypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
442: {
443: if (len % cc->cipher->block_size)
444: fatal("cipher_encrypt: bad plaintext length %d", len);
445: cc->cipher->encrypt(cc, dest, src, len);
1.21 markus 446: }
447:
1.26 markus 448: void
1.32 markus 449: cipher_decrypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
1.16 markus 450: {
1.32 markus 451: if (len % cc->cipher->block_size)
452: fatal("cipher_decrypt: bad ciphertext length %d", len);
453: cc->cipher->decrypt(cc, dest, src, len);
1.16 markus 454: }
1.1 deraadt 455:
1.32 markus 456: /*
457: * Selects the cipher, and keys if by computing the MD5 checksum of the
458: * passphrase and using the resulting 16 bytes as the key.
459: */
1.1 deraadt 460:
1.26 markus 461: void
1.32 markus 462: cipher_set_key_string(CipherContext *cc, Cipher *cipher,
463: const char *passphrase)
1.16 markus 464: {
1.32 markus 465: MD5_CTX md;
466: unsigned char digest[16];
467:
468: MD5_Init(&md);
469: MD5_Update(&md, (const u_char *)passphrase, strlen(passphrase));
470: MD5_Final(digest, &md);
1.16 markus 471:
1.32 markus 472: cipher_init(cc, cipher, digest, 16, NULL, 0);
1.16 markus 473:
1.32 markus 474: memset(digest, 0, sizeof(digest));
475: memset(&md, 0, sizeof(md));
1.1 deraadt 476: }
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