Annotation of src/usr.bin/ssh/cipher.c, Revision 1.24
1.1 deraadt 1: /*
1.17 deraadt 2: *
3: * cipher.c
4: *
5: * Author: Tatu Ylonen <ylo@cs.hut.fi>
6: *
7: * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
8: * All rights reserved
9: *
10: * Created: Wed Apr 19 17:41:39 1995 ylo
11: *
12: */
1.1 deraadt 13:
14: #include "includes.h"
1.24 ! markus 15: RCSID("$Id: cipher.c,v 1.23 2000/04/12 00:18:20 deraadt Exp $");
1.1 deraadt 16:
17: #include "ssh.h"
18: #include "cipher.h"
1.24 ! markus 19: #include "xmalloc.h"
1.8 deraadt 20:
1.12 deraadt 21: #include <ssl/md5.h>
1.1 deraadt 22:
23: /*
1.24 ! markus 24: * This is used by SSH1:
! 25: *
1.23 deraadt 26: * What kind of triple DES are these 2 routines?
1.1 deraadt 27: *
28: * Why is there a redundant initialization vector?
29: *
30: * If only iv3 was used, then, this would till effect have been
31: * outer-cbc. However, there is also a private iv1 == iv2 which
32: * perhaps makes differential analysis easier. On the other hand, the
33: * private iv1 probably makes the CRC-32 attack ineffective. This is a
34: * result of that there is no longer any known iv1 to use when
35: * choosing the X block.
36: */
37: void
38: SSH_3CBC_ENCRYPT(des_key_schedule ks1,
1.16 markus 39: des_key_schedule ks2, des_cblock * iv2,
40: des_key_schedule ks3, des_cblock * iv3,
1.19 markus 41: unsigned char *dest, unsigned char *src,
1.1 deraadt 42: unsigned int len)
43: {
1.16 markus 44: des_cblock iv1;
1.1 deraadt 45:
1.16 markus 46: memcpy(&iv1, iv2, 8);
1.1 deraadt 47:
1.16 markus 48: des_cbc_encrypt(src, dest, len, ks1, &iv1, DES_ENCRYPT);
49: memcpy(&iv1, dest + len - 8, 8);
1.1 deraadt 50:
1.16 markus 51: des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_DECRYPT);
52: memcpy(iv2, &iv1, 8); /* Note how iv1 == iv2 on entry and exit. */
1.1 deraadt 53:
1.16 markus 54: des_cbc_encrypt(dest, dest, len, ks3, iv3, DES_ENCRYPT);
55: memcpy(iv3, dest + len - 8, 8);
1.1 deraadt 56: }
57:
58: void
59: SSH_3CBC_DECRYPT(des_key_schedule ks1,
1.16 markus 60: des_key_schedule ks2, des_cblock * iv2,
61: des_key_schedule ks3, des_cblock * iv3,
1.19 markus 62: unsigned char *dest, unsigned char *src,
1.1 deraadt 63: unsigned int len)
64: {
1.16 markus 65: des_cblock iv1;
1.1 deraadt 66:
1.16 markus 67: memcpy(&iv1, iv2, 8);
1.1 deraadt 68:
1.16 markus 69: des_cbc_encrypt(src, dest, len, ks3, iv3, DES_DECRYPT);
70: memcpy(iv3, src + len - 8, 8);
1.1 deraadt 71:
1.16 markus 72: des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_ENCRYPT);
73: memcpy(iv2, dest + len - 8, 8);
1.1 deraadt 74:
1.16 markus 75: des_cbc_encrypt(dest, dest, len, ks1, &iv1, DES_DECRYPT);
76: /* memcpy(&iv1, iv2, 8); */
77: /* Note how iv1 == iv2 on entry and exit. */
1.1 deraadt 78: }
79:
80: /*
1.24 ! markus 81: * SSH1 uses a variation on Blowfish, all bytes must be swapped before
1.1 deraadt 82: * and after encryption/decryption. Thus the swap_bytes stuff (yuk).
83: */
1.16 markus 84: static void
1.1 deraadt 85: swap_bytes(const unsigned char *src, unsigned char *dst_, int n)
86: {
1.16 markus 87: /* dst must be properly aligned. */
88: u_int32_t *dst = (u_int32_t *) dst_;
89: union {
90: u_int32_t i;
91: char c[4];
92: } t;
93:
94: /* Process 8 bytes every lap. */
95: for (n = n / 8; n > 0; n--) {
96: t.c[3] = *src++;
97: t.c[2] = *src++;
98: t.c[1] = *src++;
99: t.c[0] = *src++;
100: *dst++ = t.i;
101:
102: t.c[3] = *src++;
103: t.c[2] = *src++;
104: t.c[1] = *src++;
105: t.c[0] = *src++;
106: *dst++ = t.i;
107: }
1.1 deraadt 108: }
109:
1.18 markus 110: /*
111: * Names of all encryption algorithms.
112: * These must match the numbers defined in cipher.h.
113: */
1.1 deraadt 114: static char *cipher_names[] =
1.4 provos 115: {
1.16 markus 116: "none",
117: "idea",
118: "des",
119: "3des",
120: "tss",
121: "rc4",
1.21 markus 122: "blowfish",
123: "reserved",
124: "blowfish-cbc",
125: "3des-cbc",
126: "arcfour",
127: "cast128-cbc"
1.1 deraadt 128: };
129:
1.18 markus 130: /*
131: * Returns a bit mask indicating which ciphers are supported by this
132: * implementation. The bit mask has the corresponding bit set of each
133: * supported cipher.
134: */
1.1 deraadt 135:
1.16 markus 136: unsigned int
1.22 markus 137: cipher_mask1()
1.1 deraadt 138: {
1.16 markus 139: unsigned int mask = 0;
140: mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */
141: mask |= 1 << SSH_CIPHER_BLOWFISH;
1.22 markus 142: return mask;
143: }
144: unsigned int
145: cipher_mask2()
146: {
147: unsigned int mask = 0;
1.21 markus 148: mask |= 1 << SSH_CIPHER_BLOWFISH_CBC;
149: mask |= 1 << SSH_CIPHER_3DES_CBC;
150: mask |= 1 << SSH_CIPHER_ARCFOUR;
151: mask |= 1 << SSH_CIPHER_CAST128_CBC;
1.16 markus 152: return mask;
1.1 deraadt 153: }
1.22 markus 154: unsigned int
155: cipher_mask()
156: {
157: return cipher_mask1() | cipher_mask2();
158: }
1.1 deraadt 159:
160: /* Returns the name of the cipher. */
161:
1.16 markus 162: const char *
163: cipher_name(int cipher)
1.1 deraadt 164: {
1.16 markus 165: if (cipher < 0 || cipher >= sizeof(cipher_names) / sizeof(cipher_names[0]) ||
166: cipher_names[cipher] == NULL)
1.24 ! markus 167: fatal("cipher_name: bad cipher name: %d", cipher);
1.16 markus 168: return cipher_names[cipher];
1.1 deraadt 169: }
170:
1.24 ! markus 171: /* Returns 1 if the name of the ciphers are valid. */
! 172:
! 173: #define CIPHER_SEP ","
! 174: int
! 175: ciphers_valid(const char *names)
! 176: {
! 177: char *ciphers;
! 178: char *p;
! 179: int i;
! 180:
! 181: if (strcmp(names, "") == 0)
! 182: return 0;
! 183: ciphers = xstrdup(names);
! 184: for ((p = strtok(ciphers, CIPHER_SEP)); p; (p = strtok(NULL, CIPHER_SEP))) {
! 185: i = cipher_number(p);
! 186: if (i == -1 || !(cipher_mask2() & (1 << i))) {
! 187: xfree(ciphers);
! 188: return 0;
! 189: }
! 190: }
! 191: xfree(ciphers);
! 192: return 1;
! 193: }
! 194:
1.18 markus 195: /*
196: * Parses the name of the cipher. Returns the number of the corresponding
197: * cipher, or -1 on error.
198: */
1.1 deraadt 199:
1.4 provos 200: int
201: cipher_number(const char *name)
1.1 deraadt 202: {
1.16 markus 203: int i;
204: for (i = 0; i < sizeof(cipher_names) / sizeof(cipher_names[0]); i++)
205: if (strcmp(cipher_names[i], name) == 0 &&
206: (cipher_mask() & (1 << i)))
207: return i;
208: return -1;
1.1 deraadt 209: }
210:
1.18 markus 211: /*
212: * Selects the cipher, and keys if by computing the MD5 checksum of the
213: * passphrase and using the resulting 16 bytes as the key.
214: */
1.1 deraadt 215:
1.16 markus 216: void
1.22 markus 217: cipher_set_key_string(CipherContext *context, int cipher, const char *passphrase)
1.1 deraadt 218: {
1.16 markus 219: MD5_CTX md;
220: unsigned char digest[16];
221:
222: MD5_Init(&md);
223: MD5_Update(&md, (const unsigned char *) passphrase, strlen(passphrase));
224: MD5_Final(digest, &md);
225:
1.22 markus 226: cipher_set_key(context, cipher, digest, 16);
1.16 markus 227:
228: memset(digest, 0, sizeof(digest));
229: memset(&md, 0, sizeof(md));
1.1 deraadt 230: }
231:
232: /* Selects the cipher to use and sets the key. */
233:
1.16 markus 234: void
1.22 markus 235: cipher_set_key(CipherContext *context, int cipher, const unsigned char *key,
236: int keylen)
1.16 markus 237: {
238: unsigned char padded[32];
239:
240: /* Set cipher type. */
241: context->type = cipher;
242:
243: /* Get 32 bytes of key data. Pad if necessary. (So that code
244: below does not need to worry about key size). */
245: memset(padded, 0, sizeof(padded));
246: memcpy(padded, key, keylen < sizeof(padded) ? keylen : sizeof(padded));
247:
248: /* Initialize the initialization vector. */
249: switch (cipher) {
250: case SSH_CIPHER_NONE:
1.18 markus 251: /*
252: * Has to stay for authfile saving of private key with no
253: * passphrase
254: */
1.16 markus 255: break;
256:
257: case SSH_CIPHER_3DES:
1.18 markus 258: /*
259: * Note: the least significant bit of each byte of key is
260: * parity, and must be ignored by the implementation. 16
261: * bytes of key are used (first and last keys are the same).
262: */
1.16 markus 263: if (keylen < 16)
264: error("Key length %d is insufficient for 3DES.", keylen);
265: des_set_key((void *) padded, context->u.des3.key1);
266: des_set_key((void *) (padded + 8), context->u.des3.key2);
267: if (keylen <= 16)
268: des_set_key((void *) padded, context->u.des3.key3);
269: else
270: des_set_key((void *) (padded + 16), context->u.des3.key3);
271: memset(context->u.des3.iv2, 0, sizeof(context->u.des3.iv2));
272: memset(context->u.des3.iv3, 0, sizeof(context->u.des3.iv3));
273: break;
274:
275: case SSH_CIPHER_BLOWFISH:
1.21 markus 276: if (keylen < 16)
277: error("Key length %d is insufficient for blowfish.", keylen);
1.16 markus 278: BF_set_key(&context->u.bf.key, keylen, padded);
279: memset(context->u.bf.iv, 0, 8);
280: break;
281:
1.21 markus 282: case SSH_CIPHER_3DES_CBC:
283: case SSH_CIPHER_BLOWFISH_CBC:
284: case SSH_CIPHER_ARCFOUR:
285: case SSH_CIPHER_CAST128_CBC:
286: fatal("cipher_set_key: illegal cipher: %s", cipher_name(cipher));
287: break;
288:
1.16 markus 289: default:
290: fatal("cipher_set_key: unknown cipher: %s", cipher_name(cipher));
291: }
292: memset(padded, 0, sizeof(padded));
1.1 deraadt 293: }
1.21 markus 294:
295: void
296: cipher_set_key_iv(CipherContext * context, int cipher,
297: const unsigned char *key, int keylen,
298: const unsigned char *iv, int ivlen)
299: {
300: /* Set cipher type. */
301: context->type = cipher;
302:
303: /* Initialize the initialization vector. */
304: switch (cipher) {
305: case SSH_CIPHER_NONE:
306: break;
307:
308: case SSH_CIPHER_3DES:
309: case SSH_CIPHER_BLOWFISH:
310: fatal("cipher_set_key_iv: illegal cipher: %s", cipher_name(cipher));
311: break;
312:
313: case SSH_CIPHER_3DES_CBC:
314: if (keylen < 24)
315: error("Key length %d is insufficient for 3des-cbc.", keylen);
316: des_set_key((void *) key, context->u.des3.key1);
317: des_set_key((void *) (key+8), context->u.des3.key2);
318: des_set_key((void *) (key+16), context->u.des3.key3);
319: if (ivlen < 8)
320: error("IV length %d is insufficient for 3des-cbc.", ivlen);
321: memcpy(context->u.des3.iv3, (char *)iv, 8);
322: break;
323:
324: case SSH_CIPHER_BLOWFISH_CBC:
325: if (keylen < 16)
326: error("Key length %d is insufficient for blowfish.", keylen);
327: if (ivlen < 8)
328: error("IV length %d is insufficient for blowfish.", ivlen);
329: BF_set_key(&context->u.bf.key, keylen, (unsigned char *)key);
330: memcpy(context->u.bf.iv, (char *)iv, 8);
331: break;
332:
333: case SSH_CIPHER_ARCFOUR:
334: if (keylen < 16)
335: error("Key length %d is insufficient for arcfour.", keylen);
336: RC4_set_key(&context->u.rc4, keylen, (unsigned char *)key);
337: break;
338:
339: case SSH_CIPHER_CAST128_CBC:
340: if (keylen < 16)
341: error("Key length %d is insufficient for cast128.", keylen);
342: if (ivlen < 8)
343: error("IV length %d is insufficient for cast128.", ivlen);
344: CAST_set_key(&context->u.cast.key, keylen, (unsigned char *) key);
345: memcpy(context->u.cast.iv, (char *)iv, 8);
346: break;
347:
348: default:
349: fatal("cipher_set_key: unknown cipher: %s", cipher_name(cipher));
350: }
351: }
352:
1.1 deraadt 353: /* Encrypts data using the cipher. */
354:
1.16 markus 355: void
356: cipher_encrypt(CipherContext *context, unsigned char *dest,
357: const unsigned char *src, unsigned int len)
358: {
359: if ((len & 7) != 0)
360: fatal("cipher_encrypt: bad plaintext length %d", len);
361:
362: switch (context->type) {
363: case SSH_CIPHER_NONE:
364: memcpy(dest, src, len);
365: break;
366:
367: case SSH_CIPHER_3DES:
368: SSH_3CBC_ENCRYPT(context->u.des3.key1,
369: context->u.des3.key2, &context->u.des3.iv2,
370: context->u.des3.key3, &context->u.des3.iv3,
1.19 markus 371: dest, (unsigned char *) src, len);
1.16 markus 372: break;
373:
374: case SSH_CIPHER_BLOWFISH:
375: swap_bytes(src, dest, len);
376: BF_cbc_encrypt(dest, dest, len,
377: &context->u.bf.key, context->u.bf.iv,
378: BF_ENCRYPT);
379: swap_bytes(dest, dest, len);
380: break;
381:
1.21 markus 382: case SSH_CIPHER_BLOWFISH_CBC:
383: BF_cbc_encrypt((void *)src, dest, len,
384: &context->u.bf.key, context->u.bf.iv,
385: BF_ENCRYPT);
386: break;
387:
388: case SSH_CIPHER_3DES_CBC:
389: des_ede3_cbc_encrypt(src, dest, len,
390: context->u.des3.key1, context->u.des3.key2,
391: context->u.des3.key3, &context->u.des3.iv3, DES_ENCRYPT);
392: break;
393:
394: case SSH_CIPHER_ARCFOUR:
395: RC4(&context->u.rc4, len, (unsigned char *)src, dest);
396: break;
397:
398: case SSH_CIPHER_CAST128_CBC:
399: CAST_cbc_encrypt(src, dest, len,
400: &context->u.cast.key, context->u.cast.iv, CAST_ENCRYPT);
401: break;
402:
1.16 markus 403: default:
404: fatal("cipher_encrypt: unknown cipher: %s", cipher_name(context->type));
405: }
406: }
1.1 deraadt 407:
408: /* Decrypts data using the cipher. */
409:
1.16 markus 410: void
411: cipher_decrypt(CipherContext *context, unsigned char *dest,
412: const unsigned char *src, unsigned int len)
413: {
414: if ((len & 7) != 0)
415: fatal("cipher_decrypt: bad ciphertext length %d", len);
416:
417: switch (context->type) {
418: case SSH_CIPHER_NONE:
419: memcpy(dest, src, len);
420: break;
421:
422: case SSH_CIPHER_3DES:
423: SSH_3CBC_DECRYPT(context->u.des3.key1,
424: context->u.des3.key2, &context->u.des3.iv2,
425: context->u.des3.key3, &context->u.des3.iv3,
1.19 markus 426: dest, (unsigned char *) src, len);
1.16 markus 427: break;
428:
429: case SSH_CIPHER_BLOWFISH:
430: swap_bytes(src, dest, len);
431: BF_cbc_encrypt((void *) dest, dest, len,
432: &context->u.bf.key, context->u.bf.iv,
433: BF_DECRYPT);
434: swap_bytes(dest, dest, len);
1.21 markus 435: break;
436:
437: case SSH_CIPHER_BLOWFISH_CBC:
438: BF_cbc_encrypt((void *) src, dest, len,
439: &context->u.bf.key, context->u.bf.iv,
440: BF_DECRYPT);
441: break;
442:
443: case SSH_CIPHER_3DES_CBC:
444: des_ede3_cbc_encrypt(src, dest, len,
445: context->u.des3.key1, context->u.des3.key2,
446: context->u.des3.key3, &context->u.des3.iv3, DES_DECRYPT);
447: break;
448:
449: case SSH_CIPHER_ARCFOUR:
450: RC4(&context->u.rc4, len, (unsigned char *)src, dest);
451: break;
452:
453: case SSH_CIPHER_CAST128_CBC:
454: CAST_cbc_encrypt(src, dest, len,
455: &context->u.cast.key, context->u.cast.iv, CAST_DECRYPT);
1.16 markus 456: break;
457:
458: default:
459: fatal("cipher_decrypt: unknown cipher: %s", cipher_name(context->type));
460: }
1.1 deraadt 461: }
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