Annotation of src/usr.bin/ssh/cipher.c, Revision 1.21
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"
1.21 ! markus 15: RCSID("$Id: cipher.c,v 1.21 2000/03/22 13:40:45 markus Exp $");
1.1 deraadt 16:
17: #include "ssh.h"
18: #include "cipher.h"
1.8 deraadt 19:
1.12 deraadt 20: #include <ssl/md5.h>
1.1 deraadt 21:
22: /*
23: * What kind of tripple DES are these 2 routines?
24: *
25: * Why is there a redundant initialization vector?
26: *
27: * If only iv3 was used, then, this would till effect have been
28: * outer-cbc. However, there is also a private iv1 == iv2 which
29: * perhaps makes differential analysis easier. On the other hand, the
30: * private iv1 probably makes the CRC-32 attack ineffective. This is a
31: * result of that there is no longer any known iv1 to use when
32: * choosing the X block.
33: */
34: void
35: SSH_3CBC_ENCRYPT(des_key_schedule ks1,
1.16 markus 36: des_key_schedule ks2, des_cblock * iv2,
37: des_key_schedule ks3, des_cblock * iv3,
1.19 markus 38: unsigned char *dest, unsigned char *src,
1.1 deraadt 39: unsigned int len)
40: {
1.16 markus 41: des_cblock iv1;
1.1 deraadt 42:
1.16 markus 43: memcpy(&iv1, iv2, 8);
1.1 deraadt 44:
1.16 markus 45: des_cbc_encrypt(src, dest, len, ks1, &iv1, DES_ENCRYPT);
46: memcpy(&iv1, dest + len - 8, 8);
1.1 deraadt 47:
1.16 markus 48: des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_DECRYPT);
49: memcpy(iv2, &iv1, 8); /* Note how iv1 == iv2 on entry and exit. */
1.1 deraadt 50:
1.16 markus 51: des_cbc_encrypt(dest, dest, len, ks3, iv3, DES_ENCRYPT);
52: memcpy(iv3, dest + len - 8, 8);
1.1 deraadt 53: }
54:
55: void
56: SSH_3CBC_DECRYPT(des_key_schedule ks1,
1.16 markus 57: des_key_schedule ks2, des_cblock * iv2,
58: des_key_schedule ks3, des_cblock * iv3,
1.19 markus 59: unsigned char *dest, unsigned char *src,
1.1 deraadt 60: unsigned int len)
61: {
1.16 markus 62: des_cblock iv1;
1.1 deraadt 63:
1.16 markus 64: memcpy(&iv1, iv2, 8);
1.1 deraadt 65:
1.16 markus 66: des_cbc_encrypt(src, dest, len, ks3, iv3, DES_DECRYPT);
67: memcpy(iv3, src + len - 8, 8);
1.1 deraadt 68:
1.16 markus 69: des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_ENCRYPT);
70: memcpy(iv2, dest + len - 8, 8);
1.1 deraadt 71:
1.16 markus 72: des_cbc_encrypt(dest, dest, len, ks1, &iv1, DES_DECRYPT);
73: /* memcpy(&iv1, iv2, 8); */
74: /* Note how iv1 == iv2 on entry and exit. */
1.1 deraadt 75: }
76:
77: /*
78: * SSH uses a variation on Blowfish, all bytes must be swapped before
79: * and after encryption/decryption. Thus the swap_bytes stuff (yuk).
80: */
1.16 markus 81: static void
1.1 deraadt 82: swap_bytes(const unsigned char *src, unsigned char *dst_, int n)
83: {
1.16 markus 84: /* dst must be properly aligned. */
85: u_int32_t *dst = (u_int32_t *) dst_;
86: union {
87: u_int32_t i;
88: char c[4];
89: } t;
90:
91: /* Process 8 bytes every lap. */
92: for (n = n / 8; n > 0; n--) {
93: t.c[3] = *src++;
94: t.c[2] = *src++;
95: t.c[1] = *src++;
96: t.c[0] = *src++;
97: *dst++ = t.i;
98:
99: t.c[3] = *src++;
100: t.c[2] = *src++;
101: t.c[1] = *src++;
102: t.c[0] = *src++;
103: *dst++ = t.i;
104: }
1.1 deraadt 105: }
106:
1.18 markus 107: /*
108: * Names of all encryption algorithms.
109: * These must match the numbers defined in cipher.h.
110: */
1.1 deraadt 111: static char *cipher_names[] =
1.4 provos 112: {
1.16 markus 113: "none",
114: "idea",
115: "des",
116: "3des",
117: "tss",
118: "rc4",
1.21 ! markus 119: "blowfish",
! 120: "reserved",
! 121: "blowfish-cbc",
! 122: "3des-cbc",
! 123: "arcfour",
! 124: "cast128-cbc"
1.1 deraadt 125: };
126:
1.18 markus 127: /*
128: * Returns a bit mask indicating which ciphers are supported by this
129: * implementation. The bit mask has the corresponding bit set of each
130: * supported cipher.
131: */
1.1 deraadt 132:
1.16 markus 133: unsigned int
134: cipher_mask()
1.1 deraadt 135: {
1.16 markus 136: unsigned int mask = 0;
137: mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */
138: mask |= 1 << SSH_CIPHER_BLOWFISH;
1.21 ! markus 139: mask |= 1 << SSH_CIPHER_BLOWFISH_CBC;
! 140: mask |= 1 << SSH_CIPHER_3DES_CBC;
! 141: mask |= 1 << SSH_CIPHER_ARCFOUR;
! 142: mask |= 1 << SSH_CIPHER_CAST128_CBC;
1.16 markus 143: return mask;
1.1 deraadt 144: }
145:
146: /* Returns the name of the cipher. */
147:
1.16 markus 148: const char *
149: cipher_name(int cipher)
1.1 deraadt 150: {
1.16 markus 151: if (cipher < 0 || cipher >= sizeof(cipher_names) / sizeof(cipher_names[0]) ||
152: cipher_names[cipher] == NULL)
153: fatal("cipher_name: bad cipher number: %d", cipher);
154: return cipher_names[cipher];
1.1 deraadt 155: }
156:
1.18 markus 157: /*
158: * Parses the name of the cipher. Returns the number of the corresponding
159: * cipher, or -1 on error.
160: */
1.1 deraadt 161:
1.4 provos 162: int
163: cipher_number(const char *name)
1.1 deraadt 164: {
1.16 markus 165: int i;
166: for (i = 0; i < sizeof(cipher_names) / sizeof(cipher_names[0]); i++)
167: if (strcmp(cipher_names[i], name) == 0 &&
168: (cipher_mask() & (1 << i)))
169: return i;
170: return -1;
1.1 deraadt 171: }
172:
1.18 markus 173: /*
174: * Selects the cipher, and keys if by computing the MD5 checksum of the
175: * passphrase and using the resulting 16 bytes as the key.
176: */
1.1 deraadt 177:
1.16 markus 178: void
179: cipher_set_key_string(CipherContext *context, int cipher,
180: const char *passphrase, int for_encryption)
1.1 deraadt 181: {
1.16 markus 182: MD5_CTX md;
183: unsigned char digest[16];
184:
185: MD5_Init(&md);
186: MD5_Update(&md, (const unsigned char *) passphrase, strlen(passphrase));
187: MD5_Final(digest, &md);
188:
189: cipher_set_key(context, cipher, digest, 16, for_encryption);
190:
191: memset(digest, 0, sizeof(digest));
192: memset(&md, 0, sizeof(md));
1.1 deraadt 193: }
194:
195: /* Selects the cipher to use and sets the key. */
196:
1.16 markus 197: void
198: cipher_set_key(CipherContext *context, int cipher,
199: const unsigned char *key, int keylen, int for_encryption)
200: {
201: unsigned char padded[32];
202:
203: /* Set cipher type. */
204: context->type = cipher;
205:
206: /* Get 32 bytes of key data. Pad if necessary. (So that code
207: below does not need to worry about key size). */
208: memset(padded, 0, sizeof(padded));
209: memcpy(padded, key, keylen < sizeof(padded) ? keylen : sizeof(padded));
210:
211: /* Initialize the initialization vector. */
212: switch (cipher) {
213: case SSH_CIPHER_NONE:
1.18 markus 214: /*
215: * Has to stay for authfile saving of private key with no
216: * passphrase
217: */
1.16 markus 218: break;
219:
220: case SSH_CIPHER_3DES:
1.18 markus 221: /*
222: * Note: the least significant bit of each byte of key is
223: * parity, and must be ignored by the implementation. 16
224: * bytes of key are used (first and last keys are the same).
225: */
1.16 markus 226: if (keylen < 16)
227: error("Key length %d is insufficient for 3DES.", keylen);
228: des_set_key((void *) padded, context->u.des3.key1);
229: des_set_key((void *) (padded + 8), context->u.des3.key2);
230: if (keylen <= 16)
231: des_set_key((void *) padded, context->u.des3.key3);
232: else
233: des_set_key((void *) (padded + 16), context->u.des3.key3);
234: memset(context->u.des3.iv2, 0, sizeof(context->u.des3.iv2));
235: memset(context->u.des3.iv3, 0, sizeof(context->u.des3.iv3));
236: break;
237:
238: case SSH_CIPHER_BLOWFISH:
1.21 ! markus 239: if (keylen < 16)
! 240: error("Key length %d is insufficient for blowfish.", keylen);
1.16 markus 241: BF_set_key(&context->u.bf.key, keylen, padded);
242: memset(context->u.bf.iv, 0, 8);
243: break;
244:
1.21 ! markus 245: case SSH_CIPHER_3DES_CBC:
! 246: case SSH_CIPHER_BLOWFISH_CBC:
! 247: case SSH_CIPHER_ARCFOUR:
! 248: case SSH_CIPHER_CAST128_CBC:
! 249: fatal("cipher_set_key: illegal cipher: %s", cipher_name(cipher));
! 250: break;
! 251:
1.16 markus 252: default:
253: fatal("cipher_set_key: unknown cipher: %s", cipher_name(cipher));
254: }
255: memset(padded, 0, sizeof(padded));
1.1 deraadt 256: }
257:
1.21 ! markus 258:
! 259: void
! 260: cipher_set_key_iv(CipherContext * context, int cipher,
! 261: const unsigned char *key, int keylen,
! 262: const unsigned char *iv, int ivlen)
! 263: {
! 264: /* Set cipher type. */
! 265: context->type = cipher;
! 266:
! 267: /* Initialize the initialization vector. */
! 268: switch (cipher) {
! 269: case SSH_CIPHER_NONE:
! 270: break;
! 271:
! 272: case SSH_CIPHER_3DES:
! 273: case SSH_CIPHER_BLOWFISH:
! 274: fatal("cipher_set_key_iv: illegal cipher: %s", cipher_name(cipher));
! 275: break;
! 276:
! 277: case SSH_CIPHER_3DES_CBC:
! 278: if (keylen < 24)
! 279: error("Key length %d is insufficient for 3des-cbc.", keylen);
! 280: des_set_key((void *) key, context->u.des3.key1);
! 281: des_set_key((void *) (key+8), context->u.des3.key2);
! 282: des_set_key((void *) (key+16), context->u.des3.key3);
! 283: if (ivlen < 8)
! 284: error("IV length %d is insufficient for 3des-cbc.", ivlen);
! 285: memcpy(context->u.des3.iv3, (char *)iv, 8);
! 286: break;
! 287:
! 288: case SSH_CIPHER_BLOWFISH_CBC:
! 289: if (keylen < 16)
! 290: error("Key length %d is insufficient for blowfish.", keylen);
! 291: if (ivlen < 8)
! 292: error("IV length %d is insufficient for blowfish.", ivlen);
! 293: BF_set_key(&context->u.bf.key, keylen, (unsigned char *)key);
! 294: memcpy(context->u.bf.iv, (char *)iv, 8);
! 295: break;
! 296:
! 297: case SSH_CIPHER_ARCFOUR:
! 298: if (keylen < 16)
! 299: error("Key length %d is insufficient for arcfour.", keylen);
! 300: RC4_set_key(&context->u.rc4, keylen, (unsigned char *)key);
! 301: break;
! 302:
! 303: case SSH_CIPHER_CAST128_CBC:
! 304: if (keylen < 16)
! 305: error("Key length %d is insufficient for cast128.", keylen);
! 306: if (ivlen < 8)
! 307: error("IV length %d is insufficient for cast128.", ivlen);
! 308: CAST_set_key(&context->u.cast.key, keylen, (unsigned char *) key);
! 309: memcpy(context->u.cast.iv, (char *)iv, 8);
! 310: break;
! 311:
! 312: default:
! 313: fatal("cipher_set_key: unknown cipher: %s", cipher_name(cipher));
! 314: }
! 315: }
! 316:
1.1 deraadt 317: /* Encrypts data using the cipher. */
318:
1.16 markus 319: void
320: cipher_encrypt(CipherContext *context, unsigned char *dest,
321: const unsigned char *src, unsigned int len)
322: {
323: if ((len & 7) != 0)
324: fatal("cipher_encrypt: bad plaintext length %d", len);
325:
326: switch (context->type) {
327: case SSH_CIPHER_NONE:
328: memcpy(dest, src, len);
329: break;
330:
331: case SSH_CIPHER_3DES:
332: SSH_3CBC_ENCRYPT(context->u.des3.key1,
333: context->u.des3.key2, &context->u.des3.iv2,
334: context->u.des3.key3, &context->u.des3.iv3,
1.19 markus 335: dest, (unsigned char *) src, len);
1.16 markus 336: break;
337:
338: case SSH_CIPHER_BLOWFISH:
339: swap_bytes(src, dest, len);
340: BF_cbc_encrypt(dest, dest, len,
341: &context->u.bf.key, context->u.bf.iv,
342: BF_ENCRYPT);
343: swap_bytes(dest, dest, len);
344: break;
345:
1.21 ! markus 346: case SSH_CIPHER_BLOWFISH_CBC:
! 347: BF_cbc_encrypt((void *)src, dest, len,
! 348: &context->u.bf.key, context->u.bf.iv,
! 349: BF_ENCRYPT);
! 350: break;
! 351:
! 352: case SSH_CIPHER_3DES_CBC:
! 353: des_ede3_cbc_encrypt(src, dest, len,
! 354: context->u.des3.key1, context->u.des3.key2,
! 355: context->u.des3.key3, &context->u.des3.iv3, DES_ENCRYPT);
! 356: break;
! 357:
! 358: case SSH_CIPHER_ARCFOUR:
! 359: RC4(&context->u.rc4, len, (unsigned char *)src, dest);
! 360: break;
! 361:
! 362: case SSH_CIPHER_CAST128_CBC:
! 363: CAST_cbc_encrypt(src, dest, len,
! 364: &context->u.cast.key, context->u.cast.iv, CAST_ENCRYPT);
! 365: break;
! 366:
1.16 markus 367: default:
368: fatal("cipher_encrypt: unknown cipher: %s", cipher_name(context->type));
369: }
370: }
1.1 deraadt 371:
372: /* Decrypts data using the cipher. */
373:
1.16 markus 374: void
375: cipher_decrypt(CipherContext *context, unsigned char *dest,
376: const unsigned char *src, unsigned int len)
377: {
378: if ((len & 7) != 0)
379: fatal("cipher_decrypt: bad ciphertext length %d", len);
380:
381: switch (context->type) {
382: case SSH_CIPHER_NONE:
383: memcpy(dest, src, len);
384: break;
385:
386: case SSH_CIPHER_3DES:
387: SSH_3CBC_DECRYPT(context->u.des3.key1,
388: context->u.des3.key2, &context->u.des3.iv2,
389: context->u.des3.key3, &context->u.des3.iv3,
1.19 markus 390: dest, (unsigned char *) src, len);
1.16 markus 391: break;
392:
393: case SSH_CIPHER_BLOWFISH:
394: swap_bytes(src, dest, len);
395: BF_cbc_encrypt((void *) dest, dest, len,
396: &context->u.bf.key, context->u.bf.iv,
397: BF_DECRYPT);
398: swap_bytes(dest, dest, len);
1.21 ! markus 399: break;
! 400:
! 401: case SSH_CIPHER_BLOWFISH_CBC:
! 402: BF_cbc_encrypt((void *) src, dest, len,
! 403: &context->u.bf.key, context->u.bf.iv,
! 404: BF_DECRYPT);
! 405: break;
! 406:
! 407: case SSH_CIPHER_3DES_CBC:
! 408: des_ede3_cbc_encrypt(src, dest, len,
! 409: context->u.des3.key1, context->u.des3.key2,
! 410: context->u.des3.key3, &context->u.des3.iv3, DES_DECRYPT);
! 411: break;
! 412:
! 413: case SSH_CIPHER_ARCFOUR:
! 414: RC4(&context->u.rc4, len, (unsigned char *)src, dest);
! 415: break;
! 416:
! 417: case SSH_CIPHER_CAST128_CBC:
! 418: CAST_cbc_encrypt(src, dest, len,
! 419: &context->u.cast.key, context->u.cast.iv, CAST_DECRYPT);
1.16 markus 420: break;
421:
422: default:
423: fatal("cipher_decrypt: unknown cipher: %s", cipher_name(context->type));
424: }
1.1 deraadt 425: }
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