Annotation of src/usr.bin/ssh/cipher.c, Revision 1.16
1.1 deraadt 1: /*
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: */
13:
14: #include "includes.h"
1.16 ! markus 15: RCSID("$Id: cipher.c,v 1.15 1999/11/22 21:02:38 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,
1.1 deraadt 38: void *dest, void *src,
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,
1.1 deraadt 59: void *dest, void *src,
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:
1.16 ! markus 107: void (*cipher_attack_detected) (const char *fmt,...) = fatal;
1.1 deraadt 108:
1.16 ! markus 109: static inline void
1.1 deraadt 110: detect_cbc_attack(const unsigned char *src,
111: unsigned int len)
112: {
1.16 ! markus 113: return;
! 114:
! 115: log("CRC-32 CBC insertion attack detected");
! 116: cipher_attack_detected("CRC-32 CBC insertion attack detected");
1.1 deraadt 117: }
118:
119: /* Names of all encryption algorithms. These must match the numbers defined
120: int cipher.h. */
121: static char *cipher_names[] =
1.4 provos 122: {
1.16 ! markus 123: "none",
! 124: "idea",
! 125: "des",
! 126: "3des",
! 127: "tss",
! 128: "rc4",
! 129: "blowfish"
1.1 deraadt 130: };
131:
132: /* Returns a bit mask indicating which ciphers are supported by this
133: implementation. The bit mask has the corresponding bit set of each
134: supported cipher. */
135:
1.16 ! markus 136: unsigned int
! 137: cipher_mask()
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;
! 142: return mask;
1.1 deraadt 143: }
144:
145: /* Returns the name of the cipher. */
146:
1.16 ! markus 147: const char *
! 148: cipher_name(int cipher)
1.1 deraadt 149: {
1.16 ! markus 150: if (cipher < 0 || cipher >= sizeof(cipher_names) / sizeof(cipher_names[0]) ||
! 151: cipher_names[cipher] == NULL)
! 152: fatal("cipher_name: bad cipher number: %d", cipher);
! 153: return cipher_names[cipher];
1.1 deraadt 154: }
155:
156: /* Parses the name of the cipher. Returns the number of the corresponding
157: cipher, or -1 on error. */
158:
1.4 provos 159: int
160: cipher_number(const char *name)
1.1 deraadt 161: {
1.16 ! markus 162: int i;
! 163: for (i = 0; i < sizeof(cipher_names) / sizeof(cipher_names[0]); i++)
! 164: if (strcmp(cipher_names[i], name) == 0 &&
! 165: (cipher_mask() & (1 << i)))
! 166: return i;
! 167: return -1;
1.1 deraadt 168: }
169:
170: /* Selects the cipher, and keys if by computing the MD5 checksum of the
171: passphrase and using the resulting 16 bytes as the key. */
172:
1.16 ! markus 173: void
! 174: cipher_set_key_string(CipherContext *context, int cipher,
! 175: const char *passphrase, int for_encryption)
1.1 deraadt 176: {
1.16 ! markus 177: MD5_CTX md;
! 178: unsigned char digest[16];
! 179:
! 180: MD5_Init(&md);
! 181: MD5_Update(&md, (const unsigned char *) passphrase, strlen(passphrase));
! 182: MD5_Final(digest, &md);
! 183:
! 184: cipher_set_key(context, cipher, digest, 16, for_encryption);
! 185:
! 186: memset(digest, 0, sizeof(digest));
! 187: memset(&md, 0, sizeof(md));
1.1 deraadt 188: }
189:
190: /* Selects the cipher to use and sets the key. */
191:
1.16 ! markus 192: void
! 193: cipher_set_key(CipherContext *context, int cipher,
! 194: const unsigned char *key, int keylen, int for_encryption)
! 195: {
! 196: unsigned char padded[32];
! 197:
! 198: /* Set cipher type. */
! 199: context->type = cipher;
! 200:
! 201: /* Get 32 bytes of key data. Pad if necessary. (So that code
! 202: below does not need to worry about key size). */
! 203: memset(padded, 0, sizeof(padded));
! 204: memcpy(padded, key, keylen < sizeof(padded) ? keylen : sizeof(padded));
! 205:
! 206: /* Initialize the initialization vector. */
! 207: switch (cipher) {
! 208: case SSH_CIPHER_NONE:
! 209: /* Has to stay for authfile saving of private key with
! 210: no passphrase */
! 211: break;
! 212:
! 213: case SSH_CIPHER_3DES:
! 214: /* Note: the least significant bit of each byte of key is
! 215: parity, and must be ignored by the implementation. 16
! 216: bytes of key are used (first and last keys are the
! 217: same). */
! 218: if (keylen < 16)
! 219: error("Key length %d is insufficient for 3DES.", keylen);
! 220: des_set_key((void *) padded, context->u.des3.key1);
! 221: des_set_key((void *) (padded + 8), context->u.des3.key2);
! 222: if (keylen <= 16)
! 223: des_set_key((void *) padded, context->u.des3.key3);
! 224: else
! 225: des_set_key((void *) (padded + 16), context->u.des3.key3);
! 226: memset(context->u.des3.iv2, 0, sizeof(context->u.des3.iv2));
! 227: memset(context->u.des3.iv3, 0, sizeof(context->u.des3.iv3));
! 228: break;
! 229:
! 230: case SSH_CIPHER_BLOWFISH:
! 231: BF_set_key(&context->u.bf.key, keylen, padded);
! 232: memset(context->u.bf.iv, 0, 8);
! 233: break;
! 234:
! 235: default:
! 236: fatal("cipher_set_key: unknown cipher: %s", cipher_name(cipher));
! 237: }
! 238: memset(padded, 0, sizeof(padded));
1.1 deraadt 239: }
240:
241: /* Encrypts data using the cipher. */
242:
1.16 ! markus 243: void
! 244: cipher_encrypt(CipherContext *context, unsigned char *dest,
! 245: const unsigned char *src, unsigned int len)
! 246: {
! 247: if ((len & 7) != 0)
! 248: fatal("cipher_encrypt: bad plaintext length %d", len);
! 249:
! 250: switch (context->type) {
! 251: case SSH_CIPHER_NONE:
! 252: memcpy(dest, src, len);
! 253: break;
! 254:
! 255: case SSH_CIPHER_3DES:
! 256: SSH_3CBC_ENCRYPT(context->u.des3.key1,
! 257: context->u.des3.key2, &context->u.des3.iv2,
! 258: context->u.des3.key3, &context->u.des3.iv3,
! 259: dest, (void *) src, len);
! 260: break;
! 261:
! 262: case SSH_CIPHER_BLOWFISH:
! 263: swap_bytes(src, dest, len);
! 264: BF_cbc_encrypt(dest, dest, len,
! 265: &context->u.bf.key, context->u.bf.iv,
! 266: BF_ENCRYPT);
! 267: swap_bytes(dest, dest, len);
! 268: break;
! 269:
! 270: default:
! 271: fatal("cipher_encrypt: unknown cipher: %s", cipher_name(context->type));
! 272: }
! 273: }
1.1 deraadt 274:
275: /* Decrypts data using the cipher. */
276:
1.16 ! markus 277: void
! 278: cipher_decrypt(CipherContext *context, unsigned char *dest,
! 279: const unsigned char *src, unsigned int len)
! 280: {
! 281: if ((len & 7) != 0)
! 282: fatal("cipher_decrypt: bad ciphertext length %d", len);
! 283:
! 284: switch (context->type) {
! 285: case SSH_CIPHER_NONE:
! 286: memcpy(dest, src, len);
! 287: break;
! 288:
! 289: case SSH_CIPHER_3DES:
! 290: /* CRC-32 attack? */
! 291: SSH_3CBC_DECRYPT(context->u.des3.key1,
! 292: context->u.des3.key2, &context->u.des3.iv2,
! 293: context->u.des3.key3, &context->u.des3.iv3,
! 294: dest, (void *) src, len);
! 295: break;
! 296:
! 297: case SSH_CIPHER_BLOWFISH:
! 298: detect_cbc_attack(src, len);
! 299: swap_bytes(src, dest, len);
! 300: BF_cbc_encrypt((void *) dest, dest, len,
! 301: &context->u.bf.key, context->u.bf.iv,
! 302: BF_DECRYPT);
! 303: swap_bytes(dest, dest, len);
! 304: break;
! 305:
! 306: default:
! 307: fatal("cipher_decrypt: unknown cipher: %s", cipher_name(context->type));
! 308: }
1.1 deraadt 309: }
![[BACK]](/icons/back.gif){kind=icon}
Return to cipher.c CVS log ![[TXT]](/icons/text.gif){kind=icon}
![[DIR]](/icons/dir.gif){kind=icon}
Up to [local] / src / usr.bin / ssh