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Damien Millerd4a8b7e1999-10-27 13:42:43 +10001/*
Damien Miller95def091999-11-25 00:26:21 +11002 *
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 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +100013
14#include "includes.h"
Damien Miller3b9d5e91999-12-15 09:34:31 +110015RCSID("$Id: cipher.c,v 1.11 1999/12/14 22:34:31 damien Exp $");
Damien Millerd4a8b7e1999-10-27 13:42:43 +100016
17#include "ssh.h"
18#include "cipher.h"
19
Damien Miller7f6ea021999-10-28 13:25:17 +100020#ifdef HAVE_OPENSSL
Damien Millerd4a8b7e1999-10-27 13:42:43 +100021#include <openssl/md5.h>
Damien Miller7f6ea021999-10-28 13:25:17 +100022#endif
23#ifdef HAVE_SSL
24#include <ssl/md5.h>
25#endif
Damien Millerd4a8b7e1999-10-27 13:42:43 +100026
27/*
28 * What kind of tripple DES are these 2 routines?
29 *
30 * Why is there a redundant initialization vector?
31 *
32 * If only iv3 was used, then, this would till effect have been
33 * outer-cbc. However, there is also a private iv1 == iv2 which
34 * perhaps makes differential analysis easier. On the other hand, the
35 * private iv1 probably makes the CRC-32 attack ineffective. This is a
36 * result of that there is no longer any known iv1 to use when
37 * choosing the X block.
38 */
39void
40SSH_3CBC_ENCRYPT(des_key_schedule ks1,
Damien Miller95def091999-11-25 00:26:21 +110041 des_key_schedule ks2, des_cblock * iv2,
42 des_key_schedule ks3, des_cblock * iv3,
Damien Millerd4a8b7e1999-10-27 13:42:43 +100043 void *dest, void *src,
44 unsigned int len)
45{
Damien Miller95def091999-11-25 00:26:21 +110046 des_cblock iv1;
Damien Millerd4a8b7e1999-10-27 13:42:43 +100047
Damien Miller95def091999-11-25 00:26:21 +110048 memcpy(&iv1, iv2, 8);
Damien Millerd4a8b7e1999-10-27 13:42:43 +100049
Damien Miller95def091999-11-25 00:26:21 +110050 des_cbc_encrypt(src, dest, len, ks1, &iv1, DES_ENCRYPT);
Damien Miller84093e91999-12-15 09:06:28 +110051 memcpy(&iv1, (char *)dest + len - 8, 8);
Damien Millerd4a8b7e1999-10-27 13:42:43 +100052
Damien Miller95def091999-11-25 00:26:21 +110053 des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_DECRYPT);
54 memcpy(iv2, &iv1, 8); /* Note how iv1 == iv2 on entry and exit. */
Damien Millerd4a8b7e1999-10-27 13:42:43 +100055
Damien Miller95def091999-11-25 00:26:21 +110056 des_cbc_encrypt(dest, dest, len, ks3, iv3, DES_ENCRYPT);
Damien Miller84093e91999-12-15 09:06:28 +110057 memcpy(iv3, (char *)dest + len - 8, 8);
Damien Millerd4a8b7e1999-10-27 13:42:43 +100058}
59
60void
61SSH_3CBC_DECRYPT(des_key_schedule ks1,
Damien Miller95def091999-11-25 00:26:21 +110062 des_key_schedule ks2, des_cblock * iv2,
63 des_key_schedule ks3, des_cblock * iv3,
Damien Millerd4a8b7e1999-10-27 13:42:43 +100064 void *dest, void *src,
65 unsigned int len)
66{
Damien Miller95def091999-11-25 00:26:21 +110067 des_cblock iv1;
Damien Millerd4a8b7e1999-10-27 13:42:43 +100068
Damien Miller95def091999-11-25 00:26:21 +110069 memcpy(&iv1, iv2, 8);
Damien Millerd4a8b7e1999-10-27 13:42:43 +100070
Damien Miller95def091999-11-25 00:26:21 +110071 des_cbc_encrypt(src, dest, len, ks3, iv3, DES_DECRYPT);
Damien Miller84093e91999-12-15 09:06:28 +110072 memcpy(iv3, (char *)src + len - 8, 8);
Damien Millerd4a8b7e1999-10-27 13:42:43 +100073
Damien Miller95def091999-11-25 00:26:21 +110074 des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_ENCRYPT);
Damien Miller84093e91999-12-15 09:06:28 +110075 memcpy(iv2, (char *)dest + len - 8, 8);
Damien Millerd4a8b7e1999-10-27 13:42:43 +100076
Damien Miller95def091999-11-25 00:26:21 +110077 des_cbc_encrypt(dest, dest, len, ks1, &iv1, DES_DECRYPT);
78 /* memcpy(&iv1, iv2, 8); */
79 /* Note how iv1 == iv2 on entry and exit. */
Damien Millerd4a8b7e1999-10-27 13:42:43 +100080}
81
82/*
83 * SSH uses a variation on Blowfish, all bytes must be swapped before
84 * and after encryption/decryption. Thus the swap_bytes stuff (yuk).
85 */
Damien Miller95def091999-11-25 00:26:21 +110086static void
Damien Millerd4a8b7e1999-10-27 13:42:43 +100087swap_bytes(const unsigned char *src, unsigned char *dst_, int n)
88{
Damien Miller95def091999-11-25 00:26:21 +110089 /* dst must be properly aligned. */
90 u_int32_t *dst = (u_int32_t *) dst_;
91 union {
92 u_int32_t i;
93 char c[4];
94 } t;
Damien Millerd4a8b7e1999-10-27 13:42:43 +100095
Damien Miller95def091999-11-25 00:26:21 +110096 /* Process 8 bytes every lap. */
97 for (n = n / 8; n > 0; n--) {
98 t.c[3] = *src++;
99 t.c[2] = *src++;
100 t.c[1] = *src++;
101 t.c[0] = *src++;
102 *dst++ = t.i;
103
104 t.c[3] = *src++;
105 t.c[2] = *src++;
106 t.c[1] = *src++;
107 t.c[0] = *src++;
108 *dst++ = t.i;
109 }
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000110}
111
Damien Miller95def091999-11-25 00:26:21 +1100112void (*cipher_attack_detected) (const char *fmt,...) = fatal;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000113
Damien Miller3b9d5e91999-12-15 09:34:31 +1100114static inline void
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000115detect_cbc_attack(const unsigned char *src,
116 unsigned int len)
117{
Damien Miller95def091999-11-25 00:26:21 +1100118 return;
119
120 log("CRC-32 CBC insertion attack detected");
121 cipher_attack_detected("CRC-32 CBC insertion attack detected");
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000122}
123
Damien Miller5428f641999-11-25 11:54:57 +1100124/*
125 * Names of all encryption algorithms.
126 * These must match the numbers defined in cipher.h.
127 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000128static char *cipher_names[] =
129{
Damien Miller95def091999-11-25 00:26:21 +1100130 "none",
131 "idea",
132 "des",
133 "3des",
134 "tss",
135 "rc4",
136 "blowfish"
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000137};
138
Damien Miller5428f641999-11-25 11:54:57 +1100139/*
140 * Returns a bit mask indicating which ciphers are supported by this
141 * implementation. The bit mask has the corresponding bit set of each
142 * supported cipher.
143 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000144
Damien Miller95def091999-11-25 00:26:21 +1100145unsigned int
146cipher_mask()
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000147{
Damien Miller95def091999-11-25 00:26:21 +1100148 unsigned int mask = 0;
149 mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */
150 mask |= 1 << SSH_CIPHER_BLOWFISH;
151 return mask;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000152}
153
154/* Returns the name of the cipher. */
155
Damien Miller95def091999-11-25 00:26:21 +1100156const char *
157cipher_name(int cipher)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000158{
Damien Miller95def091999-11-25 00:26:21 +1100159 if (cipher < 0 || cipher >= sizeof(cipher_names) / sizeof(cipher_names[0]) ||
160 cipher_names[cipher] == NULL)
161 fatal("cipher_name: bad cipher number: %d", cipher);
162 return cipher_names[cipher];
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000163}
164
Damien Miller5428f641999-11-25 11:54:57 +1100165/*
166 * Parses the name of the cipher. Returns the number of the corresponding
167 * cipher, or -1 on error.
168 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000169
170int
171cipher_number(const char *name)
172{
Damien Miller95def091999-11-25 00:26:21 +1100173 int i;
174 for (i = 0; i < sizeof(cipher_names) / sizeof(cipher_names[0]); i++)
175 if (strcmp(cipher_names[i], name) == 0 &&
176 (cipher_mask() & (1 << i)))
177 return i;
178 return -1;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000179}
180
Damien Miller5428f641999-11-25 11:54:57 +1100181/*
182 * Selects the cipher, and keys if by computing the MD5 checksum of the
183 * passphrase and using the resulting 16 bytes as the key.
184 */
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000185
Damien Miller95def091999-11-25 00:26:21 +1100186void
187cipher_set_key_string(CipherContext *context, int cipher,
188 const char *passphrase, int for_encryption)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000189{
Damien Miller95def091999-11-25 00:26:21 +1100190 MD5_CTX md;
191 unsigned char digest[16];
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000192
Damien Miller95def091999-11-25 00:26:21 +1100193 MD5_Init(&md);
194 MD5_Update(&md, (const unsigned char *) passphrase, strlen(passphrase));
195 MD5_Final(digest, &md);
196
197 cipher_set_key(context, cipher, digest, 16, for_encryption);
198
199 memset(digest, 0, sizeof(digest));
200 memset(&md, 0, sizeof(md));
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000201}
202
203/* Selects the cipher to use and sets the key. */
204
Damien Miller95def091999-11-25 00:26:21 +1100205void
206cipher_set_key(CipherContext *context, int cipher,
207 const unsigned char *key, int keylen, int for_encryption)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000208{
Damien Miller95def091999-11-25 00:26:21 +1100209 unsigned char padded[32];
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000210
Damien Miller95def091999-11-25 00:26:21 +1100211 /* Set cipher type. */
212 context->type = cipher;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000213
Damien Miller95def091999-11-25 00:26:21 +1100214 /* Get 32 bytes of key data. Pad if necessary. (So that code
215 below does not need to worry about key size). */
216 memset(padded, 0, sizeof(padded));
217 memcpy(padded, key, keylen < sizeof(padded) ? keylen : sizeof(padded));
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000218
Damien Miller95def091999-11-25 00:26:21 +1100219 /* Initialize the initialization vector. */
220 switch (cipher) {
221 case SSH_CIPHER_NONE:
Damien Miller5428f641999-11-25 11:54:57 +1100222 /*
223 * Has to stay for authfile saving of private key with no
224 * passphrase
225 */
Damien Miller95def091999-11-25 00:26:21 +1100226 break;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000227
Damien Miller95def091999-11-25 00:26:21 +1100228 case SSH_CIPHER_3DES:
Damien Miller5428f641999-11-25 11:54:57 +1100229 /*
230 * Note: the least significant bit of each byte of key is
231 * parity, and must be ignored by the implementation. 16
232 * bytes of key are used (first and last keys are the same).
233 */
Damien Miller95def091999-11-25 00:26:21 +1100234 if (keylen < 16)
235 error("Key length %d is insufficient for 3DES.", keylen);
236 des_set_key((void *) padded, context->u.des3.key1);
237 des_set_key((void *) (padded + 8), context->u.des3.key2);
238 if (keylen <= 16)
239 des_set_key((void *) padded, context->u.des3.key3);
240 else
241 des_set_key((void *) (padded + 16), context->u.des3.key3);
242 memset(context->u.des3.iv2, 0, sizeof(context->u.des3.iv2));
243 memset(context->u.des3.iv3, 0, sizeof(context->u.des3.iv3));
244 break;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000245
Damien Miller95def091999-11-25 00:26:21 +1100246 case SSH_CIPHER_BLOWFISH:
247 BF_set_key(&context->u.bf.key, keylen, padded);
248 memset(context->u.bf.iv, 0, 8);
249 break;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000250
Damien Miller95def091999-11-25 00:26:21 +1100251 default:
252 fatal("cipher_set_key: unknown cipher: %s", cipher_name(cipher));
253 }
254 memset(padded, 0, sizeof(padded));
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000255}
256
257/* Encrypts data using the cipher. */
258
Damien Miller95def091999-11-25 00:26:21 +1100259void
260cipher_encrypt(CipherContext *context, unsigned char *dest,
261 const unsigned char *src, unsigned int len)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000262{
Damien Miller95def091999-11-25 00:26:21 +1100263 if ((len & 7) != 0)
264 fatal("cipher_encrypt: bad plaintext length %d", len);
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000265
Damien Miller95def091999-11-25 00:26:21 +1100266 switch (context->type) {
267 case SSH_CIPHER_NONE:
268 memcpy(dest, src, len);
269 break;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000270
Damien Miller95def091999-11-25 00:26:21 +1100271 case SSH_CIPHER_3DES:
272 SSH_3CBC_ENCRYPT(context->u.des3.key1,
273 context->u.des3.key2, &context->u.des3.iv2,
274 context->u.des3.key3, &context->u.des3.iv3,
275 dest, (void *) src, len);
276 break;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000277
Damien Miller95def091999-11-25 00:26:21 +1100278 case SSH_CIPHER_BLOWFISH:
279 swap_bytes(src, dest, len);
280 BF_cbc_encrypt(dest, dest, len,
281 &context->u.bf.key, context->u.bf.iv,
282 BF_ENCRYPT);
283 swap_bytes(dest, dest, len);
284 break;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000285
Damien Miller95def091999-11-25 00:26:21 +1100286 default:
287 fatal("cipher_encrypt: unknown cipher: %s", cipher_name(context->type));
288 }
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000289}
Damien Miller95def091999-11-25 00:26:21 +1100290
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000291/* Decrypts data using the cipher. */
292
Damien Miller95def091999-11-25 00:26:21 +1100293void
294cipher_decrypt(CipherContext *context, unsigned char *dest,
295 const unsigned char *src, unsigned int len)
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000296{
Damien Miller95def091999-11-25 00:26:21 +1100297 if ((len & 7) != 0)
298 fatal("cipher_decrypt: bad ciphertext length %d", len);
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000299
Damien Miller95def091999-11-25 00:26:21 +1100300 switch (context->type) {
301 case SSH_CIPHER_NONE:
302 memcpy(dest, src, len);
303 break;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000304
Damien Miller95def091999-11-25 00:26:21 +1100305 case SSH_CIPHER_3DES:
306 /* CRC-32 attack? */
307 SSH_3CBC_DECRYPT(context->u.des3.key1,
308 context->u.des3.key2, &context->u.des3.iv2,
309 context->u.des3.key3, &context->u.des3.iv3,
310 dest, (void *) src, len);
311 break;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000312
Damien Miller95def091999-11-25 00:26:21 +1100313 case SSH_CIPHER_BLOWFISH:
314 detect_cbc_attack(src, len);
315 swap_bytes(src, dest, len);
316 BF_cbc_encrypt((void *) dest, dest, len,
317 &context->u.bf.key, context->u.bf.iv,
318 BF_DECRYPT);
319 swap_bytes(dest, dest, len);
320 break;
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000321
Damien Miller95def091999-11-25 00:26:21 +1100322 default:
323 fatal("cipher_decrypt: unknown cipher: %s", cipher_name(context->type));
324 }
Damien Millerd4a8b7e1999-10-27 13:42:43 +1000325}