5 Author: Tatu Ylonen <ylo@cs.hut.fi>
7 Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
10 Created: Wed Apr 19 17:41:39 1995 ylo
22 #include <openssl/md5.h>
29 * What kind of tripple DES are these 2 routines?
31 * Why is there a redundant initialization vector?
33 * If only iv3 was used, then, this would till effect have been
34 * outer-cbc. However, there is also a private iv1 == iv2 which
35 * perhaps makes differential analysis easier. On the other hand, the
36 * private iv1 probably makes the CRC-32 attack ineffective. This is a
37 * result of that there is no longer any known iv1 to use when
38 * choosing the X block.
41 SSH_3CBC_ENCRYPT(des_key_schedule ks1,
42 des_key_schedule ks2, des_cblock *iv2,
43 des_key_schedule ks3, des_cblock *iv3,
44 void *dest, void *src,
51 des_cbc_encrypt(src, dest, len, ks1, &iv1, DES_ENCRYPT);
52 memcpy(&iv1, dest + len - 8, 8);
54 des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_DECRYPT);
55 memcpy(iv2, &iv1, 8); /* Note how iv1 == iv2 on entry and exit. */
57 des_cbc_encrypt(dest, dest, len, ks3, iv3, DES_ENCRYPT);
58 memcpy(iv3, dest + len - 8, 8);
62 SSH_3CBC_DECRYPT(des_key_schedule ks1,
63 des_key_schedule ks2, des_cblock *iv2,
64 des_key_schedule ks3, des_cblock *iv3,
65 void *dest, void *src,
72 des_cbc_encrypt(src, dest, len, ks3, iv3, DES_DECRYPT);
73 memcpy(iv3, src + len - 8, 8);
75 des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_ENCRYPT);
76 memcpy(iv2, dest + len - 8, 8);
78 des_cbc_encrypt(dest, dest, len, ks1, &iv1, DES_DECRYPT);
79 /* memcpy(&iv1, iv2, 8); */ /* Note how iv1 == iv2 on entry and exit. */
83 * SSH uses a variation on Blowfish, all bytes must be swapped before
84 * and after encryption/decryption. Thus the swap_bytes stuff (yuk).
88 swap_bytes(const unsigned char *src, unsigned char *dst_, int n)
90 u_int32_t *dst = (u_int32_t *)dst_; /* dst must be properly aligned. */
96 /* Process 8 bytes every lap. */
97 for (n = n / 8; n > 0; n--)
113 void (*cipher_attack_detected)(const char *fmt, ...) = fatal;
117 detect_cbc_attack(const unsigned char *src,
122 log("CRC-32 CBC insertion attack detected");
123 cipher_attack_detected("CRC-32 CBC insertion attack detected");
126 /* Names of all encryption algorithms. These must match the numbers defined
128 static char *cipher_names[] =
139 /* Returns a bit mask indicating which ciphers are supported by this
140 implementation. The bit mask has the corresponding bit set of each
143 unsigned int cipher_mask()
145 unsigned int mask = 0;
146 mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */
147 mask |= 1 << SSH_CIPHER_BLOWFISH;
151 /* Returns the name of the cipher. */
154 char *cipher_name(int cipher)
156 if (cipher < 0 || cipher >= sizeof(cipher_names) / sizeof(cipher_names[0]) ||
157 cipher_names[cipher] == NULL)
158 fatal("cipher_name: bad cipher number: %d", cipher);
159 return cipher_names[cipher];
162 /* Parses the name of the cipher. Returns the number of the corresponding
163 cipher, or -1 on error. */
166 cipher_number(const char *name)
169 for (i = 0; i < sizeof(cipher_names) / sizeof(cipher_names[0]); i++)
170 if (strcmp(cipher_names[i], name) == 0 &&
171 (cipher_mask() & (1 << i)))
176 /* Selects the cipher, and keys if by computing the MD5 checksum of the
177 passphrase and using the resulting 16 bytes as the key. */
179 void cipher_set_key_string(CipherContext *context, int cipher,
180 const char *passphrase, int for_encryption)
183 unsigned char digest[16];
186 MD5_Update(&md, (const unsigned char *)passphrase, strlen(passphrase));
187 MD5_Final(digest, &md);
189 cipher_set_key(context, cipher, digest, 16, for_encryption);
191 memset(digest, 0, sizeof(digest));
192 memset(&md, 0, sizeof(md));
195 /* Selects the cipher to use and sets the key. */
197 void cipher_set_key(CipherContext *context, int cipher,
198 const unsigned char *key, int keylen, int for_encryption)
200 unsigned char padded[32];
202 /* Set cipher type. */
203 context->type = cipher;
205 /* Get 32 bytes of key data. Pad if necessary. (So that code below does
206 not need to worry about key size). */
207 memset(padded, 0, sizeof(padded));
208 memcpy(padded, key, keylen < sizeof(padded) ? keylen : sizeof(padded));
210 /* Initialize the initialization vector. */
213 case SSH_CIPHER_NONE:
214 /* Has to stay for authfile saving of private key with no passphrase */
217 case SSH_CIPHER_3DES:
218 /* Note: the least significant bit of each byte of key is parity,
219 and must be ignored by the implementation. 16 bytes of key are
220 used (first and last keys are the same). */
222 error("Key length %d is insufficient for 3DES.", keylen);
223 des_set_key((void*)padded, context->u.des3.key1);
224 des_set_key((void*)(padded + 8), context->u.des3.key2);
226 des_set_key((void*)padded, context->u.des3.key3);
228 des_set_key((void*)(padded + 16), context->u.des3.key3);
229 memset(context->u.des3.iv2, 0, sizeof(context->u.des3.iv2));
230 memset(context->u.des3.iv3, 0, sizeof(context->u.des3.iv3));
233 case SSH_CIPHER_BLOWFISH:
234 BF_set_key(&context->u.bf.key, keylen, padded);
235 memset(context->u.bf.iv, 0, 8);
239 fatal("cipher_set_key: unknown cipher: %d", cipher);
241 memset(padded, 0, sizeof(padded));
244 /* Encrypts data using the cipher. */
246 void cipher_encrypt(CipherContext *context, unsigned char *dest,
247 const unsigned char *src, unsigned int len)
250 fatal("cipher_encrypt: bad plaintext length %d", len);
252 switch (context->type)
254 case SSH_CIPHER_NONE:
255 memcpy(dest, src, len);
258 case SSH_CIPHER_3DES:
259 SSH_3CBC_ENCRYPT(context->u.des3.key1,
260 context->u.des3.key2, &context->u.des3.iv2,
261 context->u.des3.key3, &context->u.des3.iv3,
262 dest, (void*)src, len);
265 case SSH_CIPHER_BLOWFISH:
266 swap_bytes(src, dest, len);
267 BF_cbc_encrypt(dest, dest, len,
268 &context->u.bf.key, context->u.bf.iv, BF_ENCRYPT);
269 swap_bytes(dest, dest, len);
273 fatal("cipher_encrypt: unknown cipher: %d", context->type);
277 /* Decrypts data using the cipher. */
279 void cipher_decrypt(CipherContext *context, unsigned char *dest,
280 const unsigned char *src, unsigned int len)
283 fatal("cipher_decrypt: bad ciphertext length %d", len);
285 switch (context->type)
287 case SSH_CIPHER_NONE:
288 memcpy(dest, src, len);
291 case SSH_CIPHER_3DES:
293 SSH_3CBC_DECRYPT(context->u.des3.key1,
294 context->u.des3.key2, &context->u.des3.iv2,
295 context->u.des3.key3, &context->u.des3.iv3,
296 dest, (void*)src, len);
299 case SSH_CIPHER_BLOWFISH:
300 detect_cbc_attack(src, len);
301 swap_bytes(src, dest, len);
302 BF_cbc_encrypt((void*)dest, dest, len,
303 &context->u.bf.key, context->u.bf.iv, BF_DECRYPT);
304 swap_bytes(dest, dest, len);
308 fatal("cipher_decrypt: unknown cipher: %d", context->type);