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, (char *)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, (char *)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, (char *)src + len - 8, 8);
75 des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_ENCRYPT);
76 memcpy(iv2, (char *)dest + len - 8, 8);
78 des_cbc_encrypt(dest, dest, len, ks1, &iv1, DES_DECRYPT);
79 /* memcpy(&iv1, iv2, 8); */
80 /* Note how iv1 == iv2 on entry and exit. */
84 * SSH uses a variation on Blowfish, all bytes must be swapped before
85 * and after encryption/decryption. Thus the swap_bytes stuff (yuk).
88 swap_bytes(const unsigned char *src, unsigned char *dst_, int n)
90 /* dst must be properly aligned. */
91 u_int32_t *dst = (u_int32_t *) dst_;
97 /* Process 8 bytes every lap. */
98 for (n = n / 8; n > 0; n--) {
113 void (*cipher_attack_detected) (const char *fmt,...) = fatal;
116 detect_cbc_attack(const unsigned char *src,
121 log("CRC-32 CBC insertion attack detected");
122 cipher_attack_detected("CRC-32 CBC insertion attack detected");
126 * Names of all encryption algorithms.
127 * These must match the numbers defined in cipher.h.
129 static char *cipher_names[] =
141 * Returns a bit mask indicating which ciphers are supported by this
142 * implementation. The bit mask has the corresponding bit set of each
149 unsigned int mask = 0;
150 mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */
151 mask |= 1 << SSH_CIPHER_BLOWFISH;
155 /* Returns the name of the cipher. */
158 cipher_name(int cipher)
160 if (cipher < 0 || cipher >= sizeof(cipher_names) / sizeof(cipher_names[0]) ||
161 cipher_names[cipher] == NULL)
162 fatal("cipher_name: bad cipher number: %d", cipher);
163 return cipher_names[cipher];
167 * Parses the name of the cipher. Returns the number of the corresponding
168 * cipher, or -1 on error.
172 cipher_number(const char *name)
175 for (i = 0; i < sizeof(cipher_names) / sizeof(cipher_names[0]); i++)
176 if (strcmp(cipher_names[i], name) == 0 &&
177 (cipher_mask() & (1 << i)))
183 * Selects the cipher, and keys if by computing the MD5 checksum of the
184 * passphrase and using the resulting 16 bytes as the key.
188 cipher_set_key_string(CipherContext *context, int cipher,
189 const char *passphrase, int for_encryption)
192 unsigned char digest[16];
195 MD5_Update(&md, (const unsigned char *) passphrase, strlen(passphrase));
196 MD5_Final(digest, &md);
198 cipher_set_key(context, cipher, digest, 16, for_encryption);
200 memset(digest, 0, sizeof(digest));
201 memset(&md, 0, sizeof(md));
204 /* Selects the cipher to use and sets the key. */
207 cipher_set_key(CipherContext *context, int cipher,
208 const unsigned char *key, int keylen, int for_encryption)
210 unsigned char padded[32];
212 /* Set cipher type. */
213 context->type = cipher;
215 /* Get 32 bytes of key data. Pad if necessary. (So that code
216 below does not need to worry about key size). */
217 memset(padded, 0, sizeof(padded));
218 memcpy(padded, key, keylen < sizeof(padded) ? keylen : sizeof(padded));
220 /* Initialize the initialization vector. */
222 case SSH_CIPHER_NONE:
224 * Has to stay for authfile saving of private key with no
229 case SSH_CIPHER_3DES:
231 * Note: the least significant bit of each byte of key is
232 * parity, and must be ignored by the implementation. 16
233 * bytes of key are used (first and last keys are the same).
236 error("Key length %d is insufficient for 3DES.", keylen);
237 des_set_key((void *) padded, context->u.des3.key1);
238 des_set_key((void *) (padded + 8), context->u.des3.key2);
240 des_set_key((void *) padded, context->u.des3.key3);
242 des_set_key((void *) (padded + 16), context->u.des3.key3);
243 memset(context->u.des3.iv2, 0, sizeof(context->u.des3.iv2));
244 memset(context->u.des3.iv3, 0, sizeof(context->u.des3.iv3));
247 case SSH_CIPHER_BLOWFISH:
248 BF_set_key(&context->u.bf.key, keylen, padded);
249 memset(context->u.bf.iv, 0, 8);
253 fatal("cipher_set_key: unknown cipher: %s", cipher_name(cipher));
255 memset(padded, 0, sizeof(padded));
258 /* Encrypts data using the cipher. */
261 cipher_encrypt(CipherContext *context, unsigned char *dest,
262 const unsigned char *src, unsigned int len)
265 fatal("cipher_encrypt: bad plaintext length %d", len);
267 switch (context->type) {
268 case SSH_CIPHER_NONE:
269 memcpy(dest, src, len);
272 case SSH_CIPHER_3DES:
273 SSH_3CBC_ENCRYPT(context->u.des3.key1,
274 context->u.des3.key2, &context->u.des3.iv2,
275 context->u.des3.key3, &context->u.des3.iv3,
276 dest, (void *) src, len);
279 case SSH_CIPHER_BLOWFISH:
280 swap_bytes(src, dest, len);
281 BF_cbc_encrypt(dest, dest, len,
282 &context->u.bf.key, context->u.bf.iv,
284 swap_bytes(dest, dest, len);
288 fatal("cipher_encrypt: unknown cipher: %s", cipher_name(context->type));
292 /* Decrypts data using the cipher. */
295 cipher_decrypt(CipherContext *context, unsigned char *dest,
296 const unsigned char *src, unsigned int len)
299 fatal("cipher_decrypt: bad ciphertext length %d", len);
301 switch (context->type) {
302 case SSH_CIPHER_NONE:
303 memcpy(dest, src, len);
306 case SSH_CIPHER_3DES:
308 SSH_3CBC_DECRYPT(context->u.des3.key1,
309 context->u.des3.key2, &context->u.des3.iv2,
310 context->u.des3.key3, &context->u.des3.iv3,
311 dest, (void *) src, len);
314 case SSH_CIPHER_BLOWFISH:
315 detect_cbc_attack(src, len);
316 swap_bytes(src, dest, len);
317 BF_cbc_encrypt((void *) dest, dest, len,
318 &context->u.bf.key, context->u.bf.iv,
320 swap_bytes(dest, dest, len);
324 fatal("cipher_decrypt: unknown cipher: %s", cipher_name(context->type));