Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 1 | /* |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 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 | */ |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 13 | |
| 14 | #include "includes.h" |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 15 | RCSID("$Id: cipher.c,v 1.7 1999/11/24 13:26:22 damien Exp $"); |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 16 | |
| 17 | #include "ssh.h" |
| 18 | #include "cipher.h" |
| 19 | |
Damien Miller | 7f6ea02 | 1999-10-28 13:25:17 +1000 | [diff] [blame] | 20 | #ifdef HAVE_OPENSSL |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 21 | #include <openssl/md5.h> |
Damien Miller | 7f6ea02 | 1999-10-28 13:25:17 +1000 | [diff] [blame] | 22 | #endif |
| 23 | #ifdef HAVE_SSL |
| 24 | #include <ssl/md5.h> |
| 25 | #endif |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 26 | |
| 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 | */ |
| 39 | void |
| 40 | SSH_3CBC_ENCRYPT(des_key_schedule ks1, |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 41 | des_key_schedule ks2, des_cblock * iv2, |
| 42 | des_key_schedule ks3, des_cblock * iv3, |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 43 | void *dest, void *src, |
| 44 | unsigned int len) |
| 45 | { |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 46 | des_cblock iv1; |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 47 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 48 | memcpy(&iv1, iv2, 8); |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 49 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 50 | des_cbc_encrypt(src, dest, len, ks1, &iv1, DES_ENCRYPT); |
| 51 | memcpy(&iv1, dest + len - 8, 8); |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 52 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 53 | des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_DECRYPT); |
| 54 | memcpy(iv2, &iv1, 8); /* Note how iv1 == iv2 on entry and exit. */ |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 55 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 56 | des_cbc_encrypt(dest, dest, len, ks3, iv3, DES_ENCRYPT); |
| 57 | memcpy(iv3, dest + len - 8, 8); |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 58 | } |
| 59 | |
| 60 | void |
| 61 | SSH_3CBC_DECRYPT(des_key_schedule ks1, |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 62 | des_key_schedule ks2, des_cblock * iv2, |
| 63 | des_key_schedule ks3, des_cblock * iv3, |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 64 | void *dest, void *src, |
| 65 | unsigned int len) |
| 66 | { |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 67 | des_cblock iv1; |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 68 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 69 | memcpy(&iv1, iv2, 8); |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 70 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 71 | des_cbc_encrypt(src, dest, len, ks3, iv3, DES_DECRYPT); |
| 72 | memcpy(iv3, src + len - 8, 8); |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 73 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 74 | des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_ENCRYPT); |
| 75 | memcpy(iv2, dest + len - 8, 8); |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 76 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 77 | 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 Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 80 | } |
| 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 Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 86 | static void |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 87 | swap_bytes(const unsigned char *src, unsigned char *dst_, int n) |
| 88 | { |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 89 | /* 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 Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 95 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 96 | /* 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 Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 110 | } |
| 111 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 112 | void (*cipher_attack_detected) (const char *fmt,...) = fatal; |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 113 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 114 | static inline void |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 115 | detect_cbc_attack(const unsigned char *src, |
| 116 | unsigned int len) |
| 117 | { |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 118 | return; |
| 119 | |
| 120 | log("CRC-32 CBC insertion attack detected"); |
| 121 | cipher_attack_detected("CRC-32 CBC insertion attack detected"); |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 122 | } |
| 123 | |
| 124 | /* Names of all encryption algorithms. These must match the numbers defined |
| 125 | int cipher.h. */ |
| 126 | static char *cipher_names[] = |
| 127 | { |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 128 | "none", |
| 129 | "idea", |
| 130 | "des", |
| 131 | "3des", |
| 132 | "tss", |
| 133 | "rc4", |
| 134 | "blowfish" |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 135 | }; |
| 136 | |
| 137 | /* Returns a bit mask indicating which ciphers are supported by this |
| 138 | implementation. The bit mask has the corresponding bit set of each |
| 139 | supported cipher. */ |
| 140 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 141 | unsigned int |
| 142 | cipher_mask() |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 143 | { |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 144 | unsigned int mask = 0; |
| 145 | mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */ |
| 146 | mask |= 1 << SSH_CIPHER_BLOWFISH; |
| 147 | return mask; |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 148 | } |
| 149 | |
| 150 | /* Returns the name of the cipher. */ |
| 151 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 152 | const char * |
| 153 | cipher_name(int cipher) |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 154 | { |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 155 | if (cipher < 0 || cipher >= sizeof(cipher_names) / sizeof(cipher_names[0]) || |
| 156 | cipher_names[cipher] == NULL) |
| 157 | fatal("cipher_name: bad cipher number: %d", cipher); |
| 158 | return cipher_names[cipher]; |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 159 | } |
| 160 | |
| 161 | /* Parses the name of the cipher. Returns the number of the corresponding |
| 162 | cipher, or -1 on error. */ |
| 163 | |
| 164 | int |
| 165 | cipher_number(const char *name) |
| 166 | { |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 167 | int i; |
| 168 | for (i = 0; i < sizeof(cipher_names) / sizeof(cipher_names[0]); i++) |
| 169 | if (strcmp(cipher_names[i], name) == 0 && |
| 170 | (cipher_mask() & (1 << i))) |
| 171 | return i; |
| 172 | return -1; |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 173 | } |
| 174 | |
| 175 | /* Selects the cipher, and keys if by computing the MD5 checksum of the |
| 176 | passphrase and using the resulting 16 bytes as the key. */ |
| 177 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 178 | void |
| 179 | cipher_set_key_string(CipherContext *context, int cipher, |
| 180 | const char *passphrase, int for_encryption) |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 181 | { |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 182 | MD5_CTX md; |
| 183 | unsigned char digest[16]; |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 184 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 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)); |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 193 | } |
| 194 | |
| 195 | /* Selects the cipher to use and sets the key. */ |
| 196 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 197 | void |
| 198 | cipher_set_key(CipherContext *context, int cipher, |
| 199 | const unsigned char *key, int keylen, int for_encryption) |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 200 | { |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 201 | unsigned char padded[32]; |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 202 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 203 | /* Set cipher type. */ |
| 204 | context->type = cipher; |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 205 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 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)); |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 210 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 211 | /* Initialize the initialization vector. */ |
| 212 | switch (cipher) { |
| 213 | case SSH_CIPHER_NONE: |
| 214 | /* Has to stay for authfile saving of private key with |
| 215 | no passphrase */ |
| 216 | break; |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 217 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 218 | case SSH_CIPHER_3DES: |
| 219 | /* Note: the least significant bit of each byte of key is |
| 220 | parity, and must be ignored by the implementation. 16 |
| 221 | bytes of key are used (first and last keys are the |
| 222 | same). */ |
| 223 | if (keylen < 16) |
| 224 | error("Key length %d is insufficient for 3DES.", keylen); |
| 225 | des_set_key((void *) padded, context->u.des3.key1); |
| 226 | des_set_key((void *) (padded + 8), context->u.des3.key2); |
| 227 | if (keylen <= 16) |
| 228 | des_set_key((void *) padded, context->u.des3.key3); |
| 229 | else |
| 230 | des_set_key((void *) (padded + 16), context->u.des3.key3); |
| 231 | memset(context->u.des3.iv2, 0, sizeof(context->u.des3.iv2)); |
| 232 | memset(context->u.des3.iv3, 0, sizeof(context->u.des3.iv3)); |
| 233 | break; |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 234 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 235 | case SSH_CIPHER_BLOWFISH: |
| 236 | BF_set_key(&context->u.bf.key, keylen, padded); |
| 237 | memset(context->u.bf.iv, 0, 8); |
| 238 | break; |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 239 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 240 | default: |
| 241 | fatal("cipher_set_key: unknown cipher: %s", cipher_name(cipher)); |
| 242 | } |
| 243 | memset(padded, 0, sizeof(padded)); |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 244 | } |
| 245 | |
| 246 | /* Encrypts data using the cipher. */ |
| 247 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 248 | void |
| 249 | cipher_encrypt(CipherContext *context, unsigned char *dest, |
| 250 | const unsigned char *src, unsigned int len) |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 251 | { |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 252 | if ((len & 7) != 0) |
| 253 | fatal("cipher_encrypt: bad plaintext length %d", len); |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 254 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 255 | switch (context->type) { |
| 256 | case SSH_CIPHER_NONE: |
| 257 | memcpy(dest, src, len); |
| 258 | break; |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 259 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 260 | case SSH_CIPHER_3DES: |
| 261 | SSH_3CBC_ENCRYPT(context->u.des3.key1, |
| 262 | context->u.des3.key2, &context->u.des3.iv2, |
| 263 | context->u.des3.key3, &context->u.des3.iv3, |
| 264 | dest, (void *) src, len); |
| 265 | break; |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 266 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 267 | case SSH_CIPHER_BLOWFISH: |
| 268 | swap_bytes(src, dest, len); |
| 269 | BF_cbc_encrypt(dest, dest, len, |
| 270 | &context->u.bf.key, context->u.bf.iv, |
| 271 | BF_ENCRYPT); |
| 272 | swap_bytes(dest, dest, len); |
| 273 | break; |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 274 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 275 | default: |
| 276 | fatal("cipher_encrypt: unknown cipher: %s", cipher_name(context->type)); |
| 277 | } |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 278 | } |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 279 | |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 280 | /* Decrypts data using the cipher. */ |
| 281 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 282 | void |
| 283 | cipher_decrypt(CipherContext *context, unsigned char *dest, |
| 284 | const unsigned char *src, unsigned int len) |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 285 | { |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 286 | if ((len & 7) != 0) |
| 287 | fatal("cipher_decrypt: bad ciphertext length %d", len); |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 288 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 289 | switch (context->type) { |
| 290 | case SSH_CIPHER_NONE: |
| 291 | memcpy(dest, src, len); |
| 292 | break; |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 293 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 294 | case SSH_CIPHER_3DES: |
| 295 | /* CRC-32 attack? */ |
| 296 | SSH_3CBC_DECRYPT(context->u.des3.key1, |
| 297 | context->u.des3.key2, &context->u.des3.iv2, |
| 298 | context->u.des3.key3, &context->u.des3.iv3, |
| 299 | dest, (void *) src, len); |
| 300 | break; |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 301 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 302 | case SSH_CIPHER_BLOWFISH: |
| 303 | detect_cbc_attack(src, len); |
| 304 | swap_bytes(src, dest, len); |
| 305 | BF_cbc_encrypt((void *) dest, dest, len, |
| 306 | &context->u.bf.key, context->u.bf.iv, |
| 307 | BF_DECRYPT); |
| 308 | swap_bytes(dest, dest, len); |
| 309 | break; |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 310 | |
Damien Miller | 95def09 | 1999-11-25 00:26:21 +1100 | [diff] [blame] | 311 | default: |
| 312 | fatal("cipher_decrypt: unknown cipher: %s", cipher_name(context->type)); |
| 313 | } |
Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 314 | } |