| /* |
| |
| cipher.c |
| |
| Author: Tatu Ylonen <ylo@cs.hut.fi> |
| |
| Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland |
| All rights reserved |
| |
| Created: Wed Apr 19 17:41:39 1995 ylo |
| |
| */ |
| |
| #include "config.h" |
| #include "includes.h" |
| RCSID("$Id: cipher.c,v 1.2 1999/10/28 03:25:17 damien Exp $"); |
| |
| #include "ssh.h" |
| #include "cipher.h" |
| |
| #ifdef HAVE_OPENSSL |
| #include <openssl/md5.h> |
| #endif |
| #ifdef HAVE_SSL |
| #include <ssl/md5.h> |
| #endif |
| |
| /* |
| * What kind of tripple DES are these 2 routines? |
| * |
| * Why is there a redundant initialization vector? |
| * |
| * If only iv3 was used, then, this would till effect have been |
| * outer-cbc. However, there is also a private iv1 == iv2 which |
| * perhaps makes differential analysis easier. On the other hand, the |
| * private iv1 probably makes the CRC-32 attack ineffective. This is a |
| * result of that there is no longer any known iv1 to use when |
| * choosing the X block. |
| */ |
| void |
| SSH_3CBC_ENCRYPT(des_key_schedule ks1, |
| des_key_schedule ks2, des_cblock *iv2, |
| des_key_schedule ks3, des_cblock *iv3, |
| void *dest, void *src, |
| unsigned int len) |
| { |
| des_cblock iv1; |
| |
| memcpy(&iv1, iv2, 8); |
| |
| des_cbc_encrypt(src, dest, len, ks1, &iv1, DES_ENCRYPT); |
| memcpy(&iv1, dest + len - 8, 8); |
| |
| des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_DECRYPT); |
| memcpy(iv2, &iv1, 8); /* Note how iv1 == iv2 on entry and exit. */ |
| |
| des_cbc_encrypt(dest, dest, len, ks3, iv3, DES_ENCRYPT); |
| memcpy(iv3, dest + len - 8, 8); |
| } |
| |
| void |
| SSH_3CBC_DECRYPT(des_key_schedule ks1, |
| des_key_schedule ks2, des_cblock *iv2, |
| des_key_schedule ks3, des_cblock *iv3, |
| void *dest, void *src, |
| unsigned int len) |
| { |
| des_cblock iv1; |
| |
| memcpy(&iv1, iv2, 8); |
| |
| des_cbc_encrypt(src, dest, len, ks3, iv3, DES_DECRYPT); |
| memcpy(iv3, src + len - 8, 8); |
| |
| des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_ENCRYPT); |
| memcpy(iv2, dest + len - 8, 8); |
| |
| des_cbc_encrypt(dest, dest, len, ks1, &iv1, DES_DECRYPT); |
| /* memcpy(&iv1, iv2, 8); */ /* Note how iv1 == iv2 on entry and exit. */ |
| } |
| |
| /* |
| * SSH uses a variation on Blowfish, all bytes must be swapped before |
| * and after encryption/decryption. Thus the swap_bytes stuff (yuk). |
| */ |
| static |
| void |
| swap_bytes(const unsigned char *src, unsigned char *dst_, int n) |
| { |
| u_int32_t *dst = (u_int32_t *)dst_; /* dst must be properly aligned. */ |
| union { |
| u_int32_t i; |
| char c[4]; |
| } t; |
| |
| /* assert((n & 7) == 0); */ |
| |
| /* Process 8 bytes every lap. */ |
| for (n = n / 8; n > 0; n--) |
| { |
| t.c[3] = *src++; |
| t.c[2] = *src++; |
| t.c[1] = *src++; |
| t.c[0] = *src++; |
| *dst++ = t.i; |
| |
| t.c[3] = *src++; |
| t.c[2] = *src++; |
| t.c[1] = *src++; |
| t.c[0] = *src++; |
| *dst++ = t.i; |
| } |
| } |
| |
| void (*cipher_attack_detected)(const char *fmt, ...) = fatal; |
| |
| static inline |
| void |
| detect_cbc_attack(const unsigned char *src, |
| unsigned int len) |
| { |
| return; |
| |
| log("CRC-32 CBC insertion attack detected"); |
| cipher_attack_detected("CRC-32 CBC insertion attack detected"); |
| } |
| |
| /* Names of all encryption algorithms. These must match the numbers defined |
| int cipher.h. */ |
| static char *cipher_names[] = |
| { |
| "none", |
| "idea", |
| "des", |
| "3des", |
| "tss", |
| "rc4", |
| "blowfish" |
| }; |
| |
| /* Returns a bit mask indicating which ciphers are supported by this |
| implementation. The bit mask has the corresponding bit set of each |
| supported cipher. */ |
| |
| unsigned int cipher_mask() |
| { |
| unsigned int mask = 0; |
| mask |= 1 << SSH_CIPHER_3DES; /* Mandatory */ |
| mask |= 1 << SSH_CIPHER_BLOWFISH; |
| return mask; |
| } |
| |
| /* Returns the name of the cipher. */ |
| |
| const |
| char *cipher_name(int cipher) |
| { |
| if (cipher < 0 || cipher >= sizeof(cipher_names) / sizeof(cipher_names[0]) || |
| cipher_names[cipher] == NULL) |
| fatal("cipher_name: bad cipher number: %d", cipher); |
| return cipher_names[cipher]; |
| } |
| |
| /* Parses the name of the cipher. Returns the number of the corresponding |
| cipher, or -1 on error. */ |
| |
| int |
| cipher_number(const char *name) |
| { |
| int i; |
| for (i = 0; i < sizeof(cipher_names) / sizeof(cipher_names[0]); i++) |
| if (strcmp(cipher_names[i], name) == 0 && |
| (cipher_mask() & (1 << i))) |
| return i; |
| return -1; |
| } |
| |
| /* Selects the cipher, and keys if by computing the MD5 checksum of the |
| passphrase and using the resulting 16 bytes as the key. */ |
| |
| void cipher_set_key_string(CipherContext *context, int cipher, |
| const char *passphrase, int for_encryption) |
| { |
| MD5_CTX md; |
| unsigned char digest[16]; |
| |
| MD5_Init(&md); |
| MD5_Update(&md, (const unsigned char *)passphrase, strlen(passphrase)); |
| MD5_Final(digest, &md); |
| |
| cipher_set_key(context, cipher, digest, 16, for_encryption); |
| |
| memset(digest, 0, sizeof(digest)); |
| memset(&md, 0, sizeof(md)); |
| } |
| |
| /* Selects the cipher to use and sets the key. */ |
| |
| void cipher_set_key(CipherContext *context, int cipher, |
| const unsigned char *key, int keylen, int for_encryption) |
| { |
| unsigned char padded[32]; |
| |
| /* Set cipher type. */ |
| context->type = cipher; |
| |
| /* Get 32 bytes of key data. Pad if necessary. (So that code below does |
| not need to worry about key size). */ |
| memset(padded, 0, sizeof(padded)); |
| memcpy(padded, key, keylen < sizeof(padded) ? keylen : sizeof(padded)); |
| |
| /* Initialize the initialization vector. */ |
| switch (cipher) |
| { |
| case SSH_CIPHER_NONE: |
| /* Has to stay for authfile saving of private key with no passphrase */ |
| break; |
| |
| case SSH_CIPHER_3DES: |
| /* Note: the least significant bit of each byte of key is parity, |
| and must be ignored by the implementation. 16 bytes of key are |
| used (first and last keys are the same). */ |
| if (keylen < 16) |
| error("Key length %d is insufficient for 3DES.", keylen); |
| des_set_key((void*)padded, context->u.des3.key1); |
| des_set_key((void*)(padded + 8), context->u.des3.key2); |
| if (keylen <= 16) |
| des_set_key((void*)padded, context->u.des3.key3); |
| else |
| des_set_key((void*)(padded + 16), context->u.des3.key3); |
| memset(context->u.des3.iv2, 0, sizeof(context->u.des3.iv2)); |
| memset(context->u.des3.iv3, 0, sizeof(context->u.des3.iv3)); |
| break; |
| |
| case SSH_CIPHER_BLOWFISH: |
| BF_set_key(&context->u.bf.key, keylen, padded); |
| memset(context->u.bf.iv, 0, 8); |
| break; |
| |
| default: |
| fatal("cipher_set_key: unknown cipher: %d", cipher); |
| } |
| memset(padded, 0, sizeof(padded)); |
| } |
| |
| /* Encrypts data using the cipher. */ |
| |
| void cipher_encrypt(CipherContext *context, unsigned char *dest, |
| const unsigned char *src, unsigned int len) |
| { |
| assert((len & 7) == 0); |
| |
| switch (context->type) |
| { |
| case SSH_CIPHER_NONE: |
| memcpy(dest, src, len); |
| break; |
| |
| case SSH_CIPHER_3DES: |
| SSH_3CBC_ENCRYPT(context->u.des3.key1, |
| context->u.des3.key2, &context->u.des3.iv2, |
| context->u.des3.key3, &context->u.des3.iv3, |
| dest, (void*)src, len); |
| break; |
| |
| case SSH_CIPHER_BLOWFISH: |
| swap_bytes(src, dest, len); |
| BF_cbc_encrypt(dest, dest, len, |
| &context->u.bf.key, context->u.bf.iv, BF_ENCRYPT); |
| swap_bytes(dest, dest, len); |
| break; |
| |
| default: |
| fatal("cipher_encrypt: unknown cipher: %d", context->type); |
| } |
| } |
| |
| /* Decrypts data using the cipher. */ |
| |
| void cipher_decrypt(CipherContext *context, unsigned char *dest, |
| const unsigned char *src, unsigned int len) |
| { |
| assert((len & 7) == 0); |
| |
| switch (context->type) |
| { |
| case SSH_CIPHER_NONE: |
| memcpy(dest, src, len); |
| break; |
| |
| case SSH_CIPHER_3DES: |
| /* CRC-32 attack? */ |
| SSH_3CBC_DECRYPT(context->u.des3.key1, |
| context->u.des3.key2, &context->u.des3.iv2, |
| context->u.des3.key3, &context->u.des3.iv3, |
| dest, (void*)src, len); |
| break; |
| |
| case SSH_CIPHER_BLOWFISH: |
| detect_cbc_attack(src, len); |
| swap_bytes(src, dest, len); |
| BF_cbc_encrypt((void*)dest, dest, len, |
| &context->u.bf.key, context->u.bf.iv, BF_DECRYPT); |
| swap_bytes(dest, dest, len); |
| break; |
| |
| default: |
| fatal("cipher_decrypt: unknown cipher: %d", context->type); |
| } |
| } |