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authorDamien Miller <djm@mindrot.org>1999-10-27 13:42:43 +1000
committerDamien Miller <djm@mindrot.org>1999-10-27 13:42:43 +1000
commitd4a8b7e34dd619a4debf9a206c81db26d1402ea6 (patch)
treea47d770a2f790f40d18b0982d4e55fa7cfb1fa3b /cipher.c
Initial revision
Diffstat (limited to 'cipher.c')
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+/*
+
+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 "includes.h"
+RCSID("$Id: cipher.c,v 1.1 1999/10/27 03:42:44 damien Exp $");
+
+#include "ssh.h"
+#include "cipher.h"
+
+#include <openssl/md5.h>
+
+/*
+ * 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);
+ }
+}