/*
* Copyright 2018-2019 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <openssl/des.h>
#include <openssl/evp.h>
#include <openssl/kdf.h>
#include "internal/cryptlib.h"
#include "crypto/evp.h"
#include "kdf_local.h"
/* KRB5 KDF defined in RFC 3961, Section 5.1 */
static int KRB5KDF(const EVP_CIPHER *cipher,
const unsigned char *key, size_t key_len,
const unsigned char *constant, size_t constant_len,
unsigned char *okey, size_t okey_len);
struct evp_kdf_impl_st {
const EVP_CIPHER *cipher;
unsigned char *key;
size_t key_len;
unsigned char *constant;
size_t constant_len;
};
static void krb5kdf_reset(EVP_KDF_IMPL *ctx);
static EVP_KDF_IMPL *krb5kdf_new(void)
{
EVP_KDF_IMPL *ctx;
if ((ctx = OPENSSL_zalloc(sizeof(*ctx))) == NULL)
KDFerr(KDF_F_KBKDF_NEW, ERR_R_MALLOC_FAILURE);
return ctx;
}
static void krb5kdf_free(EVP_KDF_IMPL *ctx)
{
krb5kdf_reset(ctx);
OPENSSL_free(ctx);
}
static void krb5kdf_reset(EVP_KDF_IMPL *ctx)
{
OPENSSL_clear_free(ctx->key, ctx->key_len);
OPENSSL_clear_free(ctx->constant, ctx->constant_len);
memset(ctx, 0, sizeof(*ctx));
}
static int krb5kdf_derive(EVP_KDF_IMPL *ctx, unsigned char *key,
size_t keylen)
{
if (ctx->cipher == NULL) {
KDFerr(KDF_F_KRB5KDF_DERIVE, KDF_R_MISSING_CIPHER);
return 0;
}
if (ctx->key == NULL) {
KDFerr(KDF_F_KRB5KDF_DERIVE, KDF_R_MISSING_KEY);
return 0;
}
if (ctx->constant == NULL) {
KDFerr(KDF_F_KRB5KDF_DERIVE, KDF_R_MISSING_CONSTANT);
return 0;
}
return KRB5KDF(ctx->cipher, ctx->key, ctx->key_len,
ctx->constant, ctx->constant_len,
key, keylen);
}
static size_t krb5kdf_size(EVP_KDF_IMPL *ctx)
{
if (ctx->cipher != NULL)
return EVP_CIPHER_key_length(ctx->cipher);
else
return EVP_MAX_KEY_LENGTH;
}
static int krb5kdf_parse_buffer_arg(unsigned char **dst, size_t *dst_len,
va_list args)
{
const unsigned char *p;
size_t len;
p = va_arg(args, const unsigned char *);
len = va_arg(args, size_t);
OPENSSL_clear_free(*dst, *dst_len);
if (len == 0) {
*dst = NULL;
*dst_len = 0;
return 1;
}
*dst = OPENSSL_memdup(p, len);
if (*dst == NULL)
return 0;
*dst_len = len;
return 1;
}
static int krb5kdf_ctrl(EVP_KDF_IMPL *ctx, int cmd, va_list args)
{
switch (cmd) {
case EVP_KDF_CTRL_SET_CIPHER:
ctx->cipher = va_arg(args, const EVP_CIPHER *);
if (ctx->cipher == NULL)
return 0;
return 1;
case EVP_KDF_CTRL_SET_KEY:
return krb5kdf_parse_buffer_arg(&ctx->key,
&ctx->key_len, args);
case EVP_KDF_CTRL_SET_KRB5KDF_CONSTANT:
return krb5kdf_parse_buffer_arg(&ctx->constant,
&ctx->constant_len, args);
default:
return -2;
}
}
static int krb5kdf_ctrl_str(EVP_KDF_IMPL *ctx, const char *type,
const char *value)
{
if (value == NULL) {
KDFerr(KDF_F_KDF_SSHKDF_CTRL_STR, KDF_R_VALUE_MISSING);
return 0;
}
if (strcmp(type, "cipher") == 0)
return kdf_cipher2ctrl(ctx, krb5kdf_ctrl, EVP_KDF_CTRL_SET_CIPHER, value);
if (strcmp(type, "key") == 0)
return kdf_str2ctrl(ctx, krb5kdf_ctrl,
EVP_KDF_CTRL_SET_KEY, value);
if (strcmp(type, "hexkey") == 0)
return kdf_hex2ctrl(ctx, krb5kdf_ctrl,
EVP_KDF_CTRL_SET_KEY, value);
if (strcmp(type, "constant") == 0)
return kdf_str2ctrl(ctx, krb5kdf_ctrl,
EVP_KDF_CTRL_SET_KRB5KDF_CONSTANT, value);
if (strcmp(type, "hexconstant") == 0)
return kdf_hex2ctrl(ctx, krb5kdf_ctrl,
EVP_KDF_CTRL_SET_KRB5KDF_CONSTANT, value);
KDFerr(KDF_F_KBKDF_CTRL_STR, KDF_R_UNKNOWN_PARAMETER_TYPE);
return -2;
}
#ifndef OPENSSL_NO_DES
/*
* DES3 is a special case, it requires a random-to-key function and its
* input truncated to 21 bytes of the 24 produced by the cipher.
* See RFC3961 6.3.1
*/
static int fixup_des3_key(unsigned char *key)
{
unsigned char *cblock;
int i, j;
for (i = 2; i >= 0; i--) {
cblock = &key[i * 8];
memmove(cblock, &key[i * 7], 7);
cblock[7] = 0;
for (j = 0; j < 7; j++)
cblock[7] |= (cblock[j] & 1) << (j + 1);
DES_set_odd_parity((DES_cblock *)cblock);
}
/* fail if keys are such that triple des degrades to single des */
if (CRYPTO_memcmp(&key[0], &key[8], 8) == 0 ||
CRYPTO_memcmp(&key[8], &key[16], 8) == 0) {
return 0;
}
return 1;
}
#endif
/*
* N-fold(K) where blocksize is N, and constant_len is K
* Note: Here |= denotes concatenation
*
* L = lcm(N,K)
* R = L/K
*
* for r: 1 -> R
* s |= constant rot 13*(r-1))
*
* block = 0
* for k: 1 -> K
* block += s[N(k-1)..(N-1)k] (one's complement addition)
*
* Optimizing for space we compute:
* for each l in L-1 -> 0:
* s[l] = (constant rot 13*(l/K))[l%k]
* block[l % N] += s[l] (with carry)
* finally add carry if any
*/
static void n_fold(unsigned char *block, unsigned int blocksize,
const unsigned char *constant, size_t constant_len)
{
unsigned int tmp, gcd, remainder, lcm, carry;
int b, l;
if (constant_len == blocksize) {
memcpy(block, constant, constant_len);
return;
}
/* Least Common Multiple of lengths: LCM(a,b)*/
gcd = blocksize;
remainder = constant_len;
/* Calculate Great Common Divisor first GCD(a,b) */
while (remainder != 0) {
tmp = gcd % remainder;
gcd = remainder;
remainder = tmp;
}
/* resulting a is the GCD, LCM(a,b) = |a*b|/GCD(a,b) */
lcm = blocksize * constant_len / gcd;
/* now spread out the bits */
memset(block, 0, blocksize);
/* last to first to be able to bring carry forward */
carry = 0;
for (l = lcm - 1; l >= 0; l--) {
unsigned int rotbits, rshift, rbyte;
/* destination byte in block is l % N */
b = l % blocksize;
/* Our virtual s buffer is R = L/K long (K = constant_len) */
/* So we rotate backwards from R-1 to 0 (none) rotations */
rotbits = 13 * (l / constant_len);
/* find the byte on s where rotbits falls onto */
rbyte = l - (rotbits / 8);
/* calculate how much shift on that byte */
rshift = rotbits & 0x07;
/* rbyte % constant_len gives us the unrotated byte in the
* constant buffer, get also the previous byte then
* appropriately shift them to get the rotated byte we need */
tmp = (constant[(rbyte-1) % constant_len] << (8 - rshift)
| constant[rbyte % constant_len] >> rshift)
& 0xff;
/* add with carry to any value placed by previous passes */
tmp += carry + block[b];
block[b] = tmp & 0xff;
/* save any carry that may be left */
carry = tmp >> 8;
}
/* if any carry is left at the end, add it through the number */
for (b = blocksize - 1; b >= 0 && carry != 0; b--) {
carry += block[b];
block[b] = carry & 0xff;
carry >>= 8;
}
}
static int cipher_init(EVP_CIPHER_CTX *ctx,
const EVP_CIPHER *cipher,
const unsigned char *key, size_t key_len)
{
int klen, ret;
ret = EVP_EncryptInit_ex(ctx, cipher, NULL, key, NULL);
if (!ret)
goto out;
/* set the key len for the odd variable key len cipher */
klen = EVP_CIPHER_CTX_key_length(ctx);
if (key_len != (size_t)klen) {
ret = EVP_CIPHER_CTX_set_key_length(ctx, key_len);
if (!ret)
goto out;
}
/* we never want padding, either the length requested is a multiple of
* the cipher block size or we are passed a cipher that can cope with
* partial blocks via techniques like cipher text stealing */
ret = EVP_CIPHER_CTX_set_padding(ctx, 0);
if (!ret)
goto out;
out:
return ret;
}
static int KRB5KDF(const EVP_CIPHER *cipher,
const unsigned char *key, size_t key_len,
const unsigned char *constant, size_t constant_len,
unsigned char *okey, size_t okey_len)
{
EVP_CIPHER_CTX *ctx = NULL;
unsigned char block[EVP_MAX_BLOCK_LENGTH * 2];
unsigned char *plainblock, *cipherblock;
size_t blocksize;
size_t cipherlen;
size_t osize;
int des3_no_fixup = 0;
int ret;
if (key_len != okey_len) {
/* special case for 3des, where the caller may be requesting
* the random raw key, instead of the fixed up key */
if (EVP_CIPHER_nid(cipher) == NID_des_ede3_cbc &&
key_len == 24 && okey_len == 21) {
des3_no_fixup = 1;
} else {
KDFerr(KDF_F_KRB5KDF, KDF_R_WRONG_OUTPUT_BUFFER_SIZE);
return 0;
}
}
ctx = EVP_CIPHER_CTX_new();
if (ctx == NULL)
return 0;
ret = cipher_init(ctx, cipher, key, key_len);
if (!ret)
goto out;
/* Initialize input block */
blocksize = EVP_CIPHER_CTX_block_size(ctx);
if (constant_len == 0 || constant_len > blocksize) {
KDFerr(KDF_F_KRB5KDF, KDF_R_INVALID_CONSTANT_LENGTH);
ret = 0;
goto out;
}
n_fold(block, blocksize, constant, constant_len);
plainblock = block;
cipherblock = block + EVP_MAX_BLOCK_LENGTH;
for (osize = 0; osize < okey_len; osize += cipherlen) {
int olen;
ret = EVP_EncryptUpdate(ctx, cipherblock, &olen,
plainblock, blocksize);
if (!ret)
goto out;
cipherlen = olen;
ret = EVP_EncryptFinal_ex(ctx, cipherblock, &olen);
if (!ret)
goto out;
if (olen != 0) {
KDFerr(KDF_F_KRB5KDF, KDF_R_WRONG_FINAL_BLOCK_LENGTH);
ret = 0;
goto out;
}
/* write cipherblock out */
if (cipherlen > okey_len - osize)
cipherlen = okey_len - osize;
memcpy(okey + osize, cipherblock, cipherlen);
if (okey_len > osize + cipherlen) {
/* we need to reinitialize cipher context per spec */
ret = EVP_CIPHER_CTX_reset(ctx);
if (!ret)
goto out;
ret = cipher_init(ctx, cipher, key, key_len);
if (!ret)
goto out;
/* also swap block offsets so last ciphertext becomes new
* plaintext */
plainblock = cipherblock;
if (cipherblock == block) {
cipherblock += EVP_MAX_BLOCK_LENGTH;
} else {
cipherblock = block;
}
}
}
#ifndef OPENSSL_NO_DES
if (EVP_CIPHER_nid(cipher) == NID_des_ede3_cbc && !des3_no_fixup) {
ret = fixup_des3_key(okey);
if (!ret) {
KDFerr(KDF_F_KRB5KDF, KDF_R_FAILED_TO_GENERATE_KEY);
goto out;
}
}
#endif
ret = 1;
out:
EVP_CIPHER_CTX_free(ctx);
OPENSSL_cleanse(block, EVP_MAX_BLOCK_LENGTH * 2);
return ret;
}
const EVP_KDF_METHOD krb5kdf_kdf_meth = {
EVP_KDF_KRB5KDF,
krb5kdf_new,
krb5kdf_free,
krb5kdf_reset,
krb5kdf_ctrl,
krb5kdf_ctrl_str,
krb5kdf_size,
krb5kdf_derive,
};