/* This file is based on nss_sha512crypt.c which is based on the work of
* Ulrich Drepper (http://people.redhat.com/drepper/SHA-crypt.txt).
*
* libcrypto is used to provide SHA512 and random number generation.
* (http://www.openssl.org/docs/crypto/crypto.html).
*
* Sumit Bose <sbose@redhat.com>
* George McCollister <georgem@novatech-llc.com>
*/
/* SHA512-based Unix crypt implementation.
Released into the Public Domain by Ulrich Drepper <drepper@redhat.com>. */
#include "config.h"
#include <errno.h>
#include <limits.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/param.h>
#include <sys/types.h>
#include "util/util.h"
#include "util/sss_endian.h"
#include <openssl/evp.h>
#include <openssl/rand.h>
#include "sss_openssl.h"
/* Define our magic string to mark salt for SHA512 "encryption" replacement. */
const char sha512_salt_prefix[] = "$6$";
#define SALT_PREF_SIZE (sizeof(sha512_salt_prefix) - 1)
/* Prefix for optional rounds specification. */
const char sha512_rounds_prefix[] = "rounds=";
#define ROUNDS_SIZE (sizeof(sha512_rounds_prefix) - 1)
#define SALT_LEN_MAX 16
#define ROUNDS_DEFAULT 5000
#define ROUNDS_MIN 1000
#define ROUNDS_MAX 999999999
/* Table with characters for base64 transformation. */
const char b64t[64] =
"./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
/* base64 conversion function */
static inline void b64_from_24bit(char **dest, size_t *len, size_t n,
uint8_t b2, uint8_t b1, uint8_t b0)
{
uint32_t w;
size_t i;
if (*len < n) n = *len;
w = (b2 << 16) | (b1 << 8) | b0;
for (i = 0; i < n; i++) {
(*dest)[i] = b64t[w & 0x3f];
w >>= 6;
}
*len -= i;
*dest += i;
}
#define PTR_2_INT(x) ((x) - ((__typeof__ (x)) NULL))
#define ALIGN64 __alignof__(uint64_t)
static int sha512_crypt_r(const char *key,
const char *salt,
char *buffer, size_t buflen)
{
unsigned char temp_result[64] __attribute__((__aligned__(ALIGN64)));
unsigned char alt_result[64] __attribute__((__aligned__(ALIGN64)));
size_t rounds = ROUNDS_DEFAULT;
bool rounds_custom = false;
EVP_MD_CTX *alt_ctx = NULL;
EVP_MD_CTX *ctx;
size_t salt_len;
size_t key_len;
size_t cnt;
char *copied_salt = NULL;
char *copied_key = NULL;
char *p_bytes = NULL;
char *s_bytes = NULL;
int p1, p2, p3, pt, n;
unsigned int part;
char *cp, *tmp;
int ret;
/* Find beginning of salt string. The prefix should normally always be
* present. Just in case it is not. */
if (strncmp(salt, sha512_salt_prefix, SALT_PREF_SIZE) == 0) {
/* Skip salt prefix. */
salt += SALT_PREF_SIZE;
}
if (strncmp(salt, sha512_rounds_prefix, ROUNDS_SIZE) == 0) {
unsigned long int srounds;
const char *num;
char *endp;
num = salt + ROUNDS_SIZE;
srounds = strtoul(num, &endp, 10);
if (*endp == '$') {
salt = endp + 1;
if (srounds < ROUNDS_MIN) srounds = ROUNDS_MIN;
if (srounds > ROUNDS_MAX) srounds = ROUNDS_MAX;
rounds = srounds;
rounds_custom = true;
}
}
salt_len = MIN(strcspn(salt, "$"), SALT_LEN_MAX);
key_len = strlen(key);
if ((PTR_2_INT(key) % ALIGN64) != 0) {
tmp = (char *)alloca(key_len + ALIGN64);
key = copied_key = memcpy(tmp + ALIGN64 - PTR_2_INT(tmp) % ALIGN64, key, key_len);
}
if (PTR_2_INT(salt) % ALIGN64 != 0) {
tmp = (char *)alloca(salt_len + ALIGN64);
salt = copied_salt = memcpy(tmp + ALIGN64 - PTR_2_INT(tmp) % ALIGN64, salt, salt_len);
}
ctx = EVP_MD_CTX_new();
if (ctx == NULL) {
ret = ENOMEM;
goto done;
}
alt_ctx = EVP_MD_CTX_new();
if (alt_ctx == NULL) {
ret = ENOMEM;
goto done;
}
/* Prepare for the real work. */
if (!EVP_DigestInit_ex(ctx, EVP_sha512(), NULL)) {
ret = EIO;
goto done;
}
/* Add the key string. */
EVP_DigestUpdate(ctx, (const unsigned char *)key, key_len);
/* The last part is the salt string. This must be at most 16
* characters and it ends at the first `$' character (for
* compatibility with existing implementations). */
EVP_DigestUpdate(ctx, (const unsigned char *)salt, salt_len);
/* Compute alternate SHA512 sum with input KEY, SALT, and KEY.
* The final result will be added to the first context. */
if (!EVP_DigestInit_ex(alt_ctx, EVP_sha512(), NULL)) {
ret = EIO;
goto done;
}
/* Add key. */
EVP_DigestUpdate(alt_ctx, (const unsigned char *)key, key_len);
/* Add salt. */
EVP_DigestUpdate(alt_ctx, (const unsigned char *)salt, salt_len);
/* Add key again. */
EVP_DigestUpdate(alt_ctx, (const unsigned char *)key, key_len);
/* Now get result of this (64 bytes) and add it to the other context. */
EVP_DigestFinal_ex(alt_ctx, alt_result, &part);
/* Add for any character in the key one byte of the alternate sum. */
for (cnt = key_len; cnt > 64; cnt -= 64) {
EVP_DigestUpdate(ctx, alt_result, 64);
}
EVP_DigestUpdate(ctx, alt_result, cnt);
/* Take the binary representation of the length of the key and for every
* 1 add the alternate sum, for every 0 the key. */
for (cnt = key_len; cnt > 0; cnt >>= 1) {
if ((cnt & 1) != 0) {
EVP_DigestUpdate(ctx, alt_result, 64);
} else {
EVP_DigestUpdate(ctx, (const unsigned char *)key, key_len);
}
}
/* Create intermediate result. */
EVP_DigestFinal_ex(ctx, alt_result, &part);
/* Start computation of P byte sequence. */
if (!EVP_DigestInit_ex(alt_ctx, EVP_sha512(), NULL)) {
ret = EIO;
goto done;
}
/* For every character in the password add the entire password. */
for (cnt = 0; cnt < key_len; cnt++) {
EVP_DigestUpdate(alt_ctx, (const unsigned char *)key, key_len);
}
/* Finish the digest. */
EVP_DigestFinal_ex(alt_ctx, temp_result, &part);
/* Create byte sequence P. */
cp = p_bytes = alloca(key_len);
for (cnt = key_len; cnt >= 64; cnt -= 64) {
cp = mempcpy(cp, temp_result, 64);
}
memcpy(cp, temp_result, cnt);
/* Start computation of S byte sequence. */
if (!EVP_DigestInit_ex(alt_ctx, EVP_sha512(), NULL)) {
ret = EIO;
goto done;
}
/* For every character in the password add the entire salt. */
for (cnt = 0; cnt < 16 + alt_result[0]; cnt++) {
EVP_DigestUpdate(alt_ctx, (const unsigned char *)salt, salt_len);
}
/* Finish the digest. */
EVP_DigestFinal_ex(alt_ctx, temp_result, &part);
/* Create byte sequence S. */
cp = s_bytes = alloca(salt_len);
for (cnt = salt_len; cnt >= 64; cnt -= 64) {
cp = mempcpy(cp, temp_result, 64);
}
memcpy(cp, temp_result, cnt);
/* Repeatedly run the collected hash value through SHA512 to burn CPU cycles. */
for (cnt = 0; cnt < rounds; cnt++) {
if (!EVP_DigestInit_ex(ctx, EVP_sha512(), NULL)) {
ret = EIO;
goto done;
}
/* Add key or last result. */
if ((cnt & 1) != 0) {
EVP_DigestUpdate(ctx, (const unsigned char *)p_bytes, key_len);
} else {
EVP_DigestUpdate(ctx, alt_result, 64);
}
/* Add salt for numbers not divisible by 3. */
if (cnt % 3 != 0) {
EVP_DigestUpdate(ctx, (const unsigned char *)s_bytes, salt_len);
}
/* Add key for numbers not divisible by 7. */
if (cnt % 7 != 0) {
EVP_DigestUpdate(ctx, (const unsigned char *)p_bytes, key_len);
}
/* Add key or last result. */
if ((cnt & 1) != 0) {
EVP_DigestUpdate(ctx, alt_result, 64);
} else {
EVP_DigestUpdate(ctx, (const unsigned char *)p_bytes, key_len);
}
/* Create intermediate result. */
EVP_DigestFinal_ex(ctx, alt_result, &part);
}
/* Now we can construct the result string.
* It consists of three parts. */
if (buflen <= SALT_PREF_SIZE) {
ret = ERANGE;
goto done;
}
cp = stpncpy(buffer, sha512_salt_prefix, SALT_PREF_SIZE);
buflen -= SALT_PREF_SIZE;
if (rounds_custom) {
n = snprintf(cp, buflen, "%s%zu$",
sha512_rounds_prefix, rounds);
if (n < 0 || n >= buflen) {
ret = ERANGE;
goto done;
}
cp += n;
buflen -= n;
}
if (buflen <= salt_len + 1) {
ret = ERANGE;
goto done;
}
cp = stpncpy(cp, salt, salt_len);
*cp++ = '$';
buflen -= salt_len + 1;
/* fuzzyfill the base 64 string */
p1 = 0;
p2 = 21;
p3 = 42;
for (n = 0; n < 21; n++) {
b64_from_24bit(&cp, &buflen, 4, alt_result[p1], alt_result[p2], alt_result[p3]);
if (buflen == 0) {
ret = ERANGE;
goto done;
}
pt = p1;
p1 = p2 + 1;
p2 = p3 + 1;
p3 = pt + 1;
}
/* 64th and last byte */
b64_from_24bit(&cp, &buflen, 2, 0, 0, alt_result[p3]);
if (buflen == 0) {
ret = ERANGE;
goto done;
}
*cp = '\0';
ret = EOK;
done:
/* Clear the buffer for the intermediate result so that people attaching
* to processes or reading core dumps cannot get any information. We do it
* in this way to clear correct_words[] inside the SHA512 implementation
* as well. */
EVP_MD_CTX_free(ctx);
EVP_MD_CTX_free(alt_ctx);
if (p_bytes) memset(p_bytes, '\0', key_len);
if (s_bytes) memset(s_bytes, '\0', salt_len);
if (copied_key) memset(copied_key, '\0', key_len);
if (copied_salt) memset(copied_salt, '\0', salt_len);
memset(temp_result, '\0', sizeof(temp_result));
return ret;
}
int s3crypt_sha512(TALLOC_CTX *memctx,
const char *key, const char *salt, char **_hash)
{
char *hash;
int hlen = (sizeof (sha512_salt_prefix) - 1
+ sizeof (sha512_rounds_prefix) + 9 + 1
+ strlen (salt) + 1 + 86 + 1);
int ret;
hash = talloc_size(memctx, hlen);
if (!hash) return ENOMEM;
ret = sha512_crypt_r(key, salt, hash, hlen);
if (ret) return ret;
*_hash = hash;
return ret;
}
#define SALT_RAND_LEN 12
int s3crypt_gen_salt(TALLOC_CTX *memctx, char **_salt)
{
uint8_t rb[SALT_RAND_LEN];
char *salt, *cp;
size_t slen;
int ret;
salt = talloc_size(memctx, SALT_LEN_MAX + 1);
if (!salt) {
return ENOMEM;
}
ret = RAND_bytes(rb, SALT_RAND_LEN);
if (ret == 0) {
return EIO;
}
slen = SALT_LEN_MAX;
cp = salt;
b64_from_24bit(&cp, &slen, 4, rb[0], rb[1], rb[2]);
b64_from_24bit(&cp, &slen, 4, rb[3], rb[4], rb[5]);
b64_from_24bit(&cp, &slen, 4, rb[6], rb[7], rb[8]);
b64_from_24bit(&cp, &slen, 4, rb[9], rb[10], rb[11]);
*cp = '\0';
*_salt = salt;
return EOK;
}