/* One way encryption based on SHA512 sum.
Copyright (C) 2007-2017 Free Software Foundation, Inc.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public License
as published by the Free Software Foundation; either version 2.1 of
the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, see
<https://www.gnu.org/licenses/>. */
#include "crypt-port.h"
#include "crypt-private.h"
#include "alg-sha512.h"
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#if INCLUDE_sha512
/* Define our magic string to mark salt for SHA512 "encryption"
replacement. */
static const char sha512_salt_prefix[] = "$6$";
/* Prefix for optional rounds specification. */
static const char sha512_rounds_prefix[] = "rounds=";
/* Maximum salt string length. */
#define SALT_LEN_MAX 16
/* Default number of rounds if not explicitly specified. */
#define ROUNDS_DEFAULT 5000
/* Minimum number of rounds. */
#define ROUNDS_MIN 1000
/* Maximum number of rounds. */
#define ROUNDS_MAX 999999999
/* The maximum possible length of a SHA512-hashed password string,
including the terminating NUL character. Prefix (including its NUL)
+ rounds tag ("rounds=$" = "rounds=\0") + strlen(ROUNDS_MAX)
+ salt (up to SALT_LEN_MAX chars) + '$' + hash (86 chars). */
#define LENGTH_OF_NUMBER(n) (sizeof #n - 1)
#define SHA512_HASH_LENGTH \
(sizeof (sha512_salt_prefix) + sizeof (sha512_rounds_prefix) + \
LENGTH_OF_NUMBER (ROUNDS_MAX) + SALT_LEN_MAX + 1 + 86)
static_assert (SHA512_HASH_LENGTH <= CRYPT_OUTPUT_SIZE,
"CRYPT_OUTPUT_SIZE is too small for SHA512");
/* A sha512_buffer holds all of the sensitive intermediate data. */
struct sha512_buffer
{
struct sha512_ctx ctx;
uint8_t result[64];
uint8_t p_bytes[64];
uint8_t s_bytes[64];
};
static_assert (sizeof (struct sha512_buffer) <= ALG_SPECIFIC_SIZE,
"ALG_SPECIFIC_SIZE is too small for SHA512");
/* Table with characters for base64 transformation. */
static const char b64t[] =
"./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
/* Subroutine of _xcrypt_crypt_sha512_rn: Feed CTX with LEN bytes of a
virtual byte sequence consisting of BLOCK repeated over and over
indefinitely. */
static void
sha512_process_recycled_bytes (unsigned char block[64], size_t len,
struct sha512_ctx *ctx)
{
size_t cnt;
for (cnt = len; cnt >= 64; cnt -= 64)
sha512_process_bytes (block, 64, ctx);
sha512_process_bytes (block, cnt, ctx);
}
void
crypt_sha512_rn (const char *phrase, size_t phr_size,
const char *setting, size_t ARG_UNUSED (set_size),
uint8_t *output, size_t out_size,
void *scratch, size_t scr_size)
{
/* This shouldn't ever happen, but... */
if (out_size < SHA512_HASH_LENGTH
|| scr_size < sizeof (struct sha512_buffer))
{
errno = ERANGE;
return;
}
struct sha512_buffer *buf = scratch;
struct sha512_ctx *ctx = &buf->ctx;
uint8_t *result = buf->result;
uint8_t *p_bytes = buf->p_bytes;
uint8_t *s_bytes = buf->s_bytes;
char *cp = (char *)output;
const char *salt = setting;
size_t salt_size;
size_t cnt;
/* Default number of rounds. */
size_t rounds = ROUNDS_DEFAULT;
bool rounds_custom = false;
/* Find beginning of salt string. The prefix should normally always
be present. Just in case it is not. */
if (strncmp (sha512_salt_prefix, salt, sizeof (sha512_salt_prefix) - 1) == 0)
/* Skip salt prefix. */
salt += sizeof (sha512_salt_prefix) - 1;
if (strncmp (salt, sha512_rounds_prefix, sizeof (sha512_rounds_prefix) - 1)
== 0)
{
const char *num = salt + sizeof (sha512_rounds_prefix) - 1;
/* Do not allow an explicit setting of zero rounds, nor of the
default number of rounds, nor leading zeroes on the rounds. */
if (!(*num >= '1' && *num <= '9'))
{
errno = EINVAL;
return;
}
errno = 0;
char *endp;
rounds = strtoul (num, &endp, 10);
if (endp == num || *endp != '$'
|| rounds < ROUNDS_MIN
|| rounds > ROUNDS_MAX
|| errno)
{
errno = EINVAL;
return;
}
salt = endp + 1;
rounds_custom = true;
}
salt_size = strspn (salt, b64t);
if (salt[salt_size] && salt[salt_size] != '$')
{
errno = EINVAL;
return;
}
if (salt_size > SALT_LEN_MAX)
salt_size = SALT_LEN_MAX;
phr_size = strlen (phrase);
/* Compute alternate SHA512 sum with input PHRASE, SALT, and PHRASE. The
final result will be added to the first context. */
sha512_init_ctx (ctx);
/* Add phrase. */
sha512_process_bytes (phrase, phr_size, ctx);
/* Add salt. */
sha512_process_bytes (salt, salt_size, ctx);
/* Add phrase again. */
sha512_process_bytes (phrase, phr_size, ctx);
/* Now get result of this (64 bytes) and add it to the other
context. */
sha512_finish_ctx (ctx, result);
/* Prepare for the real work. */
sha512_init_ctx (ctx);
/* Add the phrase string. */
sha512_process_bytes (phrase, phr_size, ctx);
/* The last part is the salt string. This must be at most 8
characters and it ends at the first `$' character (for
compatibility with existing implementations). */
sha512_process_bytes (salt, salt_size, ctx);
/* Add for any character in the phrase one byte of the alternate sum. */
for (cnt = phr_size; cnt > 64; cnt -= 64)
sha512_process_bytes (result, 64, ctx);
sha512_process_bytes (result, cnt, ctx);
/* Take the binary representation of the length of the phrase and for every
1 add the alternate sum, for every 0 the phrase. */
for (cnt = phr_size; cnt > 0; cnt >>= 1)
if ((cnt & 1) != 0)
sha512_process_bytes (result, 64, ctx);
else
sha512_process_bytes (phrase, phr_size, ctx);
/* Create intermediate result. */
sha512_finish_ctx (ctx, result);
/* Start computation of P byte sequence. */
sha512_init_ctx (ctx);
/* For every character in the password add the entire password. */
for (cnt = 0; cnt < phr_size; ++cnt)
sha512_process_bytes (phrase, phr_size, ctx);
/* Finish the digest. */
sha512_finish_ctx (ctx, p_bytes);
/* Start computation of S byte sequence. */
sha512_init_ctx (ctx);
/* For every character in the password add the entire password. */
for (cnt = 0; cnt < (size_t) 16 + (size_t) result[0]; ++cnt)
sha512_process_bytes (salt, salt_size, ctx);
/* Finish the digest. */
sha512_finish_ctx (ctx, s_bytes);
/* Repeatedly run the collected hash value through SHA512 to burn
CPU cycles. */
for (cnt = 0; cnt < rounds; ++cnt)
{
/* New context. */
sha512_init_ctx (ctx);
/* Add phrase or last result. */
if ((cnt & 1) != 0)
sha512_process_recycled_bytes (p_bytes, phr_size, ctx);
else
sha512_process_bytes (result, 64, ctx);
/* Add salt for numbers not divisible by 3. */
if (cnt % 3 != 0)
sha512_process_recycled_bytes (s_bytes, salt_size, ctx);
/* Add phrase for numbers not divisible by 7. */
if (cnt % 7 != 0)
sha512_process_recycled_bytes (p_bytes, phr_size, ctx);
/* Add phrase or last result. */
if ((cnt & 1) != 0)
sha512_process_bytes (result, 64, ctx);
else
sha512_process_recycled_bytes (p_bytes, phr_size, ctx);
/* Create intermediate result. */
sha512_finish_ctx (ctx, result);
}
/* Now we can construct the result string. It consists of four
parts, one of which is optional. We already know that buflen is
at least sha512_hash_length, therefore none of the string bashing
below can overflow the buffer. */
memcpy (cp, sha512_salt_prefix, sizeof (sha512_salt_prefix) - 1);
cp += sizeof (sha512_salt_prefix) - 1;
if (rounds_custom)
{
int n = snprintf (cp,
SHA512_HASH_LENGTH - (sizeof (sha512_salt_prefix) - 1),
"%s%zu$", sha512_rounds_prefix, rounds);
cp += n;
}
memcpy (cp, salt, salt_size);
cp += salt_size;
*cp++ = '$';
#define b64_from_24bit(B2, B1, B0, N) \
do { \
unsigned int w = ((((unsigned int)(B2)) << 16) | \
(((unsigned int)(B1)) << 8) | \
((unsigned int)(B0))); \
int n = (N); \
while (n-- > 0) \
{ \
*cp++ = b64t[w & 0x3f]; \
w >>= 6; \
} \
} while (0)
b64_from_24bit (result[0], result[21], result[42], 4);
b64_from_24bit (result[22], result[43], result[1], 4);
b64_from_24bit (result[44], result[2], result[23], 4);
b64_from_24bit (result[3], result[24], result[45], 4);
b64_from_24bit (result[25], result[46], result[4], 4);
b64_from_24bit (result[47], result[5], result[26], 4);
b64_from_24bit (result[6], result[27], result[48], 4);
b64_from_24bit (result[28], result[49], result[7], 4);
b64_from_24bit (result[50], result[8], result[29], 4);
b64_from_24bit (result[9], result[30], result[51], 4);
b64_from_24bit (result[31], result[52], result[10], 4);
b64_from_24bit (result[53], result[11], result[32], 4);
b64_from_24bit (result[12], result[33], result[54], 4);
b64_from_24bit (result[34], result[55], result[13], 4);
b64_from_24bit (result[56], result[14], result[35], 4);
b64_from_24bit (result[15], result[36], result[57], 4);
b64_from_24bit (result[37], result[58], result[16], 4);
b64_from_24bit (result[59], result[17], result[38], 4);
b64_from_24bit (result[18], result[39], result[60], 4);
b64_from_24bit (result[40], result[61], result[19], 4);
b64_from_24bit (result[62], result[20], result[41], 4);
b64_from_24bit (0, 0, result[63], 2);
*cp = '\0';
}
void
gensalt_sha512_rn (unsigned long count,
const uint8_t *rbytes, size_t nrbytes,
uint8_t *output, size_t output_size)
{
gensalt_sha_rn ('6', SALT_LEN_MAX, ROUNDS_DEFAULT, ROUNDS_MIN, ROUNDS_MAX,
count, rbytes, nrbytes, output, output_size);
}
#endif