337 lines
11 KiB
C
337 lines
11 KiB
C
// SPDX-License-Identifier: CC0-1.0
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/* Based on libxcrypt v4.4.17-0-g6b110bc */
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/* One way encryption based on the SHA256-based Unix crypt implementation.
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*
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* Written by Ulrich Drepper <drepper at redhat.com> in 2007 [1].
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* Modified by Zack Weinberg <zackw at panix.com> in 2017, 2018.
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* Composed by Björn Esser <besser82 at fedoraproject.org> in 2018.
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* Modified by Björn Esser <besser82 at fedoraproject.org> in 2020.
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* Modified by Steffen Jaeckel <jaeckel-floss at eyet-services.de> in 2021
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* for U-Boot, instead of using the global errno to use a static one
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* inside this file.
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* To the extent possible under law, the named authors have waived all
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* copyright and related or neighboring rights to this work.
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*
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* See https://creativecommons.org/publicdomain/zero/1.0/ for further
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* details.
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*
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* This file is a modified except from [2], lines 648 up to 909.
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*
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* [1] https://www.akkadia.org/drepper/sha-crypt.html
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* [2] https://www.akkadia.org/drepper/SHA-crypt.txt
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*/
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#include "crypt-port.h"
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#include "alg-sha256.h"
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#include <linux/errno.h>
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#include <stdio.h>
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#include <stdlib.h>
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#if INCLUDE_sha256crypt
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/* Define our magic string to mark salt for SHA256 "encryption"
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replacement. */
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static const char sha256_salt_prefix[] = "$5$";
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/* Prefix for optional rounds specification. */
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static const char sha256_rounds_prefix[] = "rounds=";
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/* Maximum salt string length. */
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#define SALT_LEN_MAX 16
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/* Default number of rounds if not explicitly specified. */
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#define ROUNDS_DEFAULT 5000
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/* Minimum number of rounds. */
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#define ROUNDS_MIN 1000
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/* Maximum number of rounds. */
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#define ROUNDS_MAX 999999999
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/* The maximum possible length of a SHA256-hashed password string,
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including the terminating NUL character. Prefix (including its NUL)
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+ rounds tag ("rounds=$" = "rounds=\0") + strlen(ROUNDS_MAX)
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+ salt (up to SALT_LEN_MAX chars) + '$' + hash (43 chars). */
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#define LENGTH_OF_NUMBER(n) (sizeof #n - 1)
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#define SHA256_HASH_LENGTH \
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(sizeof (sha256_salt_prefix) + sizeof (sha256_rounds_prefix) + \
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LENGTH_OF_NUMBER (ROUNDS_MAX) + SALT_LEN_MAX + 1 + 43)
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static_assert (SHA256_HASH_LENGTH <= CRYPT_OUTPUT_SIZE,
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"CRYPT_OUTPUT_SIZE is too small for SHA256");
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/* A sha256_buffer holds all of the sensitive intermediate data. */
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struct sha256_buffer
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{
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SHA256_CTX ctx;
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uint8_t result[32];
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uint8_t p_bytes[32];
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uint8_t s_bytes[32];
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};
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static_assert (sizeof (struct sha256_buffer) <= ALG_SPECIFIC_SIZE,
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"ALG_SPECIFIC_SIZE is too small for SHA256");
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/* Use this instead of including errno.h */
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static int errno;
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void crypt_sha256crypt_rn(const char *phrase, size_t phr_size,
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const char *setting, size_t ARG_UNUSED(set_size),
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uint8_t *output, size_t out_size, void *scratch,
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size_t scr_size);
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int crypt_sha256crypt_rn_wrapped(const char *phrase, size_t phr_size,
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const char *setting, size_t set_size,
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u8 *output, size_t out_size, void *scratch,
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size_t scr_size)
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{
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errno = 0;
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crypt_sha256crypt_rn(phrase, phr_size, setting, set_size, output,
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out_size, scratch, scr_size);
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return -errno;
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}
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/* Feed CTX with LEN bytes of a virtual byte sequence consisting of
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BLOCK repeated over and over indefinitely. */
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static void
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SHA256_Update_recycled (SHA256_CTX *ctx,
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unsigned char block[32], size_t len)
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{
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size_t cnt;
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for (cnt = len; cnt >= 32; cnt -= 32)
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SHA256_Update (ctx, block, 32);
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SHA256_Update (ctx, block, cnt);
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}
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void
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crypt_sha256crypt_rn (const char *phrase, size_t phr_size,
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const char *setting, size_t ARG_UNUSED (set_size),
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uint8_t *output, size_t out_size,
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void *scratch, size_t scr_size)
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{
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/* This shouldn't ever happen, but... */
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if (out_size < SHA256_HASH_LENGTH
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|| scr_size < sizeof (struct sha256_buffer))
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{
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errno = ERANGE;
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return;
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}
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struct sha256_buffer *buf = scratch;
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SHA256_CTX *ctx = &buf->ctx;
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uint8_t *result = buf->result;
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uint8_t *p_bytes = buf->p_bytes;
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uint8_t *s_bytes = buf->s_bytes;
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char *cp = (char *)output;
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const char *salt = setting;
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size_t salt_size;
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size_t cnt;
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/* Default number of rounds. */
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size_t rounds = ROUNDS_DEFAULT;
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bool rounds_custom = false;
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/* Find beginning of salt string. The prefix should normally always
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be present. Just in case it is not. */
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if (strncmp (sha256_salt_prefix, salt, sizeof (sha256_salt_prefix) - 1) == 0)
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/* Skip salt prefix. */
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salt += sizeof (sha256_salt_prefix) - 1;
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if (strncmp (salt, sha256_rounds_prefix, sizeof (sha256_rounds_prefix) - 1)
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== 0)
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{
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const char *num = salt + sizeof (sha256_rounds_prefix) - 1;
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/* Do not allow an explicit setting of zero rounds, nor of the
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default number of rounds, nor leading zeroes on the rounds. */
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if (!(*num >= '1' && *num <= '9'))
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{
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errno = EINVAL;
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return;
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}
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errno = 0;
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char *endp;
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rounds = strtoul (num, &endp, 10);
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if (endp == num || *endp != '$'
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|| rounds < ROUNDS_MIN
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|| rounds > ROUNDS_MAX
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|| errno)
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{
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errno = EINVAL;
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return;
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}
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salt = endp + 1;
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rounds_custom = true;
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}
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/* The salt ends at the next '$' or the end of the string.
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Ensure ':' does not appear in the salt (it is used as a separator in /etc/passwd).
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Also check for '\n', as in /etc/passwd the whole parameters of the user data must
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be on a single line. */
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salt_size = strcspn (salt, "$:\n");
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if (!(salt[salt_size] == '$' || !salt[salt_size]))
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{
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errno = EINVAL;
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return;
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}
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/* Ensure we do not use more salt than SALT_LEN_MAX. */
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if (salt_size > SALT_LEN_MAX)
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salt_size = SALT_LEN_MAX;
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/* Compute alternate SHA256 sum with input PHRASE, SALT, and PHRASE. The
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final result will be added to the first context. */
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SHA256_Init (ctx);
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/* Add phrase. */
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SHA256_Update (ctx, phrase, phr_size);
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/* Add salt. */
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SHA256_Update (ctx, salt, salt_size);
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/* Add phrase again. */
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SHA256_Update (ctx, phrase, phr_size);
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/* Now get result of this (32 bytes). */
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SHA256_Final (result, ctx);
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/* Prepare for the real work. */
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SHA256_Init (ctx);
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/* Add the phrase string. */
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SHA256_Update (ctx, phrase, phr_size);
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/* The last part is the salt string. This must be at most 8
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characters and it ends at the first `$' character (for
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compatibility with existing implementations). */
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SHA256_Update (ctx, salt, salt_size);
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/* Add for any character in the phrase one byte of the alternate sum. */
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for (cnt = phr_size; cnt > 32; cnt -= 32)
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SHA256_Update (ctx, result, 32);
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SHA256_Update (ctx, result, cnt);
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/* Take the binary representation of the length of the phrase and for every
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1 add the alternate sum, for every 0 the phrase. */
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for (cnt = phr_size; cnt > 0; cnt >>= 1)
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if ((cnt & 1) != 0)
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SHA256_Update (ctx, result, 32);
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else
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SHA256_Update (ctx, phrase, phr_size);
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/* Create intermediate result. */
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SHA256_Final (result, ctx);
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/* Start computation of P byte sequence. */
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SHA256_Init (ctx);
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/* For every character in the password add the entire password. */
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for (cnt = 0; cnt < phr_size; ++cnt)
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SHA256_Update (ctx, phrase, phr_size);
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/* Finish the digest. */
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SHA256_Final (p_bytes, ctx);
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/* Start computation of S byte sequence. */
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SHA256_Init (ctx);
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/* For every character in the password add the entire password. */
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for (cnt = 0; cnt < (size_t) 16 + (size_t) result[0]; ++cnt)
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SHA256_Update (ctx, salt, salt_size);
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/* Finish the digest. */
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SHA256_Final (s_bytes, ctx);
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/* Repeatedly run the collected hash value through SHA256 to burn
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CPU cycles. */
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for (cnt = 0; cnt < rounds; ++cnt)
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{
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/* New context. */
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SHA256_Init (ctx);
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/* Add phrase or last result. */
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if ((cnt & 1) != 0)
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SHA256_Update_recycled (ctx, p_bytes, phr_size);
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else
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SHA256_Update (ctx, result, 32);
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/* Add salt for numbers not divisible by 3. */
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if (cnt % 3 != 0)
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SHA256_Update_recycled (ctx, s_bytes, salt_size);
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/* Add phrase for numbers not divisible by 7. */
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if (cnt % 7 != 0)
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SHA256_Update_recycled (ctx, p_bytes, phr_size);
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/* Add phrase or last result. */
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if ((cnt & 1) != 0)
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SHA256_Update (ctx, result, 32);
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else
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SHA256_Update_recycled (ctx, p_bytes, phr_size);
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/* Create intermediate result. */
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SHA256_Final (result, ctx);
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}
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/* Now we can construct the result string. It consists of four
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parts, one of which is optional. We already know that there
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is sufficient space at CP for the longest possible result string. */
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memcpy (cp, sha256_salt_prefix, sizeof (sha256_salt_prefix) - 1);
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cp += sizeof (sha256_salt_prefix) - 1;
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if (rounds_custom)
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{
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int n = snprintf (cp,
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SHA256_HASH_LENGTH - (sizeof (sha256_salt_prefix) - 1),
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"%s%zu$", sha256_rounds_prefix, rounds);
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cp += n;
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}
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memcpy (cp, salt, salt_size);
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cp += salt_size;
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*cp++ = '$';
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#define b64_from_24bit(B2, B1, B0, N) \
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do { \
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unsigned int w = ((((unsigned int)(B2)) << 16) | \
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(((unsigned int)(B1)) << 8) | \
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((unsigned int)(B0))); \
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int n = (N); \
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while (n-- > 0) \
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{ \
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*cp++ = b64t[w & 0x3f]; \
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w >>= 6; \
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} \
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} while (0)
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b64_from_24bit (result[0], result[10], result[20], 4);
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b64_from_24bit (result[21], result[1], result[11], 4);
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b64_from_24bit (result[12], result[22], result[2], 4);
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b64_from_24bit (result[3], result[13], result[23], 4);
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b64_from_24bit (result[24], result[4], result[14], 4);
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b64_from_24bit (result[15], result[25], result[5], 4);
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b64_from_24bit (result[6], result[16], result[26], 4);
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b64_from_24bit (result[27], result[7], result[17], 4);
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b64_from_24bit (result[18], result[28], result[8], 4);
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b64_from_24bit (result[9], result[19], result[29], 4);
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b64_from_24bit (0, result[31], result[30], 3);
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*cp = '\0';
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}
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#ifndef NO_GENSALT
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void
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gensalt_sha256crypt_rn (unsigned long count,
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const uint8_t *rbytes, size_t nrbytes,
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uint8_t *output, size_t output_size)
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{
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gensalt_sha_rn ('5', SALT_LEN_MAX, ROUNDS_DEFAULT, ROUNDS_MIN, ROUNDS_MAX,
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count, rbytes, nrbytes, output, output_size);
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}
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#endif
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#endif
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