source: rtems/cpukit/libcrypt/crypt-sha512.c

/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 2011 The FreeBSD Project. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/* Based on:
 * SHA512-based Unix crypt implementation. Released into the Public Domain by
 * Ulrich Drepper <drepper@redhat.com>. */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include <sys/endian.h>
#include <sys/param.h>

#include <errno.h>
#include <limits.h>
#include <sha512.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <crypt.h>

/* 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

char *
crypt_sha512_r(const char *key, const char *salt, struct crypt_data *data)
{
        u_long srounds;
        int n;
        uint8_t alt_result[64], temp_result[64];
        SHA512_CTX ctx, alt_ctx;
        size_t salt_len, key_len, cnt, rounds;
        char *cp, *p_bytes, *s_bytes, *endp;
        const char *num;
        bool rounds_custom;
        char *buffer = &data->buffer[0];
        int buflen = (int)sizeof(data->buffer);

        /* Default number of rounds. */
        rounds = ROUNDS_DEFAULT;
        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) {
                num = salt + sizeof(sha512_rounds_prefix) - 1;
                srounds = strtoul(num, &endp, 10);

                if (*endp == '$') {
                        salt = endp + 1;
                        rounds = MAX(ROUNDS_MIN, MIN(srounds, ROUNDS_MAX));
                        rounds_custom = true;
                }
        }

        salt_len = MIN(strcspn(salt, "$"), SALT_LEN_MAX);
        key_len = strlen(key);

        /* Prepare for the real work. */
        SHA512_Init(&ctx);

        /* Add the key string. */
        SHA512_Update(&ctx, key, key_len);

        /* 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_Update(&ctx, salt, salt_len);

        /* Compute alternate SHA512 sum with input KEY, SALT, and KEY. The
         * final result will be added to the first context. */
        SHA512_Init(&alt_ctx);

        /* Add key. */
        SHA512_Update(&alt_ctx, key, key_len);

        /* Add salt. */
        SHA512_Update(&alt_ctx, salt, salt_len);

        /* Add key again. */
        SHA512_Update(&alt_ctx, key, key_len);

        /* Now get result of this (64 bytes) and add it to the other context. */
        SHA512_Final(alt_result, &alt_ctx);

        /* Add for any character in the key one byte of the alternate sum. */
        for (cnt = key_len; cnt > 64; cnt -= 64)
                SHA512_Update(&ctx, alt_result, 64);
        SHA512_Update(&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)
                        SHA512_Update(&ctx, alt_result, 64);
                else
                        SHA512_Update(&ctx, key, key_len);

        /* Create intermediate result. */
        SHA512_Final(alt_result, &ctx);

        /* Start computation of P byte sequence. */
        SHA512_Init(&alt_ctx);

        /* For every character in the password add the entire password. */
        for (cnt = 0; cnt < key_len; ++cnt)
                SHA512_Update(&alt_ctx, key, key_len);

        /* Finish the digest. */
        SHA512_Final(temp_result, &alt_ctx);

        /* Create byte sequence P. */
        cp = p_bytes = alloca(key_len);
        for (cnt = key_len; cnt >= 64; cnt -= 64) {
                memcpy(cp, temp_result, 64);
                cp += 64;
        }
        memcpy(cp, temp_result, cnt);

        /* Start computation of S byte sequence. */
        SHA512_Init(&alt_ctx);

        /* For every character in the password add the entire password. */
        for (cnt = 0; cnt < 16 + alt_result[0]; ++cnt)
                SHA512_Update(&alt_ctx, salt, salt_len);

        /* Finish the digest. */
        SHA512_Final(temp_result, &alt_ctx);

        /* Create byte sequence S. */
        cp = s_bytes = alloca(salt_len);
        for (cnt = salt_len; cnt >= 64; cnt -= 64) {
                memcpy(cp, temp_result, 64);
                cp += 64;
        }
        memcpy(cp, temp_result, cnt);

        /* Repeatedly run the collected hash value through SHA512 to burn CPU
         * cycles. */
        for (cnt = 0; cnt < rounds; ++cnt) {
                /* New context. */
                SHA512_Init(&ctx);

                /* Add key or last result. */
                if ((cnt & 1) != 0)
                        SHA512_Update(&ctx, p_bytes, key_len);
                else
                        SHA512_Update(&ctx, alt_result, 64);

                /* Add salt for numbers not divisible by 3. */
                if (cnt % 3 != 0)
                        SHA512_Update(&ctx, s_bytes, salt_len);

                /* Add key for numbers not divisible by 7. */
                if (cnt % 7 != 0)
                        SHA512_Update(&ctx, p_bytes, key_len);

                /* Add key or last result. */
                if ((cnt & 1) != 0)
                        SHA512_Update(&ctx, alt_result, 64);
                else
                        SHA512_Update(&ctx, p_bytes, key_len);

                /* Create intermediate result. */
                SHA512_Final(alt_result, &ctx);
        }

        /* Now we can construct the result string. It consists of three
         * parts. */
        cp = stpncpy(buffer, sha512_salt_prefix, MAX(0, buflen));
        buflen -= sizeof(sha512_salt_prefix) - 1;

        if (rounds_custom) {
                n = snprintf(cp, MAX(0, buflen), "%s%zu$",
                         sha512_rounds_prefix, rounds);

                cp += n;
                buflen -= n;
        }

        cp = stpncpy(cp, salt, MIN((size_t)MAX(0, buflen), salt_len));
        buflen -= MIN((size_t)MAX(0, buflen), salt_len);

        if (buflen > 0) {
                *cp++ = '$';
                --buflen;
        }

        b64_from_24bit(alt_result[0], alt_result[21], alt_result[42], 4, &buflen, &cp);
        b64_from_24bit(alt_result[22], alt_result[43], alt_result[1], 4, &buflen, &cp);
        b64_from_24bit(alt_result[44], alt_result[2], alt_result[23], 4, &buflen, &cp);
        b64_from_24bit(alt_result[3], alt_result[24], alt_result[45], 4, &buflen, &cp);
        b64_from_24bit(alt_result[25], alt_result[46], alt_result[4], 4, &buflen, &cp);
        b64_from_24bit(alt_result[47], alt_result[5], alt_result[26], 4, &buflen, &cp);
        b64_from_24bit(alt_result[6], alt_result[27], alt_result[48], 4, &buflen, &cp);
        b64_from_24bit(alt_result[28], alt_result[49], alt_result[7], 4, &buflen, &cp);
        b64_from_24bit(alt_result[50], alt_result[8], alt_result[29], 4, &buflen, &cp);
        b64_from_24bit(alt_result[9], alt_result[30], alt_result[51], 4, &buflen, &cp);
        b64_from_24bit(alt_result[31], alt_result[52], alt_result[10], 4, &buflen, &cp);
        b64_from_24bit(alt_result[53], alt_result[11], alt_result[32], 4, &buflen, &cp);
        b64_from_24bit(alt_result[12], alt_result[33], alt_result[54], 4, &buflen, &cp);
        b64_from_24bit(alt_result[34], alt_result[55], alt_result[13], 4, &buflen, &cp);
        b64_from_24bit(alt_result[56], alt_result[14], alt_result[35], 4, &buflen, &cp);
        b64_from_24bit(alt_result[15], alt_result[36], alt_result[57], 4, &buflen, &cp);
        b64_from_24bit(alt_result[37], alt_result[58], alt_result[16], 4, &buflen, &cp);
        b64_from_24bit(alt_result[59], alt_result[17], alt_result[38], 4, &buflen, &cp);
        b64_from_24bit(alt_result[18], alt_result[39], alt_result[60], 4, &buflen, &cp);
        b64_from_24bit(alt_result[40], alt_result[61], alt_result[19], 4, &buflen, &cp);
        b64_from_24bit(alt_result[62], alt_result[20], alt_result[41], 4, &buflen, &cp);
        b64_from_24bit(0, 0, alt_result[63], 2, &buflen, &cp);

        if (buflen <= 0) {
                errno = ERANGE;
                buffer = NULL;
        }
        else
                *cp = '\0';     /* Terminate the string. */

        /* 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. */
        SHA512_Init(&ctx);
        SHA512_Final(alt_result, &ctx);
        memset(temp_result, '\0', sizeof(temp_result));
        memset(p_bytes, '\0', key_len);
        memset(s_bytes, '\0', salt_len);

        return buffer;
}

struct crypt_format crypt_sha512_format =
    CRYPT_FORMAT_INITIALIZER(crypt_sha512_r, "$6$");