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Diffstat (limited to 'cpukit/libcrypt/crypt-sha256.c')
-rw-r--r-- | cpukit/libcrypt/crypt-sha256.c | 272 |
1 files changed, 272 insertions, 0 deletions
diff --git a/cpukit/libcrypt/crypt-sha256.c b/cpukit/libcrypt/crypt-sha256.c new file mode 100644 index 0000000000..7a677284b5 --- /dev/null +++ b/cpukit/libcrypt/crypt-sha256.c @@ -0,0 +1,272 @@ +/* + * 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: + * SHA256-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 <sha256.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 SHA256 "encryption" replacement. */ +static const char sha256_salt_prefix[] = "$5$"; + +/* Prefix for optional rounds specification. */ +static const char sha256_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_sha256_r(const char *key, const char *salt, struct crypt_data *data) +{ + u_long srounds; + int n; + uint8_t alt_result[32], temp_result[32]; + SHA256_CTX ctx, alt_ctx; + size_t salt_len, key_len, cnt, rounds; + char *cp, *copied_key, *copied_salt, *p_bytes, *s_bytes, *endp; + const char *num; + bool rounds_custom; + char *buffer = &data->buffer[0]; + int buflen = (int)sizeof(data->buffer); + + copied_key = NULL; + copied_salt = NULL; + + /* 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(sha256_salt_prefix, salt, sizeof(sha256_salt_prefix) - 1) == 0) + /* Skip salt prefix. */ + salt += sizeof(sha256_salt_prefix) - 1; + + if (strncmp(salt, sha256_rounds_prefix, sizeof(sha256_rounds_prefix) - 1) + == 0) { + num = salt + sizeof(sha256_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. */ + SHA256_Init(&ctx); + + /* Add the key string. */ + SHA256_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). */ + SHA256_Update(&ctx, salt, salt_len); + + /* Compute alternate SHA256 sum with input KEY, SALT, and KEY. The + * final result will be added to the first context. */ + SHA256_Init(&alt_ctx); + + /* Add key. */ + SHA256_Update(&alt_ctx, key, key_len); + + /* Add salt. */ + SHA256_Update(&alt_ctx, salt, salt_len); + + /* Add key again. */ + SHA256_Update(&alt_ctx, key, key_len); + + /* Now get result of this (32 bytes) and add it to the other context. */ + SHA256_Final(alt_result, &alt_ctx); + + /* Add for any character in the key one byte of the alternate sum. */ + for (cnt = key_len; cnt > 32; cnt -= 32) + SHA256_Update(&ctx, alt_result, 32); + SHA256_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) + SHA256_Update(&ctx, alt_result, 32); + else + SHA256_Update(&ctx, key, key_len); + + /* Create intermediate result. */ + SHA256_Final(alt_result, &ctx); + + /* Start computation of P byte sequence. */ + SHA256_Init(&alt_ctx); + + /* For every character in the password add the entire password. */ + for (cnt = 0; cnt < key_len; ++cnt) + SHA256_Update(&alt_ctx, key, key_len); + + /* Finish the digest. */ + SHA256_Final(temp_result, &alt_ctx); + + /* Create byte sequence P. */ + cp = p_bytes = alloca(key_len); + for (cnt = key_len; cnt >= 32; cnt -= 32) { + memcpy(cp, temp_result, 32); + cp += 32; + } + memcpy(cp, temp_result, cnt); + + /* Start computation of S byte sequence. */ + SHA256_Init(&alt_ctx); + + /* For every character in the password add the entire password. */ + for (cnt = 0; cnt < 16 + alt_result[0]; ++cnt) + SHA256_Update(&alt_ctx, salt, salt_len); + + /* Finish the digest. */ + SHA256_Final(temp_result, &alt_ctx); + + /* Create byte sequence S. */ + cp = s_bytes = alloca(salt_len); + for (cnt = salt_len; cnt >= 32; cnt -= 32) { + memcpy(cp, temp_result, 32); + cp += 32; + } + memcpy(cp, temp_result, cnt); + + /* Repeatedly run the collected hash value through SHA256 to burn CPU + * cycles. */ + for (cnt = 0; cnt < rounds; ++cnt) { + /* New context. */ + SHA256_Init(&ctx); + + /* Add key or last result. */ + if ((cnt & 1) != 0) + SHA256_Update(&ctx, p_bytes, key_len); + else + SHA256_Update(&ctx, alt_result, 32); + + /* Add salt for numbers not divisible by 3. */ + if (cnt % 3 != 0) + SHA256_Update(&ctx, s_bytes, salt_len); + + /* Add key for numbers not divisible by 7. */ + if (cnt % 7 != 0) + SHA256_Update(&ctx, p_bytes, key_len); + + /* Add key or last result. */ + if ((cnt & 1) != 0) + SHA256_Update(&ctx, alt_result, 32); + else + SHA256_Update(&ctx, p_bytes, key_len); + + /* Create intermediate result. */ + SHA256_Final(alt_result, &ctx); + } + + /* Now we can construct the result string. It consists of three + * parts. */ + cp = stpncpy(buffer, sha256_salt_prefix, MAX(0, buflen)); + buflen -= sizeof(sha256_salt_prefix) - 1; + + if (rounds_custom) { + n = snprintf(cp, MAX(0, buflen), "%s%zu$", + sha256_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[10], alt_result[20], 4, &buflen, &cp); + b64_from_24bit(alt_result[21], alt_result[1], alt_result[11], 4, &buflen, &cp); + b64_from_24bit(alt_result[12], alt_result[22], alt_result[2], 4, &buflen, &cp); + b64_from_24bit(alt_result[3], alt_result[13], alt_result[23], 4, &buflen, &cp); + b64_from_24bit(alt_result[24], alt_result[4], alt_result[14], 4, &buflen, &cp); + b64_from_24bit(alt_result[15], alt_result[25], alt_result[5], 4, &buflen, &cp); + b64_from_24bit(alt_result[6], alt_result[16], alt_result[26], 4, &buflen, &cp); + b64_from_24bit(alt_result[27], alt_result[7], alt_result[17], 4, &buflen, &cp); + b64_from_24bit(alt_result[18], alt_result[28], alt_result[8], 4, &buflen, &cp); + b64_from_24bit(alt_result[9], alt_result[19], alt_result[29], 4, &buflen, &cp); + b64_from_24bit(0, alt_result[31], alt_result[30], 3, &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 SHA256 implementation as well. */ + SHA256_Init(&ctx); + SHA256_Final(alt_result, &ctx); + memset(temp_result, '\0', sizeof(temp_result)); + memset(p_bytes, '\0', key_len); + memset(s_bytes, '\0', salt_len); + memset(&ctx, '\0', sizeof(ctx)); + memset(&alt_ctx, '\0', sizeof(alt_ctx)); + if (copied_key != NULL) + memset(copied_key, '\0', key_len); + if (copied_salt != NULL) + memset(copied_salt, '\0', salt_len); + + return buffer; +} + +struct crypt_format crypt_sha256_format = + CRYPT_FORMAT_INITIALIZER(crypt_sha256_r, "$5$"); |