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Diffstat (limited to 'lib/crypt/crypt-sha256.c')
-rw-r--r-- | lib/crypt/crypt-sha256.c | 313 |
1 files changed, 313 insertions, 0 deletions
diff --git a/lib/crypt/crypt-sha256.c b/lib/crypt/crypt-sha256.c new file mode 100644 index 0000000000..37127d41e1 --- /dev/null +++ b/lib/crypt/crypt-sha256.c @@ -0,0 +1,313 @@ +/* One way encryption based on the SHA256-based Unix crypt implementation. + * + * Written by Ulrich Drepper <drepper at redhat.com> in 2007 [1]. + * Modified by Zack Weinberg <zackw at panix.com> in 2017, 2018. + * Composed by Björn Esser <besser82 at fedoraproject.org> in 2018. + * Modified by Björn Esser <besser82 at fedoraproject.org> in 2020. + * Modified by Steffen Jaeckel <jaeckel-floss at eyet-services.de> in 2020. + * To the extent possible under law, the named authors have waived all + * copyright and related or neighboring rights to this work. + * + * See https://creativecommons.org/publicdomain/zero/1.0/ for further + * details. + * + * This file is a modified except from [2], lines 648 up to 909. + * + * [1] https://www.akkadia.org/drepper/sha-crypt.html + * [2] https://www.akkadia.org/drepper/SHA-crypt.txt + */ + +#include "crypt-port.h" +#include "alg-sha256.h" + +#include <errno.h> +#include <stdio.h> +#include <stdlib.h> + +#if INCLUDE_sha256crypt + +/* 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 + +/* The maximum possible length of a SHA256-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 (43 chars). */ + +#define LENGTH_OF_NUMBER(n) (sizeof #n - 1) + +#define SHA256_HASH_LENGTH \ + (sizeof (sha256_salt_prefix) + sizeof (sha256_rounds_prefix) + \ + LENGTH_OF_NUMBER (ROUNDS_MAX) + SALT_LEN_MAX + 1 + 43) + +static_assert (SHA256_HASH_LENGTH <= CRYPT_OUTPUT_SIZE, + "CRYPT_OUTPUT_SIZE is too small for SHA256"); + +/* A sha256_buffer holds all of the sensitive intermediate data. */ +struct sha256_buffer +{ + SHA256_CTX ctx; + uint8_t result[32]; + uint8_t p_bytes[32]; + uint8_t s_bytes[32]; +}; + +static_assert (sizeof (struct sha256_buffer) <= ALG_SPECIFIC_SIZE, + "ALG_SPECIFIC_SIZE is too small for SHA256"); + + +/* Feed CTX with LEN bytes of a virtual byte sequence consisting of + BLOCK repeated over and over indefinitely. */ +static void +SHA256_Update_recycled (SHA256_CTX *ctx, + unsigned char block[32], size_t len) +{ + size_t cnt; + for (cnt = len; cnt >= 32; cnt -= 32) + SHA256_Update (ctx, block, 32); + SHA256_Update (ctx, block, cnt); +} + +void +crypt_sha256crypt_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 < SHA256_HASH_LENGTH + || scr_size < sizeof (struct sha256_buffer)) + { + errno = ERANGE; + return; + } + + struct sha256_buffer *buf = scratch; + SHA256_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 (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) + { + const char *num = salt + sizeof (sha256_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 != '$' + || rounds < ROUNDS_MIN + || rounds > ROUNDS_MAX + || errno) + { + errno = EINVAL; + return; + } + salt = endp + 1; + rounds_custom = true; + } + + /* The salt ends at the next '$' or the end of the string. + Ensure ':' does not appear in the salt (it is used as a separator in /etc/passwd). + Also check for '\n', as in /etc/passwd the whole parameters of the user data must + be on a single line. */ + salt_size = strcspn (salt, "$:\n"); + if (!(salt[salt_size] == '$' || !salt[salt_size])) + { + errno = EINVAL; + return; + } + + /* Ensure we do not use more salt than SALT_LEN_MAX. */ + if (salt_size > SALT_LEN_MAX) + salt_size = SALT_LEN_MAX; + + /* Compute alternate SHA256 sum with input PHRASE, SALT, and PHRASE. The + final result will be added to the first context. */ + SHA256_Init (ctx); + + /* Add phrase. */ + SHA256_Update (ctx, phrase, phr_size); + + /* Add salt. */ + SHA256_Update (ctx, salt, salt_size); + + /* Add phrase again. */ + SHA256_Update (ctx, phrase, phr_size); + + /* Now get result of this (32 bytes). */ + SHA256_Final (result, ctx); + + /* Prepare for the real work. */ + SHA256_Init (ctx); + + /* Add the phrase string. */ + SHA256_Update (ctx, phrase, phr_size); + + /* 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_size); + + /* Add for any character in the phrase one byte of the alternate sum. */ + for (cnt = phr_size; cnt > 32; cnt -= 32) + SHA256_Update (ctx, result, 32); + SHA256_Update (ctx, result, cnt); + + /* 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) + SHA256_Update (ctx, result, 32); + else + SHA256_Update (ctx, phrase, phr_size); + + /* Create intermediate result. */ + SHA256_Final (result, ctx); + + /* Start computation of P byte sequence. */ + SHA256_Init (ctx); + + /* For every character in the password add the entire password. */ + for (cnt = 0; cnt < phr_size; ++cnt) + SHA256_Update (ctx, phrase, phr_size); + + /* Finish the digest. */ + SHA256_Final (p_bytes, ctx); + + /* Start computation of S byte sequence. */ + SHA256_Init (ctx); + + /* For every character in the password add the entire password. */ + for (cnt = 0; cnt < (size_t) 16 + (size_t) result[0]; ++cnt) + SHA256_Update (ctx, salt, salt_size); + + /* Finish the digest. */ + SHA256_Final (s_bytes, ctx); + + /* Repeatedly run the collected hash value through SHA256 to burn + CPU cycles. */ + for (cnt = 0; cnt < rounds; ++cnt) + { + /* New context. */ + SHA256_Init (ctx); + + /* Add phrase or last result. */ + if ((cnt & 1) != 0) + SHA256_Update_recycled (ctx, p_bytes, phr_size); + else + SHA256_Update (ctx, result, 32); + + /* Add salt for numbers not divisible by 3. */ + if (cnt % 3 != 0) + SHA256_Update_recycled (ctx, s_bytes, salt_size); + + /* Add phrase for numbers not divisible by 7. */ + if (cnt % 7 != 0) + SHA256_Update_recycled (ctx, p_bytes, phr_size); + + /* Add phrase or last result. */ + if ((cnt & 1) != 0) + SHA256_Update (ctx, result, 32); + else + SHA256_Update_recycled (ctx, p_bytes, phr_size); + + /* Create intermediate result. */ + SHA256_Final (result, ctx); + } + + /* Now we can construct the result string. It consists of four + parts, one of which is optional. We already know that there + is sufficient space at CP for the longest possible result string. */ + memcpy (cp, sha256_salt_prefix, sizeof (sha256_salt_prefix) - 1); + cp += sizeof (sha256_salt_prefix) - 1; + + if (rounds_custom) + { + int n = snprintf (cp, + SHA256_HASH_LENGTH - (sizeof (sha256_salt_prefix) - 1), + "%s%zu$", sha256_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[10], result[20], 4); + b64_from_24bit (result[21], result[1], result[11], 4); + b64_from_24bit (result[12], result[22], result[2], 4); + b64_from_24bit (result[3], result[13], result[23], 4); + b64_from_24bit (result[24], result[4], result[14], 4); + b64_from_24bit (result[15], result[25], result[5], 4); + b64_from_24bit (result[6], result[16], result[26], 4); + b64_from_24bit (result[27], result[7], result[17], 4); + b64_from_24bit (result[18], result[28], result[8], 4); + b64_from_24bit (result[9], result[19], result[29], 4); + b64_from_24bit (0, result[31], result[30], 3); + + *cp = '\0'; +} + +#ifndef NO_GENSALT + +void +gensalt_sha256crypt_rn (unsigned long count, + const uint8_t *rbytes, size_t nrbytes, + uint8_t *output, size_t output_size) +{ + gensalt_sha_rn ('5', SALT_LEN_MAX, ROUNDS_DEFAULT, ROUNDS_MIN, ROUNDS_MAX, + count, rbytes, nrbytes, output, output_size); +} + +#endif + +#endif |