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| -rw-r--r-- | crypt/sha256-crypt.c | 345 |
1 files changed, 345 insertions, 0 deletions
diff --git a/crypt/sha256-crypt.c b/crypt/sha256-crypt.c new file mode 100644 index 0000000..0db13e4 --- /dev/null +++ b/crypt/sha256-crypt.c @@ -0,0 +1,345 @@ +/* One way encryption based on SHA256 sum. + Copyright (C) 2007 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Ulrich Drepper <drepper@redhat.com>, 2007. + + The GNU C 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. + + The GNU C 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 the GNU C Library; if not, write to the Free + Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA + 02111-1307 USA. */ + +#include <assert.h> +#include <errno.h> +#include <stdbool.h> +#include <stdlib.h> +#include <string.h> +#include <sys/param.h> + +#include "sha256.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 + +/* Table with characters for base64 transformation. */ +static const char b64t[64] = +"./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"; + + +/* Prototypes for local functions. */ +extern char *__sha256_crypt_r (const char *key, const char *salt, + char *buffer, int buflen); +extern char *__sha256_crypt (const char *key, const char *salt); + + +char * +__sha256_crypt_r (key, salt, buffer, buflen) + const char *key; + const char *salt; + char *buffer; + int buflen; +{ + unsigned char alt_result[32] + __attribute__ ((__aligned__ (__alignof__ (uint32_t)))); + unsigned char temp_result[32] + __attribute__ ((__aligned__ (__alignof__ (uint32_t)))); + struct sha256_ctx ctx; + struct sha256_ctx alt_ctx; + size_t salt_len; + size_t key_len; + size_t cnt; + char *cp; + char *copied_key = NULL; + char *copied_salt = NULL; + char *p_bytes; + char *s_bytes; + /* 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; + char *endp; + unsigned long int 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); + + if ((key - (char *) 0) % __alignof__ (uint32_t) != 0) + { + char *tmp = (char *) alloca (key_len + __alignof__ (uint32_t)); + key = copied_key = + memcpy (tmp + __alignof__ (uint32_t) + - (tmp - (char *) 0) % __alignof__ (uint32_t), + key, key_len); + assert ((key - (char *) 0) % __alignof__ (uint32_t) == 0); + } + + if ((salt - (char *) 0) % __alignof__ (uint32_t) != 0) + { + char *tmp = (char *) alloca (salt_len + __alignof__ (uint32_t)); + salt = copied_salt = + memcpy (tmp + __alignof__ (uint32_t) + - (tmp - (char *) 0) % __alignof__ (uint32_t), + salt, salt_len); + assert ((salt - (char *) 0) % __alignof__ (uint32_t) == 0); + } + + /* Prepare for the real work. */ + __sha256_init_ctx (&ctx); + + /* Add the key string. */ + __sha256_process_bytes (key, key_len, &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). */ + __sha256_process_bytes (salt, salt_len, &ctx); + + + /* Compute alternate SHA256 sum with input KEY, SALT, and KEY. The + final result will be added to the first context. */ + __sha256_init_ctx (&alt_ctx); + + /* Add key. */ + __sha256_process_bytes (key, key_len, &alt_ctx); + + /* Add salt. */ + __sha256_process_bytes (salt, salt_len, &alt_ctx); + + /* Add key again. */ + __sha256_process_bytes (key, key_len, &alt_ctx); + + /* Now get result of this (32 bytes) and add it to the other + context. */ + __sha256_finish_ctx (&alt_ctx, alt_result); + + /* Add for any character in the key one byte of the alternate sum. */ + for (cnt = key_len; cnt > 32; cnt -= 32) + __sha256_process_bytes (alt_result, 32, &ctx); + __sha256_process_bytes (alt_result, cnt, &ctx); + + /* 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_process_bytes (alt_result, 32, &ctx); + else + __sha256_process_bytes (key, key_len, &ctx); + + /* Create intermediate result. */ + __sha256_finish_ctx (&ctx, alt_result); + + /* Start computation of P byte sequence. */ + __sha256_init_ctx (&alt_ctx); + + /* For every character in the password add the entire password. */ + for (cnt = 0; cnt < key_len; ++cnt) + __sha256_process_bytes (key, key_len, &alt_ctx); + + /* Finish the digest. */ + __sha256_finish_ctx (&alt_ctx, temp_result); + + /* Create byte sequence P. */ + cp = p_bytes = alloca (key_len); + for (cnt = key_len; cnt >= 32; cnt -= 32) + cp = mempcpy (cp, temp_result, 32); + memcpy (cp, temp_result, cnt); + + /* Start computation of S byte sequence. */ + __sha256_init_ctx (&alt_ctx); + + /* For every character in the password add the entire password. */ + for (cnt = 0; cnt < 16 + alt_result[0]; ++cnt) + __sha256_process_bytes (salt, salt_len, &alt_ctx); + + /* Finish the digest. */ + __sha256_finish_ctx (&alt_ctx, temp_result); + + /* Create byte sequence S. */ + cp = s_bytes = alloca (salt_len); + for (cnt = salt_len; cnt >= 32; cnt -= 32) + cp = mempcpy (cp, temp_result, 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 (&ctx); + + /* Add key or last result. */ + if ((cnt & 1) != 0) + __sha256_process_bytes (p_bytes, key_len, &ctx); + else + __sha256_process_bytes (alt_result, 32, &ctx); + + /* Add salt for numbers not divisible by 3. */ + if (cnt % 3 != 0) + __sha256_process_bytes (s_bytes, salt_len, &ctx); + + /* Add key for numbers not divisible by 7. */ + if (cnt % 7 != 0) + __sha256_process_bytes (p_bytes, key_len, &ctx); + + /* Add key or last result. */ + if ((cnt & 1) != 0) + __sha256_process_bytes (alt_result, 32, &ctx); + else + __sha256_process_bytes (p_bytes, key_len, &ctx); + + /* Create intermediate result. */ + __sha256_finish_ctx (&ctx, alt_result); + } + + /* 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) + { + int 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; + } + +#define b64_from_24bit(B2, B1, B0, N) \ + do { \ + unsigned int w = ((B2) << 16) | ((B1) << 8) | (B0); \ + int n = (N); \ + while (n-- > 0 && buflen > 0) \ + { \ + *cp++ = b64t[w & 0x3f]; \ + --buflen; \ + w >>= 6; \ + } \ + } while (0) + + b64_from_24bit (alt_result[0], alt_result[10], alt_result[20], 4); + b64_from_24bit (alt_result[21], alt_result[1], alt_result[11], 4); + b64_from_24bit (alt_result[12], alt_result[22], alt_result[2], 4); + b64_from_24bit (alt_result[3], alt_result[13], alt_result[23], 4); + b64_from_24bit (alt_result[24], alt_result[4], alt_result[14], 4); + b64_from_24bit (alt_result[15], alt_result[25], alt_result[5], 4); + b64_from_24bit (alt_result[6], alt_result[16], alt_result[26], 4); + b64_from_24bit (alt_result[27], alt_result[7], alt_result[17], 4); + b64_from_24bit (alt_result[18], alt_result[28], alt_result[8], 4); + b64_from_24bit (alt_result[9], alt_result[19], alt_result[29], 4); + b64_from_24bit (0, alt_result[31], alt_result[30], 3); + if (buflen <= 0) + { + __set_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 (&ctx); + __sha256_finish_ctx (&ctx, alt_result); + 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; +} + +#ifndef _LIBC +# define libc_freeres_ptr(decl) decl +#endif +libc_freeres_ptr (static char *buffer); + +/* This entry point is equivalent to the `crypt' function in Unix + libcs. */ +char * +__sha256_crypt (const char *key, const char *salt) +{ + /* We don't want to have an arbitrary limit in the size of the + password. We can compute an upper bound for the size of the + result in advance and so we can prepare the buffer we pass to + `sha256_crypt_r'. */ + static int buflen; + int needed = (sizeof (sha256_salt_prefix) - 1 + + sizeof (sha256_rounds_prefix) + 9 + 1 + + strlen (salt) + 1 + 43 + 1); + + if (buflen < needed) + { + char *new_buffer = (char *) realloc (buffer, needed); + if (new_buffer == NULL) + return NULL; + + buffer = new_buffer; + buflen = needed; + } + + return __sha256_crypt_r (key, salt, buffer, buflen); +} + +#ifndef _LIBC +static void +__attribute__ ((__destructor__)) +free_mem (void) +{ + free (buffer); +} +#endif |