--- /dev/null
+/* 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
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