libcrypt: add support for SHA256-CRYPT password hashing

This is based on Ulrich Drepper's implementation in GLIBC, but hacked up to work
in uClibc.  The differences from the GLIBC version are as follows:

- b64_from_24bit() has been converted into a macro
- Usage of GLIBC-isms (such as libc_freeres_ptr) have been removed

It is enabled by the UCLIBC_HAS_SHA256_CRYPT_IMPL configuration symbol.  You must
have UCLIBC_HAS_CRYPT_IMPL enabled as well.

Signed-off-by: William Pitcock <nenolod@dereferenced.org>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

7 files changed, 691 insertions, 0 deletions

diff --git a/extra/Configs/Config.in b/extra/Configs/Config.in
index bbde976d0..d4960fbbf 100644
--- a/extra/Configs/Config.in
+++ b/extra/Configs/Config.in
@@ -1174,6 +1174,13 @@ config UCLIBC_HAS_CRYPT_IMPL
 	help
 	  libcrypt contains crypt(), setkey() and encrypt()
 
+config UCLIBC_HAS_SHA256_CRYPT_IMPL
+	bool "libcrypt SHA256 support"
+	depends on UCLIBC_HAS_CRYPT_IMPL
+	help
+	  This adds support for SHA256 password hashing via the crypt() function.
+	  Say N here if you do not need SHA256 crypt support.
+
 config UCLIBC_HAS_SHA512_CRYPT_IMPL
 	bool "libcrypt SHA512 support"
 	depends on UCLIBC_HAS_CRYPT_IMPL
diff --git a/libcrypt/Makefile.in b/libcrypt/Makefile.in
index 2fceaedb9..94753f4ad 100644
--- a/libcrypt/Makefile.in
+++ b/libcrypt/Makefile.in
@@ -21,6 +21,7 @@ libcrypt_OUT := $(top_builddir)libcrypt
 
 libcrypt_SRC-y :=
 libcrypt_SRC-$(UCLIBC_HAS_CRYPT_IMPL) += crypt.c des.c md5.c
+libcrypt_SRC-$(UCLIBC_HAS_SHA256_CRYPT_IMPL) += sha256.c sha256-crypt.c
 libcrypt_SRC-$(UCLIBC_HAS_SHA512_CRYPT_IMPL) += sha512.c sha512-crypt.c
 libcrypt_SRC-$(UCLIBC_HAS_CRYPT_STUB) += crypt_stub.c
 
diff --git a/libcrypt/crypt.c b/libcrypt/crypt.c
index b5bf9ee0f..188a6a081 100644
--- a/libcrypt/crypt.c
+++ b/libcrypt/crypt.c
@@ -19,6 +19,9 @@ static const struct {
 	const crypt_impl_f crypt_impl;
 } crypt_impl_tab[] = {
 	{ "$1$",        __md5_crypt },
+#ifdef __UCLIBC_HAS_SHA256_CRYPT_IMPL__
+	{ "$5$",        __sha256_crypt },
+#endif
 #ifdef __UCLIBC_HAS_SHA512_CRYPT_IMPL__
 	{ "$6$",        __sha512_crypt },
 #endif
diff --git a/libcrypt/libcrypt.h b/libcrypt/libcrypt.h
index fcad6aed0..67733d17f 100644
--- a/libcrypt/libcrypt.h
+++ b/libcrypt/libcrypt.h
@@ -9,9 +9,11 @@
 #define __LIBCRYPT_H__
 
 extern char *__md5_crypt(const unsigned char *pw, const unsigned char *salt) attribute_hidden;
+extern char *__sha256_crypt(const unsigned char *pw, const unsigned char *salt) attribute_hidden;
 extern char *__sha512_crypt(const unsigned char *pw, const unsigned char *salt) attribute_hidden;
 extern char *__des_crypt(const unsigned char *pw, const unsigned char *salt) attribute_hidden;
 
+extern char *__sha256_crypt_r (const char *key, const char *salt, char *buffer, int buflen) attribute_hidden;
 extern char *__sha512_crypt_r (const char *key, const char *salt, char *buffer, int buflen) attribute_hidden;
 
 /* shut up gcc-4.x signed warnings */
diff --git a/libcrypt/sha256-crypt.c b/libcrypt/sha256-crypt.c
new file mode 100644
index 000000000..44221482f
--- /dev/null
+++ b/libcrypt/sha256-crypt.c
@@ -0,0 +1,326 @@
+/* One way encryption based on SHA256 sum.
+   Copyright (C) 2007, 2009 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"
+#include "libcrypt.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";
+
+#define B64_FROM_24BIT(b2, b1, b0, steps) \
+	{ \
+		int n = (steps); \
+		unsigned int w = ((b2) << 16) | ((b1) << 8) | (b0); \
+		while (n-- > 0 && buflen > 0) \
+		{ \
+			*cp++ = b64t[w & 0x3f]; \
+			--buflen; \
+			w >>= 6; \
+		} \
+	}
+
+char *
+__sha256_crypt_r (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))));
+  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);
+    }
+
+  struct sha256_ctx ctx;
+  struct sha256_ctx alt_ctx;
+
+  /* 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 16
+     characters and it ends at the first `$' character.  */
+  __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;
+    }
+
+  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 (&ctx, '\0', sizeof (ctx));
+  memset (&alt_ctx, '\0', sizeof (alt_ctx));
+
+  memset (temp_result, '\0', sizeof (temp_result));
+  memset (p_bytes, '\0', key_len);
+  memset (s_bytes, '\0', salt_len);
+  if (copied_key != NULL)
+    memset (copied_key, '\0', key_len);
+  if (copied_salt != NULL)
+    memset (copied_salt, '\0', salt_len);
+
+  return buffer;
+}
+
+static char *buffer;
+
+/* This entry point is equivalent to the `crypt' function in Unix
+   libcs.  */
+char *
+__sha256_crypt (const unsigned char *key, const unsigned 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 ((const char *) key, (const char *) salt, buffer, buflen);
+}
diff --git a/libcrypt/sha256.c b/libcrypt/sha256.c
new file mode 100644
index 000000000..e652a6705
--- /dev/null
+++ b/libcrypt/sha256.c
@@ -0,0 +1,294 @@
+/* Functions to compute SHA256 message digest of files or memory blocks.
+   according to the definition of SHA256 in FIPS 180-2.
+   Copyright (C) 2007 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   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.  */
+
+/* Written by Ulrich Drepper <drepper@redhat.com>, 2007.  */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <endian.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+
+#include "sha256.h"
+
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+# ifdef _LIBC
+#  include <byteswap.h>
+#  define SWAP(n) bswap_32 (n)
+# else
+#  define SWAP(n) \
+    (((n) << 24) | (((n) & 0xff00) << 8) | (((n) >> 8) & 0xff00) | ((n) >> 24))
+# endif
+#else
+# define SWAP(n) (n)
+#endif
+
+
+/* This array contains the bytes used to pad the buffer to the next
+   64-byte boundary.  (FIPS 180-2:5.1.1)  */
+static const unsigned char fillbuf[64] = { 0x80, 0 /* , 0, 0, ...  */ };
+
+
+/* Constants for SHA256 from FIPS 180-2:4.2.2.  */
+static const uint32_t K[64] =
+  {
+    0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5,
+    0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
+    0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
+    0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
+    0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc,
+    0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
+    0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7,
+    0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
+    0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
+    0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
+    0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3,
+    0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
+    0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5,
+    0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
+    0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
+    0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
+  };
+
+
+/* Process LEN bytes of BUFFER, accumulating context into CTX.
+   It is assumed that LEN % 64 == 0.  */
+static void
+sha256_process_block (const void *buffer, size_t len, struct sha256_ctx *ctx)
+{
+  const uint32_t *words = buffer;
+  size_t nwords = len / sizeof (uint32_t);
+  uint32_t a = ctx->H[0];
+  uint32_t b = ctx->H[1];
+  uint32_t c = ctx->H[2];
+  uint32_t d = ctx->H[3];
+  uint32_t e = ctx->H[4];
+  uint32_t f = ctx->H[5];
+  uint32_t g = ctx->H[6];
+  uint32_t h = ctx->H[7];
+
+  /* First increment the byte count.  FIPS 180-2 specifies the possible
+     length of the file up to 2^64 bits.  Here we only compute the
+     number of bytes.  Do a double word increment.  */
+  ctx->total[0] += len;
+  if (ctx->total[0] < len)
+    ++ctx->total[1];
+
+  /* Process all bytes in the buffer with 64 bytes in each round of
+     the loop.  */
+  while (nwords > 0)
+    {
+      uint32_t W[64];
+      uint32_t a_save = a;
+      uint32_t b_save = b;
+      uint32_t c_save = c;
+      uint32_t d_save = d;
+      uint32_t e_save = e;
+      uint32_t f_save = f;
+      uint32_t g_save = g;
+      uint32_t h_save = h;
+
+      /* Operators defined in FIPS 180-2:4.1.2.  */
+#define Ch(x, y, z) ((x & y) ^ (~x & z))
+#define Maj(x, y, z) ((x & y) ^ (x & z) ^ (y & z))
+#define S0(x) (CYCLIC (x, 2) ^ CYCLIC (x, 13) ^ CYCLIC (x, 22))
+#define S1(x) (CYCLIC (x, 6) ^ CYCLIC (x, 11) ^ CYCLIC (x, 25))
+#define R0(x) (CYCLIC (x, 7) ^ CYCLIC (x, 18) ^ (x >> 3))
+#define R1(x) (CYCLIC (x, 17) ^ CYCLIC (x, 19) ^ (x >> 10))
+
+      /* It is unfortunate that C does not provide an operator for
+	 cyclic rotation.  Hope the C compiler is smart enough.  */
+#define CYCLIC(w, s) ((w >> s) | (w << (32 - s)))
+
+      /* Compute the message schedule according to FIPS 180-2:6.2.2 step 2.  */
+      for (unsigned int t = 0; t < 16; ++t)
+	{
+	  W[t] = SWAP (*words);
+	  ++words;
+	}
+      for (unsigned int t = 16; t < 64; ++t)
+	W[t] = R1 (W[t - 2]) + W[t - 7] + R0 (W[t - 15]) + W[t - 16];
+
+      /* The actual computation according to FIPS 180-2:6.2.2 step 3.  */
+      for (unsigned int t = 0; t < 64; ++t)
+	{
+	  uint32_t T1 = h + S1 (e) + Ch (e, f, g) + K[t] + W[t];
+	  uint32_t T2 = S0 (a) + Maj (a, b, c);
+	  h = g;
+	  g = f;
+	  f = e;
+	  e = d + T1;
+	  d = c;
+	  c = b;
+	  b = a;
+	  a = T1 + T2;
+	}
+
+      /* Add the starting values of the context according to FIPS 180-2:6.2.2
+	 step 4.  */
+      a += a_save;
+      b += b_save;
+      c += c_save;
+      d += d_save;
+      e += e_save;
+      f += f_save;
+      g += g_save;
+      h += h_save;
+
+      /* Prepare for the next round.  */
+      nwords -= 16;
+    }
+
+  /* Put checksum in context given as argument.  */
+  ctx->H[0] = a;
+  ctx->H[1] = b;
+  ctx->H[2] = c;
+  ctx->H[3] = d;
+  ctx->H[4] = e;
+  ctx->H[5] = f;
+  ctx->H[6] = g;
+  ctx->H[7] = h;
+}
+
+
+/* Initialize structure containing state of computation.
+   (FIPS 180-2:5.3.2)  */
+void
+__sha256_init_ctx (struct sha256_ctx *ctx)
+{
+  ctx->H[0] = 0x6a09e667;
+  ctx->H[1] = 0xbb67ae85;
+  ctx->H[2] = 0x3c6ef372;
+  ctx->H[3] = 0xa54ff53a;
+  ctx->H[4] = 0x510e527f;
+  ctx->H[5] = 0x9b05688c;
+  ctx->H[6] = 0x1f83d9ab;
+  ctx->H[7] = 0x5be0cd19;
+
+  ctx->total[0] = ctx->total[1] = 0;
+  ctx->buflen = 0;
+}
+
+
+/* Process the remaining bytes in the internal buffer and the usual
+   prolog according to the standard and write the result to RESBUF.
+
+   IMPORTANT: On some systems it is required that RESBUF is correctly
+   aligned for a 32 bits value.  */
+void *
+__sha256_finish_ctx (struct sha256_ctx *ctx, void *resbuf)
+{
+  /* Take yet unprocessed bytes into account.  */
+  uint32_t bytes = ctx->buflen;
+  size_t pad;
+
+  /* Now count remaining bytes.  */
+  ctx->total[0] += bytes;
+  if (ctx->total[0] < bytes)
+    ++ctx->total[1];
+
+  pad = bytes >= 56 ? 64 + 56 - bytes : 56 - bytes;
+  memcpy (&ctx->buffer[bytes], fillbuf, pad);
+
+  /* Put the 64-bit file length in *bits* at the end of the buffer.  */
+  *(uint32_t *) &ctx->buffer[bytes + pad + 4] = SWAP (ctx->total[0] << 3);
+  *(uint32_t *) &ctx->buffer[bytes + pad] = SWAP ((ctx->total[1] << 3) |
+						  (ctx->total[0] >> 29));
+
+  /* Process last bytes.  */
+  sha256_process_block (ctx->buffer, bytes + pad + 8, ctx);
+
+  /* Put result from CTX in first 32 bytes following RESBUF.  */
+  for (unsigned int i = 0; i < 8; ++i)
+    ((uint32_t *) resbuf)[i] = SWAP (ctx->H[i]);
+
+  return resbuf;
+}
+
+
+void
+__sha256_process_bytes (const void *buffer, size_t len, struct sha256_ctx *ctx)
+{
+  /* When we already have some bits in our internal buffer concatenate
+     both inputs first.  */
+  if (ctx->buflen != 0)
+    {
+      size_t left_over = ctx->buflen;
+      size_t add = 128 - left_over > len ? len : 128 - left_over;
+
+      memcpy (&ctx->buffer[left_over], buffer, add);
+      ctx->buflen += add;
+
+      if (ctx->buflen > 64)
+	{
+	  sha256_process_block (ctx->buffer, ctx->buflen & ~63, ctx);
+
+	  ctx->buflen &= 63;
+	  /* The regions in the following copy operation cannot overlap.  */
+	  memcpy (ctx->buffer, &ctx->buffer[(left_over + add) & ~63],
+		  ctx->buflen);
+	}
+
+      buffer = (const char *) buffer + add;
+      len -= add;
+    }
+
+  /* Process available complete blocks.  */
+  if (len >= 64)
+    {
+#if __GNUC__ >= 2
+# define UNALIGNED_P(p) (((uintptr_t) p) % __alignof__ (uint32_t) != 0)
+#else
+# define UNALIGNED_P(p) (((uintptr_t) p) % sizeof (uint32_t) != 0)
+#endif
+      if (UNALIGNED_P (buffer))
+	while (len > 64)
+	  {
+	    sha256_process_block (memcpy (ctx->buffer, buffer, 64), 64, ctx);
+	    buffer = (const char *) buffer + 64;
+	    len -= 64;
+	  }
+      else
+	{
+	  sha256_process_block (buffer, len & ~63, ctx);
+	  buffer = (const char *) buffer + (len & ~63);
+	  len &= 63;
+	}
+    }
+
+  /* Move remaining bytes into internal buffer.  */
+  if (len > 0)
+    {
+      size_t left_over = ctx->buflen;
+
+      memcpy (&ctx->buffer[left_over], buffer, len);
+      left_over += len;
+      if (left_over >= 64)
+	{
+	  sha256_process_block (ctx->buffer, 64, ctx);
+	  left_over -= 64;
+	  memcpy (ctx->buffer, &ctx->buffer[64], left_over);
+	}
+      ctx->buflen = left_over;
+    }
+}
diff --git a/libcrypt/sha256.h b/libcrypt/sha256.h
new file mode 100644
index 000000000..291674f35
--- /dev/null
+++ b/libcrypt/sha256.h
@@ -0,0 +1,58 @@
+/* Declaration of functions and data types used for SHA256 sum computing
+   library functions.
+   Copyright (C) 2007 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   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.  */
+
+#ifndef _SHA256_H
+#define _SHA256_H 1
+
+#include <limits.h>
+#include <stdint.h>
+#include <stdio.h>
+
+
+/* Structure to save state of computation between the single steps.  */
+struct sha256_ctx
+{
+  uint32_t H[8];
+
+  uint32_t total[2];
+  uint32_t buflen;
+  char buffer[128] __attribute__ ((__aligned__ (__alignof__ (uint32_t))));
+};
+
+/* Initialize structure containing state of computation.
+   (FIPS 180-2: 5.3.2)  */
+extern void __sha256_init_ctx (struct sha256_ctx *ctx) attribute_hidden;
+
+/* Starting with the result of former calls of this function (or the
+   initialization function update the context for the next LEN bytes
+   starting at BUFFER.
+   It is NOT required that LEN is a multiple of 64.  */
+extern void __sha256_process_bytes (const void *buffer, size_t len,
+				    struct sha256_ctx *ctx) attribute_hidden;
+
+/* Process the remaining bytes in the buffer and put result from CTX
+   in first 32 bytes following RESBUF.
+
+   IMPORTANT: On some systems it is required that RESBUF is correctly
+   aligned for a 32 bits value.  */
+extern void *__sha256_finish_ctx (struct sha256_ctx *ctx, void *resbuf)
+  attribute_hidden;
+
+#endif /* sha256.h */