com32/libutil/sha256crypt.c - platform/external/syslinux - Git at Google

 /* SHA256-based Unix crypt implementation.
    Released into the Public Domain by Ulrich Drepper <[email protected]>.  */

 #include <alloca.h>
 #include <endian.h>
 #include <errno.h>
 #include <limits.h>
 #include <stdint.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <minmax.h>
 #include <sys/types.h>

 #include "xcrypt.h"

 #define MIN(x,y) min(x,y)
 #define MAX(x,y) max(x,y)

 /* 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];		/* NB: always correctly aligned for uint32_t.  */
 };

 #if __BYTE_ORDER == __LITTLE_ENDIAN
 # define SWAP(n) \
     (((n) << 24) | (((n) & 0xff00) << 8) | (((n) >> 8) & 0xff00) | ((n) >> 24))
 #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)
 {
     unsigned int t;
     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 (t = 0; t < 16; ++t) {
 	    W[t] = SWAP(*words);
 	    ++words;
 	}
 	for (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 (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)  */
 static 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.  */
 static void *sha256_finish_ctx(struct sha256_ctx *ctx, void *resbuf)
 {
     unsigned int i;
     /* 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 (i = 0; i < 8; ++i)
 	((uint32_t *) resbuf)[i] = SWAP(ctx->H[i]);

     return resbuf;
 }

 static 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) {
 /* To check alignment gcc has an appropriate operator.  Other
    compilers don't.  */
 #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;
     }
 }

 /* 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 16U
 /* Default number of rounds if not explicitly specified.  */
 #define ROUNDS_DEFAULT 5000UL
 /* Minimum number of rounds.  */
 #define ROUNDS_MIN 1000UL
 /* Maximum number of rounds.  */
 #define ROUNDS_MAX 999999999UL

 /* Table with characters for base64 transformation.  */
 static const char b64t[64] =
     "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";

 static 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))));
     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);
     }

     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);
     }

     /* 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; 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 < (size_t)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) {
 	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;
 }

 /* 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 char *buffer;
     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);
 }

 #ifdef TEST
 static const struct {
     const char *input;
     const char result[32];
 } tests[] = {
     /* Test vectors from FIPS 180-2: appendix B.1.  */
     {
     "abc",
 	    "\xba\x78\x16\xbf\x8f\x01\xcf\xea\x41\x41\x40\xde\x5d\xae\x22\x23"
 	    "\xb0\x03\x61\xa3\x96\x17\x7a\x9c\xb4\x10\xff\x61\xf2\x00\x15\xad"},
 	/* Test vectors from FIPS 180-2: appendix B.2.  */
     {
     "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq",
 	    "\x24\x8d\x6a\x61\xd2\x06\x38\xb8\xe5\xc0\x26\x93\x0c\x3e\x60\x39"
 	    "\xa3\x3c\xe4\x59\x64\xff\x21\x67\xf6\xec\xed\xd4\x19\xdb\x06\xc1"},
 	/* Test vectors from the NESSIE project.  */
     {
     "", "\xe3\xb0\xc4\x42\x98\xfc\x1c\x14\x9a\xfb\xf4\xc8\x99\x6f\xb9\x24"
 	    "\x27\xae\x41\xe4\x64\x9b\x93\x4c\xa4\x95\x99\x1b\x78\x52\xb8\x55"},
     {
     "a", "\xca\x97\x81\x12\xca\x1b\xbd\xca\xfa\xc2\x31\xb3\x9a\x23\xdc\x4d"
 	    "\xa7\x86\xef\xf8\x14\x7c\x4e\x72\xb9\x80\x77\x85\xaf\xee\x48\xbb"},
     {
     "message digest",
 	    "\xf7\x84\x6f\x55\xcf\x23\xe1\x4e\xeb\xea\xb5\xb4\xe1\x55\x0c\xad"
 	    "\x5b\x50\x9e\x33\x48\xfb\xc4\xef\xa3\xa1\x41\x3d\x39\x3c\xb6\x50"},
     {
     "abcdefghijklmnopqrstuvwxyz",
 	    "\x71\xc4\x80\xdf\x93\xd6\xae\x2f\x1e\xfa\xd1\x44\x7c\x66\xc9\x52"
 	    "\x5e\x31\x62\x18\xcf\x51\xfc\x8d\x9e\xd8\x32\xf2\xda\xf1\x8b\x73"},
     {
     "abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq",
 	    "\x24\x8d\x6a\x61\xd2\x06\x38\xb8\xe5\xc0\x26\x93\x0c\x3e\x60\x39"
 	    "\xa3\x3c\xe4\x59\x64\xff\x21\x67\xf6\xec\xed\xd4\x19\xdb\x06\xc1"},
     {
     "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789",
 	    "\xdb\x4b\xfc\xbd\x4d\xa0\xcd\x85\xa6\x0c\x3c\x37\xd3\xfb\xd8\x80"
 	    "\x5c\x77\xf1\x5f\xc6\xb1\xfd\xfe\x61\x4e\xe0\xa7\xc8\xfd\xb4\xc0"},
     {
     "123456789012345678901234567890123456789012345678901234567890"
 	    "12345678901234567890",
 	    "\xf3\x71\xbc\x4a\x31\x1f\x2b\x00\x9e\xef\x95\x2d\xd8\x3c\xa8\x0e"
 	    "\x2b\x60\x02\x6c\x8e\x93\x55\x92\xd0\xf9\xc3\x08\x45\x3c\x81\x3e"}
 };

 #define ntests (sizeof (tests) / sizeof (tests[0]))

 static const struct {
     const char *salt;
     const char *input;
     const char *expected;
 } tests2[] = {
     {
     "$5$saltstring", "Hello world!",
 	    "$5$saltstring$5B8vYYiY.CVt1RlTTf8KbXBH3hsxY/GNooZaBBGWEc5"}, {
     "$5$rounds=10000$saltstringsaltstring", "Hello world!",
 	    "$5$rounds=10000$saltstringsaltst$3xv.VbSHBb41AL9AvLeujZkZRBAwqFMz2."
 	    "opqey6IcA"}, {
     "$5$rounds=5000$toolongsaltstring", "This is just a test",
 	    "$5$rounds=5000$toolongsaltstrin$Un/5jzAHMgOGZ5.mWJpuVolil07guHPvOW8"
 	    "mGRcvxa5"}, {
     "$5$rounds=1400$anotherlongsaltstring",
 	    "a very much longer text to encrypt.  This one even stretches over more"
 	    "than one line.",
 	    "$5$rounds=1400$anotherlongsalts$Rx.j8H.h8HjEDGomFU8bDkXm3XIUnzyxf12"
 	    "oP84Bnq1"}, {
     "$5$rounds=77777$short",
 	    "we have a short salt string but not a short password",
 	    "$5$rounds=77777$short$JiO1O3ZpDAxGJeaDIuqCoEFysAe1mZNJRs3pw0KQRd/"},
     {
     "$5$rounds=123456$asaltof16chars..", "a short string",
 	    "$5$rounds=123456$asaltof16chars..$gP3VQ/6X7UUEW3HkBn2w1/Ptq2jxPyzV/"
 	    "cZKmF/wJvD"}, {
 "$5$rounds=10$roundstoolow", "the minimum number is still observed",
 	    "$5$rounds=1000$roundstoolow$yfvwcWrQ8l/K0DAWyuPMDNHpIVlTQebY9l/gL97"
 	    "2bIC"},};
 #define ntests2 (sizeof (tests2) / sizeof (tests2[0]))

 int main(void)
 {
     struct sha256_ctx ctx;
     char sum[32];
     int result = 0;
     int cnt;

     for (cnt = 0; cnt < (int)ntests; ++cnt) {
 	sha256_init_ctx(&ctx);
 	sha256_process_bytes(tests[cnt].input, strlen(tests[cnt].input), &ctx);
 	sha256_finish_ctx(&ctx, sum);
 	if (memcmp(tests[cnt].result, sum, 32) != 0) {
 	    printf("test %d run %d failed\n", cnt, 1);
 	    result = 1;
 	}

 	sha256_init_ctx(&ctx);
 	for (int i = 0; tests[cnt].input[i] != '\0'; ++i)
 	    sha256_process_bytes(&tests[cnt].input[i], 1, &ctx);
 	sha256_finish_ctx(&ctx, sum);
 	if (memcmp(tests[cnt].result, sum, 32) != 0) {
 	    printf("test %d run %d failed\n", cnt, 2);
 	    result = 1;
 	}
     }

     /* Test vector from FIPS 180-2: appendix B.3.  */
     char buf[1000];
     memset(buf, 'a', sizeof(buf));
     sha256_init_ctx(&ctx);
     for (int i = 0; i < 1000; ++i)
 	sha256_process_bytes(buf, sizeof(buf), &ctx);
     sha256_finish_ctx(&ctx, sum);
     static const char expected[32] =
 	"\xcd\xc7\x6e\x5c\x99\x14\xfb\x92\x81\xa1\xc7\xe2\x84\xd7\x3e\x67"
 	"\xf1\x80\x9a\x48\xa4\x97\x20\x0e\x04\x6d\x39\xcc\xc7\x11\x2c\xd0";
     if (memcmp(expected, sum, 32) != 0) {
 	printf("test %d failed\n", cnt);
 	result = 1;
     }

     for (cnt = 0; cnt < ntests2; ++cnt) {
 	char *cp = sha256_crypt(tests2[cnt].input, tests2[cnt].salt);

 	if (strcmp(cp, tests2[cnt].expected) != 0) {
 	    printf("test %d: expected \"%s\", got \"%s\"\n",
 		   cnt, tests2[cnt].expected, cp);
 	    result = 1;
 	}
     }

     if (result == 0)
 	puts("all tests OK");

     return result;
 }
 #endif
	/* SHA256-based Unix crypt implementation.
	Released into the Public Domain by Ulrich Drepper <[email protected]>. */

	#include <alloca.h>
	#include <endian.h>
	#include <errno.h>
	#include <limits.h>
	#include <stdint.h>
	#include <stdbool.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	#include <minmax.h>
	#include <sys/types.h>

	#include "xcrypt.h"

	#define MIN(x,y) min(x,y)
	#define MAX(x,y) max(x,y)

	/* 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]; /* NB: always correctly aligned for uint32_t. */
	};

	#if __BYTE_ORDER == __LITTLE_ENDIAN
	# define SWAP(n) \
	(((n) << 24) \| (((n) & 0xff00) << 8) \| (((n) >> 8) & 0xff00) \| ((n) >> 24))
	#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)
	{
	unsigned int t;
	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 (t = 0; t < 16; ++t) {
	W[t] = SWAP(*words);
	++words;
	}
	for (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 (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) */
	static 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. */
	static void sha256_finish_ctx(struct sha256_ctx ctx, void *resbuf)
	{
	unsigned int i;
	/* 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 (i = 0; i < 8; ++i)
	((uint32_t *) resbuf)[i] = SWAP(ctx->H[i]);

	return resbuf;
	}

	static 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) {
	/* To check alignment gcc has an appropriate operator. Other
	compilers don't. */
	#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;
	}
	}

	/* 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 16U
	/* Default number of rounds if not explicitly specified. */
	#define ROUNDS_DEFAULT 5000UL
	/* Minimum number of rounds. */
	#define ROUNDS_MIN 1000UL
	/* Maximum number of rounds. */
	#define ROUNDS_MAX 999999999UL

	/* Table with characters for base64 transformation. */
	static const char b64t[64] =
	"./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";

	static 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))));
	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);
	}

	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);
	}

	/* 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; 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 < (size_t)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) {
	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;
	}

	/* 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 char *buffer;
	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);
	}

	#ifdef TEST
	static const struct {
	const char *input;
	const char result[32];
	} tests[] = {
	/* Test vectors from FIPS 180-2: appendix B.1. */
	{
	"abc",
	"\xba\x78\x16\xbf\x8f\x01\xcf\xea\x41\x41\x40\xde\x5d\xae\x22\x23"
	"\xb0\x03\x61\xa3\x96\x17\x7a\x9c\xb4\x10\xff\x61\xf2\x00\x15\xad"},
	/* Test vectors from FIPS 180-2: appendix B.2. */
	{
	"abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq",
	"\x24\x8d\x6a\x61\xd2\x06\x38\xb8\xe5\xc0\x26\x93\x0c\x3e\x60\x39"
	"\xa3\x3c\xe4\x59\x64\xff\x21\x67\xf6\xec\xed\xd4\x19\xdb\x06\xc1"},
	/* Test vectors from the NESSIE project. */
	{
	"", "\xe3\xb0\xc4\x42\x98\xfc\x1c\x14\x9a\xfb\xf4\xc8\x99\x6f\xb9\x24"
	"\x27\xae\x41\xe4\x64\x9b\x93\x4c\xa4\x95\x99\x1b\x78\x52\xb8\x55"},
	{
	"a", "\xca\x97\x81\x12\xca\x1b\xbd\xca\xfa\xc2\x31\xb3\x9a\x23\xdc\x4d"
	"\xa7\x86\xef\xf8\x14\x7c\x4e\x72\xb9\x80\x77\x85\xaf\xee\x48\xbb"},
	{
	"message digest",
	"\xf7\x84\x6f\x55\xcf\x23\xe1\x4e\xeb\xea\xb5\xb4\xe1\x55\x0c\xad"
	"\x5b\x50\x9e\x33\x48\xfb\xc4\xef\xa3\xa1\x41\x3d\x39\x3c\xb6\x50"},
	{
	"abcdefghijklmnopqrstuvwxyz",
	"\x71\xc4\x80\xdf\x93\xd6\xae\x2f\x1e\xfa\xd1\x44\x7c\x66\xc9\x52"
	"\x5e\x31\x62\x18\xcf\x51\xfc\x8d\x9e\xd8\x32\xf2\xda\xf1\x8b\x73"},
	{
	"abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq",
	"\x24\x8d\x6a\x61\xd2\x06\x38\xb8\xe5\xc0\x26\x93\x0c\x3e\x60\x39"
	"\xa3\x3c\xe4\x59\x64\xff\x21\x67\xf6\xec\xed\xd4\x19\xdb\x06\xc1"},
	{
	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789",
	"\xdb\x4b\xfc\xbd\x4d\xa0\xcd\x85\xa6\x0c\x3c\x37\xd3\xfb\xd8\x80"
	"\x5c\x77\xf1\x5f\xc6\xb1\xfd\xfe\x61\x4e\xe0\xa7\xc8\xfd\xb4\xc0"},
	{
	"123456789012345678901234567890123456789012345678901234567890"
	"12345678901234567890",
	"\xf3\x71\xbc\x4a\x31\x1f\x2b\x00\x9e\xef\x95\x2d\xd8\x3c\xa8\x0e"
	"\x2b\x60\x02\x6c\x8e\x93\x55\x92\xd0\xf9\xc3\x08\x45\x3c\x81\x3e"}
	};

	#define ntests (sizeof (tests) / sizeof (tests[0]))

	static const struct {
	const char *salt;
	const char *input;
	const char *expected;
	} tests2[] = {
	{
	"$5$saltstring", "Hello world!",
	"$5$saltstring$5B8vYYiY.CVt1RlTTf8KbXBH3hsxY/GNooZaBBGWEc5"}, {
	"$5$rounds=10000$saltstringsaltstring", "Hello world!",
	"$5$rounds=10000$saltstringsaltst$3xv.VbSHBb41AL9AvLeujZkZRBAwqFMz2."
	"opqey6IcA"}, {
	"$5$rounds=5000$toolongsaltstring", "This is just a test",
	"$5$rounds=5000$toolongsaltstrin$Un/5jzAHMgOGZ5.mWJpuVolil07guHPvOW8"
	"mGRcvxa5"}, {
	"$5$rounds=1400$anotherlongsaltstring",
	"a very much longer text to encrypt. This one even stretches over more"
	"than one line.",
	"$5$rounds=1400$anotherlongsalts$Rx.j8H.h8HjEDGomFU8bDkXm3XIUnzyxf12"
	"oP84Bnq1"}, {
	"$5$rounds=77777$short",
	"we have a short salt string but not a short password",
	"$5$rounds=77777$short$JiO1O3ZpDAxGJeaDIuqCoEFysAe1mZNJRs3pw0KQRd/"},
	{
	"$5$rounds=123456$asaltof16chars..", "a short string",
	"$5$rounds=123456$asaltof16chars..$gP3VQ/6X7UUEW3HkBn2w1/Ptq2jxPyzV/"
	"cZKmF/wJvD"}, {
	"$5$rounds=10$roundstoolow", "the minimum number is still observed",
	"$5$rounds=1000$roundstoolow$yfvwcWrQ8l/K0DAWyuPMDNHpIVlTQebY9l/gL97"
	"2bIC"},};
	#define ntests2 (sizeof (tests2) / sizeof (tests2[0]))

	int main(void)
	{
	struct sha256_ctx ctx;
	char sum[32];
	int result = 0;
	int cnt;

	for (cnt = 0; cnt < (int)ntests; ++cnt) {
	sha256_init_ctx(&ctx);
	sha256_process_bytes(tests[cnt].input, strlen(tests[cnt].input), &ctx);
	sha256_finish_ctx(&ctx, sum);
	if (memcmp(tests[cnt].result, sum, 32) != 0) {
	printf("test %d run %d failed\n", cnt, 1);
	result = 1;
	}

	sha256_init_ctx(&ctx);
	for (int i = 0; tests[cnt].input[i] != '\0'; ++i)
	sha256_process_bytes(&tests[cnt].input[i], 1, &ctx);
	sha256_finish_ctx(&ctx, sum);
	if (memcmp(tests[cnt].result, sum, 32) != 0) {
	printf("test %d run %d failed\n", cnt, 2);
	result = 1;
	}
	}

	/* Test vector from FIPS 180-2: appendix B.3. */
	char buf[1000];
	memset(buf, 'a', sizeof(buf));
	sha256_init_ctx(&ctx);
	for (int i = 0; i < 1000; ++i)
	sha256_process_bytes(buf, sizeof(buf), &ctx);
	sha256_finish_ctx(&ctx, sum);
	static const char expected[32] =
	"\xcd\xc7\x6e\x5c\x99\x14\xfb\x92\x81\xa1\xc7\xe2\x84\xd7\x3e\x67"
	"\xf1\x80\x9a\x48\xa4\x97\x20\x0e\x04\x6d\x39\xcc\xc7\x11\x2c\xd0";
	if (memcmp(expected, sum, 32) != 0) {
	printf("test %d failed\n", cnt);
	result = 1;
	}

	for (cnt = 0; cnt < ntests2; ++cnt) {
	char *cp = sha256_crypt(tests2[cnt].input, tests2[cnt].salt);

	if (strcmp(cp, tests2[cnt].expected) != 0) {
	printf("test %d: expected \"%s\", got \"%s\"\n",
	cnt, tests2[cnt].expected, cp);
	result = 1;
	}
	}

	if (result == 0)
	puts("all tests OK");

	return result;
	}
	#endif