src/third_party/musl/src/crypt/crypt_sha512.c - cobalt - Git at Google

 /*
  * public domain sha512 crypt implementation
  *
  * original sha crypt design: http://people.redhat.com/drepper/SHA-crypt.txt
  * in this implementation at least 32bit int is assumed,
  * key length is limited, the $6$ prefix is mandatory, '\n' and ':' is rejected
  * in the salt and rounds= setting must contain a valid iteration count,
  * on error "*" is returned.
  */
 #include <ctype.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
 #include <stdint.h>

 /* public domain sha512 implementation based on fips180-3 */
 /* >=2^64 bits messages are not supported (about 2000 peta bytes) */

 struct sha512 {
 	uint64_t len;     /* processed message length */
 	uint64_t h[8];    /* hash state */
 	uint8_t buf[128]; /* message block buffer */
 };

 static uint64_t ror(uint64_t n, int k) { return (n >> k) | (n << (64-k)); }
 #define Ch(x,y,z)  (z ^ (x & (y ^ z)))
 #define Maj(x,y,z) ((x & y) | (z & (x | y)))
 #define S0(x)      (ror(x,28) ^ ror(x,34) ^ ror(x,39))
 #define S1(x)      (ror(x,14) ^ ror(x,18) ^ ror(x,41))
 #define R0(x)      (ror(x,1) ^ ror(x,8) ^ (x>>7))
 #define R1(x)      (ror(x,19) ^ ror(x,61) ^ (x>>6))

 static const uint64_t K[80] = {
 0x428a2f98d728ae22ULL, 0x7137449123ef65cdULL, 0xb5c0fbcfec4d3b2fULL, 0xe9b5dba58189dbbcULL,
 0x3956c25bf348b538ULL, 0x59f111f1b605d019ULL, 0x923f82a4af194f9bULL, 0xab1c5ed5da6d8118ULL,
 0xd807aa98a3030242ULL, 0x12835b0145706fbeULL, 0x243185be4ee4b28cULL, 0x550c7dc3d5ffb4e2ULL,
 0x72be5d74f27b896fULL, 0x80deb1fe3b1696b1ULL, 0x9bdc06a725c71235ULL, 0xc19bf174cf692694ULL,
 0xe49b69c19ef14ad2ULL, 0xefbe4786384f25e3ULL, 0x0fc19dc68b8cd5b5ULL, 0x240ca1cc77ac9c65ULL,
 0x2de92c6f592b0275ULL, 0x4a7484aa6ea6e483ULL, 0x5cb0a9dcbd41fbd4ULL, 0x76f988da831153b5ULL,
 0x983e5152ee66dfabULL, 0xa831c66d2db43210ULL, 0xb00327c898fb213fULL, 0xbf597fc7beef0ee4ULL,
 0xc6e00bf33da88fc2ULL, 0xd5a79147930aa725ULL, 0x06ca6351e003826fULL, 0x142929670a0e6e70ULL,
 0x27b70a8546d22ffcULL, 0x2e1b21385c26c926ULL, 0x4d2c6dfc5ac42aedULL, 0x53380d139d95b3dfULL,
 0x650a73548baf63deULL, 0x766a0abb3c77b2a8ULL, 0x81c2c92e47edaee6ULL, 0x92722c851482353bULL,
 0xa2bfe8a14cf10364ULL, 0xa81a664bbc423001ULL, 0xc24b8b70d0f89791ULL, 0xc76c51a30654be30ULL,
 0xd192e819d6ef5218ULL, 0xd69906245565a910ULL, 0xf40e35855771202aULL, 0x106aa07032bbd1b8ULL,
 0x19a4c116b8d2d0c8ULL, 0x1e376c085141ab53ULL, 0x2748774cdf8eeb99ULL, 0x34b0bcb5e19b48a8ULL,
 0x391c0cb3c5c95a63ULL, 0x4ed8aa4ae3418acbULL, 0x5b9cca4f7763e373ULL, 0x682e6ff3d6b2b8a3ULL,
 0x748f82ee5defb2fcULL, 0x78a5636f43172f60ULL, 0x84c87814a1f0ab72ULL, 0x8cc702081a6439ecULL,
 0x90befffa23631e28ULL, 0xa4506cebde82bde9ULL, 0xbef9a3f7b2c67915ULL, 0xc67178f2e372532bULL,
 0xca273eceea26619cULL, 0xd186b8c721c0c207ULL, 0xeada7dd6cde0eb1eULL, 0xf57d4f7fee6ed178ULL,
 0x06f067aa72176fbaULL, 0x0a637dc5a2c898a6ULL, 0x113f9804bef90daeULL, 0x1b710b35131c471bULL,
 0x28db77f523047d84ULL, 0x32caab7b40c72493ULL, 0x3c9ebe0a15c9bebcULL, 0x431d67c49c100d4cULL,
 0x4cc5d4becb3e42b6ULL, 0x597f299cfc657e2aULL, 0x5fcb6fab3ad6faecULL, 0x6c44198c4a475817ULL
 };

 static void processblock(struct sha512 *s, const uint8_t *buf)
 {
 	uint64_t W[80], t1, t2, a, b, c, d, e, f, g, h;
 	int i;

 	for (i = 0; i < 16; i++) {
 		W[i] = (uint64_t)buf[8*i]<<56;
 		W[i] |= (uint64_t)buf[8*i+1]<<48;
 		W[i] |= (uint64_t)buf[8*i+2]<<40;
 		W[i] |= (uint64_t)buf[8*i+3]<<32;
 		W[i] |= (uint64_t)buf[8*i+4]<<24;
 		W[i] |= (uint64_t)buf[8*i+5]<<16;
 		W[i] |= (uint64_t)buf[8*i+6]<<8;
 		W[i] |= buf[8*i+7];
 	}
 	for (; i < 80; i++)
 		W[i] = R1(W[i-2]) + W[i-7] + R0(W[i-15]) + W[i-16];
 	a = s->h[0];
 	b = s->h[1];
 	c = s->h[2];
 	d = s->h[3];
 	e = s->h[4];
 	f = s->h[5];
 	g = s->h[6];
 	h = s->h[7];
 	for (i = 0; i < 80; i++) {
 		t1 = h + S1(e) + Ch(e,f,g) + K[i] + W[i];
 		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;
 	}
 	s->h[0] += a;
 	s->h[1] += b;
 	s->h[2] += c;
 	s->h[3] += d;
 	s->h[4] += e;
 	s->h[5] += f;
 	s->h[6] += g;
 	s->h[7] += h;
 }

 static void pad(struct sha512 *s)
 {
 	unsigned r = s->len % 128;

 	s->buf[r++] = 0x80;
 	if (r > 112) {
 		memset(s->buf + r, 0, 128 - r);
 		r = 0;
 		processblock(s, s->buf);
 	}
 	memset(s->buf + r, 0, 120 - r);
 	s->len *= 8;
 	s->buf[120] = s->len >> 56;
 	s->buf[121] = s->len >> 48;
 	s->buf[122] = s->len >> 40;
 	s->buf[123] = s->len >> 32;
 	s->buf[124] = s->len >> 24;
 	s->buf[125] = s->len >> 16;
 	s->buf[126] = s->len >> 8;
 	s->buf[127] = s->len;
 	processblock(s, s->buf);
 }

 static void sha512_init(struct sha512 *s)
 {
 	s->len = 0;
 	s->h[0] = 0x6a09e667f3bcc908ULL;
 	s->h[1] = 0xbb67ae8584caa73bULL;
 	s->h[2] = 0x3c6ef372fe94f82bULL;
 	s->h[3] = 0xa54ff53a5f1d36f1ULL;
 	s->h[4] = 0x510e527fade682d1ULL;
 	s->h[5] = 0x9b05688c2b3e6c1fULL;
 	s->h[6] = 0x1f83d9abfb41bd6bULL;
 	s->h[7] = 0x5be0cd19137e2179ULL;
 }

 static void sha512_sum(struct sha512 *s, uint8_t *md)
 {
 	int i;

 	pad(s);
 	for (i = 0; i < 8; i++) {
 		md[8*i] = s->h[i] >> 56;
 		md[8*i+1] = s->h[i] >> 48;
 		md[8*i+2] = s->h[i] >> 40;
 		md[8*i+3] = s->h[i] >> 32;
 		md[8*i+4] = s->h[i] >> 24;
 		md[8*i+5] = s->h[i] >> 16;
 		md[8*i+6] = s->h[i] >> 8;
 		md[8*i+7] = s->h[i];
 	}
 }

 static void sha512_update(struct sha512 *s, const void *m, unsigned long len)
 {
 	const uint8_t *p = m;
 	unsigned r = s->len % 128;

 	s->len += len;
 	if (r) {
 		if (len < 128 - r) {
 			memcpy(s->buf + r, p, len);
 			return;
 		}
 		memcpy(s->buf + r, p, 128 - r);
 		len -= 128 - r;
 		p += 128 - r;
 		processblock(s, s->buf);
 	}
 	for (; len >= 128; len -= 128, p += 128)
 		processblock(s, p);
 	memcpy(s->buf, p, len);
 }

 static const unsigned char b64[] =
 "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";

 static char *to64(char *s, unsigned int u, int n)
 {
 	while (--n >= 0) {
 		*s++ = b64[u % 64];
 		u /= 64;
 	}
 	return s;
 }

 /* key limit is not part of the original design, added for DoS protection.
  * rounds limit has been lowered (versus the reference/spec), also for DoS
  * protection. runtime is O(klen^2 + klen*rounds) */
 #define KEY_MAX 256
 #define SALT_MAX 16
 #define ROUNDS_DEFAULT 5000
 #define ROUNDS_MIN 1000
 #define ROUNDS_MAX 9999999

 /* hash n bytes of the repeated md message digest */
 static void hashmd(struct sha512 *s, unsigned int n, const void *md)
 {
 	unsigned int i;

 	for (i = n; i > 64; i -= 64)
 		sha512_update(s, md, 64);
 	sha512_update(s, md, i);
 }

 static char *sha512crypt(const char *key, const char *setting, char *output)
 {
 	struct sha512 ctx;
 	unsigned char md[64], kmd[64], smd[64];
 	unsigned int i, r, klen, slen;
 	char rounds[20] = "";
 	const char *salt;
 	char *p;

 	/* reject large keys */
 	for (i = 0; i <= KEY_MAX && key[i]; i++);
 	if (i > KEY_MAX)
 		return 0;
 	klen = i;

 	/* setting: $6$rounds=n$salt$ (rounds=n$ and closing $ are optional) */
 	if (strncmp(setting, "$6$", 3) != 0)
 		return 0;
 	salt = setting + 3;

 	r = ROUNDS_DEFAULT;
 	if (strncmp(salt, "rounds=", sizeof "rounds=" - 1) == 0) {
 		unsigned long u;
 		char *end;

 		/*
 		 * this is a deviation from the reference:
 		 * bad rounds setting is rejected if it is
 		 * - empty
 		 * - unterminated (missing '$')
 		 * - begins with anything but a decimal digit
 		 * the reference implementation treats these bad
 		 * rounds as part of the salt or parse them with
 		 * strtoul semantics which may cause problems
 		 * including non-portable hashes that depend on
 		 * the host's value of ULONG_MAX.
 		 */
 		salt += sizeof "rounds=" - 1;
 		if (!isdigit(*salt))
 			return 0;
 		u = strtoul(salt, &end, 10);
 		if (*end != '$')
 			return 0;
 		salt = end+1;
 		if (u < ROUNDS_MIN)
 			r = ROUNDS_MIN;
 		else if (u > ROUNDS_MAX)
 			return 0;
 		else
 			r = u;
 		/* needed when rounds is zero prefixed or out of bounds */
 		sprintf(rounds, "rounds=%u$", r);
 	}

 	for (i = 0; i < SALT_MAX && salt[i] && salt[i] != '$'; i++)
 		/* reject characters that interfere with /etc/shadow parsing */
 		if (salt[i] == '\n' || salt[i] == ':')
 			return 0;
 	slen = i;

 	/* B = sha(key salt key) */
 	sha512_init(&ctx);
 	sha512_update(&ctx, key, klen);
 	sha512_update(&ctx, salt, slen);
 	sha512_update(&ctx, key, klen);
 	sha512_sum(&ctx, md);

 	/* A = sha(key salt repeat-B alternate-B-key) */
 	sha512_init(&ctx);
 	sha512_update(&ctx, key, klen);
 	sha512_update(&ctx, salt, slen);
 	hashmd(&ctx, klen, md);
 	for (i = klen; i > 0; i >>= 1)
 		if (i & 1)
 			sha512_update(&ctx, md, sizeof md);
 		else
 			sha512_update(&ctx, key, klen);
 	sha512_sum(&ctx, md);

 	/* DP = sha(repeat-key), this step takes O(klen^2) time */
 	sha512_init(&ctx);
 	for (i = 0; i < klen; i++)
 		sha512_update(&ctx, key, klen);
 	sha512_sum(&ctx, kmd);

 	/* DS = sha(repeat-salt) */
 	sha512_init(&ctx);
 	for (i = 0; i < 16 + md[0]; i++)
 		sha512_update(&ctx, salt, slen);
 	sha512_sum(&ctx, smd);

 	/* iterate A = f(A,DP,DS), this step takes O(rounds*klen) time */
 	for (i = 0; i < r; i++) {
 		sha512_init(&ctx);
 		if (i % 2)
 			hashmd(&ctx, klen, kmd);
 		else
 			sha512_update(&ctx, md, sizeof md);
 		if (i % 3)
 			sha512_update(&ctx, smd, slen);
 		if (i % 7)
 			hashmd(&ctx, klen, kmd);
 		if (i % 2)
 			sha512_update(&ctx, md, sizeof md);
 		else
 			hashmd(&ctx, klen, kmd);
 		sha512_sum(&ctx, md);
 	}

 	/* output is $6$rounds=n$salt$hash */
 	p = output;
 	p += sprintf(p, "$6$%s%.*s$", rounds, slen, salt);
 #if 1
 	static const unsigned char perm[][3] = {
 		0,21,42,22,43,1,44,2,23,3,24,45,25,46,4,
 		47,5,26,6,27,48,28,49,7,50,8,29,9,30,51,
 		31,52,10,53,11,32,12,33,54,34,55,13,56,14,35,
 		15,36,57,37,58,16,59,17,38,18,39,60,40,61,19,
 		62,20,41 };
 	for (i=0; i<21; i++) p = to64(p,
 		(md[perm[i][0]]<<16)|(md[perm[i][1]]<<8)|md[perm[i][2]], 4);
 #else
 	p = to64(p, (md[0]<<16)|(md[21]<<8)|md[42], 4);
 	p = to64(p, (md[22]<<16)|(md[43]<<8)|md[1], 4);
 	p = to64(p, (md[44]<<16)|(md[2]<<8)|md[23], 4);
 	p = to64(p, (md[3]<<16)|(md[24]<<8)|md[45], 4);
 	p = to64(p, (md[25]<<16)|(md[46]<<8)|md[4], 4);
 	p = to64(p, (md[47]<<16)|(md[5]<<8)|md[26], 4);
 	p = to64(p, (md[6]<<16)|(md[27]<<8)|md[48], 4);
 	p = to64(p, (md[28]<<16)|(md[49]<<8)|md[7], 4);
 	p = to64(p, (md[50]<<16)|(md[8]<<8)|md[29], 4);
 	p = to64(p, (md[9]<<16)|(md[30]<<8)|md[51], 4);
 	p = to64(p, (md[31]<<16)|(md[52]<<8)|md[10], 4);
 	p = to64(p, (md[53]<<16)|(md[11]<<8)|md[32], 4);
 	p = to64(p, (md[12]<<16)|(md[33]<<8)|md[54], 4);
 	p = to64(p, (md[34]<<16)|(md[55]<<8)|md[13], 4);
 	p = to64(p, (md[56]<<16)|(md[14]<<8)|md[35], 4);
 	p = to64(p, (md[15]<<16)|(md[36]<<8)|md[57], 4);
 	p = to64(p, (md[37]<<16)|(md[58]<<8)|md[16], 4);
 	p = to64(p, (md[59]<<16)|(md[17]<<8)|md[38], 4);
 	p = to64(p, (md[18]<<16)|(md[39]<<8)|md[60], 4);
 	p = to64(p, (md[40]<<16)|(md[61]<<8)|md[19], 4);
 	p = to64(p, (md[62]<<16)|(md[20]<<8)|md[41], 4);
 #endif
 	p = to64(p, md[63], 2);
 	*p = 0;
 	return output;
 }

 char *__crypt_sha512(const char *key, const char *setting, char *output)
 {
 	static const char testkey[] = "Xy01@#\x01\x02\x80\x7f\xff\r\n\x81\t !";
 	static const char testsetting[] = "$6$rounds=1234$abc0123456789$";
 	static const char testhash[] = "$6$rounds=1234$abc0123456789$BCpt8zLrc/RcyuXmCDOE1ALqMXB2MH6n1g891HhFj8.w7LxGv.FTkqq6Vxc/km3Y0jE0j24jY5PIv/oOu6reg1";
 	char testbuf[128];
 	char *p, *q;

 	p = sha512crypt(key, setting, output);
 	/* self test and stack cleanup */
 	q = sha512crypt(testkey, testsetting, testbuf);
 	if (!p || q != testbuf || memcmp(testbuf, testhash, sizeof testhash))
 		return "*";
 	return p;
 }
	/*
	* public domain sha512 crypt implementation
	*
	* original sha crypt design: http://people.redhat.com/drepper/SHA-crypt.txt
	* in this implementation at least 32bit int is assumed,
	* key length is limited, the $6$ prefix is mandatory, '\n' and ':' is rejected
	* in the salt and rounds= setting must contain a valid iteration count,
	* on error "*" is returned.
	*/
	#include <ctype.h>
	#include <stdlib.h>
	#include <stdio.h>
	#include <string.h>
	#include <stdint.h>

	/* public domain sha512 implementation based on fips180-3 */
	/* >=2^64 bits messages are not supported (about 2000 peta bytes) */

	struct sha512 {
	uint64_t len; /* processed message length */
	uint64_t h[8]; /* hash state */
	uint8_t buf[128]; /* message block buffer */
	};

	static uint64_t ror(uint64_t n, int k) { return (n >> k) \| (n << (64-k)); }
	#define Ch(x,y,z) (z ^ (x & (y ^ z)))
	#define Maj(x,y,z) ((x & y) \| (z & (x \| y)))
	#define S0(x) (ror(x,28) ^ ror(x,34) ^ ror(x,39))
	#define S1(x) (ror(x,14) ^ ror(x,18) ^ ror(x,41))
	#define R0(x) (ror(x,1) ^ ror(x,8) ^ (x>>7))
	#define R1(x) (ror(x,19) ^ ror(x,61) ^ (x>>6))

	static const uint64_t K[80] = {
	0x428a2f98d728ae22ULL, 0x7137449123ef65cdULL, 0xb5c0fbcfec4d3b2fULL, 0xe9b5dba58189dbbcULL,
	0x3956c25bf348b538ULL, 0x59f111f1b605d019ULL, 0x923f82a4af194f9bULL, 0xab1c5ed5da6d8118ULL,
	0xd807aa98a3030242ULL, 0x12835b0145706fbeULL, 0x243185be4ee4b28cULL, 0x550c7dc3d5ffb4e2ULL,
	0x72be5d74f27b896fULL, 0x80deb1fe3b1696b1ULL, 0x9bdc06a725c71235ULL, 0xc19bf174cf692694ULL,
	0xe49b69c19ef14ad2ULL, 0xefbe4786384f25e3ULL, 0x0fc19dc68b8cd5b5ULL, 0x240ca1cc77ac9c65ULL,
	0x2de92c6f592b0275ULL, 0x4a7484aa6ea6e483ULL, 0x5cb0a9dcbd41fbd4ULL, 0x76f988da831153b5ULL,
	0x983e5152ee66dfabULL, 0xa831c66d2db43210ULL, 0xb00327c898fb213fULL, 0xbf597fc7beef0ee4ULL,
	0xc6e00bf33da88fc2ULL, 0xd5a79147930aa725ULL, 0x06ca6351e003826fULL, 0x142929670a0e6e70ULL,
	0x27b70a8546d22ffcULL, 0x2e1b21385c26c926ULL, 0x4d2c6dfc5ac42aedULL, 0x53380d139d95b3dfULL,
	0x650a73548baf63deULL, 0x766a0abb3c77b2a8ULL, 0x81c2c92e47edaee6ULL, 0x92722c851482353bULL,
	0xa2bfe8a14cf10364ULL, 0xa81a664bbc423001ULL, 0xc24b8b70d0f89791ULL, 0xc76c51a30654be30ULL,
	0xd192e819d6ef5218ULL, 0xd69906245565a910ULL, 0xf40e35855771202aULL, 0x106aa07032bbd1b8ULL,
	0x19a4c116b8d2d0c8ULL, 0x1e376c085141ab53ULL, 0x2748774cdf8eeb99ULL, 0x34b0bcb5e19b48a8ULL,
	0x391c0cb3c5c95a63ULL, 0x4ed8aa4ae3418acbULL, 0x5b9cca4f7763e373ULL, 0x682e6ff3d6b2b8a3ULL,
	0x748f82ee5defb2fcULL, 0x78a5636f43172f60ULL, 0x84c87814a1f0ab72ULL, 0x8cc702081a6439ecULL,
	0x90befffa23631e28ULL, 0xa4506cebde82bde9ULL, 0xbef9a3f7b2c67915ULL, 0xc67178f2e372532bULL,
	0xca273eceea26619cULL, 0xd186b8c721c0c207ULL, 0xeada7dd6cde0eb1eULL, 0xf57d4f7fee6ed178ULL,
	0x06f067aa72176fbaULL, 0x0a637dc5a2c898a6ULL, 0x113f9804bef90daeULL, 0x1b710b35131c471bULL,
	0x28db77f523047d84ULL, 0x32caab7b40c72493ULL, 0x3c9ebe0a15c9bebcULL, 0x431d67c49c100d4cULL,
	0x4cc5d4becb3e42b6ULL, 0x597f299cfc657e2aULL, 0x5fcb6fab3ad6faecULL, 0x6c44198c4a475817ULL
	};

	static void processblock(struct sha512 s, const uint8_t buf)
	{
	uint64_t W[80], t1, t2, a, b, c, d, e, f, g, h;
	int i;

	for (i = 0; i < 16; i++) {
	W[i] = (uint64_t)buf[8*i]<<56;
	W[i] \|= (uint64_t)buf[8*i+1]<<48;
	W[i] \|= (uint64_t)buf[8*i+2]<<40;
	W[i] \|= (uint64_t)buf[8*i+3]<<32;
	W[i] \|= (uint64_t)buf[8*i+4]<<24;
	W[i] \|= (uint64_t)buf[8*i+5]<<16;
	W[i] \|= (uint64_t)buf[8*i+6]<<8;
	W[i] \|= buf[8*i+7];
	}
	for (; i < 80; i++)
	W[i] = R1(W[i-2]) + W[i-7] + R0(W[i-15]) + W[i-16];
	a = s->h[0];
	b = s->h[1];
	c = s->h[2];
	d = s->h[3];
	e = s->h[4];
	f = s->h[5];
	g = s->h[6];
	h = s->h[7];
	for (i = 0; i < 80; i++) {
	t1 = h + S1(e) + Ch(e,f,g) + K[i] + W[i];
	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;
	}
	s->h[0] += a;
	s->h[1] += b;
	s->h[2] += c;
	s->h[3] += d;
	s->h[4] += e;
	s->h[5] += f;
	s->h[6] += g;
	s->h[7] += h;
	}

	static void pad(struct sha512 *s)
	{
	unsigned r = s->len % 128;

	s->buf[r++] = 0x80;
	if (r > 112) {
	memset(s->buf + r, 0, 128 - r);
	r = 0;
	processblock(s, s->buf);
	}
	memset(s->buf + r, 0, 120 - r);
	s->len *= 8;
	s->buf[120] = s->len >> 56;
	s->buf[121] = s->len >> 48;
	s->buf[122] = s->len >> 40;
	s->buf[123] = s->len >> 32;
	s->buf[124] = s->len >> 24;
	s->buf[125] = s->len >> 16;
	s->buf[126] = s->len >> 8;
	s->buf[127] = s->len;
	processblock(s, s->buf);
	}

	static void sha512_init(struct sha512 *s)
	{
	s->len = 0;
	s->h[0] = 0x6a09e667f3bcc908ULL;
	s->h[1] = 0xbb67ae8584caa73bULL;
	s->h[2] = 0x3c6ef372fe94f82bULL;
	s->h[3] = 0xa54ff53a5f1d36f1ULL;
	s->h[4] = 0x510e527fade682d1ULL;
	s->h[5] = 0x9b05688c2b3e6c1fULL;
	s->h[6] = 0x1f83d9abfb41bd6bULL;
	s->h[7] = 0x5be0cd19137e2179ULL;
	}

	static void sha512_sum(struct sha512 s, uint8_t md)
	{
	int i;

	pad(s);
	for (i = 0; i < 8; i++) {
	md[8*i] = s->h[i] >> 56;
	md[8*i+1] = s->h[i] >> 48;
	md[8*i+2] = s->h[i] >> 40;
	md[8*i+3] = s->h[i] >> 32;
	md[8*i+4] = s->h[i] >> 24;
	md[8*i+5] = s->h[i] >> 16;
	md[8*i+6] = s->h[i] >> 8;
	md[8*i+7] = s->h[i];
	}
	}

	static void sha512_update(struct sha512 s, const void m, unsigned long len)
	{
	const uint8_t *p = m;
	unsigned r = s->len % 128;

	s->len += len;
	if (r) {
	if (len < 128 - r) {
	memcpy(s->buf + r, p, len);
	return;
	}
	memcpy(s->buf + r, p, 128 - r);
	len -= 128 - r;
	p += 128 - r;
	processblock(s, s->buf);
	}
	for (; len >= 128; len -= 128, p += 128)
	processblock(s, p);
	memcpy(s->buf, p, len);
	}

	static const unsigned char b64[] =
	"./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";

	static char to64(char s, unsigned int u, int n)
	{
	while (--n >= 0) {
	*s++ = b64[u % 64];
	u /= 64;
	}
	return s;
	}

	/* key limit is not part of the original design, added for DoS protection.
	* rounds limit has been lowered (versus the reference/spec), also for DoS
	* protection. runtime is O(klen^2 + klenrounds) /
	#define KEY_MAX 256
	#define SALT_MAX 16
	#define ROUNDS_DEFAULT 5000
	#define ROUNDS_MIN 1000
	#define ROUNDS_MAX 9999999

	/* hash n bytes of the repeated md message digest */
	static void hashmd(struct sha512 s, unsigned int n, const void md)
	{
	unsigned int i;

	for (i = n; i > 64; i -= 64)
	sha512_update(s, md, 64);
	sha512_update(s, md, i);
	}

	static char sha512crypt(const char key, const char setting, char output)
	{
	struct sha512 ctx;
	unsigned char md[64], kmd[64], smd[64];
	unsigned int i, r, klen, slen;
	char rounds[20] = "";
	const char *salt;
	char *p;

	/* reject large keys */
	for (i = 0; i <= KEY_MAX && key[i]; i++);
	if (i > KEY_MAX)
	return 0;
	klen = i;

	/* setting: $6$rounds=n$salt$ (rounds=n$ and closing $ are optional) */
	if (strncmp(setting, "$6$", 3) != 0)
	return 0;
	salt = setting + 3;

	r = ROUNDS_DEFAULT;
	if (strncmp(salt, "rounds=", sizeof "rounds=" - 1) == 0) {
	unsigned long u;
	char *end;

	/*
	* this is a deviation from the reference:
	* bad rounds setting is rejected if it is
	* - empty
	* - unterminated (missing '$')
	* - begins with anything but a decimal digit
	* the reference implementation treats these bad
	* rounds as part of the salt or parse them with
	* strtoul semantics which may cause problems
	* including non-portable hashes that depend on
	* the host's value of ULONG_MAX.
	*/
	salt += sizeof "rounds=" - 1;
	if (!isdigit(*salt))
	return 0;
	u = strtoul(salt, &end, 10);
	if (*end != '$')
	return 0;
	salt = end+1;
	if (u < ROUNDS_MIN)
	r = ROUNDS_MIN;
	else if (u > ROUNDS_MAX)
	return 0;
	else
	r = u;
	/* needed when rounds is zero prefixed or out of bounds */
	sprintf(rounds, "rounds=%u$", r);
	}

	for (i = 0; i < SALT_MAX && salt[i] && salt[i] != '$'; i++)
	/* reject characters that interfere with /etc/shadow parsing */
	if (salt[i] == '\n' \|\| salt[i] == ':')
	return 0;
	slen = i;

	/* B = sha(key salt key) */
	sha512_init(&ctx);
	sha512_update(&ctx, key, klen);
	sha512_update(&ctx, salt, slen);
	sha512_update(&ctx, key, klen);
	sha512_sum(&ctx, md);

	/* A = sha(key salt repeat-B alternate-B-key) */
	sha512_init(&ctx);
	sha512_update(&ctx, key, klen);
	sha512_update(&ctx, salt, slen);
	hashmd(&ctx, klen, md);
	for (i = klen; i > 0; i >>= 1)
	if (i & 1)
	sha512_update(&ctx, md, sizeof md);
	else
	sha512_update(&ctx, key, klen);
	sha512_sum(&ctx, md);

	/* DP = sha(repeat-key), this step takes O(klen^2) time */
	sha512_init(&ctx);
	for (i = 0; i < klen; i++)
	sha512_update(&ctx, key, klen);
	sha512_sum(&ctx, kmd);

	/* DS = sha(repeat-salt) */
	sha512_init(&ctx);
	for (i = 0; i < 16 + md[0]; i++)
	sha512_update(&ctx, salt, slen);
	sha512_sum(&ctx, smd);

	/* iterate A = f(A,DP,DS), this step takes O(roundsklen) time /
	for (i = 0; i < r; i++) {
	sha512_init(&ctx);
	if (i % 2)
	hashmd(&ctx, klen, kmd);
	else
	sha512_update(&ctx, md, sizeof md);
	if (i % 3)
	sha512_update(&ctx, smd, slen);
	if (i % 7)
	hashmd(&ctx, klen, kmd);
	if (i % 2)
	sha512_update(&ctx, md, sizeof md);
	else
	hashmd(&ctx, klen, kmd);
	sha512_sum(&ctx, md);
	}

	/* output is $6$rounds=n$salt$hash */
	p = output;
	p += sprintf(p, "$6$%s%.*s$", rounds, slen, salt);
	#if 1
	static const unsigned char perm[][3] = {
	0,21,42,22,43,1,44,2,23,3,24,45,25,46,4,
	47,5,26,6,27,48,28,49,7,50,8,29,9,30,51,
	31,52,10,53,11,32,12,33,54,34,55,13,56,14,35,
	15,36,57,37,58,16,59,17,38,18,39,60,40,61,19,
	62,20,41 };
	for (i=0; i<21; i++) p = to64(p,
	(md[perm[i][0]]<<16)\|(md[perm[i][1]]<<8)\|md[perm[i][2]], 4);
	#else
	p = to64(p, (md[0]<<16)\|(md[21]<<8)\|md[42], 4);
	p = to64(p, (md[22]<<16)\|(md[43]<<8)\|md[1], 4);
	p = to64(p, (md[44]<<16)\|(md[2]<<8)\|md[23], 4);
	p = to64(p, (md[3]<<16)\|(md[24]<<8)\|md[45], 4);
	p = to64(p, (md[25]<<16)\|(md[46]<<8)\|md[4], 4);
	p = to64(p, (md[47]<<16)\|(md[5]<<8)\|md[26], 4);
	p = to64(p, (md[6]<<16)\|(md[27]<<8)\|md[48], 4);
	p = to64(p, (md[28]<<16)\|(md[49]<<8)\|md[7], 4);
	p = to64(p, (md[50]<<16)\|(md[8]<<8)\|md[29], 4);
	p = to64(p, (md[9]<<16)\|(md[30]<<8)\|md[51], 4);
	p = to64(p, (md[31]<<16)\|(md[52]<<8)\|md[10], 4);
	p = to64(p, (md[53]<<16)\|(md[11]<<8)\|md[32], 4);
	p = to64(p, (md[12]<<16)\|(md[33]<<8)\|md[54], 4);
	p = to64(p, (md[34]<<16)\|(md[55]<<8)\|md[13], 4);
	p = to64(p, (md[56]<<16)\|(md[14]<<8)\|md[35], 4);
	p = to64(p, (md[15]<<16)\|(md[36]<<8)\|md[57], 4);
	p = to64(p, (md[37]<<16)\|(md[58]<<8)\|md[16], 4);
	p = to64(p, (md[59]<<16)\|(md[17]<<8)\|md[38], 4);
	p = to64(p, (md[18]<<16)\|(md[39]<<8)\|md[60], 4);
	p = to64(p, (md[40]<<16)\|(md[61]<<8)\|md[19], 4);
	p = to64(p, (md[62]<<16)\|(md[20]<<8)\|md[41], 4);
	#endif
	p = to64(p, md[63], 2);
	*p = 0;
	return output;
	}

	char __crypt_sha512(const char key, const char setting, char output)
	{
	static const char testkey[] = "Xy01@#\x01\x02\x80\x7f\xff\r\n\x81\t !";
	static const char testsetting[] = "$6$rounds=1234$abc0123456789$";
	static const char testhash[] = "$6$rounds=1234$abc0123456789$BCpt8zLrc/RcyuXmCDOE1ALqMXB2MH6n1g891HhFj8.w7LxGv.FTkqq6Vxc/km3Y0jE0j24jY5PIv/oOu6reg1";
	char testbuf[128];
	char p, q;

	p = sha512crypt(key, setting, output);
	/* self test and stack cleanup */
	q = sha512crypt(testkey, testsetting, testbuf);
	if (!p \|\| q != testbuf \|\| memcmp(testbuf, testhash, sizeof testhash))
	return "*";
	return p;
	}