sha256.c

/*
 * SHA-256 hash implementation and interface functions
 * Copyright (c) 2003-2006, Jouni Malinen <j@w1.fi>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Alternatively, this software may be distributed under the terms of BSD
 * license.
 *
 * See README and COPYING for more details.
 */

#include "includes.h"

#include "common.h"
#include "sha256.h"
#include "crypto.h"


/**
 * hmac_sha256_vector - HMAC-SHA256 over data vector (RFC 2104)
 * @key: Key for HMAC operations
 * @key_len: Length of the key in bytes
 * @num_elem: Number of elements in the data vector
 * @addr: Pointers to the data areas
 * @len: Lengths of the data blocks
 * @mac: Buffer for the hash (32 bytes)
 */
void hmac_sha256_vector(const u8 *key, size_t key_len, size_t num_elem,
			const u8 *addr[], const size_t *len, u8 *mac)
{
	unsigned char k_pad[64]; /* padding - key XORd with ipad/opad */
	unsigned char tk[32];
	const u8 *_addr[6];
	size_t _len[6], i;

	if (num_elem > 5) {
		/*
		 * Fixed limit on the number of fragments to avoid having to
		 * allocate memory (which could fail).
		 */
		return;
	}

        /* if key is longer than 64 bytes reset it to key = SHA256(key) */
        if (key_len > 64) {
		sha256_vector(1, &key, &key_len, tk);
		key = tk;
		key_len = 32;
        }

	/* the HMAC_SHA256 transform looks like:
	 *
	 * SHA256(K XOR opad, SHA256(K XOR ipad, text))
	 *
	 * where K is an n byte key
	 * ipad is the byte 0x36 repeated 64 times
	 * opad is the byte 0x5c repeated 64 times
	 * and text is the data being protected */

	/* start out by storing key in ipad */
	memset(k_pad, 0, sizeof(k_pad));
	memcpy(k_pad, key, key_len);
	/* XOR key with ipad values */
	for (i = 0; i < 64; i++)
		k_pad[i] ^= 0x36;

	/* perform inner SHA256 */
	_addr[0] = k_pad;
	_len[0] = 64;
	for (i = 0; i < num_elem; i++) {
		_addr[i + 1] = addr[i];
		_len[i + 1] = len[i];
	}
	sha256_vector(1 + num_elem, _addr, _len, mac);

	memset(k_pad, 0, sizeof(k_pad));
	memcpy(k_pad, key, key_len);
	/* XOR key with opad values */
	for (i = 0; i < 64; i++)
		k_pad[i] ^= 0x5c;

	/* perform outer SHA256 */
	_addr[0] = k_pad;
	_len[0] = 64;
	_addr[1] = mac;
	_len[1] = SHA256_MAC_LEN;
	sha256_vector(2, _addr, _len, mac);
}


/**
 * hmac_sha256 - HMAC-SHA256 over data buffer (RFC 2104)
 * @key: Key for HMAC operations
 * @key_len: Length of the key in bytes
 * @data: Pointers to the data area
 * @data_len: Length of the data area
 * @mac: Buffer for the hash (20 bytes)
 */
void hmac_sha256(const u8 *key, size_t key_len, const u8 *data,
		 size_t data_len, u8 *mac)
{
	hmac_sha256_vector(key, key_len, 1, &data, &data_len, mac);
}


/**
 * sha256_prf - SHA256-based Pseudo-Random Function (IEEE 802.11r, 8.5A.3)
 * @key: Key for PRF
 * @key_len: Length of the key in bytes
 * @label: A unique label for each purpose of the PRF
 * @data: Extra data to bind into the key
 * @data_len: Length of the data
 * @buf: Buffer for the generated pseudo-random key
 * @buf_len: Number of bytes of key to generate
 *
 * This function is used to derive new, cryptographically separate keys from a
 * given key.
 */
void sha256_prf(const u8 *key, size_t key_len, const char *label,
		const u8 *data, size_t data_len, u8 *buf, size_t buf_len)
{
	u16 counter = 0;
	size_t pos, plen;
	u8 hash[SHA256_MAC_LEN];
	const u8 *addr[3];
	size_t len[3];
	u8 counter_le[2];

	addr[0] = counter_le;
	len[0] = 2;
	addr[1] = (u8 *) label;
	len[1] = strlen(label) + 1;
	addr[2] = data;
	len[2] = data_len;

	pos = 0;
	while (pos < buf_len) {
		plen = buf_len - pos;
		WPA_PUT_LE16(counter_le, counter);
		if (plen >= SHA256_MAC_LEN) {
			hmac_sha256_vector(key, key_len, 3, addr, len,
					   &buf[pos]);
			pos += SHA256_MAC_LEN;
		} else {
			hmac_sha256_vector(key, key_len, 3, addr, len, hash);
			memcpy(&buf[pos], hash, plen);
			break;
		}
		counter++;
	}
}


#ifdef INTERNAL_SHA256

struct sha256_state {
	u64 length;
	u32 state[8], curlen;
	u8 buf[64];
};

static void sha256_init(struct sha256_state *md);
static int sha256_process(struct sha256_state *md, const unsigned char *in,
			  unsigned long inlen);
static int sha256_done(struct sha256_state *md, unsigned char *out);


/**
 * sha256_vector - SHA256 hash for data vector
 * @num_elem: Number of elements in the data vector
 * @addr: Pointers to the data areas
 * @len: Lengths of the data blocks
 * @mac: Buffer for the hash
 */
void sha256_vector(size_t num_elem, const u8 *addr[], const size_t *len,
		 u8 *mac)
{
	struct sha256_state ctx;
	size_t i;

	sha256_init(&ctx);
	for (i = 0; i < num_elem; i++)
		sha256_process(&ctx, addr[i], len[i]);
	sha256_done(&ctx, mac);
}


/* ===== start - public domain SHA256 implementation ===== */

/* This is based on SHA256 implementation in LibTomCrypt that was released into
 * public domain by Tom St Denis. */

/* the K array */
static const unsigned long K[64] = {
	0x428a2f98UL, 0x71374491UL, 0xb5c0fbcfUL, 0xe9b5dba5UL, 0x3956c25bUL,
	0x59f111f1UL, 0x923f82a4UL, 0xab1c5ed5UL, 0xd807aa98UL, 0x12835b01UL,
	0x243185beUL, 0x550c7dc3UL, 0x72be5d74UL, 0x80deb1feUL, 0x9bdc06a7UL,
	0xc19bf174UL, 0xe49b69c1UL, 0xefbe4786UL, 0x0fc19dc6UL, 0x240ca1ccUL,
	0x2de92c6fUL, 0x4a7484aaUL, 0x5cb0a9dcUL, 0x76f988daUL, 0x983e5152UL,
	0xa831c66dUL, 0xb00327c8UL, 0xbf597fc7UL, 0xc6e00bf3UL, 0xd5a79147UL,
	0x06ca6351UL, 0x14292967UL, 0x27b70a85UL, 0x2e1b2138UL, 0x4d2c6dfcUL,
	0x53380d13UL, 0x650a7354UL, 0x766a0abbUL, 0x81c2c92eUL, 0x92722c85UL,
	0xa2bfe8a1UL, 0xa81a664bUL, 0xc24b8b70UL, 0xc76c51a3UL, 0xd192e819UL,
	0xd6990624UL, 0xf40e3585UL, 0x106aa070UL, 0x19a4c116UL, 0x1e376c08UL,
	0x2748774cUL, 0x34b0bcb5UL, 0x391c0cb3UL, 0x4ed8aa4aUL, 0x5b9cca4fUL,
	0x682e6ff3UL, 0x748f82eeUL, 0x78a5636fUL, 0x84c87814UL, 0x8cc70208UL,
	0x90befffaUL, 0xa4506cebUL, 0xbef9a3f7UL, 0xc67178f2UL
};


/* Various logical functions */
#define RORc(x, y) \
( ((((unsigned long) (x) & 0xFFFFFFFFUL) >> (unsigned long) ((y) & 31)) | \
   ((unsigned long) (x) << (unsigned long) (32 - ((y) & 31)))) & 0xFFFFFFFFUL)
#define Ch(x,y,z)       (z ^ (x & (y ^ z)))
#define Maj(x,y,z)      (((x | y) & z) | (x & y)) 
#define S(x, n)         RORc((x), (n))
#define R(x, n)         (((x)&0xFFFFFFFFUL)>>(n))
#define Sigma0(x)       (S(x, 2) ^ S(x, 13) ^ S(x, 22))
#define Sigma1(x)       (S(x, 6) ^ S(x, 11) ^ S(x, 25))
#define Gamma0(x)       (S(x, 7) ^ S(x, 18) ^ R(x, 3))
#define Gamma1(x)       (S(x, 17) ^ S(x, 19) ^ R(x, 10))
#ifndef MIN
#define MIN(x, y) (((x) < (y)) ? (x) : (y))
#endif

/* compress 512-bits */
static int sha256_compress(struct sha256_state *md, unsigned char *buf)
{
	u32 S[8], W[64], t0, t1;
	u32 t;
	int i;

	/* copy state into S */
	for (i = 0; i < 8; i++) {
		S[i] = md->state[i];
	}

	/* copy the state into 512-bits into W[0..15] */
	for (i = 0; i < 16; i++)
		W[i] = WPA_GET_BE32(buf + (4 * i));

	/* fill W[16..63] */
	for (i = 16; i < 64; i++) {
		W[i] = Gamma1(W[i - 2]) + W[i - 7] + Gamma0(W[i - 15]) +
			W[i - 16];
	}        

	/* Compress */
#define RND(a,b,c,d,e,f,g,h,i)                          \
	t0 = h + Sigma1(e) + Ch(e, f, g) + K[i] + W[i];	\
	t1 = Sigma0(a) + Maj(a, b, c);			\
	d += t0;					\
	h  = t0 + t1;

	for (i = 0; i < 64; ++i) {
		RND(S[0], S[1], S[2], S[3], S[4], S[5], S[6], S[7], i);
		t = S[7]; S[7] = S[6]; S[6] = S[5]; S[5] = S[4]; 
		S[4] = S[3]; S[3] = S[2]; S[2] = S[1]; S[1] = S[0]; S[0] = t;
	}

	/* feedback */
	for (i = 0; i < 8; i++) {
		md->state[i] = md->state[i] + S[i];
	}
	return 0;
}


/* Initialize the hash state */
static void sha256_init(struct sha256_state *md)
{
	md->curlen = 0;
	md->length = 0;
	md->state[0] = 0x6A09E667UL;
	md->state[1] = 0xBB67AE85UL;
	md->state[2] = 0x3C6EF372UL;
	md->state[3] = 0xA54FF53AUL;
	md->state[4] = 0x510E527FUL;
	md->state[5] = 0x9B05688CUL;
	md->state[6] = 0x1F83D9ABUL;
	md->state[7] = 0x5BE0CD19UL;
}

/**
   Process a block of memory though the hash
   @param md     The hash state
   @param in     The data to hash
   @param inlen  The length of the data (octets)
   @return CRYPT_OK if successful
*/
static int sha256_process(struct sha256_state *md, const unsigned char *in,
			  unsigned long inlen)
{
	unsigned long n;
#define block_size 64

	if (md->curlen > sizeof(md->buf))
		return -1;

	while (inlen > 0) {
		if (md->curlen == 0 && inlen >= block_size) {
			if (sha256_compress(md, (unsigned char *) in) < 0)
				return -1;
			md->length += block_size * 8;
			in += block_size;
			inlen -= block_size;
		} else {
			n = MIN(inlen, (block_size - md->curlen));
			memcpy(md->buf + md->curlen, in, n);
			md->curlen += n;
			in += n;
			inlen -= n;
			if (md->curlen == block_size) {
				if (sha256_compress(md, md->buf) < 0)
					return -1;
				md->length += 8 * block_size;
				md->curlen = 0;
			}
		}
	}

	return 0;
}


/**
   Terminate the hash to get the digest
   @param md  The hash state
   @param out [out] The destination of the hash (32 bytes)
   @return CRYPT_OK if successful
*/
static int sha256_done(struct sha256_state *md, unsigned char *out)
{
	int i;

	if (md->curlen >= sizeof(md->buf))
		return -1;

	/* increase the length of the message */
	md->length += md->curlen * 8;

	/* append the '1' bit */
	md->buf[md->curlen++] = (unsigned char) 0x80;

	/* if the length is currently above 56 bytes we append zeros
	 * then compress.  Then we can fall back to padding zeros and length
	 * encoding like normal.
	 */
	if (md->curlen > 56) {
		while (md->curlen < 64) {
			md->buf[md->curlen++] = (unsigned char) 0;
		}
		sha256_compress(md, md->buf);
		md->curlen = 0;
	}

	/* pad upto 56 bytes of zeroes */
	while (md->curlen < 56) {
		md->buf[md->curlen++] = (unsigned char) 0;
	}

	/* store length */
	WPA_PUT_BE64(md->buf + 56, md->length);
	sha256_compress(md, md->buf);

	/* copy output */
	for (i = 0; i < 8; i++)
		WPA_PUT_BE32(out + (4 * i), md->state[i]);

	return 0;
}

/* ===== end - public domain SHA256 implementation ===== */

#endif /* INTERNAL_SHA256 */