160 lines
4 KiB
C
160 lines
4 KiB
C
/*
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* SHA-256 hash implementation and interface functions
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* Copyright (c) 2003-2007, Jouni Malinen <j@w1.fi>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* Alternatively, this software may be distributed under the terms of BSD
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* license.
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*
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* See README and COPYING for more details.
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*/
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#include "crypto/includes.h"
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#include "crypto/common.h"
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#include "crypto/sha256.h"
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#include "crypto/crypto.h"
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/**
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* hmac_sha256_vector - HMAC-SHA256 over data vector (RFC 2104)
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* @key: Key for HMAC operations
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* @key_len: Length of the key in bytes
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* @num_elem: Number of elements in the data vector
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* @addr: Pointers to the data areas
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* @len: Lengths of the data blocks
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* @mac: Buffer for the hash (32 bytes)
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*/
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void
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hmac_sha256_vector(const u8 *key, size_t key_len, size_t num_elem,
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const u8 *addr[], const size_t *len, u8 *mac)
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{
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unsigned char k_pad[64]; /* padding - key XORd with ipad/opad */
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unsigned char tk[32];
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const u8 *_addr[6];
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size_t _len[6], i;
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if (num_elem > 5) {
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/*
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* Fixed limit on the number of fragments to avoid having to
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* allocate memory (which could fail).
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*/
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return;
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}
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/* if key is longer than 64 bytes reset it to key = SHA256(key) */
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if (key_len > 64) {
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sha256_vector(1, &key, &key_len, tk);
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key = tk;
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key_len = 32;
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}
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/* the HMAC_SHA256 transform looks like:
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*
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* SHA256(K XOR opad, SHA256(K XOR ipad, text))
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*
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* where K is an n byte key
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* ipad is the byte 0x36 repeated 64 times
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* opad is the byte 0x5c repeated 64 times
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* and text is the data being protected */
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/* start out by storing key in ipad */
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os_memset(k_pad, 0, sizeof(k_pad));
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os_memcpy(k_pad, key, key_len);
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/* XOR key with ipad values */
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for (i = 0; i < 64; i++)
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k_pad[i] ^= 0x36;
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/* perform inner SHA256 */
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_addr[0] = k_pad;
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_len[0] = 64;
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for (i = 0; i < num_elem; i++) {
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_addr[i + 1] = addr[i];
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_len[i + 1] = len[i];
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}
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sha256_vector(1 + num_elem, _addr, _len, mac);
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os_memset(k_pad, 0, sizeof(k_pad));
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os_memcpy(k_pad, key, key_len);
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/* XOR key with opad values */
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for (i = 0; i < 64; i++)
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k_pad[i] ^= 0x5c;
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/* perform outer SHA256 */
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_addr[0] = k_pad;
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_len[0] = 64;
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_addr[1] = mac;
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_len[1] = SHA256_MAC_LEN;
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sha256_vector(2, _addr, _len, mac);
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}
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/**
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* hmac_sha256 - HMAC-SHA256 over data buffer (RFC 2104)
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* @key: Key for HMAC operations
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* @key_len: Length of the key in bytes
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* @data: Pointers to the data area
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* @data_len: Length of the data area
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* @mac: Buffer for the hash (20 bytes)
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*/
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void
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hmac_sha256(const u8 *key, size_t key_len, const u8 *data,
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size_t data_len, u8 *mac)
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{
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hmac_sha256_vector(key, key_len, 1, &data, &data_len, mac);
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}
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/**
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* sha256_prf - SHA256-based Pseudo-Random Function (IEEE 802.11r, 8.5.1.5.2)
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* @key: Key for PRF
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* @key_len: Length of the key in bytes
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* @label: A unique label for each purpose of the PRF
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* @data: Extra data to bind into the key
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* @data_len: Length of the data
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* @buf: Buffer for the generated pseudo-random key
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* @buf_len: Number of bytes of key to generate
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*
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* This function is used to derive new, cryptographically separate keys from a
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* given key.
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*/
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void
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sha256_prf(const u8 *key, size_t key_len, const char *label,
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const u8 *data, size_t data_len, u8 *buf, size_t buf_len)
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{
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u16 counter = 1;
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size_t pos, plen;
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u8 hash[SHA256_MAC_LEN];
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const u8 *addr[4];
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size_t len[4];
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u8 counter_le[2], length_le[2];
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addr[0] = counter_le;
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len[0] = 2;
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addr[1] = (u8 *) label;
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len[1] = os_strlen(label);
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addr[2] = data;
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len[2] = data_len;
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addr[3] = length_le;
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len[3] = sizeof(length_le);
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WPA_PUT_LE16(length_le, buf_len * 8);
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pos = 0;
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while (pos < buf_len) {
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plen = buf_len - pos;
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WPA_PUT_LE16(counter_le, counter);
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if (plen >= SHA256_MAC_LEN) {
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hmac_sha256_vector(key, key_len, 4, addr, len,
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&buf[pos]);
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pos += SHA256_MAC_LEN;
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} else {
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hmac_sha256_vector(key, key_len, 4, addr, len, hash);
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os_memcpy(&buf[pos], hash, plen);
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break;
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}
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counter++;
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}
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}
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