/* * SHA-256 hash implementation and interface functions * Copyright (c) 2003-2007, Jouni Malinen * * 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 "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 */ os_memset(k_pad, 0, sizeof(k_pad)); os_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); os_memset(k_pad, 0, sizeof(k_pad)); os_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, 8.5.1.5.2) * @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 = 1; size_t pos, plen; u8 hash[SHA256_MAC_LEN]; const u8 *addr[4]; size_t len[4]; u8 counter_le[2], length_le[2]; addr[0] = counter_le; len[0] = 2; addr[1] = (u8 *) label; len[1] = os_strlen(label); addr[2] = data; len[2] = data_len; addr[3] = length_le; len[3] = sizeof(length_le); WPA_PUT_LE16(length_le, buf_len * 8); 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, 4, addr, len, &buf[pos]); pos += SHA256_MAC_LEN; } else { hmac_sha256_vector(key, key_len, 4, addr, len, hash); os_memcpy(&buf[pos], hash, plen); break; } counter++; } }