65 lines
1.6 KiB
C
65 lines
1.6 KiB
C
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/*
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* SHA256-based PRF (IEEE 802.11r)
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* Copyright (c) 2003-2007, Jouni Malinen <j@w1.fi>
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*
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* This software may be distributed under the terms of the BSD license.
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* See README for more details.
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*/
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#include "includes.h"
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#include "common.h"
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#include "sha256.h"
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#include "crypto.h"
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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 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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