77 lines
1.7 KiB
C
77 lines
1.7 KiB
C
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/*
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* HMAC-SHA256 KDF (RFC 5295)
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* Copyright (c) 2014, 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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/**
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* hmac_sha256_kdf - HMAC-SHA256 based KDF (RFC 5295)
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* @secret: Key for KDF
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* @secret_len: Length of the key in bytes
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* @label: A unique label for each purpose of the KDF
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* @seed: Seed value to bind into the key
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* @seed_len: Length of the seed
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* @out: Buffer for the generated pseudo-random key
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* @outlen: Number of bytes of key to generate
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* Returns: 0 on success, -1 on failure.
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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 in ERP. This KDF is defined in RFC 5295, Chapter 3.1.2.
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*/
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int hmac_sha256_kdf(const u8 *secret, size_t secret_len,
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const char *label, const u8 *seed, size_t seed_len,
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u8 *out, size_t outlen)
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{
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u8 T[SHA256_MAC_LEN];
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u8 iter = 1;
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const unsigned char *addr[4];
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size_t len[4];
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size_t pos, clen;
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addr[0] = T;
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len[0] = SHA256_MAC_LEN;
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addr[1] = (const unsigned char *) label;
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len[1] = os_strlen(label) + 1;
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addr[2] = seed;
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len[2] = seed_len;
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addr[3] = &iter;
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len[3] = 1;
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if (hmac_sha256_vector(secret, secret_len, 3, &addr[1], &len[1], T) < 0)
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return -1;
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pos = 0;
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for (;;) {
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clen = outlen - pos;
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if (clen > SHA256_MAC_LEN)
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clen = SHA256_MAC_LEN;
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os_memcpy(out + pos, T, clen);
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pos += clen;
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if (pos == outlen)
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break;
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if (iter == 255) {
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os_memset(out, 0, outlen);
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return -1;
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}
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iter++;
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if (hmac_sha256_vector(secret, secret_len, 4, addr, len, T) < 0)
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{
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os_memset(out, 0, outlen);
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return -1;
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}
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}
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return 0;
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}
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