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+/*
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+ * SHA1 T-PRF for EAP-FAST
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+ * Copyright (c) 2003-2005, 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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+
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+#include "includes.h"
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+
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+#include "common.h"
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+#include "sha1.h"
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+#include "crypto.h"
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+
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+/**
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+ * sha1_t_prf - EAP-FAST Pseudo-Random Function (T-PRF)
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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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+ * @seed: Seed value to bind into the key
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+ * @seed_len: Length of the seed
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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 for EAP-FAST. T-PRF is defined in RFC 4851, Section 5.5.
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+ */
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+void sha1_t_prf(const u8 *key, size_t key_len, const char *label,
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+ const u8 *seed, size_t seed_len, u8 *buf, size_t buf_len)
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+{
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+ unsigned char counter = 0;
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+ size_t pos, plen;
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+ u8 hash[SHA1_MAC_LEN];
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+ size_t label_len = os_strlen(label);
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+ u8 output_len[2];
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+ const unsigned char *addr[5];
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+ size_t len[5];
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+
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+ addr[0] = hash;
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+ len[0] = 0;
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+ addr[1] = (unsigned char *) label;
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+ len[1] = label_len + 1;
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+ addr[2] = seed;
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+ len[2] = seed_len;
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+ addr[3] = output_len;
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+ len[3] = 2;
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+ addr[4] = &counter;
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+ len[4] = 1;
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+
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+ output_len[0] = (buf_len >> 8) & 0xff;
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+ output_len[1] = buf_len & 0xff;
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+ pos = 0;
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+ while (pos < buf_len) {
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+ counter++;
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+ plen = buf_len - pos;
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+ hmac_sha1_vector(key, key_len, 5, addr, len, hash);
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+ if (plen >= SHA1_MAC_LEN) {
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+ os_memcpy(&buf[pos], hash, SHA1_MAC_LEN);
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+ pos += SHA1_MAC_LEN;
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+ } else {
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+ os_memcpy(&buf[pos], hash, plen);
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+ break;
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+ }
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+ len[0] = SHA1_MAC_LEN;
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+ }
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+}
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