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+/*
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+ * SHA1-based key derivation function (PBKDF2) for IEEE 802.11i
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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 "md5.h"
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+#include "crypto.h"
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+
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+static void pbkdf2_sha1_f(const char *passphrase, const char *ssid,
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+ size_t ssid_len, int iterations, unsigned int count,
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+ u8 *digest)
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+{
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+ unsigned char tmp[SHA1_MAC_LEN], tmp2[SHA1_MAC_LEN];
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+ int i, j;
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+ unsigned char count_buf[4];
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+ const u8 *addr[2];
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+ size_t len[2];
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+ size_t passphrase_len = os_strlen(passphrase);
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+
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+ addr[0] = (u8 *) ssid;
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+ len[0] = ssid_len;
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+ addr[1] = count_buf;
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+ len[1] = 4;
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+
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+ /* F(P, S, c, i) = U1 xor U2 xor ... Uc
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+ * U1 = PRF(P, S || i)
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+ * U2 = PRF(P, U1)
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+ * Uc = PRF(P, Uc-1)
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+ */
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+
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+ count_buf[0] = (count >> 24) & 0xff;
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+ count_buf[1] = (count >> 16) & 0xff;
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+ count_buf[2] = (count >> 8) & 0xff;
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+ count_buf[3] = count & 0xff;
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+ hmac_sha1_vector((u8 *) passphrase, passphrase_len, 2, addr, len, tmp);
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+ os_memcpy(digest, tmp, SHA1_MAC_LEN);
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+
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+ for (i = 1; i < iterations; i++) {
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+ hmac_sha1((u8 *) passphrase, passphrase_len, tmp, SHA1_MAC_LEN,
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+ tmp2);
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+ os_memcpy(tmp, tmp2, SHA1_MAC_LEN);
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+ for (j = 0; j < SHA1_MAC_LEN; j++)
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+ digest[j] ^= tmp2[j];
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+ }
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+}
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+
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+
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+/**
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+ * pbkdf2_sha1 - SHA1-based key derivation function (PBKDF2) for IEEE 802.11i
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+ * @passphrase: ASCII passphrase
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+ * @ssid: SSID
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+ * @ssid_len: SSID length in bytes
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+ * @iterations: Number of iterations to run
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+ * @buf: Buffer for the generated key
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+ * @buflen: Length of the buffer in bytes
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+ *
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+ * This function is used to derive PSK for WPA-PSK. For this protocol,
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+ * iterations is set to 4096 and buflen to 32. This function is described in
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+ * IEEE Std 802.11-2004, Clause H.4. The main construction is from PKCS#5 v2.0.
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+ */
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+void pbkdf2_sha1(const char *passphrase, const char *ssid, size_t ssid_len,
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+ int iterations, u8 *buf, size_t buflen)
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+{
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+ unsigned int count = 0;
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+ unsigned char *pos = buf;
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+ size_t left = buflen, plen;
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+ unsigned char digest[SHA1_MAC_LEN];
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+
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+ while (left > 0) {
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+ count++;
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+ pbkdf2_sha1_f(passphrase, ssid, ssid_len, iterations, count,
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+ digest);
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+ plen = left > SHA1_MAC_LEN ? SHA1_MAC_LEN : left;
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+ os_memcpy(pos, digest, plen);
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+ pos += plen;
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+ left -= plen;
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+ }
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+}
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