forked from osmocom/wireshark
88 lines
2.1 KiB
C
88 lines
2.1 KiB
C
/* dot11decrypt_wep.c
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*
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* Copyright (c) 2002-2005 Sam Leffler, Errno Consulting
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* Copyright (c) 2006 CACE Technologies, Davis (California)
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* All rights reserved.
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*
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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#include "config.h"
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/************************************************************************/
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/* File includes */
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#include <glib.h>
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#include "crc32.h"
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/************************************************************************/
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/* Note: copied from net80211/ieee80211_airpdcap_tkip.c */
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#define S_SWAP(a,b) { guint8 t = S[a]; S[a] = S[b]; S[b] = t; }
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/* Note: copied from FreeBSD source code, RELENG 6, */
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/* sys/net80211/ieee80211_crypto_wep.c, 391 */
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int Dot11DecryptWepDecrypt(
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const guchar *seed,
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const size_t seed_len,
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guchar *cypher_text,
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const size_t data_len)
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{
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guint32 i, j, k, crc;
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guint8 S[256];
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guint8 icv[4];
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size_t buflen;
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/* Generate key stream (RC4 Pseudo-Random Number Generator) */
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for (i = 0; i < 256; i++)
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S[i] = (guint8)i;
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for (j = i = 0; i < 256; i++) {
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j = (j + S[i] + seed[i % seed_len]) & 0xff;
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S_SWAP(i, j);
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}
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/* Apply RC4 to data and compute CRC32 over decrypted data */
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crc = ~(guint32)0;
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buflen = data_len;
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for (i = j = k = 0; k < buflen; k++) {
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i = (i + 1) & 0xff;
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j = (j + S[i]) & 0xff;
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S_SWAP(i, j);
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*cypher_text ^= S[(S[i] + S[j]) & 0xff];
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crc = crc32_ccitt_table_lookup((crc ^ *cypher_text) & 0xff) ^ (crc >> 8);
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cypher_text++;
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}
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crc = ~crc;
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/* Encrypt little-endian CRC32 and verify that it matches with the received ICV */
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icv[0] = (guint8)crc;
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icv[1] = (guint8)(crc >> 8);
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icv[2] = (guint8)(crc >> 16);
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icv[3] = (guint8)(crc >> 24);
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for (k = 0; k < 4; k++) {
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i = (i + 1) & 0xff;
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j = (j + S[i]) & 0xff;
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S_SWAP(i, j);
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if ((icv[k] ^ S[(S[i] + S[j]) & 0xff]) != *cypher_text++) {
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/* ICV mismatch - drop frame */
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return 1/*DOT11DECRYPT_RET_UNSUCCESS*/;
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}
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}
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return 0/*DOT11DECRYPT_RET_SUCCESS*/;
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}
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/*
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* Editor modelines - https://www.wireshark.org/tools/modelines.html
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*
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* Local variables:
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* c-basic-offset: 8
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* tab-width: 8
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* indent-tabs-mode: t
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* End:
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*
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* vi: set shiftwidth=8 tabstop=8 noexpandtab:
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* :indentSize=8:tabSize=8:noTabs=false:
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*/
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