text: /*-
   * Copyright (c) 2002-2008 Sam Leffler, Errno Consulting
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
   * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
   * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
   * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
   * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
   * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   *
   * $FreeBSD: head/sys/net80211/ieee80211_crypto_wep.c 186302 2008-12-18 23:00:09Z sam $
   */
  
  /*
   * IEEE 802.11 WEP crypto support.
   */
  #include "opt_wlan.h"
  
  #include <sys/param.h>
  #include <sys/systm.h> 
  #include <sys/mbuf.h>   
  #include <sys/malloc.h>
  #include <sys/kernel.h>
  #include <sys/module.h>
  #include <sys/endian.h>
  
  #include <sys/socket.h>
  
  #include <net/if.h>
  #include <net/if_media.h>
  #include <net/ethernet.h>
  #include <net/route.h>
  
  #include <netproto/802_11/ieee80211_var.h>
  
  static	void *wep_attach(struct ieee80211vap *, struct ieee80211_key *);
  static	void wep_detach(struct ieee80211_key *);
  static	int wep_setkey(struct ieee80211_key *);
  static	int wep_encap(struct ieee80211_key *, struct mbuf *, uint8_t keyid);
  static	int wep_decap(struct ieee80211_key *, struct mbuf *, int hdrlen);
  static	int wep_enmic(struct ieee80211_key *, struct mbuf *, int);
  static	int wep_demic(struct ieee80211_key *, struct mbuf *, int);
  
  static const struct ieee80211_cipher wep = {
  	.ic_name	= "WEP",
  	.ic_cipher	= IEEE80211_CIPHER_WEP,
  	.ic_header	= IEEE80211_WEP_IVLEN + IEEE80211_WEP_KIDLEN,
  	.ic_trailer	= IEEE80211_WEP_CRCLEN,
  	.ic_miclen	= 0,
  	.ic_attach	= wep_attach,
  	.ic_detach	= wep_detach,
  	.ic_setkey	= wep_setkey,
  	.ic_encap	= wep_encap,
  	.ic_decap	= wep_decap,
  	.ic_enmic	= wep_enmic,
  	.ic_demic	= wep_demic,
  };
  
  static	int wep_encrypt(struct ieee80211_key *, struct mbuf *, int hdrlen);
  static	int wep_decrypt(struct ieee80211_key *, struct mbuf *, int hdrlen);
  
  struct wep_ctx {
  	struct ieee80211vap *wc_vap;	/* for diagnostics+statistics */
  	struct ieee80211com *wc_ic;
  	uint32_t	wc_iv;		/* initial vector for crypto */
  };
  
  /* number of references from net80211 layer */
  static	int nrefs = 0;
  
  static void *
  wep_attach(struct ieee80211vap *vap, struct ieee80211_key *k)
  {
  	struct wep_ctx *ctx;
  
  	ctx = (struct wep_ctx *) kmalloc(sizeof(struct wep_ctx),
  		M_80211_CRYPTO, M_INTWAIT | M_ZERO);
  	if (ctx == NULL) {
  		vap->iv_stats.is_crypto_nomem++;
  		return NULL;
  	}
  
  	ctx->wc_vap = vap;
  	ctx->wc_ic = vap->iv_ic;
  	get_random_bytes(&ctx->wc_iv, sizeof(ctx->wc_iv));
  	nrefs++;			/* NB: we assume caller locking */
  	return ctx;
  }
  
  static void
  wep_detach(struct ieee80211_key *k)
  {
  	struct wep_ctx *ctx = k->wk_private;
  
  	kfree(ctx, M_80211_CRYPTO);
  	KASSERT(nrefs > 0, ("imbalanced attach/detach"));
  	nrefs--;			/* NB: we assume caller locking */
  }
  
  static int
  wep_setkey(struct ieee80211_key *k)
  {
  	return k->wk_keylen >= 40/NBBY;
  }
  
  /*
   * Add privacy headers appropriate for the specified key.
   */
  static int
  wep_encap(struct ieee80211_key *k, struct mbuf *m, uint8_t keyid)
  {
  	struct wep_ctx *ctx = k->wk_private;
  	struct ieee80211com *ic = ctx->wc_ic;
  	uint32_t iv;
  	uint8_t *ivp;
  	int hdrlen;
  
  	hdrlen = ieee80211_hdrspace(ic, mtod(m, void *));
  
  	/*
  	 * Copy down 802.11 header and add the IV + KeyID.
  	 */
  	M_PREPEND(m, wep.ic_header, MB_DONTWAIT);
  	if (m == NULL)
  		return 0;
  	ivp = mtod(m, uint8_t *);
  	ovbcopy(ivp + wep.ic_header, ivp, hdrlen);
  	ivp += hdrlen;
  
  	/*
  	 * XXX
  	 * IV must not duplicate during the lifetime of the key.
  	 * But no mechanism to renew keys is defined in IEEE 802.11
  	 * for WEP.  And the IV may be duplicated at other stations
  	 * because the session key itself is shared.  So we use a
  	 * pseudo random IV for now, though it is not the right way.
  	 *
  	 * NB: Rather than use a strictly random IV we select a
  	 * random one to start and then increment the value for
  	 * each frame.  This is an explicit tradeoff between
  	 * overhead and security.  Given the basic insecurity of
  	 * WEP this seems worthwhile.
  	 */
  
  	/*
  	 * Skip 'bad' IVs from Fluhrer/Mantin/Shamir:
  	 * (B, 255, N) with 3 <= B < 16 and 0 <= N <= 255
  	 */
  	iv = ctx->wc_iv;
  	if ((iv & 0xff00) == 0xff00) {
  		int B = (iv & 0xff0000) >> 16;
  		if (3 <= B && B < 16)
  			iv += 0x0100;
  	}
  	ctx->wc_iv = iv + 1;
  
  	/*
  	 * NB: Preserve byte order of IV for packet
  	 *     sniffers; it doesn't matter otherwise.
  	 */
  #if _BYTE_ORDER == _BIG_ENDIAN
  	ivp[0] = iv >> 0;
  	ivp[1] = iv >> 8;
  	ivp[2] = iv >> 16;
  #else
  	ivp[2] = iv >> 0;
  	ivp[1] = iv >> 8;
  	ivp[0] = iv >> 16;
  #endif
  	ivp[3] = keyid;
  
  	/*
  	 * Finally, do software encrypt if neeed.
  	 */
  	if ((k->wk_flags & IEEE80211_KEY_SWENCRYPT) &&
  	    !wep_encrypt(k, m, hdrlen))
  		return 0;
  
  	return 1;
  }
  
  /*
   * Add MIC to the frame as needed.
   */
  static int
  wep_enmic(struct ieee80211_key *k, struct mbuf *m, int force)
  {
  
  	return 1;
  }
  
  /*
   * Validate and strip privacy headers (and trailer) for a
   * received frame.  If necessary, decrypt the frame using
   * the specified key.
   */
  static int
  wep_decap(struct ieee80211_key *k, struct mbuf *m, int hdrlen)
  {
  	struct wep_ctx *ctx = k->wk_private;
  	struct ieee80211vap *vap = ctx->wc_vap;
  #ifdef IEEE80211_DEBUG
  	struct ieee80211_frame *wh;
  #endif
  
  #ifdef IEEE80211_DEBUG
  	wh = mtod(m, struct ieee80211_frame *);
  #endif
  
  	/*
  	 * Check if the device handled the decrypt in hardware.
  	 * If so we just strip the header; otherwise we need to
  	 * handle the decrypt in software.
  	 */
  	if ((k->wk_flags & IEEE80211_KEY_SWDECRYPT) &&
  	    !wep_decrypt(k, m, hdrlen)) {
  		IEEE80211_NOTE_MAC(vap, IEEE80211_MSG_CRYPTO, wh->i_addr2,
  		    "%s", "WEP ICV mismatch on decrypt");
  		vap->iv_stats.is_rx_wepfail++;
  		return 0;
  	}
  
  	/*
  	 * Copy up 802.11 header and strip crypto bits.
  	 */
  	ovbcopy(mtod(m, void *), mtod(m, uint8_t *) + wep.ic_header, hdrlen);
  	m_adj(m, wep.ic_header);
  	m_adj(m, -wep.ic_trailer);
  
  	return 1;
  }
  
  /*
   * Verify and strip MIC from the frame.
   */
  static int
  wep_demic(struct ieee80211_key *k, struct mbuf *skb, int force)
  {
  	return 1;
  }
  
  static const uint32_t crc32_table[256] = {
  	0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L,
  	0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0x0edb8832L, 0x79dcb8a4L,
  	0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L,
  	0x90bf1d91L, 0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL,
  	0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L, 0x136c9856L,
  	0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL, 0x14015c4fL, 0x63066cd9L,
  	0xfa0f3d63L, 0x8d080df5L, 0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L,
  	0xa2677172L, 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL,
  	0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L, 0x32d86ce3L,
  	0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L, 0x26d930acL, 0x51de003aL,
  	0xc8d75180L, 0xbfd06116L, 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L,
  	0xb8bda50fL, 0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L,
  	0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL, 0x76dc4190L,
  	0x01db7106L, 0x98d220bcL, 0xefd5102aL, 0x71b18589L, 0x06b6b51fL,
  	0x9fbfe4a5L, 0xe8b8d433L, 0x7807c9a2L, 0x0f00f934L, 0x9609a88eL,
  	0xe10e9818L, 0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L,
  	0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL, 0x6c0695edL,
  	0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L, 0x65b0d9c6L, 0x12b7e950L,
  	0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L,
  	0xfbd44c65L, 0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L,
  	0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL, 0x4369e96aL,
  	0x346ed9fcL, 0xad678846L, 0xda60b8d0L, 0x44042d73L, 0x33031de5L,
  	0xaa0a4c5fL, 0xdd0d7cc9L, 0x5005713cL, 0x270241aaL, 0xbe0b1010L,
  	0xc90c2086L, 0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL,
  	0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L, 0x59b33d17L,
  	0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL, 0xedb88320L, 0x9abfb3b6L,
  	0x03b6e20cL, 0x74b1d29aL, 0xead54739L, 0x9dd277afL, 0x04db2615L,
  	0x73dc1683L, 0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L,
  	0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L, 0xf00f9344L,
  	0x8708a3d2L, 0x1e01f268L, 0x6906c2feL, 0xf762575dL, 0x806567cbL,
  	0x196c3671L, 0x6e6b06e7L, 0xfed41b76L, 0x89d32be0L, 0x10da7a5aL,
  	0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L,
  	0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L, 0xd1bb67f1L,
  	0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL, 0xd80d2bdaL, 0xaf0a1b4cL,
  	0x36034af6L, 0x41047a60L, 0xdf60efc3L, 0xa867df55L, 0x316e8eefL,
  	0x4669be79L, 0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L,
  	0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL, 0xc5ba3bbeL,
  	0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L, 0xc2d7ffa7L, 0xb5d0cf31L,
  	0x2cd99e8bL, 0x5bdeae1dL, 0x9b64c2b0L, 0xec63f226L, 0x756aa39cL,
  	0x026d930aL, 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L,
  	0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L, 0x92d28e9bL,
  	0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L, 0x86d3d2d4L, 0xf1d4e242L,
  	0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L,
  	0x18b74777L, 0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL,
  	0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L, 0xa00ae278L,
  	0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L, 0xa7672661L, 0xd06016f7L,
  	0x4969474dL, 0x3e6e77dbL, 0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L,
  	0x37d83bf0L, 0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L,
  	0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L, 0xbad03605L,
  	0xcdd70693L, 0x54de5729L, 0x23d967bfL, 0xb3667a2eL, 0xc4614ab8L,
  	0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL,
  	0x2d02ef8dL
  };
  
  static int
  wep_encrypt(struct ieee80211_key *key, struct mbuf *m0, int hdrlen)
  {
  #define S_SWAP(a,b) do { uint8_t t = S[a]; S[a] = S[b]; S[b] = t; } while(0)
  	struct wep_ctx *ctx = key->wk_private;
  	struct ieee80211vap *vap = ctx->wc_vap;
  	struct mbuf *m = m0;
  	uint8_t rc4key[IEEE80211_WEP_IVLEN + IEEE80211_KEYBUF_SIZE];
  	uint8_t icv[IEEE80211_WEP_CRCLEN];
  	uint32_t i, j, k, crc;
  	size_t buflen, data_len;
  	uint8_t S[256];
  	uint8_t *pos;
  	u_int off, keylen;
  
  	vap->iv_stats.is_crypto_wep++;
  
  	/* NB: this assumes the header was pulled up */
  	memcpy(rc4key, mtod(m, uint8_t *) + hdrlen, IEEE80211_WEP_IVLEN);
  	memcpy(rc4key + IEEE80211_WEP_IVLEN, key->wk_key, key->wk_keylen);
  
  	/* Setup RC4 state */
  	for (i = 0; i < 256; i++)
  		S[i] = i;
  	j = 0;
  	keylen = key->wk_keylen + IEEE80211_WEP_IVLEN;
  	for (i = 0; i < 256; i++) {
  		j = (j + S[i] + rc4key[i % keylen]) & 0xff;
  		S_SWAP(i, j);
  	}
  
  	off = hdrlen + wep.ic_header;
  	data_len = m->m_pkthdr.len - off;
  
  	/* Compute CRC32 over unencrypted data and apply RC4 to data */
  	crc = ~0;
  	i = j = 0;
  	pos = mtod(m, uint8_t *) + off;
  	buflen = m->m_len - off;
  	for (;;) {
  		if (buflen > data_len)
  			buflen = data_len;
  		data_len -= buflen;
  		for (k = 0; k < buflen; k++) {
  			crc = crc32_table[(crc ^ *pos) & 0xff] ^ (crc >> 8);
  			i = (i + 1) & 0xff;
  			j = (j + S[i]) & 0xff;
  			S_SWAP(i, j);
  			*pos++ ^= S[(S[i] + S[j]) & 0xff];
  		}
  		if (m->m_next == NULL) {
  			if (data_len != 0) {		/* out of data */
  				IEEE80211_NOTE_MAC(vap, IEEE80211_MSG_CRYPTO,
  				    mtod(m0,
  					struct ieee80211_frame *)->i_addr2,
  				    "out of data for WEP (data_len %zu)",
  				    data_len);
  				/* XXX stat */
  				return 0;
  			}
  			break;
  		}
  		m = m->m_next;
  		pos = mtod(m, uint8_t *);
  		buflen = m->m_len;
  	}
  	crc = ~crc;
  
  	/* Append little-endian CRC32 and encrypt it to produce ICV */
  	icv[0] = crc;
  	icv[1] = crc >> 8;
  	icv[2] = crc >> 16;
  	icv[3] = crc >> 24;
  	for (k = 0; k < IEEE80211_WEP_CRCLEN; k++) {
  		i = (i + 1) & 0xff;
  		j = (j + S[i]) & 0xff;
  		S_SWAP(i, j);
  		icv[k] ^= S[(S[i] + S[j]) & 0xff];
  	}
  	return m_append(m0, IEEE80211_WEP_CRCLEN, icv);
  #undef S_SWAP
  }
  
  static int
  wep_decrypt(struct ieee80211_key *key, struct mbuf *m0, int hdrlen)
  {
  #define S_SWAP(a,b) do { uint8_t t = S[a]; S[a] = S[b]; S[b] = t; } while(0)
  	struct wep_ctx *ctx = key->wk_private;
  	struct ieee80211vap *vap = ctx->wc_vap;
  	struct mbuf *m = m0;
  	uint8_t rc4key[IEEE80211_WEP_IVLEN + IEEE80211_KEYBUF_SIZE];
  	uint8_t icv[IEEE80211_WEP_CRCLEN];
  	uint32_t i, j, k, crc;
  	size_t buflen, data_len;
  	uint8_t S[256];
  	uint8_t *pos;
  	u_int off, keylen;
  
  	vap->iv_stats.is_crypto_wep++;
  
  	/* NB: this assumes the header was pulled up */
  	memcpy(rc4key, mtod(m, uint8_t *) + hdrlen, IEEE80211_WEP_IVLEN);
  	memcpy(rc4key + IEEE80211_WEP_IVLEN, key->wk_key, key->wk_keylen);
  
  	/* Setup RC4 state */
  	for (i = 0; i < 256; i++)
  		S[i] = i;
  	j = 0;
  	keylen = key->wk_keylen + IEEE80211_WEP_IVLEN;
  	for (i = 0; i < 256; i++) {
  		j = (j + S[i] + rc4key[i % keylen]) & 0xff;
  		S_SWAP(i, j);
  	}
  
  	off = hdrlen + wep.ic_header;
  	data_len = m->m_pkthdr.len - (off + wep.ic_trailer),
  
  	/* Compute CRC32 over unencrypted data and apply RC4 to data */
  	crc = ~0;
  	i = j = 0;
  	pos = mtod(m, uint8_t *) + off;
  	buflen = m->m_len - off;
  	for (;;) {
  		if (buflen > data_len)
  			buflen = data_len;
  		data_len -= buflen;
  		for (k = 0; k < buflen; k++) {
  			i = (i + 1) & 0xff;
  			j = (j + S[i]) & 0xff;
  			S_SWAP(i, j);
  			*pos ^= S[(S[i] + S[j]) & 0xff];
  			crc = crc32_table[(crc ^ *pos) & 0xff] ^ (crc >> 8);
  			pos++;
  		}
  		m = m->m_next;
  		if (m == NULL) {
  			if (data_len != 0) {		/* out of data */
  				IEEE80211_NOTE_MAC(vap, IEEE80211_MSG_CRYPTO,
  				    mtod(m0, struct ieee80211_frame *)->i_addr2,
  				    "out of data for WEP (data_len %zu)",
  				    data_len);
  				return 0;
  			}
  			break;
  		}
  		pos = mtod(m, uint8_t *);
  		buflen = m->m_len;
  	}
  	crc = ~crc;
  
  	/* Encrypt little-endian CRC32 and verify that it matches with
  	 * received ICV */
  	icv[0] = crc;
  	icv[1] = crc >> 8;
  	icv[2] = crc >> 16;
  	icv[3] = crc >> 24;
  	for (k = 0; k < IEEE80211_WEP_CRCLEN; k++) {
  		i = (i + 1) & 0xff;
  		j = (j + S[i]) & 0xff;
  		S_SWAP(i, j);
  		/* XXX assumes ICV is contiguous in mbuf */
  		if ((icv[k] ^ S[(S[i] + S[j]) & 0xff]) != *pos++) {
  			/* ICV mismatch - drop frame */
  			return 0;
  		}
  	}
  	return 1;
  #undef S_SWAP
  }
  
  /*
   * Module glue.
   */
  IEEE80211_CRYPTO_MODULE(wep, 1);
  