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256 lines
6.0 KiB
256 lines
6.0 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* lib80211 crypt: host-based WEP encryption implementation for lib80211 |
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* |
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* Copyright (c) 2002-2004, Jouni Malinen <[email protected]> |
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* Copyright (c) 2008, John W. Linville <[email protected]> |
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*/ |
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#include <linux/err.h> |
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#include <linux/fips.h> |
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#include <linux/module.h> |
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#include <linux/init.h> |
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#include <linux/slab.h> |
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#include <linux/random.h> |
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#include <linux/scatterlist.h> |
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#include <linux/skbuff.h> |
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#include <linux/mm.h> |
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#include <asm/string.h> |
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#include <net/lib80211.h> |
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#include <crypto/arc4.h> |
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#include <linux/crc32.h> |
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MODULE_AUTHOR("Jouni Malinen"); |
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MODULE_DESCRIPTION("lib80211 crypt: WEP"); |
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MODULE_LICENSE("GPL"); |
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struct lib80211_wep_data { |
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u32 iv; |
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#define WEP_KEY_LEN 13 |
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u8 key[WEP_KEY_LEN + 1]; |
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u8 key_len; |
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u8 key_idx; |
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struct arc4_ctx tx_ctx; |
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struct arc4_ctx rx_ctx; |
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}; |
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static void *lib80211_wep_init(int keyidx) |
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{ |
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struct lib80211_wep_data *priv; |
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if (fips_enabled) |
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return NULL; |
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priv = kzalloc(sizeof(*priv), GFP_ATOMIC); |
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if (priv == NULL) |
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return NULL; |
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priv->key_idx = keyidx; |
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/* start WEP IV from a random value */ |
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get_random_bytes(&priv->iv, 4); |
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return priv; |
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} |
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static void lib80211_wep_deinit(void *priv) |
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{ |
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kfree_sensitive(priv); |
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} |
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/* Add WEP IV/key info to a frame that has at least 4 bytes of headroom */ |
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static int lib80211_wep_build_iv(struct sk_buff *skb, int hdr_len, |
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u8 *key, int keylen, void *priv) |
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{ |
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struct lib80211_wep_data *wep = priv; |
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u32 klen; |
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u8 *pos; |
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if (skb_headroom(skb) < 4 || skb->len < hdr_len) |
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return -1; |
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pos = skb_push(skb, 4); |
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memmove(pos, pos + 4, hdr_len); |
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pos += hdr_len; |
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klen = 3 + wep->key_len; |
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wep->iv++; |
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/* Fluhrer, Mantin, and Shamir have reported weaknesses in the key |
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* scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N) |
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* can be used to speedup attacks, so avoid using them. */ |
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if ((wep->iv & 0xff00) == 0xff00) { |
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u8 B = (wep->iv >> 16) & 0xff; |
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if (B >= 3 && B < klen) |
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wep->iv += 0x0100; |
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} |
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/* Prepend 24-bit IV to RC4 key and TX frame */ |
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*pos++ = (wep->iv >> 16) & 0xff; |
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*pos++ = (wep->iv >> 8) & 0xff; |
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*pos++ = wep->iv & 0xff; |
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*pos++ = wep->key_idx << 6; |
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return 0; |
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} |
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/* Perform WEP encryption on given skb that has at least 4 bytes of headroom |
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* for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted, |
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* so the payload length increases with 8 bytes. |
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* |
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* WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data)) |
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*/ |
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static int lib80211_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv) |
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{ |
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struct lib80211_wep_data *wep = priv; |
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u32 crc, klen, len; |
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u8 *pos, *icv; |
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u8 key[WEP_KEY_LEN + 3]; |
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/* other checks are in lib80211_wep_build_iv */ |
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if (skb_tailroom(skb) < 4) |
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return -1; |
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/* add the IV to the frame */ |
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if (lib80211_wep_build_iv(skb, hdr_len, NULL, 0, priv)) |
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return -1; |
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/* Copy the IV into the first 3 bytes of the key */ |
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skb_copy_from_linear_data_offset(skb, hdr_len, key, 3); |
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/* Copy rest of the WEP key (the secret part) */ |
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memcpy(key + 3, wep->key, wep->key_len); |
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len = skb->len - hdr_len - 4; |
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pos = skb->data + hdr_len + 4; |
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klen = 3 + wep->key_len; |
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/* Append little-endian CRC32 over only the data and encrypt it to produce ICV */ |
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crc = ~crc32_le(~0, pos, len); |
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icv = skb_put(skb, 4); |
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icv[0] = crc; |
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icv[1] = crc >> 8; |
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icv[2] = crc >> 16; |
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icv[3] = crc >> 24; |
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arc4_setkey(&wep->tx_ctx, key, klen); |
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arc4_crypt(&wep->tx_ctx, pos, pos, len + 4); |
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return 0; |
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} |
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/* Perform WEP decryption on given buffer. Buffer includes whole WEP part of |
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* the frame: IV (4 bytes), encrypted payload (including SNAP header), |
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* ICV (4 bytes). len includes both IV and ICV. |
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* |
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* Returns 0 if frame was decrypted successfully and ICV was correct and -1 on |
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* failure. If frame is OK, IV and ICV will be removed. |
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*/ |
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static int lib80211_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv) |
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{ |
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struct lib80211_wep_data *wep = priv; |
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u32 crc, klen, plen; |
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u8 key[WEP_KEY_LEN + 3]; |
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u8 keyidx, *pos, icv[4]; |
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if (skb->len < hdr_len + 8) |
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return -1; |
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pos = skb->data + hdr_len; |
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key[0] = *pos++; |
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key[1] = *pos++; |
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key[2] = *pos++; |
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keyidx = *pos++ >> 6; |
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if (keyidx != wep->key_idx) |
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return -1; |
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klen = 3 + wep->key_len; |
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/* Copy rest of the WEP key (the secret part) */ |
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memcpy(key + 3, wep->key, wep->key_len); |
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/* Apply RC4 to data and compute CRC32 over decrypted data */ |
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plen = skb->len - hdr_len - 8; |
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arc4_setkey(&wep->rx_ctx, key, klen); |
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arc4_crypt(&wep->rx_ctx, pos, pos, plen + 4); |
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crc = ~crc32_le(~0, pos, plen); |
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icv[0] = crc; |
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icv[1] = crc >> 8; |
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icv[2] = crc >> 16; |
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icv[3] = crc >> 24; |
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if (memcmp(icv, pos + plen, 4) != 0) { |
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/* ICV mismatch - drop frame */ |
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return -2; |
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} |
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/* Remove IV and ICV */ |
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memmove(skb->data + 4, skb->data, hdr_len); |
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skb_pull(skb, 4); |
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skb_trim(skb, skb->len - 4); |
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return 0; |
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} |
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static int lib80211_wep_set_key(void *key, int len, u8 * seq, void *priv) |
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{ |
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struct lib80211_wep_data *wep = priv; |
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if (len < 0 || len > WEP_KEY_LEN) |
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return -1; |
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memcpy(wep->key, key, len); |
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wep->key_len = len; |
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return 0; |
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} |
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static int lib80211_wep_get_key(void *key, int len, u8 * seq, void *priv) |
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{ |
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struct lib80211_wep_data *wep = priv; |
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if (len < wep->key_len) |
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return -1; |
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memcpy(key, wep->key, wep->key_len); |
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return wep->key_len; |
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} |
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static void lib80211_wep_print_stats(struct seq_file *m, void *priv) |
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{ |
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struct lib80211_wep_data *wep = priv; |
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seq_printf(m, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len); |
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} |
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static struct lib80211_crypto_ops lib80211_crypt_wep = { |
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.name = "WEP", |
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.init = lib80211_wep_init, |
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.deinit = lib80211_wep_deinit, |
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.encrypt_mpdu = lib80211_wep_encrypt, |
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.decrypt_mpdu = lib80211_wep_decrypt, |
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.encrypt_msdu = NULL, |
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.decrypt_msdu = NULL, |
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.set_key = lib80211_wep_set_key, |
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.get_key = lib80211_wep_get_key, |
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.print_stats = lib80211_wep_print_stats, |
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.extra_mpdu_prefix_len = 4, /* IV */ |
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.extra_mpdu_postfix_len = 4, /* ICV */ |
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.owner = THIS_MODULE, |
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}; |
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static int __init lib80211_crypto_wep_init(void) |
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{ |
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return lib80211_register_crypto_ops(&lib80211_crypt_wep); |
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} |
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static void __exit lib80211_crypto_wep_exit(void) |
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{ |
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lib80211_unregister_crypto_ops(&lib80211_crypt_wep); |
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} |
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module_init(lib80211_crypto_wep_init); |
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module_exit(lib80211_crypto_wep_exit);
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