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* Software WEP encryption implementation
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* Copyright 2002, Jouni Malinen <jkmaline@cc.hut.fi>
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* Copyright 2003, Instant802 Networks, Inc.
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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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#include <linux/netdevice.h>
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#include <linux/types.h>
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#include <linux/random.h>
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#include <linux/compiler.h>
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#include <linux/crc32.h>
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#include <linux/crypto.h>
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#include <linux/err.h>
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#include <linux/scatterlist.h>
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#include <net/mac80211.h>
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#include "ieee80211_i.h"
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int ieee80211_wep_init(struct ieee80211_local *local)
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/* start WEP IV from a random value */
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get_random_bytes(&local->wep_iv, WEP_IV_LEN);
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local->wep_tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0,
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if (IS_ERR(local->wep_tx_tfm))
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local->wep_rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0,
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if (IS_ERR(local->wep_rx_tfm)) {
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crypto_free_blkcipher(local->wep_tx_tfm);
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void ieee80211_wep_free(struct ieee80211_local *local)
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crypto_free_blkcipher(local->wep_tx_tfm);
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crypto_free_blkcipher(local->wep_rx_tfm);
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static inline int ieee80211_wep_weak_iv(u32 iv, int keylen)
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/* Fluhrer, Mantin, and Shamir have reported weaknesses in the
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* key scheduling algorithm of RC4. At least IVs (KeyByte + 3,
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* 0xff, N) can be used to speedup attacks, so avoid using them. */
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if ((iv & 0xff00) == 0xff00) {
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u8 B = (iv >> 16) & 0xff;
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if (B >= 3 && B < 3 + keylen)
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void ieee80211_wep_get_iv(struct ieee80211_local *local,
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struct ieee80211_key *key, u8 *iv)
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if (ieee80211_wep_weak_iv(local->wep_iv, key->keylen))
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local->wep_iv += 0x0100;
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*iv++ = (local->wep_iv >> 16) & 0xff;
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*iv++ = (local->wep_iv >> 8) & 0xff;
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*iv++ = local->wep_iv & 0xff;
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*iv++ = key->keyidx << 6;
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u8 * ieee80211_wep_add_iv(struct ieee80211_local *local,
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struct ieee80211_key *key)
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struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
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fc = le16_to_cpu(hdr->frame_control);
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fc |= IEEE80211_FCTL_PROTECTED;
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hdr->frame_control = cpu_to_le16(fc);
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if ((skb_headroom(skb) < WEP_IV_LEN ||
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skb_tailroom(skb) < WEP_ICV_LEN)) {
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I802_DEBUG_INC(local->tx_expand_skb_head);
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if (unlikely(pskb_expand_head(skb, WEP_IV_LEN, WEP_ICV_LEN,
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hdrlen = iwlwifi_ieee80211_get_hdrlen(fc);
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newhdr = skb_push(skb, WEP_IV_LEN);
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memmove(newhdr, newhdr + WEP_IV_LEN, hdrlen);
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ieee80211_wep_get_iv(local, key, newhdr + hdrlen);
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return newhdr + hdrlen;
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void ieee80211_wep_remove_iv(struct ieee80211_local *local,
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struct ieee80211_key *key)
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struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
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fc = le16_to_cpu(hdr->frame_control);
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hdrlen = iwlwifi_ieee80211_get_hdrlen(fc);
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memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen);
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skb_pull(skb, WEP_IV_LEN);
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/* Perform WEP encryption using given key. data buffer must have tailroom
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* for 4-byte ICV. data_len must not include this ICV. Note: this function
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* does _not_ add IV. data = RC4(data | CRC32(data)) */
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void ieee80211_wep_encrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key,
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size_t klen, u8 *data, size_t data_len)
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struct blkcipher_desc desc = { .tfm = tfm };
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struct scatterlist sg;
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icv = (__le32 *)(data + data_len);
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*icv = cpu_to_le32(~crc32_le(~0, data, data_len));
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crypto_blkcipher_setkey(tfm, rc4key, klen);
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sg_init_one(&sg, data, data_len + WEP_ICV_LEN);
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crypto_blkcipher_encrypt(&desc, &sg, &sg, sg.length);
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/* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the
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* beginning of the buffer 4 bytes of extra space (ICV) in the end of the
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* buffer will be added. Both IV and ICV will be transmitted, so the
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* payload length increases with 8 bytes.
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* WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
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int ieee80211_wep_encrypt(struct ieee80211_local *local, struct sk_buff *skb,
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struct ieee80211_key *key)
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if (!key || key->alg != ALG_WEP)
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klen = 3 + key->keylen;
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rc4key = kmalloc(klen, GFP_ATOMIC);
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iv = ieee80211_wep_add_iv(local, skb, key);
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len = skb->len - (iv + WEP_IV_LEN - skb->data);
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/* Prepend 24-bit IV to RC4 key */
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memcpy(rc4key, iv, 3);
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/* Copy rest of the WEP key (the secret part) */
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memcpy(rc4key + 3, key->key, key->keylen);
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/* Add room for ICV */
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skb_put(skb, WEP_ICV_LEN);
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ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, klen,
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iv + WEP_IV_LEN, len);
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/* Perform WEP decryption using given key. data buffer includes encrypted
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* payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV.
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* Return 0 on success and -1 on ICV mismatch. */
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int ieee80211_wep_decrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key,
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size_t klen, u8 *data, size_t data_len)
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struct blkcipher_desc desc = { .tfm = tfm };
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struct scatterlist sg;
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crypto_blkcipher_setkey(tfm, rc4key, klen);
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sg_init_one(&sg, data, data_len + WEP_ICV_LEN);
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crypto_blkcipher_decrypt(&desc, &sg, &sg, sg.length);
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crc = cpu_to_le32(~crc32_le(~0, data, data_len));
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if (memcmp(&crc, data + data_len, WEP_ICV_LEN) != 0)
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/* Perform WEP decryption on given skb. 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). skb->len includes both IV and ICV.
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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, i.e., decrypted payload
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* is moved to the beginning of the skb and skb length will be reduced.
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int ieee80211_wep_decrypt(struct ieee80211_local *local, struct sk_buff *skb,
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struct ieee80211_key *key)
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struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
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fc = le16_to_cpu(hdr->frame_control);
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if (!(fc & IEEE80211_FCTL_PROTECTED))
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hdrlen = iwlwifi_ieee80211_get_hdrlen(fc);
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if (skb->len < 8 + hdrlen)
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len = skb->len - hdrlen - 8;
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keyidx = skb->data[hdrlen + 3] >> 6;
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if (!key || keyidx != key->keyidx || key->alg != ALG_WEP)
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klen = 3 + key->keylen;
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rc4key = kmalloc(klen, GFP_ATOMIC);
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/* Prepend 24-bit IV to RC4 key */
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memcpy(rc4key, skb->data + hdrlen, 3);
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/* Copy rest of the WEP key (the secret part) */
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memcpy(rc4key + 3, key->key, key->keylen);
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if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen,
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skb->data + hdrlen + WEP_IV_LEN,
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printk(KERN_DEBUG "WEP decrypt failed (ICV)\n");
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skb_trim(skb, skb->len - WEP_ICV_LEN);
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memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen);
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skb_pull(skb, WEP_IV_LEN);
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int ieee80211_wep_get_keyidx(struct sk_buff *skb)
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struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
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fc = le16_to_cpu(hdr->frame_control);
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if (!(fc & IEEE80211_FCTL_PROTECTED))
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hdrlen = iwlwifi_ieee80211_get_hdrlen(fc);
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if (skb->len < 8 + hdrlen)
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return skb->data[hdrlen + 3] >> 6;
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u8 * ieee80211_wep_is_weak_iv(struct sk_buff *skb, struct ieee80211_key *key)
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struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
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fc = le16_to_cpu(hdr->frame_control);
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if (!(fc & IEEE80211_FCTL_PROTECTED))
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hdrlen = iwlwifi_ieee80211_get_hdrlen(fc);
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ivpos = skb->data + hdrlen;
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iv = (ivpos[0] << 16) | (ivpos[1] << 8) | ivpos[2];
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if (ieee80211_wep_weak_iv(iv, key->keylen))