/* * Software WEP encryption implementation * Copyright 2002, Jouni Malinen <jkmaline@cc.hut.fi> * Copyright 2003, Instant802 Networks, Inc. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. */ #include <linux/netdevice.h> #include <linux/types.h> #include <linux/random.h> #include <linux/compiler.h> #include <linux/crc32.h> #include <linux/crypto.h> #include <linux/err.h> #include <linux/mm.h> #include <linux/scatterlist.h> #include <asm/unaligned.h> #include <net/mac80211.h> #include "ieee80211_i.h" #include "wep.h" int ieee80211_wep_init(struct ieee80211_local *local) { /* start WEP IV from a random value */ get_random_bytes(&local->wep_iv, WEP_IV_LEN); local->wep_tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC); if (IS_ERR(local->wep_tx_tfm)) return PTR_ERR(local->wep_tx_tfm); local->wep_rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC); if (IS_ERR(local->wep_rx_tfm)) { crypto_free_blkcipher(local->wep_tx_tfm); return PTR_ERR(local->wep_rx_tfm); } return 0; } void ieee80211_wep_free(struct ieee80211_local *local) { crypto_free_blkcipher(local->wep_tx_tfm); crypto_free_blkcipher(local->wep_rx_tfm); } static inline bool ieee80211_wep_weak_iv(u32 iv, int keylen) { /* * Fluhrer, Mantin, and Shamir have reported weaknesses in the * key scheduling algorithm of RC4. At least IVs (KeyByte + 3, * 0xff, N) can be used to speedup attacks, so avoid using them. */ if ((iv & 0xff00) == 0xff00) { u8 B = (iv >> 16) & 0xff; if (B >= 3 && B < 3 + keylen) return true; } return false; } static void ieee80211_wep_get_iv(struct ieee80211_local *local, struct ieee80211_key *key, u8 *iv) { local->wep_iv++; if (ieee80211_wep_weak_iv(local->wep_iv, key->conf.keylen)) local->wep_iv += 0x0100; if (!iv) return; *iv++ = (local->wep_iv >> 16) & 0xff; *iv++ = (local->wep_iv >> 8) & 0xff; *iv++ = local->wep_iv & 0xff; *iv++ = key->conf.keyidx << 6; } static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local, struct sk_buff *skb, struct ieee80211_key *key) { struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; unsigned int hdrlen; u8 *newhdr; hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED); if (WARN_ON(skb_tailroom(skb) < WEP_ICV_LEN || skb_headroom(skb) < WEP_IV_LEN)) return NULL; hdrlen = ieee80211_hdrlen(hdr->frame_control); newhdr = skb_push(skb, WEP_IV_LEN); memmove(newhdr, newhdr + WEP_IV_LEN, hdrlen); ieee80211_wep_get_iv(local, key, newhdr + hdrlen); return newhdr + hdrlen; } static void ieee80211_wep_remove_iv(struct ieee80211_local *local, struct sk_buff *skb, struct ieee80211_key *key) { struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; unsigned int hdrlen; hdrlen = ieee80211_hdrlen(hdr->frame_control); memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen); skb_pull(skb, WEP_IV_LEN); } /* Perform WEP encryption using given key. data buffer must have tailroom * for 4-byte ICV. data_len must not include this ICV. Note: this function * does _not_ add IV. data = RC4(data | CRC32(data)) */ void ieee80211_wep_encrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key, size_t klen, u8 *data, size_t data_len) { struct blkcipher_desc desc = { .tfm = tfm }; struct scatterlist sg; __le32 icv; icv = cpu_to_le32(~crc32_le(~0, data, data_len)); put_unaligned(icv, (__le32 *)(data + data_len)); crypto_blkcipher_setkey(tfm, rc4key, klen); sg_init_one(&sg, data, data_len + WEP_ICV_LEN); crypto_blkcipher_encrypt(&desc, &sg, &sg, sg.length); } /* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the * beginning of the buffer 4 bytes of extra space (ICV) in the end of the * buffer will be added. Both IV and ICV will be transmitted, so the * payload length increases with 8 bytes. * * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data)) */ int ieee80211_wep_encrypt(struct ieee80211_local *local, struct sk_buff *skb, struct ieee80211_key *key) { u32 klen; u8 *rc4key, *iv; size_t len; if (!key || key->conf.alg != ALG_WEP) return -1; klen = 3 + key->conf.keylen; rc4key = kmalloc(klen, GFP_ATOMIC); if (!rc4key) return -1; iv = ieee80211_wep_add_iv(local, skb, key); if (!iv) { kfree(rc4key); return -1; } len = skb->len - (iv + WEP_IV_LEN - skb->data); /* Prepend 24-bit IV to RC4 key */ memcpy(rc4key, iv, 3); /* Copy rest of the WEP key (the secret part) */ memcpy(rc4key + 3, key->conf.key, key->conf.keylen); /* Add room for ICV */ skb_put(skb, WEP_ICV_LEN); ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, klen, iv + WEP_IV_LEN, len); kfree(rc4key); return 0; } /* Perform WEP decryption using given key. data buffer includes encrypted * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV. * Return 0 on success and -1 on ICV mismatch. */ int ieee80211_wep_decrypt_data(struct crypto_blkcipher *tfm, u8 *rc4key, size_t klen, u8 *data, size_t data_len) { struct blkcipher_desc desc = { .tfm = tfm }; struct scatterlist sg; __le32 crc; crypto_blkcipher_setkey(tfm, rc4key, klen); sg_init_one(&sg, data, data_len + WEP_ICV_LEN); crypto_blkcipher_decrypt(&desc, &sg, &sg, sg.length); crc = cpu_to_le32(~crc32_le(~0, data, data_len)); if (memcmp(&crc, data + data_len, WEP_ICV_LEN) != 0) /* ICV mismatch */ return -1; return 0; } /* Perform WEP decryption on given skb. Buffer includes whole WEP part of * the frame: IV (4 bytes), encrypted payload (including SNAP header), * ICV (4 bytes). skb->len includes both IV and ICV. * * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload * is moved to the beginning of the skb and skb length will be reduced. */ int ieee80211_wep_decrypt(struct ieee80211_local *local, struct sk_buff *skb, struct ieee80211_key *key) { u32 klen; u8 *rc4key; u8 keyidx; struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; unsigned int hdrlen; size_t len; int ret = 0; if (!ieee80211_has_protected(hdr->frame_control)) return -1; hdrlen = ieee80211_hdrlen(hdr->frame_control); if (skb->len < hdrlen + WEP_IV_LEN + WEP_ICV_LEN) return -1; len = skb->len - hdrlen - WEP_IV_LEN - WEP_ICV_LEN; keyidx = skb->data[hdrlen + 3] >> 6; if (!key || keyidx != key->conf.keyidx || key->conf.alg != ALG_WEP) return -1; klen = 3 + key->conf.keylen; rc4key = kmalloc(klen, GFP_ATOMIC); if (!rc4key) return -1; /* Prepend 24-bit IV to RC4 key */ memcpy(rc4key, skb->data + hdrlen, 3); /* Copy rest of the WEP key (the secret part) */ memcpy(rc4key + 3, key->conf.key, key->conf.keylen); if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen, skb->data + hdrlen + WEP_IV_LEN, len)) ret = -1; kfree(rc4key); /* Trim ICV */ skb_trim(skb, skb->len - WEP_ICV_LEN); /* Remove IV */ memmove(skb->data + WEP_IV_LEN, skb->data, hdrlen); skb_pull(skb, WEP_IV_LEN); return ret; } bool ieee80211_wep_is_weak_iv(struct sk_buff *skb, struct ieee80211_key *key) { struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; unsigned int hdrlen; u8 *ivpos; u32 iv; if (!ieee80211_has_protected(hdr->frame_control)) return false; hdrlen = ieee80211_hdrlen(hdr->frame_control); ivpos = skb->data + hdrlen; iv = (ivpos[0] << 16) | (ivpos[1] << 8) | ivpos[2]; return ieee80211_wep_weak_iv(iv, key->conf.keylen); } ieee80211_rx_result ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx) { struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)rx->skb->data; if (!ieee80211_is_data(hdr->frame_control) && !ieee80211_is_auth(hdr->frame_control)) return RX_CONTINUE; if (!(rx->status->flag & RX_FLAG_DECRYPTED)) { if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key)) return RX_DROP_UNUSABLE; } else if (!(rx->status->flag & RX_FLAG_IV_STRIPPED)) { ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key); /* remove ICV */ skb_trim(rx->skb, rx->skb->len - WEP_ICV_LEN); } return RX_CONTINUE; } static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb) { struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb); if (!(tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE)) { if (ieee80211_wep_encrypt(tx->local, skb, tx->key)) return -1; } else { info->control.hw_key = &tx->key->conf; if (tx->key->conf.flags & IEEE80211_KEY_FLAG_GENERATE_IV) { if (!ieee80211_wep_add_iv(tx->local, skb, tx->key)) return -1; } } return 0; } ieee80211_tx_result ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx) { struct sk_buff *skb; ieee80211_tx_set_protected(tx); skb = tx->skb; do { if (wep_encrypt_skb(tx, skb) < 0) { I802_DEBUG_INC(tx->local->tx_handlers_drop_wep); return TX_DROP; } } while ((skb = skb->next)); return TX_CONTINUE; }