/* * 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 <linux/slab.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, IEEE80211_WEP_IV_LEN); local->wep_tx_tfm = crypto_alloc_cipher("arc4", 0, CRYPTO_ALG_ASYNC); if (IS_ERR(local->wep_tx_tfm)) { local->wep_rx_tfm = ERR_PTR(-EINVAL); return PTR_ERR(local->wep_tx_tfm); } local->wep_rx_tfm = crypto_alloc_cipher("arc4", 0, CRYPTO_ALG_ASYNC); if (IS_ERR(local->wep_rx_tfm)) { crypto_free_cipher(local->wep_tx_tfm); local->wep_tx_tfm = ERR_PTR(-EINVAL); return PTR_ERR(local->wep_rx_tfm); } return 0; } void ieee80211_wep_free(struct ieee80211_local *local) { if (!IS_ERR(local->wep_tx_tfm)) crypto_free_cipher(local->wep_tx_tfm); if (!IS_ERR(local->wep_rx_tfm)) crypto_free_cipher(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, int keylen, int keyidx, u8 *iv) { local->wep_iv++; if (ieee80211_wep_weak_iv(local->wep_iv, 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++ = keyidx << 6; } static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local, struct sk_buff *skb, int keylen, int keyidx) { struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb); unsigned int hdrlen; u8 *newhdr; hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED); if (WARN_ON(skb_tailroom(skb) < IEEE80211_WEP_ICV_LEN || skb_headroom(skb) < IEEE80211_WEP_IV_LEN)) return NULL; hdrlen = ieee80211_hdrlen(hdr->frame_control); newhdr = skb_push(skb, IEEE80211_WEP_IV_LEN); memmove(newhdr, newhdr + IEEE80211_WEP_IV_LEN, hdrlen); /* the HW only needs room for the IV, but not the actual IV */ if (info->control.hw_key && (info->control.hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) return newhdr + hdrlen; skb_set_network_header(skb, skb_network_offset(skb) + IEEE80211_WEP_IV_LEN); ieee80211_wep_get_iv(local, keylen, keyidx, 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 + IEEE80211_WEP_IV_LEN, skb->data, hdrlen); skb_pull(skb, IEEE80211_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)) */ int ieee80211_wep_encrypt_data(struct crypto_cipher *tfm, u8 *rc4key, size_t klen, u8 *data, size_t data_len) { __le32 icv; int i; if (IS_ERR(tfm)) return -1; icv = cpu_to_le32(~crc32_le(~0, data, data_len)); put_unaligned(icv, (__le32 *)(data + data_len)); crypto_cipher_setkey(tfm, rc4key, klen); for (i = 0; i < data_len + IEEE80211_WEP_ICV_LEN; i++) crypto_cipher_encrypt_one(tfm, data + i, data + i); return 0; } /* 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, const u8 *key, int keylen, int keyidx) { u8 *iv; size_t len; u8 rc4key[3 + WLAN_KEY_LEN_WEP104]; iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx); if (!iv) return -1; len = skb->len - (iv + IEEE80211_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, keylen); /* Add room for ICV */ skb_put(skb, IEEE80211_WEP_ICV_LEN); return ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, keylen + 3, iv + IEEE80211_WEP_IV_LEN, len); } /* 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_cipher *tfm, u8 *rc4key, size_t klen, u8 *data, size_t data_len) { __le32 crc; int i; if (IS_ERR(tfm)) return -1; crypto_cipher_setkey(tfm, rc4key, klen); for (i = 0; i < data_len + IEEE80211_WEP_ICV_LEN; i++) crypto_cipher_decrypt_one(tfm, data + i, data + i); crc = cpu_to_le32(~crc32_le(~0, data, data_len)); if (memcmp(&crc, data + data_len, IEEE80211_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. */ static int ieee80211_wep_decrypt(struct ieee80211_local *local, struct sk_buff *skb, struct ieee80211_key *key) { u32 klen; u8 rc4key[3 + WLAN_KEY_LEN_WEP104]; 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 + IEEE80211_WEP_IV_LEN + IEEE80211_WEP_ICV_LEN) return -1; len = skb->len - hdrlen - IEEE80211_WEP_IV_LEN - IEEE80211_WEP_ICV_LEN; keyidx = skb->data[hdrlen + 3] >> 6; if (!key || keyidx != key->conf.keyidx) return -1; klen = 3 + key->conf.keylen; /* 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 + IEEE80211_WEP_IV_LEN, len)) ret = -1; /* Trim ICV */ skb_trim(skb, skb->len - IEEE80211_WEP_ICV_LEN); /* Remove IV */ memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen); skb_pull(skb, IEEE80211_WEP_IV_LEN); return ret; } ieee80211_rx_result ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx) { struct sk_buff *skb = rx->skb; struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb); struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; __le16 fc = hdr->frame_control; if (!ieee80211_is_data(fc) && !ieee80211_is_auth(fc)) return RX_CONTINUE; if (!(status->flag & RX_FLAG_DECRYPTED)) { if (skb_linearize(rx->skb)) return RX_DROP_UNUSABLE; if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key)) return RX_DROP_UNUSABLE; } else if (!(status->flag & RX_FLAG_IV_STRIPPED)) { if (!pskb_may_pull(rx->skb, ieee80211_hdrlen(fc) + IEEE80211_WEP_IV_LEN)) return RX_DROP_UNUSABLE; ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key); /* remove ICV */ if (pskb_trim(rx->skb, rx->skb->len - IEEE80211_WEP_ICV_LEN)) return RX_DROP_UNUSABLE; } 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); struct ieee80211_key_conf *hw_key = info->control.hw_key; if (!hw_key) { if (ieee80211_wep_encrypt(tx->local, skb, tx->key->conf.key, tx->key->conf.keylen, tx->key->conf.keyidx)) return -1; } else if ((hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV) || (hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) { if (!ieee80211_wep_add_iv(tx->local, skb, tx->key->conf.keylen, tx->key->conf.keyidx)) 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_queue_walk(&tx->skbs, skb) { if (wep_encrypt_skb(tx, skb) < 0) { I802_DEBUG_INC(tx->local->tx_handlers_drop_wep); return TX_DROP; } } return TX_CONTINUE; }