ieee80211_crypto_wep.c

Linux下wifi实现

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};

static int
wep_encrypt(struct ieee80211_key *key, struct sk_buff *skb0, 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 sk_buff *skb = skb0;
	u_int8_t rc4key[IEEE80211_WEP_IVLEN + IEEE80211_KEYBUF_SIZE];
	uint8_t *icv;
	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, skb->data + 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 = skb->len - off;

	/* Compute CRC32 over unencrypted data and apply RC4 to data */
	crc = ~0;
	i = j = 0;
	pos = skb->data + off;
	buflen = skb->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 (skb->next == NULL) {
			if (data_len != 0) {		/* out of data */
#ifdef IEEE80211_DEBUG
				const struct ieee80211_frame *wh =
				    (const struct ieee80211_frame *) skb0->data;
#endif
				IEEE80211_NOTE_MAC(vap, IEEE80211_MSG_CRYPTO,
					wh->i_addr2,
					"out of data for WEP (data_len %lu)",
					(unsigned long) data_len);
				return 0;
			}
			break;
		}
		skb = skb->next;
		pos = skb->data;
		buflen = skb->len;
	}
	crc = ~crc;

	if (skb_tailroom(skb) < wep.ic_trailer) {
#ifdef IEEE80211_DEBUG
		const struct ieee80211_frame *wh =
			(const struct ieee80211_frame *) skb0->data;
#endif
		/* NB: should not happen */
		IEEE80211_NOTE_MAC(ctx->wc_vap, IEEE80211_MSG_CRYPTO,
			wh->i_addr1, "no room for %s ICV, tailroom %u",
			wep.ic_name, skb_tailroom(skb));
		/* XXX statistic */
		return 0;
	}
	/* Append little-endian CRC32 and encrypt it to produce ICV */
	icv = skb_put(skb, IEEE80211_WEP_CRCLEN);
	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 1;
#undef S_SWAP
}

static int
wep_decrypt(struct ieee80211_key *key, struct sk_buff *skb0, 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 sk_buff *skb = skb0;
	u_int8_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, skb->data + 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 = skb->len - (off + wep.ic_trailer),

	/* Compute CRC32 over unencrypted data and apply RC4 to data */
	crc = ~0;
	i = j = 0;
	pos = skb->data + off;
	buflen = skb->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++;
		}
		skb = skb->next;
		if (skb == NULL) {
			if (data_len != 0) {		/* out of data */
#ifdef IEEE80211_DEBUG
				const struct ieee80211_frame *wh =
					(const struct ieee80211_frame *) skb0->data;
#endif
				IEEE80211_NOTE_MAC(vap, IEEE80211_MSG_CRYPTO,
					wh->i_addr2,
					"out of data for WEP (data_len %lu)",
					(unsigned long) data_len);
				return 0;
			}
			break;
		}
		pos = skb->data;
		buflen = skb->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 sk_buf */
		if ((icv[k] ^ S[(S[i] + S[j]) & 0xff]) != *pos++) {
			/* ICV mismatch - drop frame */
			return 0;
		}
	}
	return 1;
#undef S_SWAP
}

/*
 * Module glue.
 */

MODULE_AUTHOR("Errno Consulting, Sam Leffler");
MODULE_DESCRIPTION("802.11 wireless support: WEP cipher");
#ifdef MODULE_LICENSE
MODULE_LICENSE("Dual BSD/GPL");
#endif

static int __init
init_crypto_wep(void)
{
	ieee80211_crypto_register(&wep);
	return 0;
}
module_init(init_crypto_wep);

static void __exit
exit_crypto_wep(void)
{
	ieee80211_crypto_unregister(&wep);
}
module_exit(exit_crypto_wep);