ieee80211_crypt_tkip.c

Source for the 802.11 (wireless) network stack for Linux

static int ieee80211_tkip_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
{
	struct ieee80211_tkip_data *tkey = priv;
	u8 rc4key[16];
	u8 keyidx, *pos;
	u32 iv32;
	u16 iv16;
	struct ieee80211_hdr_4addr *hdr;
	u8 icv[4];
	u32 crc;
	struct scatterlist sg;
	int plen;

	hdr = (struct ieee80211_hdr_4addr *)skb->data;

	if (tkey->flags & IEEE80211_CRYPTO_TKIP_COUNTERMEASURES) {
		if (net_ratelimit()) {
			printk(KERN_DEBUG "TKIP countermeasures: dropped "
			       "received packet from " MAC_FMT "\n",
			       MAC_ARG(hdr->addr2));
		}
		return -1;
	}

	if (skb->len < hdr_len + 8 + 4)
		return -1;

	pos = skb->data + hdr_len;
	keyidx = pos[3];
	if (!(keyidx & (1 << 5))) {
		if (net_ratelimit()) {
			printk(KERN_DEBUG "TKIP: received packet without ExtIV"
			       " flag from " MAC_FMT "\n", MAC_ARG(hdr->addr2));
		}
		return -2;
	}
	keyidx >>= 6;
	if (tkey->key_idx != keyidx) {
		printk(KERN_DEBUG "TKIP: RX tkey->key_idx=%d frame "
		       "keyidx=%d priv=%p\n", tkey->key_idx, keyidx, priv);
		return -6;
	}
	if (!tkey->key_set) {
		if (net_ratelimit()) {
			printk(KERN_DEBUG "TKIP: received packet from " MAC_FMT
			       " with keyid=%d that does not have a configured"
			       " key\n", MAC_ARG(hdr->addr2), keyidx);
		}
		return -3;
	}
	iv16 = (pos[0] << 8) | pos[2];
	iv32 = pos[4] | (pos[5] << 8) | (pos[6] << 16) | (pos[7] << 24);
	pos += 8;

	if (iv32 < tkey->rx_iv32 ||
	    (iv32 == tkey->rx_iv32 && iv16 <= tkey->rx_iv16)) {
		if (net_ratelimit()) {
			printk(KERN_DEBUG "TKIP: replay detected: STA=" MAC_FMT
			       " previous TSC %08x%04x received TSC "
			       "%08x%04x\n", MAC_ARG(hdr->addr2),
			       tkey->rx_iv32, tkey->rx_iv16, iv32, iv16);
		}
		tkey->dot11RSNAStatsTKIPReplays++;
		return -4;
	}

	if (iv32 != tkey->rx_iv32 || !tkey->rx_phase1_done) {
		tkip_mixing_phase1(tkey->rx_ttak, tkey->key, hdr->addr2, iv32);
		tkey->rx_phase1_done = 1;
	}
	tkip_mixing_phase2(rc4key, tkey->key, tkey->rx_ttak, iv16);

	plen = skb->len - hdr_len - 12;

	crypto_cipher_setkey(tkey->tfm_arc4, rc4key, 16);
	sg.page = virt_to_page(pos);
	sg.offset = offset_in_page(pos);
	sg.length = plen + 4;
	crypto_cipher_decrypt(tkey->tfm_arc4, &sg, &sg, plen + 4);

	crc = ~crc32_le(~0, pos, plen);
	icv[0] = crc;
	icv[1] = crc >> 8;
	icv[2] = crc >> 16;
	icv[3] = crc >> 24;
	if (memcmp(icv, pos + plen, 4) != 0) {
		if (iv32 != tkey->rx_iv32) {
			/* Previously cached Phase1 result was already lost, so
			 * it needs to be recalculated for the next packet. */
			tkey->rx_phase1_done = 0;
		}
		if (net_ratelimit()) {
			printk(KERN_DEBUG "TKIP: ICV error detected: STA="
			       MAC_FMT "\n", MAC_ARG(hdr->addr2));
		}
		tkey->dot11RSNAStatsTKIPICVErrors++;
		return -5;
	}

	/* Update real counters only after Michael MIC verification has
	 * completed */
	tkey->rx_iv32_new = iv32;
	tkey->rx_iv16_new = iv16;

	/* Remove IV and ICV */
	memmove(skb->data + 8, skb->data, hdr_len);
	skb_pull(skb, 8);
	skb_trim(skb, skb->len - 4);

	return keyidx;
}

static int michael_mic(struct ieee80211_tkip_data *tkey, u8 * key, u8 * hdr,
		       u8 * data, size_t data_len, u8 * mic)
{
	struct scatterlist sg[2];

	if (tkey->tfm_michael == NULL) {
		printk(KERN_WARNING "michael_mic: tfm_michael == NULL\n");
		return -1;
	}
	sg[0].page = virt_to_page(hdr);
	sg[0].offset = offset_in_page(hdr);
	sg[0].length = 16;

	sg[1].page = virt_to_page(data);
	sg[1].offset = offset_in_page(data);
	sg[1].length = data_len;

	crypto_digest_init(tkey->tfm_michael);
	crypto_digest_setkey(tkey->tfm_michael, key, 8);
	crypto_digest_update(tkey->tfm_michael, sg, 2);
	crypto_digest_final(tkey->tfm_michael, mic);

	return 0;
}

static void michael_mic_hdr(struct sk_buff *skb, u8 * hdr)
{
	struct ieee80211_hdr_4addr *hdr11;

	hdr11 = (struct ieee80211_hdr_4addr *)skb->data;
	switch (le16_to_cpu(hdr11->frame_ctl) &
		(IEEE80211_FCTL_FROMDS | IEEE80211_FCTL_TODS)) {
	case IEEE80211_FCTL_TODS:
		memcpy(hdr, hdr11->addr3, ETH_ALEN);	/* DA */
		memcpy(hdr + ETH_ALEN, hdr11->addr2, ETH_ALEN);	/* SA */
		break;
	case IEEE80211_FCTL_FROMDS:
		memcpy(hdr, hdr11->addr1, ETH_ALEN);	/* DA */
		memcpy(hdr + ETH_ALEN, hdr11->addr3, ETH_ALEN);	/* SA */
		break;
	case IEEE80211_FCTL_FROMDS | IEEE80211_FCTL_TODS:
		memcpy(hdr, hdr11->addr3, ETH_ALEN);	/* DA */
		memcpy(hdr + ETH_ALEN, hdr11->addr4, ETH_ALEN);	/* SA */
		break;
	case 0:
		memcpy(hdr, hdr11->addr1, ETH_ALEN);	/* DA */
		memcpy(hdr + ETH_ALEN, hdr11->addr2, ETH_ALEN);	/* SA */
		break;
	}

	hdr[12] = 0;		/* priority */
	hdr[13] = hdr[14] = hdr[15] = 0;	/* reserved */
}

static int ieee80211_michael_mic_add(struct sk_buff *skb, int hdr_len,
				     void *priv)
{
	struct ieee80211_tkip_data *tkey = priv;
	u8 *pos;

	if (skb_tailroom(skb) < 8 || skb->len < hdr_len) {
		printk(KERN_DEBUG "Invalid packet for Michael MIC add "
		       "(tailroom=%d hdr_len=%d skb->len=%d)\n",
		       skb_tailroom(skb), hdr_len, skb->len);
		return -1;
	}

	michael_mic_hdr(skb, tkey->tx_hdr);
	pos = skb_put(skb, 8);
	if (michael_mic(tkey, &tkey->key[16], tkey->tx_hdr,
			skb->data + hdr_len, skb->len - 8 - hdr_len, pos))
		return -1;

	return 0;
}

static void ieee80211_michael_mic_failure(struct net_device *dev,
					  struct ieee80211_hdr_4addr *hdr,
					  int keyidx)
{
#if WIRELESS_EXT >= 18
	union iwreq_data wrqu;
	struct iw_michaelmicfailure ev;

	/* TODO: needed parameters: count, keyid, key type, TSC */
	memset(&ev, 0, sizeof(ev));
	ev.flags = keyidx & IW_MICFAILURE_KEY_ID;
	if (hdr->addr1[0] & 0x01)
		ev.flags |= IW_MICFAILURE_GROUP;
	else
		ev.flags |= IW_MICFAILURE_PAIRWISE;
	ev.src_addr.sa_family = ARPHRD_ETHER;
	memcpy(ev.src_addr.sa_data, hdr->addr2, ETH_ALEN);
	memset(&wrqu, 0, sizeof(wrqu));
	wrqu.data.length = sizeof(ev);
	wireless_send_event(dev, IWEVMICHAELMICFAILURE, &wrqu, (char *)&ev);
#endif
}

static int ieee80211_michael_mic_verify(struct sk_buff *skb, int keyidx,
					int hdr_len, void *priv)
{
	struct ieee80211_tkip_data *tkey = priv;
	u8 mic[8];

	if (!tkey->key_set)
		return -1;

	michael_mic_hdr(skb, tkey->rx_hdr);
	if (michael_mic(tkey, &tkey->key[24], tkey->rx_hdr,
			skb->data + hdr_len, skb->len - 8 - hdr_len, mic))
		return -1;
	if (memcmp(mic, skb->data + skb->len - 8, 8) != 0) {
		struct ieee80211_hdr_4addr *hdr;
		hdr = (struct ieee80211_hdr_4addr *)skb->data;
		printk(KERN_DEBUG "%s: Michael MIC verification failed for "
		       "MSDU from " MAC_FMT " keyidx=%d\n",
		       skb->dev ? skb->dev->name : "N/A", MAC_ARG(hdr->addr2),
		       keyidx);
		if (skb->dev)
			ieee80211_michael_mic_failure(skb->dev, hdr, keyidx);
		tkey->dot11RSNAStatsTKIPLocalMICFailures++;
		return -1;
	}

	/* Update TSC counters for RX now that the packet verification has
	 * completed. */
	tkey->rx_iv32 = tkey->rx_iv32_new;
	tkey->rx_iv16 = tkey->rx_iv16_new;

	skb_trim(skb, skb->len - 8);

	return 0;
}

static int ieee80211_tkip_set_key(void *key, int len, u8 * seq, void *priv)
{
	struct ieee80211_tkip_data *tkey = priv;
	int keyidx;
	struct crypto_tfm *tfm = tkey->tfm_michael;
	struct crypto_tfm *tfm2 = tkey->tfm_arc4;

	keyidx = tkey->key_idx;
	memset(tkey, 0, sizeof(*tkey));
	tkey->key_idx = keyidx;
	tkey->tfm_michael = tfm;
	tkey->tfm_arc4 = tfm2;
	if (len == TKIP_KEY_LEN) {
		memcpy(tkey->key, key, TKIP_KEY_LEN);
		tkey->key_set = 1;
		tkey->tx_iv16 = 1;	/* TSC is initialized to 1 */
		if (seq) {
			tkey->rx_iv32 = (seq[5] << 24) | (seq[4] << 16) |
			    (seq[3] << 8) | seq[2];
			tkey->rx_iv16 = (seq[1] << 8) | seq[0];
		}
	} else if (len == 0)
		tkey->key_set = 0;
	else
		return -1;

	return 0;
}

static int ieee80211_tkip_get_key(void *key, int len, u8 * seq, void *priv)
{
	struct ieee80211_tkip_data *tkey = priv;

	if (len < TKIP_KEY_LEN)
		return -1;

	if (!tkey->key_set)
		return 0;
	memcpy(key, tkey->key, TKIP_KEY_LEN);

	if (seq) {
		/* Return the sequence number of the last transmitted frame. */
		u16 iv16 = tkey->tx_iv16;
		u32 iv32 = tkey->tx_iv32;
		if (iv16 == 0)
			iv32--;
		iv16--;
		seq[0] = tkey->tx_iv16;
		seq[1] = tkey->tx_iv16 >> 8;
		seq[2] = tkey->tx_iv32;
		seq[3] = tkey->tx_iv32 >> 8;
		seq[4] = tkey->tx_iv32 >> 16;
		seq[5] = tkey->tx_iv32 >> 24;
	}

	return TKIP_KEY_LEN;
}

static char *ieee80211_tkip_print_stats(char *p, void *priv)
{
	struct ieee80211_tkip_data *tkip = priv;
	p += sprintf(p, "key[%d] alg=TKIP key_set=%d "
		     "tx_pn=%02x%02x%02x%02x%02x%02x "
		     "rx_pn=%02x%02x%02x%02x%02x%02x "
		     "replays=%d icv_errors=%d local_mic_failures=%d\n",
		     tkip->key_idx, tkip->key_set,
		     (tkip->tx_iv32 >> 24) & 0xff,
		     (tkip->tx_iv32 >> 16) & 0xff,
		     (tkip->tx_iv32 >> 8) & 0xff,
		     tkip->tx_iv32 & 0xff,
		     (tkip->tx_iv16 >> 8) & 0xff,
		     tkip->tx_iv16 & 0xff,
		     (tkip->rx_iv32 >> 24) & 0xff,
		     (tkip->rx_iv32 >> 16) & 0xff,
		     (tkip->rx_iv32 >> 8) & 0xff,
		     tkip->rx_iv32 & 0xff,
		     (tkip->rx_iv16 >> 8) & 0xff,
		     tkip->rx_iv16 & 0xff,
		     tkip->dot11RSNAStatsTKIPReplays,
		     tkip->dot11RSNAStatsTKIPICVErrors,
		     tkip->dot11RSNAStatsTKIPLocalMICFailures);
	return p;
}

static struct ieee80211_crypto_ops ieee80211_crypt_tkip = {
	.name = "TKIP",
	.init = ieee80211_tkip_init,
	.deinit = ieee80211_tkip_deinit,
	.encrypt_mpdu = ieee80211_tkip_encrypt,
	.decrypt_mpdu = ieee80211_tkip_decrypt,
	.encrypt_msdu = ieee80211_michael_mic_add,
	.decrypt_msdu = ieee80211_michael_mic_verify,
	.set_key = ieee80211_tkip_set_key,
	.get_key = ieee80211_tkip_get_key,
	.print_stats = ieee80211_tkip_print_stats,
	.extra_mpdu_prefix_len = 4 + 4,	/* IV + ExtIV */
	.extra_mpdu_postfix_len = 4,	/* ICV */
	.extra_msdu_postfix_len = 8,	/* MIC */
	.get_flags = ieee80211_tkip_get_flags,
	.set_flags = ieee80211_tkip_set_flags,
	.owner = THIS_MODULE,
};

static int __init ieee80211_crypto_tkip_init(void)
{
	return ieee80211_register_crypto_ops(&ieee80211_crypt_tkip);
}

static void __exit ieee80211_crypto_tkip_exit(void)
{
	ieee80211_unregister_crypto_ops(&ieee80211_crypt_tkip);
}

module_init(ieee80211_crypto_tkip_init);
module_exit(ieee80211_crypto_tkip_exit);