xref: /openbmc/linux/drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_ccmp.c (revision 17c8129e)

// SPDX-License-Identifier: GPL-2.0
/*
 * Host AP crypt: host-based CCMP encryption implementation for Host AP driver
 *
 * Copyright (c) 2003-2004, Jouni Malinen <jkmaline@cc.hut.fi>
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/random.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/if_ether.h>
#include <linux/if_arp.h>
#include <linux/string.h>
#include <linux/wireless.h>

#include "ieee80211.h"

#include <linux/crypto.h>
#include <crypto/aead.h>
    #include <linux/scatterlist.h>

MODULE_AUTHOR("Jouni Malinen");
MODULE_DESCRIPTION("Host AP crypt: CCMP");
MODULE_LICENSE("GPL");

#define AES_BLOCK_LEN 16
#define CCMP_HDR_LEN 8
#define CCMP_MIC_LEN 8
#define CCMP_TK_LEN 16
#define CCMP_PN_LEN 6

struct ieee80211_ccmp_data {
	u8 key[CCMP_TK_LEN];
	int key_set;

	u8 tx_pn[CCMP_PN_LEN];
	u8 rx_pn[CCMP_PN_LEN];

	u32 dot11RSNAStatsCCMPFormatErrors;
	u32 dot11RSNAStatsCCMPReplays;
	u32 dot11RSNAStatsCCMPDecryptErrors;

	int key_idx;

	struct crypto_aead *tfm;

	/* scratch buffers for virt_to_page() (crypto API) */
	u8 tx_aad[2 * AES_BLOCK_LEN];
	u8 rx_aad[2 * AES_BLOCK_LEN];
};

static void *ieee80211_ccmp_init(int key_idx)
{
	struct ieee80211_ccmp_data *priv;

	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
	if (!priv)
		goto fail;
	priv->key_idx = key_idx;

	priv->tfm = crypto_alloc_aead("ccm(aes)", 0, CRYPTO_ALG_ASYNC);
	if (IS_ERR(priv->tfm)) {
		pr_debug("ieee80211_crypt_ccmp: could not allocate crypto API aes\n");
		priv->tfm = NULL;
		goto fail;
	}

	return priv;

fail:
	if (priv) {
		if (priv->tfm)
			crypto_free_aead(priv->tfm);
		kfree(priv);
	}

	return NULL;
}

static void ieee80211_ccmp_deinit(void *priv)
{
	struct ieee80211_ccmp_data *_priv = priv;

	if (_priv && _priv->tfm)
		crypto_free_aead(_priv->tfm);
	kfree(priv);
}

static int ccmp_init_iv_and_aad(struct rtl_80211_hdr_4addr *hdr,
			     u8 *pn, u8 *iv, u8 *aad)
{
	u8 *pos, qc = 0;
	size_t aad_len;
	u16 fc;
	int a4_included, qc_included;

	fc = le16_to_cpu(hdr->frame_ctl);
	a4_included = ((fc & (IEEE80211_FCTL_TODS | IEEE80211_FCTL_FROMDS)) ==
		       (IEEE80211_FCTL_TODS | IEEE80211_FCTL_FROMDS));
	/* qc_included = ((WLAN_FC_GET_TYPE(fc) == IEEE80211_FTYPE_DATA) &&
	 *	       (WLAN_FC_GET_STYPE(fc) & 0x08));
	 */
	/* fixed by David :2006.9.6 */
	qc_included = (WLAN_FC_GET_TYPE(fc) == IEEE80211_FTYPE_DATA) &&
		       (WLAN_FC_GET_STYPE(fc) & 0x80);
	aad_len = 22;
	if (a4_included)
		aad_len += 6;
	if (qc_included) {
		pos = (u8 *)&hdr->addr4;
		if (a4_included)
			pos += 6;
		qc = *pos & 0x0f;
		aad_len += 2;
	}

	/* In CCM, the initial vectors (IV) used for CTR mode encryption and CBC
	 * mode authentication are not allowed to collide, yet both are derived
	 * from the same vector. We only set L := 1 here to indicate that the
	 * data size can be represented in (L+1) bytes. The CCM layer will take
	 * care of storing the data length in the top (L+1) bytes and setting
	 * and clearing the other bits as is required to derive the two IVs.
	 */
	iv[0] = 0x1;

	/* Nonce: QC | A2 | PN */
	iv[1] = qc;
	memcpy(iv + 2, hdr->addr2, ETH_ALEN);
	memcpy(iv + 8, pn, CCMP_PN_LEN);

	/* AAD:
	 * FC with bits 4..6 and 11..13 masked to zero; 14 is always one
	 * A1 | A2 | A3
	 * SC with bits 4..15 (seq#) masked to zero
	 * A4 (if present)
	 * QC (if present)
	 */
	pos = (u8 *)hdr;
	aad[0] = pos[0] & 0x8f;
	aad[1] = pos[1] & 0xc7;
	memcpy(&aad[2], &hdr->addr1, ETH_ALEN);
	memcpy(&aad[8], &hdr->addr2, ETH_ALEN);
	memcpy(&aad[14], &hdr->addr3, ETH_ALEN);
	pos = (u8 *)&hdr->seq_ctl;
	aad[20] = pos[0] & 0x0f;
	aad[21] = 0; /* all bits masked */
	memset(aad + 22, 0, 8);
	if (a4_included)
		memcpy(aad + 22, hdr->addr4, ETH_ALEN);
	if (qc_included) {
		aad[a4_included ? 28 : 22] = qc;
		/* rest of QC masked */
	}

	return aad_len;
}

static int ieee80211_ccmp_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
{
	struct ieee80211_ccmp_data *key = priv;
	int i;
	u8 *pos;
	struct rtl_80211_hdr_4addr *hdr;
	struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);

	if (skb_headroom(skb) < CCMP_HDR_LEN ||
	    skb_tailroom(skb) < CCMP_MIC_LEN ||
	    skb->len < hdr_len)
		return -1;

	pos = skb_push(skb, CCMP_HDR_LEN);
	memmove(pos, pos + CCMP_HDR_LEN, hdr_len);
	pos += hdr_len;
	/* mic = skb_put(skb, CCMP_MIC_LEN); */

	i = CCMP_PN_LEN - 1;
	while (i >= 0) {
		key->tx_pn[i]++;
		if (key->tx_pn[i] != 0)
			break;
		i--;
	}

	*pos++ = key->tx_pn[5];
	*pos++ = key->tx_pn[4];
	*pos++ = 0;
	*pos++ = (key->key_idx << 6) | BIT(5) /* Ext IV included */;
	*pos++ = key->tx_pn[3];
	*pos++ = key->tx_pn[2];
	*pos++ = key->tx_pn[1];
	*pos++ = key->tx_pn[0];

	hdr = (struct rtl_80211_hdr_4addr *)skb->data;
	if (!tcb_desc->bHwSec) {
		struct aead_request *req;
		struct scatterlist sg[2];
		u8 *aad = key->tx_aad;
		u8 iv[AES_BLOCK_LEN];
		int aad_len, ret;
		size_t data_len = skb->len - hdr_len - CCMP_HDR_LEN;

		req = aead_request_alloc(key->tfm, GFP_ATOMIC);
		if (!req)
			return -ENOMEM;

		aad_len = ccmp_init_iv_and_aad(hdr, key->tx_pn, iv, aad);

		skb_put(skb, CCMP_MIC_LEN);

		sg_init_table(sg, 2);
		sg_set_buf(&sg[0], aad, aad_len);
		sg_set_buf(&sg[1], skb->data + hdr_len + CCMP_HDR_LEN,
			   data_len + CCMP_MIC_LEN);

		aead_request_set_callback(req, 0, NULL, NULL);
		aead_request_set_ad(req, aad_len);
		aead_request_set_crypt(req, sg, sg, data_len, iv);

		ret = crypto_aead_encrypt(req);
		aead_request_free(req);

		return ret;
	}
	return 0;
}

static int ieee80211_ccmp_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
{
	struct ieee80211_ccmp_data *key = priv;
	u8 keyidx, *pos;
	struct rtl_80211_hdr_4addr *hdr;
	struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
	u8 pn[6];

	if (skb->len < hdr_len + CCMP_HDR_LEN + CCMP_MIC_LEN) {
		key->dot11RSNAStatsCCMPFormatErrors++;
		return -1;
	}

	hdr = (struct rtl_80211_hdr_4addr *)skb->data;
	pos = skb->data + hdr_len;
	keyidx = pos[3];
	if (!(keyidx & BIT(5))) {
		if (net_ratelimit()) {
			netdev_dbg(skb->dev, "CCMP: received packet without ExtIV flag from %pM\n",
				   hdr->addr2);
		}
		key->dot11RSNAStatsCCMPFormatErrors++;
		return -2;
	}
	keyidx >>= 6;
	if (key->key_idx != keyidx) {
		netdev_dbg(skb->dev, "CCMP: RX tkey->key_idx=%d frame keyidx=%d priv=%p\n",
			   key->key_idx, keyidx, priv);
		return -6;
	}
	if (!key->key_set) {
		if (net_ratelimit()) {
			netdev_dbg(skb->dev, "CCMP: received packet from %pM with keyid=%d that does not have a configured key\n",
				   hdr->addr2, keyidx);
		}
		return -3;
	}

	pn[0] = pos[7];
	pn[1] = pos[6];
	pn[2] = pos[5];
	pn[3] = pos[4];
	pn[4] = pos[1];
	pn[5] = pos[0];
	pos += 8;

	if (memcmp(pn, key->rx_pn, CCMP_PN_LEN) <= 0) {
		if (net_ratelimit()) {
			netdev_dbg(skb->dev, "CCMP: replay detected: STA=%pM previous PN %pm received PN %pm\n",
				   hdr->addr2, key->rx_pn, pn);
		}
		key->dot11RSNAStatsCCMPReplays++;
		return -4;
	}
	if (!tcb_desc->bHwSec) {
		struct aead_request *req;
		struct scatterlist sg[2];
		u8 *aad = key->rx_aad;
		u8 iv[AES_BLOCK_LEN];
		int aad_len, ret;
		size_t data_len = skb->len - hdr_len - CCMP_HDR_LEN;

		req = aead_request_alloc(key->tfm, GFP_ATOMIC);
		if (!req)
			return -ENOMEM;

		aad_len = ccmp_init_iv_and_aad(hdr, pn, iv, aad);

		sg_init_table(sg, 2);
		sg_set_buf(&sg[0], aad, aad_len);
		sg_set_buf(&sg[1], pos, data_len);

		aead_request_set_callback(req, 0, NULL, NULL);
		aead_request_set_ad(req, aad_len);
		aead_request_set_crypt(req, sg, sg, data_len, iv);

		ret = crypto_aead_decrypt(req);
		aead_request_free(req);

		if (ret) {
			if (net_ratelimit()) {
				netdev_dbg(skb->dev, "CCMP: decrypt failed: STA=%pM\n",
					   hdr->addr2);
			}
			key->dot11RSNAStatsCCMPDecryptErrors++;
			return -5;
		}

		memcpy(key->rx_pn, pn, CCMP_PN_LEN);
	}
	/* Remove hdr and MIC */
	memmove(skb->data + CCMP_HDR_LEN, skb->data, hdr_len);
	skb_pull(skb, CCMP_HDR_LEN);
	skb_trim(skb, skb->len - CCMP_MIC_LEN);

	return keyidx;
}

static int ieee80211_ccmp_set_key(void *key, int len, u8 *seq, void *priv)
{
	struct ieee80211_ccmp_data *data = priv;
	int keyidx;
	struct crypto_aead *tfm = data->tfm;

	keyidx = data->key_idx;
	memset(data, 0, sizeof(*data));
	data->key_idx = keyidx;
	if (len == CCMP_TK_LEN) {
		memcpy(data->key, key, CCMP_TK_LEN);
		data->key_set = 1;
		if (seq) {
			data->rx_pn[0] = seq[5];
			data->rx_pn[1] = seq[4];
			data->rx_pn[2] = seq[3];
			data->rx_pn[3] = seq[2];
			data->rx_pn[4] = seq[1];
			data->rx_pn[5] = seq[0];
		}
		if (crypto_aead_setauthsize(tfm, CCMP_MIC_LEN) ||
		    crypto_aead_setkey(tfm, data->key, CCMP_TK_LEN))
			return -1;
	} else if (len == 0) {
		data->key_set = 0;
	} else {
		return -1;
	}

	return 0;
}

static int ieee80211_ccmp_get_key(void *key, int len, u8 *seq, void *priv)
{
	struct ieee80211_ccmp_data *data = priv;

	if (len < CCMP_TK_LEN)
		return 0;

	if (!data->key_set)
		return 0;
	memcpy(key, data->key, CCMP_TK_LEN);

	if (seq) {
		seq[0] = data->tx_pn[5];
		seq[1] = data->tx_pn[4];
		seq[2] = data->tx_pn[3];
		seq[3] = data->tx_pn[2];
		seq[4] = data->tx_pn[1];
		seq[5] = data->tx_pn[0];
	}

	return CCMP_TK_LEN;
}

static char *ieee80211_ccmp_print_stats(char *p, void *priv)
{
	struct ieee80211_ccmp_data *ccmp = priv;

	p += sprintf(p, "key[%d] alg=CCMP key_set=%d tx_pn=%pm rx_pn=%pm format_errors=%d replays=%d decrypt_errors=%d\n",
		     ccmp->key_idx, ccmp->key_set,
		     ccmp->tx_pn, ccmp->rx_pn,
		     ccmp->dot11RSNAStatsCCMPFormatErrors,
		     ccmp->dot11RSNAStatsCCMPReplays,
		     ccmp->dot11RSNAStatsCCMPDecryptErrors);

	return p;
}

static struct ieee80211_crypto_ops ieee80211_crypt_ccmp = {
	.name			= "CCMP",
	.init			= ieee80211_ccmp_init,
	.deinit			= ieee80211_ccmp_deinit,
	.encrypt_mpdu		= ieee80211_ccmp_encrypt,
	.decrypt_mpdu		= ieee80211_ccmp_decrypt,
	.encrypt_msdu		= NULL,
	.decrypt_msdu		= NULL,
	.set_key		= ieee80211_ccmp_set_key,
	.get_key		= ieee80211_ccmp_get_key,
	.print_stats		= ieee80211_ccmp_print_stats,
	.extra_prefix_len	= CCMP_HDR_LEN,
	.extra_postfix_len	= CCMP_MIC_LEN,
	.owner			= THIS_MODULE,
};

int __init ieee80211_crypto_ccmp_init(void)
{
	return ieee80211_register_crypto_ops(&ieee80211_crypt_ccmp);
}

void ieee80211_crypto_ccmp_exit(void)
{
	ieee80211_unregister_crypto_ops(&ieee80211_crypt_ccmp);
}