/*

   * lib80211 crypt: host-based CCMP encryption implementation for lib80211

   *

   * Copyright (c) 2003-2004, Jouni Malinen <j@w1.fi>

   * Copyright (c) 2008, John W. Linville <linville@tuxdriver.com>

   *
   * 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. See README and COPYING for
   * more details.
   */

  #include <linux/kernel.h>

  #include <linux/err.h>

  #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 <asm/string.h>
  #include <linux/wireless.h>

  #include <linux/ieee80211.h>

  #include <linux/crypto.h>

  #include <net/lib80211.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 lib80211_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_cipher *tfm;

  
  	/* scratch buffers for virt_to_page() (crypto API) */
  	u8 tx_b0[AES_BLOCK_LEN], tx_b[AES_BLOCK_LEN],

  	    tx_e[AES_BLOCK_LEN], tx_s0[AES_BLOCK_LEN];

  	u8 rx_b0[AES_BLOCK_LEN], rx_b[AES_BLOCK_LEN], rx_a[AES_BLOCK_LEN];
  };

  static inline void lib80211_ccmp_aes_encrypt(struct crypto_cipher *tfm,

  					      const u8 pt[16], u8 ct[16])

  {

  	crypto_cipher_encrypt_one(tfm, ct, pt);

  }

  static void *lib80211_ccmp_init(int key_idx)

  {

  	struct lib80211_ccmp_data *priv;

  	priv = kzalloc(sizeof(*priv), GFP_ATOMIC);

  	if (priv == NULL)
  		goto fail;

  	priv->key_idx = key_idx;

  	priv->tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC);
  	if (IS_ERR(priv->tfm)) {

  		priv->tfm = NULL;

  		goto fail;
  	}
  
  	return priv;

        fail:

  	if (priv) {
  		if (priv->tfm)

  			crypto_free_cipher(priv->tfm);

  		kfree(priv);
  	}
  
  	return NULL;
  }

  static void lib80211_ccmp_deinit(void *priv)

  {

  	struct lib80211_ccmp_data *_priv = priv;

  	if (_priv && _priv->tfm)

  		crypto_free_cipher(_priv->tfm);

  	kfree(priv);
  }

  static inline void xor_block(u8 * b, u8 * a, size_t len)

  {
  	int i;
  	for (i = 0; i < len; i++)
  		b[i] ^= a[i];
  }

  static void ccmp_init_blocks(struct crypto_cipher *tfm,

  			     struct ieee80211_hdr *hdr,

  			     u8 * pn, size_t dlen, u8 * b0, u8 * auth, u8 * s0)

  {
  	u8 *pos, qc = 0;
  	size_t aad_len;

  	int a4_included, qc_included;
  	u8 aad[2 * AES_BLOCK_LEN];

  	a4_included = ieee80211_has_a4(hdr->frame_control);
  	qc_included = ieee80211_is_data_qos(hdr->frame_control);

  	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;
  	}
  
  	/* CCM Initial Block:
  	 * Flag (Include authentication header, M=3 (8-octet MIC),
  	 *       L=1 (2-octet Dlen))
  	 * Nonce: 0x00 | A2 | PN
  	 * Dlen */
  	b0[0] = 0x59;
  	b0[1] = qc;
  	memcpy(b0 + 2, hdr->addr2, ETH_ALEN);
  	memcpy(b0 + 8, pn, CCMP_PN_LEN);
  	b0[14] = (dlen >> 8) & 0xff;
  	b0[15] = dlen & 0xff;
  
  	/* 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] = 0;		/* aad_len >> 8 */

  	aad[1] = aad_len & 0xff;
  	aad[2] = pos[0] & 0x8f;
  	aad[3] = pos[1] & 0xc7;
  	memcpy(aad + 4, hdr->addr1, 3 * ETH_ALEN);

  	pos = (u8 *) & hdr->seq_ctrl;

  	aad[22] = pos[0] & 0x0f;

  	aad[23] = 0;		/* all bits masked */

  	memset(aad + 24, 0, 8);
  	if (a4_included)
  		memcpy(aad + 24, hdr->addr4, ETH_ALEN);
  	if (qc_included) {
  		aad[a4_included ? 30 : 24] = qc;
  		/* rest of QC masked */
  	}
  
  	/* Start with the first block and AAD */

  	lib80211_ccmp_aes_encrypt(tfm, b0, auth);

  	xor_block(auth, aad, AES_BLOCK_LEN);

  	lib80211_ccmp_aes_encrypt(tfm, auth, auth);

  	xor_block(auth, &aad[AES_BLOCK_LEN], AES_BLOCK_LEN);

  	lib80211_ccmp_aes_encrypt(tfm, auth, auth);

  	b0[0] &= 0x07;
  	b0[14] = b0[15] = 0;

  	lib80211_ccmp_aes_encrypt(tfm, b0, s0);

  }

  static int lib80211_ccmp_hdr(struct sk_buff *skb, int hdr_len,

  			      u8 *aeskey, int keylen, void *priv)

  {

  	struct lib80211_ccmp_data *key = priv;

  	int i;
  	u8 *pos;

  	if (skb_headroom(skb) < CCMP_HDR_LEN || skb->len < hdr_len)

  		return -1;

  	if (aeskey != NULL && keylen >= CCMP_TK_LEN)
  		memcpy(aeskey, key->key, CCMP_TK_LEN);

  	pos = skb_push(skb, CCMP_HDR_LEN);
  	memmove(pos, pos + CCMP_HDR_LEN, hdr_len);
  	pos += hdr_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) | (1 << 5) /* Ext IV included */ ;

  	*pos++ = key->tx_pn[3];
  	*pos++ = key->tx_pn[2];
  	*pos++ = key->tx_pn[1];
  	*pos++ = key->tx_pn[0];

  	return CCMP_HDR_LEN;
  }

  static int lib80211_ccmp_encrypt(struct sk_buff *skb, int hdr_len, void *priv)

  {

  	struct lib80211_ccmp_data *key = priv;

  	int data_len, i, blocks, last, len;
  	u8 *pos, *mic;

  	struct ieee80211_hdr *hdr;

  	u8 *b0 = key->tx_b0;
  	u8 *b = key->tx_b;
  	u8 *e = key->tx_e;
  	u8 *s0 = key->tx_s0;
  
  	if (skb_tailroom(skb) < CCMP_MIC_LEN || skb->len < hdr_len)
  		return -1;
  
  	data_len = skb->len - hdr_len;

  	len = lib80211_ccmp_hdr(skb, hdr_len, NULL, 0, priv);

  	if (len < 0)
  		return -1;
  
  	pos = skb->data + hdr_len + CCMP_HDR_LEN;

  	hdr = (struct ieee80211_hdr *)skb->data;

  	ccmp_init_blocks(key->tfm, hdr, key->tx_pn, data_len, b0, b, s0);

  	blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);

  	last = data_len % AES_BLOCK_LEN;
  
  	for (i = 1; i <= blocks; i++) {
  		len = (i == blocks && last) ? last : AES_BLOCK_LEN;
  		/* Authentication */
  		xor_block(b, pos, len);

  		lib80211_ccmp_aes_encrypt(key->tfm, b, b);

  		/* Encryption, with counter */
  		b0[14] = (i >> 8) & 0xff;
  		b0[15] = i & 0xff;

  		lib80211_ccmp_aes_encrypt(key->tfm, b0, e);

  		xor_block(pos, e, len);
  		pos += len;
  	}

  	mic = skb_put(skb, CCMP_MIC_LEN);

  	for (i = 0; i < CCMP_MIC_LEN; i++)
  		mic[i] = b[i] ^ s0[i];
  
  	return 0;
  }

  /*
   * deal with seq counter wrapping correctly.
   * refer to timer_after() for jiffies wrapping handling
   */
  static inline int ccmp_replay_check(u8 *pn_n, u8 *pn_o)
  {
  	u32 iv32_n, iv16_n;
  	u32 iv32_o, iv16_o;
  
  	iv32_n = (pn_n[0] << 24) | (pn_n[1] << 16) | (pn_n[2] << 8) | pn_n[3];
  	iv16_n = (pn_n[4] << 8) | pn_n[5];
  
  	iv32_o = (pn_o[0] << 24) | (pn_o[1] << 16) | (pn_o[2] << 8) | pn_o[3];
  	iv16_o = (pn_o[4] << 8) | pn_o[5];
  
  	if ((s32)iv32_n - (s32)iv32_o < 0 ||
  	    (iv32_n == iv32_o && iv16_n <= iv16_o))
  		return 1;
  	return 0;
  }

  static int lib80211_ccmp_decrypt(struct sk_buff *skb, int hdr_len, void *priv)

  {

  	struct lib80211_ccmp_data *key = priv;

  	u8 keyidx, *pos;

  	struct ieee80211_hdr *hdr;

  	u8 *b0 = key->rx_b0;
  	u8 *b = key->rx_b;
  	u8 *a = key->rx_a;
  	u8 pn[6];
  	int i, blocks, last, len;
  	size_t data_len = skb->len - hdr_len - CCMP_HDR_LEN - CCMP_MIC_LEN;
  	u8 *mic = skb->data + skb->len - CCMP_MIC_LEN;
  
  	if (skb->len < hdr_len + CCMP_HDR_LEN + CCMP_MIC_LEN) {
  		key->dot11RSNAStatsCCMPFormatErrors++;
  		return -1;
  	}

  	hdr = (struct ieee80211_hdr *)skb->data;

  	pos = skb->data + hdr_len;
  	keyidx = pos[3];
  	if (!(keyidx & (1 << 5))) {

  		net_dbg_ratelimited("CCMP: received packet without ExtIV flag from %pM
  ",
  				    hdr->addr2);

  		key->dot11RSNAStatsCCMPFormatErrors++;
  		return -2;
  	}
  	keyidx >>= 6;
  	if (key->key_idx != keyidx) {
  		printk(KERN_DEBUG "CCMP: RX tkey->key_idx=%d frame "
  		       "keyidx=%d priv=%p
  ", key->key_idx, keyidx, priv);
  		return -6;
  	}
  	if (!key->key_set) {

  		net_dbg_ratelimited("CCMP: received packet from %pM with keyid=%d that does not have a configured key
  ",
  				    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 (ccmp_replay_check(pn, key->rx_pn)) {

  #ifdef CONFIG_LIB80211_DEBUG

  		net_dbg_ratelimited("CCMP: replay detected: STA=%pM previous PN %02x%02x%02x%02x%02x%02x received PN %02x%02x%02x%02x%02x%02x
  ",
  				    hdr->addr2,
  				    key->rx_pn[0], key->rx_pn[1], key->rx_pn[2],
  				    key->rx_pn[3], key->rx_pn[4], key->rx_pn[5],
  				    pn[0], pn[1], pn[2], pn[3], pn[4], pn[5]);

  #endif

  		key->dot11RSNAStatsCCMPReplays++;
  		return -4;
  	}
  
  	ccmp_init_blocks(key->tfm, hdr, pn, data_len, b0, a, b);
  	xor_block(mic, b, CCMP_MIC_LEN);

  	blocks = DIV_ROUND_UP(data_len, AES_BLOCK_LEN);

  	last = data_len % AES_BLOCK_LEN;
  
  	for (i = 1; i <= blocks; i++) {
  		len = (i == blocks && last) ? last : AES_BLOCK_LEN;
  		/* Decrypt, with counter */
  		b0[14] = (i >> 8) & 0xff;
  		b0[15] = i & 0xff;

  		lib80211_ccmp_aes_encrypt(key->tfm, b0, b);

  		xor_block(pos, b, len);
  		/* Authentication */
  		xor_block(a, pos, len);

  		lib80211_ccmp_aes_encrypt(key->tfm, a, a);

  		pos += len;
  	}
  
  	if (memcmp(mic, a, CCMP_MIC_LEN) != 0) {

  		net_dbg_ratelimited("CCMP: decrypt failed: STA=%pM
  ",
  				    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 lib80211_ccmp_set_key(void *key, int len, u8 * seq, void *priv)

  {

  	struct lib80211_ccmp_data *data = priv;

  	int keyidx;

  	struct crypto_cipher *tfm = data->tfm;

  
  	keyidx = data->key_idx;
  	memset(data, 0, sizeof(*data));
  	data->key_idx = keyidx;
  	data->tfm = tfm;
  	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];
  		}
  		crypto_cipher_setkey(data->tfm, data->key, CCMP_TK_LEN);
  	} else if (len == 0)
  		data->key_set = 0;
  	else
  		return -1;
  
  	return 0;
  }

  static int lib80211_ccmp_get_key(void *key, int len, u8 * seq, void *priv)

  {

  	struct lib80211_ccmp_data *data = priv;

  
  	if (len < CCMP_TK_LEN)
  		return -1;
  
  	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 void lib80211_ccmp_print_stats(struct seq_file *m, void *priv)

  {

  	struct lib80211_ccmp_data *ccmp = priv;

  	seq_printf(m,
  		   "key[%d] alg=CCMP key_set=%d "
  		   "tx_pn=%02x%02x%02x%02x%02x%02x "
  		   "rx_pn=%02x%02x%02x%02x%02x%02x "
  		   "format_errors=%d replays=%d decrypt_errors=%d
  ",
  		   ccmp->key_idx, ccmp->key_set,
  		   ccmp->tx_pn[0], ccmp->tx_pn[1], ccmp->tx_pn[2],
  		   ccmp->tx_pn[3], ccmp->tx_pn[4], ccmp->tx_pn[5],
  		   ccmp->rx_pn[0], ccmp->rx_pn[1], ccmp->rx_pn[2],
  		   ccmp->rx_pn[3], ccmp->rx_pn[4], ccmp->rx_pn[5],
  		   ccmp->dot11RSNAStatsCCMPFormatErrors,
  		   ccmp->dot11RSNAStatsCCMPReplays,
  		   ccmp->dot11RSNAStatsCCMPDecryptErrors);

  }

  static struct lib80211_crypto_ops lib80211_crypt_ccmp = {

  	.name = "CCMP",

  	.init = lib80211_ccmp_init,
  	.deinit = lib80211_ccmp_deinit,

  	.encrypt_mpdu = lib80211_ccmp_encrypt,
  	.decrypt_mpdu = lib80211_ccmp_decrypt,

  	.encrypt_msdu = NULL,
  	.decrypt_msdu = NULL,

  	.set_key = lib80211_ccmp_set_key,
  	.get_key = lib80211_ccmp_get_key,
  	.print_stats = lib80211_ccmp_print_stats,

  	.extra_mpdu_prefix_len = CCMP_HDR_LEN,
  	.extra_mpdu_postfix_len = CCMP_MIC_LEN,

  	.owner = THIS_MODULE,

  };

  static int __init lib80211_crypto_ccmp_init(void)

  {

  	return lib80211_register_crypto_ops(&lib80211_crypt_ccmp);

  }

  static void __exit lib80211_crypto_ccmp_exit(void)

  {

  	lib80211_unregister_crypto_ops(&lib80211_crypt_ccmp);

  }

  module_init(lib80211_crypto_ccmp_init);
  module_exit(lib80211_crypto_ccmp_exit);