// SPDX-License-Identifier: GPL-2.0
/*
 * Host AP crypt: host-based WEP encryption implementation for Host AP driver
 *
 * Copyright (c) 2002-2004, Jouni Malinen <jkmaline@cc.hut.fi>
 */

#include <crypto/arc4.h>
#include <linux/fips.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/random.h>
#include <linux/skbuff.h>
#include <linux/string.h>
#include "rtllib.h"

#include <linux/crc32.h>

struct prism2_wep_data {
	u32 iv;
#define WEP_KEY_LEN 13
	u8 key[WEP_KEY_LEN + 1];
	u8 key_len;
	u8 key_idx;
	struct arc4_ctx rx_ctx_arc4;
	struct arc4_ctx tx_ctx_arc4;
};

static void *prism2_wep_init(int keyidx)
{
	struct prism2_wep_data *priv;

	if (fips_enabled)
		return NULL;

	priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
	if (priv == NULL)
		return NULL;
	priv->key_idx = keyidx;

	/* start WEP IV from a random value */
	get_random_bytes(&priv->iv, 4);

	return priv;
}

static void prism2_wep_deinit(void *priv)
{
	kfree_sensitive(priv);
}

/* Perform WEP encryption on given skb that has at least 4 bytes of headroom
 * for IV and 4 bytes of tailroom for ICV. 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))
 */
static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
{
	struct prism2_wep_data *wep = priv;
	u32 klen, len;
	u8 key[WEP_KEY_LEN + 3];
	u8 *pos;
	struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb +
				    MAX_DEV_ADDR_SIZE);
	u32 crc;
	u8 *icv;

	if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
	    skb->len < hdr_len){
		pr_err("Error!!! headroom=%d tailroom=%d skblen=%d hdr_len=%d\n",
		       skb_headroom(skb), skb_tailroom(skb), skb->len, hdr_len);
		return -1;
	}
	len = skb->len - hdr_len;
	pos = skb_push(skb, 4);
	memmove(pos, pos + 4, hdr_len);
	pos += hdr_len;

	klen = 3 + wep->key_len;

	wep->iv++;

	/* 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 ((wep->iv & 0xff00) == 0xff00) {
		u8 B = (wep->iv >> 16) & 0xff;

		if (B >= 3 && B < klen)
			wep->iv += 0x0100;
	}

	/* Prepend 24-bit IV to RC4 key and TX frame */
	*pos++ = key[0] = (wep->iv >> 16) & 0xff;
	*pos++ = key[1] = (wep->iv >> 8) & 0xff;
	*pos++ = key[2] = wep->iv & 0xff;
	*pos++ = wep->key_idx << 6;

	/* Copy rest of the WEP key (the secret part) */
	memcpy(key + 3, wep->key, wep->key_len);

	if (!tcb_desc->bHwSec) {
		/* Append little-endian CRC32 and encrypt it to produce ICV */
		crc = ~crc32_le(~0, pos, len);
		icv = skb_put(skb, 4);
		icv[0] = crc;
		icv[1] = crc >> 8;
		icv[2] = crc >> 16;
		icv[3] = crc >> 24;

		arc4_setkey(&wep->tx_ctx_arc4, key, klen);
		arc4_crypt(&wep->tx_ctx_arc4, pos, pos, len + 4);
	}

	return 0;
}

/* Perform WEP decryption on given struct buffer. Buffer includes whole WEP
 * part of the frame: IV (4 bytes), encrypted payload (including SNAP header),
 * ICV (4 bytes). 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.
 */
static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
{
	struct prism2_wep_data *wep = priv;
	u32  klen, plen;
	u8 key[WEP_KEY_LEN + 3];
	u8 keyidx, *pos;
	struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb +
				    MAX_DEV_ADDR_SIZE);
	u32 crc;
	u8 icv[4];

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

	pos = skb->data + hdr_len;
	key[0] = *pos++;
	key[1] = *pos++;
	key[2] = *pos++;
	keyidx = *pos++ >> 6;
	if (keyidx != wep->key_idx)
		return -1;

	klen = 3 + wep->key_len;

	/* Copy rest of the WEP key (the secret part) */
	memcpy(key + 3, wep->key, wep->key_len);

	/* Apply RC4 to data and compute CRC32 over decrypted data */
	plen = skb->len - hdr_len - 8;

	if (!tcb_desc->bHwSec) {
		arc4_setkey(&wep->rx_ctx_arc4, key, klen);
		arc4_crypt(&wep->rx_ctx_arc4, pos, pos, 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) {
			/* ICV mismatch - drop frame */
			return -2;
		}
	}
	/* Remove IV and ICV */
	memmove(skb->data + 4, skb->data, hdr_len);
	skb_pull(skb, 4);
	skb_trim(skb, skb->len - 4);

	return 0;
}

static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv)
{
	struct prism2_wep_data *wep = priv;

	if (len < 0 || len > WEP_KEY_LEN)
		return -1;

	memcpy(wep->key, key, len);
	wep->key_len = len;

	return 0;
}

static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv)
{
	struct prism2_wep_data *wep = priv;

	if (len < wep->key_len)
		return -1;

	memcpy(key, wep->key, wep->key_len);

	return wep->key_len;
}

static void prism2_wep_print_stats(struct seq_file *m, void *priv)
{
	struct prism2_wep_data *wep = priv;

	seq_printf(m, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len);
}

static struct lib80211_crypto_ops rtllib_crypt_wep = {
	.name			= "R-WEP",
	.init			= prism2_wep_init,
	.deinit			= prism2_wep_deinit,
	.encrypt_mpdu		= prism2_wep_encrypt,
	.decrypt_mpdu		= prism2_wep_decrypt,
	.encrypt_msdu		= NULL,
	.decrypt_msdu		= NULL,
	.set_key		= prism2_wep_set_key,
	.get_key		= prism2_wep_get_key,
	.print_stats		= prism2_wep_print_stats,
	.extra_mpdu_prefix_len  = 4,	/* IV */
	.extra_mpdu_postfix_len = 4,	/* ICV */
	.owner			= THIS_MODULE,
};

static int __init rtllib_crypto_wep_init(void)
{
	return lib80211_register_crypto_ops(&rtllib_crypt_wep);
}

static void __exit rtllib_crypto_wep_exit(void)
{
	lib80211_unregister_crypto_ops(&rtllib_crypt_wep);
}

module_init(rtllib_crypto_wep_init);
module_exit(rtllib_crypto_wep_exit);

MODULE_LICENSE("GPL");