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/*

 * Host AP crypt: host-based CCMP encryption implementation for Host AP driver

 *

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

 *

 * 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 <net/ieee80211.h>

#include <linux/crypto.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_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 ieee80211_ccmp_aes_encrypt(struct crypto_cipher *tfm,

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

{

        crypto_cipher_encrypt_one(tfm, ct, pt);

}

static void *ieee80211_ccmp_init(int key_idx)

{

        struct ieee80211_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)) {

                printk(KERN_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_cipher(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_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_4addr *hdr,

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

{

        u8 *pos, qc = 0;

        size_t aad_len;

        u16 fc;

        int a4_included, qc_included;

        u8 aad[2 * AES_BLOCK_LEN];

        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) & IEEE80211_STYPE_QOS_DATA));

        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_ctl;

        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 */

        ieee80211_ccmp_aes_encrypt(tfm, b0, auth);

        xor_block(auth, aad, AES_BLOCK_LEN);

        ieee80211_ccmp_aes_encrypt(tfm, auth, auth);

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

        ieee80211_ccmp_aes_encrypt(tfm, auth, auth);

        b0[0] &= 0x07;

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

        ieee80211_ccmp_aes_encrypt(tfm, b0, s0);

}

static int ieee80211_ccmp_hdr(struct sk_buff *skb, int hdr_len,

                              u8 *aeskey, int keylen, void *priv)

{

        struct ieee80211_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 ieee80211_ccmp_encrypt(struct sk_buff *skb, int hdr_len, void *priv)

{

        struct ieee80211_ccmp_data *key = priv;

        int data_len, i, blocks, last, len;

        u8 *pos, *mic;

        struct ieee80211_hdr_4addr *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 = ieee80211_ccmp_hdr(skb, hdr_len, NULL, 0, priv);

        if (len < 0)

                return -1;

        pos = skb->data + hdr_len + CCMP_HDR_LEN;

        mic = skb_put(skb, CCMP_MIC_LEN);

        hdr = (struct ieee80211_hdr_4addr *)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);

                ieee80211_ccmp_aes_encrypt(key->tfm, b, b);

                /* Encryption, with counter */

                b0[14] = (i >> 8) & 0xff;

                b0[15] = i & 0xff;

                ieee80211_ccmp_aes_encrypt(key->tfm, b0, e);

                xor_block(pos, e, len);

                pos += 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 ieee80211_ccmp_decrypt(struct sk_buff *skb, int hdr_len, void *priv)

{

        struct ieee80211_ccmp_data *key = priv;

        u8 keyidx, *pos;

        struct ieee80211_hdr_4addr *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;

        DECLARE_MAC_BUF(mac);

        if (skb->len < hdr_len + CCMP_HDR_LEN + CCMP_MIC_LEN) {

                key->dot11RSNAStatsCCMPFormatErrors++;

                return -1;

        }

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

        pos = skb->data + hdr_len;

        keyidx = pos[3];

        if (!(keyidx & (1 << 5))) {

                if (net_ratelimit()) {

                        printk(KERN_DEBUG "CCMP: received packet without ExtIV"

                               " flag from %s\n", print_mac(mac, 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\n", key->key_idx, keyidx, priv);

                return -6;

        }

        if (!key->key_set) {

                if (net_ratelimit()) {

                        printk(KERN_DEBUG "CCMP: received packet from %s"

                               " with keyid=%d that does not have a configured"

                               " key\n", print_mac(mac, 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)) {

                if (ieee80211_ratelimit_debug(IEEE80211_DL_DROP)) {

                        IEEE80211_DEBUG_DROP("CCMP: replay detected: STA=%s "

                                 "previous PN %02x%02x%02x%02x%02x%02x "

                                 "received PN %02x%02x%02x%02x%02x%02x\n",

                                 print_mac(mac, 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]);

                }

                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;

                ieee80211_ccmp_aes_encrypt(key->tfm, b0, b);

                xor_block(pos, b, len);

                /* Authentication */

                xor_block(a, pos, len);

                ieee80211_ccmp_aes_encrypt(key->tfm, a, a);

                pos += len;

        }

        if (memcmp(mic, a, CCMP_MIC_LEN) != 0) {

                if (net_ratelimit()) {

                        printk(KERN_DEBUG "CCMP: decrypt failed: STA="

                               "%s\n", print_mac(mac, 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_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 ieee80211_ccmp_get_key(void *key, int len, u8 * seq, void *priv)

{

        struct ieee80211_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 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=%02x%02x%02x%02x%02x%02x "

                     "rx_pn=%02x%02x%02x%02x%02x%02x "

                     "format_errors=%d replays=%d decrypt_errors=%d\n",

                     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);

        return p;

}

static struct ieee80211_crypto_ops ieee80211_crypt_ccmp = {

        .name = "CCMP",

        .init = ieee80211_ccmp_init,

        .deinit = ieee80211_ccmp_deinit,

        .build_iv = ieee80211_ccmp_hdr,

        .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_mpdu_prefix_len = CCMP_HDR_LEN,

        .extra_mpdu_postfix_len = CCMP_MIC_LEN,

        .owner = THIS_MODULE,

};

static int __init ieee80211_crypto_ccmp_init(void)

{

        return ieee80211_register_crypto_ops(&ieee80211_crypt_ccmp);

}

static void __exit ieee80211_crypto_ccmp_exit(void)

{

        ieee80211_unregister_crypto_ops(&ieee80211_crypt_ccmp);

}

module_init(ieee80211_crypto_ccmp_init);

module_exit(ieee80211_crypto_ccmp_exit);