335 lines
8.4 KiB
C
335 lines
8.4 KiB
C
/*
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* FILS AEAD for (Re)Association Request/Response frames
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* Copyright 2016, Qualcomm Atheros, Inc.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <crypto/aes.h>
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#include <crypto/algapi.h>
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#include <crypto/hash.h>
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#include <crypto/skcipher.h>
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#include "ieee80211_i.h"
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#include "aes_cmac.h"
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#include "fils_aead.h"
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static void gf_mulx(u8 *pad)
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{
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u64 a = get_unaligned_be64(pad);
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u64 b = get_unaligned_be64(pad + 8);
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put_unaligned_be64((a << 1) | (b >> 63), pad);
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put_unaligned_be64((b << 1) ^ ((a >> 63) ? 0x87 : 0), pad + 8);
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}
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static int aes_s2v(struct crypto_shash *tfm,
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size_t num_elem, const u8 *addr[], size_t len[], u8 *v)
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{
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u8 d[AES_BLOCK_SIZE], tmp[AES_BLOCK_SIZE] = {};
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SHASH_DESC_ON_STACK(desc, tfm);
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size_t i;
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desc->tfm = tfm;
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/* D = AES-CMAC(K, <zero>) */
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crypto_shash_digest(desc, tmp, AES_BLOCK_SIZE, d);
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for (i = 0; i < num_elem - 1; i++) {
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/* D = dbl(D) xor AES_CMAC(K, Si) */
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gf_mulx(d); /* dbl */
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crypto_shash_digest(desc, addr[i], len[i], tmp);
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crypto_xor(d, tmp, AES_BLOCK_SIZE);
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}
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crypto_shash_init(desc);
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if (len[i] >= AES_BLOCK_SIZE) {
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/* len(Sn) >= 128 */
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/* T = Sn xorend D */
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crypto_shash_update(desc, addr[i], len[i] - AES_BLOCK_SIZE);
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crypto_xor(d, addr[i] + len[i] - AES_BLOCK_SIZE,
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AES_BLOCK_SIZE);
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} else {
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/* len(Sn) < 128 */
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/* T = dbl(D) xor pad(Sn) */
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gf_mulx(d); /* dbl */
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crypto_xor(d, addr[i], len[i]);
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d[len[i]] ^= 0x80;
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}
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/* V = AES-CMAC(K, T) */
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crypto_shash_finup(desc, d, AES_BLOCK_SIZE, v);
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return 0;
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}
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/* Note: addr[] and len[] needs to have one extra slot at the end. */
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static int aes_siv_encrypt(const u8 *key, size_t key_len,
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const u8 *plain, size_t plain_len,
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size_t num_elem, const u8 *addr[],
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size_t len[], u8 *out)
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{
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u8 v[AES_BLOCK_SIZE];
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struct crypto_shash *tfm;
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struct crypto_skcipher *tfm2;
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struct skcipher_request *req;
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int res;
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struct scatterlist src[1], dst[1];
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u8 *tmp;
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key_len /= 2; /* S2V key || CTR key */
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addr[num_elem] = plain;
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len[num_elem] = plain_len;
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num_elem++;
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/* S2V */
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tfm = crypto_alloc_shash("cmac(aes)", 0, 0);
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if (IS_ERR(tfm))
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return PTR_ERR(tfm);
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/* K1 for S2V */
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res = crypto_shash_setkey(tfm, key, key_len);
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if (!res)
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res = aes_s2v(tfm, num_elem, addr, len, v);
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crypto_free_shash(tfm);
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if (res)
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return res;
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/* Use a temporary buffer of the plaintext to handle need for
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* overwriting this during AES-CTR.
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*/
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tmp = kmemdup(plain, plain_len, GFP_KERNEL);
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if (!tmp)
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return -ENOMEM;
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/* IV for CTR before encrypted data */
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memcpy(out, v, AES_BLOCK_SIZE);
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/* Synthetic IV to be used as the initial counter in CTR:
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* Q = V bitand (1^64 || 0^1 || 1^31 || 0^1 || 1^31)
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*/
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v[8] &= 0x7f;
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v[12] &= 0x7f;
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/* CTR */
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tfm2 = crypto_alloc_skcipher("ctr(aes)", 0, CRYPTO_ALG_ASYNC);
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if (IS_ERR(tfm2)) {
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kfree(tmp);
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return PTR_ERR(tfm2);
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}
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/* K2 for CTR */
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res = crypto_skcipher_setkey(tfm2, key + key_len, key_len);
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if (res)
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goto fail;
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req = skcipher_request_alloc(tfm2, GFP_KERNEL);
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if (!req) {
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res = -ENOMEM;
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goto fail;
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}
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sg_init_one(src, tmp, plain_len);
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sg_init_one(dst, out + AES_BLOCK_SIZE, plain_len);
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skcipher_request_set_crypt(req, src, dst, plain_len, v);
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res = crypto_skcipher_encrypt(req);
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skcipher_request_free(req);
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fail:
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kfree(tmp);
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crypto_free_skcipher(tfm2);
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return res;
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}
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/* Note: addr[] and len[] needs to have one extra slot at the end. */
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static int aes_siv_decrypt(const u8 *key, size_t key_len,
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const u8 *iv_crypt, size_t iv_c_len,
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size_t num_elem, const u8 *addr[], size_t len[],
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u8 *out)
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{
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struct crypto_shash *tfm;
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struct crypto_skcipher *tfm2;
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struct skcipher_request *req;
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struct scatterlist src[1], dst[1];
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size_t crypt_len;
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int res;
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u8 frame_iv[AES_BLOCK_SIZE], iv[AES_BLOCK_SIZE];
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u8 check[AES_BLOCK_SIZE];
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crypt_len = iv_c_len - AES_BLOCK_SIZE;
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key_len /= 2; /* S2V key || CTR key */
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addr[num_elem] = out;
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len[num_elem] = crypt_len;
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num_elem++;
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memcpy(iv, iv_crypt, AES_BLOCK_SIZE);
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memcpy(frame_iv, iv_crypt, AES_BLOCK_SIZE);
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/* Synthetic IV to be used as the initial counter in CTR:
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* Q = V bitand (1^64 || 0^1 || 1^31 || 0^1 || 1^31)
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*/
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iv[8] &= 0x7f;
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iv[12] &= 0x7f;
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/* CTR */
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tfm2 = crypto_alloc_skcipher("ctr(aes)", 0, CRYPTO_ALG_ASYNC);
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if (IS_ERR(tfm2))
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return PTR_ERR(tfm2);
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/* K2 for CTR */
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res = crypto_skcipher_setkey(tfm2, key + key_len, key_len);
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if (res) {
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crypto_free_skcipher(tfm2);
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return res;
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}
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req = skcipher_request_alloc(tfm2, GFP_KERNEL);
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if (!req) {
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crypto_free_skcipher(tfm2);
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return -ENOMEM;
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}
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sg_init_one(src, iv_crypt + AES_BLOCK_SIZE, crypt_len);
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sg_init_one(dst, out, crypt_len);
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skcipher_request_set_crypt(req, src, dst, crypt_len, iv);
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res = crypto_skcipher_decrypt(req);
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skcipher_request_free(req);
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crypto_free_skcipher(tfm2);
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if (res)
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return res;
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/* S2V */
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tfm = crypto_alloc_shash("cmac(aes)", 0, 0);
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if (IS_ERR(tfm))
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return PTR_ERR(tfm);
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/* K1 for S2V */
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res = crypto_shash_setkey(tfm, key, key_len);
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if (!res)
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res = aes_s2v(tfm, num_elem, addr, len, check);
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crypto_free_shash(tfm);
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if (res)
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return res;
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if (memcmp(check, frame_iv, AES_BLOCK_SIZE) != 0)
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return -EINVAL;
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return 0;
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}
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int fils_encrypt_assoc_req(struct sk_buff *skb,
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struct ieee80211_mgd_assoc_data *assoc_data)
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{
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struct ieee80211_mgmt *mgmt = (void *)skb->data;
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u8 *capab, *ies, *encr;
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const u8 *addr[5 + 1], *session;
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size_t len[5 + 1];
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size_t crypt_len;
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if (ieee80211_is_reassoc_req(mgmt->frame_control)) {
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capab = (u8 *)&mgmt->u.reassoc_req.capab_info;
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ies = mgmt->u.reassoc_req.variable;
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} else {
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capab = (u8 *)&mgmt->u.assoc_req.capab_info;
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ies = mgmt->u.assoc_req.variable;
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}
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session = cfg80211_find_ext_ie(WLAN_EID_EXT_FILS_SESSION,
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ies, skb->data + skb->len - ies);
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if (!session || session[1] != 1 + 8)
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return -EINVAL;
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/* encrypt after FILS Session element */
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encr = (u8 *)session + 2 + 1 + 8;
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/* AES-SIV AAD vectors */
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/* The STA's MAC address */
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addr[0] = mgmt->sa;
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len[0] = ETH_ALEN;
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/* The AP's BSSID */
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addr[1] = mgmt->da;
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len[1] = ETH_ALEN;
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/* The STA's nonce */
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addr[2] = assoc_data->fils_nonces;
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len[2] = FILS_NONCE_LEN;
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/* The AP's nonce */
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addr[3] = &assoc_data->fils_nonces[FILS_NONCE_LEN];
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len[3] = FILS_NONCE_LEN;
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/* The (Re)Association Request frame from the Capability Information
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* field to the FILS Session element (both inclusive).
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*/
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addr[4] = capab;
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len[4] = encr - capab;
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crypt_len = skb->data + skb->len - encr;
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skb_put(skb, AES_BLOCK_SIZE);
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return aes_siv_encrypt(assoc_data->fils_kek, assoc_data->fils_kek_len,
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encr, crypt_len, 5, addr, len, encr);
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}
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int fils_decrypt_assoc_resp(struct ieee80211_sub_if_data *sdata,
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u8 *frame, size_t *frame_len,
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struct ieee80211_mgd_assoc_data *assoc_data)
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{
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struct ieee80211_mgmt *mgmt = (void *)frame;
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u8 *capab, *ies, *encr;
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const u8 *addr[5 + 1], *session;
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size_t len[5 + 1];
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int res;
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size_t crypt_len;
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if (*frame_len < 24 + 6)
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return -EINVAL;
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capab = (u8 *)&mgmt->u.assoc_resp.capab_info;
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ies = mgmt->u.assoc_resp.variable;
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session = cfg80211_find_ext_ie(WLAN_EID_EXT_FILS_SESSION,
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ies, frame + *frame_len - ies);
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if (!session || session[1] != 1 + 8) {
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mlme_dbg(sdata,
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"No (valid) FILS Session element in (Re)Association Response frame from %pM",
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mgmt->sa);
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return -EINVAL;
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}
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/* decrypt after FILS Session element */
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encr = (u8 *)session + 2 + 1 + 8;
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/* AES-SIV AAD vectors */
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/* The AP's BSSID */
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addr[0] = mgmt->sa;
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len[0] = ETH_ALEN;
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/* The STA's MAC address */
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addr[1] = mgmt->da;
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len[1] = ETH_ALEN;
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/* The AP's nonce */
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addr[2] = &assoc_data->fils_nonces[FILS_NONCE_LEN];
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len[2] = FILS_NONCE_LEN;
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/* The STA's nonce */
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addr[3] = assoc_data->fils_nonces;
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len[3] = FILS_NONCE_LEN;
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/* The (Re)Association Response frame from the Capability Information
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* field to the FILS Session element (both inclusive).
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*/
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addr[4] = capab;
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len[4] = encr - capab;
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crypt_len = frame + *frame_len - encr;
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if (crypt_len < AES_BLOCK_SIZE) {
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mlme_dbg(sdata,
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"Not enough room for AES-SIV data after FILS Session element in (Re)Association Response frame from %pM",
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mgmt->sa);
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return -EINVAL;
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}
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res = aes_siv_decrypt(assoc_data->fils_kek, assoc_data->fils_kek_len,
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encr, crypt_len, 5, addr, len, encr);
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if (res != 0) {
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mlme_dbg(sdata,
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"AES-SIV decryption of (Re)Association Response frame from %pM failed",
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mgmt->sa);
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return res;
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}
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*frame_len -= AES_BLOCK_SIZE;
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return 0;
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}
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