mirror of https://gitee.com/openkylin/linux.git
612 lines
17 KiB
C
612 lines
17 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* key management facility for FS encryption support.
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*
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* Copyright (C) 2015, Google, Inc.
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*
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* This contains encryption key functions.
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*
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* Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
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*/
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#include <keys/user-type.h>
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#include <linux/hashtable.h>
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#include <linux/scatterlist.h>
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#include <crypto/aes.h>
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#include <crypto/algapi.h>
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#include <crypto/sha.h>
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#include <crypto/skcipher.h>
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#include "fscrypt_private.h"
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static struct crypto_shash *essiv_hash_tfm;
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/* Table of keys referenced by FS_POLICY_FLAG_DIRECT_KEY policies */
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static DEFINE_HASHTABLE(fscrypt_master_keys, 6); /* 6 bits = 64 buckets */
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static DEFINE_SPINLOCK(fscrypt_master_keys_lock);
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/*
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* Key derivation function. This generates the derived key by encrypting the
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* master key with AES-128-ECB using the inode's nonce as the AES key.
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*
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* The master key must be at least as long as the derived key. If the master
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* key is longer, then only the first 'derived_keysize' bytes are used.
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*/
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static int derive_key_aes(const u8 *master_key,
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const struct fscrypt_context *ctx,
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u8 *derived_key, unsigned int derived_keysize)
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{
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int res = 0;
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struct skcipher_request *req = NULL;
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DECLARE_CRYPTO_WAIT(wait);
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struct scatterlist src_sg, dst_sg;
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struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0);
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if (IS_ERR(tfm)) {
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res = PTR_ERR(tfm);
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tfm = NULL;
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goto out;
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}
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crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
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req = skcipher_request_alloc(tfm, GFP_NOFS);
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if (!req) {
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res = -ENOMEM;
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goto out;
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}
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skcipher_request_set_callback(req,
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CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
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crypto_req_done, &wait);
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res = crypto_skcipher_setkey(tfm, ctx->nonce, sizeof(ctx->nonce));
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if (res < 0)
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goto out;
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sg_init_one(&src_sg, master_key, derived_keysize);
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sg_init_one(&dst_sg, derived_key, derived_keysize);
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skcipher_request_set_crypt(req, &src_sg, &dst_sg, derived_keysize,
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NULL);
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res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
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out:
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skcipher_request_free(req);
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crypto_free_skcipher(tfm);
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return res;
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}
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/*
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* Search the current task's subscribed keyrings for a "logon" key with
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* description prefix:descriptor, and if found acquire a read lock on it and
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* return a pointer to its validated payload in *payload_ret.
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*/
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static struct key *
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find_and_lock_process_key(const char *prefix,
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const u8 descriptor[FS_KEY_DESCRIPTOR_SIZE],
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unsigned int min_keysize,
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const struct fscrypt_key **payload_ret)
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{
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char *description;
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struct key *key;
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const struct user_key_payload *ukp;
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const struct fscrypt_key *payload;
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description = kasprintf(GFP_NOFS, "%s%*phN", prefix,
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FS_KEY_DESCRIPTOR_SIZE, descriptor);
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if (!description)
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return ERR_PTR(-ENOMEM);
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key = request_key(&key_type_logon, description, NULL);
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kfree(description);
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if (IS_ERR(key))
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return key;
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down_read(&key->sem);
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ukp = user_key_payload_locked(key);
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if (!ukp) /* was the key revoked before we acquired its semaphore? */
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goto invalid;
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payload = (const struct fscrypt_key *)ukp->data;
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if (ukp->datalen != sizeof(struct fscrypt_key) ||
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payload->size < 1 || payload->size > FS_MAX_KEY_SIZE) {
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fscrypt_warn(NULL,
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"key with description '%s' has invalid payload",
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key->description);
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goto invalid;
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}
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if (payload->size < min_keysize) {
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fscrypt_warn(NULL,
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"key with description '%s' is too short (got %u bytes, need %u+ bytes)",
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key->description, payload->size, min_keysize);
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goto invalid;
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}
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*payload_ret = payload;
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return key;
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invalid:
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up_read(&key->sem);
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key_put(key);
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return ERR_PTR(-ENOKEY);
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}
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static struct fscrypt_mode available_modes[] = {
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[FS_ENCRYPTION_MODE_AES_256_XTS] = {
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.friendly_name = "AES-256-XTS",
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.cipher_str = "xts(aes)",
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.keysize = 64,
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.ivsize = 16,
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},
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[FS_ENCRYPTION_MODE_AES_256_CTS] = {
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.friendly_name = "AES-256-CTS-CBC",
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.cipher_str = "cts(cbc(aes))",
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.keysize = 32,
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.ivsize = 16,
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},
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[FS_ENCRYPTION_MODE_AES_128_CBC] = {
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.friendly_name = "AES-128-CBC",
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.cipher_str = "cbc(aes)",
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.keysize = 16,
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.ivsize = 16,
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.needs_essiv = true,
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},
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[FS_ENCRYPTION_MODE_AES_128_CTS] = {
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.friendly_name = "AES-128-CTS-CBC",
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.cipher_str = "cts(cbc(aes))",
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.keysize = 16,
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.ivsize = 16,
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},
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[FS_ENCRYPTION_MODE_ADIANTUM] = {
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.friendly_name = "Adiantum",
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.cipher_str = "adiantum(xchacha12,aes)",
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.keysize = 32,
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.ivsize = 32,
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},
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};
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static struct fscrypt_mode *
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select_encryption_mode(const struct fscrypt_info *ci, const struct inode *inode)
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{
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if (!fscrypt_valid_enc_modes(ci->ci_data_mode, ci->ci_filename_mode)) {
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fscrypt_warn(inode->i_sb,
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"inode %lu uses unsupported encryption modes (contents mode %d, filenames mode %d)",
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inode->i_ino, ci->ci_data_mode,
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ci->ci_filename_mode);
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return ERR_PTR(-EINVAL);
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}
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if (S_ISREG(inode->i_mode))
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return &available_modes[ci->ci_data_mode];
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if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
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return &available_modes[ci->ci_filename_mode];
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WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n",
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inode->i_ino, (inode->i_mode & S_IFMT));
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return ERR_PTR(-EINVAL);
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}
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/* Find the master key, then derive the inode's actual encryption key */
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static int find_and_derive_key(const struct inode *inode,
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const struct fscrypt_context *ctx,
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u8 *derived_key, const struct fscrypt_mode *mode)
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{
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struct key *key;
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const struct fscrypt_key *payload;
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int err;
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key = find_and_lock_process_key(FS_KEY_DESC_PREFIX,
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ctx->master_key_descriptor,
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mode->keysize, &payload);
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if (key == ERR_PTR(-ENOKEY) && inode->i_sb->s_cop->key_prefix) {
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key = find_and_lock_process_key(inode->i_sb->s_cop->key_prefix,
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ctx->master_key_descriptor,
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mode->keysize, &payload);
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}
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if (IS_ERR(key))
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return PTR_ERR(key);
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if (ctx->flags & FS_POLICY_FLAG_DIRECT_KEY) {
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if (mode->ivsize < offsetofend(union fscrypt_iv, nonce)) {
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fscrypt_warn(inode->i_sb,
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"direct key mode not allowed with %s",
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mode->friendly_name);
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err = -EINVAL;
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} else if (ctx->contents_encryption_mode !=
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ctx->filenames_encryption_mode) {
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fscrypt_warn(inode->i_sb,
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"direct key mode not allowed with different contents and filenames modes");
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err = -EINVAL;
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} else {
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memcpy(derived_key, payload->raw, mode->keysize);
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err = 0;
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}
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} else {
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err = derive_key_aes(payload->raw, ctx, derived_key,
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mode->keysize);
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}
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up_read(&key->sem);
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key_put(key);
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return err;
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}
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/* Allocate and key a symmetric cipher object for the given encryption mode */
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static struct crypto_skcipher *
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allocate_skcipher_for_mode(struct fscrypt_mode *mode, const u8 *raw_key,
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const struct inode *inode)
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{
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struct crypto_skcipher *tfm;
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int err;
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tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0);
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if (IS_ERR(tfm)) {
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fscrypt_warn(inode->i_sb,
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"error allocating '%s' transform for inode %lu: %ld",
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mode->cipher_str, inode->i_ino, PTR_ERR(tfm));
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return tfm;
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}
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if (unlikely(!mode->logged_impl_name)) {
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/*
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* fscrypt performance can vary greatly depending on which
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* crypto algorithm implementation is used. Help people debug
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* performance problems by logging the ->cra_driver_name the
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* first time a mode is used. Note that multiple threads can
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* race here, but it doesn't really matter.
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*/
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mode->logged_impl_name = true;
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pr_info("fscrypt: %s using implementation \"%s\"\n",
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mode->friendly_name,
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crypto_skcipher_alg(tfm)->base.cra_driver_name);
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}
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crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
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err = crypto_skcipher_setkey(tfm, raw_key, mode->keysize);
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if (err)
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goto err_free_tfm;
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return tfm;
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err_free_tfm:
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crypto_free_skcipher(tfm);
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return ERR_PTR(err);
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}
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/* Master key referenced by FS_POLICY_FLAG_DIRECT_KEY policy */
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struct fscrypt_master_key {
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struct hlist_node mk_node;
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refcount_t mk_refcount;
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const struct fscrypt_mode *mk_mode;
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struct crypto_skcipher *mk_ctfm;
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u8 mk_descriptor[FS_KEY_DESCRIPTOR_SIZE];
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u8 mk_raw[FS_MAX_KEY_SIZE];
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};
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static void free_master_key(struct fscrypt_master_key *mk)
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{
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if (mk) {
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crypto_free_skcipher(mk->mk_ctfm);
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kzfree(mk);
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}
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}
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static void put_master_key(struct fscrypt_master_key *mk)
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{
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if (!refcount_dec_and_lock(&mk->mk_refcount, &fscrypt_master_keys_lock))
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return;
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hash_del(&mk->mk_node);
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spin_unlock(&fscrypt_master_keys_lock);
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free_master_key(mk);
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}
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/*
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* Find/insert the given master key into the fscrypt_master_keys table. If
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* found, it is returned with elevated refcount, and 'to_insert' is freed if
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* non-NULL. If not found, 'to_insert' is inserted and returned if it's
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* non-NULL; otherwise NULL is returned.
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*/
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static struct fscrypt_master_key *
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find_or_insert_master_key(struct fscrypt_master_key *to_insert,
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const u8 *raw_key, const struct fscrypt_mode *mode,
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const struct fscrypt_info *ci)
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{
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unsigned long hash_key;
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struct fscrypt_master_key *mk;
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/*
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* Careful: to avoid potentially leaking secret key bytes via timing
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* information, we must key the hash table by descriptor rather than by
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* raw key, and use crypto_memneq() when comparing raw keys.
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*/
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BUILD_BUG_ON(sizeof(hash_key) > FS_KEY_DESCRIPTOR_SIZE);
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memcpy(&hash_key, ci->ci_master_key_descriptor, sizeof(hash_key));
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spin_lock(&fscrypt_master_keys_lock);
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hash_for_each_possible(fscrypt_master_keys, mk, mk_node, hash_key) {
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if (memcmp(ci->ci_master_key_descriptor, mk->mk_descriptor,
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FS_KEY_DESCRIPTOR_SIZE) != 0)
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continue;
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if (mode != mk->mk_mode)
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continue;
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if (crypto_memneq(raw_key, mk->mk_raw, mode->keysize))
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continue;
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/* using existing tfm with same (descriptor, mode, raw_key) */
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refcount_inc(&mk->mk_refcount);
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spin_unlock(&fscrypt_master_keys_lock);
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free_master_key(to_insert);
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return mk;
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}
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if (to_insert)
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hash_add(fscrypt_master_keys, &to_insert->mk_node, hash_key);
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spin_unlock(&fscrypt_master_keys_lock);
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return to_insert;
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}
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/* Prepare to encrypt directly using the master key in the given mode */
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static struct fscrypt_master_key *
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fscrypt_get_master_key(const struct fscrypt_info *ci, struct fscrypt_mode *mode,
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const u8 *raw_key, const struct inode *inode)
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{
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struct fscrypt_master_key *mk;
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int err;
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/* Is there already a tfm for this key? */
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mk = find_or_insert_master_key(NULL, raw_key, mode, ci);
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if (mk)
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return mk;
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/* Nope, allocate one. */
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mk = kzalloc(sizeof(*mk), GFP_NOFS);
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if (!mk)
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return ERR_PTR(-ENOMEM);
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refcount_set(&mk->mk_refcount, 1);
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mk->mk_mode = mode;
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mk->mk_ctfm = allocate_skcipher_for_mode(mode, raw_key, inode);
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if (IS_ERR(mk->mk_ctfm)) {
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err = PTR_ERR(mk->mk_ctfm);
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mk->mk_ctfm = NULL;
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goto err_free_mk;
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}
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memcpy(mk->mk_descriptor, ci->ci_master_key_descriptor,
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FS_KEY_DESCRIPTOR_SIZE);
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memcpy(mk->mk_raw, raw_key, mode->keysize);
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return find_or_insert_master_key(mk, raw_key, mode, ci);
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err_free_mk:
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free_master_key(mk);
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return ERR_PTR(err);
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}
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static int derive_essiv_salt(const u8 *key, int keysize, u8 *salt)
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{
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struct crypto_shash *tfm = READ_ONCE(essiv_hash_tfm);
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/* init hash transform on demand */
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if (unlikely(!tfm)) {
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struct crypto_shash *prev_tfm;
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tfm = crypto_alloc_shash("sha256", 0, 0);
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if (IS_ERR(tfm)) {
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fscrypt_warn(NULL,
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"error allocating SHA-256 transform: %ld",
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PTR_ERR(tfm));
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return PTR_ERR(tfm);
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}
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prev_tfm = cmpxchg(&essiv_hash_tfm, NULL, tfm);
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if (prev_tfm) {
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crypto_free_shash(tfm);
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tfm = prev_tfm;
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}
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}
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{
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SHASH_DESC_ON_STACK(desc, tfm);
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desc->tfm = tfm;
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return crypto_shash_digest(desc, key, keysize, salt);
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}
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}
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static int init_essiv_generator(struct fscrypt_info *ci, const u8 *raw_key,
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int keysize)
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{
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int err;
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struct crypto_cipher *essiv_tfm;
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u8 salt[SHA256_DIGEST_SIZE];
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essiv_tfm = crypto_alloc_cipher("aes", 0, 0);
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if (IS_ERR(essiv_tfm))
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return PTR_ERR(essiv_tfm);
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ci->ci_essiv_tfm = essiv_tfm;
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err = derive_essiv_salt(raw_key, keysize, salt);
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if (err)
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goto out;
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/*
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* Using SHA256 to derive the salt/key will result in AES-256 being
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* used for IV generation. File contents encryption will still use the
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* configured keysize (AES-128) nevertheless.
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*/
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err = crypto_cipher_setkey(essiv_tfm, salt, sizeof(salt));
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if (err)
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goto out;
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out:
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memzero_explicit(salt, sizeof(salt));
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return err;
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}
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void __exit fscrypt_essiv_cleanup(void)
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{
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crypto_free_shash(essiv_hash_tfm);
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}
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/*
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* Given the encryption mode and key (normally the derived key, but for
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* FS_POLICY_FLAG_DIRECT_KEY mode it's the master key), set up the inode's
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* symmetric cipher transform object(s).
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*/
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static int setup_crypto_transform(struct fscrypt_info *ci,
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struct fscrypt_mode *mode,
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const u8 *raw_key, const struct inode *inode)
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{
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struct fscrypt_master_key *mk;
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struct crypto_skcipher *ctfm;
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int err;
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if (ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY) {
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mk = fscrypt_get_master_key(ci, mode, raw_key, inode);
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if (IS_ERR(mk))
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return PTR_ERR(mk);
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ctfm = mk->mk_ctfm;
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} else {
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mk = NULL;
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ctfm = allocate_skcipher_for_mode(mode, raw_key, inode);
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if (IS_ERR(ctfm))
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return PTR_ERR(ctfm);
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}
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ci->ci_master_key = mk;
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ci->ci_ctfm = ctfm;
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if (mode->needs_essiv) {
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/* ESSIV implies 16-byte IVs which implies !DIRECT_KEY */
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WARN_ON(mode->ivsize != AES_BLOCK_SIZE);
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WARN_ON(ci->ci_flags & FS_POLICY_FLAG_DIRECT_KEY);
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err = init_essiv_generator(ci, raw_key, mode->keysize);
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if (err) {
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fscrypt_warn(inode->i_sb,
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"error initializing ESSIV generator for inode %lu: %d",
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inode->i_ino, err);
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return err;
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}
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}
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return 0;
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}
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static void put_crypt_info(struct fscrypt_info *ci)
|
|
{
|
|
if (!ci)
|
|
return;
|
|
|
|
if (ci->ci_master_key) {
|
|
put_master_key(ci->ci_master_key);
|
|
} else {
|
|
crypto_free_skcipher(ci->ci_ctfm);
|
|
crypto_free_cipher(ci->ci_essiv_tfm);
|
|
}
|
|
kmem_cache_free(fscrypt_info_cachep, ci);
|
|
}
|
|
|
|
int fscrypt_get_encryption_info(struct inode *inode)
|
|
{
|
|
struct fscrypt_info *crypt_info;
|
|
struct fscrypt_context ctx;
|
|
struct fscrypt_mode *mode;
|
|
u8 *raw_key = NULL;
|
|
int res;
|
|
|
|
if (fscrypt_has_encryption_key(inode))
|
|
return 0;
|
|
|
|
res = fscrypt_initialize(inode->i_sb->s_cop->flags);
|
|
if (res)
|
|
return res;
|
|
|
|
res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
|
|
if (res < 0) {
|
|
if (!fscrypt_dummy_context_enabled(inode) ||
|
|
IS_ENCRYPTED(inode))
|
|
return res;
|
|
/* Fake up a context for an unencrypted directory */
|
|
memset(&ctx, 0, sizeof(ctx));
|
|
ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
|
|
ctx.contents_encryption_mode = FS_ENCRYPTION_MODE_AES_256_XTS;
|
|
ctx.filenames_encryption_mode = FS_ENCRYPTION_MODE_AES_256_CTS;
|
|
memset(ctx.master_key_descriptor, 0x42, FS_KEY_DESCRIPTOR_SIZE);
|
|
} else if (res != sizeof(ctx)) {
|
|
return -EINVAL;
|
|
}
|
|
|
|
if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1)
|
|
return -EINVAL;
|
|
|
|
if (ctx.flags & ~FS_POLICY_FLAGS_VALID)
|
|
return -EINVAL;
|
|
|
|
crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_NOFS);
|
|
if (!crypt_info)
|
|
return -ENOMEM;
|
|
|
|
crypt_info->ci_flags = ctx.flags;
|
|
crypt_info->ci_data_mode = ctx.contents_encryption_mode;
|
|
crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
|
|
memcpy(crypt_info->ci_master_key_descriptor, ctx.master_key_descriptor,
|
|
FS_KEY_DESCRIPTOR_SIZE);
|
|
memcpy(crypt_info->ci_nonce, ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
|
|
|
|
mode = select_encryption_mode(crypt_info, inode);
|
|
if (IS_ERR(mode)) {
|
|
res = PTR_ERR(mode);
|
|
goto out;
|
|
}
|
|
WARN_ON(mode->ivsize > FSCRYPT_MAX_IV_SIZE);
|
|
crypt_info->ci_mode = mode;
|
|
|
|
/*
|
|
* This cannot be a stack buffer because it may be passed to the
|
|
* scatterlist crypto API as part of key derivation.
|
|
*/
|
|
res = -ENOMEM;
|
|
raw_key = kmalloc(mode->keysize, GFP_NOFS);
|
|
if (!raw_key)
|
|
goto out;
|
|
|
|
res = find_and_derive_key(inode, &ctx, raw_key, mode);
|
|
if (res)
|
|
goto out;
|
|
|
|
res = setup_crypto_transform(crypt_info, mode, raw_key, inode);
|
|
if (res)
|
|
goto out;
|
|
|
|
if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL)
|
|
crypt_info = NULL;
|
|
out:
|
|
if (res == -ENOKEY)
|
|
res = 0;
|
|
put_crypt_info(crypt_info);
|
|
kzfree(raw_key);
|
|
return res;
|
|
}
|
|
EXPORT_SYMBOL(fscrypt_get_encryption_info);
|
|
|
|
/**
|
|
* fscrypt_put_encryption_info - free most of an inode's fscrypt data
|
|
*
|
|
* Free the inode's fscrypt_info. Filesystems must call this when the inode is
|
|
* being evicted. An RCU grace period need not have elapsed yet.
|
|
*/
|
|
void fscrypt_put_encryption_info(struct inode *inode)
|
|
{
|
|
put_crypt_info(inode->i_crypt_info);
|
|
inode->i_crypt_info = NULL;
|
|
}
|
|
EXPORT_SYMBOL(fscrypt_put_encryption_info);
|
|
|
|
/**
|
|
* fscrypt_free_inode - free an inode's fscrypt data requiring RCU delay
|
|
*
|
|
* Free the inode's cached decrypted symlink target, if any. Filesystems must
|
|
* call this after an RCU grace period, just before they free the inode.
|
|
*/
|
|
void fscrypt_free_inode(struct inode *inode)
|
|
{
|
|
if (IS_ENCRYPTED(inode) && S_ISLNK(inode->i_mode)) {
|
|
kfree(inode->i_link);
|
|
inode->i_link = NULL;
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(fscrypt_free_inode);
|