forked from Minki/linux
5dae460c22
Add a new fscrypt policy version, "v2". It has the following changes from the original policy version, which we call "v1" (*): - Master keys (the user-provided encryption keys) are only ever used as input to HKDF-SHA512. This is more flexible and less error-prone, and it avoids the quirks and limitations of the AES-128-ECB based KDF. Three classes of cryptographically isolated subkeys are defined: - Per-file keys, like used in v1 policies except for the new KDF. - Per-mode keys. These implement the semantics of the DIRECT_KEY flag, which for v1 policies made the master key be used directly. These are also planned to be used for inline encryption when support for it is added. - Key identifiers (see below). - Each master key is identified by a 16-byte master_key_identifier, which is derived from the key itself using HKDF-SHA512. This prevents users from associating the wrong key with an encrypted file or directory. This was easily possible with v1 policies, which identified the key by an arbitrary 8-byte master_key_descriptor. - The key must be provided in the filesystem-level keyring, not in a process-subscribed keyring. The following UAPI additions are made: - The existing ioctl FS_IOC_SET_ENCRYPTION_POLICY can now be passed a fscrypt_policy_v2 to set a v2 encryption policy. It's disambiguated from fscrypt_policy/fscrypt_policy_v1 by the version code prefix. - A new ioctl FS_IOC_GET_ENCRYPTION_POLICY_EX is added. It allows getting the v1 or v2 encryption policy of an encrypted file or directory. The existing FS_IOC_GET_ENCRYPTION_POLICY ioctl could not be used because it did not have a way for userspace to indicate which policy structure is expected. The new ioctl includes a size field, so it is extensible to future fscrypt policy versions. - The ioctls FS_IOC_ADD_ENCRYPTION_KEY, FS_IOC_REMOVE_ENCRYPTION_KEY, and FS_IOC_GET_ENCRYPTION_KEY_STATUS now support managing keys for v2 encryption policies. Such keys are kept logically separate from keys for v1 encryption policies, and are identified by 'identifier' rather than by 'descriptor'. The 'identifier' need not be provided when adding a key, since the kernel will calculate it anyway. This patch temporarily keeps adding/removing v2 policy keys behind the same permission check done for adding/removing v1 policy keys: capable(CAP_SYS_ADMIN). However, the next patch will carefully take advantage of the cryptographically secure master_key_identifier to allow non-root users to add/remove v2 policy keys, thus providing a full replacement for v1 policies. (*) Actually, in the API fscrypt_policy::version is 0 while on-disk fscrypt_context::format is 1. But I believe it makes the most sense to advance both to '2' to have them be in sync, and to consider the numbering to start at 1 except for the API quirk. Reviewed-by: Paul Crowley <paulcrowley@google.com> Reviewed-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Eric Biggers <ebiggers@google.com>
521 lines
16 KiB
C
521 lines
16 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* This contains encryption functions for per-file encryption.
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*
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* Copyright (C) 2015, Google, Inc.
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* Copyright (C) 2015, Motorola Mobility
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*
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* Written by Michael Halcrow, 2014.
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*
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* Filename encryption additions
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* Uday Savagaonkar, 2014
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* Encryption policy handling additions
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* Ildar Muslukhov, 2014
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* Add fscrypt_pullback_bio_page()
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* Jaegeuk Kim, 2015.
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*
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* This has not yet undergone a rigorous security audit.
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*
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* The usage of AES-XTS should conform to recommendations in NIST
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* Special Publication 800-38E and IEEE P1619/D16.
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*/
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#include <linux/pagemap.h>
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#include <linux/mempool.h>
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#include <linux/module.h>
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#include <linux/scatterlist.h>
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#include <linux/ratelimit.h>
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#include <linux/dcache.h>
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#include <linux/namei.h>
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#include <crypto/aes.h>
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#include <crypto/skcipher.h>
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#include "fscrypt_private.h"
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static unsigned int num_prealloc_crypto_pages = 32;
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static unsigned int num_prealloc_crypto_ctxs = 128;
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module_param(num_prealloc_crypto_pages, uint, 0444);
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MODULE_PARM_DESC(num_prealloc_crypto_pages,
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"Number of crypto pages to preallocate");
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module_param(num_prealloc_crypto_ctxs, uint, 0444);
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MODULE_PARM_DESC(num_prealloc_crypto_ctxs,
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"Number of crypto contexts to preallocate");
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static mempool_t *fscrypt_bounce_page_pool = NULL;
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static LIST_HEAD(fscrypt_free_ctxs);
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static DEFINE_SPINLOCK(fscrypt_ctx_lock);
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static struct workqueue_struct *fscrypt_read_workqueue;
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static DEFINE_MUTEX(fscrypt_init_mutex);
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static struct kmem_cache *fscrypt_ctx_cachep;
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struct kmem_cache *fscrypt_info_cachep;
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void fscrypt_enqueue_decrypt_work(struct work_struct *work)
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{
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queue_work(fscrypt_read_workqueue, work);
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}
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EXPORT_SYMBOL(fscrypt_enqueue_decrypt_work);
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/**
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* fscrypt_release_ctx() - Release a decryption context
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* @ctx: The decryption context to release.
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*
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* If the decryption context was allocated from the pre-allocated pool, return
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* it to that pool. Else, free it.
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*/
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void fscrypt_release_ctx(struct fscrypt_ctx *ctx)
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{
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unsigned long flags;
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if (ctx->flags & FS_CTX_REQUIRES_FREE_ENCRYPT_FL) {
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kmem_cache_free(fscrypt_ctx_cachep, ctx);
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} else {
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spin_lock_irqsave(&fscrypt_ctx_lock, flags);
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list_add(&ctx->free_list, &fscrypt_free_ctxs);
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spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
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}
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}
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EXPORT_SYMBOL(fscrypt_release_ctx);
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/**
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* fscrypt_get_ctx() - Get a decryption context
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* @gfp_flags: The gfp flag for memory allocation
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*
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* Allocate and initialize a decryption context.
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*
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* Return: A new decryption context on success; an ERR_PTR() otherwise.
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*/
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struct fscrypt_ctx *fscrypt_get_ctx(gfp_t gfp_flags)
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{
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struct fscrypt_ctx *ctx;
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unsigned long flags;
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/*
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* First try getting a ctx from the free list so that we don't have to
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* call into the slab allocator.
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*/
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spin_lock_irqsave(&fscrypt_ctx_lock, flags);
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ctx = list_first_entry_or_null(&fscrypt_free_ctxs,
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struct fscrypt_ctx, free_list);
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if (ctx)
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list_del(&ctx->free_list);
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spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
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if (!ctx) {
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ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, gfp_flags);
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if (!ctx)
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return ERR_PTR(-ENOMEM);
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ctx->flags |= FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
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} else {
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ctx->flags &= ~FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
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}
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return ctx;
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}
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EXPORT_SYMBOL(fscrypt_get_ctx);
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struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags)
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{
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return mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
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}
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/**
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* fscrypt_free_bounce_page() - free a ciphertext bounce page
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*
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* Free a bounce page that was allocated by fscrypt_encrypt_pagecache_blocks(),
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* or by fscrypt_alloc_bounce_page() directly.
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*/
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void fscrypt_free_bounce_page(struct page *bounce_page)
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{
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if (!bounce_page)
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return;
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set_page_private(bounce_page, (unsigned long)NULL);
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ClearPagePrivate(bounce_page);
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mempool_free(bounce_page, fscrypt_bounce_page_pool);
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}
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EXPORT_SYMBOL(fscrypt_free_bounce_page);
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void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
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const struct fscrypt_info *ci)
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{
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memset(iv, 0, ci->ci_mode->ivsize);
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iv->lblk_num = cpu_to_le64(lblk_num);
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if (fscrypt_is_direct_key_policy(&ci->ci_policy))
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memcpy(iv->nonce, ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE);
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if (ci->ci_essiv_tfm != NULL)
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crypto_cipher_encrypt_one(ci->ci_essiv_tfm, iv->raw, iv->raw);
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}
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/* Encrypt or decrypt a single filesystem block of file contents */
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int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw,
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u64 lblk_num, struct page *src_page,
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struct page *dest_page, unsigned int len,
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unsigned int offs, gfp_t gfp_flags)
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{
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union fscrypt_iv iv;
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struct skcipher_request *req = NULL;
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DECLARE_CRYPTO_WAIT(wait);
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struct scatterlist dst, src;
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struct fscrypt_info *ci = inode->i_crypt_info;
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struct crypto_skcipher *tfm = ci->ci_ctfm;
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int res = 0;
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if (WARN_ON_ONCE(len <= 0))
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return -EINVAL;
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if (WARN_ON_ONCE(len % FS_CRYPTO_BLOCK_SIZE != 0))
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return -EINVAL;
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fscrypt_generate_iv(&iv, lblk_num, ci);
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req = skcipher_request_alloc(tfm, gfp_flags);
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if (!req)
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return -ENOMEM;
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skcipher_request_set_callback(
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req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
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crypto_req_done, &wait);
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sg_init_table(&dst, 1);
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sg_set_page(&dst, dest_page, len, offs);
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sg_init_table(&src, 1);
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sg_set_page(&src, src_page, len, offs);
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skcipher_request_set_crypt(req, &src, &dst, len, &iv);
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if (rw == FS_DECRYPT)
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res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
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else
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res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
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skcipher_request_free(req);
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if (res) {
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fscrypt_err(inode, "%scryption failed for block %llu: %d",
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(rw == FS_DECRYPT ? "De" : "En"), lblk_num, res);
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return res;
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}
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return 0;
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}
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/**
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* fscrypt_encrypt_pagecache_blocks() - Encrypt filesystem blocks from a pagecache page
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* @page: The locked pagecache page containing the block(s) to encrypt
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* @len: Total size of the block(s) to encrypt. Must be a nonzero
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* multiple of the filesystem's block size.
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* @offs: Byte offset within @page of the first block to encrypt. Must be
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* a multiple of the filesystem's block size.
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* @gfp_flags: Memory allocation flags
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*
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* A new bounce page is allocated, and the specified block(s) are encrypted into
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* it. In the bounce page, the ciphertext block(s) will be located at the same
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* offsets at which the plaintext block(s) were located in the source page; any
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* other parts of the bounce page will be left uninitialized. However, normally
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* blocksize == PAGE_SIZE and the whole page is encrypted at once.
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*
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* This is for use by the filesystem's ->writepages() method.
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*
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* Return: the new encrypted bounce page on success; an ERR_PTR() on failure
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*/
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struct page *fscrypt_encrypt_pagecache_blocks(struct page *page,
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unsigned int len,
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unsigned int offs,
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gfp_t gfp_flags)
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{
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const struct inode *inode = page->mapping->host;
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const unsigned int blockbits = inode->i_blkbits;
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const unsigned int blocksize = 1 << blockbits;
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struct page *ciphertext_page;
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u64 lblk_num = ((u64)page->index << (PAGE_SHIFT - blockbits)) +
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(offs >> blockbits);
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unsigned int i;
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int err;
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if (WARN_ON_ONCE(!PageLocked(page)))
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return ERR_PTR(-EINVAL);
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if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, blocksize)))
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return ERR_PTR(-EINVAL);
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ciphertext_page = fscrypt_alloc_bounce_page(gfp_flags);
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if (!ciphertext_page)
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return ERR_PTR(-ENOMEM);
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for (i = offs; i < offs + len; i += blocksize, lblk_num++) {
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err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num,
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page, ciphertext_page,
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blocksize, i, gfp_flags);
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if (err) {
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fscrypt_free_bounce_page(ciphertext_page);
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return ERR_PTR(err);
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}
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}
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SetPagePrivate(ciphertext_page);
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set_page_private(ciphertext_page, (unsigned long)page);
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return ciphertext_page;
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}
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EXPORT_SYMBOL(fscrypt_encrypt_pagecache_blocks);
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/**
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* fscrypt_encrypt_block_inplace() - Encrypt a filesystem block in-place
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* @inode: The inode to which this block belongs
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* @page: The page containing the block to encrypt
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* @len: Size of block to encrypt. Doesn't need to be a multiple of the
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* fs block size, but must be a multiple of FS_CRYPTO_BLOCK_SIZE.
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* @offs: Byte offset within @page at which the block to encrypt begins
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* @lblk_num: Filesystem logical block number of the block, i.e. the 0-based
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* number of the block within the file
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* @gfp_flags: Memory allocation flags
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*
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* Encrypt a possibly-compressed filesystem block that is located in an
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* arbitrary page, not necessarily in the original pagecache page. The @inode
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* and @lblk_num must be specified, as they can't be determined from @page.
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*
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* Return: 0 on success; -errno on failure
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*/
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int fscrypt_encrypt_block_inplace(const struct inode *inode, struct page *page,
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unsigned int len, unsigned int offs,
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u64 lblk_num, gfp_t gfp_flags)
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{
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return fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num, page, page,
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len, offs, gfp_flags);
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}
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EXPORT_SYMBOL(fscrypt_encrypt_block_inplace);
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/**
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* fscrypt_decrypt_pagecache_blocks() - Decrypt filesystem blocks in a pagecache page
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* @page: The locked pagecache page containing the block(s) to decrypt
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* @len: Total size of the block(s) to decrypt. Must be a nonzero
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* multiple of the filesystem's block size.
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* @offs: Byte offset within @page of the first block to decrypt. Must be
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* a multiple of the filesystem's block size.
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*
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* The specified block(s) are decrypted in-place within the pagecache page,
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* which must still be locked and not uptodate. Normally, blocksize ==
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* PAGE_SIZE and the whole page is decrypted at once.
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*
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* This is for use by the filesystem's ->readpages() method.
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*
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* Return: 0 on success; -errno on failure
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*/
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int fscrypt_decrypt_pagecache_blocks(struct page *page, unsigned int len,
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unsigned int offs)
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{
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const struct inode *inode = page->mapping->host;
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const unsigned int blockbits = inode->i_blkbits;
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const unsigned int blocksize = 1 << blockbits;
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u64 lblk_num = ((u64)page->index << (PAGE_SHIFT - blockbits)) +
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(offs >> blockbits);
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unsigned int i;
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int err;
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if (WARN_ON_ONCE(!PageLocked(page)))
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return -EINVAL;
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if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, blocksize)))
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return -EINVAL;
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for (i = offs; i < offs + len; i += blocksize, lblk_num++) {
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err = fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, page,
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page, blocksize, i, GFP_NOFS);
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if (err)
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return err;
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}
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return 0;
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}
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EXPORT_SYMBOL(fscrypt_decrypt_pagecache_blocks);
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/**
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* fscrypt_decrypt_block_inplace() - Decrypt a filesystem block in-place
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* @inode: The inode to which this block belongs
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* @page: The page containing the block to decrypt
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* @len: Size of block to decrypt. Doesn't need to be a multiple of the
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* fs block size, but must be a multiple of FS_CRYPTO_BLOCK_SIZE.
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* @offs: Byte offset within @page at which the block to decrypt begins
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* @lblk_num: Filesystem logical block number of the block, i.e. the 0-based
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* number of the block within the file
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*
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* Decrypt a possibly-compressed filesystem block that is located in an
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* arbitrary page, not necessarily in the original pagecache page. The @inode
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* and @lblk_num must be specified, as they can't be determined from @page.
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*
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* Return: 0 on success; -errno on failure
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*/
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int fscrypt_decrypt_block_inplace(const struct inode *inode, struct page *page,
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unsigned int len, unsigned int offs,
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u64 lblk_num)
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{
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return fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, page, page,
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len, offs, GFP_NOFS);
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}
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EXPORT_SYMBOL(fscrypt_decrypt_block_inplace);
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/*
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* Validate dentries in encrypted directories to make sure we aren't potentially
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* caching stale dentries after a key has been added.
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*/
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static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
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{
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struct dentry *dir;
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int err;
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int valid;
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/*
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* Plaintext names are always valid, since fscrypt doesn't support
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* reverting to ciphertext names without evicting the directory's inode
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* -- which implies eviction of the dentries in the directory.
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*/
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if (!(dentry->d_flags & DCACHE_ENCRYPTED_NAME))
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return 1;
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/*
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* Ciphertext name; valid if the directory's key is still unavailable.
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*
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* Although fscrypt forbids rename() on ciphertext names, we still must
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* use dget_parent() here rather than use ->d_parent directly. That's
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* because a corrupted fs image may contain directory hard links, which
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* the VFS handles by moving the directory's dentry tree in the dcache
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* each time ->lookup() finds the directory and it already has a dentry
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* elsewhere. Thus ->d_parent can be changing, and we must safely grab
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* a reference to some ->d_parent to prevent it from being freed.
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*/
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if (flags & LOOKUP_RCU)
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return -ECHILD;
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dir = dget_parent(dentry);
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err = fscrypt_get_encryption_info(d_inode(dir));
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valid = !fscrypt_has_encryption_key(d_inode(dir));
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dput(dir);
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if (err < 0)
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return err;
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return valid;
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}
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const struct dentry_operations fscrypt_d_ops = {
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.d_revalidate = fscrypt_d_revalidate,
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};
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static void fscrypt_destroy(void)
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{
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struct fscrypt_ctx *pos, *n;
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list_for_each_entry_safe(pos, n, &fscrypt_free_ctxs, free_list)
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kmem_cache_free(fscrypt_ctx_cachep, pos);
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INIT_LIST_HEAD(&fscrypt_free_ctxs);
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mempool_destroy(fscrypt_bounce_page_pool);
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fscrypt_bounce_page_pool = NULL;
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}
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/**
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* fscrypt_initialize() - allocate major buffers for fs encryption.
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* @cop_flags: fscrypt operations flags
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*
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* We only call this when we start accessing encrypted files, since it
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* results in memory getting allocated that wouldn't otherwise be used.
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*
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* Return: Zero on success, non-zero otherwise.
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*/
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int fscrypt_initialize(unsigned int cop_flags)
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{
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int i, res = -ENOMEM;
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/* No need to allocate a bounce page pool if this FS won't use it. */
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|
if (cop_flags & FS_CFLG_OWN_PAGES)
|
|
return 0;
|
|
|
|
mutex_lock(&fscrypt_init_mutex);
|
|
if (fscrypt_bounce_page_pool)
|
|
goto already_initialized;
|
|
|
|
for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
|
|
struct fscrypt_ctx *ctx;
|
|
|
|
ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, GFP_NOFS);
|
|
if (!ctx)
|
|
goto fail;
|
|
list_add(&ctx->free_list, &fscrypt_free_ctxs);
|
|
}
|
|
|
|
fscrypt_bounce_page_pool =
|
|
mempool_create_page_pool(num_prealloc_crypto_pages, 0);
|
|
if (!fscrypt_bounce_page_pool)
|
|
goto fail;
|
|
|
|
already_initialized:
|
|
mutex_unlock(&fscrypt_init_mutex);
|
|
return 0;
|
|
fail:
|
|
fscrypt_destroy();
|
|
mutex_unlock(&fscrypt_init_mutex);
|
|
return res;
|
|
}
|
|
|
|
void fscrypt_msg(const struct inode *inode, const char *level,
|
|
const char *fmt, ...)
|
|
{
|
|
static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
|
|
DEFAULT_RATELIMIT_BURST);
|
|
struct va_format vaf;
|
|
va_list args;
|
|
|
|
if (!__ratelimit(&rs))
|
|
return;
|
|
|
|
va_start(args, fmt);
|
|
vaf.fmt = fmt;
|
|
vaf.va = &args;
|
|
if (inode)
|
|
printk("%sfscrypt (%s, inode %lu): %pV\n",
|
|
level, inode->i_sb->s_id, inode->i_ino, &vaf);
|
|
else
|
|
printk("%sfscrypt: %pV\n", level, &vaf);
|
|
va_end(args);
|
|
}
|
|
|
|
/**
|
|
* fscrypt_init() - Set up for fs encryption.
|
|
*/
|
|
static int __init fscrypt_init(void)
|
|
{
|
|
int err = -ENOMEM;
|
|
|
|
/*
|
|
* Use an unbound workqueue to allow bios to be decrypted in parallel
|
|
* even when they happen to complete on the same CPU. This sacrifices
|
|
* locality, but it's worthwhile since decryption is CPU-intensive.
|
|
*
|
|
* Also use a high-priority workqueue to prioritize decryption work,
|
|
* which blocks reads from completing, over regular application tasks.
|
|
*/
|
|
fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
|
|
WQ_UNBOUND | WQ_HIGHPRI,
|
|
num_online_cpus());
|
|
if (!fscrypt_read_workqueue)
|
|
goto fail;
|
|
|
|
fscrypt_ctx_cachep = KMEM_CACHE(fscrypt_ctx, SLAB_RECLAIM_ACCOUNT);
|
|
if (!fscrypt_ctx_cachep)
|
|
goto fail_free_queue;
|
|
|
|
fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT);
|
|
if (!fscrypt_info_cachep)
|
|
goto fail_free_ctx;
|
|
|
|
err = fscrypt_init_keyring();
|
|
if (err)
|
|
goto fail_free_info;
|
|
|
|
return 0;
|
|
|
|
fail_free_info:
|
|
kmem_cache_destroy(fscrypt_info_cachep);
|
|
fail_free_ctx:
|
|
kmem_cache_destroy(fscrypt_ctx_cachep);
|
|
fail_free_queue:
|
|
destroy_workqueue(fscrypt_read_workqueue);
|
|
fail:
|
|
return err;
|
|
}
|
|
late_initcall(fscrypt_init)
|