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Diffstat (limited to 'fs/crypto/crypto.c')
| -rw-r--r-- | fs/crypto/crypto.c | 346 |
1 files changed, 346 insertions, 0 deletions
diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c new file mode 100644 index 000000000..5286a124b --- /dev/null +++ b/fs/crypto/crypto.c @@ -0,0 +1,346 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * This contains encryption functions for per-file encryption. + * + * Copyright (C) 2015, Google, Inc. + * Copyright (C) 2015, Motorola Mobility + * + * Written by Michael Halcrow, 2014. + * + * Filename encryption additions + * Uday Savagaonkar, 2014 + * Encryption policy handling additions + * Ildar Muslukhov, 2014 + * Add fscrypt_pullback_bio_page() + * Jaegeuk Kim, 2015. + * + * This has not yet undergone a rigorous security audit. + * + * The usage of AES-XTS should conform to recommendations in NIST + * Special Publication 800-38E and IEEE P1619/D16. + */ + +#include <crypto/skcipher.h> +#include <linux/export.h> +#include <linux/mempool.h> +#include <linux/module.h> +#include <linux/pagemap.h> +#include <linux/ratelimit.h> +#include <linux/scatterlist.h> + +#include "fscrypt_private.h" + +static unsigned int num_prealloc_crypto_pages = 32; + +module_param(num_prealloc_crypto_pages, uint, 0444); +MODULE_PARM_DESC(num_prealloc_crypto_pages, + "Number of crypto pages to preallocate"); + +static mempool_t *fscrypt_bounce_page_pool = NULL; + +static DEFINE_MUTEX(fscrypt_init_mutex); + +struct kmem_cache *fscrypt_inode_info_cachep; + +static struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags) +{ + if (WARN_ON_ONCE(!fscrypt_bounce_page_pool)) { + /* + * Oops, the filesystem called a function that uses the bounce + * page pool, but it didn't set needs_bounce_pages. + */ + return NULL; + } + return mempool_alloc(fscrypt_bounce_page_pool, gfp_flags); +} + +/** + * fscrypt_free_bounce_page() - free a ciphertext bounce page + * @bounce_page: the bounce page to free, or NULL + * + * Free a bounce page that was allocated by fscrypt_encrypt_pagecache_blocks(). + */ +void fscrypt_free_bounce_page(struct page *bounce_page) +{ + if (!bounce_page) + return; + set_page_private(bounce_page, (unsigned long)NULL); + ClearPagePrivate(bounce_page); + mempool_free(bounce_page, fscrypt_bounce_page_pool); +} +EXPORT_SYMBOL(fscrypt_free_bounce_page); + +/* + * Generate the IV for the given data unit index within the given file. + * For filenames encryption, index == 0. + * + * Keep this in sync with fscrypt_limit_io_blocks(). fscrypt_limit_io_blocks() + * needs to know about any IV generation methods where the low bits of IV don't + * simply contain the data unit index (e.g., IV_INO_LBLK_32). + */ +void fscrypt_generate_iv(union fscrypt_iv *iv, u64 index, + const struct fscrypt_inode_info *ci) +{ + u8 flags = fscrypt_policy_flags(&ci->ci_policy); + + memset(iv, 0, sizeof(*iv)); + + if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) { + WARN_ON_ONCE(index > U32_MAX); + WARN_ON_ONCE(ci->ci_inode->i_ino > U32_MAX); + index |= (u64)ci->ci_inode->i_ino << 32; + } else if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) { + WARN_ON_ONCE(index > U32_MAX); + index = (u32)(ci->ci_hashed_ino + index); + } else if (flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { + memcpy(iv->nonce, ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE); + } + iv->index = cpu_to_le64(index); +} + +/* Encrypt or decrypt a single "data unit" of file contents. */ +static int fscrypt_crypt_data_unit(const struct fscrypt_inode_info *ci, + fscrypt_direction_t rw, u64 index, + struct page *src_page, + struct page *dest_page, unsigned int len, + unsigned int offs) +{ + struct crypto_sync_skcipher *tfm; + union fscrypt_iv iv; + struct scatterlist dst, src; + int err; + + if (WARN_ON_ONCE(ci == NULL)) /* File hasn't been opened yet? */ + return -ENOKEY; + tfm = ci->ci_enc_key.tfm; + if (WARN_ON_ONCE(tfm == NULL)) /* Called on block-based filesystem? */ + return -ENOKEY; + + if (WARN_ON_ONCE(len <= 0)) + return -EINVAL; + if (WARN_ON_ONCE(len % FSCRYPT_CONTENTS_ALIGNMENT != 0)) + return -EINVAL; + + fscrypt_generate_iv(&iv, index, ci); + + { + SYNC_SKCIPHER_REQUEST_ON_STACK(req, tfm); + skcipher_request_set_callback(req, + CRYPTO_TFM_REQ_MAY_BACKLOG | + CRYPTO_TFM_REQ_MAY_SLEEP, + NULL, NULL); + sg_init_table(&dst, 1); + sg_set_page(&dst, dest_page, len, offs); + sg_init_table(&src, 1); + sg_set_page(&src, src_page, len, offs); + skcipher_request_set_crypt(req, &src, &dst, len, &iv); + if (rw == FS_DECRYPT) + err = crypto_skcipher_decrypt(req); + else + err = crypto_skcipher_encrypt(req); + } + if (err) + fscrypt_err(ci->ci_inode, + "%scryption failed for data unit %llu: %d", + (rw == FS_DECRYPT ? "De" : "En"), index, err); + return err; +} + +/** + * fscrypt_encrypt_pagecache_blocks() - Encrypt data from a pagecache folio + * @folio: the locked pagecache folio containing the data to encrypt + * @len: size of the data to encrypt, in bytes + * @offs: offset within @page of the data to encrypt, in bytes + * @gfp_flags: memory allocation flags; see details below + * + * This allocates a new bounce page and encrypts the given data into it. The + * length and offset of the data must be aligned to the file's crypto data unit + * size. Alignment to the filesystem block size fulfills this requirement, as + * the filesystem block size is always a multiple of the data unit size. + * + * In the bounce page, the ciphertext data will be located at the same offset at + * which the plaintext data was located in the source page. Any other parts of + * the bounce page will be left uninitialized. + * + * This is for use by the ->writepages() method of non-block-based filesystems. + * + * The bounce page allocation is mempool-backed, so it will always succeed when + * @gfp_flags includes __GFP_DIRECT_RECLAIM, e.g. when it's GFP_NOFS. However, + * only the first page of each bio can be allocated this way. To prevent + * deadlocks, for any additional pages a mask like GFP_NOWAIT must be used. + * + * Return: the new encrypted bounce page on success; an ERR_PTR() on failure + */ +struct page *fscrypt_encrypt_pagecache_blocks(struct folio *folio, + size_t len, size_t offs, gfp_t gfp_flags) +{ + const struct inode *inode = folio->mapping->host; + const struct fscrypt_inode_info *ci = fscrypt_get_inode_info_raw(inode); + unsigned int du_bits; + unsigned int du_size; + struct page *ciphertext_page; + u64 index; + unsigned int i; + int err; + + if (WARN_ON_ONCE(ci == NULL)) /* File hasn't been opened yet? */ + return ERR_PTR(-ENOKEY); + + du_bits = ci->ci_data_unit_bits; + du_size = 1U << du_bits; + index = (folio_pos(folio) + offs) >> du_bits; + + VM_BUG_ON_FOLIO(folio_test_large(folio), folio); + if (WARN_ON_ONCE(!folio_test_locked(folio))) + return ERR_PTR(-EINVAL); + + if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, du_size))) + return ERR_PTR(-EINVAL); + + ciphertext_page = fscrypt_alloc_bounce_page(gfp_flags); + if (!ciphertext_page) + return ERR_PTR(-ENOMEM); + + for (i = offs; i < offs + len; i += du_size, index++) { + err = fscrypt_crypt_data_unit(ci, FS_ENCRYPT, index, + &folio->page, ciphertext_page, + du_size, i); + if (err) { + fscrypt_free_bounce_page(ciphertext_page); + return ERR_PTR(err); + } + } + SetPagePrivate(ciphertext_page); + set_page_private(ciphertext_page, (unsigned long)folio); + return ciphertext_page; +} +EXPORT_SYMBOL(fscrypt_encrypt_pagecache_blocks); + +/** + * fscrypt_encrypt_block_inplace() - Encrypt a filesystem block in-place + * @inode: The inode to which this block belongs + * @page: The page containing the block to encrypt + * @len: Size of block to encrypt. This must be a multiple of + * FSCRYPT_CONTENTS_ALIGNMENT. + * @offs: Byte offset within @page at which the block to encrypt begins + * @lblk_num: Filesystem logical block number of the block, i.e. the 0-based + * number of the block within the file + * + * Encrypt a possibly-compressed filesystem block that is located in an + * arbitrary page, not necessarily in the original pagecache page. The @inode + * and @lblk_num must be specified, as they can't be determined from @page. + * + * This function only supports non-block-based filesystems that don't support + * sub-block data units (as indicated by the fscrypt_operations fields). + * + * Return: 0 on success; -errno on failure + */ +int fscrypt_encrypt_block_inplace(const struct inode *inode, struct page *page, + unsigned int len, unsigned int offs, + u64 lblk_num) +{ + if (WARN_ON_ONCE(inode->i_sb->s_cop->supports_subblock_data_units)) + return -EOPNOTSUPP; + return fscrypt_crypt_data_unit(fscrypt_get_inode_info_raw(inode), + FS_ENCRYPT, lblk_num, page, page, len, + offs); +} +EXPORT_SYMBOL(fscrypt_encrypt_block_inplace); + +/** + * fscrypt_decrypt_block_inplace() - Decrypt a filesystem block in-place + * @inode: The inode to which this block belongs + * @page: The page containing the block to decrypt + * @len: Size of block to decrypt. This must be a multiple of + * FSCRYPT_CONTENTS_ALIGNMENT. + * @offs: Byte offset within @page at which the block to decrypt begins + * @lblk_num: Filesystem logical block number of the block, i.e. the 0-based + * number of the block within the file + * + * Decrypt a possibly-compressed filesystem block that is located in an + * arbitrary page, not necessarily in the original pagecache page. The @inode + * and @lblk_num must be specified, as they can't be determined from @page. + * + * This function only supports non-block-based filesystems that don't support + * sub-block data units (as indicated by the fscrypt_operations fields). + * + * Return: 0 on success; -errno on failure + */ +int fscrypt_decrypt_block_inplace(const struct inode *inode, struct page *page, + unsigned int len, unsigned int offs, + u64 lblk_num) +{ + if (WARN_ON_ONCE(inode->i_sb->s_cop->supports_subblock_data_units)) + return -EOPNOTSUPP; + return fscrypt_crypt_data_unit(fscrypt_get_inode_info_raw(inode), + FS_DECRYPT, lblk_num, page, page, len, + offs); +} +EXPORT_SYMBOL(fscrypt_decrypt_block_inplace); + +/** + * fscrypt_initialize() - allocate major buffers for fs encryption. + * @sb: the filesystem superblock + * + * We only call this when we start accessing encrypted files, since it + * results in memory getting allocated that wouldn't otherwise be used. + * + * Return: 0 on success; -errno on failure + */ +int fscrypt_initialize(struct super_block *sb) +{ + mempool_t *pool; + + /* pairs with smp_store_release() below */ + if (smp_load_acquire(&fscrypt_bounce_page_pool)) + return 0; + + /* No need to allocate a bounce page pool if this FS won't use it. */ + if (!sb->s_cop->needs_bounce_pages) + return 0; + + guard(mutex)(&fscrypt_init_mutex); + if (fscrypt_bounce_page_pool) + return 0; + + pool = mempool_create_page_pool(num_prealloc_crypto_pages, 0); + if (!pool) + return -ENOMEM; + /* pairs with smp_load_acquire() above */ + smp_store_release(&fscrypt_bounce_page_pool, pool); + return 0; +} + +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 && inode->i_ino) + printk("%sfscrypt (%s, inode %llu): %pV\n", + level, inode->i_sb->s_id, inode->i_ino, &vaf); + else if (inode) + printk("%sfscrypt (%s): %pV\n", level, inode->i_sb->s_id, &vaf); + else + printk("%sfscrypt: %pV\n", level, &vaf); + va_end(args); +} + +static int __init fscrypt_init(void) +{ + fscrypt_inode_info_cachep = KMEM_CACHE(fscrypt_inode_info, + SLAB_RECLAIM_ACCOUNT | + SLAB_PANIC); + fscrypt_init_keyring(); + return 0; +} +late_initcall(fscrypt_init) |