| /* |
| * 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 <linux/pagemap.h> |
| #include <linux/mempool.h> |
| #include <linux/module.h> |
| #include <linux/scatterlist.h> |
| #include <linux/ratelimit.h> |
| #include <linux/bio.h> |
| #include <linux/dcache.h> |
| #include <linux/fscrypto.h> |
| #include <linux/ecryptfs.h> |
| |
| static unsigned int num_prealloc_crypto_pages = 32; |
| static unsigned int num_prealloc_crypto_ctxs = 128; |
| |
| module_param(num_prealloc_crypto_pages, uint, 0444); |
| MODULE_PARM_DESC(num_prealloc_crypto_pages, |
| "Number of crypto pages to preallocate"); |
| module_param(num_prealloc_crypto_ctxs, uint, 0444); |
| MODULE_PARM_DESC(num_prealloc_crypto_ctxs, |
| "Number of crypto contexts to preallocate"); |
| |
| static mempool_t *fscrypt_bounce_page_pool = NULL; |
| |
| static LIST_HEAD(fscrypt_free_ctxs); |
| static DEFINE_SPINLOCK(fscrypt_ctx_lock); |
| |
| static struct workqueue_struct *fscrypt_read_workqueue; |
| static DEFINE_MUTEX(fscrypt_init_mutex); |
| |
| static struct kmem_cache *fscrypt_ctx_cachep; |
| struct kmem_cache *fscrypt_info_cachep; |
| |
| /** |
| * fscrypt_release_ctx() - Releases an encryption context |
| * @ctx: The encryption context to release. |
| * |
| * If the encryption context was allocated from the pre-allocated pool, returns |
| * it to that pool. Else, frees it. |
| * |
| * If there's a bounce page in the context, this frees that. |
| */ |
| void fscrypt_release_ctx(struct fscrypt_ctx *ctx) |
| { |
| unsigned long flags; |
| |
| if (ctx->flags & FS_WRITE_PATH_FL && ctx->w.bounce_page) { |
| mempool_free(ctx->w.bounce_page, fscrypt_bounce_page_pool); |
| ctx->w.bounce_page = NULL; |
| } |
| ctx->w.control_page = NULL; |
| if (ctx->flags & FS_CTX_REQUIRES_FREE_ENCRYPT_FL) { |
| kmem_cache_free(fscrypt_ctx_cachep, ctx); |
| } else { |
| spin_lock_irqsave(&fscrypt_ctx_lock, flags); |
| list_add(&ctx->free_list, &fscrypt_free_ctxs); |
| spin_unlock_irqrestore(&fscrypt_ctx_lock, flags); |
| } |
| } |
| EXPORT_SYMBOL(fscrypt_release_ctx); |
| |
| /** |
| * fscrypt_get_ctx() - Gets an encryption context |
| * @inode: The inode for which we are doing the crypto |
| * |
| * Allocates and initializes an encryption context. |
| * |
| * Return: An allocated and initialized encryption context on success; error |
| * value or NULL otherwise. |
| */ |
| struct fscrypt_ctx *fscrypt_get_ctx(struct inode *inode) |
| { |
| struct fscrypt_ctx *ctx = NULL; |
| struct fscrypt_info *ci = inode->i_crypt_info; |
| unsigned long flags; |
| |
| if (ci == NULL) |
| return ERR_PTR(-ENOKEY); |
| |
| /* |
| * We first try getting the ctx from a free list because in |
| * the common case the ctx will have an allocated and |
| * initialized crypto tfm, so it's probably a worthwhile |
| * optimization. For the bounce page, we first try getting it |
| * from the kernel allocator because that's just about as fast |
| * as getting it from a list and because a cache of free pages |
| * should generally be a "last resort" option for a filesystem |
| * to be able to do its job. |
| */ |
| spin_lock_irqsave(&fscrypt_ctx_lock, flags); |
| ctx = list_first_entry_or_null(&fscrypt_free_ctxs, |
| struct fscrypt_ctx, free_list); |
| if (ctx) |
| list_del(&ctx->free_list); |
| spin_unlock_irqrestore(&fscrypt_ctx_lock, flags); |
| if (!ctx) { |
| ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, GFP_NOFS); |
| if (!ctx) |
| return ERR_PTR(-ENOMEM); |
| ctx->flags |= FS_CTX_REQUIRES_FREE_ENCRYPT_FL; |
| } else { |
| ctx->flags &= ~FS_CTX_REQUIRES_FREE_ENCRYPT_FL; |
| } |
| ctx->flags &= ~FS_WRITE_PATH_FL; |
| return ctx; |
| } |
| EXPORT_SYMBOL(fscrypt_get_ctx); |
| |
| /** |
| * fscrypt_complete() - The completion callback for page encryption |
| * @req: The asynchronous encryption request context |
| * @res: The result of the encryption operation |
| */ |
| static void fscrypt_complete(struct crypto_async_request *req, int res) |
| { |
| struct fscrypt_completion_result *ecr = req->data; |
| |
| if (res == -EINPROGRESS) |
| return; |
| ecr->res = res; |
| complete(&ecr->completion); |
| } |
| |
| typedef enum { |
| FS_DECRYPT = 0, |
| FS_ENCRYPT, |
| } fscrypt_direction_t; |
| |
| static int do_page_crypto(struct inode *inode, |
| fscrypt_direction_t rw, pgoff_t index, |
| struct page *src_page, struct page *dest_page) |
| { |
| u8 xts_tweak[FS_XTS_TWEAK_SIZE]; |
| struct skcipher_request *req = NULL; |
| DECLARE_FS_COMPLETION_RESULT(ecr); |
| struct scatterlist dst, src; |
| struct fscrypt_info *ci = inode->i_crypt_info; |
| struct crypto_skcipher *tfm = ci->ci_ctfm; |
| int res = 0; |
| |
| req = skcipher_request_alloc(tfm, GFP_NOFS); |
| if (!req) { |
| printk_ratelimited(KERN_ERR |
| "%s: crypto_request_alloc() failed\n", |
| __func__); |
| return -ENOMEM; |
| } |
| |
| skcipher_request_set_callback( |
| req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, |
| fscrypt_complete, &ecr); |
| |
| BUILD_BUG_ON(FS_XTS_TWEAK_SIZE < sizeof(index)); |
| memcpy(xts_tweak, &index, sizeof(index)); |
| memset(&xts_tweak[sizeof(index)], 0, |
| FS_XTS_TWEAK_SIZE - sizeof(index)); |
| |
| sg_init_table(&dst, 1); |
| sg_set_page(&dst, dest_page, PAGE_CACHE_SIZE, 0); |
| sg_init_table(&src, 1); |
| sg_set_page(&src, src_page, PAGE_CACHE_SIZE, 0); |
| skcipher_request_set_crypt(req, &src, &dst, PAGE_CACHE_SIZE, |
| xts_tweak); |
| if (rw == FS_DECRYPT) |
| res = crypto_skcipher_decrypt(req); |
| else |
| res = crypto_skcipher_encrypt(req); |
| if (res == -EINPROGRESS || res == -EBUSY) { |
| BUG_ON(req->base.data != &ecr); |
| wait_for_completion(&ecr.completion); |
| res = ecr.res; |
| } |
| skcipher_request_free(req); |
| if (res) { |
| printk_ratelimited(KERN_ERR |
| "%s: crypto_skcipher_encrypt() returned %d\n", |
| __func__, res); |
| return res; |
| } |
| return 0; |
| } |
| |
| static struct page *alloc_bounce_page(struct fscrypt_ctx *ctx) |
| { |
| ctx->w.bounce_page = mempool_alloc(fscrypt_bounce_page_pool, |
| GFP_NOWAIT); |
| if (ctx->w.bounce_page == NULL) |
| return ERR_PTR(-ENOMEM); |
| ctx->flags |= FS_WRITE_PATH_FL; |
| return ctx->w.bounce_page; |
| } |
| |
| /** |
| * fscypt_encrypt_page() - Encrypts a page |
| * @inode: The inode for which the encryption should take place |
| * @plaintext_page: The page to encrypt. Must be locked. |
| * |
| * Allocates a ciphertext page and encrypts plaintext_page into it using the ctx |
| * encryption context. |
| * |
| * Called on the page write path. The caller must call |
| * fscrypt_restore_control_page() on the returned ciphertext page to |
| * release the bounce buffer and the encryption context. |
| * |
| * Return: An allocated page with the encrypted content on success. Else, an |
| * error value or NULL. |
| */ |
| struct page *fscrypt_encrypt_page(struct inode *inode, |
| struct page *plaintext_page) |
| { |
| struct fscrypt_ctx *ctx; |
| struct page *ciphertext_page = NULL; |
| int err; |
| |
| BUG_ON(!PageLocked(plaintext_page)); |
| |
| ctx = fscrypt_get_ctx(inode); |
| if (IS_ERR(ctx)) |
| return (struct page *)ctx; |
| |
| /* The encryption operation will require a bounce page. */ |
| ciphertext_page = alloc_bounce_page(ctx); |
| if (IS_ERR(ciphertext_page)) |
| goto errout; |
| |
| ctx->w.control_page = plaintext_page; |
| err = do_page_crypto(inode, FS_ENCRYPT, plaintext_page->index, |
| plaintext_page, ciphertext_page); |
| if (err) { |
| ciphertext_page = ERR_PTR(err); |
| goto errout; |
| } |
| SetPagePrivate(ciphertext_page); |
| set_page_private(ciphertext_page, (unsigned long)ctx); |
| lock_page(ciphertext_page); |
| return ciphertext_page; |
| |
| errout: |
| fscrypt_release_ctx(ctx); |
| return ciphertext_page; |
| } |
| EXPORT_SYMBOL(fscrypt_encrypt_page); |
| |
| /** |
| * f2crypt_decrypt_page() - Decrypts a page in-place |
| * @page: The page to decrypt. Must be locked. |
| * |
| * Decrypts page in-place using the ctx encryption context. |
| * |
| * Called from the read completion callback. |
| * |
| * Return: Zero on success, non-zero otherwise. |
| */ |
| int fscrypt_decrypt_page(struct page *page) |
| { |
| BUG_ON(!PageLocked(page)); |
| |
| return do_page_crypto(page->mapping->host, |
| FS_DECRYPT, page->index, page, page); |
| } |
| EXPORT_SYMBOL(fscrypt_decrypt_page); |
| |
| int fscrypt_zeroout_range(struct inode *inode, pgoff_t lblk, |
| sector_t pblk, unsigned int len) |
| { |
| struct fscrypt_ctx *ctx; |
| struct page *ciphertext_page = NULL; |
| struct bio *bio; |
| int ret, err = 0; |
| |
| BUG_ON(inode->i_sb->s_blocksize != PAGE_CACHE_SIZE); |
| |
| ctx = fscrypt_get_ctx(inode); |
| if (IS_ERR(ctx)) |
| return PTR_ERR(ctx); |
| |
| ciphertext_page = alloc_bounce_page(ctx); |
| if (IS_ERR(ciphertext_page)) { |
| err = PTR_ERR(ciphertext_page); |
| goto errout; |
| } |
| |
| while (len--) { |
| err = do_page_crypto(inode, FS_ENCRYPT, lblk, |
| ZERO_PAGE(0), ciphertext_page); |
| if (err) |
| goto errout; |
| |
| bio = bio_alloc(GFP_KERNEL, 1); |
| if (!bio) { |
| err = -ENOMEM; |
| goto errout; |
| } |
| bio->bi_bdev = inode->i_sb->s_bdev; |
| bio->bi_iter.bi_sector = |
| pblk << (inode->i_sb->s_blocksize_bits - 9); |
| ret = bio_add_page(bio, ciphertext_page, |
| inode->i_sb->s_blocksize, 0); |
| if (ret != inode->i_sb->s_blocksize) { |
| /* should never happen! */ |
| WARN_ON(1); |
| bio_put(bio); |
| err = -EIO; |
| goto errout; |
| } |
| err = submit_bio_wait(WRITE, bio); |
| if ((err == 0) && bio->bi_error) |
| err = -EIO; |
| bio_put(bio); |
| if (err) |
| goto errout; |
| lblk++; |
| pblk++; |
| } |
| err = 0; |
| errout: |
| fscrypt_release_ctx(ctx); |
| return err; |
| } |
| EXPORT_SYMBOL(fscrypt_zeroout_range); |
| |
| /* |
| * Validate dentries for encrypted directories to make sure we aren't |
| * potentially caching stale data after a key has been added or |
| * removed. |
| */ |
| static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags) |
| { |
| struct inode *dir = d_inode(dentry->d_parent); |
| struct fscrypt_info *ci = dir->i_crypt_info; |
| int dir_has_key, cached_with_key; |
| |
| if (!dir->i_sb->s_cop->is_encrypted(dir)) |
| return 0; |
| |
| if (ci && ci->ci_keyring_key && |
| (ci->ci_keyring_key->flags & ((1 << KEY_FLAG_INVALIDATED) | |
| (1 << KEY_FLAG_REVOKED) | |
| (1 << KEY_FLAG_DEAD)))) |
| ci = NULL; |
| |
| /* this should eventually be an flag in d_flags */ |
| spin_lock(&dentry->d_lock); |
| cached_with_key = dentry->d_flags & DCACHE_ENCRYPTED_WITH_KEY; |
| spin_unlock(&dentry->d_lock); |
| dir_has_key = (ci != NULL); |
| |
| /* |
| * If the dentry was cached without the key, and it is a |
| * negative dentry, it might be a valid name. We can't check |
| * if the key has since been made available due to locking |
| * reasons, so we fail the validation so ext4_lookup() can do |
| * this check. |
| * |
| * We also fail the validation if the dentry was created with |
| * the key present, but we no longer have the key, or vice versa. |
| */ |
| if ((!cached_with_key && d_is_negative(dentry)) || |
| (!cached_with_key && dir_has_key) || |
| (cached_with_key && !dir_has_key)) |
| return 0; |
| return 1; |
| } |
| |
| const struct dentry_operations fscrypt_d_ops = { |
| .d_revalidate = fscrypt_d_revalidate, |
| }; |
| EXPORT_SYMBOL(fscrypt_d_ops); |
| |
| /* |
| * Call fscrypt_decrypt_page on every single page, reusing the encryption |
| * context. |
| */ |
| static void completion_pages(struct work_struct *work) |
| { |
| struct fscrypt_ctx *ctx = |
| container_of(work, struct fscrypt_ctx, r.work); |
| struct bio *bio = ctx->r.bio; |
| struct bio_vec *bv; |
| int i; |
| |
| bio_for_each_segment_all(bv, bio, i) { |
| struct page *page = bv->bv_page; |
| int ret = fscrypt_decrypt_page(page); |
| |
| if (ret) { |
| WARN_ON_ONCE(1); |
| SetPageError(page); |
| } else { |
| SetPageUptodate(page); |
| } |
| unlock_page(page); |
| } |
| fscrypt_release_ctx(ctx); |
| bio_put(bio); |
| } |
| |
| void fscrypt_decrypt_bio_pages(struct fscrypt_ctx *ctx, struct bio *bio) |
| { |
| INIT_WORK(&ctx->r.work, completion_pages); |
| ctx->r.bio = bio; |
| queue_work(fscrypt_read_workqueue, &ctx->r.work); |
| } |
| EXPORT_SYMBOL(fscrypt_decrypt_bio_pages); |
| |
| void fscrypt_pullback_bio_page(struct page **page, bool restore) |
| { |
| struct fscrypt_ctx *ctx; |
| struct page *bounce_page; |
| |
| /* The bounce data pages are unmapped. */ |
| if ((*page)->mapping) |
| return; |
| |
| /* The bounce data page is unmapped. */ |
| bounce_page = *page; |
| ctx = (struct fscrypt_ctx *)page_private(bounce_page); |
| |
| /* restore control page */ |
| *page = ctx->w.control_page; |
| |
| if (restore) |
| fscrypt_restore_control_page(bounce_page); |
| } |
| EXPORT_SYMBOL(fscrypt_pullback_bio_page); |
| |
| void fscrypt_restore_control_page(struct page *page) |
| { |
| struct fscrypt_ctx *ctx; |
| |
| ctx = (struct fscrypt_ctx *)page_private(page); |
| set_page_private(page, (unsigned long)NULL); |
| ClearPagePrivate(page); |
| unlock_page(page); |
| fscrypt_release_ctx(ctx); |
| } |
| EXPORT_SYMBOL(fscrypt_restore_control_page); |
| |
| static void fscrypt_destroy(void) |
| { |
| struct fscrypt_ctx *pos, *n; |
| |
| list_for_each_entry_safe(pos, n, &fscrypt_free_ctxs, free_list) |
| kmem_cache_free(fscrypt_ctx_cachep, pos); |
| INIT_LIST_HEAD(&fscrypt_free_ctxs); |
| mempool_destroy(fscrypt_bounce_page_pool); |
| fscrypt_bounce_page_pool = NULL; |
| } |
| |
| /** |
| * fscrypt_initialize() - allocate major buffers for fs encryption. |
| * |
| * We only call this when we start accessing encrypted files, since it |
| * results in memory getting allocated that wouldn't otherwise be used. |
| * |
| * Return: Zero on success, non-zero otherwise. |
| */ |
| int fscrypt_initialize(void) |
| { |
| int i, res = -ENOMEM; |
| |
| if (fscrypt_bounce_page_pool) |
| 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; |
| } |
| EXPORT_SYMBOL(fscrypt_initialize); |
| |
| /** |
| * fscrypt_init() - Set up for fs encryption. |
| */ |
| static int __init fscrypt_init(void) |
| { |
| fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue", |
| WQ_HIGHPRI, 0); |
| 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; |
| |
| return 0; |
| |
| fail_free_ctx: |
| kmem_cache_destroy(fscrypt_ctx_cachep); |
| fail_free_queue: |
| destroy_workqueue(fscrypt_read_workqueue); |
| fail: |
| return -ENOMEM; |
| } |
| module_init(fscrypt_init) |
| |
| /** |
| * fscrypt_exit() - Shutdown the fs encryption system |
| */ |
| static void __exit fscrypt_exit(void) |
| { |
| fscrypt_destroy(); |
| |
| if (fscrypt_read_workqueue) |
| destroy_workqueue(fscrypt_read_workqueue); |
| kmem_cache_destroy(fscrypt_ctx_cachep); |
| kmem_cache_destroy(fscrypt_info_cachep); |
| } |
| module_exit(fscrypt_exit); |
| |
| MODULE_LICENSE("GPL"); |