diff options
Diffstat (limited to 'fs/ext4/crypto.c')
| -rw-r--r-- | fs/ext4/crypto.c | 558 |
1 files changed, 558 insertions, 0 deletions
diff --git a/fs/ext4/crypto.c b/fs/ext4/crypto.c new file mode 100644 index 000000000000..8ff15273ab0c --- /dev/null +++ b/fs/ext4/crypto.c @@ -0,0 +1,558 @@ +/* + * linux/fs/ext4/crypto.c + * + * Copyright (C) 2015, Google, Inc. + * + * This contains encryption functions for ext4 + * + * Written by Michael Halcrow, 2014. + * + * Filename encryption additions + * Uday Savagaonkar, 2014 + * Encryption policy handling additions + * Ildar Muslukhov, 2014 + * + * 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/hash.h> +#include <crypto/sha.h> +#include <keys/user-type.h> +#include <keys/encrypted-type.h> +#include <linux/crypto.h> +#include <linux/ecryptfs.h> +#include <linux/gfp.h> +#include <linux/kernel.h> +#include <linux/key.h> +#include <linux/list.h> +#include <linux/mempool.h> +#include <linux/module.h> +#include <linux/mutex.h> +#include <linux/random.h> +#include <linux/scatterlist.h> +#include <linux/spinlock_types.h> + +#include "ext4_extents.h" +#include "xattr.h" + +/* Encryption added and removed here! (L: */ + +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 *ext4_bounce_page_pool; + +static LIST_HEAD(ext4_free_crypto_ctxs); +static DEFINE_SPINLOCK(ext4_crypto_ctx_lock); + +/** + * ext4_release_crypto_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 ext4_release_crypto_ctx(struct ext4_crypto_ctx *ctx) +{ + unsigned long flags; + + if (ctx->bounce_page) { + if (ctx->flags & EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL) + __free_page(ctx->bounce_page); + else + mempool_free(ctx->bounce_page, ext4_bounce_page_pool); + ctx->bounce_page = NULL; + } + ctx->control_page = NULL; + if (ctx->flags & EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL) { + if (ctx->tfm) + crypto_free_tfm(ctx->tfm); + kfree(ctx); + } else { + spin_lock_irqsave(&ext4_crypto_ctx_lock, flags); + list_add(&ctx->free_list, &ext4_free_crypto_ctxs); + spin_unlock_irqrestore(&ext4_crypto_ctx_lock, flags); + } +} + +/** + * ext4_alloc_and_init_crypto_ctx() - Allocates and inits an encryption context + * @mask: The allocation mask. + * + * Return: An allocated and initialized encryption context on success. An error + * value or NULL otherwise. + */ +static struct ext4_crypto_ctx *ext4_alloc_and_init_crypto_ctx(gfp_t mask) +{ + struct ext4_crypto_ctx *ctx = kzalloc(sizeof(struct ext4_crypto_ctx), + mask); + + if (!ctx) + return ERR_PTR(-ENOMEM); + return ctx; +} + +/** + * ext4_get_crypto_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 ext4_crypto_ctx *ext4_get_crypto_ctx(struct inode *inode) +{ + struct ext4_crypto_ctx *ctx = NULL; + int res = 0; + unsigned long flags; + struct ext4_encryption_key *key = &EXT4_I(inode)->i_encryption_key; + + if (!ext4_read_workqueue) + ext4_init_crypto(); + + /* + * 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(&ext4_crypto_ctx_lock, flags); + ctx = list_first_entry_or_null(&ext4_free_crypto_ctxs, + struct ext4_crypto_ctx, free_list); + if (ctx) + list_del(&ctx->free_list); + spin_unlock_irqrestore(&ext4_crypto_ctx_lock, flags); + if (!ctx) { + ctx = ext4_alloc_and_init_crypto_ctx(GFP_NOFS); + if (IS_ERR(ctx)) { + res = PTR_ERR(ctx); + goto out; + } + ctx->flags |= EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL; + } else { + ctx->flags &= ~EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL; + } + + /* Allocate a new Crypto API context if we don't already have + * one or if it isn't the right mode. */ + BUG_ON(key->mode == EXT4_ENCRYPTION_MODE_INVALID); + if (ctx->tfm && (ctx->mode != key->mode)) { + crypto_free_tfm(ctx->tfm); + ctx->tfm = NULL; + ctx->mode = EXT4_ENCRYPTION_MODE_INVALID; + } + if (!ctx->tfm) { + switch (key->mode) { + case EXT4_ENCRYPTION_MODE_AES_256_XTS: + ctx->tfm = crypto_ablkcipher_tfm( + crypto_alloc_ablkcipher("xts(aes)", 0, 0)); + break; + case EXT4_ENCRYPTION_MODE_AES_256_GCM: + /* TODO(mhalcrow): AEAD w/ gcm(aes); + * crypto_aead_setauthsize() */ + ctx->tfm = ERR_PTR(-ENOTSUPP); + break; + default: + BUG(); + } + if (IS_ERR_OR_NULL(ctx->tfm)) { + res = PTR_ERR(ctx->tfm); + ctx->tfm = NULL; + goto out; + } + ctx->mode = key->mode; + } + BUG_ON(key->size != ext4_encryption_key_size(key->mode)); + + /* There shouldn't be a bounce page attached to the crypto + * context at this point. */ + BUG_ON(ctx->bounce_page); + +out: + if (res) { + if (!IS_ERR_OR_NULL(ctx)) + ext4_release_crypto_ctx(ctx); + ctx = ERR_PTR(res); + } + return ctx; +} + +struct workqueue_struct *ext4_read_workqueue; +static DEFINE_MUTEX(crypto_init); + +/** + * ext4_exit_crypto() - Shutdown the ext4 encryption system + */ +void ext4_exit_crypto(void) +{ + struct ext4_crypto_ctx *pos, *n; + + list_for_each_entry_safe(pos, n, &ext4_free_crypto_ctxs, free_list) { + if (pos->bounce_page) { + if (pos->flags & + EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL) { + __free_page(pos->bounce_page); + } else { + mempool_free(pos->bounce_page, + ext4_bounce_page_pool); + } + } + if (pos->tfm) + crypto_free_tfm(pos->tfm); + kfree(pos); + } + INIT_LIST_HEAD(&ext4_free_crypto_ctxs); + if (ext4_bounce_page_pool) + mempool_destroy(ext4_bounce_page_pool); + ext4_bounce_page_pool = NULL; + if (ext4_read_workqueue) + destroy_workqueue(ext4_read_workqueue); + ext4_read_workqueue = NULL; +} + +/** + * ext4_init_crypto() - Set up for ext4 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 ext4_init_crypto(void) +{ + int i, res; + + mutex_lock(&crypto_init); + if (ext4_read_workqueue) + goto already_initialized; + ext4_read_workqueue = alloc_workqueue("ext4_crypto", WQ_HIGHPRI, 0); + if (!ext4_read_workqueue) { + res = -ENOMEM; + goto fail; + } + + for (i = 0; i < num_prealloc_crypto_ctxs; i++) { + struct ext4_crypto_ctx *ctx; + + ctx = ext4_alloc_and_init_crypto_ctx(GFP_KERNEL); + if (IS_ERR(ctx)) { + res = PTR_ERR(ctx); + goto fail; + } + list_add(&ctx->free_list, &ext4_free_crypto_ctxs); + } + + ext4_bounce_page_pool = + mempool_create_page_pool(num_prealloc_crypto_pages, 0); + if (!ext4_bounce_page_pool) { + res = -ENOMEM; + goto fail; + } +already_initialized: + mutex_unlock(&crypto_init); + return 0; +fail: + ext4_exit_crypto(); + mutex_unlock(&crypto_init); + return res; +} + +void ext4_restore_control_page(struct page *data_page) +{ + struct ext4_crypto_ctx *ctx = + (struct ext4_crypto_ctx *)page_private(data_page); + + set_page_private(data_page, (unsigned long)NULL); + ClearPagePrivate(data_page); + unlock_page(data_page); + ext4_release_crypto_ctx(ctx); +} + +/** + * ext4_crypt_complete() - The completion callback for page encryption + * @req: The asynchronous encryption request context + * @res: The result of the encryption operation + */ +static void ext4_crypt_complete(struct crypto_async_request *req, int res) +{ + struct ext4_completion_result *ecr = req->data; + + if (res == -EINPROGRESS) + return; + ecr->res = res; + complete(&ecr->completion); +} + +typedef enum { + EXT4_DECRYPT = 0, + EXT4_ENCRYPT, +} ext4_direction_t; + +static int ext4_page_crypto(struct ext4_crypto_ctx *ctx, + struct inode *inode, + ext4_direction_t rw, + pgoff_t index, + struct page *src_page, + struct page *dest_page) + +{ + u8 xts_tweak[EXT4_XTS_TWEAK_SIZE]; + struct ablkcipher_request *req = NULL; + DECLARE_EXT4_COMPLETION_RESULT(ecr); + struct scatterlist dst, src; + struct ext4_inode_info *ei = EXT4_I(inode); + struct crypto_ablkcipher *atfm = __crypto_ablkcipher_cast(ctx->tfm); + int res = 0; + + BUG_ON(!ctx->tfm); + BUG_ON(ctx->mode != ei->i_encryption_key.mode); + + if (ctx->mode != EXT4_ENCRYPTION_MODE_AES_256_XTS) { + printk_ratelimited(KERN_ERR + "%s: unsupported crypto algorithm: %d\n", + __func__, ctx->mode); + return -ENOTSUPP; + } + + crypto_ablkcipher_clear_flags(atfm, ~0); + crypto_tfm_set_flags(ctx->tfm, CRYPTO_TFM_REQ_WEAK_KEY); + + res = crypto_ablkcipher_setkey(atfm, ei->i_encryption_key.raw, + ei->i_encryption_key.size); + if (res) { + printk_ratelimited(KERN_ERR + "%s: crypto_ablkcipher_setkey() failed\n", + __func__); + return res; + } + req = ablkcipher_request_alloc(atfm, GFP_NOFS); + if (!req) { + printk_ratelimited(KERN_ERR + "%s: crypto_request_alloc() failed\n", + __func__); + return -ENOMEM; + } + ablkcipher_request_set_callback( + req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, + ext4_crypt_complete, &ecr); + + BUILD_BUG_ON(EXT4_XTS_TWEAK_SIZE < sizeof(index)); + memcpy(xts_tweak, &index, sizeof(index)); + memset(&xts_tweak[sizeof(index)], 0, + EXT4_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); + ablkcipher_request_set_crypt(req, &src, &dst, PAGE_CACHE_SIZE, + xts_tweak); + if (rw == EXT4_DECRYPT) + res = crypto_ablkcipher_decrypt(req); + else + res = crypto_ablkcipher_encrypt(req); + if (res == -EINPROGRESS || res == -EBUSY) { + BUG_ON(req->base.data != &ecr); + wait_for_completion(&ecr.completion); + res = ecr.res; + } + ablkcipher_request_free(req); + if (res) { + printk_ratelimited( + KERN_ERR + "%s: crypto_ablkcipher_encrypt() returned %d\n", + __func__, res); + return res; + } + return 0; +} + +/** + * ext4_encrypt() - 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 + * ext4_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 *ext4_encrypt(struct inode *inode, + struct page *plaintext_page) +{ + struct ext4_crypto_ctx *ctx; + struct page *ciphertext_page = NULL; + int err; + + BUG_ON(!PageLocked(plaintext_page)); + + ctx = ext4_get_crypto_ctx(inode); + if (IS_ERR(ctx)) + return (struct page *) ctx; + + /* The encryption operation will require a bounce page. */ + ciphertext_page = alloc_page(GFP_NOFS); + if (!ciphertext_page) { + /* This is a potential bottleneck, but at least we'll have + * forward progress. */ + ciphertext_page = mempool_alloc(ext4_bounce_page_pool, + GFP_NOFS); + if (WARN_ON_ONCE(!ciphertext_page)) { + ciphertext_page = mempool_alloc(ext4_bounce_page_pool, + GFP_NOFS | __GFP_WAIT); + } + ctx->flags &= ~EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL; + } else { + ctx->flags |= EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL; + } + ctx->bounce_page = ciphertext_page; + ctx->control_page = plaintext_page; + err = ext4_page_crypto(ctx, inode, EXT4_ENCRYPT, plaintext_page->index, + plaintext_page, ciphertext_page); + if (err) { + ext4_release_crypto_ctx(ctx); + return ERR_PTR(err); + } + SetPagePrivate(ciphertext_page); + set_page_private(ciphertext_page, (unsigned long)ctx); + lock_page(ciphertext_page); + return ciphertext_page; +} + +/** + * ext4_decrypt() - Decrypts a page in-place + * @ctx: The encryption context. + * @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 ext4_decrypt(struct ext4_crypto_ctx *ctx, struct page *page) +{ + BUG_ON(!PageLocked(page)); + + return ext4_page_crypto(ctx, page->mapping->host, + EXT4_DECRYPT, page->index, page, page); +} + +/* + * Convenience function which takes care of allocating and + * deallocating the encryption context + */ +int ext4_decrypt_one(struct inode *inode, struct page *page) +{ + int ret; + + struct ext4_crypto_ctx *ctx = ext4_get_crypto_ctx(inode); + + if (!ctx) + return -ENOMEM; + ret = ext4_decrypt(ctx, page); + ext4_release_crypto_ctx(ctx); + return ret; +} + +int ext4_encrypted_zeroout(struct inode *inode, struct ext4_extent *ex) +{ + struct ext4_crypto_ctx *ctx; + struct page *ciphertext_page = NULL; + struct bio *bio; + ext4_lblk_t lblk = ex->ee_block; + ext4_fsblk_t pblk = ext4_ext_pblock(ex); + unsigned int len = ext4_ext_get_actual_len(ex); + int err = 0; + + BUG_ON(inode->i_sb->s_blocksize != PAGE_CACHE_SIZE); + + ctx = ext4_get_crypto_ctx(inode); + if (IS_ERR(ctx)) + return PTR_ERR(ctx); + + ciphertext_page = alloc_page(GFP_NOFS); + if (!ciphertext_page) { + /* This is a potential bottleneck, but at least we'll have + * forward progress. */ + ciphertext_page = mempool_alloc(ext4_bounce_page_pool, + GFP_NOFS); + if (WARN_ON_ONCE(!ciphertext_page)) { + ciphertext_page = mempool_alloc(ext4_bounce_page_pool, + GFP_NOFS | __GFP_WAIT); + } + ctx->flags &= ~EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL; + } else { + ctx->flags |= EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL; + } + ctx->bounce_page = ciphertext_page; + + while (len--) { + err = ext4_page_crypto(ctx, inode, EXT4_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; + err = bio_add_page(bio, ciphertext_page, + inode->i_sb->s_blocksize, 0); + if (err) { + bio_put(bio); + goto errout; + } + err = submit_bio_wait(WRITE, bio); + if (err) + goto errout; + } + err = 0; +errout: + ext4_release_crypto_ctx(ctx); + return err; +} + +bool ext4_valid_contents_enc_mode(uint32_t mode) +{ + return (mode == EXT4_ENCRYPTION_MODE_AES_256_XTS); +} + +/** + * ext4_validate_encryption_key_size() - Validate the encryption key size + * @mode: The key mode. + * @size: The key size to validate. + * + * Return: The validated key size for @mode. Zero if invalid. + */ +uint32_t ext4_validate_encryption_key_size(uint32_t mode, uint32_t size) +{ + if (size == ext4_encryption_key_size(mode)) + return size; + return 0; +} |