This patch adds crypto.c supporting encrypting and decrypting functions.
1. IO preparation:
- fscrypt_get_ctx / fscrypt_release_ctx
2. before IOs:
- fscrypt_encrypt_page
- fscrypt_decrypt_page
- fscrypt_zeroout_range
3. after IOs:
- fscrypt_decrypt_bio_pages
- fscrypt_pullback_bio_page
- fscrypt_restore_control_page
Signed-off-by: Michael Halcrow <mhalcrow@xxxxxxxxxx>
Signed-off-by: Ildar Muslukhov <ildarm@xxxxxxxxxx>
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
---
fs/crypto/crypto.c | 507 +++++++++++++++++++++++++++++++++++++++++++++++
include/linux/fscrypto.h | 60 ++++++
2 files changed, 567 insertions(+)
create mode 100644 fs/crypto/crypto.c
diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c
new file mode 100644
index 0000000..928a34b
--- /dev/null
+++ b/fs/crypto/crypto.c
@@ -0,0 +1,507 @@
+/*
+ * 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/crypto.h>
+#include <linux/ecryptfs.h>
+#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/fscrypto.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 ablkcipher_request *req = NULL;
+ DECLARE_FS_COMPLETION_RESULT(ecr);
+ struct scatterlist dst, src;
+ struct fscrypt_info *ci = inode->i_crypt_info;
+ struct crypto_ablkcipher *tfm = ci->ci_ctfm;
+ int res = 0;
+
+ req = ablkcipher_request_alloc(tfm, 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,
+ fscrypt_complete, &ecr);
+
+ BUILD_BUG_ON(FS_XTS_TWEAK_SIZE < sizeof(index));
+ memcpy(xts_tweak, &inode->i_ino, 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);
+ ablkcipher_request_set_crypt(req, &src, &dst, PAGE_CACHE_SIZE,
+ xts_tweak);
+ if (rw == FS_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;
+}
+
+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);
+
+/*
+ * 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.
+ */
+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
+ */
+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");
diff --git a/include/linux/fscrypto.h b/include/linux/fscrypto.h
index 4d83f08..63211f9 100644
--- a/include/linux/fscrypto.h
+++ b/include/linux/fscrypto.h
@@ -236,4 +236,64 @@ static inline int fscrypt_has_encryption_key(struct inode *inode)
return 0;
#endif
}
+
+#if IS_ENABLED(CONFIG_FS_ENCRYPTION)
+/* crypto.c */
+extern struct kmem_cache *fscrypt_info_cachep;
+int fscrypt_initialize(void);
+
+extern struct fscrypt_ctx *fscrypt_get_ctx(struct inode *);
+extern void fscrypt_release_ctx(struct fscrypt_ctx *);
+extern struct page *fscrypt_encrypt_page(struct inode *, struct page *);
+extern int fscrypt_decrypt_page(struct page *);
+extern void fscrypt_decrypt_bio_pages(struct fscrypt_ctx *, struct bio *);
+extern void fscrypt_pullback_bio_page(struct page **, bool);
+extern void fscrypt_restore_control_page(struct page *);
+extern int fscrypt_zeroout_range(struct inode *, pgoff_t, sector_t,
+ unsigned int);
+#endif
+
+/* crypto.c */
+static inline struct fscrypt_ctx *fscrypt_notsupp_get_ctx(struct inode *i)
+{
+ return ERR_PTR(-EOPNOTSUPP);
+}
+
+static inline void fscrypt_notsupp_release_ctx(struct fscrypt_ctx *c)
+{
+ return;
+}
+
+static inline struct page *fscrypt_notsupp_encrypt_page(struct inode *i,
+ struct page *p)
+{
+ return ERR_PTR(-EOPNOTSUPP);
+}
+
+static inline int fscrypt_notsupp_decrypt_page(struct page *p)
+{
+ return -EOPNOTSUPP;
+}
+
+static inline void fscrypt_notsupp_decrypt_bio_pages(struct fscrypt_ctx *c,
+ struct bio *b)
+{
+ return;
+}
+
+static inline void fscrypt_notsupp_pullback_bio_page(struct page **p, bool b)
+{
+ return;
+}
+
+static inline void fscrypt_notsupp_restore_control_page(struct page *p)
+{
+ return;
+}
+
+static inline int fscrypt_notsupp_zeroout_range(struct inode *i, pgoff_t p,
+ sector_t s, unsigned int f)
+{
+ return -EOPNOTSUPP;
+}
#endif /* _LINUX_FSCRYPTO_H */
--
2.6.3
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