kernel/git/stable/linux-stable.git/fs/crypto, branch linux-4.10.y

fscrypt: fix context consistency check when key(s) unavailable

2017-05-20T12:31:03+00:00

commit 272f98f6846277378e1758a49a49d7bf39343c02 upstream. To mitigate some types of offline attacks, filesystem encryption is designed to enforce that all files in an encrypted directory tree use the same encryption policy (i.e. the same encryption context excluding the nonce). However, the fscrypt_has_permitted_context() function which enforces this relies on comparing struct fscrypt_info's, which are only available when we have the encryption keys. This can cause two incorrect behaviors: 1. If we have the parent directory's key but not the child's key, or vice versa, then fscrypt_has_permitted_context() returned false, causing applications to see EPERM or ENOKEY. This is incorrect if the encryption contexts are in fact consistent. Although we'd normally have either both keys or neither key in that case since the master_key_descriptors would be the same, this is not guaranteed because keys can be added or removed from keyrings at any time. 2. If we have neither the parent's key nor the child's key, then fscrypt_has_permitted_context() returned true, causing applications to see no error (or else an error for some other reason). This is incorrect if the encryption contexts are in fact inconsistent, since in that case we should deny access. To fix this, retrieve and compare the fscrypt_contexts if we are unable to set up both fscrypt_infos. While this slightly hurts performance when accessing an encrypted directory tree without the key, this isn't a case we really need to be optimizing for; access *with* the key is much more important. Furthermore, the performance hit is barely noticeable given that we are already retrieving the fscrypt_context and doing two keyring searches in fscrypt_get_encryption_info(). If we ever actually wanted to optimize this case we might start by caching the fscrypt_contexts. Signed-off-by: Eric Biggers Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman

fscrypt: remove broken support for detecting keyring key revocation

2017-03-30T07:44:07+00:00

commit 1b53cf9815bb4744958d41f3795d5d5a1d365e2d upstream. Filesystem encryption ostensibly supported revoking a keyring key that had been used to "unlock" encrypted files, causing those files to become "locked" again. This was, however, buggy for several reasons, the most severe of which was that when key revocation happened to be detected for an inode, its fscrypt_info was immediately freed, even while other threads could be using it for encryption or decryption concurrently. This could be exploited to crash the kernel or worse. This patch fixes the use-after-free by removing the code which detects the keyring key having been revoked, invalidated, or expired. Instead, an encrypted inode that is "unlocked" now simply remains unlocked until it is evicted from memory. Note that this is no worse than the case for block device-level encryption, e.g. dm-crypt, and it still remains possible for a privileged user to evict unused pages, inodes, and dentries by running 'sync; echo 3 > /proc/sys/vm/drop_caches', or by simply unmounting the filesystem. In fact, one of those actions was already needed anyway for key revocation to work even somewhat sanely. This change is not expected to break any applications. In the future I'd like to implement a real API for fscrypt key revocation that interacts sanely with ongoing filesystem operations --- waiting for existing operations to complete and blocking new operations, and invalidating and sanitizing key material and plaintext from the VFS caches. But this is a hard problem, and for now this bug must be fixed. This bug affected almost all versions of ext4, f2fs, and ubifs encryption, and it was potentially reachable in any kernel configured with encryption support (CONFIG_EXT4_ENCRYPTION=y, CONFIG_EXT4_FS_ENCRYPTION=y, CONFIG_F2FS_FS_ENCRYPTION=y, or CONFIG_UBIFS_FS_ENCRYPTION=y). Note that older kernels did not use the shared fs/crypto/ code, but due to the potential security implications of this bug, it may still be worthwhile to backport this fix to them. Fixes: b7236e21d55f ("ext4 crypto: reorganize how we store keys in the inode") Signed-off-by: Eric Biggers Signed-off-by: Theodore Ts'o Acked-by: Michael Halcrow Signed-off-by: Greg Kroah-Hartman

fscrypt: fix renaming and linking special files

2016-12-31T05:47:05+00:00

Attempting to link a device node, named pipe, or socket file into an encrypted directory through rename(2) or link(2) always failed with EPERM. This happened because fscrypt_has_permitted_context() saw that the file was unencrypted and forbid creating the link. This behavior was unexpected because such files are never encrypted; only regular files, directories, and symlinks can be encrypted. To fix this, make fscrypt_has_permitted_context() always return true on special files. This will be covered by a test in my encryption xfstests patchset. Fixes: 9bd8212f981e ("ext4 crypto: add encryption policy and password salt support") Signed-off-by: Eric Biggers Reviewed-by: Richard Weinberger Cc: stable@vger.kernel.org Signed-off-by: Theodore Ts'o

fscrypt: fix the test_dummy_encryption mount option

2016-12-28T00:46:27+00:00

Commit f1c131b45410a: "crypto: xts - Convert to skcipher" now fails the setkey operation if the AES key is the same as the tweak key. Previously this check was only done if FIPS mode is enabled. Now this check is also done if weak key checking was requested. This is reasonable, but since we were using the dummy key which was a constant series of 0x42 bytes, it now caused dummy encrpyption test mode to fail. Fix this by using 0x42... and 0x24... for the two keys, so they are different. Fixes: f1c131b45410a202eb45cc55980a7a9e4e4b4f40 Cc: stable@vger.kernel.org Signed-off-by: Theodore Ts'o

fscrypt: Rename FS_WRITE_PATH_FL to FS_CTX_HAS_BOUNCE_BUFFER_FL

2016-12-11T21:33:18+00:00

... to better explain its purpose after introducing in-place encryption without bounce buffer. Signed-off-by: David Gstir Signed-off-by: Theodore Ts'o

fscrypt: Delay bounce page pool allocation until needed

2016-12-11T21:33:11+00:00

Since fscrypt users can now indicated if fscrypt_encrypt_page() should use a bounce page, we can delay the bounce page pool initialization util it is really needed. That is until fscrypt_operations has no FS_CFLG_OWN_PAGES flag set. Signed-off-by: David Gstir Signed-off-by: Theodore Ts'o

fscrypt: Cleanup page locking requirements for fscrypt_{decrypt,encrypt}_page()

2016-12-11T21:26:12+00:00

Rename the FS_CFLG_INPLACE_ENCRYPTION flag to FS_CFLG_OWN_PAGES which, when set, indicates that the fs uses pages under its own control as opposed to writeback pages which require locking and a bounce buffer for encryption. Signed-off-by: David Gstir Signed-off-by: Theodore Ts'o

fscrypt: Cleanup fscrypt_{decrypt,encrypt}_page()

2016-12-11T21:26:12+00:00

- Improve documentation - Add BUG_ON(len == 0) to avoid accidental switch of offs and len parameters - Improve variable names for readability Signed-off-by: David Gstir Signed-off-by: Theodore Ts'o

fscrypt: Never allocate fscrypt_ctx on in-place encryption

2016-12-11T21:26:11+00:00

In case of in-place encryption fscrypt_ctx was allocated but never released. Since we don't need it for in-place encryption, we skip allocating it. Fixes: 1c7dcf69eea3 ("fscrypt: Add in-place encryption mode") Signed-off-by: David Gstir Signed-off-by: Theodore Ts'o

fscrypt: Use correct index in decrypt path.

2016-12-11T21:26:10+00:00

Actually use the fs-provided index instead of always using page->index which is only set for page-cache pages. Fixes: 9c4bb8a3a9b4 ("fscrypt: Let fs select encryption index/tweak") Signed-off-by: David Gstir Signed-off-by: Theodore Ts'o