summaryrefslogtreecommitdiffstats
path: root/fs/crypto/Kconfig
AgeCommit message (Collapse)AuthorFilesLines
2019-08-12fscrypt: add an HKDF-SHA512 implementationEric Biggers1-0/+2
Add an implementation of HKDF (RFC 5869) to fscrypt, for the purpose of deriving additional key material from the fscrypt master keys for v2 encryption policies. HKDF is a key derivation function built on top of HMAC. We choose SHA-512 for the underlying unkeyed hash, and use an "hmac(sha512)" transform allocated from the crypto API. We'll be using this to replace the AES-ECB based KDF currently used to derive the per-file encryption keys. While the AES-ECB based KDF is believed to meet the original security requirements, it is nonstandard and has problems that don't exist in modern KDFs such as HKDF: 1. It's reversible. Given a derived key and nonce, an attacker can easily compute the master key. This is okay if the master key and derived keys are equally hard to compromise, but now we'd like to be more robust against threats such as a derived key being compromised through a timing attack, or a derived key for an in-use file being compromised after the master key has already been removed. 2. It doesn't evenly distribute the entropy from the master key; each 16 input bytes only affects the corresponding 16 output bytes. 3. It isn't easily extensible to deriving other values or keys, such as a public hash for securely identifying the key, or per-mode keys. Per-mode keys will be immediately useful for Adiantum encryption, for which fscrypt currently uses the master key directly, introducing unnecessary usage constraints. Per-mode keys will also be useful for hardware inline encryption, which is currently being worked on. HKDF solves all the above problems. Reviewed-by: Paul Crowley <paulcrowley@google.com> Reviewed-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Eric Biggers <ebiggers@google.com>
2019-06-27fscrypt: remove selection of CONFIG_CRYPTO_SHA256Eric Biggers1-1/+0
fscrypt only uses SHA-256 for AES-128-CBC-ESSIV, which isn't the default and is only recommended on platforms that have hardware accelerated AES-CBC but not AES-XTS. There's no link-time dependency, since SHA-256 is requested via the crypto API on first use. To reduce bloat, we should limit FS_ENCRYPTION to selecting the default algorithms only. SHA-256 by itself isn't that much bloat, but it's being discussed to move ESSIV into a crypto API template, which would incidentally bring in other things like "authenc" support, which would all end up being built-in since FS_ENCRYPTION is now a bool. For Adiantum encryption we already just document that users who want to use it have to enable CONFIG_CRYPTO_ADIANTUM themselves. So, let's do the same for AES-128-CBC-ESSIV and CONFIG_CRYPTO_SHA256. Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Reviewed-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Eric Biggers <ebiggers@google.com>
2019-05-21treewide: Add SPDX license identifier - Makefile/KconfigThomas Gleixner1-0/+1
Add SPDX license identifiers to all Make/Kconfig files which: - Have no license information of any form These files fall under the project license, GPL v2 only. The resulting SPDX license identifier is: GPL-2.0-only Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-01-23fscrypt: remove filesystem specific build config optionChandan Rajendra1-2/+3
In order to have a common code base for fscrypt "post read" processing for all filesystems which support encryption, this commit removes filesystem specific build config option (e.g. CONFIG_EXT4_FS_ENCRYPTION) and replaces it with a build option (i.e. CONFIG_FS_ENCRYPTION) whose value affects all the filesystems making use of fscrypt. Reviewed-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com> Signed-off-by: Eric Biggers <ebiggers@google.com>
2019-01-23fscrypt: remove CRYPTO_CTR dependencyEric Biggers1-1/+0
fscrypt doesn't use the CTR mode of operation for anything, so there's no need to select CRYPTO_CTR. It was added by commit 71dea01ea2ed ("ext4 crypto: require CONFIG_CRYPTO_CTR if ext4 encryption is enabled"). But, I've been unable to identify the arm64 crypto bug it was supposedly working around. I suspect the issue was seen only on some old Android device kernel (circa 3.10?). So if the fix wasn't mistaken, the real bug is probably already fixed. Or maybe it was actually a bug in a non-upstream crypto driver. So, remove the dependency. If it turns out there's actually still a bug, we'll fix it properly. Signed-off-by: Eric Biggers <ebiggers@google.com>
2017-06-23fscrypt: add support for AES-128-CBCDaniel Walter1-0/+1
fscrypt provides facilities to use different encryption algorithms which are selectable by userspace when setting the encryption policy. Currently, only AES-256-XTS for file contents and AES-256-CBC-CTS for file names are implemented. This is a clear case of kernel offers the mechanism and userspace selects a policy. Similar to what dm-crypt and ecryptfs have. This patch adds support for using AES-128-CBC for file contents and AES-128-CBC-CTS for file name encryption. To mitigate watermarking attacks, IVs are generated using the ESSIV algorithm. While AES-CBC is actually slightly less secure than AES-XTS from a security point of view, there is more widespread hardware support. Using AES-CBC gives us the acceptable performance while still providing a moderate level of security for persistent storage. Especially low-powered embedded devices with crypto accelerators such as CAAM or CESA often only support AES-CBC. Since using AES-CBC over AES-XTS is basically thought of a last resort, we use AES-128-CBC over AES-256-CBC since it has less encryption rounds and yields noticeable better performance starting from a file size of just a few kB. Signed-off-by: Daniel Walter <dwalter@sigma-star.at> [david@sigma-star.at: addressed review comments] Signed-off-by: David Gstir <david@sigma-star.at> Reviewed-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2017-01-01fscrypt: factor out bio specific functionsRichard Weinberger1-1/+0
That way we can get rid of the direct dependency on CONFIG_BLOCK. Fixes: d475a507457b ("ubifs: Add skeleton for fscrypto") Reported-by: Arnd Bergmann <arnd@arndb.de> Reported-by: Randy Dunlap <rdunlap@infradead.org> Reviewed-by: Eric Biggers <ebiggers@google.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: David Gstir <david@sigma-star.at> Signed-off-by: Richard Weinberger <richard@nod.at> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2016-12-11fscrypto: remove unneeded Kconfig dependenciesEric Biggers1-2/+0
SHA256 and ENCRYPTED_KEYS are not needed. CTR shouldn't be needed either, but I left it for now because it was intentionally added by commit 71dea01ea2ed ("ext4 crypto: require CONFIG_CRYPTO_CTR if ext4 encryption is enabled"). So it sounds like there may be a dependency problem elsewhere, which I have not been able to identify specifically, that must be solved before CTR can be removed. Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2016-03-17fs crypto: move per-file encryption from f2fs tree to fs/cryptoJaegeuk Kim1-0/+18
This patch adds the renamed functions moved from the f2fs crypto files. 1. definitions for per-file encryption used by ext4 and f2fs. 2. crypto.c for encrypt/decrypt functions a. IO preparation: - fscrypt_get_ctx / fscrypt_release_ctx b. before IOs: - fscrypt_encrypt_page - fscrypt_decrypt_page - fscrypt_zeroout_range c. after IOs: - fscrypt_decrypt_bio_pages - fscrypt_pullback_bio_page - fscrypt_restore_control_page 3. policy.c supporting context management. a. For ioctls: - fscrypt_process_policy - fscrypt_get_policy b. For context permission - fscrypt_has_permitted_context - fscrypt_inherit_context 4. keyinfo.c to handle permissions - fscrypt_get_encryption_info - fscrypt_free_encryption_info 5. fname.c to support filename encryption a. general wrapper functions - fscrypt_fname_disk_to_usr - fscrypt_fname_usr_to_disk - fscrypt_setup_filename - fscrypt_free_filename b. specific filename handling functions - fscrypt_fname_alloc_buffer - fscrypt_fname_free_buffer 6. Makefile and Kconfig Cc: Al Viro <viro@ftp.linux.org.uk> Signed-off-by: Michael Halcrow <mhalcrow@google.com> Signed-off-by: Ildar Muslukhov <ildarm@google.com> Signed-off-by: Uday Savagaonkar <savagaon@google.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>