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| author | Daniel Rosenberg <drosen@google.com> | 2020-01-20 14:31:56 -0800 |
|---|---|---|
| committer | Eric Biggers <ebiggers@google.com> | 2020-01-22 14:47:15 -0800 |
| commit | 6e1918cfb263acacd3fc9239127732b69de64695 (patch) | |
| tree | f568fcd5fbed7df8ff441c664f18be933593ebd7 /fs/crypto/hooks.c | |
| parent | 1b3b827ee5230a73c8ed1b2cd8d53b4bd001268b (diff) | |
| download | linux-6e1918cfb263acacd3fc9239127732b69de64695.tar.bz2 | |
fscrypt: don't allow v1 policies with casefolding
Casefolded encrypted directories will use a new dirhash method that
requires a secret key. If the directory uses a v2 encryption policy,
it's easy to derive this key from the master key using HKDF. However,
v1 encryption policies don't provide a way to derive additional keys.
Therefore, don't allow casefolding on directories that use a v1 policy.
Specifically, make it so that trying to enable casefolding on a
directory that has a v1 policy fails, trying to set a v1 policy on a
casefolded directory fails, and trying to open a casefolded directory
that has a v1 policy (if one somehow exists on-disk) fails.
Signed-off-by: Daniel Rosenberg <drosen@google.com>
[EB: improved commit message, updated fscrypt.rst, and other cleanups]
Link: https://lore.kernel.org/r/20200120223201.241390-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Diffstat (limited to 'fs/crypto/hooks.c')
| -rw-r--r-- | fs/crypto/hooks.c | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/fs/crypto/hooks.c b/fs/crypto/hooks.c index 4081aae4bc35..fd4e5ae21077 100644 --- a/fs/crypto/hooks.c +++ b/fs/crypto/hooks.c @@ -122,6 +122,34 @@ int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry, } EXPORT_SYMBOL_GPL(__fscrypt_prepare_lookup); +/** + * fscrypt_prepare_setflags() - prepare to change flags with FS_IOC_SETFLAGS + * @inode: the inode on which flags are being changed + * @oldflags: the old flags + * @flags: the new flags + * + * The caller should be holding i_rwsem for write. + * + * Return: 0 on success; -errno if the flags change isn't allowed or if + * another error occurs. + */ +int fscrypt_prepare_setflags(struct inode *inode, + unsigned int oldflags, unsigned int flags) +{ + struct fscrypt_info *ci; + int err; + + if (IS_ENCRYPTED(inode) && (flags & ~oldflags & FS_CASEFOLD_FL)) { + err = fscrypt_require_key(inode); + if (err) + return err; + ci = inode->i_crypt_info; + if (ci->ci_policy.version != FSCRYPT_POLICY_V2) + return -EINVAL; + } + return 0; +} + int __fscrypt_prepare_symlink(struct inode *dir, unsigned int len, unsigned int max_len, struct fscrypt_str *disk_link) |