From: Eric Biggers <ebiggers3@gmail.com>
To: Theodore Ts'o <tytso@mit.edu>
Cc: Ext4 Developers List <linux-ext4@vger.kernel.org>,
Linux Filesystem Development List <linux-fsdevel@vger.kernel.org>,
jaegeuk@kernel.org, richard@nod.at, ebiggers@google.com
Subject: Re: [PATCH] ext4: don't allow encrypted operations without keys
Date: Thu, 5 Jan 2017 11:26:19 -0800 [thread overview]
Message-ID: <20170105192619.GF21696@gmail.com> (raw)
In-Reply-To: <20161228052252.10314-1-tytso@mit.edu>
Hi Ted,
On Wed, Dec 28, 2016 at 12:22:52AM -0500, Theodore Ts'o wrote:
> While we allow deletes without the key, the following should not be
> permitted:
>
> # cd /vdc/encrypted-dir-without-key
> # ls -l
> total 4
> -rw-r--r-- 1 root root 0 Dec 27 22:35 6,LKNRJsp209FbXoSvJWzB
> -rw-r--r-- 1 root root 286 Dec 27 22:35 uRJ5vJh9gE7vcomYMqTAyD
> # mv uRJ5vJh9gE7vcomYMqTAyD 6,LKNRJsp209FbXoSvJWzB
>
> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
> ---
> fs/ext4/namei.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
> index eadba919f26b..45a5ba558074 100644
> --- a/fs/ext4/namei.c
> +++ b/fs/ext4/namei.c
> @@ -3525,6 +3525,12 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
> EXT4_I(old_dentry->d_inode)->i_projid)))
> return -EXDEV;
>
> + if ((ext4_encrypted_inode(old_dir) &&
> + !fscrypt_has_encryption_key(old_dir)) ||
> + (ext4_encrypted_inode(new_dir) &&
> + !fscrypt_has_encryption_key(new_dir)))
> + return -ENOKEY;
> +
> retval = dquot_initialize(old.dir);
> if (retval)
> return retval;
> @@ -3725,6 +3731,12 @@ static int ext4_cross_rename(struct inode *old_dir, struct dentry *old_dentry,
> int retval;
> struct timespec ctime;
>
> + if ((ext4_encrypted_inode(old_dir) &&
> + !fscrypt_has_encryption_key(old_dir)) ||
> + (ext4_encrypted_inode(new_dir) &&
> + !fscrypt_has_encryption_key(new_dir)))
> + return -ENOKEY;
> +
> if ((ext4_encrypted_inode(old_dir) ||
> ext4_encrypted_inode(new_dir)) &&
> (old_dir != new_dir) &&
I'm fine with this, with the understanding that it relies on ext4_lookup()
calling fscrypt_get_encryption_info() (via fscrypt_has_permitted_context()) when
looking up the directory. I also suggest moving the fscrypt_permitted_context()
check in ext4_rename() up to be next to the new check, so that the fscrypt hooks
are grouped together and are consistent with ext4_cross_rename().
I can also write/update an xfstest to test this.
Something I'm thinking about is making things easier for filesystems by having
functions like "fscrypt_rename_hook()" which would handle all these needed
checks. It would be easy to do with out-of-line functions in fs/crypto/, but we
don't want to be making ->is_encrypted() calls through the fscrypt_operations
all the time, when an inlined call to ext4_encrypted_inode() (or f2fs or
ubifs_encrypted_inode()) is much faster. I think it could be implemented as
efficiently as now if the hooks were defined in a header and called a macro like
"fs_encrypted_inode()" which filesystems would have to #define first. It would
be a little ugly, but at least it would be less error-prone than having multiple
filesystems replicate these increasingly complex checks.
Eric
next prev parent reply other threads:[~2017-01-05 19:26 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-19 22:20 [PATCH v2 1/5] fscrypt: fix loophole in one-encryption-policy-per-tree enforcement Eric Biggers
2016-12-19 22:20 ` [PATCH v2 2/5] fscrypt: fix renaming and linking special files Eric Biggers
2016-12-31 5:49 ` Theodore Ts'o
2016-12-19 22:20 ` [PATCH v2 3/5] ext4: consolidate fscrypt_has_permitted_context() checks Eric Biggers
2016-12-28 5:41 ` Theodore Ts'o
2017-01-05 19:03 ` Eric Biggers
2016-12-19 22:20 ` [PATCH v2 4/5] f2fs: " Eric Biggers
2016-12-19 22:20 ` [PATCH v2 5/5] ubifs: " Eric Biggers
2016-12-28 3:48 ` [PATCH v2 1/5] fscrypt: fix loophole in one-encryption-policy-per-tree enforcement Theodore Ts'o
2016-12-28 5:22 ` [PATCH] ext4: don't allow encrypted operations without keys Theodore Ts'o
2017-01-05 19:26 ` Eric Biggers [this message]
2017-01-05 20:15 ` Theodore Ts'o
2017-02-04 21:44 ` Eric Biggers
2017-02-06 1:13 ` Theodore Ts'o
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