From patchwork Thu Aug 11 07:44:56 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [1/2, natty, CVE, 1/2] Add mount option to check uid of device being mounted = expect uid Date: Wed, 10 Aug 2011 21:44:56 -0000 From: John Johansen X-Patchwork-Id: 109562 Message-Id: <1313048697-23240-1-git-send-email-john.johansen@canonical.com> To: kernel-team@lists.ubuntu.com Close a TOCTOU race for mounts done via ecryptfs-mount-private. The mount source (device) can be raced when the ownership test is done in userspace. Provide Ecryptfs a means to force the uid check at mount time. (cherry picked from commit 764355487ea220fdc2faf128d577d7f679b91f97 git://git.kernel.org/pub/scm/linux/kernel/git/ecryptfs/ecryptfs-2.6.git for-linus) CVE-2011-1833 BugLink: http://bugs.launchpad.net/bugs/732628 Signed-off-by: John Johansen --- fs/ecryptfs/main.c | 23 +++++++++++++++++++++-- 1 files changed, 21 insertions(+), 2 deletions(-) diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c index 758323a..adc54c2 100644 --- a/fs/ecryptfs/main.c +++ b/fs/ecryptfs/main.c @@ -218,6 +218,7 @@ enum { ecryptfs_opt_sig, ecryptfs_opt_ecryptfs_sig, ecryptfs_opt_encrypted_view, ecryptfs_opt_fnek_sig, ecryptfs_opt_fn_cipher, ecryptfs_opt_fn_cipher_key_bytes, ecryptfs_opt_unlink_sigs, ecryptfs_opt_mount_auth_tok_only, + ecryptfs_opt_check_dev_ruid, ecryptfs_opt_err }; static const match_table_t tokens = { @@ -234,6 +235,7 @@ static const match_table_t tokens = { {ecryptfs_opt_fn_cipher_key_bytes, "ecryptfs_fn_key_bytes=%u"}, {ecryptfs_opt_unlink_sigs, "ecryptfs_unlink_sigs"}, {ecryptfs_opt_mount_auth_tok_only, "ecryptfs_mount_auth_tok_only"}, + {ecryptfs_opt_check_dev_ruid, "ecryptfs_check_dev_ruid"}, {ecryptfs_opt_err, NULL} }; @@ -277,6 +279,7 @@ static void ecryptfs_init_mount_crypt_stat( * ecryptfs_parse_options * @sb: The ecryptfs super block * @options: The options pased to the kernel + * @check_ruid: set to 1 if device uid should be checked against the ruid * * Parse mount options: * debug=N - ecryptfs_verbosity level for debug output @@ -292,7 +295,8 @@ static void ecryptfs_init_mount_crypt_stat( * * Returns zero on success; non-zero on error */ -static int ecryptfs_parse_options(struct ecryptfs_sb_info *sbi, char *options) +static int ecryptfs_parse_options(struct ecryptfs_sb_info *sbi, char *options, + uid_t *check_ruid) { char *p; int rc = 0; @@ -317,6 +321,8 @@ static int ecryptfs_parse_options(struct ecryptfs_sb_info *sbi, char *options) char *cipher_key_bytes_src; char *fn_cipher_key_bytes_src; + *check_ruid = 0; + if (!options) { rc = -EINVAL; goto out; @@ -421,6 +427,9 @@ static int ecryptfs_parse_options(struct ecryptfs_sb_info *sbi, char *options) mount_crypt_stat->flags |= ECRYPTFS_GLOBAL_MOUNT_AUTH_TOK_ONLY; break; + case ecryptfs_opt_check_dev_ruid: + *check_ruid = 1; + break; case ecryptfs_opt_err: default: printk(KERN_WARNING @@ -516,6 +525,7 @@ static struct dentry *ecryptfs_mount(struct file_system_type *fs_type, int flags const char *err = "Getting sb failed"; struct inode *inode; struct path path; + uid_t check_ruid; int rc; sbi = kmem_cache_zalloc(ecryptfs_sb_info_cache, GFP_KERNEL); @@ -524,7 +534,7 @@ static struct dentry *ecryptfs_mount(struct file_system_type *fs_type, int flags goto out; } - rc = ecryptfs_parse_options(sbi, raw_data); + rc = ecryptfs_parse_options(sbi, raw_data, &check_ruid); if (rc) { err = "Error parsing options"; goto out; @@ -562,6 +572,15 @@ static struct dentry *ecryptfs_mount(struct file_system_type *fs_type, int flags "known incompatibilities\n"); goto out_free; } + + if (check_ruid && path.dentry->d_inode->i_uid != current_uid()) { + rc = -EPERM; + printk(KERN_ERR "Mount of device (uid: %d) not owned by " + "requested user (uid: %d)\n", + path.dentry->d_inode->i_uid, current_uid()); + goto out_free; + } + ecryptfs_set_superblock_lower(s, path.dentry->d_sb); s->s_maxbytes = path.dentry->d_sb->s_maxbytes; s->s_blocksize = path.dentry->d_sb->s_blocksize;