From patchwork Thu Aug 11 19:18:44 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [1/2, maverick, CVE, 1/2] Add mount option to check uid of device being mounted = expect uid Date: Thu, 11 Aug 2011 09:18:44 -0000 From: Tim Gardner X-Patchwork-Id: 109665 Message-Id: <4E442B14.5000401@canonical.com> To: John Johansen Cc: Andy Whitcroft , kernel-team@lists.ubuntu.com How about this? Acked-by: John Johansen >From 5a90787578603c7207dfc1be2dad5f09780bbae8 Mon Sep 17 00:00:00 2001 From: John Johansen Date: Thu, 11 Aug 2011 00:48:00 -0700 Subject: [PATCH] Add mount option to check uid of device being mounted = expect uid, CVE-2011-1833 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. (backported from commit 764355487ea220fdc2faf128d577d7f679b91f97) CVE-2011-1833 BugLink: http://bugs.launchpad.net/bugs/732628 Signed-off-by: John Johansen Signed-off-by: Tim Gardner --- fs/ecryptfs/main.c | 29 ++++++++++++++++++++++++----- 1 files changed, 24 insertions(+), 5 deletions(-) diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c index cbd4e18..d5581f6 100644 --- a/fs/ecryptfs/main.c +++ b/fs/ecryptfs/main.c @@ -208,7 +208,8 @@ enum { ecryptfs_opt_sig, ecryptfs_opt_ecryptfs_sig, ecryptfs_opt_passthrough, ecryptfs_opt_xattr_metadata, ecryptfs_opt_encrypted_view, ecryptfs_opt_fnek_sig, ecryptfs_opt_fn_cipher, ecryptfs_opt_fn_cipher_key_bytes, - ecryptfs_opt_unlink_sigs, ecryptfs_opt_err }; + ecryptfs_opt_unlink_sigs, ecryptfs_opt_check_dev_ruid, + ecryptfs_opt_err }; static const match_table_t tokens = { {ecryptfs_opt_sig, "sig=%s"}, @@ -223,6 +224,7 @@ static const match_table_t tokens = { {ecryptfs_opt_fn_cipher, "ecryptfs_fn_cipher=%s"}, {ecryptfs_opt_fn_cipher_key_bytes, "ecryptfs_fn_key_bytes=%u"}, {ecryptfs_opt_unlink_sigs, "ecryptfs_unlink_sigs"}, + {ecryptfs_opt_check_dev_ruid, "ecryptfs_check_dev_ruid"}, {ecryptfs_opt_err, NULL} }; @@ -266,6 +268,7 @@ 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 @@ -281,7 +284,8 @@ 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; @@ -306,6 +310,8 @@ 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; @@ -406,6 +412,9 @@ static int ecryptfs_parse_options(struct ecryptfs_sb_info *sbi, char *options) case ecryptfs_opt_unlink_sigs: mount_crypt_stat->flags |= ECRYPTFS_UNLINK_SIGS; break; + case ecryptfs_opt_check_dev_ruid: + *check_ruid = 1; + break; case ecryptfs_opt_err: default: printk(KERN_WARNING @@ -494,7 +503,7 @@ static struct file_system_type ecryptfs_fs_type; * ecryptfs_interpose to create our initial inode and super block * struct. */ -static int ecryptfs_read_super(struct super_block *sb, const char *dev_name) +static int ecryptfs_read_super(struct super_block *sb, const char *dev_name, uid_t check_ruid) { struct path path; int rc; @@ -511,6 +520,15 @@ static int ecryptfs_read_super(struct super_block *sb, const char *dev_name) "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(sb, path.dentry->d_sb); sb->s_maxbytes = path.dentry->d_sb->s_maxbytes; sb->s_blocksize = path.dentry->d_sb->s_blocksize; @@ -549,6 +567,7 @@ static int ecryptfs_get_sb(struct file_system_type *fs_type, int flags, struct ecryptfs_dentry_info *root_info; const char *err = "Getting sb failed"; int rc; + uid_t check_ruid; sbi = kmem_cache_zalloc(ecryptfs_sb_info_cache, GFP_KERNEL); if (!sbi) { @@ -556,7 +575,7 @@ static int ecryptfs_get_sb(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; @@ -601,7 +620,7 @@ static int ecryptfs_get_sb(struct file_system_type *fs_type, int flags, /* ->kill_sb() will take care of root_info */ ecryptfs_set_dentry_private(s->s_root, root_info); s->s_flags |= MS_ACTIVE; - rc = ecryptfs_read_super(s, dev_name); + rc = ecryptfs_read_super(s, dev_name, check_ruid); if (rc) { deactivate_locked_super(s); err = "Reading sb failed"; -- 1.7.0.4