From bb684cd8022bd9a6a5eb5fda9d61009df80e11d0 Mon Sep 17 00:00:00 2001 From: Tim Gardner Date: Thu, 11 Aug 2011 13:33:18 -0600 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 | 30 +++++++++++++++++++++++++----- 1 files changed, 25 insertions(+), 5 deletions(-) diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c index c6ac85d..f6cd392 100644 --- a/fs/ecryptfs/main.c +++ b/fs/ecryptfs/main.c @@ -212,7 +212,8 @@ 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"}, @@ -227,6 +228,7 @@ 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} }; @@ -270,6 +272,7 @@ 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 @@ -285,7 +288,8 @@ static void ecryptfs_init_mount_crypt_stat( * * Returns zero on success; non-zero on error */ -static int ecryptfs_parse_options(struct super_block *sb, char *options) +static int ecryptfs_parse_options(struct super_block *sb, char *options, + uid_t *check_ruid) { char *p; int rc = 0; @@ -310,6 +314,8 @@ static int ecryptfs_parse_options(struct super_block *sb, char *options) char *cipher_key_bytes_src; char *fn_cipher_key_bytes_src; + *check_ruid = 0; + if (!options) { rc = -EINVAL; goto out; @@ -410,6 +416,9 @@ static int ecryptfs_parse_options(struct super_block *sb, 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 @@ -551,7 +560,8 @@ out: * 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; @@ -561,6 +571,15 @@ static int ecryptfs_read_super(struct super_block *sb, const char *dev_name) ecryptfs_printk(KERN_WARNING, "path_lookup() failed\n"); goto out; } + + 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; @@ -599,6 +618,7 @@ static int ecryptfs_get_sb(struct file_system_type *fs_type, int flags, { int rc; struct super_block *sb; + uid_t check_ruid; rc = get_sb_nodev(fs_type, flags, raw_data, ecryptfs_fill_super, mnt); if (rc < 0) { @@ -606,12 +626,12 @@ static int ecryptfs_get_sb(struct file_system_type *fs_type, int flags, goto out; } sb = mnt->mnt_sb; - rc = ecryptfs_parse_options(sb, raw_data); + rc = ecryptfs_parse_options(sb, raw_data, &check_ruid); if (rc) { printk(KERN_ERR "Error parsing options; rc = [%d]\n", rc); goto out_abort; } - rc = ecryptfs_read_super(sb, dev_name); + rc = ecryptfs_read_super(sb, dev_name, check_ruid); if (rc) { printk(KERN_ERR "Reading sb failed; rc = [%d]\n", rc); goto out_abort; -- 1.7.0.4