APPLIED: [PATCH] Lucid CVE-2011-1833

[Tim Gardner]

On 08/11/2011 01:51 PM, John Johansen wrote:
> On 08/11/2011 12:41 PM, Tim Gardner wrote:
>> From bb684cd8022bd9a6a5eb5fda9d61009df80e11d0 Mon Sep 17 00:00:00 2001
>> From: Tim Gardner<tim.gardner at canonical.com>
>> 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<john.johansen at canonical.com>
>> Signed-off-by: Tim Gardner<tim.gardner at canonical.com>
>
> yep, I am good with the change of passing check_ruid down into
> ecryptfs_read_super
>
> Acked-by: John Johansen <john.johansen at canonical.com>
>
>
>> ---
>> 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
>


-- 
Tim Gardner tim.gardner at canonical.com