From 764355487ea220fdc2faf128d577d7f679b91f97 Mon Sep 17 00:00:00 2001 From: John Johansen Date: Fri, 22 Jul 2011 08:14:15 -0700 Subject: [PATCH] Ecryptfs: Add mount option to check uid of device being mounted = expect uid 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. Signed-off-by: John Johansen Cc: Signed-off-by: Tyler Hicks --- fs/ecryptfs/main.c | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-) diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c index 9f1bb747d77d..b4a6befb1216 100644 --- a/fs/ecryptfs/main.c +++ b/fs/ecryptfs/main.c @@ -175,6 +175,7 @@ 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 = { @@ -191,6 +192,7 @@ 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} }; @@ -236,6 +238,7 @@ static void ecryptfs_init_mount_crypt_stat( * ecryptfs_parse_options * @sb: The ecryptfs super block * @options: The options passed 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 @@ -251,7 +254,8 @@ 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; @@ -276,6 +280,8 @@ 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; @@ -380,6 +386,9 @@ 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 @@ -475,6 +484,7 @@ 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); @@ -483,7 +493,7 @@ 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; @@ -521,6 +531,15 @@ 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; -- 2.39.2