[apparmor] [PATCH 1/4] security: add security_path_chdir hook

[Seth Arnold]

On Tue, Nov 05, 2013 at 05:34:58AM -0800, John Johansen wrote:
> Signed-off-by: John Johansen <john.johansen at canonical.com>

Both nfs_permission() and fuse_permission() use MAY_CHDIR without an
obvious security hook nearby. (The chroot() syscall does have a nearby
security_path_chroot() call.) Should this patch add security_path_chdir()
calls to these locations?

I believe this is correct as written, but I thought I'd ask for
confirmation.

Thanks

> ---
>  fs/open.c                |  8 ++++++++
>  include/linux/security.h | 11 +++++++++++
>  security/security.c      |  7 +++++++
>  3 files changed, 26 insertions(+)
> 
> diff --git a/fs/open.c b/fs/open.c
> index d420331..9505fc5 100644
> --- a/fs/open.c
> +++ b/fs/open.c
> @@ -387,6 +387,10 @@ retry:
>  	if (error)
>  		goto out;
>  
> +	error = security_path_chdir(&path);
> +	if (error)
> +		goto dput_and_out;
> +
>  	error = inode_permission(path.dentry->d_inode, MAY_EXEC | MAY_CHDIR);
>  	if (error)
>  		goto dput_and_out;
> @@ -419,6 +423,10 @@ SYSCALL_DEFINE1(fchdir, unsigned int, fd)
>  	if (!S_ISDIR(inode->i_mode))
>  		goto out_putf;
>  
> +	error = security_path_chdir(&f.file->f_path);
> +	if (error)
> +		goto out_putf;
> +
>  	error = inode_permission(inode, MAY_EXEC | MAY_CHDIR);
>  	if (!error)
>  		set_fs_pwd(current->fs, &f.file->f_path);
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 9d37e2b..ed693ff 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -466,6 +466,10 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
>   *	@uid contains new owner's ID.
>   *	@gid contains new group's ID.
>   *	Return 0 if permission is granted.
> + * @path_chdir:
> + *	Check for permission to change working directory to @path.
> + *	@path contains the path structure.
> + *	Return 0 if permission is granted.
>   * @path_chroot:
>   *	Check for permission to change root directory.
>   *	@path contains the path structure.
> @@ -1486,6 +1490,7 @@ struct security_operations {
>  			    struct path *new_dir, struct dentry *new_dentry);
>  	int (*path_chmod) (struct path *path, umode_t mode);
>  	int (*path_chown) (struct path *path, kuid_t uid, kgid_t gid);
> +	int (*path_chdir) (struct path *path);
>  	int (*path_chroot) (struct path *path);
>  #endif
>  
> @@ -2944,6 +2949,7 @@ int security_path_rename(struct path *old_dir, struct dentry *old_dentry,
>  			 struct path *new_dir, struct dentry *new_dentry);
>  int security_path_chmod(struct path *path, umode_t mode);
>  int security_path_chown(struct path *path, kuid_t uid, kgid_t gid);
> +int security_path_chdir(struct path *path);
>  int security_path_chroot(struct path *path);
>  #else	/* CONFIG_SECURITY_PATH */
>  static inline int security_path_unlink(struct path *dir, struct dentry *dentry)
> @@ -3004,6 +3010,11 @@ static inline int security_path_chown(struct path *path, kuid_t uid, kgid_t gid)
>  	return 0;
>  }
>  
> +static inline int security_path_chdir(struct path *path)
> +{
> +	return 0;
> +}
> +
>  static inline int security_path_chroot(struct path *path)
>  {
>  	return 0;
> diff --git a/security/security.c b/security/security.c
> index 4dc31f4..ca57c35 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -464,6 +464,13 @@ int security_path_chown(struct path *path, kuid_t uid, kgid_t gid)
>  	return security_ops->path_chown(path, uid, gid);
>  }
>  
> +int security_path_chdir(struct path *path)
> +{
> +	if (unlikely(IS_PRIVATE(path->dentry->d_inode)))
> +		return 0;
> +	return security_ops->path_chdir(path);
> +}
> +
>  int security_path_chroot(struct path *path)
>  {
>  	return security_ops->path_chroot(path);
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