chroot(2) [osx man page]

CHROOT(2)						      BSD System Calls Manual							 CHROOT(2)

NAME

     chroot -- change root directory

SYNOPSIS

     #include <unistd.h>

     int
     chroot(const char *dirname);

DESCRIPTION

     Dirname is the address of the pathname of a directory, terminated by an ASCII NUL.  Chroot() causes dirname to become the root directory,
     that is, the starting point for path searches of pathnames beginning with '/'.

     In order for a directory to become the root directory a process must have execute (search) access for that directory.

     If the program is not currently running with an altered root directory, it should be noted that chroot() has no effect on the process's cur-
     rent directory.

     If the program is already running with an altered root directory, the process's current directory is changed to the same new root directory.
     This prevents the current directory from being further up the directory tree than the altered root directory.

     This call is restricted to the super-user.

RETURN VALUES

     Upon successful completion, a value of 0 is returned.  Otherwise, a value of -1 is returned and errno is set to indicate an error.

ERRORS

     Chroot() will fail and the root directory will be unchanged if:

     [ENOTDIR]		A component of the path name is not a directory.

     [ENAMETOOLONG]	A component of a pathname exceeded {NAME_MAX} characters, or an entire path name exceeded {PATH_MAX} characters.

     [ENOENT]		The named directory does not exist.

     [EACCES]		Search permission is denied for any component of the path name.

     [ELOOP]		Too many symbolic links were encountered in translating the pathname.

     [EFAULT]		Path points outside the process's allocated address space.

     [EIO]		An I/O error occurred while reading from or writing to the file system.

SEE ALSO

     chdir(2)

WARNINGS

     There are ways for a root process to escape from the chroot jail.

HISTORY

     The chroot() function call appeared in 4.2BSD.

4.2 Berkeley Distribution					   June 4, 1993 					 4.2 Berkeley Distribution

CHROOT(2)						      BSD System Calls Manual							 CHROOT(2)

NAME

     chroot -- change root directory

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <unistd.h>

     int
     chroot(const char *dirname);

DESCRIPTION

     The dirname argument is the address of the pathname of a directory, terminated by an ASCII NUL.  The chroot() system call causes dirname to
     become the root directory, that is, the starting point for path searches of pathnames beginning with '/'.

     In order for a directory to become the root directory a process must have execute (search) access for that directory.

     It should be noted that chroot() has no effect on the process's current directory.

     This call is restricted to the super-user.

     Depending on the setting of the 'kern.chroot_allow_open_directories' sysctl variable, open filedescriptors which reference directories will
     make the chroot() fail as follows:

     If 'kern.chroot_allow_open_directories' is set to zero, chroot() will always fail with EPERM if there are any directories open.

     If 'kern.chroot_allow_open_directories' is set to one (the default), chroot() will fail with EPERM if there are any directories open and the
     process is already subject to the chroot() system call.

     Any other value for 'kern.chroot_allow_open_directories' will bypass the check for open directories

RETURN VALUES

     Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the
     error.

ERRORS

     The chroot() system call will fail and the root directory will be unchanged if:

     [ENOTDIR]		A component of the path name is not a directory.

     [EPERM]		The effective user ID is not the super-user, or one or more filedescriptors are open directories.

     [ENAMETOOLONG]	A component of a pathname exceeded 255 characters, or an entire path name exceeded 1023 characters.

     [ENOENT]		The named directory does not exist.

     [EACCES]		Search permission is denied for any component of the path name.

     [ELOOP]		Too many symbolic links were encountered in translating the pathname.

     [EFAULT]		The dirname argument points outside the process's allocated address space.

     [EIO]		An I/O error occurred while reading from or writing to the file system.

SEE ALSO

     chdir(2), jail(2)

HISTORY

     The chroot() system call appeared in 4.2BSD.  It was marked as ``legacy'' in Version 2 of the Single UNIX Specification (``SUSv2''), and was
     removed in subsequent standards.

BUGS

     If the process is able to change its working directory to the target directory, but another access control check fails (such as a check for
     open directories, or a MAC check), it is possible that this system call may return an error, with the working directory of the process left
     changed.

SECURITY CONSIDERATIONS

     The system have many hardcoded paths to files where it may load after the process starts.	It is generally recommended to drop privileges
     immediately after a successful chroot call, and restrict write access to a limited subtree of the chroot root, for instance, setup the sand-
     box so that the sandboxed user will have no write access to any well-known system directories.

BSD
								  January 3, 2012							       BSD