jail, jail_attach -- imprison current process and future decendants
Standard C Library (libc, -lc)
#include <sys/param.h>
#include <sys/jail.h>
int
jail(struct jail *jail);
int
jail_attach(int jid);
The jail() system call sets up a jail and locks the current process in
it.
The argument is a pointer to a structure describing the prison:
struct jail {
u_int32_t version;
char *path;
char *hostname;
u_int32_t ip_number;
};
``version'' defines the version of the API in use. It should be set to
zero at this time.
The ``path'' pointer should be set to the directory which is to be the
root of the prison.
The ``hostname'' pointer can be set to the hostname of the prison. This
can be changed from the inside of the prison.
The ``ip_number'' can be set to the IP number assigned to the prison.
The jail_attach() system call attaches the current process to an existing
jail, identified by jid.
If successful, jail() returns a non-negative integer, termed the jail
identifier (JID). It returns -1 on failure, and sets errno to indicate
the error.
The jail_attach() function returns the value 0 if successful; otherwise
the value -1 is returned and the global variable errno is set to indicate
the error.
PRISON?
Once a process has been put in a prison, it and its decendants cannot
escape the prison.
Inside the prison, the concept of ``superuser'' is very diluted. In general,
it can be assumed that nothing can be mangled from inside a prison
which does not exist entirely inside that prison. For instance the
directory tree below ``path'' can be manipulated all the ways a root can
normally do it, including ``rm -rf /*'' but new device special nodes cannot
be created because they reference shared resources (the device drivers
in the kernel). The effective ``securelevel'' for a process is the
greater of the global ``securelevel'' or, if present, the per-jail
``securelevel''.
All IP activity will be forced to happen to/from the IP number specified,
which should be an alias on one of the network interfaces.
It is possible to identify a process as jailed by examining
``/proc/<pid>/status'': it will show a field near the end of the line,
either as a single hyphen for a process at large, or the hostname currently
set for the prison for jailed processes.
The jail() system call will fail if:
[EINVAL] The version number of the argument is not correct.
Further jail() calls chroot(2) internally, so it can fail for all the
same reasons. Please consult the chroot(2) manual page for details.
chdir(2), chroot(2)
The jail() system call appeared in FreeBSD 4.0. The jail_attach() system
call appeared in FreeBSD 5.1.
The jail feature was written by Poul-Henning Kamp for R&D Associates
``http://www.rndassociates.com/'' who contributed it to FreeBSD.
FreeBSD 5.2.1 April 8, 2003 FreeBSD 5.2.1 [ Back ] | 