JAIL(2) FreeBSD System Calls Manual JAIL(2)
NAME
jail, jail_get, jail_set, jail_remove, jail_attach - create and manage
system jails
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <sys/param.h>
#include <sys/jail.h>
int
jail(struct jail *jail);
int
jail_attach(int jid);
int
jail_remove(int jid);
#include <sys/uio.h>
int
jail_get(struct iovec *iov, u_int niov, int flags);
int
jail_set(struct iovec *iov, u_int niov, int flags);
DESCRIPTION
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 {
uint32_t version;
char *path;
char *hostname;
char *jailname;
unsigned int ip4s;
unsigned int ip6s;
struct in_addr *ip4;
struct in6_addr *ip6;
};
"version" defines the version of the API in use. JAIL_API_VERSION is
defined for the current version.
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 "jailname" pointer is an optional name that can be assigned to the
jail for example for management purposes.
The "ip4s" and "ip6s" give the numbers of IPv4 and IPv6 addresses that
will be passed via their respective pointers.
The "ip4" and "ip6" pointers can be set to an arrays of IPv4 and IPv6
addresses to be assigned to the prison, or NULL if none. IPv4 addresses
must be in network byte order.
This is equivalent to, and deprecated in favor of, the jail_set() system
call (see below), with the parameters path, host.hostname, name,
ip4.addr, and ip6.addr, and with the JAIL_ATTACH flag.
The jail_set() system call creates a new jail, or modifies an existing
one, and optionally locks the current process in it. Jail parameters are
passed as an array of name-value pairs in the array iov, containing niov
elements. Parameter names are a null-terminated string, and values may
be strings, integers, or other arbitrary data. Some parameters are
boolean, and do not have a value (their length is zero) but are set by
the name alone with or without a "no" prefix, e.g. persist or nopersist.
Any parameters not set will be given default values, generally based on
the current environment.
Jails have a set of core parameters, and modules can add their own jail
parameters. The current set of available parameters, and their formats,
can be retrieved via the security.jail.param sysctl MIB entry. Notable
parameters include those mentioned in the jail() description above, as
well as jid and name, which identify the jail being created or modified.
See jail(8) for more information on the core jail parameters.
The flags arguments consists of one or more of the following flags:
JAIL_CREATE
Create a new jail. If a jid or name parameters exists, they must
not refer to an existing jail.
JAIL_UPDATE
Modify an existing jail. One of the jid or name parameters must
exist, and must refer to an existing jail. If both JAIL_CREATE
and JAIL_UPDATE are set, a jail will be created if it does not
yet exist, and modified if it does exist.
JAIL_ATTACH
In addition to creating or modifying the jail, attach the current
process to it, as with the jail_attach() system call.
JAIL_DYING
Allow setting a jail that is in the process of being removed.
The jail_get() system call retrieves jail parameters, using the same
name-value list as jail_set() in the iov and niov arguments. The jail to
read can be specified by either jid or name by including those parameters
in the list. If they are included but are not intended to be the search
key, they should be cleared (zero and the empty string respectively).
The special parameter lastjid can be used to retrieve a list of all
jails. It will fetch the jail with the jid above and closest to the
passed value. The first jail (usually but not always jid 1) can be found
by passing a lastjid of zero.
The flags arguments consists of one or more following flags:
JAIL_DYING
Allow getting a jail that is in the process of being removed.
The jail_attach() system call attaches the current process to an existing
jail, identified by jid. It changes the process's root and current
directories to the jail's path directory.
The jail_remove() system call removes the jail identified by jid. It
will kill all processes belonging to the jail, and remove any children of
that jail.
RETURN VALUES
If successful, jail(), jail_set(), and jail_get() return a non-negative
integer, termed the jail identifier (JID). They return -1 on failure,
and set errno to indicate the error.
The jail_attach() and jail_remove() functions return the value 0 if
successful; otherwise the value -1 is returned and the global variable
errno is set to indicate the error.
ERRORS
The jail() system call will fail if:
[EPERM] This process is not allowed to create a jail, either
because it is not the super-user, or because it would
exceed the jail's children.max limit.
[EFAULT] jail points to an address outside the allocated
address space of the process.
[EINVAL] The version number of the argument is not correct.
[EAGAIN] No free JID could be found.
The jail_set() system call will fail if:
[EPERM] This process is not allowed to create a jail, either
because it is not the super-user, or because it would
exceed the jail's children.max limit.
[EPERM] A jail parameter was set to a less restrictive value
then the current environment.
[EFAULT] Iov, or one of the addresses contained within it,
points to an address outside the allocated address
space of the process.
[ENOENT] The jail referred to by a jid or name parameter does
not exist, and the JAIL_CREATE flag is not set.
[ENOENT] The jail referred to by a jid is not accessible by the
process, because the process is in a different jail.
[EEXIST] The jail referred to by a jid or name parameter
exists, and the JAIL_UPDATE flag is not set.
[EINVAL] A supplied parameter is the wrong size.
[EINVAL] A supplied parameter is out of range.
[EINVAL] A supplied string parameter is not null-terminated.
[EINVAL] A supplied parameter name does not match any known
parameters.
[EINVAL] One of the JAIL_CREATE or JAIL_UPDATE flags is not
set.
[ENAMETOOLONG] A supplied string parameter is longer than allowed.
[EAGAIN] There are no jail IDs left.
The jail_get() system call will fail if:
[EFAULT] Iov, or one of the addresses contained within it,
points to an address outside the allocated address
space of the process.
[ENOENT] The jail referred to by a jid or name parameter does
not exist.
[ENOENT] The jail referred to by a jid is not accessible by the
process, because the process is in a different jail.
[ENOENT] The lastjid parameter is greater than the highest
current jail ID.
[EINVAL] A supplied parameter is the wrong size.
[EINVAL] A supplied parameter name does not match any known
parameters.
The jail_attach() and jail_remove() system calls will fail if:
[EPERM] A user other than the super-user attempted to attach
to or remove a jail.
[EINVAL] The jail specified by jid does not exist.
Further jail(), jail_set(), and jail_attach() call chroot(2) internally,
so they can fail for all the same reasons. Please consult the chroot(2)
manual page for details.
SEE ALSO
chdir(2), chroot(2), jail(8)
HISTORY
The jail() system call appeared in FreeBSD 4.0. The jail_attach() system
call appeared in FreeBSD 5.1. The jail_set(), jail_get(), and
jail_remove() system calls appeared in FreeBSD 8.0.
AUTHORS
The jail feature was written by Poul-Henning Kamp for R&D Associates who
contributed it to FreeBSD.
James Gritton added the extensible jail parameters and hierarchical
jails.
FreeBSD 13.1-RELEASE-p6 February 19, 2021 FreeBSD 13.1-RELEASE-p6
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