table of contents
JAIL(2) | System Calls Manual | JAIL(2) |
NAME¶
jail, jail_get, jail_set, jail_remove, jail_attach — create and manage system jailsLIBRARY¶
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 { u_int32_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 managment 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 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
andJAIL_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.
JAIL_DYING
- Allow getting a jail that is in the process of being removed.
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.
PRISON?¶
Once a process has been put in a prison, it and its descendants 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. All connections to/from
the loopback address (127.0.0.1
for IPv4,
::1
for IPv6) will be changed to be to/from the
primary address of the jail for the given address family.
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 name currently set for the prison for jailed processes.
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.
- [
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
orJAIL_UPDATE
flags is not set. - [
ENAMETOOLONG
] - A supplied string parameter is longer than allowed.
- [
EAGAIN
] - There are no jail IDs left.
- [
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.
- [
EINVAL
] - The jail specified by jid does not exist.
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 “http://www.rndassociates.com/
” who
contributed it to FreeBSD.
James Gritton added the extensible jail parameters and hierarchical jails.
June 23, 2009 | Debian |