.\" Copyright (c) 1999 Poul-Henning Kamp. .\" Copyright (c) 2009 James Gritton. .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" $FreeBSD$ .\" .Dd June 23, 2009 .Dt JAIL 2 .Os .Sh NAME .Nm jail , .Nm jail_get , .Nm jail_set , .Nm jail_remove , .Nm jail_attach .Nd create and manage system jails .Sh LIBRARY .Lb libc .Sh SYNOPSIS .In sys/param.h .In sys/jail.h .Ft int .Fn jail "struct jail *jail" .Ft int .Fn jail_attach "int jid" .Ft int .Fn jail_remove "int jid" .In sys/uio.h .Ft int .Fn jail_get "struct iovec *iov" "u_int niov" "int flags" .Ft int .Fn jail_set "struct iovec *iov" "u_int niov" "int flags" .Sh DESCRIPTION The .Fn jail system call sets up a jail and locks the current process in it. .Pp The argument is a pointer to a structure describing the prison: .Bd -literal -offset indent 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; }; .Ed .Pp .Dq Li version defines the version of the API in use. .Dv JAIL_API_VERSION is defined for the current version. .Pp The .Dq Li path pointer should be set to the directory which is to be the root of the prison. .Pp The .Dq Li hostname pointer can be set to the hostname of the prison. This can be changed from the inside of the prison. .Pp The .Dq Li jailname pointer is an optional name that can be assigned to the jail for example for managment purposes. .Pp The .Dq Li ip4s and .Dq Li ip6s give the numbers of IPv4 and IPv6 addresses that will be passed via their respective pointers. .Pp The .Dq Li ip4 and .Dq Li 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. .Pp This is equivalent to the .Fn jail_set system call (see below), with the parameters .Va path , .Va host.hostname , .Va name , .Va ip4.addr , and .Va ip6.addr , and with the .Dv JAIL_ATTACH flag. .Pp The .Fn 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 .Fa iov , containing .Fa 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 .Dq no prefix, e.g. .Va persist or .Va nopersist . Any parameters not set will be given default values, generally based on the current environment. .Pp 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 .Va security.jail.param sysctl MIB entry. Notable parameters include those mentioned in the .Fn jail description above, as well as .Va jid and .Va name , which identify the jail being created or modified. See .Xr jail 8 for more information on the core jail parameters. .Pp The .Fa flags arguments consists of one or more of the following flags: .Bl -tag -width indent .It Dv JAIL_CREATE Create a new jail. If a .Va jid or .Va name parameters exists, they must not refer to an existing jail. .It Dv JAIL_UPDATE Modify an existing jail. One of the .Va jid or .Va name parameters must exist, and must refer to an existing jail. If both .Dv JAIL_CREATE and .Dv JAIL_UPDATE are set, a jail will be created if it does not yet exist, and modified if it does exist. .It Dv JAIL_ATTACH In addition to creating or modifying the jail, attach the current process to it, as with the .Fn jail_attach system call. .It Dv JAIL_DYING Allow setting a jail that is in the process of being removed. .El .Pp The .Fn jail_get system call retrieves jail parameters, using the same name-value list as .Fn jail_set in the .Fa iov and .Fa niov arguments. The jail to read can be specified by either .Va jid or .Va 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). .Pp The special parameter .Va 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 .Va lastjid of zero. .Pp The .Fa flags arguments consists of one or more following flags: .Bl -tag -width indent .It Dv JAIL_DYING Allow getting a jail that is in the process of being removed. .El .Pp The .Fn jail_attach system call attaches the current process to an existing jail, identified by .Fa jid . .Pp The .Fn jail_remove system call removes the jail identified by .Fa jid . It will kill all processes belonging to the jail, and remove any children of that jail. .Sh RETURN VALUES If successful, .Fn jail , .Fn jail_set , and .Fn jail_get return a non-negative integer, termed the jail identifier (JID). They return \-1 on failure, and set .Va errno to indicate the error. .Pp .Rv -std jail_attach jail_remove .Sh PRISON? Once a process has been put in a prison, it and its descendants cannot escape the prison. .Pp Inside the prison, the concept of .Dq 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 .Dq Li path can be manipulated all the ways a root can normally do it, including .Dq Li "rm -rf /*" but new device special nodes cannot be created because they reference shared resources (the device drivers in the kernel). The effective .Dq securelevel for a process is the greater of the global .Dq securelevel or, if present, the per-jail .Dq securelevel . .Pp 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 .Pf ( Li 127.0.0.1 for IPv4, .Li ::1 for IPv6) will be changed to be to/from the primary address of the jail for the given address family. .Pp It is possible to identify a process as jailed by examining .Dq Li /proc//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. .Sh ERRORS The .Fn jail system call will fail if: .Bl -tag -width Er .It Bq Er 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 .Va children.max limit. .It Bq Er EFAULT .Fa jail points to an address outside the allocated address space of the process. .It Bq Er EINVAL The version number of the argument is not correct. .It Bq Er EAGAIN No free JID could be found. .El .Pp The .Fn jail_set system call will fail if: .Bl -tag -width Er .It Bq Er 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 .Va children.max limit. .It Bq Er EPERM A jail parameter was set to a less restrictive value then the current environment. .It Bq Er EFAULT .Fa Iov , or one of the addresses contained within it, points to an address outside the allocated address space of the process. .It Bq Er ENOENT The jail referred to by a .Va jid or .Va name parameter does not exist, and the .Dv JAIL_CREATE flag is not set. .It Bq Er ENOENT The jail referred to by a .Va jid is not accessible by the process, because the process is in a different jail. .It Bq Er EEXIST The jail referred to by a .Va jid or .Va name parameter exists, and the .Dv JAIL_UPDATE flag is not set. .It Bq Er EINVAL A supplied parameter is the wrong size. .It Bq Er EINVAL A supplied parameter is out of range. .It Bq Er EINVAL A supplied string parameter is not null-terminated. .It Bq Er EINVAL A supplied parameter name does not match any known parameters. .It Bq Er EINVAL One of the .Dv JAIL_CREATE or .Dv JAIL_UPDATE flags is not set. .It Bq Er ENAMETOOLONG A supplied string parameter is longer than allowed. .It Bq Er EAGAIN There are no jail IDs left. .El .Pp The .Fn jail_get system call will fail if: .Bl -tag -width Er .It Bq Er EFAULT .Fa Iov , or one of the addresses contained within it, points to an address outside the allocated address space of the process. .It Bq Er ENOENT The jail referred to by a .Va jid or .Va name parameter does not exist. .It Bq Er ENOENT The jail referred to by a .Va jid is not accessible by the process, because the process is in a different jail. .It Bq Er ENOENT The .Va lastjid parameter is greater than the highest current jail ID. .It Bq Er EINVAL A supplied parameter is the wrong size. .It Bq Er EINVAL A supplied parameter name does not match any known parameters. .El .Pp The .Fn jail_attach and .Fn jail_remove system calls will fail if: .Bl -tag -width Er .It Bq Er EINVAL The jail specified by .Fa jid does not exist. .El .Pp Further .Fn jail , .Fn jail_set , and .Fn jail_attach call .Xr chroot 2 internally, so it can fail for all the same reasons. Please consult the .Xr chroot 2 manual page for details. .Sh SEE ALSO .Xr chdir 2 , .Xr chroot 2 , .Xr jail 8 .Sh HISTORY The .Fn jail system call appeared in .Fx 4.0 . The .Fn jail_attach system call appeared in .Fx 5.1 . The .Fn jail_set , .Fn jail_get , and .Fn jail_remove system calls appeared in .Fx 8.0 . .Sh AUTHORS The jail feature was written by .An Poul-Henning Kamp for R&D Associates .Dq Li http://www.rndassociates.com/ who contributed it to .Fx . .An James Gritton added the extensible jail parameters and hierarchical jails.