1.\" 2.\"---------------------------------------------------------------------------- 3.\""THE BEER-WARE LICENSE" (Revision 42): 4.\"<phk@FreeBSD.ORG> wrote this file. As long as you retain this notice you 5.\"can do whatever you want with this stuff. If we meet some day, and you think 6.\"this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp 7.\"---------------------------------------------------------------------------- 8.\" 9.\"$FreeBSD: src/lib/libc/sys/jail.2,v 1.10.2.10 2002/12/12 05:26:38 trhodes Exp $ 10.\"$DragonFly: src/lib/libc/sys/jail.2,v 1.11 2007/11/21 19:12:40 swildner Exp $ 11.\" 12.Dd April 28, 1999 13.Dt JAIL 2 14.Os 15.Sh NAME 16.Nm jail 17.Nd imprison current process and future descendants 18.Sh LIBRARY 19.Lb libc 20.Sh SYNOPSIS 21.In sys/types.h 22.In sys/jail.h 23.Ft int 24.Fn jail "struct jail *jail" 25.Sh DESCRIPTION 26The 27.Nm 28system call sets up a jail and locks the current process in it. 29.Pp 30The argument is a pointer to a structure describing the prison: 31.Bd -literal -offset indent 32struct jail { 33 uint32_t version; 34 char *path; 35 char *hostname; 36 uint32_t n_ips; 37 struct sockaddr_storage *ips; 38}; 39.Ed 40.Pp 41.Dq Li version 42defines the version of the API in use. It should be set to 1 at this time. 43.Pp 44The 45.Dq Li path 46pointer should be set to the directory which is to be the root of the 47prison. 48.Pp 49The 50.Dq Li hostname 51pointer can be set to the hostname of the prison. This can be changed 52from the inside of the prison. 53.Pp 54.Dq Li n_ips 55is the number of IP addresses that are on ips. 56.Pp 57The 58.Dq ips 59pointer contains the IP addresses assigned to the jail. 60.Sh PRISON 61Once a process has been put in a prison, it and its descendants cannot escape 62the prison. 63A process can be attached to a prison by calling 64.Xr jail_attach 2 . 65.Pp 66Inside the prison, the concept of "superuser" is very diluted. In general, 67it can be assumed that nothing can be mangled from inside a prison which 68does not exist entirely inside that prison. For instance the directory 69tree below 70.Dq Li path 71can be manipulated all the ways a root can normally do it, including 72.Dq Li "rm -rf /*" 73but new device special nodes cannot be created because they reference 74shared resources (the device drivers in the kernel). 75.Pp 76All IP activity will be forced to happen to/from the IP numbers specified, 77which should be an alias on one or more of the network interfaces. 78.Pp 79It is possible to identify a process as jailed by examining 80.Dq Li /proc/<pid>/status : 81it will show a field near the end of the line, either as 82a single hyphen for a process at large, or the hostname currently 83set for the prison for jailed processes. 84.Pp 85The program 86.Xr jls 8 87ca be used to identify all active jails. 88.Sh RETURN VALUES 89If successful, 90.Fn jail 91returns a non-negative integer, termed the jail identifier (JID). 92It returns -1 on failure, and sets 93.Va errno 94to indicate the error. 95.Sh ERRORS 96The 97.Fn jail 98system call will fail if: 99.Bl -tag -width Er 100.It Bq Er EINVAL 101The version number of the argument is not correct. 102.El 103.Pp 104Further 105.Fn jail 106calls 107.Xr chroot 2 108internally, so it can fail for all the same reasons. 109Please consult the 110.Xr chroot 2 111manual page for details. 112.Sh SEE ALSO 113.Xr chdir 2 , 114.Xr chroot 2 , 115.Xr jail_attach 2 , 116.Xr jail 8 , 117.Xr jexec 8 , 118.Xr jls 8 119.Sh HISTORY 120The 121.Fn jail 122function call appeared in 123.Fx 4.0 . 124.Sh AUTHORS 125The jail feature was written by 126.An Poul-Henning Kamp 127for R&D Associates 128.Dq Pa http://www.rndassociates.com/ 129who contributed it to 130.Fx . 131