.\" .\"---------------------------------------------------------------------------- .\""THE BEER-WARE LICENSE" (Revision 42): .\" wrote this file. As long as you retain this notice you .\"can do whatever you want with this stuff. If we meet some day, and you think .\"this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp .\"---------------------------------------------------------------------------- .\" .\"$FreeBSD: src/lib/libc/sys/jail.2,v 1.10.2.10 2002/12/12 05:26:38 trhodes Exp $ .\"$DragonFly: src/lib/libc/sys/jail.2,v 1.11 2007/11/21 19:12:40 swildner Exp $ .\" .Dd April 28, 1999 .Dt JAIL 2 .Os .Sh NAME .Nm jail .Nd imprison current process and future descendants .Sh LIBRARY .Lb libc .Sh SYNOPSIS .In sys/types.h .In sys/jail.h .Ft int .Fn jail "struct jail *jail" .Sh DESCRIPTION The .Nm 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 { uint32_t version; char *path; char *hostname; uint32_t n_ips; struct sockaddr_storage *ips; }; .Ed .Pp .Dq Li version defines the version of the API in use. It should be set to 1 at this time. .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 .Dq Li n_ips is the number of IP addresses that are on ips. .Pp The .Dq ips pointer contains the IP addresses assigned to the jail. .Sh PRISON Once a process has been put in a prison, it and its descendants cannot escape the prison. A process can be attached to a prison by calling .Xr jail_attach 2 . .Pp 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 .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). .Pp All IP activity will be forced to happen to/from the IP numbers specified, which should be an alias on one or more of the network interfaces. .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 hostname currently set for the prison for jailed processes. .Pp The program .Xr jls 8 ca be used to identify all active jails. .Sh RETURN VALUES If successful, jail() returns a non-negative integer, termed the jail identifier (JID). It returns -1 on failure, and sets .Va errno to indicate the error. .Sh ERRORS The .Fn jail system call will fail if: .Bl -tag -width Er .It Bq Er EINVAL The version number of the argument is not correct. .El .Pp Further .Fn jail calls .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_attach 2 , .Xr jail 8 , .Xr jexec 8 , .Xr jls 8 .Sh HISTORY The .Fn jail function call appeared in .Fx 4.0 . .Sh AUTHORS The jail feature was written by .An Poul-Henning Kamp for R&D Associates .Dq Pa http://www.rndassociates.com/ who contributed it to .Fx .