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143 lines
3.3 KiB
Groff
143 lines
3.3 KiB
Groff
.\"
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.\"----------------------------------------------------------------------------
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.\""THE BEER-WARE LICENSE" (Revision 42):
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.\"<phk@FreeBSD.ORG> wrote this file. As long as you retain this notice you
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.\"can do whatever you want with this stuff. If we meet some day, and you think
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.\"this stuff is worth it, you can buy me a beer in return. Poul-Henning Kamp
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.\"----------------------------------------------------------------------------
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.\"
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.\"$FreeBSD$
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.\"
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.Dd April 8, 2003
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.Dt JAIL 2
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.Os
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.Sh NAME
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.Nm jail , jail_attach
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.Nd imprison current process and future descendants
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/param.h
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.In sys/jail.h
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.Ft int
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.Fn jail "struct jail *jail"
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.Ft int
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.Fn jail_attach "int jid"
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.Sh DESCRIPTION
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The
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.Fn jail
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system call sets up a jail and locks the current process in it.
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.Pp
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The argument is a pointer to a structure describing the prison:
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.Bd -literal -offset indent
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struct jail {
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u_int32_t version;
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char *path;
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char *hostname;
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u_int32_t ip_number;
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};
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.Ed
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.Pp
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.Dq Li version
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defines the version of the API in use.
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It should be set to zero at this time.
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.Pp
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The
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.Dq Li path
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pointer should be set to the directory which is to be the root of the
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prison.
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.Pp
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The
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.Dq Li hostname
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pointer can be set to the hostname of the prison.
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This can be changed
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from the inside of the prison.
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.Pp
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The
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.Dq Li ip_number
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can be set to the IP number assigned to the prison.
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.Pp
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The
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.Fn jail_attach
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system call attaches the current process to an existing jail,
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identified by
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.Fa jid .
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.Sh RETURN VALUES
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If successful,
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.Fn jail
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returns a non-negative integer, termed the jail identifier (JID).
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It returns \-1 on failure, and sets
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.Va errno
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to indicate the error.
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.Pp
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.Rv -std jail_attach
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.Sh PRISON?
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Once a process has been put in a prison, it and its descendants cannot escape
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the prison.
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.Pp
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Inside the prison, the concept of
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.Dq superuser
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is very diluted.
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In general,
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it can be assumed that nothing can be mangled from inside a prison which
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does not exist entirely inside that prison.
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For instance the directory
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tree below
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.Dq Li path
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can be manipulated all the ways a root can normally do it, including
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.Dq Li "rm -rf /*"
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but new device special nodes cannot be created because they reference
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shared resources (the device drivers in the kernel).
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The effective
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.Dq securelevel
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for a process is the greater of the global
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.Dq securelevel
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or, if present, the per-jail
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.Dq securelevel .
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.Pp
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All IP activity will be forced to happen to/from the IP number specified,
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which should be an alias on one of the network interfaces.
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.Pp
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It is possible to identify a process as jailed by examining
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.Dq Li /proc/<pid>/status :
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it will show a field near the end of the line, either as
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a single hyphen for a process at large, or the hostname currently
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set for the prison for jailed processes.
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.Sh ERRORS
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The
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.Fn jail
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system call
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will fail if:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The version number of the argument is not correct.
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.El
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.Pp
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Further
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.Fn jail
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calls
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.Xr chroot 2
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internally, so it can fail for all the same reasons.
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Please consult the
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.Xr chroot 2
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manual page for details.
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.Sh SEE ALSO
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.Xr chdir 2 ,
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.Xr chroot 2
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.Sh HISTORY
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The
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.Fn jail
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system call appeared in
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.Fx 4.0 .
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The
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.Fn jail_attach
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system call appeared in
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.Fx 5.1 .
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.Sh AUTHORS
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The jail feature was written by
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.An Poul-Henning Kamp
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for R&D Associates
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.Dq Li http://www.rndassociates.com/
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who contributed it to
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.Fx .
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