path: root/bin/systrace/systrace.1

.\"	$OpenBSD: systrace.1,v 1.19 2002/06/21 15:28:46 provos Exp $
.\"
.\" Copyright 2002 Niels Provos <provos@citi.umich.edu>
.\" All rights reserved.
.\"
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.\" modification, are permitted provided that the following conditions
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.\" 1. Redistributions of source code must retain the above copyright
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.\"    documentation and/or other materials provided with the distribution.
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.\"    must display the following acknowledgement:
.\"      This product includes software developed by Niels Provos.
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.\" Manual page, using -mandoc macros
.\"
.Dd June 3, 2002
.Dt SYSTRACE 1
.Os
.Sh NAME
.Nm systrace
.Nd generates and enforces system call policies
.Sh SYNOPSIS
.Nm systrace
.Op Fl aAitU
.Op Fl g Ar gui
.Op Fl f Ar file
.Op Fl p Ar pid
.Ar command ...
.Sh DESCRIPTION
The
.Nm
utility enforces system call policies for applications by
constraining the application's access to the system.
The policy is generated interactively.
Operations not covered by the policy raise an
alarm and allow an user to refine the currently configured policy.
.Pp
The options are as follows:
.Bl -tag -width Dfxfile
.It Fl a
Enables automatic enforcement of configured policies.
An operation not covered by policy is denied and logged via
.Xr syslog 3 .
.It Fl A
Automatically generate a policy that allows every operation the
application executes.
The created policy functions as a base that can be refined.
.It Fl i
Inherits the policy of the first executed binary to all children.
.It Fl t
Uses text mode to ask for interactive policy generation.
.It Fl U
Ignore user configured policies and use only global system policies.
.It Fl g Ar gui
Specifies an alternative location for the notification user interface.
.It Fl f Ar file
The policies specified in
.Ar file
are added to the policies that
.Nm
knows about.
.It Fl p Ar pid
Specifies the pid of a process that
.Nm
should attach to.
The full path name of the corresponding binary has to be specified
as
.Ar command .
.El
.Pp
.Sh POLICY
The policy is specified via the following grammar:
.Bd -literal -offset AAA
filter = expression "then" action errorcode
expression = symbol | "not" expression | "(" expression ")" |
    expression "and" expression | expression "or" expression
symbol = string typeoff "match" cmdstring |
    string typeoff "eq" cmdstring | string typeoff "neq" cmdstring |
    string typeoff "sub" cmdstring | string typeoff "nsub" cmdstring |
    string typeoff "inpath" cmdstring | "true"
typeoff = /* empty */ | "[" number "]"
action = "permit" | "deny"
errorcode = /* empty */ | "[" string "]"
.Ed
.Pp
The
.Va cmdstring
is an arbitrary string enclosed with quotation marks.
The
.Va errorcode
is used to return an
.Xr errno 2
value to the system call when using a
.Va deny
action.  The value
.Do
inherit
.Dc
has a special meaning when used with a
.Va permit
rule for the
.Va execve
system call.
In that case, the current policy is inherited for the new binary.
.Pp
The filter operations have the following meaning:
.Bl -hang -width Dinpath -offset AAA
.It match
Evaluates to true if file name globbing according to
.Xr fnmatch 3
succeeds.
.It eq
Evaluates to true if the system call argument matches
.Va cmdstring
exactly.
.It neq
This is the logical negation of
.Va eq .
.It sub
Performs a substring match on the system call argument.
.It nsub
This is the logical negation of
.Va sub .
.It inpath
Evaluates to true if the system call argument is a subpath of
.Va cmdstring .
.El
.Pp
Policy entries may contain an appended predicate.
Predicates have the following format:
.Bd -literal -offset AAA
", if" {"user", "group"} {"=", "!="} string
.Ed
.Pp
A rule is added to the configured policy only if its predicate
evaluates to true.
.Sh EXAMPLES
An excerpt from a sample
.Xr ls 1
policy might look as follows:
.Bd -literal -offset AAA
Policy: /bin/ls, Emulation: native
[...]
	native-open: filename eq "$HOME" and oflags sub "ro" then permit
	native-fchdir: permit
[...]
	native-open: filename eq "/tmp" and oflags sub "ro" then permit
	native-stat: permit
	native-open: filename match "$HOME/*" and oflags sub "ro" then permit
	native-open: filename eq "/etc/pwd.db" and oflags sub "ro" then permit
[...]
	native-open: filename eq "/etc" then deny[eperm], if group != wheel
.Ed
.Sh FILES
.Bl -tag -width xHOME/xsystrace -compact
.It Pa /dev/systrace
systrace device
.It Pa /etc/systrace
global systrace policies
.It Pa $HOME/.systrace
user specified policies
.El
.Sh SEE ALSO
.Xr systrace 4
.Sh BUGS
Applications that use clone()-like system calls to share the complete
address space between processes may be able to replace system call
arguments after they have been evaluated by
.Nm
and escape policy enforcement.
.Sh AUTHORS
The
.Nm
utility has been developed by Niels Provos.