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ptrace(2): document policies affecting access to the facility

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Reviewed by:	emaste
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D33986
This commit is contained in:
Konstantin Belousov 2022-01-22 01:26:23 +02:00
parent fe6db72708
commit a393644ecb
1 changed files with 50 additions and 1 deletions
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51
lib/libc/sys/ptrace.2
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@ -2,7 +2,7 @@
.\" $NetBSD: ptrace.2,v 1.2 1995/02/27 12:35:37 cgd Exp $
.\"
.\" This file is in the public domain.
.Dd May 20, 2021
.Dd January 22, 2022
.Dt PTRACE 2
.Os
.Sh NAME
@ -122,6 +122,55 @@ Kernel drops any
signals queued to the traced children, which could be either generated by
not yet consumed debug events, or sent by other means, the later should
not be done anyway.
.Sh DISABLING PTRACE
The
.Nm
subsystem provides rich facilities to manipulate other processes state.
Sometimes it may be desirable to disallow it either completely, or limit
its scope.
The following controls are provided for this:
.Bl -tag -width security.bsd.unprivileged_proc_debug
.It Dv security.bsd.allow_ptrace
Setting this sysctl to zero value makes
.Xr ptrace 2
return
.Er ENOSYS
always as if the syscall is not implemented by the kernel.
.It Dv security.bsd.unprivileged_proc_debug
Setting this sysctl to zero disallows use of
.Fn ptrace
by unprivileged processes.
.It Dv security.bsd.see_other_uids
Setting this sysctl to zero value disallows
.Fn ptrace
requests from targeting processes with the real user identifier different
from the real user identifier of the caller.
The requests return
.Er ESRCH
if policy is not met.
.It Dv security.bsd.see_other_gids
Setting this sysctl to zero value disallows
.Fn ptrace
requests from process belonging to a group that is not also one of
the group of the target process.
The requests return
.Er ESRCH
if policy is not met.
.It Dv securelevel and init
The
.Xr init 1
process can only be traced with
.Nm
if securelevel is zero.
.It Dv procctl(2) PROC_TRACE_CTL
Process can deny attempts to trace itself with
.Xr procctl 2
.Dv PROC_TRACE_CTL
request.
In this case requests return
.Xr EPERM
error.
.El
.Sh TRACING EVENTS
.Pp
Each traced process has a tracing event mask.