Date: Tue, 6 Aug 2019 17:05:58 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r350640 - head/share/man/man7 Message-ID: <201908061705.x76H5wZU037479@repo.freebsd.org>
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Author: kib Date: Tue Aug 6 17:05:58 2019 New Revision: 350640 URL: https://svnweb.freebsd.org/changeset/base/350640 Log: Provide the list of knobs related to mitigations. Discussed with: bjk, emaste Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D21087 Modified: head/share/man/man7/security.7 Modified: head/share/man/man7/security.7 ============================================================================== --- head/share/man/man7/security.7 Tue Aug 6 16:53:25 2019 (r350639) +++ head/share/man/man7/security.7 Tue Aug 6 17:05:58 2019 (r350640) @@ -1,5 +1,10 @@ .\" Copyright (C) 1998 Matthew Dillon. All rights reserved. +.\" Copyright (c) 2019 The FreeBSD Foundation, Inc. .\" +.\" Parts of this documentation were written by +.\" Konstantin Belousov <kib@FreeBSD.org> under sponsorship +.\" from the FreeBSD Foundation. +.\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: @@ -23,7 +28,7 @@ .\" .\" $FreeBSD$ .\" -.Dd December 25, 2013 +.Dd July 27, 2019 .Dt SECURITY 7 .Os .Sh NAME @@ -941,12 +946,125 @@ option that SSH allows in its .Pa authorized_keys file to make the key only usable to entities logging in from specific machines. +.Sh KNOBS AND TWEAKS +.Fx +provides several knobs and tweak handles that make some introspection +information access more restricted. +Some people consider this as improving system security, so the knobs are +briefly listed there, together with controls which enable some mitigations +of the hardware state leaks. +.Bl -tag -width security.bsd.unprivileged_proc_debug +.It Dv security.bsd.see_other_uids +Controls visibility of processes owned by different uid. +The knob directly affects the +.Dv kern.proc +sysctls filtering of data, which results in restricted output from +utilities like +.Xr ps 1 . +.It Dv security.bsd.see_other_gids +Same, for processes owned by different gid. +.It Dv security.bsd.see_jail_proc +Same, for processes belonging to a jail. +.It Dv security.bsd.conservative_signals +When enabled, unprivileged users are only allowed to send job control +and usual termination signals like +.Dv SIGKILL , +.Dv SIGINT , +and +.Dv SIGTERM , +to the processes executing programs with changed uids. +.It Dv security.bsd.unprivileged_proc_debug +Controls availability of the process debugging facilities to non-root users. +See also +.Xr proccontrol 1 +mode +.Dv trace . +.It Dv vm.pmap.pti +Tunable, amd64-only. +Enables mode of operation of virtual memory system where usermode page +tables are sanitized to prevent so-called Meltdown information leak on +some Intel CPUs. +By default, the system detects whether the CPU needs the workaround, +and enables it automatically. +See also +.Xr proccontrol 1 +mode +.Dv kpti . +.It Dv hw.mds_disable +amd64 and i386. +Controls Microarchitectural Data Sampling hardware information leak +mitigation. +.It Dv hw.spec_store_bypass_disable +amd64 and i386. +Controls Speculative Store Bypass hardware information leak mitigation. +.It Dv hw.ibrs_disable +amd64 and i386. +Controls Indirect Branch Restricted Speculation hardware information leak +mitigation. +.It Dv machdep.syscall_ret_l1d_flush +amd64. +Controls force-flush of L1D cache on return from syscalls which report +errors other than +.Ev EEXIST , +.Ev EAGAIN , +.Ev EXDEV , +.Ev ENOENT , +.Ev ENOTCONN , +and +.Ev EINPROGRESS . +This is mostly a paranoid setting added to prevent hypothetical exploitation +of unknown gadgets for unknown hardware issues. +The error codes exclusion list is composed of the most common errors which +typically occurs on normal system operation. +.It Dv machdep.nmi_flush_l1d_sw +amd64. +Controls force-flush of L1D cache on NMI; +this provides software assist for bhyve mitigation of L1 terminal fault +hardware information leak. +.It Dv hw.vmm.vmx.l1d_flush +amd64. +Controls the mitigation of L1 Terminal Fault in bhyve hypervisor. +.It Dv kern.elf32.aslr.enable +Controls system-global Address Space Layour Randomization (ASLR) for +normal non-PIE (Position Independent Executable) 32bit binaries. +See also +.Xr proccontrol 1 +mode +.Dv aslr , +also affected by the per-image control note flag. +.It Dv kern.elf32.aslr.pie_enable +Controls system-global Address Space Layout Randomization for +position-independent (PIE) 32bit binaries. +.It Dv kern.elf32.aslr.honor_sbrk +Makes ASLR less aggressive and more compatible with old binaries +relying on the sbrk area. +.It Dv kern.elf32.aslr.aslr_stack_gap +If ASLR is enabled for a binary, a non-zero value creates a randomized +stack gap between strings and the end of the aux vector. +The value is the maximum percentage of main stack to waste on the gap. +Cannot be greater than 50, i.e., at most half of the stack. +.It Dv kern.elf64.aslr.enable +64bit binaries ASLR control. +.It Dv kern.elf64.aslr.pie_enable +64bit PIE binaries ASLR control. +.It Dv kern.elf64.aslr.honor_sbrk +64bit binaries ASLR sbrk compatibility control. +.It Dv kern.elf32.aslr.aslr_stack_gap +Controls stack gap for 64bit binaries. +.It Dv kern.elf32.nxstack +Enables non-executable stack for 32bit processes. +Enabled by default if supported by hardware and corresponding binary. +.It Dv kern.elf64.nxstack +Enables non-executable stack for 64bit processes. +.El .Sh SEE ALSO .Xr chflags 1 , .Xr find 1 , .Xr md5 1 , .Xr netstat 1 , .Xr openssl 1 , +.Xr proccontrol 1 , +.Xr ps 1 , .Xr ssh 1 , .Xr xdm 1 Pq Pa ports/x11/xorg-clients , .Xr group 5 ,
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