e5fff57dd0
Rather than using a special value to denote "use the default router", treat the absence of the -g option to mean the same thing. The in-kernel netdump client will always attempt to reach the server directly before falling back to the configured gateway anyway. This change makes it cleaner to support a hostname value for -g. Reviewed by: cem MFC after: 3 days Differential Revision: https://reviews.freebsd.org/D18025
376 lines
9.5 KiB
Groff
376 lines
9.5 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" From: @(#)swapon.8 8.1 (Berkeley) 6/5/93
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd November 17, 2018
|
|
.Dt DUMPON 8
|
|
.Os
|
|
.Sh NAME
|
|
.Nm dumpon
|
|
.Nd "specify a device for crash dumps"
|
|
.Sh SYNOPSIS
|
|
.Nm
|
|
.Op Fl v
|
|
.Op Fl k Ar pubkey
|
|
.Op Fl Z
|
|
.Op Fl z
|
|
.Ar device
|
|
.Nm
|
|
.Op Fl v
|
|
.Op Fl k Ar pubkey
|
|
.Op Fl Z
|
|
.Op Fl z
|
|
.Op Fl g Ar gateway
|
|
.Fl s Ar server
|
|
.Fl c Ar client
|
|
.Ar iface
|
|
.Nm
|
|
.Op Fl v
|
|
.Cm off
|
|
.Nm
|
|
.Op Fl v
|
|
.Fl l
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
utility is used to configure where the kernel can save a crash dump in the case
|
|
of a panic.
|
|
.Pp
|
|
System administrators should typically configure
|
|
.Nm
|
|
in a persistent fashion using the
|
|
.Xr rc.conf 5
|
|
variables
|
|
.Va dumpdev
|
|
and
|
|
.Va dumpon_flags .
|
|
For more information on this usage, see
|
|
.Xr rc.conf 5 .
|
|
.Ss General options
|
|
.Bl -tag -width _k_pubkey
|
|
.It Fl k Ar pubkey
|
|
Configure encrypted kernel dumps.
|
|
.Pp
|
|
A random, one-time symmetric key is automatically generated for bulk kernel
|
|
dump encryption every time
|
|
.Nm
|
|
is used.
|
|
The provided
|
|
.Ar pubkey
|
|
is used to encrypt a copy of the symmetric key.
|
|
The encrypted dump contents consist of a standard dump header, the
|
|
pubkey-encrypted symmetric key contents, and the symmetric key encrypted core
|
|
dump contents.
|
|
.Pp
|
|
As a result, only someone with the corresponding private key can decrypt the symmetric key.
|
|
The symmetric key is necessary to decrypt the kernel core.
|
|
The goal of the mechanism is to provide confidentiality.
|
|
.Pp
|
|
The
|
|
.Va pubkey
|
|
file should be a PEM-formatted RSA key of at least 1024 bits.
|
|
.It Fl l
|
|
List the currently configured dump device, or /dev/null if no device is
|
|
configured.
|
|
.It Fl v
|
|
Enable verbose mode.
|
|
.It Fl Z
|
|
Enable compression (Zstandard).
|
|
.It Fl z
|
|
Enable compression (gzip).
|
|
Only one compression method may be enabled at a time, so
|
|
.Fl z
|
|
is incompatible with
|
|
.Fl Z .
|
|
.Pp
|
|
Zstandard provides superior compression ratio and performance.
|
|
.El
|
|
.Ss Netdump
|
|
.Nm
|
|
may also configure the kernel to dump to a remote
|
|
.Xr netdumpd 8
|
|
server.
|
|
(The
|
|
.Xr netdumpd 8
|
|
server is available in ports.)
|
|
.Xr netdump 4
|
|
eliminates the need to reserve space for crash dumps.
|
|
It is especially useful in diskless environments.
|
|
When
|
|
.Nm
|
|
is used to configure netdump, the
|
|
.Ar device
|
|
(or
|
|
.Ar iface )
|
|
parameter should specify a network interface (e.g.,
|
|
.Va igb1 ) .
|
|
The specified NIC must be up (online) to configure netdump.
|
|
.Pp
|
|
.Xr netdump 4
|
|
specific options include:
|
|
.Bl -tag -width _g_gateway
|
|
.It Fl c Ar client
|
|
The local IP address of the
|
|
.Xr netdump 4
|
|
client.
|
|
.It Fl g Ar gateway
|
|
The first-hop router between
|
|
.Ar client
|
|
and
|
|
.Ar server .
|
|
If the
|
|
.Fl g
|
|
option is not specified and the system has a default route, the default
|
|
router is used as the
|
|
.Xr netdump 4
|
|
gateway.
|
|
If the
|
|
.Fl g
|
|
option is not specified and the system does not have a default route,
|
|
.Ar server
|
|
is assumed to be on the same link as
|
|
.Ar client .
|
|
.It Fl s Ar server
|
|
The IP address of the
|
|
.Xr netdumpd 8
|
|
server.
|
|
.El
|
|
.Pp
|
|
All of these options can be specified in the
|
|
.Xr rc.conf 5
|
|
variable
|
|
.Va dumpon_flags .
|
|
.Ss Minidumps
|
|
The default type of kernel crash dump is the mini crash dump.
|
|
Mini crash dumps hold only memory pages in use by the kernel.
|
|
Alternatively, full memory dumps can be enabled by setting the
|
|
.Va debug.minidump
|
|
.Xr sysctl 8
|
|
variable to 0.
|
|
.Ss Full dumps
|
|
For systems using full memory dumps, the size of the specified dump
|
|
device must be at least the size of physical memory.
|
|
Even though an additional 64 kB header is added to the dump, the BIOS for a
|
|
platform typically holds back some memory, so it is not usually
|
|
necessary to size the dump device larger than the actual amount of RAM
|
|
available in the machine.
|
|
Also, when using full memory dumps, the
|
|
.Nm
|
|
utility will refuse to enable a dump device which is smaller than the
|
|
total amount of physical memory as reported by the
|
|
.Va hw.physmem
|
|
.Xr sysctl 8
|
|
variable.
|
|
.Sh IMPLEMENTATION NOTES
|
|
Because the file system layer is already dead by the time a crash dump
|
|
is taken, it is not possible to send crash dumps directly to a file.
|
|
.Pp
|
|
The
|
|
.Xr loader 8
|
|
variable
|
|
.Va dumpdev
|
|
may be used to enable early kernel core dumps for system panics which occur
|
|
before userspace starts.
|
|
.Sh EXAMPLES
|
|
In order to generate an RSA private key, a user can use the
|
|
.Xr genrsa 1
|
|
tool:
|
|
.Pp
|
|
.Dl # openssl genrsa -out private.pem 4096
|
|
.Pp
|
|
A public key can be extracted from the private key using the
|
|
.Xr rsa 1
|
|
tool:
|
|
.Pp
|
|
.Dl # openssl rsa -in private.pem -out public.pem -pubout
|
|
.Pp
|
|
Once the RSA keys are created in a safe place, the public key may be moved to
|
|
the untrusted netdump client machine.
|
|
Now
|
|
.Pa public.pem
|
|
can be used by
|
|
.Nm
|
|
to configure encrypted kernel crash dumps:
|
|
.Pp
|
|
.Dl # dumpon -k public.pem /dev/ada0s1b
|
|
.Pp
|
|
It is recommended to test if the kernel saves encrypted crash dumps using the
|
|
current configuration.
|
|
The easiest way to do that is to cause a kernel panic using the
|
|
.Xr ddb 4
|
|
debugger:
|
|
.Pp
|
|
.Dl # sysctl debug.kdb.panic=1
|
|
.Pp
|
|
In the debugger the following commands should be typed to write a core dump and
|
|
reboot:
|
|
.Pp
|
|
.Dl db> call doadump(0)
|
|
.Dl db> reset
|
|
.Pp
|
|
After reboot
|
|
.Xr savecore 8
|
|
should be able to save the core dump in the
|
|
.Va Dq dumpdir
|
|
directory, which is
|
|
.Pa /var/crash
|
|
by default:
|
|
.Pp
|
|
.Dl # savecore /dev/ada0s1b
|
|
.Pp
|
|
Three files should be created in the core directory:
|
|
.Pa info.# ,
|
|
.Pa key.#
|
|
and
|
|
.Pa vmcore_encrypted.#
|
|
(where
|
|
.Dq #
|
|
is the number of the last core dump saved by
|
|
.Xr savecore 8 ) .
|
|
The
|
|
.Pa vmcore_encrypted.#
|
|
can be decrypted using the
|
|
.Xr decryptcore 8
|
|
utility:
|
|
.Pp
|
|
.Dl # decryptcore -p private.pem -k key.# -e vmcore_encrypted.# -c vmcore.#
|
|
.Pp
|
|
or shorter:
|
|
.Pp
|
|
.Dl # decryptcore -p private.pem -n #
|
|
.Pp
|
|
The
|
|
.Pa vmcore.#
|
|
can be now examined using
|
|
.Xr kgdb 1 :
|
|
.Pp
|
|
.Dl # kgdb /boot/kernel/kernel vmcore.#
|
|
.Pp
|
|
or shorter:
|
|
.Pp
|
|
.Dl # kgdb -n #
|
|
.Pp
|
|
The core was decrypted properly if
|
|
.Xr kgdb 1
|
|
does not print any errors.
|
|
Note that the live kernel might be at a different path
|
|
which can be examined by looking at the
|
|
.Va kern.bootfile
|
|
.Xr sysctl 8 .
|
|
.Sh SEE ALSO
|
|
.Xr gzip 1 ,
|
|
.Xr kgdb 1 ,
|
|
.Xr zstd 1 ,
|
|
.Xr ddb 4 ,
|
|
.Xr netdump 4 ,
|
|
.Xr fstab 5 ,
|
|
.Xr rc.conf 5 ,
|
|
.Xr config 8 ,
|
|
.Xr decryptcore 8 ,
|
|
.Xr init 8 ,
|
|
.Xr loader 8 ,
|
|
.Xr rc 8 ,
|
|
.Xr savecore 8 ,
|
|
.Xr swapon 8 ,
|
|
.Xr panic 9
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
utility appeared in
|
|
.Fx 2.0.5 .
|
|
.Pp
|
|
Support for encrypted kernel core dumps and netdump was added in
|
|
.Fx 12.0 .
|
|
.Sh AUTHORS
|
|
The
|
|
.Nm
|
|
manual page was written by
|
|
.An Mark Johnston Aq Mt markj@FreeBSD.org ,
|
|
.An Conrad Meyer Aq Mt cem@FreeBSD.org ,
|
|
.An Konrad Witaszczyk Aq Mt def@FreeBSD.org ,
|
|
and countless others.
|
|
.Sh CAVEATS
|
|
To configure encrypted kernel core dumps, the running kernel must have been
|
|
compiled with the
|
|
.Dv EKCD
|
|
option.
|
|
.Pp
|
|
Netdump does not automatically update the configured
|
|
.Ar gateway
|
|
if routing topology changes.
|
|
.Pp
|
|
The size of a compressed dump or a minidump is not a fixed function of RAM
|
|
size.
|
|
Therefore, when at least one of these options is enabled, the
|
|
.Nm
|
|
utility cannot verify that the
|
|
.Ar device
|
|
has sufficient space for a dump.
|
|
.Nm
|
|
is also unable to verify that a configured
|
|
.Xr netdumpd 8
|
|
server has sufficient space for a dump.
|
|
.Pp
|
|
.Fl Z
|
|
requires a kernel compiled with the
|
|
.Dv ZSTDIO
|
|
kernel option.
|
|
Similarly,
|
|
.Fl z
|
|
requires the
|
|
.Dv GZIO
|
|
option.
|
|
.Sh BUGS
|
|
It is currently not possible to configure both compression and encryption.
|
|
The encrypted dump format assumes that the kernel dump size is a multiple
|
|
of the cipher block size, which may not be true when the dump is compressed.
|
|
.Pp
|
|
Netdump only supports IPv4 at this time.
|
|
.Sh SECURITY CONSIDERATIONS
|
|
The current encrypted kernel core dump scheme does not provide integrity nor
|
|
authentication.
|
|
That is, the recipient of an encrypted kernel core dump cannot know if they
|
|
received an intact core dump, nor can they verify the provenance of the dump.
|
|
.Pp
|
|
RSA keys smaller than 1024 bits are practical to factor and therefore weak.
|
|
Even 1024 bit keys may not be large enough to ensure privacy for many
|
|
years, so NIST recommends a minimum of 2048 bit RSA keys.
|
|
As a seatbelt,
|
|
.Nm
|
|
prevents users from configuring encrypted kernel dumps with extremely weak RSA
|
|
keys.
|
|
If you do not care for cryptographic privacy guarantees, just use
|
|
.Nm
|
|
without specifying a
|
|
.Fl k Ar pubkey
|
|
option.
|
|
.Pp
|
|
This process is sandboxed using
|
|
.Xr capsicum 4 .
|