287d467c5d
Generally, access to the kernel debugger is considered to be unsafe from a security perspective since it presents an unrestricted interface to inspect or modify the system state, including sensitive data such as signing keys. However, having some access to debugger functionality on production systems may be useful in determining the cause of a panic or hang. Therefore, it is desirable to have an optional policy which allows limited use of ddb(4) while disabling the functionality which could reveal system secrets. This loadable MAC module allows for the use of some ddb(4) commands while preventing the execution of others. The commands have been broadly grouped into three categories: - Those which are 'safe' and will not emit sensitive data (e.g. trace). Generally, these commands are deterministic and don't accept arguments. - Those which are definitively unsafe (e.g. examine <addr>, search <addr> <value>) - Commands which may be safe to execute depending on the arguments provided (e.g. show thread <addr>). Safe commands have been flagged as such with the DB_CMD_MEMSAFE flag. Commands requiring extra validation can provide a function to do so. For example, 'show thread <addr>' can be used as long as addr can be checked against the system's list of process structures. The policy also prevents debugger backends other than ddb(4) from executing, for example gdb(4). Reviewed by: markj, pauamma_gundo.com (manpages) Sponsored by: Juniper Networks, Inc. Sponsored by: Klara, Inc. Differential Revision: https://reviews.freebsd.org/D35371
170 lines
4.1 KiB
Groff
170 lines
4.1 KiB
Groff
.\"-
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.\" Copyright (c) 2007-2008 Robert N. M. Watson
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd December 24, 2008
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.Dt DDB 8
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.Os
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.Sh NAME
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.Nm ddb
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.Nd "configure DDB kernel debugger properties"
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.Sh SYNOPSIS
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.Nm
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.Cm capture
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.Op Fl M core
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.Op Fl N system
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.Cm print
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.Nm
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.Cm capture
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.Op Fl M core
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.Op Fl N system
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.Cm status
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.Nm
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.Cm script
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.Ar scriptname
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.Nm
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.Cm script
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.Ar scriptname Ns = Ns Ar script
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.Nm
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.Cm scripts
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.Nm
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.Cm unscript
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.Ar scriptname
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.Nm
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.Ar pathname
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.Sh DESCRIPTION
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The
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.Nm
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utility configures certain aspects of the
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.Xr ddb 4
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kernel debugger from user space that are not configured at compile-time or
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easily via
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.Xr sysctl 8
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MIB entries.
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.Pp
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To ease configuration, commands can be put in a file which is processed using
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.Nm
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as shown in the last synopsis line.
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An absolute
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.Ar pathname
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must be used.
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The file will be read line by line and applied as arguments to the
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.Nm
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utility.
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Whitespace at the beginning of lines will be ignored as will lines where the
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first non-whitespace character is
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.Ql # .
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.Sh OUTPUT CAPTURE
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The
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.Nm
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utility can be used to extract the contents of the
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.Xr ddb 4
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output capture buffer of the current live kernel, or from the crash dump of a
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kernel on disk.
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The following debugger commands are available from the command line:
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.Bl -tag -width indent
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.It Xo
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.Cm capture
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.Op Fl M Ar core
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.Op Fl N Ar system
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.Cm print
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.Xc
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Print the current contents of the
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.Xr ddb 4
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output capture buffer.
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.It Xo
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.Cm capture
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.Op Fl M Ar core
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.Op Fl N Ar system
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.Cm status
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.Xc
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Print the current status of the
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.Xr ddb 4
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output capture buffer.
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.El
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.Sh SCRIPTING
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The
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.Nm
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utility can be used to configure aspects of
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.Xr ddb 4
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scripting from user space; scripting support is described in more detail in
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.Xr ddb 4 .
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Each of the debugger commands is available from the command line:
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.Bl -tag -width indent
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.It Cm script Ar scriptname
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Print the script named
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.Ar scriptname .
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.It Cm script Ar scriptname Ns = Ns Ar script
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Define a script named
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.Ar scriptname .
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As many scripts contain characters interpreted in special ways by the shell,
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it is advisable to enclose
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.Ar script
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in quotes.
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.It Cm scripts
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List currently defined scripts.
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.It Cm unscript Ar scriptname
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Delete the script named
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.Ar scriptname .
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.El
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.Sh EXIT STATUS
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.Ex -std
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.Sh EXAMPLES
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The following example defines a script that will execute when the kernel
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debugger is entered as a result of a break signal:
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.Bd -literal -offset indent
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ddb script kdb.enter.break="show pcpu; bt"
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.Ed
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.Pp
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The following example will delete the script:
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.Pp
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.Dl "ddb unscript kdb.enter.break"
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.Pp
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For further examples, see the
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.Xr ddb 4
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and
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.Xr textdump 4
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manual pages.
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.Sh SEE ALSO
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.Xr ddb 4 ,
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.Xr mac_ddb 4 ,
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.Xr textdump 4 ,
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.Xr sysctl 8
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.Sh HISTORY
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The
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.Nm
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utility first appeared in
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.Fx 7.1 .
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.Sh AUTHORS
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.An Robert N M Watson
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.Sh BUGS
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Ideally,
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.Nm
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would not exist, as all pertinent aspects of
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.Xr ddb 4
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could be configured directly via
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.Xr sysctl 8 .
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