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List: kde-panel-devel
Subject: Re: Review Request 126203: Disable ptrace for kcheckpass and the greeter
From: "Raphael Kubo da Costa" <rakuco () FreeBSD ! org>
Date: 2015-11-30 16:02:11
Message-ID: 20151130160211.9081.49691 () mimi ! kde ! org
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> On Nov. 30, 2015, 10:34 a.m., Tobias Berner wrote:
> > I think FreeBSD 10 introduced a similar interface in r277322
> > https://svnweb.freebsd.org/base?view=revision&revision=277322
> > Though it is explicitely stated to not be a "security feature".
> >
> > According to the man page of progctl
> > https://www.freebsd.org/cgi/man.cgi?query=procctl&apropos=0&sektion=2&manpath=FreeBSD+10.2-RELEASE&arch=default&format=html
> > this would be PROC_TRACE_CTL with data PROC_TRACE_CTL_DISABLE.
> >
> >
> > I will have to ask someone more familiar with that.
>
> Martin Gräßlin wrote:
> > how do I get kwin to output the debug output for the framebuffer backend, with \
> > qcdebug lines,
>
> Given the notes on it, that seems fine. It's not my intention to protect against \
> kernel or root.
> Raphael Kubo da Costa wrote:
> From a non-Linux perspective, it would be good if there was a CMake check for \
> `prctl()` and `PR_SET_DUMPABLE/PROC_TRACE_CTL` with a big warning in case none was \
> found. The oldest supported FreeBSD release (9.x) will be supported until the end \
> of 2016 and it does not have this functionality, and neither do \
> {Net,DragonFly,Open}BSD, so adding the calls without additional checks will just \
> create additional problems for those packaging kscreenlocker for those platforms, \
> and I doubt they will be able to add a replacement for this without help from their \
> kernel (and existing releases would still be broken).
> Martin Gräßlin wrote:
> The CMake check seems like a good idea to me - this also allows to make a nice \
> HAVE_PRCTL_DUMPABABLE flag which I would prefer over QOSLINUX or something like \
> that. Anybody know how to write such a check? I assume trying to compile and check \
> whether it compiles?
I think so. Something like this (untested):
```
include(CheckIncludeFile)
include(CheckSymbolExists)
check_include_file("sys/prctl.h" HAVE_SYS_PRCTL_H)
check_symbol_exists(PR_SET_DUMPABLE "sys/prctl.h" HAVE_PR_SET_DUMPABLE)
check_include_file("sys/procctl.h" HAVE_SYS_PROCCTL_H)
check_symbol_exists(PROC_TRACE_CTL "sys/procctl.h" HAVE_PROC_TRACE_CTL)
if (NOT HAVE_PR_SET_DUMPABLE OR NOT HAVE_PROC_TRACE_CTL)
message(WARNING "Support for disabling ptrace(2) and core dumps via prctl/procctl \
is not available. <scary message here>.") endif ()
configure_file(...)
```
It's unfortunate that the naming could not be standardized, as now one needs to check \
for those macros and call different functions with different arguments depending on \
their values.
- Raphael
-----------------------------------------------------------
This is an automatically generated e-mail. To reply, visit:
https://git.reviewboard.kde.org/r/126203/#review88939
-----------------------------------------------------------
On Nov. 30, 2015, 10:01 a.m., Martin Gräßlin wrote:
>
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://git.reviewboard.kde.org/r/126203/
> -----------------------------------------------------------
>
> (Updated Nov. 30, 2015, 10:01 a.m.)
>
>
> Review request for Plasma and Tobias Berner.
>
>
> Repository: kscreenlocker
>
>
> Description
> -------
>
> Setting the PR_SET_DUMPABLE flag to 0 for the security relevant
> command kcheckpass and kscreenlocker_greet. If one wants to gdb into
> the running command it will result in:
>
> ptrace: Operation not permitted.
>
> For kscreenlocker_greet ptrace is permitted in testing mode.
>
> As root it's still possible to attach to the process.
>
> ---
>
> @Tobias: I assume this is a strong linux-ism. Is there a FreeBSD compareable \
> functionality?
> I'm considering to push this explicitly without an ifdef. It's a new security \
> feature and I want to make non-Linux systems aware of the fact that it adds a new \
> feature and that a replacement should be added.
>
> Diffs
> -----
>
> greeter/main.cpp e4e679e7ef40b319665428281fdba5f4e0b4eb25
> kcheckpass/kcheckpass.c fd2d2215bf2199f159a121bb0ce08e7b2b254aaa
>
> Diff: https://git.reviewboard.kde.org/r/126203/diff/
>
>
> Testing
> -------
>
> Tried to gdb into the processes: failed
> Tried to gdb into kscreenlocker_greet --testing: succeeded
> Tried to gdb into kscreenlocker_greet as root: succeeded
>
>
> Thanks,
>
> Martin Gräßlin
>
>
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This is an automatically generated e-mail. To reply, visit:
<a href="https://git.reviewboard.kde.org/r/126203/">https://git.reviewboard.kde.org/r/126203/</a>
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<br />
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: \
10px;"> <p style="margin-top: 0;">On November 30th, 2015, 10:34 a.m. EET, <b>Tobias \
Berner</b> wrote:</p> <blockquote style="margin-left: 1em; border-left: 2px solid \
#d0d0d0; padding-left: 10px;"> <pre style="white-space: pre-wrap; white-space: \
-moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: \
break-word;"><p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">I think FreeBSD 10 introduced a similar interface in \
r277322 https://svnweb.freebsd.org/base?view=revision&revision=277322
Though it is explicitely stated to not be a "security feature".</p>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">According to the man page of progctl \
https://www.freebsd.org/cgi/man.cgi?query=procctl&apropos=0&sektion=2&manpath=FreeBSD+10.2-RELEASE&arch=default&format=html
this would be PROC_TRACE_CTL with data PROC_TRACE_CTL_DISABLE.</p>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">I will have to ask someone more familiar with \
that.</p></pre> </blockquote>
<p>On November 30th, 2015, 10:43 a.m. EET, <b>Martin Gräßlin</b> wrote:</p>
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: \
10px;"> <pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: \
-pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;"><blockquote \
style="text-rendering: inherit;padding: 0 0 0 1em;border-left: 1px solid \
#bbb;white-space: normal;margin: 0 0 0 0.5em;line-height: inherit;"> <p \
style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: \
inherit;">how do I get kwin to output the debug output for the framebuffer backend, \
with qcdebug lines,</p> </blockquote>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">Given the notes on it, that seems fine. It's not my \
intention to protect against kernel or root.</p></pre> </blockquote>
<p>On November 30th, 2015, 12:22 p.m. EET, <b>Raphael Kubo da Costa</b> wrote:</p>
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: \
10px;"> <pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: \
-pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;"><p style="padding: \
0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">From \
a non-Linux perspective, it would be good if there was a CMake check for <code \
style="text-rendering: inherit;color: #4444cc;padding: 0;white-space: normal;margin: \
0;line-height: inherit;">prctl()</code> and <code style="text-rendering: \
inherit;color: #4444cc;padding: 0;white-space: normal;margin: 0;line-height: \
inherit;">PR_SET_DUMPABLE/PROC_TRACE_CTL</code> with a big warning in case none was \
found. The oldest supported FreeBSD release (9.x) will be supported until the end of \
2016 and it does not have this functionality, and neither do {Net,DragonFly,Open}BSD, \
so adding the calls without additional checks will just create additional problems \
for those packaging kscreenlocker for those platforms, and I doubt they will be able \
to add a replaceme nt for this without help from their kernel (and existing releases \
would still be broken).</p></pre> </blockquote>
<p>On November 30th, 2015, 5:41 p.m. EET, <b>Martin Gräßlin</b> wrote:</p>
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: \
10px;"> <pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: \
-pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;"><p style="padding: \
0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">The \
CMake check seems like a good idea to me - this also allows to make a nice \
HAVE_PRCTL_DUMPABABLE flag which I would prefer over QOSLINUX or something like that. \
Anybody know how to write such a check? I assume trying to compile and check whether \
it compiles?</p></pre> </blockquote>
</blockquote>
<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: \
-pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;"><p style="padding: \
0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">I \
think so. Something like this (untested):</p> <p style="padding: 0;text-rendering: \
inherit;margin: 0;line-height: inherit;white-space: inherit;"><div class="codehilite" \
style="background: #f8f8f8"><pre style="line-height: 125%">include(CheckIncludeFile) \
include(CheckSymbolExists)
check_include_file("sys/prctl.h" HAVE_SYS_PRCTL_H)
check_symbol_exists(PR_SET_DUMPABLE "sys/prctl.h" HAVE_PR_SET_DUMPABLE)
check_include_file("sys/procctl.h" HAVE_SYS_PROCCTL_H)
check_symbol_exists(PROC_TRACE_CTL "sys/procctl.h" HAVE_PROC_TRACE_CTL)
if (NOT HAVE_PR_SET_DUMPABLE OR NOT HAVE_PROC_TRACE_CTL)
message(WARNING "Support for disabling ptrace(2) and core dumps via \
prctl/procctl is not available. <scary message here>.") endif ()
configure_file(...)
</pre></div>
</p>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">It's unfortunate that the naming could not be \
standardized, as now one needs to check for those macros and call different functions \
with different arguments depending on their values.</p></pre> <br />
<p>- Raphael</p>
<br />
<p>On November 30th, 2015, 10:01 a.m. EET, Martin Gräßlin wrote:</p>
<table bgcolor="#fefadf" width="100%" cellspacing="0" cellpadding="12" style="border: \
1px #888a85 solid; border-radius: 6px; -moz-border-radius: 6px; \
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<td>
<div>Review request for Plasma and Tobias Berner.</div>
<div>By Martin Gräßlin.</div>
<p style="color: grey;"><i>Updated Nov. 30, 2015, 10:01 a.m.</i></p>
<div style="margin-top: 1.5em;">
<b style="color: #575012; font-size: 10pt;">Repository: </b>
kscreenlocker
</div>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Description </h1>
<table width="100%" bgcolor="#ffffff" cellspacing="0" cellpadding="10" \
style="border: 1px solid #b8b5a0"> <tr>
<td>
<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: \
-moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: \
break-word;"><p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">Setting the PR_SET_DUMPABLE flag to 0 for the security \
relevant command kcheckpass and kscreenlocker_greet. If one wants to gdb into
the running command it will result in:</p>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">ptrace: Operation not permitted.</p> <p \
style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: \
inherit;">For kscreenlocker_greet ptrace is permitted in testing mode.</p> <p \
style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: \
inherit;">As root it's still possible to attach to the process.</p> <hr \
style="text-rendering: inherit;margin: 0;padding: 0;white-space: normal;border: 1px \
solid #ddd;line-height: inherit;" /> <p style="padding: 0;text-rendering: \
inherit;margin: 0;line-height: inherit;white-space: inherit;">@Tobias: I assume this \
is a strong linux-ism. Is there a FreeBSD compareable functionality?</p> <p \
style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: \
inherit;">I'm considering to push this explicitly without an ifdef. It's a new \
security feature and I want to make non-Linux systems aware of the fact that it adds \
a new feature and that a replacement should be added.</p></pre> </td>
</tr>
</table>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Testing </h1>
<table width="100%" bgcolor="#ffffff" cellspacing="0" cellpadding="10" style="border: \
1px solid #b8b5a0"> <tr>
<td>
<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: \
-moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: \
break-word;"><p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">Tried to gdb into the processes: failed Tried to gdb \
into kscreenlocker_greet --testing: succeeded Tried to gdb into kscreenlocker_greet \
as root: succeeded</p></pre> </td>
</tr>
</table>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Diffs</b> </h1>
<ul style="margin-left: 3em; padding-left: 0;">
<li>greeter/main.cpp <span style="color: \
grey">(e4e679e7ef40b319665428281fdba5f4e0b4eb25)</span></li>
<li>kcheckpass/kcheckpass.c <span style="color: \
grey">(fd2d2215bf2199f159a121bb0ce08e7b2b254aaa)</span></li>
</ul>
<p><a href="https://git.reviewboard.kde.org/r/126203/diff/" style="margin-left: \
3em;">View Diff</a></p>
</td>
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