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<div style="font-size:10.0pt;font-family:Verdana,Arial">Bron, do
you mean Sieve is separated from the rest of the Cyrus code or
that inside Sieve code there's separation for pure data
processing (without syscalls) and I/O & other resources
handling, processes/threads management, etc.? I my previous mail
I was meaning the later.<br>
<br>
If it's already done, that's great and everything is ready to
define the format for the "results" file and proceed with the
seccomp implementation, if all agree that this is a needed
change.<br>
<br>
</div>
<div style="border:none;border-top:solid #B5C4DF
1.0pt;padding:3.0pt 0cm 0cm
0cm;font-size:10.0pt;font-family:"Tahoma","sans-serif""><b>From:</b>
Bron Gondwana Via Cyrus-devel<br>
<b>Sent:</b> Tuesday, February 07, 2017 07:01<br>
<b>To:</b> Cyrus-devel<br>
<b>Subject:</b> Re: Cyrus Sieve futures<br>
</div>
<br>
</div>
<title></title>
<div style="font-family:Arial;">Actually, that's pretty much already
done, the separation. Sieve, more than any other part of the
Cyrus code, is very decoupled. It used to be a separate CVS
repository once upon a time.<br>
</div>
<div style="font-family:Arial;"><br>
Bron.<br>
</div>
<div><br>
</div>
<div><br>
</div>
<div>On Tue, 7 Feb 2017, at 18:36, Anatoli via Cyrus-devel wrote:<br>
</div>
<blockquote type="cite">
<div>
<div style="font-size:10pt;font-family:Verdana,Arial;">
<div style="font-family:Arial;">Hi Ken,<br>
</div>
<div style="font-family:Arial;"> <br>
</div>
<div style="font-family:Arial;"> I don't have any special uses
for Sieve apart from the most basic ones, but I would like
to ask you if you see it feasible, as part of this work, to
separate the "numbers crunching" (e.g. rules matching,
transformations, etc.) code from the I/O code (that is
responsible for manipulating files, communicating with other
processes, etc.)?<br>
</div>
<div style="font-family:Arial;"> <br>
</div>
<div style="font-family:Arial;"> My idea is to isolate and
safeguard Sieve's "numbers crunching" code <a
moz-do-not-send="true"
href="https://en.wikipedia.org/wiki/Seccomp">with</a> <a
moz-do-not-send="true"
href="http://man7.org/linux/man-pages/man2/seccomp.2.html">seccomp</a>,
which basically only allows to execute userland code (i.e.
no syscalls, etc.) and read/write to already-open file
descriptors. This should reduce currently broad attack
surface to some really exotic bugs in the Linux kernel (up
to now just one significant bug for strict seccomp bypass
was discovered (CVE-2009-0835 in 2.6 kernel 8 years ago),
soon after this functionality was implemented).<br>
</div>
<div style="font-family:Arial;"> <br>
</div>
<div style="font-family:Arial;"> One of possible architectures
could be described this way (similar to <a
moz-do-not-send="true"
href="http://www.postfix.org/OVERVIEW.html">Postfix
architecture</a>):<br>
</div>
<div style="font-family:Arial;"> <br>
</div>
<ol>
<li>Sieve daemon receives an incoming data for processing
and stores it in a memory buffer (without touching it)<br>
</li>
<li>It creates a new "results" file and opens it for writing<br>
</li>
<li>It forks a process<br>
</li>
<li>The newly created child process switches to seccomp<br>
</li>
<li>It processes the data and writes the results (in a
special format) to the "results" file, then exits<br>
</li>
<li>Sieve daemon detects the exit of the child process and
reads the "results" file to perform the requested actions,
then deletes the file<br>
</li>
<li>If the child is killed (as the result of seccomp
restrictions violation) or something is wrong with the
format of the "results" file, Sieve daemon quarantines the
data and writes an error to the logs<br>
</li>
</ol>
<div style="font-family:Arial;"><br>
</div>
<div style="font-family:Arial;">The format for the "results"
file should be simple and well defined, and the code to
interpret it should be carefully written. This could be
started as a mere adaptation for the new architecture of the
current actions processing logic and be progressively
improved later. This would be much easier than making the
entire Sieve code base and the libraries it uses (e.g. PCRE)
reasonably safe (PCRE alone is a huge bag of<a
moz-do-not-send="true"
href="https://web.nvd.nist.gov/view/vuln/search-results?query=pcre&search_type=all&cves=on">vulnerabilities</a>,
including lots of RCEs).<br>
</div>
<div style="font-family:Arial;"> <br>
</div>
<div style="font-family:Arial;"> <br>
</div>
<div style="font-family:Arial;"> Another question (just
wondering if it's in your (or other devs) plans and its
feasibility): is it practically possible to implement for
Sieve something like "run the rules on X folder (+
subfolders)" same way as local rules in most MUAs could be
applied to already stored mails? I find lack of this feature
as the only (but notable) downside to Sieve vs local rules.<br>
</div>
<div style="font-family:Arial;"> <br>
</div>
<div style="font-family:Arial;"> Regards,<br>
</div>
<div style="font-family:Arial;"> Anatoli<br>
</div>
<div style="font-family:Arial;"> <br>
</div>
</div>
<div
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<div style="font-family:Arial;"><b>From:</b> Ken Murchison Via
Cyrus-devel<br>
</div>
<div style="font-family:Arial;"> <b>Sent:</b> Monday,
February 06, 2017 19:34<br>
</div>
<div style="font-family:Arial;"> <b>To:</b> Cyrus-devel<br>
</div>
<div style="font-family:Arial;"> <b>Subject:</b> Cyrus Sieve
futures<br>
</div>
</div>
</div>
<blockquote type="cite">
<div style="font-family:Arial;">All, <br>
</div>
<div style="font-family:Arial;"> <br>
</div>
<div style="font-family:Arial;"> I'm in the process of rewriting
the Sieve parser and adding new extensions for what will
become part of Cyrus v3.1. We currently support deprecated
and non-standardized extensions "imapflags" (standardized as
"imap4flags) and "notify" (standardized as "enotify"). I'd
like to rip out the parser and bytecode generator for these
extensions, and leave just the bytecode executing code for the
deprecated actions "mark", "unmark", and "denotify". <br>
</div>
<div style="font-family:Arial;"> <br>
</div>
<div style="font-family:Arial;"> Any existing scripts using
these actions (or the older "notify" syntax) would continue to
run. New/updated scripts would have to switch to using the
updated "notify" syntax and replace "mark" and "unmark" with
"setflag"/"addflag" and "removeflag". Does anyone have an
issue with these changes? <br>
</div>
<div style="font-family:Arial;"> <br>
</div>
<div style="font-family:Arial;"> Does anyone have any requests
for standard extensions that we don't currently support? Note
that "variables", "mailbox" and "*metadata" will be in Cyrus
3.0 and "ereject", "editheader", and "extlists" are already in
what will be the 3.1 branch. <br>
</div>
<div style="font-family:Arial;"> <br>
</div>
<div style="font-family:Arial;"> Extensions that I'm looking at
implementing (pretty much because they are low-hanging fruit)
are "duplicate", "environment", and "ihave". I may also look
at "replace" and "extracttext" which would be useful if we add
handling of calendar events to Sieve. <br>
</div>
<div style="font-family:Arial;"> <br>
</div>
</blockquote>
</blockquote>
<div style="font-family:Arial;"><br>
</div>
<div id="sig567075">
<div class="signature">--<br>
</div>
<div class="signature"> Bron Gondwana<br>
</div>
<div class="signature"> <a class="moz-txt-link-abbreviated" href="mailto:brong@fastmail.fm">brong@fastmail.fm</a><br>
</div>
<div class="signature"><br>
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