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List: asterisk-dev
Subject: Re: [asterisk-dev] [Code Review] 2783: Fix SIP/TLS reading - random connection drop
From: "David Lee" <reviewboard () asterisk ! org>
Date: 2013-08-29 20:25:58
Message-ID: 20130829202558.23400.37328 () hotblack ! digium ! com
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https://reviewboard.asterisk.org/r/2783/#review9562
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If you can get your hands on a copy of "Network Security with
OpenSSL"[1], check out the section on non-blocking I/O (somewhere in the
depths of Chapter 5 in my edition).
[1]: http://shop.oreilly.com/product/9780596002701.do
/trunk/main/tcptls.c
<https://reviewboard.asterisk.org/r/2783/#comment18678>
Maybe it happens less often, but ssl_write would have the same problem.
/trunk/main/tcptls.c
<https://reviewboard.asterisk.org/r/2783/#comment18676>
An SSL_read() may, ironically, fail with an SSL_ERROR_WANT_WRITE. A
read may require a renegotiation, which can happen at any time.
/trunk/main/tcptls.c
<https://reviewboard.asterisk.org/r/2783/#comment18677>
This has the possibility of turning what's normally a non-blocking
read into a blocking read. I have no idea what the broader
implications of that might be, if any.
- David Lee
On Aug. 21, 2013, 3:24 p.m., Tzafrir Cohen wrote:
>
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviewboard.asterisk.org/r/2783/
> -----------------------------------------------------------
>
> (Updated Aug. 21, 2013, 3:24 p.m.)
>
>
> Review request for Asterisk Developers.
>
>
> Bugs: ASTERISK-18345
> https://issues.asterisk.org/jira/browse/ASTERISK-18345
>
>
> Repository: Asterisk
>
>
> Description
> -------
>
> Symptom: Asterisk drops a SIP/TLS connection: debugging reports that it has failed \
> to read it.
> I can reproduce this on my system when the TLS client is Asterisk 11.5 (installed \
> from the Debian package) set with 'allow=all' to get a long list of codecs.
> Calling ast_wait_for_input before every fgets is not sufficient.
> Function fgets internally calls read (=> SSL_read) until either "\n" or
> eof is found. And because the socket is polled only before the first
> SSL_read call, consequent calls can fail and return <=0 even though the
> data are on the way.
>
> This is fixed by adding a read() loop inside the ssl_read() hook.
>
> I came accross this patch today and it looks like it fixes my problem (see my \
> comment at the end). The patch I used is by Filip Jenicek. See the bug report for \
> the full log.
>
> Diffs
> -----
>
> /trunk/main/tcptls.c 397346
>
> Diff: https://reviewboard.asterisk.org/r/2783/diff/
>
>
> Testing
> -------
>
> Work on trunk.
>
>
> Thanks,
>
> Tzafrir Cohen
>
>
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This is an automatically generated e-mail. To reply, visit:
<a href="https://reviewboard.asterisk.org/r/2783/">https://reviewboard.asterisk.org/r/2783/</a>
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<br />
<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: \
-pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">If you can get your \
hands on a copy of "Network Security with OpenSSL"[1], check out the \
section on non-blocking I/O (somewhere in the depths of Chapter 5 in my edition).
[1]: http://shop.oreilly.com/product/9780596002701.do</pre>
<br />
<div>
<table width="100%" border="0" bgcolor="white" style="border: 1px solid #C0C0C0; \
border-collapse: collapse; margin: 2px padding: 2px;"> <thead>
<tr>
<th colspan="4" bgcolor="#F0F0F0" style="border-bottom: 1px solid #C0C0C0; \
font-size: 9pt; padding: 4px 8px; text-align: left;"> <a \
href="https://reviewboard.asterisk.org/r/2783/diff/1/?file=44334#file44334line59" \
style="color: black; font-weight: bold; text-decoration: \
underline;">/trunk/main/tcptls.c</a> <span style="font-weight: normal;">
(Diff revision 1)
</span>
</th>
</tr>
</thead>
<tbody style="background-color: #e4d9cb; padding: 4px 8px; text-align: center;">
<tr>
<td colspan="4"><pre style="font-size: 8pt; line-height: 140%; margin: 0; \
">ASTERISK_FILE_VERSION(__FILE__, "$Revision$")</pre></td>
</tr>
</tbody>
<tbody>
<tr>
<th bgcolor="#f0f0f0" style="border-right: 1px solid #C0C0C0;" \
align="right"><font size="2">59</font></th> <td bgcolor="#ffffff" width="50%"><pre \
style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="k">static</span> \
<span class="n">HOOK_T</span> <span class="n">ssl_read</span><span \
class="p">(</span><span class="kt">void</span> <span class="o">*</span><span \
class="n">cookie</span><span class="p">,</span> <span class="kt">char</span> <span \
class="o">*</span><span class="n">buf</span><span class="p">,</span> <span \
class="n">LEN_T</span> <span class="n">len</span><span class="p">)</span></pre></td> \
<th bgcolor="#f0f0f0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid \
#C0C0C0;" align="right"><font size="2">59</font></th> <td bgcolor="#ffffff" \
width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span \
class="k">static</span> <span class="n">HOOK_T</span> <span \
class="n">ssl_read</span><span class="p">(</span><span class="kt">void</span> <span \
class="o">*</span><span class="n">cookie</span><span class="p">,</span> <span \
class="kt">char</span> <span class="o">*</span><span class="n">buf</span><span \
class="p">,</span> <span class="n">LEN_T</span> <span class="n">len</span><span \
class="p">)</span></pre></td> </tr>
</tbody>
</table>
<pre style="margin-left: 2em; white-space: pre-wrap; white-space: -moz-pre-wrap; \
white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">Maybe it \
happens less often, but ssl_write would have the same problem.</pre> </div>
<br />
<div>
<table width="100%" border="0" bgcolor="white" style="border: 1px solid #C0C0C0; \
border-collapse: collapse; margin: 2px padding: 2px;"> <thead>
<tr>
<th colspan="4" bgcolor="#F0F0F0" style="border-bottom: 1px solid #C0C0C0; \
font-size: 9pt; padding: 4px 8px; text-align: left;"> <a \
href="https://reviewboard.asterisk.org/r/2783/diff/1/?file=44334#file44334line64" \
style="color: black; font-weight: bold; text-decoration: \
underline;">/trunk/main/tcptls.c</a> <span style="font-weight: normal;">
(Diff revision 1)
</span>
</th>
</tr>
</thead>
<tbody style="background-color: #e4d9cb; padding: 4px 8px; text-align: center;">
<tr>
<td colspan="4"><pre style="font-size: 8pt; line-height: 140%; margin: 0; \
">ASTERISK_FILE_VERSION(__FILE__, "$Revision$")</pre></td>
</tr>
</tbody>
<tbody>
<tr>
<th bgcolor="#b1ebb0" style="border-right: 1px solid #C0C0C0;" \
align="right"><font size="2"></font></th> <td bgcolor="#c5ffc4" width="50%"><pre \
style="font-size: 8pt; line-height: 140%; margin: 0; "></pre></td> <th \
bgcolor="#b1ebb0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid \
#C0C0C0;" align="right"><font size="2">64</font></th> <td bgcolor="#c5ffc4" \
width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span \
class="tb"> </span><span class="k">while</span> <span class="p">(</span><span \
class="n">i</span> <span class="o"><</span> <span class="mi">0</span> <span \
class="o">&&</span> <span class="n">SSL_get_error</span><span \
class="p">(</span><span class="n">cookie</span><span class="p">,</span> <span \
class="n">i</span><span class="p">)</span> <span class="o">==</span> <span \
class="n">SSL_ERROR_WANT_READ</span><span class="p">)</span> <span \
class="p">{</span></pre></td> </tr>
</tbody>
</table>
<pre style="margin-left: 2em; white-space: pre-wrap; white-space: -moz-pre-wrap; \
white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">An \
SSL_read() may, ironically, fail with an SSL_ERROR_WANT_WRITE. A read may require a \
renegotiation, which can happen at any time.</pre> </div>
<br />
<div>
<table width="100%" border="0" bgcolor="white" style="border: 1px solid #C0C0C0; \
border-collapse: collapse; margin: 2px padding: 2px;"> <thead>
<tr>
<th colspan="4" bgcolor="#F0F0F0" style="border-bottom: 1px solid #C0C0C0; \
font-size: 9pt; padding: 4px 8px; text-align: left;"> <a \
href="https://reviewboard.asterisk.org/r/2783/diff/1/?file=44334#file44334line66" \
style="color: black; font-weight: bold; text-decoration: \
underline;">/trunk/main/tcptls.c</a> <span style="font-weight: normal;">
(Diff revision 1)
</span>
</th>
</tr>
</thead>
<tbody style="background-color: #e4d9cb; padding: 4px 8px; text-align: center;">
<tr>
<td colspan="4"><pre style="font-size: 8pt; line-height: 140%; margin: 0; \
">ASTERISK_FILE_VERSION(__FILE__, "$Revision$")</pre></td>
</tr>
</tbody>
<tbody>
<tr>
<th bgcolor="#b1ebb0" style="border-right: 1px solid #C0C0C0;" \
align="right"><font size="2"></font></th> <td bgcolor="#c5ffc4" width="50%"><pre \
style="font-size: 8pt; line-height: 140%; margin: 0; "></pre></td> <th \
bgcolor="#b1ebb0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid \
#C0C0C0;" align="right"><font size="2">66</font></th> <td bgcolor="#c5ffc4" \
width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span \
class="tb"> </span><span class="tb"> </span><span class="k">if</span> <span \
class="p">(</span><span class="n">ast_wait_for_input</span><span \
class="p">(</span><span class="n">SSL_get_fd</span><span class="p">(</span><span \
class="n">cookie</span><span class="p">),</span> <span class="mi">5000</span><span \
class="p">)</span> <span class="o"><=</span> <span class="mi">0</span><span \
class="p">)</span> <span class="k">return</span> <span class="mi">0</span><span \
class="p">;</span></pre></td> </tr>
</tbody>
</table>
<pre style="margin-left: 2em; white-space: pre-wrap; white-space: -moz-pre-wrap; \
white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">This has \
the possibility of turning what's normally a non-blocking read into a blocking \
read. I have no idea what the broader implications of that might be, if any.</pre>
</div>
<br />
<p>- David</p>
<br />
<p>On August 21st, 2013, 3:24 p.m. CDT, Tzafrir Cohen wrote:</p>
<table bgcolor="#fefadf" width="100%" cellspacing="0" cellpadding="8" \
style="background-image: \
url('https://reviewboard.asterisk.org/static/rb/images/review_request_box_top_bg.png'); \
background-position: left top; background-repeat: repeat-x; border: 1px black \
solid;"> <tr>
<td>
<div>Review request for Asterisk Developers.</div>
<div>By Tzafrir Cohen.</div>
<p style="color: grey;"><i>Updated Aug. 21, 2013, 3:24 p.m.</i></p>
<div style="margin-top: 1.5em;">
<b style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Bugs: </b>
<a href="https://issues.asterisk.org/jira/browse/ASTERISK-18345">ASTERISK-18345</a>
</div>
<div style="margin-top: 1.5em;">
<b style="color: #575012; font-size: 10pt;">Repository: </b>
Asterisk
</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;">Symptom: Asterisk drops a SIP/TLS connection: debugging reports that it \
has failed to read it.
I can reproduce this on my system when the TLS client is Asterisk 11.5 (installed \
from the Debian package) set with 'allow=all' to get a long list of codecs.
Calling ast_wait_for_input before every fgets is not sufficient.
Function fgets internally calls read (=> SSL_read) until either "\n" or
eof is found. And because the socket is polled only before the first
SSL_read call, consequent calls can fail and return <=0 even though the
data are on the way.
This is fixed by adding a read() loop inside the ssl_read() hook.
I came accross this patch today and it looks like it fixes my problem (see my comment \
at the end). The patch I used is by Filip Jenicek. See the bug report for the full \
log.</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;">Work on trunk.</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>/trunk/main/tcptls.c <span style="color: grey">(397346)</span></li>
</ul>
<p><a href="https://reviewboard.asterisk.org/r/2783/diff/" style="margin-left: \
3em;">View Diff</a></p>
</td>
</tr>
</table>
</div>
</body>
</html>
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