Fix CVE-2017-7853:

https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-7853
https://savannah.gnu.org/support/index.php?109265

Patch copied from upstream source repository:

https://git.savannah.gnu.org/cgit/osip.git/commit/?id=1ae06daf3b2375c34af23083394a6f010be24a45

From 1ae06daf3b2375c34af23083394a6f010be24a45 Mon Sep 17 00:00:00 2001
From: Aymeric Moizard <amoizard@gmail.com>
Date: Tue, 21 Feb 2017 17:16:26 +0100
Subject: [PATCH]  * fix bug report: sr #109265: SIP message body length
 underflow in libosip2-4.1.0    https://savannah.gnu.org/support/?109265   
 also applicable to current latest version

---
 src/osipparser2/osip_message_parse.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/osipparser2/osip_message_parse.c b/src/osipparser2/osip_message_parse.c
index 1628c60..aa35446 100644
--- a/src/osipparser2/osip_message_parse.c
+++ b/src/osipparser2/osip_message_parse.c
@@ -784,6 +784,12 @@ msg_osip_body_parse (osip_message_t * sip, const char *start_of_buf, const char
     if ('\n' == start_of_body[0] || '\r' == start_of_body[0])
       start_of_body++;
 
+    /* if message body is empty or contains a single CR/LF */
+    if (end_of_body <= start_of_body) {
+      osip_free (sep_boundary);
+      return OSIP_SYNTAXERROR;
+    }
+
     body_len = end_of_body - start_of_body;
 
     /* Skip CR before end boundary. */
-- 
2.13.1

d74a87c0247c43bdbba38632015a'>commit</a><a href='/guix/diff/gnu/packages/ntp.scm?id=8b2708a5660bd74a87c0247c43bdbba38632015a'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/packages/ntp.scm'>
<input type='hidden' name='id' value='8b2708a5660bd74a87c0247c43bdbba38632015a'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=8b2708a5660bd74a87c0247c43bdbba38632015a'>root</a>/<a href='/guix/log/gnu?id=8b2708a5660bd74a87c0247c43bdbba38632015a'>gnu</a>/<a href='/guix/log/gnu/packages?id=8b2708a5660bd74a87c0247c43bdbba38632015a'>packages</a>/<a href='/guix/log/gnu/packages/ntp.scm?id=8b2708a5660bd74a87c0247c43bdbba38632015a'>ntp.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/packages/ntp.scm?id=8b2708a5660bd74a87c0247c43bdbba38632015a&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2019-09-29 16:39:19 +0200'>2019-09-29</span></td><td><a href='/guix/commit/gnu/packages/ntp.scm?id=4ecf790e70dd22c204edad269cb661d820864906'>gnu: tlsdate: Build against OpenSSL@1.0.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/ntp.scm (tlsdate)[inputs]: Change from OPENSSL to OPENSSL-1.0.
</span></span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2019-09-08 23:15:31 +0900'>2019-09-08</span></td><td><a href='/guix/commit/gnu/packages/ntp.scm?id=f92cf9d356e5584b073a626bcb27ffb5ed7f99a7'>gnu: openntpd: Fix error CA errors when using constraints.</a><span class='msg-avail'>...<span class='msg-tooltip'>The error printed by nttpd was "constraint: failed to load constraint ca" when
libressl tried loading the file /etc/ssl/cert.pem.  The problem was
investigated as part of fixing issue 37318 (see:
http://debbugs.gnu.org/cgi/bugreport.cgi?bug=37318).

* gnu/packages/ntp.scm (openntpd)[configure-flags]: Use the '--with-cacert'
flag to specify the location of the certificate authority file of libressl.
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2019-03-18 23:42:47 +0100'>2019-03-18</span></td><td><a href='/guix/commit/gnu/packages/ntp.scm?id=0a8c2c98fb0b0727044f85b35f3350ea60e5a6bb'>gnu: ntp: Update to 4.2.8p13.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/ntp.scm (ntp): Update to 4.2.8p13.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>