Fix CVE-2018-1000097:

https://security-tracker.debian.org/tracker/CVE-2018-1000097
https://nvd.nist.gov/vuln/detail/CVE-2018-1000097

Patch taken from upstream bug report:
https://lists.gnu.org/archive/html/bug-gnu-utils/2018-02/msg00005.html

diff --git a/src/unshar.c b/src/unshar.c
index 80bc3a9..0fc3773 100644
--- a/src/unshar.c
+++ b/src/unshar.c
@@ -240,7 +240,7 @@ find_archive (char const * name, FILE * file, off_t start)
       off_t position = ftello (file);
 
       /* Read next line, fail if no more and no previous process.  */
-      if (!fgets (rw_buffer, BUFSIZ, file))
+      if (!fgets (rw_buffer, rw_base_size, file))
 	{
 	  if (!start)
 	    error (0, 0, _("Found no shell commands in %s"), name);
ko' selected='selected'>koszko</option>
<option value='koszko-scripts'>koszko-scripts</option>
</select> <input type='submit' value='switch'/></form></td></tr>
<tr><td class='sub'>Wojtek's customized Guix</td><td class='sub right'></td></tr></table>
<table class='tabs'><tr><td>
<a href='/guix/about/'>about</a><a href='/guix/'>summary</a><a href='/guix/refs/?id=75ebc650c8a4e0f5b51a510891c22e2a39268142'>refs</a><a class='active' href='/guix/log/tests/elpa.scm'>log</a><a href='/guix/tree/tests/elpa.scm?id=75ebc650c8a4e0f5b51a510891c22e2a39268142'>tree</a><a href='/guix/commit/tests/elpa.scm?id=75ebc650c8a4e0f5b51a510891c22e2a39268142'>commit</a><a href='/guix/diff/tests/elpa.scm?id=75ebc650c8a4e0f5b51a510891c22e2a39268142'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/tests/elpa.scm'>
<input type='hidden' name='id' value='75ebc650c8a4e0f5b51a510891c22e2a39268142'/><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=75ebc650c8a4e0f5b51a510891c22e2a39268142'>root</a>/<a href='/guix/log/tests?id=75ebc650c8a4e0f5b51a510891c22e2a39268142'>tests</a>/<a href='/guix/log/tests/elpa.scm?id=75ebc650c8a4e0f5b51a510891c22e2a39268142'>elpa.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/tests/elpa.scm?id=75ebc650c8a4e0f5b51a510891c22e2a39268142&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-01-16 23:14:05 +0100'>2020-01-16</span></td><td><a href='/guix/commit/tests/elpa.scm?id=9d6c6cb20ef240221fc9a8e155f4bfa53e71bce4'>import: elpa: Rewrite test to use an HTTP server instead of mocking.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-03-18 22:33:41 +0100'>2018-03-18</span></td><td><a href='/guix/commit/tests/elpa.scm?id=17cdd3d0fe1987d0272f2c3496123be1ef772d6b'>tests: elpa: Don't actually download files.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-03-18 22:25:54 +0100'>2018-03-18</span></td><td><a href='/guix/commit/tests/elpa.scm?id=e5425ed950d06f8e75697b7e8562f71704094453'>import: elpa: Adjust test for HTTPS URLs.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>