Fix CVE-2020-10595:

https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-10595

Patch copied from upstream advisory:

https://seclists.org/oss-sec/2020/q1/128

diff --git a/prompting.c b/prompting.c
index e985d95..d81054f 100644
--- a/prompting.c
+++ b/prompting.c
@@ -314,26 +314,27 @@ pamk5_prompter_krb5(krb5_context context UNUSED, void *data, const char *name,
     /*
      * Reuse pam_prompts as a starting index and copy the data into the reply
      * area of the krb5_prompt structs.
      */
     pam_prompts = 0;
     if (name != NULL && !args->silent)
         pam_prompts++;
     if (banner != NULL && !args->silent)
         pam_prompts++;
     for (i = 0; i < num_prompts; i++, pam_prompts++) {
-        size_t len;
+        size_t len, allowed;

         if (resp[pam_prompts].resp == NULL)
             goto cleanup;
         len = strlen(resp[pam_prompts].resp);
-        if (len > prompts[i].reply->length)
+        allowed = prompts[i].reply->length;
+        if (allowed == 0 || len > allowed - 1)
             goto cleanup;

         /*
          * The trailing nul is not included in length, but other applications
          * expect it to be there.  Therefore, we copy one more byte than the
          * actual length of the password, but set length to just the length of
          * the password.
          */
         memcpy(prompts[i].reply->data, resp[pam_prompts].resp, len + 1);
         prompts[i].reply->length = (unsigned int) len;
='/guix/diff/gnu/services/security-token.scm?id=5e7da50260fbe7a979b8d32665d868a761f0376b'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/services/security-token.scm'>
<input type='hidden' name='id' value='5e7da50260fbe7a979b8d32665d868a761f0376b'/><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=5e7da50260fbe7a979b8d32665d868a761f0376b'>root</a>/<a href='/guix/log/gnu?id=5e7da50260fbe7a979b8d32665d868a761f0376b'>gnu</a>/<a href='/guix/log/gnu/services?id=5e7da50260fbe7a979b8d32665d868a761f0376b'>services</a>/<a href='/guix/log/gnu/services/security-token.scm?id=5e7da50260fbe7a979b8d32665d868a761f0376b'>security-token.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/services/security-token.scm?id=5e7da50260fbe7a979b8d32665d868a761f0376b&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2023-12-22 00:31:41 +0100'>2023-12-22</span></td><td><a href='/guix/commit/gnu/services/security-token.scm?id=3d6583727ec90732ad7bd97808fd4fca8f6d8bdc'>services: Remove unnecessary references to (gnu build shepherd).</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/databases.scm (memcached-shepherd-service): Remove
‘with-imported-modules’ form and ‘modules’ field.
* gnu/services/security-token.scm (pcscd-shepherd-service): Remove
‘with-imported-modules’ form.
* gnu/services/web.scm (hpcguix-web-shepherd-service): Likewise.

Change-Id: Ieb817508f1751e0c1ff551a0e078789a4a813c1c
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-06-25 01:43:08 +0530'>2022-06-25</span></td><td><a href='/guix/commit/gnu/services/security-token.scm?id=037bfd85458dd0b32a6dd85b7c12e85e3dd716ae'>services: pcscd: Use switch-symlinks from (guix build utils).</a><span class='msg-avail'>...<span class='msg-tooltip'>switch-symlinks has been moved to (guix build utils). We need not duplicate it
anymore.

* gnu/services/security-token.scm (pcscd-activation): Use switch-symlinks
from (guix build utils).
</span></span></td><td>Arun Isaac</td></tr>
<tr><td><span title='2021-07-03 20:13:42 +0200'>2021-07-03</span></td><td><a href='/guix/commit/gnu/services/security-token.scm?id=e789ce538ed848bacb8f4eb5742f78b965ccf57c'>services: pcscd: Fix daemon signal handling.</a><span class='msg-avail'>...<span class='msg-tooltip'>"pcscd" wouldn't handle SIGTERM as it inherit ignoring this signal (and
others) from its parent shepherd; fork+exec-command restore signal
handling.  Fixes &lt;https://issues.guix.gnu.org/45202&gt;.

* gnu/services/security-token.scm (pcscd)[start]: Use
fork+exec-command to start "pcscd".
</span></span></td><td>Brice Waegeneire</td></tr>
<tr><td><span title='2021-06-19 23:49:18 +0200'>2021-06-19</span></td><td><a href='/guix/commit/gnu/services/security-token.scm?id=4bed8486d4c0a4ff142903b8bc1584ce84767355'>services: pcscd: Cleanup socket when started.</a><span class='msg-avail'>...<span class='msg-tooltip'>Otherwise when pcscd doesn't terminate properly (ie. receive a SIGKILL),
it won't start again because of it's socket already existing.

* gnu/services/security-token.scm (pcscd-shepherd-service)[start]:
Remove existing socket file.
</span></span></td><td>Brice Waegeneire</td></tr>
<tr><td><span title='2020-12-13 00:35:49 +0100'>2020-12-13</span></td><td><a href='/guix/commit/gnu/services/security-token.scm?id=a4cd86ff4b7a9dd4bf1a5320b8121b470e381b67'>gnu: htop: Update to 3.0.3.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/admin.scm (htop): Update to 3.0.3.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2020-12-12 23:10:05 +0100'>2020-12-12</span></td><td><a href='/guix/commit/gnu/services/security-token.scm?id=8f2656f1debffe92ea088f4c88cfe8ec560b2ba3'>services: pcscd-shepherd-service: Fix PID file location.</a><span class='msg-avail'>...<span class='msg-tooltip'>Fixes &lt;http://issues.guix.gnu.org/45202&gt;.

* gnu/services/security-token.scm (pcscd-shepherd-service): Look for
pcscd.pid in /run instead of /var/run.

Reported by Raffael Stocker &lt;r.stocker@mnet-mail.de&gt;.
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>