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;
ild-aux/mdate-from-git.scm?id=be81d464728cf95e015e5a89a833d9d464d39442'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/build-aux/mdate-from-git.scm'>
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<div class='path'>path: <a href='/guix/log/?id=be81d464728cf95e015e5a89a833d9d464d39442'>root</a>/<a href='/guix/log/build-aux?id=be81d464728cf95e015e5a89a833d9d464d39442'>build-aux</a>/<a href='/guix/log/build-aux/mdate-from-git.scm?id=be81d464728cf95e015e5a89a833d9d464d39442'>mdate-from-git.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/build-aux/mdate-from-git.scm?id=be81d464728cf95e015e5a89a833d9d464d39442&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2024-04-19 16:45:41 +0200'>2024-04-19</span></td><td><a href='/guix/commit/build-aux/mdate-from-git.scm?id=2b8a2a6e723a0cf987c814865df9368e6348b6f8'>maint: Generate doc/version[-LANG].texi using `mdate-from-git.scm'.</a><span class='msg-avail'>...<span class='msg-tooltip'>This replaces Automake's `build-aux/mdate-sh' with our own
`build-aux/mdate-from-git.scm' to use reproducible timestamps from Git
instead.

* build-aux/mdate-from-git.scm: New script.
* bootstrap: Use it to replace build-aux/mdate-sh.
* Makefile.am (EXTRA_DIST): Add it.

Change-Id: I17d0a7de9ffea397129c0db1728f86e28a4e245f
</span></span></td><td>Janneke Nieuwenhuizen</td></tr>