[31646] in CVS-changelog-for-Kerberos-V5
krb5 commit: Check TXT lookup results on Windows
daemon@ATHENA.MIT.EDU (ghudson@mit.edu)
Mon Nov 9 11:59:18 2026
From: ghudson@mit.edu
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Date: Mon, 9 Nov 2026 11:59:11 -0500 (EST)
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https://github.com/krb5/krb5/commit/adce9735b119b75387e64016280faa1320a71ec6
commit adce9735b119b75387e64016280faa1320a71ec6
Author: Greg Hudson <ghudson@mit.edu>
Date: Sun Sep 20 03:48:12 2026 -0400
Check TXT lookup results on Windows
In the Windows implementation of k5_try_realm_txt_rr(), iterate
through the received records and pick one that is a non-empty TXT
record. Otherwise the function could dereference an invalid pointer
and crash (depending on the behavior of DnsQuery_UTF8(), which is not
fully known). Discovered by Aisle Research.
ticket: 9242 (new)
tags: pullup
target_version: 1.22-next
src/lib/krb5/os/dnsglue.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)
diff --git a/src/lib/krb5/os/dnsglue.c b/src/lib/krb5/os/dnsglue.c
index b422d8f48..aeb85e51f 100644
--- a/src/lib/krb5/os/dnsglue.c
+++ b/src/lib/krb5/os/dnsglue.c
@@ -351,7 +351,7 @@ k5_try_realm_txt_rr(krb5_context context, const char *prefix, const char *name,
{
krb5_error_code ret = 0;
char *txtname = NULL;
- PDNS_RECORD rr = NULL;
+ PDNS_RECORD records = NULL, rr;
DNS_STATUS st;
*realm = NULL;
@@ -361,13 +361,21 @@ k5_try_realm_txt_rr(krb5_context context, const char *prefix, const char *name,
return ENOMEM;
st = DnsQuery_UTF8(txtname, DNS_TYPE_TEXT, DNS_QUERY_STANDARD, NULL,
- &rr, NULL);
- if (st != ERROR_SUCCESS || rr == NULL) {
+ &records, NULL);
+ if (st != ERROR_SUCCESS || records == NULL) {
TRACE_TXT_LOOKUP_NOTFOUND(context, txtname);
ret = KRB5_ERR_HOST_REALM_UNKNOWN;
goto cleanup;
}
+ for (rr = records; rr != NULL; rr = rr->pNext) {
+ if (rr->wType == DNS_TYPE_TEXT && rr->Data.TXT.dwStringCount >= 1)
+ break;
+ }
+ if (rr == NULL) {
+ ret = KRB5_ERR_HOST_REALM_UNKNOWN;
+ goto cleanup;
+ }
*realm = strdup(rr->Data.TXT.pStringArray[0]);
if (*realm == NULL)
ret = ENOMEM;
@@ -375,8 +383,8 @@ k5_try_realm_txt_rr(krb5_context context, const char *prefix, const char *name,
cleanup:
free(txtname);
- if (rr != NULL)
- DnsRecordListFree(rr, DnsFreeRecordList);
+ if (records != NULL)
+ DnsRecordListFree(records, DnsFreeRecordList);
return ret;
}
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