krb5 commit [krb5-1.22]: Detect iprop update of nonexistent principal

[ghudson at mit.edu]

https://github.com/krb5/krb5/commit/9f9ecf6933191a22b68b7041986611ac0f318f41
commit 9f9ecf6933191a22b68b7041986611ac0f318f41
Author: Zoltan Borbely <Zoltan.Borbely at morganstanley.com>
Date:   Tue Feb 10 19:05:16 2026 +0100

    Detect iprop update of nonexistent principal
    
    If the update log metadata falls out of sync with the database, a
    non-creation update entry could be applied to a nonexistent principal.
    This scenario currently results in a process abort with the DB2
    database module when krb5_encode_princ_entry() is invoked with
    entry->len set to zero.  Detect this mismatch in ulog_conv_2dbentry()
    and return an error to force a full resync.
    
    [ghudson at mit.edu: rewrote comment and commit message]
    
    (cherry picked from commit 3d5c8db948c2f4f67cc8b85eb94ad8a423c045f4)
    
    ticket: 9280
    version_fixed: 1.22.3

 src/lib/kdb/kdb_convert.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/lib/kdb/kdb_convert.c b/src/lib/kdb/kdb_convert.c
index 1231abc4f..a716c065a 100644
--- a/src/lib/kdb/kdb_convert.c
+++ b/src/lib/kdb/kdb_convert.c
@@ -747,6 +747,18 @@ ulog_conv_2dbentry(krb5_context context, krb5_db_entry **entry,
 #undef u
     }
 
+    if (ent->len == 0) {
+        /*
+         * The len field should have been set in the existing principal or (for
+         * a creation update) set in the update entry.  If was not set, we just
+         * applied a non-creation update to a nonexistent principal, implying
+         * that our database is out of sync with our ulog metadata.  Return an
+         * error to force a full resync.
+         */
+        ret = KRB5_KDB_NOENTRY;
+        goto cleanup;
+    }
+
     /*
      * process mod_princ_data request
      */