ipapython: Propagate KRB5Error exceptions on iterating ccache

`ipapython.session_storage.get_data` iterates over
credentials in a credential cache till `krb5_cc_next_cred` returns
an error. This function doesn't expect any error on calling
other kerberos foreign functions during iteration. But that can
actually happen and KRB5Error exceptions stop an iteration while
they should be propagated.

With this change iteration will exactly stop on `krb5_cc_next_cred`
error as it was supposed to be.

Fixes: https://pagure.io/freeipa/issue/9519
Signed-off-by: Stanislav Levin <slev@altlinux.org>
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>

ipapython/session_storage.py

@@ -312,8 +312,12 @@ def get_data(princ_name, key):
                 checkcreds = krb5_creds()
                 # the next function will throw an error and break out of the
                 # while loop when we try to access past the last cred
-                krb5_cc_next_cred(context, ccache, ctypes.byref(cursor),
-                                  ctypes.byref(checkcreds))
+                try:
+                    krb5_cc_next_cred(context, ccache, ctypes.byref(cursor),
+                                      ctypes.byref(checkcreds))
+                except KRB5Error:
+                    break
+
                 if (krb5_principal_compare(context, principal,
                                           checkcreds.client) == 1 and
                     krb5_principal_compare(context, srv_princ,
@@ -328,8 +332,6 @@ def get_data(princ_name, key):
                 else:
                     krb5_free_cred_contents(context,
                                             ctypes.byref(checkcreds))
-        except KRB5Error:
-            pass
         finally:
             krb5_cc_end_seq_get(context, ccache, ctypes.byref(cursor))