From 79d626dde9e7e38da79da1911338e18998e348df Mon Sep 17 00:00:00 2001
From: Greg Hudson <ghudson@mit.edu>
Date: Mon, 25 Jul 2016 13:28:43 -0400
Subject: [PATCH] Improve bad password inference in kinit

kinit currently outputs "Password incorrect" if it sees a
bad-integrity error code, which results if the KDC reply couldn't be
decrypted, or when encrypted timestamp preauth fails against an MIT
krb5 1.14 or earlier KDC.  Expand this check to include general
preauth failures reported by the KDC, but only if a password was
prompted for.

ticket: 8465 (new)
(cherry picked from commit 1a83ffad4d8e405ce696536c06d9bce1f8100595)
---
 src/clients/kinit/kinit.c | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/src/clients/kinit/kinit.c b/src/clients/kinit/kinit.c
index eba36b9..990fd11 100644
--- a/src/clients/kinit/kinit.c
+++ b/src/clients/kinit/kinit.c
@@ -700,9 +700,18 @@ kinit_prompter(
     krb5_prompt prompts[]
 )
 {
-    krb5_error_code rc =
-        krb5_prompter_posix(ctx, data, name, banner, num_prompts, prompts);
-    return rc;
+    krb5_boolean *pwprompt = data;
+    krb5_prompt_type *ptypes;
+    int i;
+
+    /* Make a note if we receive a password prompt. */
+    ptypes = krb5_get_prompt_types(ctx);
+    for (i = 0; i < num_prompts; i++) {
+        if (ptypes != NULL && ptypes[i] == KRB5_PROMPT_TYPE_PASSWORD)
+            *pwprompt = TRUE;
+    }
+
+    return krb5_prompter_posix(ctx, data, name, banner, num_prompts, prompts);
 }
 
 static int
@@ -715,6 +724,7 @@ k5_kinit(opts, k5)
     krb5_creds my_creds;
     krb5_error_code code = 0;
     krb5_get_init_creds_opt *options = NULL;
+    krb5_boolean pwprompt = FALSE;
     int i;
 
     memset(&my_creds, 0, sizeof(my_creds));
@@ -819,7 +829,7 @@ k5_kinit(opts, k5)
     switch (opts->action) {
     case INIT_PW:
         code = krb5_get_init_creds_password(k5->ctx, &my_creds, k5->me,
-                                            0, kinit_prompter, 0,
+                                            0, kinit_prompter, &pwprompt,
                                             opts->starttime,
                                             opts->service_name,
                                             options);
@@ -856,11 +866,15 @@ k5_kinit(opts, k5)
             break;
         }
 
-        if (code == KRB5KRB_AP_ERR_BAD_INTEGRITY)
+        /* If reply decryption failed, or if pre-authentication failed and we
+         * were prompted for a password, assume the password was wrong. */
+        if (code == KRB5KRB_AP_ERR_BAD_INTEGRITY ||
+            (pwprompt && code == KRB5KDC_ERR_PREAUTH_FAILED)) {
             fprintf(stderr, _("%s: Password incorrect while %s\n"), progname,
                     doing);
-        else
+        } else {
             com_err(progname, code, _("while %s"), doing);
+        }
         goto cleanup;
     }
 
-- 
2.9.3