[krbdev.mit.edu #8651] kinit -kt KDB: Cannot find/read stored master key

[Richard Basch via RT]

I ran a tight loop and simulated the issue.

In my test, the following conditions existed:
- The stash file is a non-standard location (and defined in the KRB5_KDC_PROFILE config (key_stash_file).
- Standard location stash file did not exist (not even as a symlink)

All my test essentially did was:
	while true ; do
	rm -f /tmp/ktrace.out /tmp/strace.out
	KRB5_KDC_PROFILE=… KRB5_CONFIG=… KRB5_TRACE=/tmp/ktrace.out strace -f -o /tmp/strace.out kinit -kt KDB: kadmin/admin || break
	done
The final run (after thousands of success) showed it looking for the STANDARD location stash file.


> On Mar 17, 2018, at 9:51 PM, Greg Hudson via RT <rt-comment at KRBDEV-PROD-APP-1.mit.edu> wrote:
> 
> [I moderated through the first copy to krb5-bugs, but not the second 
> copy, and I didn't moderate through to krbdev.  I prefer if messages 
> go to just one project list, so that the follow-up conversation 
> doesn't get fragmented.]
> 
> The cause of this bug is obscured by an error handling flaw in kinit 
> -t KDB:.  When kinit calls kinit_kbd_init(), it destroys and 
> recreates the krb5_context, but doesn't reset the global variable 
> errctx which is used by extended_com_err_fn().  That can be fixed 
> with the following patch:
> 
> diff --git a/src/clients/kinit/kinit.c b/src/clients/kinit/kinit.c
> index a518284..3fdae28 100644
> --- a/src/clients/kinit/kinit.c
> +++ b/src/clients/kinit/kinit.c
> @@ -718,6 +718,7 @@ k5_kinit(struct k_opts *opts, struct k5_data *k5)
> #ifndef _WIN32
>         if (strncmp(opts->keytab_name, "KDB:", 4) == 0) {
>             ret = kinit_kdb_init(&k5->ctx, k5->me->realm.data);
> +            errctx = k5->ctx;
>             if (ret) {
>                 com_err(progname, ret,
>                         _("while setting up KDB keytab for realm 
> %s"),
> 
> Without that fix, we just have the error string for 
> KRB5_KDB_CANTREAD_STORED, not the extended error message set in 
> krb5_db_def_fetch_mkey().  So all we know for now is that 
> krb5_db_def_fetch_mkey_keytab() didn't succeed.  It's hard to 
> theorize beyond that.  kt_file.c does contain locking calls, but they 
> are straightforward blocking POSIX file locks which shouldn't fail.
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