Check retrieved TGT against local keytab, if it exists.
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aidan
parent
0bc8e23c3a
commit
b84b9c883a
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@ -1,4 +1,4 @@
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/* $NetBSD: k5login.c,v 1.14 2000/08/09 17:44:18 thorpej Exp $ */
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/* $NetBSD: k5login.c,v 1.15 2000/09/01 03:12:20 aidan Exp $ */
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/*-
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* Copyright (c) 1990 The Regents of the University of California.
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@ -33,12 +33,29 @@
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* SUCH DAMAGE.
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*/
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/*
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* Copyright (c) 1980, 1987, 1988 The Regents of the University of California.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms are permitted
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* provided that the above copyright notice and this paragraph are
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* duplicated in all such forms and that any documentation,
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* advertising materials, and other materials related to such
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* distribution and use acknowledge that the software was developed
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* by the University of California, Berkeley. The name of the
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* University may not be used to endorse or promote products derived
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* from this software without specific prior written permission.
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
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* WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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*/
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#include <sys/cdefs.h>
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#ifndef lint
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#if 0
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static char sccsid[] = "@(#)klogin.c 5.11 (Berkeley) 7/12/92";
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#endif
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__RCSID("$NetBSD: k5login.c,v 1.14 2000/08/09 17:44:18 thorpej Exp $");
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__RCSID("$NetBSD: k5login.c,v 1.15 2000/09/01 03:12:20 aidan Exp $");
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#endif /* not lint */
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#ifdef KERBEROS5
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@ -52,6 +69,7 @@ __RCSID("$NetBSD: k5login.c,v 1.14 2000/08/09 17:44:18 thorpej Exp $");
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <errno.h>
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#define KRB5_DEFAULT_OPTIONS 0
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#define KRB5_DEFAULT_LIFE 60*60*10 /* 10 hours */
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@ -72,6 +90,7 @@ static krb5_principal me, server;
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int k5_read_creds __P((char *));
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int k5_write_creds __P((void));
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int k5_verify_creds __P((krb5_context, krb5_ccache));
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int k5login __P((struct passwd *, char *, char *, char *));
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void k5destroy __P((void));
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@ -82,6 +101,125 @@ void k5destroy __P((void));
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#define krb5_realm_data(r) ((r).data)
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#endif
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/*
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* Verify the Kerberos ticket-granting ticket just retrieved for the
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* user. If the Kerberos server doesn't respond, assume the user is
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* trying to fake us out (since we DID just get a TGT from what is
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* supposedly our KDC). If the host/<host> service is unknown (i.e.,
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* the local keytab doesn't have it), let her in.
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*
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* Returns 1 for confirmation, -1 for failure, 0 for uncertainty.
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*/
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int
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k5_verify_creds(c, ccache)
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krb5_context c;
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krb5_ccache ccache;
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{
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char phost[MAXHOSTNAMELEN];
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int retval, have_keys;
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krb5_principal princ;
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krb5_keyblock *kb = 0;
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krb5_error_code kerror;
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krb5_data packet;
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krb5_auth_context auth_context = NULL;
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krb5_ticket *ticket = NULL;
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kerror = krb5_sname_to_principal(c, 0, 0, KRB5_NT_SRV_HST, &princ);
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if (kerror) {
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com_err("login", kerror, "constructing local service name");
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return (-1);
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}
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/* Do we have host/<host> keys? */
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/* (use default keytab, kvno IGNORE_VNO to get the first match,
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* and default enctype.) */
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kerror = krb5_kt_read_service_key(c, NULL, princ, 0, 0, &kb);
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if (kb)
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krb5_free_keyblock(c, kb);
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/* any failure means we don't have keys at all. */
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have_keys = kerror ? 0 : 1;
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/* XXX there should be a krb5 function like mk_req, but taking a full
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* principal, instead of a service/hostname. (Did I miss one?) */
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gethostname(phost, sizeof(phost));
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phost[sizeof(phost) - 1] = '\0';
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/* talk to the kdc and construct the ticket */
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kerror = krb5_mk_req(c, &auth_context, 0, "host", phost,
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0, ccache, &packet);
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/* wipe the auth context for rd_req */
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if (auth_context) {
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krb5_auth_con_free(c, auth_context);
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auth_context = NULL;
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}
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if (kerror == KRB5KDC_ERR_S_PRINCIPAL_UNKNOWN) {
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/* we have a service key, so something should be
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* in the database, therefore this error packet could
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* have come from an attacker. */
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if (have_keys) {
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retval = -1;
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goto EGRESS;
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}
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/* but if it is unknown and we've got no key, we don't
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* have any security anyhow, so it is ok. */
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else {
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retval = 0;
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goto EGRESS;
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}
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}
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else if (kerror) {
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com_err("login", kerror,
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"Unable to verify Kerberos V5 TGT: %s", phost);
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syslog(LOG_NOTICE|LOG_AUTH, "Kerberos V5 TGT bad: %s",
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error_message(kerror));
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retval = -1;
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goto EGRESS;
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}
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/* got ticket, try to use it */
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kerror = krb5_rd_req(c, &auth_context, &packet,
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princ, NULL, NULL, &ticket);
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if (kerror) {
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if (!have_keys) {
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/* The krb5 errors aren't specified well, but I think
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* these values cover the cases we expect. */
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switch (kerror) {
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case ENOENT: /* no keytab */
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case KRB5_KT_NOTFOUND:
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retval = 0;
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break;
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default:
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/* unexpected error: fail */
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retval = -1;
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break;
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}
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}
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else {
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/* we have keys, so if we got any error, we could be
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* under attack. */
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retval = -1;
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}
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com_err("login", kerror, "Unable to verify host ticket");
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syslog(LOG_NOTICE|LOG_AUTH, "can't verify v5 ticket: %s; %s\n",
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error_message(kerror),
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retval
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? "keytab found, assuming failure"
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: "no keytab found, assuming success");
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goto EGRESS;
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}
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/*
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* The host/<host> ticket has been received _and_ verified.
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*/
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retval = 1;
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/* do cleanup and return */
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EGRESS:
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if (auth_context)
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krb5_auth_con_free(c, auth_context);
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krb5_free_principal(c, princ);
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/* possibly ticket and packet need freeing here as well */
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return (retval);
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}
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/*
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* Attempt to read forwarded kerberos creds
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*
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@ -313,6 +451,10 @@ k5login(pw, instance, localhost, password)
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return(1);
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}
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if (k5_verify_creds(kcontext, ccache) < 0) {
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return(1);
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}
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/* Success */
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notickets = 0;
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