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NetBSD/lib/libtelnet/kerberos5.c

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/* $NetBSD: kerberos5.c,v 1.21 2021/04/12 09:17:48 mrg Exp $ */
/*-
* Copyright (c) 1991, 1993
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* Copyright (C) 1990 by the Massachusetts Institute of Technology
*
* Export of this software from the United States of America may
* require a specific license from the United States Government.
* It is the responsibility of any person or organization contemplating
* export to obtain such a license before exporting.
*
* WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
* distribute this software and its documentation for any purpose and
* without fee is hereby granted, provided that the above copyright
* notice appear in all copies and that both that copyright notice and
* this permission notice appear in supporting documentation, and that
* the name of M.I.T. not be used in advertising or publicity pertaining
* to distribution of the software without specific, written prior
* permission. M.I.T. makes no representations about the suitability of
* this software for any purpose. It is provided "as is" without express
* or implied warranty.
*/
#ifdef KRB5
#include <arpa/telnet.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <netdb.h>
#include <ctype.h>
#include <pwd.h>
#define Authenticator k5_Authenticator
#include <krb5.h>
#undef Authenticator
/* #include <roken.h> */
#include "encrypt.h"
#include "auth.h"
#include "misc.h"
extern int net;
int forward_flags; /* Flags get set in telnet/main.c on -f and -F */
int got_forwarded_creds;/* Tell telnetd to pass -F or -f to login. */
int require_hwpreauth;
const char *get_krb5_err_text(krb5_context, krb5_error_code);
void kerberos5_forward(Authenticator *);
static unsigned char str_data[1024] = {IAC, SB, TELOPT_AUTHENTICATION, 0,
AUTHTYPE_KERBEROS_V5,};
#define KRB_AUTH 0 /* Authentication data follows */
#define KRB_REJECT 1 /* Rejected (reason might follow) */
#define KRB_ACCEPT 2 /* Accepted */
#define KRB_RESPONSE 3 /* Response for mutual auth. */
#define KRB_FORWARD 4 /* Forwarded credentials follow */
#define KRB_FORWARD_ACCEPT 5 /* Forwarded credentials accepted */
#define KRB_FORWARD_REJECT 6 /* Forwarded credentials rejected */
static krb5_data auth;
static krb5_ticket *ticket;
krb5_context telnet_context;
static krb5_auth_context auth_context;
static int
Data(Authenticator *ap, int type, const void *d, int c)
{
unsigned char *p = str_data + 4;
const unsigned char *cd = (const unsigned char *) d;
if (c == -1)
c = strlen(cd);
if (auth_debug_mode) {
printf("%s:%d: [%d] (%d)",
str_data[3] == TELQUAL_IS ? ">>>IS" : ">>>REPLY",
str_data[3],
type, c);
printd(d, c);
printf("\r\n");
}
*p++ = ap->type;
*p++ = ap->way;
*p++ = type;
while (c-- > 0) {
if ((*p++ = *cd++) == IAC)
*p++ = IAC;
}
*p++ = IAC;
*p++ = SE;
if (str_data[3] == TELQUAL_IS)
printsub('>', &str_data[2], p - &str_data[2]);
return (telnet_net_write(str_data, p - str_data));
}
const char *
get_krb5_err_text(krb5_context ctx, krb5_error_code ret)
{
static const char *str = NULL;
if (str)
krb5_free_error_message(ctx, str);
str = krb5_get_error_message(ctx, ret);
if (str != NULL)
return str;
return "unknown";
}
int
kerberos5_init(Authenticator *ap, int server)
{
krb5_error_code ret;
if (telnet_context == 0) {
ret = krb5_init_context(&telnet_context);
if (ret)
return 0;
}
if (server) {
krb5_keytab kt;
krb5_kt_cursor cursor;
ret = krb5_kt_default(telnet_context, &kt);
if (ret)
return 0;
ret = krb5_kt_start_seq_get(telnet_context, kt, &cursor);
if (ret) {
krb5_kt_close(telnet_context, kt);
return 0;
}
krb5_kt_end_seq_get(telnet_context, kt, &cursor);
krb5_kt_close(telnet_context, kt);
str_data[3] = TELQUAL_REPLY;
} else
str_data[3] = TELQUAL_IS;
return (1);
}
int
kerberos5_send(Authenticator *ap)
{
krb5_error_code ret;
krb5_ccache ccache;
int ap_opts;
krb5_data cksum_data;
char foo[2];
printf("[ Trying KERBEROS5 ... ]\r\n");
if (!UserNameRequested) {
if (auth_debug_mode) {
printf("Kerberos V5: no user name supplied\r\n");
}
return (0);
}
ret = krb5_cc_default(telnet_context, &ccache);
if (ret) {
if (auth_debug_mode) {
printf(
"Kerberos V5: could not get default ccache: %s\r\n",
get_krb5_err_text(telnet_context, ret));
}
return (0);
}
if ((ap->way & AUTH_HOW_MASK) == AUTH_HOW_MUTUAL)
ap_opts = AP_OPTS_MUTUAL_REQUIRED;
else
ap_opts = 0;
ap_opts |= AP_OPTS_USE_SUBKEY;
ret = krb5_auth_con_init(telnet_context, &auth_context);
if (ret) {
if (auth_debug_mode) {
printf(
"Kerberos V5: krb5_auth_con_init failed: %s\r\n",
get_krb5_err_text(telnet_context, ret));
}
return (0);
}
ret = krb5_auth_con_setaddrs_from_fd(telnet_context,
auth_context, &net);
if (ret) {
if (auth_debug_mode) {
printf("Kerberos V5: "
"krb5_auth_con_setaddrs_from_fd failed: %s\r\n",
get_krb5_err_text(telnet_context, ret));
}
return (0);
}
krb5_auth_con_setkeytype(telnet_context, auth_context,
KRB5_ENCTYPE_DES_CBC_CRC);
foo[0] = ap->type;
foo[1] = ap->way;
cksum_data.length = sizeof(foo);
cksum_data.data = foo;
ret = krb5_mk_req(telnet_context, &auth_context, ap_opts, "host",
RemoteHostName, &cksum_data, ccache, &auth);
if (ret) {
if (1 || auth_debug_mode) {
printf("Kerberos V5: mk_req failed (%s)\r\n",
get_krb5_err_text(telnet_context, ret));
}
return (0);
}
if (!auth_sendname((unsigned char *) UserNameRequested,
strlen(UserNameRequested))) {
if (auth_debug_mode)
printf("Not enough room for user name\r\n");
return (0);
}
if (!Data(ap, KRB_AUTH, auth.data, auth.length)) {
if (auth_debug_mode)
printf("Not enough room for authentication data\r\n");
return (0);
}
if (auth_debug_mode) {
printf("Sent Kerberos V5 credentials to server\r\n");
}
return (1);
}
void
kerberos5_is(Authenticator * ap, unsigned char *data, int cnt)
{
krb5_error_code ret;
krb5_data outbuf;
krb5_keyblock *key_block;
char *name;
krb5_principal server;
int zero = 0;
if (cnt-- < 1)
return;
switch (*data++) {
case KRB_AUTH:
auth.data = (char *) data;
auth.length = cnt;
auth_context = NULL;
ret = krb5_auth_con_init(telnet_context, &auth_context);
if (ret) {
Data(ap, KRB_REJECT, "krb5_auth_con_init failed", -1);
auth_finished(ap, AUTH_REJECT);
if (auth_debug_mode)
printf("Kerberos V5: krb5_auth_con_init failed (%s)\r\n",
get_krb5_err_text(telnet_context, ret));
return;
}
ret = krb5_auth_con_setaddrs_from_fd(telnet_context,
auth_context, &zero);
if (ret) {
Data(ap, KRB_REJECT, "krb5_auth_con_setaddrs_from_fd failed", -1);
auth_finished(ap, AUTH_REJECT);
if (auth_debug_mode)
printf("Kerberos V5: "
"krb5_auth_con_setaddrs_from_fd failed (%s)\r\n",
get_krb5_err_text(telnet_context, ret));
return;
}
ret = krb5_sock_to_principal(telnet_context, 0, "host",
KRB5_NT_SRV_HST, &server);
if (ret) {
Data(ap, KRB_REJECT, "krb5_sock_to_principal failed", -1);
auth_finished(ap, AUTH_REJECT);
if (auth_debug_mode)
printf("Kerberos V5: "
"krb5_sock_to_principal failed (%s)\r\n",
get_krb5_err_text(telnet_context, ret));
return;
}
ret = krb5_rd_req(telnet_context, &auth_context, &auth,
server, NULL, NULL, &ticket);
krb5_free_principal(telnet_context, server);
if (ret) {
char *errbuf;
asprintf(&errbuf,
"Read req failed: %s",
get_krb5_err_text(telnet_context, ret));
Data(ap, KRB_REJECT, errbuf, -1);
if (auth_debug_mode)
printf("%s\r\n", errbuf);
free(errbuf);
return;
} {
char foo[2];
foo[0] = ap->type;
foo[1] = ap->way;
ret = krb5_verify_authenticator_checksum(telnet_context,
auth_context, foo, sizeof(foo));
if (ret) {
char *errbuf;
asprintf(&errbuf, "Bad checksum: %s",
get_krb5_err_text(telnet_context, ret));
Data(ap, KRB_REJECT, errbuf, -1);
if (auth_debug_mode)
printf("%s\r\n", errbuf);
free(errbuf);
return;
}
}
ret = krb5_auth_con_getremotesubkey(telnet_context,
auth_context, &key_block);
if (ret) {
Data(ap, KRB_REJECT, "krb5_auth_con_getremotesubkey failed", -1);
auth_finished(ap, AUTH_REJECT);
if (auth_debug_mode)
printf("Kerberos V5: "
"krb5_auth_con_getremotesubkey failed (%s)\r\n",
get_krb5_err_text(telnet_context, ret));
return;
}
if (key_block == NULL) {
ret = krb5_auth_con_getkey(telnet_context,
auth_context,
&key_block);
}
if (ret) {
Data(ap, KRB_REJECT, "krb5_auth_con_getkey failed", -1);
auth_finished(ap, AUTH_REJECT);
if (auth_debug_mode)
printf("Kerberos V5: "
"krb5_auth_con_getkey failed (%s)\r\n",
get_krb5_err_text(telnet_context, ret));
return;
}
if (key_block == NULL) {
Data(ap, KRB_REJECT, "no subkey received", -1);
auth_finished(ap, AUTH_REJECT);
if (auth_debug_mode)
printf("Kerberos V5: "
"krb5_auth_con_getremotesubkey returned NULL key\r\n");
return;
}
if ((ap->way & AUTH_HOW_MASK) == AUTH_HOW_MUTUAL) {
ret = krb5_mk_rep(telnet_context,
auth_context, &outbuf);
if (ret) {
Data(ap, KRB_REJECT,
"krb5_mk_rep failed", -1);
auth_finished(ap, AUTH_REJECT);
if (auth_debug_mode)
printf("Kerberos V5: "
"krb5_mk_rep failed (%s)\r\n",
get_krb5_err_text(telnet_context,
ret));
krb5_free_keyblock(telnet_context, key_block);
return;
}
Data(ap, KRB_RESPONSE, outbuf.data, outbuf.length);
}
if (krb5_unparse_name(telnet_context, ticket->client, &name))
name = 0;
if (UserNameRequested && krb5_kuserok(telnet_context,
ticket->client, UserNameRequested)) {
Data(ap, KRB_ACCEPT, name ? name : "", name ? -1 : 0);
if (auth_debug_mode) {
printf("Kerberos5 identifies him as ``%s''\r\n",
name ? name : "");
}
if (key_block->keytype == ETYPE_DES_CBC_MD5 ||
key_block->keytype == ETYPE_DES_CBC_MD4 ||
key_block->keytype == ETYPE_DES_CBC_CRC) {
Session_Key skey;
skey.type = SK_DES;
skey.length = 8;
skey.data = key_block->keyvalue.data;
encrypt_session_key(&skey, 0);
}
} else {
char *msg;
asprintf(&msg, "user `%s' is not authorized to "
"login as `%s'",
name ? name : "<unknown>",
UserNameRequested ? UserNameRequested : "<nobody>");
if (msg == NULL)
Data(ap, KRB_REJECT, NULL, 0);
else {
Data(ap, KRB_REJECT, (void *) msg, -1);
free(msg);
}
auth_finished(ap, AUTH_REJECT);
krb5_free_keyblock(telnet_context, key_block);
break;
}
auth_finished(ap, AUTH_USER);
krb5_free_keyblock(telnet_context, key_block);
break;
case KRB_FORWARD:{
struct passwd pws, *pwd;
char pwbuf[1024];
char ccname[1024]; /* XXX */
krb5_data inbuf;
krb5_ccache ccache;
inbuf.data = (char *) data;
inbuf.length = cnt;
if (getpwnam_r(UserNameRequested, &pws, pwbuf,
sizeof(pwbuf), &pwd) != 0 || pwd == NULL)
break;
snprintf(ccname, sizeof(ccname),
"FILE:/tmp/krb5cc_%u", pwd->pw_uid);
ret = krb5_cc_resolve(telnet_context, ccname, &ccache);
if (ret) {
if (auth_debug_mode)
printf("Kerberos V5: could not get ccache: %s\r\n",
get_krb5_err_text(telnet_context,
ret));
break;
}
ret = krb5_cc_initialize(telnet_context, ccache,
ticket->client);
if (ret) {
if (auth_debug_mode)
printf("Kerberos V5: could not init ccache: %s\r\n",
get_krb5_err_text(telnet_context,
ret));
break;
}
ret = krb5_rd_cred2(telnet_context, auth_context,
ccache, &inbuf);
if (ret) {
char *errbuf;
asprintf(&errbuf,
"Read forwarded creds failed: %s",
get_krb5_err_text(telnet_context, ret));
if (errbuf == NULL)
Data(ap, KRB_FORWARD_REJECT, NULL, 0);
else
Data(ap, KRB_FORWARD_REJECT, errbuf, -1);
if (auth_debug_mode)
printf("Could not read forwarded credentials: %s\r\n",
errbuf);
free(errbuf);
} else
Data(ap, KRB_FORWARD_ACCEPT, 0, 0);
chown(ccname + 5, pwd->pw_uid, -1);
if (auth_debug_mode)
printf("Forwarded credentials obtained\r\n");
break;
}
default:
if (auth_debug_mode)
printf("Unknown Kerberos option %d\r\n", data[-1]);
Data(ap, KRB_REJECT, 0, 0);
break;
}
}
void
kerberos5_reply(Authenticator * ap, unsigned char *data, int cnt)
{
static int mutual_complete = 0;
if (cnt-- < 1)
return;
switch (*data++) {
case KRB_REJECT:
if (cnt > 0) {
printf("[ Kerberos V5 refuses authentication because %.*s ]\r\n",
cnt, data);
} else
printf("[ Kerberos V5 refuses authentication ]\r\n");
auth_send_retry();
return;
case KRB_ACCEPT:{
krb5_error_code ret;
Session_Key skey;
krb5_keyblock *keyblock;
if ((ap->way & AUTH_HOW_MASK) == AUTH_HOW_MUTUAL &&
!mutual_complete) {
printf("[ Kerberos V5 accepted you, but didn't provide mutual authentication! ]\r\n");
auth_send_retry();
return;
}
if (cnt)
printf("[ Kerberos V5 accepts you as ``%.*s'' ]\r\n", cnt, data);
else
printf("[ Kerberos V5 accepts you ]\r\n");
ret = krb5_auth_con_getlocalsubkey(telnet_context,
auth_context, &keyblock);
if (ret)
ret = krb5_auth_con_getkey(telnet_context,
auth_context, &keyblock);
if (ret) {
printf("[ krb5_auth_con_getkey: %s ]\r\n",
get_krb5_err_text(telnet_context, ret));
auth_send_retry();
return;
}
skey.type = SK_DES;
skey.length = 8;
skey.data = keyblock->keyvalue.data;
encrypt_session_key(&skey, 0);
krb5_free_keyblock(telnet_context, keyblock);
auth_finished(ap, AUTH_USER);
if (forward_flags & OPTS_FORWARD_CREDS)
kerberos5_forward(ap);
break;
}
case KRB_RESPONSE:
if ((ap->way & AUTH_HOW_MASK) == AUTH_HOW_MUTUAL) {
/* the rest of the reply should contain a krb_ap_rep */
krb5_ap_rep_enc_part *reply;
krb5_data inbuf;
krb5_error_code ret;
inbuf.length = cnt;
inbuf.data = (char *) data;
ret = krb5_rd_rep(telnet_context,
auth_context, &inbuf, &reply);
if (ret) {
printf("[ Mutual authentication failed: %s ]\r\n",
get_krb5_err_text(telnet_context, ret));
auth_send_retry();
return;
}
krb5_free_ap_rep_enc_part(telnet_context, reply);
mutual_complete = 1;
}
return;
case KRB_FORWARD_ACCEPT:
printf("[ Kerberos V5 accepted forwarded credentials ]\r\n");
return;
case KRB_FORWARD_REJECT:
printf("[ Kerberos V5 refuses forwarded credentials because %.*s ]\r\n",
cnt, data);
return;
default:
if (auth_debug_mode)
printf("Unknown Kerberos option %d\r\n", data[-1]);
return;
}
}
int
kerberos5_status(Authenticator *ap, char *name, size_t l, int level)
{
if (level < AUTH_USER)
return (level);
if (UserNameRequested &&
krb5_kuserok(telnet_context, ticket->client, UserNameRequested)) {
strlcpy(name, UserNameRequested, l);
return (AUTH_VALID);
} else
return (AUTH_USER);
}
#define BUMP(buf, len) while (*(buf)) {++(buf), --(len);}
#define ADDC(buf, len, c) if ((len) > 0) {*(buf)++ = (c); --(len);}
void
kerberos5_printsub(unsigned char *data, int cnt, unsigned char *buf, int buflen)
{
int i;
buf[buflen - 1] = '\0'; /* make sure its NULL terminated */
buflen -= 1;
switch (data[3]) {
case KRB_REJECT: /* Rejected (reason might follow) */
strlcpy((char *) buf, " REJECT ", buflen);
goto common;
case KRB_ACCEPT: /* Accepted (name might follow) */
strlcpy((char *) buf, " ACCEPT ", buflen);
common:
BUMP(buf, buflen);
if (cnt <= 4)
break;
ADDC(buf, buflen, '"');
for (i = 4; i < cnt; i++)
ADDC(buf, buflen, data[i]);
ADDC(buf, buflen, '"');
ADDC(buf, buflen, '\0');
break;
case KRB_AUTH: /* Authentication data follows */
strlcpy((char *) buf, " AUTH", buflen);
goto common2;
case KRB_RESPONSE:
strlcpy((char *) buf, " RESPONSE", buflen);
goto common2;
case KRB_FORWARD: /* Forwarded credentials follow */
strlcpy((char *) buf, " FORWARD", buflen);
goto common2;
case KRB_FORWARD_ACCEPT: /* Forwarded credentials accepted */
strlcpy((char *) buf, " FORWARD_ACCEPT", buflen);
goto common2;
case KRB_FORWARD_REJECT: /* Forwarded credentials rejected */
/* (reason might follow) */
strlcpy((char *) buf, " FORWARD_REJECT", buflen);
goto common2;
default:
snprintf(buf, buflen, " %d (unknown)", data[3]);
common2:
BUMP(buf, buflen);
for (i = 4; i < cnt; i++) {
snprintf(buf, buflen, " %d", data[i]);
BUMP(buf, buflen);
}
break;
}
}
void
kerberos5_forward(Authenticator * ap)
{
krb5_error_code ret;
krb5_ccache ccache;
krb5_creds creds;
krb5_kdc_flags flags;
krb5_data out_data;
krb5_principal principal;
ret = krb5_cc_default(telnet_context, &ccache);
if (ret) {
if (auth_debug_mode)
printf("KerberosV5: could not get default ccache: %s\r\n",
get_krb5_err_text(telnet_context, ret));
return;
}
ret = krb5_cc_get_principal(telnet_context, ccache, &principal);
if (ret) {
if (auth_debug_mode)
printf("KerberosV5: could not get principal: %s\r\n",
get_krb5_err_text(telnet_context, ret));
return;
}
memset(&creds, 0, sizeof(creds));
creds.client = principal;
ret = krb5_build_principal(telnet_context, &creds.server,
strlen(principal->realm), principal->realm, "krbtgt",
principal->realm, NULL);
if (ret) {
if (auth_debug_mode)
printf("KerberosV5: could not get principal: %s\r\n",
get_krb5_err_text(telnet_context, ret));
return;
}
creds.times.endtime = 0;
flags.i = 0;
flags.b.forwarded = 1;
if (forward_flags & OPTS_FORWARDABLE_CREDS)
flags.b.forwardable = 1;
ret = krb5_get_forwarded_creds(telnet_context, auth_context,
ccache, flags.i, RemoteHostName, &creds, &out_data);
if (ret) {
if (auth_debug_mode)
printf("Kerberos V5: error getting forwarded creds: %s\r\n",
get_krb5_err_text(telnet_context, ret));
return;
}
if (!Data(ap, KRB_FORWARD, out_data.data, out_data.length)) {
if (auth_debug_mode)
printf("Not enough room for authentication data\r\n");
} else {
if (auth_debug_mode)
printf("Forwarded local Kerberos V5 credentials to server\r\n");
}
}
#endif /* KRB5 */
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