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telnetd/libtelnet/kerberos5.c

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/*-
* 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. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. 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.
*/
#include <sys/cdefs.h>
#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 "encrypt.h"
#include "auth.h"
#include "misc.h"
int forward_flags = 0; /* Flags get set in telnet/main.c on -f and -F */
/* These values need to be the same as those defined in telnet/main.c. */
/* Either define them in both places, or put in some common header file. */
#define OPTS_FORWARD_CREDS 0x00000002
#define OPTS_FORWARDABLE_CREDS 0x00000001
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;
static krb5_context context;
static krb5_auth_context auth_context;
static void
print_krb5_error(krb5_context context, krb5_error_code code, const char *msg)
{
const char *error_message;
error_message = krb5_get_error_message(context, code);
printf(msg, error_message);
krb5_free_error_message(context, error_message);
}
static int
Data(Authenticator *ap, int type, const char *d, int c)
{
unsigned char *p = str_data + 4;
const unsigned char *cd = 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(net_write(str_data, p - str_data));
}
int
kerberos5_init(Authenticator *ap __unused, int server)
{
krb5_error_code ret;
ret = krb5_init_context(&context);
if (ret)
return 0;
if (server) {
krb5_keytab kt;
krb5_kt_cursor cursor;
ret = krb5_kt_default(context, &kt);
if (ret)
return 0;
ret = krb5_kt_start_seq_get (context, kt, &cursor);
if (ret) {
krb5_kt_close (context, kt);
return 0;
}
krb5_kt_end_seq_get (context, kt, &cursor);
krb5_kt_close (context, kt);
str_data[3] = TELQUAL_REPLY;
} else
str_data[3] = TELQUAL_IS;
return(1);
}
extern int net;
static int
kerberos5_send(const char *name, Authenticator *ap)
{
krb5_error_code ret;
krb5_ccache ccache;
int ap_opts;
krb5_data cksum_data;
char foo[2];
if (!UserNameRequested) {
if (auth_debug_mode) {
printf("Kerberos V5: no user name supplied\r\n");
}
return(0);
}
ret = krb5_cc_default(context, &ccache);
if (ret) {
if (auth_debug_mode) {
print_krb5_error(context, ret, "Kerberos V5: could not get default ccache: %s\r\n");
}
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 (context, &auth_context);
if (ret) {
if (auth_debug_mode) {
print_krb5_error(context, ret, "Kerberos V5: krb5_auth_con_init failed (%s)\r\n");
}
return(0);
}
ret = krb5_auth_con_setaddrs_from_fd (context,
auth_context,
&net);
if (ret) {
if (auth_debug_mode) {
print_krb5_error(context, ret, "Kerberos V5:"
" krb5_auth_con_setaddrs_from_fd failed (%s)\r\n");
}
return(0);
}
krb5_auth_con_setkeytype (context, auth_context, KEYTYPE_DES);
foo[0] = ap->type;
foo[1] = ap->way;
cksum_data.length = sizeof(foo);
cksum_data.data = foo;
{
krb5_principal service;
char sname[128];
ret = krb5_sname_to_principal (context,
RemoteHostName,
NULL,
KRB5_NT_SRV_HST,
&service);
if(ret) {
if (auth_debug_mode) {
const char *err_str;
err_str = krb5_get_error_message(context, ret);
printf("Kerberosr V5:"
" krb5_sname_to_principal(%s) failed (%s)\r\n",
RemoteHostName, err_str);
krb5_free_error_message(context, err_str);
}
return 0;
}
ret = krb5_unparse_name_fixed(context, service, sname, sizeof(sname));
if(ret) {
if (auth_debug_mode) {
print_krb5_error(context, ret, "Kerberos V5:"
" krb5_unparse_name_fixed failed (%s)\r\n");
}
return 0;
}
printf("[ Trying %s (%s)... ]\r\n", name, sname);
ret = krb5_mk_req_exact(context, &auth_context, ap_opts,
service,
&cksum_data, ccache, &auth);
krb5_free_principal (context, service);
}
if (ret) {
if (1 || auth_debug_mode) {
print_krb5_error(context, ret, "Kerberos V5: mk_req failed (%s)\r\n");
}
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);
}
int
kerberos5_send_mutual(Authenticator *ap)
{
return kerberos5_send("mutual KERBEROS5", ap);
}
int
kerberos5_send_oneway(Authenticator *ap)
{
return kerberos5_send("KERBEROS5", ap);
}
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 (context, &auth_context);
if (ret) {
Data(ap, KRB_REJECT, "krb5_auth_con_init failed", -1);
auth_finished(ap, AUTH_REJECT);
if (auth_debug_mode)
print_krb5_error(context, ret, "Kerberos V5: krb5_auth_con_init failed (%s)\r\n");
return;
}
ret = krb5_auth_con_setaddrs_from_fd (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)
print_krb5_error(context, ret, "Kerberos V5: "
"krb5_auth_con_setaddrs_from_fd failed (%s)\r\n");
return;
}
ret = krb5_sock_to_principal (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)
print_krb5_error(context, ret, "Kerberos V5: "
"krb5_sock_to_principal failed (%s)\r\n");
return;
}
ret = krb5_rd_req(context,
&auth_context,
&auth,
server,
NULL,
NULL,
&ticket);
krb5_free_principal (context, server);
if (ret) {
char *errbuf;
const char *err_str;
err_str = krb5_get_error_message(context, ret);
asprintf(&errbuf,
"Read req failed: %s", err_str);
krb5_free_error_message(context, err_str);
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(context,
auth_context,
foo,
sizeof(foo));
if (ret) {
char *errbuf;
const char *err_str;
err_str = krb5_get_error_message(context, ret);
asprintf(&errbuf, "Bad checksum: %s", err_str);
krb5_free_error_message(context, err_str);
Data(ap, KRB_REJECT, errbuf, -1);
if (auth_debug_mode)
printf ("%s\r\n", errbuf);
free(errbuf);
return;
}
}
ret = krb5_auth_con_getremotesubkey (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)
print_krb5_error(context, ret, "Kerberos V5: "
"krb5_auth_con_getremotesubkey failed (%s)\r\n");
return;
}
if (key_block == NULL) {
ret = krb5_auth_con_getkey(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)
print_krb5_error(context, ret, "Kerberos V5: "
"krb5_auth_con_getkey failed (%s)\r\n");
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(context, auth_context, &outbuf);
if (ret) {
Data(ap, KRB_REJECT,
"krb5_mk_rep failed", -1);
auth_finished(ap, AUTH_REJECT);
if (auth_debug_mode)
print_krb5_error(context, ret, "Kerberos V5: "
"krb5_mk_rep failed (%s)\r\n");
return;
}
Data(ap, KRB_RESPONSE, outbuf.data, outbuf.length);
}
if (krb5_unparse_name(context, ticket->client, &name))
name = 0;
if(UserNameRequested && krb5_kuserok(context,
ticket->client,
UserNameRequested)) {
Data(ap, KRB_ACCEPT, 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_contents(context, key_block);
break;
}
auth_finished(ap, AUTH_USER);
krb5_free_keyblock_contents(context, key_block);
break;
case KRB_FORWARD: {
struct passwd *pwd;
char ccname[1024]; /* XXX */
krb5_data inbuf;
krb5_ccache ccache;
inbuf.data = (char *)data;
inbuf.length = cnt;
pwd = getpwnam (UserNameRequested);
if (pwd == NULL)
break;
snprintf (ccname, sizeof(ccname),
"FILE:/tmp/krb5cc_%u", pwd->pw_uid);
ret = krb5_cc_resolve (context, ccname, &ccache);
if (ret) {
if (auth_debug_mode)
print_krb5_error(context, ret, "Kerberos V5: could not get ccache: %s\r\n");
break;
}
ret = krb5_cc_initialize (context,
ccache,
ticket->client);
if (ret) {
if (auth_debug_mode)
print_krb5_error(context, ret, "Kerberos V5: could not init ccache: %s\r\n");
break;
}
#if defined(DCE)
esetenv("KRB5CCNAME", ccname, 1);
#endif
ret = krb5_rd_cred2 (context,
auth_context,
ccache,
&inbuf);
if(ret) {
char *errbuf;
const char *err_str;
err_str = krb5_get_error_message(context, ret);
asprintf (&errbuf,
"Read forwarded creds failed: %s", err_str);
krb5_free_error_message(context, err_str);
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);
#if defined(DCE)
dfsfwd = 1;
#endif
}
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 (context,
auth_context,
&keyblock);
if (ret)
ret = krb5_auth_con_getkey (context,
auth_context,
&keyblock);
if(ret) {
print_krb5_error(context, ret, "[ krb5_auth_con_getkey: %s ]\r\n");
auth_send_retry();
return;
}
skey.type = SK_DES;
skey.length = 8;
skey.data = keyblock->keyvalue.data;
encrypt_session_key(&skey, 0);
krb5_free_keyblock_contents (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(context, auth_context, &inbuf, &reply);
if (ret) {
print_krb5_error(context, ret, "[ Mutual authentication failed: %s ]\r\n");
auth_send_retry();
return;
}
krb5_free_ap_rep_enc_part(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 __unused, char *name, int level)
{
if (level < AUTH_USER)
return(level);
if (UserNameRequested &&
krb5_kuserok(context,
ticket->client,
UserNameRequested))
{
strcpy(name, UserNameRequested);
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 (context, &ccache);
if (ret) {
if (auth_debug_mode)
print_krb5_error(context, ret, "KerberosV5: could not get default ccache: %s\r\n");
return;
}
ret = krb5_cc_get_principal (context, ccache, &principal);
if (ret) {
if (auth_debug_mode)
print_krb5_error(context, ret, "KerberosV5: could not get principal: %s\r\n");
return;
}
memset (&creds, 0, sizeof(creds));
creds.client = principal;
ret = krb5_build_principal (context,
&creds.server,
strlen(principal->realm),
principal->realm,
"krbtgt",
principal->realm,
NULL);
if (ret) {
if (auth_debug_mode)
print_krb5_error(context, ret, "KerberosV5: could not get principal: %s\r\n");
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 (context,
auth_context,
ccache,
flags.i,
RemoteHostName,
&creds,
&out_data);
if (ret) {
if (auth_debug_mode)
print_krb5_error(context, ret, "Kerberos V5: error getting forwarded creds: %s\r\n");
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");
}
}
#if defined(DCE)
/* if this was a K5 authentication try and join a PAG for the user. */
void
kerberos5_dfspag(void)
{
if (dfsk5ok) {
dfspag = krb5_dfs_pag(context, dfsfwd, ticket->client,
UserNameRequested);
}
}
#endif
#endif /* KRB5 */
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