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telnetd/libtelnet/sra.c

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/*-
* Copyright (c) 1991, 1993
* Dave Safford. 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.
*
*/
#include <sys/cdefs.h>
#ifdef SRA
#ifdef ENCRYPTION
#include <sys/types.h>
#include "arpa/telnet.h"
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <ttyent.h>
#ifndef NOPAM
#include <security/pam_appl.h>
#else
#include <unistd.h>
#endif
#include "auth.h"
#include "misc.h"
#include "encrypt.h"
#include "pk.h"
char pka[HEXKEYBYTES+1], ska[HEXKEYBYTES+1], pkb[HEXKEYBYTES+1];
char *user, *pass, *xuser, *xpass;
DesData ck;
IdeaData ik;
extern int auth_debug_mode;
extern char line[];
static int sra_valid = 0;
static int passwd_sent = 0;
static unsigned char str_data[1024] = { IAC, SB, TELOPT_AUTHENTICATION, 0,
AUTHTYPE_SRA, };
#define SRA_KEY 0
#define SRA_USER 1
#define SRA_CONTINUE 2
#define SRA_PASS 3
#define SRA_ACCEPT 4
#define SRA_REJECT 5
static int check_user(char *, char *);
/* support routine to send out authentication message */
static int
Data(Authenticator *ap, int type, void *d, int c)
{
unsigned char *p = str_data + 4;
unsigned char *cd = (unsigned char *)d;
if (c == -1)
c = strlen((char *)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
sra_init(Authenticator *ap __unused, int server)
{
if (server)
str_data[3] = TELQUAL_REPLY;
else
str_data[3] = TELQUAL_IS;
user = (char *)malloc(256);
xuser = (char *)malloc(513);
pass = (char *)malloc(256);
xpass = (char *)malloc(513);
if (user == NULL || xuser == NULL || pass == NULL || xpass ==
NULL)
return 0; /* malloc failed */
passwd_sent = 0;
genkeys(pka,ska);
return(1);
}
/* client received a go-ahead for sra */
int
sra_send(Authenticator *ap)
{
/* send PKA */
if (auth_debug_mode)
printf("Sent PKA to server.\r\n" );
printf("Trying SRA secure login:\r\n");
if (!Data(ap, SRA_KEY, (void *)pka, HEXKEYBYTES)) {
if (auth_debug_mode)
printf("Not enough room for authentication data\r\n");
return(0);
}
return(1);
}
/* server received an IS -- could be SRA KEY, USER, or PASS */
void
sra_is(Authenticator *ap, unsigned char *data, int cnt)
{
int valid;
Session_Key skey;
if (cnt-- < 1)
goto bad;
switch (*data++) {
case SRA_KEY:
if (cnt < HEXKEYBYTES) {
Data(ap, SRA_REJECT, (void *)0, 0);
auth_finished(ap, AUTH_USER);
if (auth_debug_mode) {
printf("SRA user rejected for bad PKB\r\n");
}
return;
}
if (auth_debug_mode)
printf("Sent pka\r\n");
if (!Data(ap, SRA_KEY, (void *)pka, HEXKEYBYTES)) {
if (auth_debug_mode)
printf("Not enough room\r\n");
return;
}
memcpy(pkb,data,HEXKEYBYTES);
pkb[HEXKEYBYTES] = '\0';
common_key(ska,pkb,&ik,&ck);
return;
case SRA_USER:
/* decode KAB(u) */
if (cnt > 512) /* Attempted buffer overflow */
break;
memcpy(xuser,data,cnt);
xuser[cnt] = '\0';
pk_decode(xuser,user,&ck);
auth_encrypt_user(user);
Data(ap, SRA_CONTINUE, (void *)0, 0);
return;
case SRA_PASS:
if (cnt > 512) /* Attempted buffer overflow */
break;
/* decode KAB(P) */
memcpy(xpass,data,cnt);
xpass[cnt] = '\0';
pk_decode(xpass,pass,&ck);
/* check user's password */
valid = check_user(user,pass);
if(valid) {
Data(ap, SRA_ACCEPT, (void *)0, 0);
skey.data = ck;
skey.type = SK_DES;
skey.length = 8;
encrypt_session_key(&skey, 1);
sra_valid = 1;
auth_finished(ap, AUTH_VALID);
if (auth_debug_mode) {
printf("SRA user accepted\r\n");
}
}
else {
Data(ap, SRA_CONTINUE, (void *)0, 0);
/*
Data(ap, SRA_REJECT, (void *)0, 0);
sra_valid = 0;
auth_finished(ap, AUTH_REJECT);
*/
if (auth_debug_mode) {
printf("SRA user failed\r\n");
}
}
return;
default:
if (auth_debug_mode)
printf("Unknown SRA option %d\r\n", data[-1]);
}
bad:
Data(ap, SRA_REJECT, 0, 0);
sra_valid = 0;
auth_finished(ap, AUTH_REJECT);
}
/* client received REPLY -- could be SRA KEY, CONTINUE, ACCEPT, or REJECT */
void
sra_reply(Authenticator *ap, unsigned char *data, int cnt)
{
char uprompt[256],tuser[256];
Session_Key skey;
size_t i;
if (cnt-- < 1)
return;
switch (*data++) {
case SRA_KEY:
/* calculate common key */
if (cnt < HEXKEYBYTES) {
if (auth_debug_mode) {
printf("SRA user rejected for bad PKB\r\n");
}
return;
}
memcpy(pkb,data,HEXKEYBYTES);
pkb[HEXKEYBYTES] = '\0';
common_key(ska,pkb,&ik,&ck);
enc_user:
/* encode user */
memset(tuser,0,sizeof(tuser));
sprintf(uprompt,"User (%s): ",UserNameRequested);
telnet_gets(uprompt,tuser,255,1);
if (tuser[0] == '\n' || tuser[0] == '\r' )
strcpy(user,UserNameRequested);
else {
/* telnet_gets leaves the newline on */
for(i=0;i<sizeof(tuser);i++) {
if (tuser[i] == '\n') {
tuser[i] = '\0';
break;
}
}
strcpy(user,tuser);
}
pk_encode(user,xuser,&ck);
/* send it off */
if (auth_debug_mode)
printf("Sent KAB(U)\r\n");
if (!Data(ap, SRA_USER, (void *)xuser, strlen(xuser))) {
if (auth_debug_mode)
printf("Not enough room\r\n");
return;
}
break;
case SRA_CONTINUE:
if (passwd_sent) {
passwd_sent = 0;
printf("[ SRA login failed ]\r\n");
goto enc_user;
}
/* encode password */
memset(pass,0,256);
telnet_gets("Password: ",pass,255,0);
pk_encode(pass,xpass,&ck);
/* send it off */
if (auth_debug_mode)
printf("Sent KAB(P)\r\n");
if (!Data(ap, SRA_PASS, (void *)xpass, strlen(xpass))) {
if (auth_debug_mode)
printf("Not enough room\r\n");
return;
}
passwd_sent = 1;
break;
case SRA_REJECT:
printf("[ SRA refuses authentication ]\r\n");
printf("Trying plaintext login:\r\n");
auth_finished(0,AUTH_REJECT);
return;
case SRA_ACCEPT:
printf("[ SRA accepts you ]\r\n");
skey.data = ck;
skey.type = SK_DES;
skey.length = 8;
encrypt_session_key(&skey, 0);
auth_finished(ap, AUTH_VALID);
return;
default:
if (auth_debug_mode)
printf("Unknown SRA option %d\r\n", data[-1]);
return;
}
}
int
sra_status(Authenticator *ap __unused, char *name, int level)
{
if (level < AUTH_USER)
return(level);
if (UserNameRequested && sra_valid) {
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
sra_printsub(unsigned char *data, int cnt, unsigned char *buf, int buflen)
{
char lbuf[32];
int i;
buf[buflen-1] = '\0'; /* make sure its NULL terminated */
buflen -= 1;
switch(data[3]) {
case SRA_CONTINUE:
strncpy((char *)buf, " CONTINUE ", buflen);
goto common;
case SRA_REJECT: /* Rejected (reason might follow) */
strncpy((char *)buf, " REJECT ", buflen);
goto common;
case SRA_ACCEPT: /* Accepted (name might follow) */
strncpy((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 SRA_KEY: /* Authentication data follows */
strncpy((char *)buf, " KEY ", buflen);
goto common2;
case SRA_USER:
strncpy((char *)buf, " USER ", buflen);
goto common2;
case SRA_PASS:
strncpy((char *)buf, " PASS ", buflen);
goto common2;
default:
sprintf(lbuf, " %d (unknown)", data[3]);
strncpy((char *)buf, lbuf, buflen);
common2:
BUMP(buf, buflen);
for (i = 4; i < cnt; i++) {
sprintf(lbuf, " %d", data[i]);
strncpy((char *)buf, lbuf, buflen);
BUMP(buf, buflen);
}
break;
}
}
static int
isroot(const char *usr)
{
struct passwd *pwd;
if ((pwd=getpwnam(usr))==NULL)
return 0;
return (!pwd->pw_uid);
}
static int
rootterm(char *ttyn)
{
struct ttyent *t;
return ((t = getttynam(ttyn)) && t->ty_status & TTY_SECURE);
}
#ifdef NOPAM
static int
check_user(char *name, char *cred)
{
char *cp;
char *xpasswd, *salt;
if (isroot(name) && !rootterm(line))
{
crypt("AA","*"); /* Waste some time to simulate success */
return(0);
}
if (pw = sgetpwnam(name)) {
if (pw->pw_shell == NULL) {
pw = (struct passwd *) NULL;
return(0);
}
salt = pw->pw_passwd;
xpasswd = crypt(cred, salt);
/* The strcmp does not catch null passwords! */
if (pw == NULL || *pw->pw_passwd == '\0' ||
strcmp(xpasswd, pw->pw_passwd)) {
pw = (struct passwd *) NULL;
return(0);
}
return(1);
}
return(0);
}
#else
/*
* The following is stolen from ftpd, which stole it from the imap-uw
* PAM module and login.c. It is needed because we can't really
* "converse" with the user, having already gone to the trouble of
* getting their username and password through an encrypted channel.
*/
#define COPY_STRING(s) (s ? strdup(s):NULL)
struct cred_t {
const char *uname;
const char *pass;
};
typedef struct cred_t cred_t;
static int
auth_conv(int num_msg, const struct pam_message **msg, struct pam_response **resp, void *appdata)
{
int i;
cred_t *cred = (cred_t *) appdata;
struct pam_response *reply =
malloc(sizeof(struct pam_response) * num_msg);
if (reply == NULL)
return PAM_BUF_ERR;
for (i = 0; i < num_msg; i++) {
switch (msg[i]->msg_style) {
case PAM_PROMPT_ECHO_ON: /* assume want user name */
reply[i].resp_retcode = PAM_SUCCESS;
reply[i].resp = COPY_STRING(cred->uname);
/* PAM frees resp. */
break;
case PAM_PROMPT_ECHO_OFF: /* assume want password */
reply[i].resp_retcode = PAM_SUCCESS;
reply[i].resp = COPY_STRING(cred->pass);
/* PAM frees resp. */
break;
case PAM_TEXT_INFO:
case PAM_ERROR_MSG:
reply[i].resp_retcode = PAM_SUCCESS;
reply[i].resp = NULL;
break;
default: /* unknown message style */
free(reply);
return PAM_CONV_ERR;
}
}
*resp = reply;
return PAM_SUCCESS;
}
/*
* The PAM version as a side effect may put a new username in *name.
*/
static int
check_user(char *name, char *cred)
{
pam_handle_t *pamh = NULL;
const void *item;
int rval;
int e;
cred_t auth_cred = { name, cred };
struct pam_conv conv = { &auth_conv, &auth_cred };
e = pam_start("telnetd", name, &conv, &pamh);
if (e != PAM_SUCCESS) {
syslog(LOG_ERR, "pam_start: %s", pam_strerror(pamh, e));
return 0;
}
#if 0 /* Where can we find this value? */
e = pam_set_item(pamh, PAM_RHOST, remotehost);
if (e != PAM_SUCCESS) {
syslog(LOG_ERR, "pam_set_item(PAM_RHOST): %s",
pam_strerror(pamh, e));
return 0;
}
#endif
e = pam_authenticate(pamh, 0);
switch (e) {
case PAM_SUCCESS:
/*
* With PAM we support the concept of a "template"
* user. The user enters a login name which is
* authenticated by PAM, usually via a remote service
* such as RADIUS or TACACS+. If authentication
* succeeds, a different but related "template" name
* is used for setting the credentials, shell, and
* home directory. The name the user enters need only
* exist on the remote authentication server, but the
* template name must be present in the local password
* database.
*
* This is supported by two various mechanisms in the
* individual modules. However, from the application's
* point of view, the template user is always passed
* back as a changed value of the PAM_USER item.
*/
if ((e = pam_get_item(pamh, PAM_USER, &item)) ==
PAM_SUCCESS) {
strcpy(name, item);
} else
syslog(LOG_ERR, "Couldn't get PAM_USER: %s",
pam_strerror(pamh, e));
if (isroot(name) && !rootterm(line))
rval = 0;
else
rval = 1;
break;
case PAM_AUTH_ERR:
case PAM_USER_UNKNOWN:
case PAM_MAXTRIES:
rval = 0;
break;
default:
syslog(LOG_ERR, "auth_pam: %s", pam_strerror(pamh, e));
rval = 0;
break;
}
if ((e = pam_end(pamh, e)) != PAM_SUCCESS) {
syslog(LOG_ERR, "pam_end: %s", pam_strerror(pamh, e));
rval = 0;
}
return rval;
}
#endif
#endif /* ENCRYPTION */
#endif /* SRA */
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