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0f8c8396c5
SRA does a Diffie-Hellmen exchange and then DES-encrypts the authentication data. If the authentication is successful, it also sets up a session key for DES encryption. SRA was originally developed at Texas A&M University. This code is probably export restricted (despite the fact that I originally found it at a University in Germany). SRA is not perfect. It is vulnerable to monkey-in-the-middle attacks and does not use tremendously large DH constants (and thus an individual exchange probably could be factored in a few days on modern CPU horsepower). It does not, however, require any changes in user or administrative behavior and foils session hijacking and sniffing. The goal of this commit is that telnet and telnetd end up in the DES distribution and that therefore an encrypted session telnet becomes standard issue for FreeBSD.
479 lines
9.4 KiB
C
479 lines
9.4 KiB
C
#ifdef SRA
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#include <sys/types.h>
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#include <arpa/telnet.h>
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#include <stdio.h>
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#ifdef __STDC__
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#include <stdlib.h>
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#endif
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#ifdef NO_STRING_H
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#include <strings.h>
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#else
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#include <string.h>
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#endif
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#include "auth.h"
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#include "misc.h"
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#include "encrypt.h"
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#include "pk.h"
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char pka[HEXKEYBYTES+1], ska[HEXKEYBYTES+1], pkb[HEXKEYBYTES+1];
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char *user,*pass,*xuser,*xpass;
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DesData ck;
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IdeaData ik;
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extern int auth_debug_mode;
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static sra_valid = 0;
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static passwd_sent = 0;
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static unsigned char str_data[1024] = { IAC, SB, TELOPT_AUTHENTICATION, 0,
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AUTHTYPE_SRA, };
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#define SRA_KEY 0
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#define SRA_USER 1
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#define SRA_CONTINUE 2
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#define SRA_PASS 3
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#define SRA_ACCEPT 4
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#define SRA_REJECT 5
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/* support routine to send out authentication message */
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static int Data(ap, type, d, c)
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Authenticator *ap;
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int type;
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void *d;
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int c;
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{
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unsigned char *p = str_data + 4;
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unsigned char *cd = (unsigned char *)d;
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if (c == -1)
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c = strlen((char *)cd);
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if (auth_debug_mode) {
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printf("%s:%d: [%d] (%d)",
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str_data[3] == TELQUAL_IS ? ">>>IS" : ">>>REPLY",
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str_data[3],
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type, c);
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printd(d, c);
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printf("\r\n");
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}
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*p++ = ap->type;
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*p++ = ap->way;
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*p++ = type;
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while (c-- > 0) {
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if ((*p++ = *cd++) == IAC)
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*p++ = IAC;
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}
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*p++ = IAC;
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*p++ = SE;
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if (str_data[3] == TELQUAL_IS)
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printsub('>', &str_data[2], p - (&str_data[2]));
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return(net_write(str_data, p - str_data));
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}
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int sra_init(ap, server)
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Authenticator *ap;
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int server;
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{
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if (server)
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str_data[3] = TELQUAL_REPLY;
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else
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str_data[3] = TELQUAL_IS;
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user = (char *)malloc(256);
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xuser = (char *)malloc(512);
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pass = (char *)malloc(256);
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xpass = (char *)malloc(512);
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passwd_sent = 0;
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genkeys(pka,ska);
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return(1);
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}
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/* client received a go-ahead for sra */
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int sra_send(ap)
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Authenticator *ap;
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{
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/* send PKA */
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if (auth_debug_mode)
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printf("Sent PKA to server.\r\n" );
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printf("Trying SRA secure login:\r\n");
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if (!Data(ap, SRA_KEY, (void *)pka, HEXKEYBYTES)) {
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if (auth_debug_mode)
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printf("Not enough room for authentication data\r\n");
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return(0);
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}
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return(1);
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}
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/* server received an IS -- could be SRA KEY, USER, or PASS */
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void sra_is(ap, data, cnt)
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Authenticator *ap;
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unsigned char *data;
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int cnt;
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{
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int valid;
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Session_Key skey;
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if (cnt-- < 1)
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return;
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switch (*data++) {
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case SRA_KEY:
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if (cnt < HEXKEYBYTES) {
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Data(ap, SRA_REJECT, (void *)0, 0);
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auth_finished(ap, AUTH_USER);
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if (auth_debug_mode) {
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printf("SRA user rejected for bad PKB\r\n");
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}
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return;
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}
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if (auth_debug_mode)
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printf("Sent pka\r\n");
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if (!Data(ap, SRA_KEY, (void *)pka, HEXKEYBYTES)) {
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if (auth_debug_mode)
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printf("Not enough room\r\n");
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return;
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}
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memcpy(pkb,data,HEXKEYBYTES);
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pkb[HEXKEYBYTES] = '\0';
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common_key(ska,pkb,&ik,&ck);
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break;
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case SRA_USER:
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/* decode KAB(u) */
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memcpy(xuser,data,cnt);
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xuser[cnt] = '\0';
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pk_decode(xuser,user,&ck);
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auth_encrypt_user(user);
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Data(ap, SRA_CONTINUE, (void *)0, 0);
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break;
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case SRA_PASS:
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/* decode KAB(P) */
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memcpy(xpass,data,cnt);
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xpass[cnt] = '\0';
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pk_decode(xpass,pass,&ck);
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/* check user's password */
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valid = check_user(user,pass);
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if(valid) {
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Data(ap, SRA_ACCEPT, (void *)0, 0);
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#ifdef DES_ENCRYPTION
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skey.data = ck;
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skey.type = SK_DES;
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skey.length = 8;
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encrypt_session_key(&skey, 1);
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#endif
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sra_valid = 1;
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auth_finished(ap, AUTH_VALID);
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if (auth_debug_mode) {
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printf("SRA user accepted\r\n");
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}
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}
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else {
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Data(ap, SRA_CONTINUE, (void *)0, 0);
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/*
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Data(ap, SRA_REJECT, (void *)0, 0);
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sra_valid = 0;
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auth_finished(ap, AUTH_REJECT);
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*/
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if (auth_debug_mode) {
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printf("SRA user failed\r\n");
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}
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}
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break;
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default:
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if (auth_debug_mode)
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printf("Unknown SRA option %d\r\n", data[-1]);
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Data(ap, SRA_REJECT, 0, 0);
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sra_valid = 0;
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auth_finished(ap, AUTH_REJECT);
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break;
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}
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}
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extern char *getpass();
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/* client received REPLY -- could be SRA KEY, CONTINUE, ACCEPT, or REJECT */
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void sra_reply(ap, data, cnt)
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Authenticator *ap;
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unsigned char *data;
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int cnt;
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{
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extern char *telnet_gets();
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char uprompt[256],tuser[256];
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Session_Key skey;
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int i;
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if (cnt-- < 1)
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return;
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switch (*data++) {
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case SRA_KEY:
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/* calculate common key */
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if (cnt < HEXKEYBYTES) {
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if (auth_debug_mode) {
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printf("SRA user rejected for bad PKB\r\n");
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}
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return;
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}
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memcpy(pkb,data,HEXKEYBYTES);
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pkb[HEXKEYBYTES] = '\0';
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common_key(ska,pkb,&ik,&ck);
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enc_user:
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/* encode user */
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memset(tuser,0,sizeof(tuser));
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sprintf(uprompt,"User (%s): ",UserNameRequested);
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telnet_gets(uprompt,tuser,255,1);
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if (tuser[0] == '\n' || tuser[0] == '\r' )
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strcpy(user,UserNameRequested);
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else {
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/* telnet_gets leaves the newline on */
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for(i=0;i<sizeof(tuser);i++) {
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if (tuser[i] == '\n') {
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tuser[i] = '\0';
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break;
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}
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}
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strcpy(user,tuser);
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}
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pk_encode(user,xuser,&ck);
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/* send it off */
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if (auth_debug_mode)
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printf("Sent KAB(U)\r\n");
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if (!Data(ap, SRA_USER, (void *)xuser, strlen(xuser))) {
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if (auth_debug_mode)
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printf("Not enough room\r\n");
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return;
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}
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break;
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case SRA_CONTINUE:
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if (passwd_sent) {
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passwd_sent = 0;
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printf("[ SRA login failed ]\r\n");
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goto enc_user;
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}
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/* encode password */
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memset(pass,0,sizeof(pass));
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telnet_gets("Password: ",pass,255,0);
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pk_encode(pass,xpass,&ck);
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/* send it off */
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if (auth_debug_mode)
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printf("Sent KAB(P)\r\n");
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if (!Data(ap, SRA_PASS, (void *)xpass, strlen(xpass))) {
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if (auth_debug_mode)
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printf("Not enough room\r\n");
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return;
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}
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passwd_sent = 1;
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break;
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case SRA_REJECT:
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printf("[ SRA refuses authentication ]\r\n");
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printf("Trying plaintext login:\r\n");
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auth_finished(0,AUTH_REJECT);
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return;
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case SRA_ACCEPT:
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printf("[ SRA accepts you ]\r\n");
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#ifdef DES_ENCRYPTION
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skey.data = ck;
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skey.type = SK_DES;
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skey.length = 8;
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encrypt_session_key(&skey, 0);
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#endif
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auth_finished(ap, AUTH_VALID);
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return;
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default:
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if (auth_debug_mode)
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printf("Unknown SRA option %d\r\n", data[-1]);
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return;
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}
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}
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int sra_status(ap, name, level)
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Authenticator *ap;
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char *name;
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int level;
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{
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if (level < AUTH_USER)
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return(level);
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if (UserNameRequested && sra_valid) {
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strcpy(name, UserNameRequested);
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return(AUTH_VALID);
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} else
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return(AUTH_USER);
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}
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#define BUMP(buf, len) while (*(buf)) {++(buf), --(len);}
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#define ADDC(buf, len, c) if ((len) > 0) {*(buf)++ = (c); --(len);}
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void sra_printsub(data, cnt, buf, buflen)
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unsigned char *data, *buf;
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int cnt, buflen;
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{
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char lbuf[32];
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register int i;
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buf[buflen-1] = '\0'; /* make sure its NULL terminated */
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buflen -= 1;
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switch(data[3]) {
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case SRA_CONTINUE:
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strncpy((char *)buf, " CONTINUE ", buflen);
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goto common;
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case SRA_REJECT: /* Rejected (reason might follow) */
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strncpy((char *)buf, " REJECT ", buflen);
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goto common;
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case SRA_ACCEPT: /* Accepted (name might follow) */
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strncpy((char *)buf, " ACCEPT ", buflen);
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common:
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BUMP(buf, buflen);
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if (cnt <= 4)
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break;
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ADDC(buf, buflen, '"');
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for (i = 4; i < cnt; i++)
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ADDC(buf, buflen, data[i]);
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ADDC(buf, buflen, '"');
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ADDC(buf, buflen, '\0');
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break;
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case SRA_KEY: /* Authentication data follows */
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strncpy((char *)buf, " KEY ", buflen);
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goto common2;
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case SRA_USER:
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strncpy((char *)buf, " USER ", buflen);
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goto common2;
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case SRA_PASS:
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strncpy((char *)buf, " PASS ", buflen);
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goto common2;
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default:
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sprintf(lbuf, " %d (unknown)", data[3]);
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strncpy((char *)buf, lbuf, buflen);
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common2:
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BUMP(buf, buflen);
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for (i = 4; i < cnt; i++) {
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sprintf(lbuf, " %d", data[i]);
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strncpy((char *)buf, lbuf, buflen);
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BUMP(buf, buflen);
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}
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break;
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}
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}
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struct passwd *pw;
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/*
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* Helper function for sgetpwnam().
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*/
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char *
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sgetsave(s)
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char *s;
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{
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char *new = malloc((unsigned) strlen(s) + 1);
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if (new == NULL) {
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return(NULL);
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}
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(void) strcpy(new, s);
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return (new);
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}
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#include <pwd.h>
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#include <syslog.h>
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#ifdef USE_SHADOW
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#include <shadow.h>
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#endif
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struct passwd *
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sgetpwnam(name)
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char *name;
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{
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static struct passwd save;
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register struct passwd *p;
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char *sgetsave();
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if ((p = getpwnam(name)) == NULL)
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return (p);
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if (save.pw_name) {
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free(save.pw_name);
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free(save.pw_passwd);
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free(save.pw_gecos);
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free(save.pw_dir);
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free(save.pw_shell);
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}
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save = *p;
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save.pw_name = sgetsave(p->pw_name);
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save.pw_passwd = sgetsave(p->pw_passwd);
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save.pw_gecos = sgetsave(p->pw_gecos);
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save.pw_dir = sgetsave(p->pw_dir);
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save.pw_shell = sgetsave(p->pw_shell);
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#if 0
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syslog(LOG_WARNING,"%s\n",save.pw_name);
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syslog(LOG_WARNING,"%s\n",save.pw_passwd);
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syslog(LOG_WARNING,"%s\n",save.pw_gecos);
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syslog(LOG_WARNING,"%s\n",save.pw_dir);
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#endif
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#ifdef USE_SHADOW
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{
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struct spwd *sp;
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sp = getspnam(name);
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free(save.pw_passwd);
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save.pw_passwd = sgetsave(sp->sp_pwdp);
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}
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#endif
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return (&save);
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}
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char *crypt();
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int check_user(name, pass)
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char *name;
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char *pass;
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{
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register char *cp;
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char *xpasswd, *salt;
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if (pw = sgetpwnam(name)) {
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if (pw->pw_shell == NULL) {
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pw = (struct passwd *) NULL;
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return(0);
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}
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salt = pw->pw_passwd;
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xpasswd = crypt(pass, salt);
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/* The strcmp does not catch null passwords! */
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if (pw == NULL || *pw->pw_passwd == '\0' ||
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strcmp(xpasswd, pw->pw_passwd)) {
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pw = (struct passwd *) NULL;
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return(0);
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}
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return(1);
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}
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return(0);
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}
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#endif
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