/* Subject: general purpose telnet server.
This is a telnet bouncer that some people have expressed interest in.
It's uses are utility and privacy related. It should compile easily on
most OS's striaght out of it's wrapper as such.

Mark
mark@cairo.anu.edu.au
*/
/* Name: ts2.c */
/* Author: Hal-9000, Xanadude, Richard Stevens, Avalon, Mark */
/* Distribution: Public */
/* Copyright: Held by the respective contributors */
/* Posted to USENET September '93 by Mark mark@cairo.anu.edu.au */

/* This file was telserv.c, part of the Telnet Server package v. 1.0,
     written by "Hal-9000". Much of that package was developed by Richard
     Stephens and his thanks go to "Xanadude" for providing him with that
     section. Performance fix by Darren Reed. */

/* Reworked to add concurrency, password checking and destination selection
   on the fly. - Mark 31st Aug 93

   Compiled and tested on:
       HPUX 9.01 9000/700 series        NeXTStep 3.1 NeXT 68040
       OSx Pyramid 90x BSD universe     SunOS 5.2 sun4c
       Ultrix 4.3 DEC RISC              Linux 0.99.10 80486

   To compile, type "cc -O -s ts2.c -o ts2".

   MY_PASSWORD and SERV_TCP_PORT are all that is required to be altered. */

#define    MY_PASSWORD    "bollox"
#define    SERV_TCP_PORT  9090    /* port I'll listen for connections on */

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <errno.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <sys/ioctl.h>

#define    QLEN           5

char sbuf[2048], cbuf[2048];
extern int errno;
extern char *sys_errlist[];
void reaper();
int main();
void telcli();

int main(argc, argv)
int argc;
char *argv[];
{
    int srv_fd, rem_fd, rem_len, opt = 1;
    struct sockaddr_in rem_addr, srv_addr;
#if !defined(SVR4) && !defined(POSIX) && !defined(linux) && !defined(__386BSD__) && !defined(hpux)
    union wait status;
#else
    int    status;
#endif /* !defined(SVR4) */

    bzero((char *) &rem_addr, sizeof(rem_addr));
    bzero((char *) &srv_addr, sizeof(srv_addr));
    srv_addr.sin_family = AF_INET;
    srv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    srv_addr.sin_port = htons(SERV_TCP_PORT);
    srv_fd = socket(PF_INET, SOCK_STREAM, 0);
    if (bind(srv_fd, (struct sockaddr *) &srv_addr, sizeof(srv_addr)) == -1) {
        perror("bind");
        exit(-1);
    }
    listen(srv_fd, QLEN);
    close(0); close(1); close(2);
#ifdef TIOCNOTTY
    if ((rem_fd = open("/dev/tty", O_RDWR)) >= 0) {
        ioctl(rem_fd, TIOCNOTTY, (char *)0);
        close(rem_fd);
    }
#endif
    if (fork()) exit(0);
    while (1) {
    rem_len = sizeof(rem_addr);
        rem_fd=accept(srv_fd, (struct sockaddr *) &rem_addr, &rem_len);
        if (rem_fd < 0) {
            if (errno == EINTR) continue;
            exit(-1);
        }
        switch(fork()) {
        case 0:                             /* child process */
            close(srv_fd);                  /* close original socket */
            telcli(rem_fd);                 /* process the request */
            close(rem_fd);
            exit(0);
            break;
        default: 
            close(rem_fd);                  /* parent process */
            if (fork()) exit(0);            /* let init worry about children */
            break;
        case -1:
            fprintf(stderr, "\n\rfork: %s\n\r", sys_errlist[errno]);
            break;
        }
    }
}

void telcli(source)
int source;
{
    int dest;
    int found;
    struct sockaddr_in sa;
    struct hostent *hp;
    struct servent *sp;
    char gethost[100];
    char getport[100];
    char string[100];

    bzero(gethost, 100);
    sprintf(string, "Password: ");
    write(source, string, strlen(string));
    read(source, gethost, 100);
    gethost[(strlen(gethost)-2)] = '\0'; /* kludge alert - kill the \r\n */
    if (strcmp(gethost, MY_PASSWORD) != 0) {
        sprintf(string, "Wrong password, got %s.\n", gethost);
        write(source, string, strlen(string));
        close(source);
        exit(0);
    }
    do {
        found = 0;
        bzero(gethost,100);
        sprintf(string, "Host: ");
        write(source, string, strlen(string));
        read(source, gethost, 100);
        gethost[(strlen(gethost)-2)] = '\0';
        hp = gethostbyname(gethost);
        if (hp) {
            found++;
#if !defined(h_addr)        /* In 4.3, this is a #define */
#if defined(hpux) || defined(NeXT) || defined(ultrix) || defined(POSIX)
            memcpy((caddr_t)&sa.sin_addr, hp->h_addr_list[0], hp->h_length);
#else
            bcopy(hp->h_addr_list[0], &sa.sin_addr, hp->h_length);
#endif
#else /* defined(h_addr) */
#if defined(hpux) || defined(NeXT) || defined(ultrix) || defined(POSIX)
            memcpy((caddr_t)&sa.sin_addr, hp->h_addr, hp->h_length);
#else
            bcopy(hp->h_addr, &sa.sin_addr, hp->h_length);
#endif
#endif /* defined(h_addr) */
            sprintf(string, "Found address for %s\n", hp->h_name);
            write(source, string, strlen(string));
        } else {
            if (inet_addr(gethost) == -1) {
                found = 0;
                sprintf(string, "Didnt find address for %s\n", gethost);
                write(source, string, strlen(string));
            } else {
                found++;
                sa.sin_addr.s_addr = inet_addr(gethost);
            }
        }
    } while (!found);
    sa.sin_family = AF_INET;
    sprintf(string, "Port: ");
    write(source, string, strlen(string));
    read(source, getport, 100);
    gethost[(strlen(getport)-2)] = '\0';
    sa.sin_port = htons((unsigned) atoi(getport));
    if (sa.sin_port == 0) {
        sp = getservbyname(getport, "tcp");
        if (sp)
            sa.sin_port = sp->s_port;
        else {
            sprintf(string, "%s: bad port number\n", getport);
            write(source, string, strlen(string));
            return;
        }
    }
    sprintf(string, "Trying %s...\n", (char *) inet_ntoa(sa.sin_addr));
    write(source, string, strlen(string));
    if ((dest = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
        perror("telcli: socket");
        exit(1);
    }
    connect(dest, (struct sockaddr *) &sa, sizeof(sa));
    sprintf(string, "Connected to %s port %d...\n", inet_ntoa(sa.sin_addr),
                                                          ntohs(sa.sin_port));
    write(source, string, strlen(string));
#ifdef FNDELAY
    fcntl(source,F_SETFL,fcntl(source,F_GETFL,0)|FNDELAY);
    fcntl(dest,F_SETFL,fcntl(dest,F_GETFL,0)|FNDELAY);
#else
    fcntl(source,F_SETFL,O_NDELAY);
    fcntl(dest,F_SETFL,O_NDELAY);
#endif
    communicate(dest,source);
    close(dest);
    exit(0);
}

communicate(sfd,cfd)    {
    char *chead, *ctail, *shead, *stail;
    int num, nfd, spos, cpos;
    extern int errno;
    fd_set rd, wr;

    chead = ctail = cbuf;
    cpos = 0;
    shead = stail = sbuf;
    spos = 0;
    while (1) {
        FD_ZERO(&rd);
        FD_ZERO(&wr);
        if (spos < sizeof(sbuf)-1) FD_SET(sfd, &rd);
        if (ctail > chead) FD_SET(sfd, &wr);
        if (cpos < sizeof(cbuf)-1) FD_SET(cfd, &rd);
        if (stail > shead) FD_SET(cfd, &wr);
        nfd = select(256, &rd, &wr, 0, 0);
        if (nfd <= 0) continue;
        if (FD_ISSET(sfd, &rd)) {
            num=read(sfd,stail,sizeof(sbuf)-spos);
            if ((num==-1) && (errno != EWOULDBLOCK)) return;
            if (num==0) return;
            if (num>0) {
                spos += num;
                stail += num;
                if (!--nfd) continue;
            }
        }
        if (FD_ISSET(cfd, &rd)) {
            num=read(cfd,ctail,sizeof(cbuf)-cpos);
            if ((num==-1) && (errno != EWOULDBLOCK)) return;
            if (num==0) return;
            if (num>0) {
                cpos += num;
                ctail += num;
                if (!--nfd) continue;
            }
        }
        if (FD_ISSET(sfd, &wr)) {
            num=write(sfd,chead,ctail-chead);
            if ((num==-1) && (errno != EWOULDBLOCK)) return;
            if (num>0) {
                chead += num;
                if (chead == ctail) {
                    chead = ctail = cbuf;
                    cpos = 0;
                }
                if (!--nfd) continue;
            }
        }
        if (FD_ISSET(cfd, &wr)) {
            num=write(cfd,shead,stail-shead);
            if ((num==-1) && (errno != EWOULDBLOCK)) return;
            if (num>0) {
                shead += num;
                if (shead == stail) {
                    shead = stail = sbuf;
                    spos = 0;
                }
                if (!--nfd) continue;
            }
        }
    }
}