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/* telnet.c -- basic telnet protocol handling for ttywatch
*
* Copyright © 2001 Michael K. Johnson <johnsonm@redhat.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
/* Shamelessly stolen from ttywatch -- oot */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include "telnet.h"
#include "log.h"
#define IAC "\xff"
#define DONT "\xfe"
#define WONT "\xfc"
#define WILL "\xfb"
#define DO "\xfd"
#define SB "\xfa"
#define SE "\xf0"
#define ECHO "\x01"
#define SUPPRESS_GO_AHEAD "\x03"
#define LINEMODE "\x22"
#define NEWENVIRON "\x27"
#define MODE "\x01"
/* Make a request. Not intended to be RFC-compatible, just enough
* to convince telnet clients to do what we want... To do this
* right, we would have to honestly negotiate, not speak blind.
*
* For now, assume all responses will be favorable and stripped
* out in telnet_process_input()... Sending it all in a single
* write makes it more efficient because it will all go out in a
* single packet, and the responses are more likely to all come
* back in a single packet (and thus, practically, a single read)
* too.
*/
void
telnet_negotiate(int socket) {
char request[]=
IAC DONT ECHO
IAC WILL ECHO
IAC WILL SUPPRESS_GO_AHEAD
IAC DO SUPPRESS_GO_AHEAD
IAC DONT NEWENVIRON
IAC WONT NEWENVIRON
IAC DO LINEMODE
IAC SB LINEMODE MODE "0" IAC SE
;
write(socket, request, sizeof(request)-1);
}
int
telnet_process_input(telnet_state * ts, char *data, int len) {
char *s, *d; /* source, destination */
# define DEBUG_TELNET 0
# if DEBUG_TELNET
printf("\nprinting packet:");
for (s=data; s<data+len; s++) {
if (!((s-data)%10))
printf("\n %03d: ", s-data);
printf("%02x ", *s & 0x000000FF);
}
printf("\n");
# endif /* DEBUG_TELNET */
for (s=data, d=data; s<data+len; s++) {
switch (*ts) {
case TS_DATA:
if (*s == '\xff') { /* IAC */
*ts = TS_IAC;
continue;
}
#if DEBUG_TELNET
printf("copying data element '%c'\n", *s);
#endif /* DEBUG_TELNET */
if (s>d) {
*(d++) = *s;
} else {
d++;
}
break;
case TS_IAC:
if (*s == '\xfa') { /* SB */
*ts = TS_SB;
continue;
}
/* if not SB, skip IAC verb object */
# if DEBUG_TELNET
printf("skipping verb/object (offset %d)...\n", s-data-1);
# endif /* DEBUG_TELNET */
s += 1;
*ts = TS_DATA;
break;
case TS_SB:
# if DEBUG_TELNET
printf("skipping SB (offset %d)...\n", s-data-1);
# endif /* DEBUG_TELNET */
while (s < (data+(len-1))) {
if (*s == '\xff') {
break; /* fall through to TS_SB_IAC setting below */
} else {
s++;
}
}
if (*s == '\xff') {
*ts = TS_SB_IAC;
}
break;
case TS_SB_IAC:
if (*s == '\xf0') { /* SE */
# if DEBUG_TELNET
printf("SE ends SB (offset %d)...\n", s-data-1);
# endif /* DEBUG_TELNET */
*ts = TS_DATA;
} else {
# if DEBUG_TELNET
printf("IAC without SE in SB\n");
# endif /* DEBUG_TELNET */
*ts = TS_SB;
}
break;
default:
logMessage("unknown telnet state %d for data element %c", *ts, *s);
*ts = TS_DATA;
break;
}
}
/* calculate new length after copying data around */
len = d - data;
#if DEBUG_TELNET
printf("returning len: %d of packet:", len);
for (s=data; s<data+len; s++) {
if (!((s-data)%10))
printf("\n %03d: ", s-data);
printf("%02x ", *s & 0x000000FF);
}
printf("\n");
#endif /* DEBUG_TELNET */
return len;
}
/* The telnet protocol requires CR/NL instead of just NL
* We normally deal with Unix, which just uses NL, so we need to translate.
*
* It would be easy to go through line-by-line and write each line, but
* that would create more packet overhead by sending out one packet
* per line, and over things like slow PPP connections, that is painful.
* Therefore, instead, we create a modified copy of the data and write
* the whole modified copy at once.
*/
void
telnet_send_output(int sock, char *data, int len) {
char *s, *d; /* source, destination */
char *buf;
buf = alloca((len*2)+1); /* max necessary size */
/* just may need to add CR before NL (but do not double existing CRs) */
for (s=data, d=buf; d-buf<len; s++, d++) {
if ((*s == '\n') && (s == data || (*(s-1) != '\r'))) {
/* NL without preceding CR */
*(d++) = '\r';
len++;
}
*d = *s;
}
/* now send it... */
write(sock, buf, len);
}
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