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/* $OpenBSD: rfc931.c,v 1.1 1997/02/26 03:06:56 downsj Exp $ */
/*
* rfc931() speaks a common subset of the RFC 931, AUTH, TAP, IDENT and RFC
* 1413 protocols. It queries an RFC 931 etc. compatible daemon on a remote
* host to look up the owner of a connection. The information should not be
* used for authentication purposes. This routine intercepts alarm signals.
*
* Diagnostics are reported through syslog(3).
*
* Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
*/
#ifndef lint
#if 0
static char sccsid[] = "@(#) rfc931.c 1.10 95/01/02 16:11:34";
#else
static char rcsid[] = "$OpenBSD: rfc931.c,v 1.1 1997/02/26 03:06:56 downsj Exp $";
#endif
#endif
/* System libraries. */
#include <stdio.h>
#include <syslog.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <setjmp.h>
#include <signal.h>
#include <string.h>
#include <unistd.h>
/* Local stuff. */
#include "tcpd.h"
#define RFC931_PORT 113 /* Semi-well-known port */
#define ANY_PORT 0 /* Any old port will do */
int rfc931_timeout = RFC931_TIMEOUT;/* Global so it can be changed */
static jmp_buf timebuf;
/* fsocket - open stdio stream on top of socket */
static FILE *fsocket(domain, type, protocol)
int domain;
int type;
int protocol;
{
int s;
FILE *fp;
if ((s = socket(domain, type, protocol)) < 0) {
tcpd_warn("socket: %m");
return (0);
} else {
if ((fp = fdopen(s, "r+")) == 0) {
tcpd_warn("fdopen: %m");
close(s);
}
return (fp);
}
}
/* timeout - handle timeouts */
static void timeout(sig)
int sig;
{
longjmp(timebuf, sig);
}
/* rfc931 - return remote user name, given socket structures */
void rfc931(rmt_sin, our_sin, dest)
struct sockaddr_in *rmt_sin;
struct sockaddr_in *our_sin;
char *dest;
{
unsigned rmt_port;
unsigned our_port;
struct sockaddr_in rmt_query_sin;
struct sockaddr_in our_query_sin;
char user[256]; /* XXX */
char buffer[512]; /* XXX */
char *cp;
char *result = unknown;
FILE *fp;
/*
* Use one unbuffered stdio stream for writing to and for reading from
* the RFC931 etc. server. This is done because of a bug in the SunOS
* 4.1.x stdio library. The bug may live in other stdio implementations,
* too. When we use a single, buffered, bidirectional stdio stream ("r+"
* or "w+" mode) we read our own output. Such behaviour would make sense
* with resources that support random-access operations, but not with
* sockets.
*/
if ((fp = fsocket(AF_INET, SOCK_STREAM, 0)) != 0) {
setbuf(fp, (char *) 0);
/*
* Set up a timer so we won't get stuck while waiting for the server.
*/
if (setjmp(timebuf) == 0) {
signal(SIGALRM, timeout);
alarm(rfc931_timeout);
/*
* Bind the local and remote ends of the query socket to the same
* IP addresses as the connection under investigation. We go
* through all this trouble because the local or remote system
* might have more than one network address. The RFC931 etc.
* client sends only port numbers; the server takes the IP
* addresses from the query socket.
*/
our_query_sin = *our_sin;
our_query_sin.sin_port = htons(ANY_PORT);
rmt_query_sin = *rmt_sin;
rmt_query_sin.sin_port = htons(RFC931_PORT);
if (bind(fileno(fp), (struct sockaddr *) & our_query_sin,
sizeof(our_query_sin)) >= 0 &&
connect(fileno(fp), (struct sockaddr *) & rmt_query_sin,
sizeof(rmt_query_sin)) >= 0) {
/*
* Send query to server. Neglect the risk that a 13-byte
* write would have to be fragmented by the local system and
* cause trouble with buggy System V stdio libraries.
*/
fprintf(fp, "%u,%u\r\n",
ntohs(rmt_sin->sin_port),
ntohs(our_sin->sin_port));
fflush(fp);
/*
* Read response from server. Use fgets()/sscanf() so we can
* work around System V stdio libraries that incorrectly
* assume EOF when a read from a socket returns less than
* requested.
*/
if (fgets(buffer, sizeof(buffer), fp) != 0
&& ferror(fp) == 0 && feof(fp) == 0
&& sscanf(buffer, "%u , %u : USERID :%*[^:]:%255s",
&rmt_port, &our_port, user) == 3
&& ntohs(rmt_sin->sin_port) == rmt_port
&& ntohs(our_sin->sin_port) == our_port) {
/*
* Strip trailing carriage return. It is part of the
* protocol, not part of the data.
*/
cp = strchr(user, '\r');
if (cp)
*cp = 0;
result = user;
}
}
alarm(0);
}
fclose(fp);
}
STRN_CPY(dest, result, STRING_LENGTH);
}
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