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/*
* rfc931() speaks a common subset of the RFC 931, AUTH, TAP and IDENT
* protocols. The code 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.
*/
#include "config.h"
#include "portability.h"
#ifndef lint
static char sccsid[] = "@(#) rfc931.c 1.8 93/12/13 22:23:20";
#endif /* lint */
#ifndef _HPUX_SOURCE
# define _HPUX_SOURCE
#endif /* _HPUX_SOURCE */
#ifdef SCO3
# define SIGALRM 14
#endif /* SCO3 */
/* System libraries. */
#include <stdio.h>
#ifndef ATTSVR3
# include <syslog.h>
#else
# define syslog(a,b) perror(b)
#endif /* ATTSVR3 */
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <setjmp.h>
#include <signal.h>
extern char *strchr();
extern char *inet_ntoa();
/* Local stuff. */
/* #include "log_tcp.h" */
#define RFC931_TIMEOUT 45
#define RFC931_PORT 113 /* Semi-well-known port */
#define ANY_PORT 0 /* Any old port will do */
#define FROM_UNKNOWN "unknown"
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(int domain, int type, int protocol)
{
int s;
FILE *fp;
if ((s = socket(domain, type, protocol)) < 0) {
syslog(LOG_ERR, "socket: %m");
return (0);
} else {
if ((fp = fdopen(s, "r+")) == 0) {
syslog(LOG_ERR, "fdopen: %m");
close(s);
}
return (fp);
}
}
/* bind_connect - bind both ends of a socket */
int bind_connect(int s, struct sockaddr* local, struct sockaddr* remote,
int length)
{
if (bind(s, local, length) < 0) {
syslog(LOG_ERR, "bind: %m");
return (-1);
} else {
return (connect(s, remote, length));
}
}
/* timeout - handle timeouts */
static void timeout(int sig)
{
longjmp(timebuf, sig);
}
/* rfc931 - return remote user name, given socket structures */
char *rfc931(struct sockaddr_in *rmt_sin, struct sockaddr_in *our_sin)
{
unsigned rmt_port;
unsigned our_port;
struct sockaddr_in rmt_query_sin;
struct sockaddr_in our_query_sin;
static char user[256]; /* XXX */
char buffer[512]; /* XXX */
char *cp;
char *result = FROM_UNKNOWN; /* XXX */
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_connect(fileno(fp),
(struct sockaddr *) & our_query_sin,
(struct sockaddr *) & rmt_query_sin,
sizeof(our_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.
*/
if ((cp = strchr(user, '\r')))
*cp = 0;
result = user;
}
}
alarm(0);
}
fclose(fp);
}
return (result);
}
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