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/*
* This module determines the type of socket (datagram, stream), the client
* socket address and port, the server socket address and port. In addition,
* it provides methods to map a transport address to a printable host name
* or address. Socket address information results are in static memory.
*
* The result from the hostname lookup method is STRING_PARANOID when a host
* pretends to have someone elses name, or when a host name is available but
* could not be verified.
*
* When lookup or conversion fails the result is set to STRING_UNKNOWN.
*
* Diagnostics are reported through syslog(3).
*
* Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
*/
#ifndef lint
static char sccsid[] = "@(#) socket.c 1.15 97/03/21 19:27:24";
#endif
/* System libraries. */
#include <sys/types.h>
#include <sys/param.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>
#include <syslog.h>
#include <string.h>
extern char *inet_ntoa();
/* Local stuff. */
#include "tcpd.h"
/* Forward declarations. */
static void sock_sink();
#ifdef APPEND_DOT
/*
* Speed up DNS lookups by terminating the host name with a dot. Should be
* done with care. The speedup can give problems with lookups from sources
* that lack DNS-style trailing dot magic, such as local files or NIS maps.
*/
static struct hostent *gethostbyname_dot(name)
char *name;
{
char dot_name[MAXHOSTNAMELEN + 1];
/*
* Don't append dots to unqualified names. Such names are likely to come
* from local hosts files or from NIS.
*/
if (strchr(name, '.') == 0 || strlen(name) >= MAXHOSTNAMELEN - 1) {
return (gethostbyname(name));
} else {
sprintf(dot_name, "%s.", name);
return (gethostbyname(dot_name));
}
}
#define gethostbyname gethostbyname_dot
#endif
/* sock_host - look up endpoint addresses and install conversion methods */
void sock_host(request)
struct request_info *request;
{
static struct sockaddr_in client;
static struct sockaddr_in server;
int len;
char buf[BUFSIZ];
int fd = request->fd;
sock_methods(request);
/*
* Look up the client host address. Hal R. Brand <BRAND@addvax.llnl.gov>
* suggested how to get the client host info in case of UDP connections:
* peek at the first message without actually looking at its contents. We
* really should verify that client.sin_family gets the value AF_INET,
* but this program has already caused too much grief on systems with
* broken library code.
*/
len = sizeof(client);
if (getpeername(fd, (struct sockaddr *) & client, &len) < 0) {
request->sink = sock_sink;
len = sizeof(client);
if (recvfrom(fd, buf, sizeof(buf), MSG_PEEK,
(struct sockaddr *) & client, &len) < 0) {
tcpd_warn("can't get client address: %m");
return; /* give up */
}
#ifdef really_paranoid
memset(buf, 0 sizeof(buf));
#endif
}
request->client->sin = &client;
/*
* Determine the server binding. This is used for client username
* lookups, and for access control rules that trigger on the server
* address or name.
*/
len = sizeof(server);
if (getsockname(fd, (struct sockaddr *) & server, &len) < 0) {
tcpd_warn("getsockname: %m");
return;
}
request->server->sin = &server;
}
/* sock_hostaddr - map endpoint address to printable form */
void sock_hostaddr(host)
struct host_info *host;
{
struct sockaddr_in *sin = host->sin;
if (sin != 0)
STRN_CPY(host->addr, inet_ntoa(sin->sin_addr), sizeof(host->addr));
}
/* sock_hostname - map endpoint address to host name */
void sock_hostname(host)
struct host_info *host;
{
struct sockaddr_in *sin = host->sin;
struct hostent *hp;
int i;
/*
* On some systems, for example Solaris 2.3, gethostbyaddr(0.0.0.0) does
* not fail. Instead it returns "INADDR_ANY". Unfortunately, this does
* not work the other way around: gethostbyname("INADDR_ANY") fails. We
* have to special-case 0.0.0.0, in order to avoid false alerts from the
* host name/address checking code below.
*/
if (sin != 0 && sin->sin_addr.s_addr != 0
&& (hp = gethostbyaddr((char *) &(sin->sin_addr),
sizeof(sin->sin_addr), AF_INET)) != 0) {
STRN_CPY(host->name, hp->h_name, sizeof(host->name));
/*
* Verify that the address is a member of the address list returned
* by gethostbyname(hostname).
*
* Verify also that gethostbyaddr() and gethostbyname() return the same
* hostname, or rshd and rlogind may still end up being spoofed.
*
* On some sites, gethostbyname("localhost") returns "localhost.domain".
* This is a DNS artefact. We treat it as a special case. When we
* can't believe the address list from gethostbyname("localhost")
* we're in big trouble anyway.
*/
if ((hp = gethostbyname(host->name)) == 0) {
/*
* Unable to verify that the host name matches the address. This
* may be a transient problem or a botched name server setup.
*/
tcpd_warn("can't verify hostname: gethostbyname(%s) failed",
host->name);
} else if (STR_NE(host->name, hp->h_name)
&& STR_NE(host->name, "localhost")) {
/*
* The gethostbyaddr() and gethostbyname() calls did not return
* the same hostname. This could be a nameserver configuration
* problem. It could also be that someone is trying to spoof us.
*/
tcpd_warn("host name/name mismatch: %s != %.*s",
host->name, STRING_LENGTH, hp->h_name);
} else {
/*
* The address should be a member of the address list returned by
* gethostbyname(). We should first verify that the h_addrtype
* field is AF_INET, but this program has already caused too much
* grief on systems with broken library code.
*/
for (i = 0; hp->h_addr_list[i]; i++) {
if (memcmp(hp->h_addr_list[i],
(char *) &sin->sin_addr,
sizeof(sin->sin_addr)) == 0)
return; /* name is good, keep it */
}
/*
* The host name does not map to the initial address. Perhaps
* someone has messed up. Perhaps someone compromised a name
* server.
*/
tcpd_warn("host name/address mismatch: %s != %.*s",
inet_ntoa(sin->sin_addr), STRING_LENGTH, hp->h_name);
}
strcpy(host->name, paranoid); /* name is bad, clobber it */
}
}
/* sock_sink - absorb unreceived IP datagram */
static void sock_sink(fd)
int fd;
{
char buf[BUFSIZ];
struct sockaddr_in sin;
int size = sizeof(sin);
/*
* Eat up the not-yet received datagram. Some systems insist on a
* non-zero source address argument in the recvfrom() call below.
*/
(void) recvfrom(fd, buf, sizeof(buf), 0, (struct sockaddr *) & sin, &size);
}
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