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/*
* pmap_check - additional portmap security.
*
* Always reject non-local requests to update the portmapper tables.
*
* Refuse to forward mount requests to the nfs mount daemon. Otherwise, the
* requests would appear to come from the local system, and nfs export
* restrictions could be bypassed.
*
* Refuse to forward requests to the nfsd process.
*
* Refuse to forward requests to NIS (YP) daemons; The only exception is the
* YPPROC_DOMAIN_NONACK broadcast rpc call that is used to establish initial
* contact with the NIS server.
*
* Always allocate an unprivileged port when forwarding a request.
*
* If compiled with -DCHECK_PORT, require that requests to register or
* unregister a privileged port come from a privileged port. This makes it
* more difficult to replace a critical service by a trojan.
*
* If compiled with -DHOSTS_ACCESS, reject requests from hosts that are not
* authorized by the /etc/hosts.{allow,deny} files. The local system is
* always treated as an authorized host. The access control tables are never
* consulted for requests from the local system, and are always consulted
* for requests from other hosts. Access control is based on IP addresses
* only; attempts to map an address to a host name might cause the
* portmapper to hang.
*
* Author: Wietse Venema (wietse@wzv.win.tue.nl), dept. of Mathematics and
* Computing Science, Eindhoven University of Technology, The Netherlands.
*/
#ifndef lint
#if 0
static char sccsid[] = "@(#) pmap_check.c 1.6 93/11/21 20:58:59";
#endif
static const char rcsid[] =
"$Id$";
#endif
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <rpc/rpc.h>
#include <rpc/pmap_prot.h>
#include <syslog.h>
#include <netdb.h>
#include <sys/signal.h>
#include "pmap_check.h"
/* Explicit #defines in case the include files are not available. */
#define NFSPROG ((u_long) 100003)
#define MOUNTPROG ((u_long) 100005)
#define YPXPROG ((u_long) 100069)
#define YPPROG ((u_long) 100004)
#define YPPROC_DOMAIN_NONACK ((u_long) 2)
#define MOUNTPROC_MNT ((u_long) 1)
static void logit();
static void toggle_verboselog();
int verboselog = 0;
int allow_severity = LOG_INFO;
int deny_severity = LOG_WARNING;
/* A handful of macros for "readability". */
#define good_client(a) hosts_ctl("portmap", "", inet_ntoa(a->sin_addr), "")
#define legal_port(a,p) \
(ntohs((a)->sin_port) < IPPORT_RESERVED || (p) >= IPPORT_RESERVED)
#define log_bad_port(addr, proc, prog) \
logit(deny_severity, addr, proc, prog, ": request from unprivileged port")
#define log_bad_host(addr, proc, prog) \
logit(deny_severity, addr, proc, prog, ": request from unauthorized host")
#define log_bad_owner(addr, proc, prog) \
logit(deny_severity, addr, proc, prog, ": request from non-local host")
#define log_no_forward(addr, proc, prog) \
logit(deny_severity, addr, proc, prog, ": request not forwarded")
#define log_client(addr, proc, prog) \
logit(allow_severity, addr, proc, prog, "")
/* check_startup - additional startup code */
void check_startup()
{
/*
* Give up root privileges so that we can never allocate a privileged
* port when forwarding an rpc request.
*/
if (setuid(1) == -1) {
syslog(LOG_ERR, "setuid(1) failed: %m");
exit(1);
}
(void) signal(SIGINT, toggle_verboselog);
}
/* check_default - additional checks for NULL, DUMP, GETPORT and unknown */
int
check_default(addr, proc, prog)
struct sockaddr_in *addr;
u_long proc;
u_long prog;
{
#ifdef HOSTS_ACCESS
if (!(from_local(addr) || good_client(addr))) {
log_bad_host(addr, proc, prog);
return (FALSE);
}
#endif
if (verboselog)
log_client(addr, proc, prog);
return (TRUE);
}
/* check_privileged_port - additional checks for privileged-port updates */
int
check_privileged_port(addr, proc, prog, port)
struct sockaddr_in *addr;
u_long proc;
u_long prog;
u_long port;
{
#ifdef CHECK_PORT
if (!legal_port(addr, port)) {
log_bad_port(addr, proc, prog);
return (FALSE);
}
#endif
return (TRUE);
}
/* check_setunset - additional checks for update requests */
int
check_setunset(addr, proc, prog, port)
struct sockaddr_in *addr;
u_long proc;
u_long prog;
u_long port;
{
if (!from_local(addr)) {
#ifdef HOSTS_ACCESS
(void) good_client(addr); /* because of side effects */
#endif
log_bad_owner(addr, proc, prog);
return (FALSE);
}
if (port && !check_privileged_port(addr, proc, prog, port))
return (FALSE);
if (verboselog)
log_client(addr, proc, prog);
return (TRUE);
}
/* check_callit - additional checks for forwarded requests */
int
check_callit(addr, proc, prog, aproc)
struct sockaddr_in *addr;
u_long proc;
u_long prog;
u_long aproc;
{
#ifdef HOSTS_ACCESS
if (!(from_local(addr) || good_client(addr))) {
log_bad_host(addr, proc, prog);
return (FALSE);
}
#endif
if (prog == PMAPPROG || prog == NFSPROG || prog == YPXPROG ||
(prog == MOUNTPROG && aproc == MOUNTPROC_MNT) ||
(prog == YPPROG && aproc != YPPROC_DOMAIN_NONACK)) {
log_no_forward(addr, proc, prog);
return (FALSE);
}
if (verboselog)
log_client(addr, proc, prog);
return (TRUE);
}
/* toggle_verboselog - toggle verbose logging flag */
static void toggle_verboselog(sig)
int sig;
{
(void) signal(sig, toggle_verboselog);
verboselog = !verboselog;
}
/* logit - report events of interest via the syslog daemon */
static void logit(severity, addr, procnum, prognum, text)
int severity;
struct sockaddr_in *addr;
u_long procnum;
u_long prognum;
char *text;
{
char *procname;
char procbuf[4 * sizeof(u_long)];
char *progname;
char progbuf[4 * sizeof(u_long)];
struct rpcent *rpc;
struct proc_map {
u_long code;
char *proc;
};
struct proc_map *procp;
static struct proc_map procmap[] = {
{PMAPPROC_CALLIT, "callit"},
{PMAPPROC_DUMP, "dump"},
{PMAPPROC_GETPORT, "getport"},
{PMAPPROC_NULL, "null"},
{PMAPPROC_SET, "set"},
{PMAPPROC_UNSET, "unset"},
{0, 0},
};
/*
* Fork off a process or the portmap daemon might hang while
* getrpcbynumber() or syslog() does its thing.
*/
if (fork() == 0) {
/* Try to map program number to name. */
if (prognum == 0) {
progname = "";
} else if ((rpc = getrpcbynumber((int) prognum))) {
progname = rpc->r_name;
} else {
sprintf(progname = progbuf, "%lu", prognum);
}
/* Try to map procedure number to name. */
for (procp = procmap; procp->proc && procp->code != procnum; procp++)
/* void */ ;
if ((procname = procp->proc) == 0)
sprintf(procname = procbuf, "%lu", (u_long) procnum);
/* Write syslog record. */
syslog(severity, "connect from %s to %s(%s)%s",
inet_ntoa(addr->sin_addr), procname, progname, text);
exit(0);
}
}
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