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