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Reviewed by: Bill fenner

Browse Source 
Submitted by:	Archie Cobbs (Archie@whistle.com)

Changes to allow inted to control the number of servers to
start on each service. This is a defence against a denial of service attack
in which the system is made unusable by
an external party. It also allows the behaviour of
small memory systems to be more accuratly predicted, by
bounding the extent to which processes can multiply.
This commit is contained in:
julian 1996-11-10 21:12:44 +00:00
parent 5278ea869e
commit f447087e68
3 changed files with 227 additions and 76 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
usr.sbin/inetd/Makefile
View File

@ -4,6 +4,9 @@ PROG= inetd
MAN8= inetd.8
MLINKS= inetd.8 inetd.conf.5
COPTS+= -Wall
#COPTS+= -DSANITY_CHECK
DPADD+= ${LIBUTIL}
LDADD+= -lutil

13
usr.sbin/inetd/inetd.8
View File

@ -30,7 +30,7 @@
.\" SUCH DAMAGE.
.\"
.\" from: @(#)inetd.8 8.3 (Berkeley) 4/13/94
.\" $Id: inetd.8,v 1.8 1996/02/07 17:15:00 wollman Exp $
.\" $Id: inetd.8,v 1.9 1996/08/09 22:20:23 julian Exp $
.\"
.Dd February 7, 1996
.Dt INETD 8
@ -101,7 +101,7 @@ fields of the configuration file are as follows:
service name
socket type
protocol
wait/nowait
{wait|nowait}[/max-child]
user
server program
server program arguments
@ -261,6 +261,15 @@ requests until a timeout.
TCPMUX services must use
.Dq nowait .
.Pp
The maximum number of outstanding child processes (or ``threads'')
for a ``nowait'' service may be explicitly specified by appending a
``/'' followed by the number to the ``nowait'' keyword. Normally
(or if a value of zero is specified) there is no maximum. Otherwise,
once the maximum is reached, further connection attempts will be
queued up until an existing child process exits. This also works
in the case of ``wait'' mode, although a value other than one (the
default) might not make sense in some cases.
.Pp
The
.Em user
entry should contain the user name of the user as whom the server

287
usr.sbin/inetd/inetd.c
View File

@ -40,7 +40,7 @@ static char copyright[] __attribute__ ((unused)) =
#ifndef lint
/* from: @(#)inetd.c 8.4 (Berkeley) 4/13/94"; */
static char inetd_c_rcsid[] __attribute__ ((unused)) =
"$Id: inetd.c,v 1.15 1996/11/01 01:42:08 alex Exp $";
"$Id: inetd.c,v 1.16 1996/11/10 21:07:27 julian Exp $";
#endif /* not lint */
/*
@ -132,10 +132,10 @@ static char inetd_c_rcsid[] __attribute__ ((unused)) =
#define TOOMANY 256 /* don't start more than TOOMANY */
#define CNT_INTVL 60 /* servers in CNT_INTVL sec. */
#define RETRYTIME (60*10) /* retry after bind or server fail */
#define MAX_MAXCHLD 32767 /* max allowable max children */
#define SIGBLOCK (sigmask(SIGCHLD)|sigmask(SIGHUP)|sigmask(SIGALRM))
int debug = 0;
int log = 0;
int nsock, maxsock;
@ -151,17 +151,20 @@ struct servtab {
char *se_service; /* name of service */
int se_socktype; /* type of socket to use */
char *se_proto; /* protocol used */
short se_wait; /* single threaded server */
short se_checked; /* looked at during merge */
short se_maxchild; /* max number of children */
short se_numchild; /* current number of children */
pid_t *se_pids; /* array of child pids */
char *se_user; /* user name to run as */
struct biltin *se_bi; /* if built-in, description */
char *se_server; /* server program */
#define MAXARGV 20
char *se_argv[MAXARGV+1]; /* program arguments */
int se_fd; /* open descriptor */
int se_type; /* type */
struct sockaddr_in se_ctrladdr;/* bound address */
int se_rpc; /* ==1 if RPC service */
u_char se_type; /* type: normal, mux, or mux+ */
u_char se_checked; /* looked at during merge */
u_char se_accept; /* i.e., wait/nowait mode */
u_char se_rpc; /* ==1 if RPC service */
int se_rpc_prog; /* RPC program number */
u_int se_rpc_lowvers; /* RPC low version */
u_int se_rpc_highvers; /* RPC high version */
@ -197,7 +200,10 @@ void machtime_stream __P((int, struct servtab *));
char *newstr __P((char *));
char *nextline __P((FILE *));
void print_service __P((char *, struct servtab *));
void addchild __P((struct servtab *, int));
void reapchild __P((int));
void enable __P((struct servtab *));
void disable __P((struct servtab *));
void retry __P((int));
int setconfig __P((void));
void setup __P((struct servtab *));
@ -211,7 +217,7 @@ struct biltin {
char *bi_service; /* internally provided service name */
int bi_socktype; /* type of socket supported */
short bi_fork; /* 1 if should fork before call */
short bi_wait; /* 1 if should wait for child */
short bi_maxchild; /* max number of children (default) */
void (*bi_fn)(); /* function which performs it */
} biltins[] = {
/* Echo received data */
@ -385,7 +391,7 @@ main(argc, argv, envp)
if (debug)
fprintf(stderr, "someone wants %s\n",
sep->se_service);
if (!sep->se_wait && sep->se_socktype == SOCK_STREAM) {
if (sep->se_accept && sep->se_socktype == SOCK_STREAM) {
ctrl = accept(sep->se_fd, (struct sockaddr *)0,
(int *)0);
if (debug)
@ -458,20 +464,15 @@ main(argc, argv, envp)
}
if (pid < 0) {
syslog(LOG_ERR, "fork: %m");
if (!sep->se_wait &&
if (sep->se_accept &&
sep->se_socktype == SOCK_STREAM)
close(ctrl);
sigsetmask(0L);
sleep(1);
continue;
}
if (pid && sep->se_wait) {
sep->se_wait = pid;
if (sep->se_fd >= 0) {
FD_CLR(sep->se_fd, &allsock);
nsock--;
}
}
if (pid)
addchild(sep, pid);
sigsetmask(0L);
if (pid == 0) {
if (dofork) {
@ -538,17 +539,43 @@ main(argc, argv, envp)
_exit(EX_OSERR);
}
}
if (!sep->se_wait && sep->se_socktype == SOCK_STREAM)
if (sep->se_accept && sep->se_socktype == SOCK_STREAM)
close(ctrl);
}
}
}
/*
* Record a new child pid for this service. If we've reached the
* limit on children, then stop accepting incoming requests.
*/
void
addchild(struct servtab *sep, pid_t pid)
{
#ifdef SANITY_CHECK
if (sep->se_numchild >= sep->se_maxchild) {
syslog(LOG_ERR, "%s: %d >= %d",
__FUNCTION__, sep->se_numchild, sep->se_maxchild);
exit(EX_SOFTWARE);
}
#endif
if (sep->se_maxchild == 0)
return;
sep->se_pids[sep->se_numchild++] = pid;
if (sep->se_numchild == sep->se_maxchild)
disable(sep);
}
/*
* Some child process has exited. See if it's on somebody's list.
*/
void
reapchild(signo)
int signo;
{
int status;
int k, status;
pid_t pid;
struct servtab *sep;
@ -559,19 +586,21 @@ reapchild(signo)
if (debug)
fprintf(stderr, "%d reaped, status %#x\n",
pid, status);
for (sep = servtab; sep; sep = sep->se_next)
if (sep->se_wait == pid) {
if (status)
syslog(LOG_WARNING,
"%s: exit status 0x%x",
sep->se_server, status);
if (debug)
fprintf(stderr, "restored %s, fd %d\n",
sep->se_service, sep->se_fd);
FD_SET(sep->se_fd, &allsock);
nsock++;
sep->se_wait = 1;
}
for (sep = servtab; sep; sep = sep->se_next) {
for (k = 0; k < sep->se_numchild; k++)
if (sep->se_pids[k] == pid)
break;
if (k == sep->se_numchild)
continue;
if (sep->se_numchild == sep->se_maxchild)
enable(sep);
sep->se_pids[k] = sep->se_pids[--sep->se_numchild];
if (status)
syslog(LOG_WARNING,
"%s[%d]: exit status 0x%x",
sep->se_server, pid, status);
break;
}
}
}
@ -579,7 +608,7 @@ void
config(signo)
int signo;
{
struct servtab *sep, *cp, **sepp;
struct servtab *sep, *new, **sepp;
struct passwd *pwd;
long omask;
@ -589,43 +618,57 @@ config(signo)
}
for (sep = servtab; sep; sep = sep->se_next)
sep->se_checked = 0;
while (cp = getconfigent()) {
if ((pwd = getpwnam(cp->se_user)) == NULL) {
while ((new = getconfigent())) {
if ((pwd = getpwnam(new->se_user)) == NULL) {
syslog(LOG_ERR,
"%s/%s: No such user '%s', service ignored",
cp->se_service, cp->se_proto, cp->se_user);
new->se_service, new->se_proto, new->se_user);
continue;
}
for (sep = servtab; sep; sep = sep->se_next)
if (strcmp(sep->se_service, cp->se_service) == 0 &&
strcmp(sep->se_proto, cp->se_proto) == 0)
if (strcmp(sep->se_service, new->se_service) == 0 &&
strcmp(sep->se_proto, new->se_proto) == 0)
break;
if (sep != 0) {
int i;
#define SWAP(a, b) { typeof(a) c = a; a = b; b = c; }
omask = sigblock(SIGBLOCK);
/*
* sep->se_wait may be holding the pid of a daemon
* that we're waiting for. If so, don't overwrite
* it unless the config file explicitly says don't
* wait.
*/
if (cp->se_bi == 0 &&
(sep->se_wait == 1 || cp->se_wait == 0))
sep->se_wait = cp->se_wait;
#define SWAP(a, b) { char *c = a; a = b; b = c; }
if (cp->se_user)
SWAP(sep->se_user, cp->se_user);
if (cp->se_server)
SWAP(sep->se_server, cp->se_server);
/* copy over outstanding child pids */
if (sep->se_maxchild && new->se_maxchild) {
new->se_numchild = sep->se_numchild;
if (new->se_numchild > new->se_maxchild)
new->se_numchild = new->se_maxchild;
memcpy(new->se_pids, sep->se_pids,
new->se_numchild * sizeof(*new->se_pids));
}
SWAP(sep->se_pids, new->se_pids);
sep->se_maxchild = new->se_maxchild;
sep->se_numchild = new->se_numchild;
/* might need to turn on or off service now */
if (sep->se_fd >= 0) {
if (sep->se_maxchild
&& sep->se_numchild == sep->se_maxchild) {
if (FD_ISSET(sep->se_fd, &allsock))
disable(sep);
} else {
if (!FD_ISSET(sep->se_fd, &allsock))
enable(sep);
}
}
sep->se_accept = new->se_accept;
if (new->se_user)
SWAP(sep->se_user, new->se_user);
if (new->se_server)
SWAP(sep->se_server, new->se_server);
for (i = 0; i < MAXARGV; i++)
SWAP(sep->se_argv[i], cp->se_argv[i]);
SWAP(sep->se_argv[i], new->se_argv[i]);
sigsetmask(omask);
freeconfig(cp);
freeconfig(new);
if (debug)
print_service("REDO", sep);
} else {
sep = enter(cp);
sep = enter(new);
if (debug)
print_service("ADD ", sep);
}
@ -799,10 +842,7 @@ setsockopt(fd, SOL_SOCKET, opt, (char *)&on, sizeof (on))
}
if (sep->se_socktype == SOCK_STREAM)
listen(sep->se_fd, 64);
FD_SET(sep->se_fd, &allsock);
nsock++;
if (sep->se_fd > maxsock)
maxsock = sep->se_fd;
enable(sep);
if (debug) {
fprintf(stderr, "registered %s on %d\n",
sep->se_server, sep->se_fd);
@ -817,18 +857,13 @@ close_sep(sep)
struct servtab *sep;
{
if (sep->se_fd >= 0) {
nsock--;
FD_CLR(sep->se_fd, &allsock);
if (FD_ISSET(sep->se_fd, &allsock))
disable(sep);
(void) close(sep->se_fd);
sep->se_fd = -1;
}
sep->se_count = 0;
/*
* Don't keep the pid of this running deamon: when reapchild()
* reaps this pid, it would erroneously increment nsock.
*/
if (sep->se_wait > 1)
sep->se_wait = 1;
sep->se_numchild = 0; /* forget about any existing children */
}
struct servtab *
@ -852,6 +887,68 @@ enter(cp)
return (sep);
}
void
enable(struct servtab *sep)
{
if (debug)
fprintf(stderr,
"enabling %s, fd %d", sep->se_service, sep->se_fd);
#ifdef SANITY_CHECK
if (sep->se_fd < 0) {
syslog(LOG_ERR,
"%s: %s: bad fd", __FUNCTION__, sep->se_service);
exit(EX_SOFTWARE);
}
if (ISMUX(sep)) {
syslog(LOG_ERR,
"%s: %s: is mux", __FUNCTION__, sep->se_service);
exit(EX_SOFTWARE);
}
if (FD_ISSET(sep->se_fd, &allsock)) {
syslog(LOG_ERR,
"%s: %s: not off", __FUNCTION__, sep->se_service);
exit(EX_SOFTWARE);
}
#endif
FD_SET(sep->se_fd, &allsock);
nsock++;
if (sep->se_fd > maxsock)
maxsock = sep->se_fd;
}
void
disable(struct servtab *sep)
{
if (debug)
fprintf(stderr,
"disabling %s, fd %d", sep->se_service, sep->se_fd);
#ifdef SANITY_CHECK
if (sep->se_fd < 0) {
syslog(LOG_ERR,
"%s: %s: bad fd", __FUNCTION__, sep->se_service);
exit(EX_SOFTWARE);
}
if (ISMUX(sep)) {
syslog(LOG_ERR,
"%s: %s: is mux", __FUNCTION__, sep->se_service);
exit(EX_SOFTWARE);
}
if (!FD_ISSET(sep->se_fd, &allsock)) {
syslog(LOG_ERR,
"%s: %s: not on", __FUNCTION__, sep->se_service);
exit(EX_SOFTWARE);
}
if (nsock == 0) {
syslog(LOG_ERR, "%s: nsock=0", __FUNCTION__);
exit(EX_SOFTWARE);
}
#endif
FD_CLR(sep->se_fd, &allsock);
nsock--;
if (sep->se_fd == maxsock)
maxsock--;
}
FILE *fconfig = NULL;
struct servtab serv;
char line[LINE_MAX];
@ -882,7 +979,7 @@ getconfigent()
{
struct servtab *sep = &serv;
int argc;
char *cp, *arg;
char *cp, *arg, *s;
char *versp;
static char TCPMUX_TOKEN[] = "tcpmux/";
#define MUX_LEN (sizeof(TCPMUX_TOKEN)-1)
@ -962,14 +1059,36 @@ getconfigent()
}
}
arg = sskip(&cp);
sep->se_wait = strcmp(arg, "wait") == 0;
if (!strncmp(arg, "wait", 4))
sep->se_accept = 0;
else if (!strncmp(arg, "nowait", 6))
sep->se_accept = 1;
else {
syslog(LOG_ERR,
"%s: bad wait/nowait for service %s",
CONFIG, sep->se_service);
goto more;
}
sep->se_maxchild = -1;
if ((s = strchr(arg, '/')) != NULL) {
char *eptr;
u_long val;
val = strtoul(s + 1, &eptr, 10);
if (eptr == s + 1 || *eptr || val > MAX_MAXCHLD) {
syslog(LOG_ERR,
"%s: bad max-child for service %s",
CONFIG, sep->se_service);
goto more;
}
sep->se_maxchild = val;
}
if (ISMUX(sep)) {
/*
* Silently enforce "nowait" for TCPMUX services since
* they don't have an assigned port to listen on.
* Silently enforce "nowait" mode for TCPMUX services
* since they don't have an assigned port to listen on.
*/
sep->se_wait = 0;
sep->se_accept = 1;
if (strcmp(sep->se_proto, "tcp")) {
syslog(LOG_ERR,
"%s: bad protocol for tcpmux service %s",
@ -997,14 +1116,32 @@ getconfigent()
sep->se_service);
goto more;
}
sep->se_accept = 1; /* force accept mode for built-ins */
sep->se_bi = bi;
sep->se_wait = bi->bi_wait;
} else
sep->se_bi = NULL;
if (sep->se_maxchild < 0) /* apply default max-children */
if (sep->se_bi)
sep->se_maxchild = sep->se_bi->bi_maxchild;
else
sep->se_maxchild = sep->se_accept ? 0 : 1;
if (sep->se_maxchild) {
sep->se_pids = malloc(sep->se_maxchild * sizeof(*sep->se_pids));
if (sep->se_pids == NULL) {
syslog(LOG_ERR, "Out of memory.");
exit(EX_OSERR);
}
}
argc = 0;
for (arg = skip(&cp); cp; arg = skip(&cp))
if (argc < MAXARGV)
if (argc < MAXARGV) {
sep->se_argv[argc++] = newstr(arg);
} else {
syslog(LOG_ERR,
"%s: too many arguments for service %s",
CONFIG, sep->se_service);
goto more;
}
while (argc <= MAXARGV)
sep->se_argv[argc++] = NULL;
return (sep);
@ -1024,6 +1161,8 @@ freeconfig(cp)
free(cp->se_user);
if (cp->se_server)
free(cp->se_server);
if (cp->se_pids)
free(cp->se_pids);
for (i = 0; i < MAXARGV; i++)
if (cp->se_argv[i])
free(cp->se_argv[i]);