libcasper: fix descriptors numbers

Casper services expect that the first 3 descriptors (stdin/stdout/stderr)
will point to /dev/null. Which Casper will ensure later. The Casper
services are forked from the original process. If the initial process
closes one of those descriptors, Casper may reuse one of them for it on
purpose. If this is the case, then renumarate the descriptors used by
Casper to higher numbers. This is done already after the fork, so it
doesn't break the parent process.

PR:		225343
Reported by:	Borja Marcos <borjam (at) sarenet.es>
Tested by:	jkim@
This commit is contained in:
Mariusz Zaborski 2021-06-09 23:46:51 +02:00
parent 4ab5c88da2
commit aa310ebfba
4 changed files with 50 additions and 16 deletions

View File

@ -32,8 +32,10 @@
* $FreeBSD$
*/
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <paths.h>
#include <stdlib.h>
#include "libcasper_impl.h"
@ -44,3 +46,28 @@ fd_is_valid(int fd)
return (fcntl(fd, F_GETFL) != -1 || errno != EBADF);
}
void
fd_fix_environment(int *fdp)
{
int nullfd, nfd;
if (*fdp > STDERR_FILENO)
return;
nullfd = open(_PATH_DEVNULL, O_RDWR);
if (nullfd == -1)
errx(1, "Unable to open %s", _PATH_DEVNULL);
while (*fdp <= STDERR_FILENO) {
nfd = dup(*fdp);
if (nfd == -1)
errx(1, "Unable to secure fd");
if (dup2(nullfd, *fdp) == -1)
errx(1, "Unable to secure fd");
*fdp = nfd;
}
close(nullfd);
}

View File

@ -44,6 +44,7 @@ struct service;
struct service_connection;
bool fd_is_valid(int fd);
void fd_fix_environment(int *fdp);
/* Private service functions. */
struct service *service_alloc(const char *name,

View File

@ -386,24 +386,27 @@ stdnull(void)
}
static void
service_clean(int sock, int procfd, uint64_t flags)
service_clean(int *sockp, int *procfdp, uint64_t flags)
{
int fd, maxfd, minfd;
assert(sock > STDERR_FILENO);
assert(procfd > STDERR_FILENO);
assert(sock != procfd);
fd_fix_environment(sockp);
fd_fix_environment(procfdp);
assert(*sockp > STDERR_FILENO);
assert(*procfdp > STDERR_FILENO);
assert(*sockp != *procfdp);
if ((flags & CASPER_SERVICE_STDIO) == 0)
stdnull();
if ((flags & CASPER_SERVICE_FD) == 0) {
if (procfd > sock) {
maxfd = procfd;
minfd = sock;
if (*procfdp > *sockp) {
maxfd = *procfdp;
minfd = *sockp;
} else {
maxfd = sock;
minfd = procfd;
maxfd = *sockp;
minfd = *procfdp;
}
for (fd = STDERR_FILENO + 1; fd < maxfd; fd++) {
@ -424,7 +427,7 @@ service_start(struct service *service, int sock, int procfd)
assert(service != NULL);
assert(service->s_magic == SERVICE_MAGIC);
setproctitle("%s", service->s_name);
service_clean(sock, procfd, service->s_flags);
service_clean(&sock, &procfd, service->s_flags);
if (service_connection_add(service, sock, NULL) == NULL)
_exit(1);

View File

@ -52,6 +52,7 @@ __FBSDID("$FreeBSD$");
#include <strings.h>
#include <unistd.h>
#include "libcasper_impl.h"
#include "zygote.h"
/* Zygote info. */
@ -104,7 +105,7 @@ zygote_clone_service_execute(int *chanfdp, int *procfdp)
* between sandbox and its owner.
*/
static void
zygote_main(int sock)
zygote_main(int *sockp)
{
int error, procfd;
int chanfd[2];
@ -113,12 +114,14 @@ zygote_main(int sock)
zygote_func_t *func;
pid_t pid;
assert(sock > STDERR_FILENO);
fd_fix_environment(sockp);
assert(*sockp > STDERR_FILENO);
setproctitle("zygote");
for (;;) {
nvlin = nvlist_recv(sock, 0);
nvlin = nvlist_recv(*sockp, 0);
if (nvlin == NULL) {
if (errno == ENOTCONN) {
/* Casper exited. */
@ -157,7 +160,7 @@ zygote_main(int sock)
break;
case 0:
/* Child. */
close(sock);
close(*sockp);
close(chanfd[0]);
func(chanfd[1]);
/* NOTREACHED */
@ -179,7 +182,7 @@ zygote_main(int sock)
nvlist_move_descriptor(nvlout, "chanfd", chanfd[0]);
nvlist_move_descriptor(nvlout, "procfd", procfd);
}
(void)nvlist_send(sock, nvlout);
(void)nvlist_send(*sockp, nvlout);
nvlist_destroy(nvlout);
}
/* NOTREACHED */
@ -206,7 +209,7 @@ zygote_init(void)
case 0:
/* Child. */
close(sp[0]);
zygote_main(sp[1]);
zygote_main(&sp[1]);
/* NOTREACHED */
abort();
default: