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.
Approved by: so
Security: EN-21:19.libcasper
PR: 255339
Reported by: Borja Marcos <borjam (at) sarenet.es>
Tested by: jkim@
(cherry picked from commit aa310ebfba
)
(cherry picked from commit 4e2ae05c3ae8c470829b4c3a78aa8c34a7f0b617)
This commit is contained in:
parent
bdb244c37d
commit
3ed4f7af83
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@ -32,8 +32,10 @@
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* $FreeBSD$
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*/
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#include <err.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <paths.h>
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#include <stdlib.h>
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#include "libcasper_impl.h"
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@ -44,3 +46,28 @@ fd_is_valid(int fd)
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return (fcntl(fd, F_GETFL) != -1 || errno != EBADF);
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}
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void
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fd_fix_environment(int *fdp)
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{
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int nullfd, nfd;
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if (*fdp > STDERR_FILENO)
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return;
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nullfd = open(_PATH_DEVNULL, O_RDWR);
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if (nullfd == -1)
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errx(1, "Unable to open %s", _PATH_DEVNULL);
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while (*fdp <= STDERR_FILENO) {
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nfd = dup(*fdp);
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if (nfd == -1)
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errx(1, "Unable to secure fd");
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if (dup2(nullfd, *fdp) == -1)
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errx(1, "Unable to secure fd");
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*fdp = nfd;
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}
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close(nullfd);
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}
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@ -44,6 +44,7 @@ struct service;
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struct service_connection;
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bool fd_is_valid(int fd);
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void fd_fix_environment(int *fdp);
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/* Private service functions. */
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struct service *service_alloc(const char *name,
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@ -386,24 +386,27 @@ stdnull(void)
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}
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static void
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service_clean(int sock, int procfd, uint64_t flags)
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service_clean(int *sockp, int *procfdp, uint64_t flags)
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{
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int fd, maxfd, minfd;
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assert(sock > STDERR_FILENO);
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assert(procfd > STDERR_FILENO);
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assert(sock != procfd);
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fd_fix_environment(sockp);
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fd_fix_environment(procfdp);
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assert(*sockp > STDERR_FILENO);
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assert(*procfdp > STDERR_FILENO);
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assert(*sockp != *procfdp);
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if ((flags & CASPER_SERVICE_STDIO) == 0)
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stdnull();
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if ((flags & CASPER_SERVICE_FD) == 0) {
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if (procfd > sock) {
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maxfd = procfd;
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minfd = sock;
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if (*procfdp > *sockp) {
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maxfd = *procfdp;
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minfd = *sockp;
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} else {
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maxfd = sock;
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minfd = procfd;
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maxfd = *sockp;
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minfd = *procfdp;
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}
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for (fd = STDERR_FILENO + 1; fd < maxfd; fd++) {
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@ -424,7 +427,7 @@ service_start(struct service *service, int sock, int procfd)
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assert(service != NULL);
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assert(service->s_magic == SERVICE_MAGIC);
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setproctitle("%s", service->s_name);
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service_clean(sock, procfd, service->s_flags);
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service_clean(&sock, &procfd, service->s_flags);
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if (service_connection_add(service, sock, NULL) == NULL)
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_exit(1);
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@ -52,6 +52,7 @@ __FBSDID("$FreeBSD$");
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#include <strings.h>
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#include <unistd.h>
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#include "libcasper_impl.h"
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#include "zygote.h"
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/* Zygote info. */
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@ -104,7 +105,7 @@ zygote_clone_service_execute(int *chanfdp, int *procfdp)
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* between sandbox and its owner.
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*/
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static void
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zygote_main(int sock)
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zygote_main(int *sockp)
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{
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int error, procfd;
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int chanfd[2];
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@ -113,12 +114,14 @@ zygote_main(int sock)
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zygote_func_t *func;
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pid_t pid;
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assert(sock > STDERR_FILENO);
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fd_fix_environment(sockp);
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assert(*sockp > STDERR_FILENO);
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setproctitle("zygote");
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for (;;) {
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nvlin = nvlist_recv(sock, 0);
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nvlin = nvlist_recv(*sockp, 0);
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if (nvlin == NULL) {
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if (errno == ENOTCONN) {
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/* Casper exited. */
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@ -157,7 +160,7 @@ zygote_main(int sock)
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break;
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case 0:
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/* Child. */
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close(sock);
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close(*sockp);
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close(chanfd[0]);
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func(chanfd[1]);
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/* NOTREACHED */
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@ -179,7 +182,7 @@ send:
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nvlist_move_descriptor(nvlout, "chanfd", chanfd[0]);
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nvlist_move_descriptor(nvlout, "procfd", procfd);
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}
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(void)nvlist_send(sock, nvlout);
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(void)nvlist_send(*sockp, nvlout);
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nvlist_destroy(nvlout);
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}
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/* NOTREACHED */
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@ -206,7 +209,7 @@ zygote_init(void)
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case 0:
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/* Child. */
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close(sp[0]);
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zygote_main(sp[1]);
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zygote_main(&sp[1]);
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/* NOTREACHED */
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abort();
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default:
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