chroot and change user support (Nolan)
Resent with fixed formatting.
This patch adds two new command line options:
-chroot <dir>
-runas <user>
This is useful for running qemu as an unprivileged user in a chroot
jail. To avoid having to populate the jail, chrooting happens right
before the start of guest execution.
Signed-off-by: Nolan Leake <nolan@sigbus.net>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6652 c046a42c-6fe2-441c-8c8c-71466251a162
diff --git a/qemu-doc.texi b/qemu-doc.texi
index 39a3a76..616de48 100644
--- a/qemu-doc.texi
+++ b/qemu-doc.texi
@@ -1161,6 +1161,14 @@
@item -echr 20
@end table
+@item -chroot dir
+Immediately before starting guest execution, chroot to the specified
+directory. Especially useful in combination with -runas.
+
+@item -runas user
+Immediately before starting guest execution, drop root privileges, switching
+to the specified user.
+
@end table
@c man end
diff --git a/vl.c b/vl.c
index 224c811..8e59cd8 100644
--- a/vl.c
+++ b/vl.c
@@ -52,6 +52,7 @@
#include <zlib.h>
#ifndef _WIN32
+#include <pwd.h>
#include <sys/times.h>
#include <sys/wait.h>
#include <termios.h>
@@ -4075,6 +4076,10 @@
#endif
"-tb-size n set TB size\n"
"-incoming p prepare for incoming migration, listen on port p\n"
+#ifndef _WIN32
+ "-chroot dir Chroot to dir just before starting the VM.\n"
+ "-runas user Change to user id user just before starting the VM.\n"
+#endif
"\n"
"During emulation, the following keys are useful:\n"
"ctrl-alt-f toggle full screen\n"
@@ -4192,6 +4197,8 @@
QEMU_OPTION_old_param,
QEMU_OPTION_tb_size,
QEMU_OPTION_incoming,
+ QEMU_OPTION_chroot,
+ QEMU_OPTION_runas,
};
typedef struct QEMUOption {
@@ -4322,6 +4329,8 @@
#endif
{ "tb-size", HAS_ARG, QEMU_OPTION_tb_size },
{ "incoming", HAS_ARG, QEMU_OPTION_incoming },
+ { "chroot", HAS_ARG, QEMU_OPTION_chroot },
+ { "runas", HAS_ARG, QEMU_OPTION_runas },
{ NULL },
};
@@ -4632,6 +4641,10 @@
const char *pid_file = NULL;
int autostart;
const char *incoming = NULL;
+ int fd;
+ struct passwd *pwd;
+ const char *chroot_dir = NULL;
+ const char *run_as = NULL;
qemu_cache_utils_init(envp);
@@ -5287,6 +5300,12 @@
case QEMU_OPTION_incoming:
incoming = optarg;
break;
+ case QEMU_OPTION_chroot:
+ chroot_dir = optarg;
+ break;
+ case QEMU_OPTION_runas:
+ run_as = optarg;
+ break;
}
}
}
@@ -5739,7 +5758,6 @@
if (daemonize) {
uint8_t status = 0;
ssize_t len;
- int fd;
again1:
len = write(fds[1], &status, 1);
@@ -5753,12 +5771,47 @@
TFR(fd = open("/dev/null", O_RDWR));
if (fd == -1)
exit(1);
+ }
- dup2(fd, 0);
- dup2(fd, 1);
- dup2(fd, 2);
+#ifndef _WIN32
+ if (run_as) {
+ pwd = getpwnam(run_as);
+ if (!pwd) {
+ fprintf(stderr, "User \"%s\" doesn't exist\n", run_as);
+ exit(1);
+ }
+ }
- close(fd);
+ if (chroot_dir) {
+ if (chroot(chroot_dir) < 0) {
+ fprintf(stderr, "chroot failed\n");
+ exit(1);
+ }
+ chdir("/");
+ }
+
+ if (run_as) {
+ if (setgid(pwd->pw_gid) < 0) {
+ fprintf(stderr, "Failed to setgid(%d)\n", pwd->pw_gid);
+ exit(1);
+ }
+ if (setuid(pwd->pw_uid) < 0) {
+ fprintf(stderr, "Failed to setuid(%d)\n", pwd->pw_uid);
+ exit(1);
+ }
+ if (setuid(0) != -1) {
+ fprintf(stderr, "Dropping privileges failed\n");
+ exit(1);
+ }
+ }
+#endif
+
+ if (daemonize) {
+ dup2(fd, 0);
+ dup2(fd, 1);
+ dup2(fd, 2);
+
+ close(fd);
}
main_loop();
