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#include "system.h"
#include <sched.h>
#include <stdlib.h>
#include <fcntl.h>
#include <rpm/rpmstring.h>
#include <rpm/rpmlog.h>
#include "lib/rpmchroot.h"
#include "lib/rpmug.h"
#include "debug.h"
int _rpm_nouserns = 0;
struct rootState_s {
char *rootDir;
int chrootDone;
int cwd;
};
/* Process global chroot state */
static struct rootState_s rootState = {
.rootDir = NULL,
.chrootDone = 0,
.cwd = -1,
};
#if defined(HAVE_UNSHARE) && defined(CLONE_NEWUSER)
/*
* If setgroups file exists (Linux >= 3.19), we need to write "deny" to it,
* otherwise gid_map will fail.
*/
static int deny_setgroups(void)
{
int fd = open("/proc/self/setgroups", O_WRONLY, 0);
int xx = -1;
if (fd >= 0) {
xx = write(fd, "deny\n", strlen("deny\n"));
close (fd);
}
return (xx == -1);
}
static int setup_map(const char *path, unsigned int id, unsigned int oid)
{
int xx = -1;
int fd = open(path, O_WRONLY);
if (fd >= 0) {
char buf[256];
int ret = snprintf(buf, sizeof(buf), "%u %u 1\n", id, oid);
xx = write(fd, buf, ret);
close (fd);
}
return (xx == -1);
}
/*
* Try to become root by creating a user namespace. We don't really care
* if this fails here because in that case chroot() will just fail as it
* normally would.
*/
static void try_become_root(void)
{
static int unshared = 0;
uid_t uid = getuid();
gid_t gid = getgid();
if (!unshared && unshare(CLONE_NEWUSER | CLONE_NEWNS) == 0) {
deny_setgroups();
setup_map("/proc/self/uid_map", 0, uid);
setup_map("/proc/self/gid_map", 0, gid);
unshared = 1;
}
rpmlog(RPMLOG_DEBUG, "user ns: %d original user %d:%d current %d:%d\n",
unshared, uid, gid, getuid(), getgid());
}
#else
static void try_become_root(void)
{
}
#endif
int rpmChrootSet(const char *rootDir)
{
int rc = 0;
/* Setting same rootDir again is a no-op and not an error */
if (rootDir && rootState.rootDir && rstreq(rootDir, rootState.rootDir))
return 0;
/* Resetting only permitted in neutral state */
if (rootState.chrootDone != 0)
return -1;
rootState.rootDir = _free(rootState.rootDir);
if (rootState.cwd >= 0) {
close(rootState.cwd);
rootState.cwd = -1;
}
if (rootDir != NULL) {
rootState.rootDir = rstrdup(rootDir);
rootState.cwd = open(".", O_RDONLY);
if (rootState.cwd < 0) {
rpmlog(RPMLOG_ERR, _("Unable to open current directory: %m\n"));
rc = -1;
}
/* Force preloading of dlopen()'ed libraries before chroot */
if (rpmugInit())
rc = -1;
}
return rc;
}
int rpmChrootIn(void)
{
int rc = 0;
if (rootState.rootDir == NULL || rstreq(rootState.rootDir, "/"))
return 0;
if (rootState.cwd < 0) {
rpmlog(RPMLOG_ERR, _("%s: chroot directory not set\n"), __func__);
return -1;
}
/* "refcounted" entry to chroot */
if (rootState.chrootDone > 0) {
rootState.chrootDone++;
} else if (rootState.chrootDone == 0) {
if (!_rpm_nouserns && getuid())
try_become_root();
rpmlog(RPMLOG_DEBUG, "entering chroot %s\n", rootState.rootDir);
if (chdir("/") == 0 && chroot(rootState.rootDir) == 0) {
rootState.chrootDone = 1;
} else {
rpmlog(RPMLOG_ERR, _("Unable to change root directory: %m\n"));
rc = -1;
}
}
return rc;
}
int rpmChrootOut(void)
{
int rc = 0;
if (rootState.rootDir == NULL || rstreq(rootState.rootDir, "/"))
return 0;
if (rootState.cwd < 0) {
rpmlog(RPMLOG_ERR, _("%s: chroot directory not set\n"), __func__);
return -1;
}
/* "refcounted" return from chroot */
if (rootState.chrootDone > 1) {
rootState.chrootDone--;
} else if (rootState.chrootDone == 1) {
rpmlog(RPMLOG_DEBUG, "exiting chroot %s\n", rootState.rootDir);
if (chroot(".") == 0 && fchdir(rootState.cwd) == 0) {
rootState.chrootDone = 0;
} else {
rpmlog(RPMLOG_ERR, _("Unable to restore root directory: %m\n"));
rc = -1;
}
}
return rc;
}
int rpmChrootDone(void)
{
return (rootState.chrootDone > 0);
}
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