mirror of
https://github.com/genuinetools/reg.git
synced 2024-08-22 06:30:23 -04:00
473 lines
11 KiB
C
473 lines
11 KiB
C
#define _GNU_SOURCE
|
|
#include <endian.h>
|
|
#include <errno.h>
|
|
#include <fcntl.h>
|
|
#include <linux/limits.h>
|
|
#include <sys/socket.h>
|
|
#include <linux/netlink.h>
|
|
#include <sched.h>
|
|
#include <setjmp.h>
|
|
#include <signal.h>
|
|
#include <stdint.h>
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <string.h>
|
|
#include <sys/ioctl.h>
|
|
#include <sys/types.h>
|
|
#include <sys/prctl.h>
|
|
#include <unistd.h>
|
|
#include <grp.h>
|
|
|
|
#include <bits/sockaddr.h>
|
|
#include <linux/types.h>
|
|
|
|
// All arguments should be above the stack because it grows down
|
|
struct clone_arg {
|
|
/*
|
|
* Reserve some space for clone() to locate arguments
|
|
* and retcode in this place
|
|
*/
|
|
char stack[4096] __attribute__((aligned(16)));
|
|
char stack_ptr[0];
|
|
jmp_buf *env;
|
|
};
|
|
|
|
struct nsenter_config {
|
|
uint32_t cloneflags;
|
|
char *uidmap;
|
|
int uidmap_len;
|
|
char *gidmap;
|
|
int gidmap_len;
|
|
uint8_t is_setgroup;
|
|
int consolefd;
|
|
};
|
|
|
|
// list of known message types we want to send to bootstrap program
|
|
// These are defined in libcontainer/message_linux.go
|
|
#define INIT_MSG 62000
|
|
#define CLONE_FLAGS_ATTR 27281
|
|
#define CONSOLE_PATH_ATTR 27282
|
|
#define NS_PATHS_ATTR 27283
|
|
#define UIDMAP_ATTR 27284
|
|
#define GIDMAP_ATTR 27285
|
|
#define SETGROUP_ATTR 27286
|
|
|
|
// Use raw setns syscall for versions of glibc that don't include it
|
|
// (namely glibc-2.12)
|
|
#if __GLIBC__ == 2 && __GLIBC_MINOR__ < 14
|
|
#define _GNU_SOURCE
|
|
#include "syscall.h"
|
|
#if defined(__NR_setns) && !defined(SYS_setns)
|
|
#define SYS_setns __NR_setns
|
|
#endif
|
|
|
|
#ifdef SYS_setns
|
|
int setns(int fd, int nstype)
|
|
{
|
|
return syscall(SYS_setns, fd, nstype);
|
|
}
|
|
#endif
|
|
#endif
|
|
|
|
#define pr_perror(fmt, ...) \
|
|
fprintf(stderr, "nsenter: " fmt ": %m\n", ##__VA_ARGS__)
|
|
|
|
static int child_func(void *_arg)
|
|
{
|
|
struct clone_arg *arg = (struct clone_arg *)_arg;
|
|
longjmp(*arg->env, 1);
|
|
}
|
|
|
|
static int clone_parent(jmp_buf *env, int flags) __attribute__((noinline));
|
|
static int clone_parent(jmp_buf *env, int flags)
|
|
{
|
|
struct clone_arg ca;
|
|
int child;
|
|
|
|
ca.env = env;
|
|
child = clone(child_func, ca.stack_ptr, CLONE_PARENT | SIGCHLD | flags,
|
|
&ca);
|
|
// On old kernels, CLONE_PARENT cannot work with CLONE_NEWPID,
|
|
// unshare before clone to workaround this.
|
|
if (child == -1 && errno == EINVAL) {
|
|
if (unshare(flags)) {
|
|
pr_perror("Unable to unshare namespaces");
|
|
return -1;
|
|
}
|
|
child = clone(child_func, ca.stack_ptr, SIGCHLD | CLONE_PARENT,
|
|
&ca);
|
|
}
|
|
return child;
|
|
}
|
|
|
|
// get init pipe from the parent. It's used to read bootstrap data, and to
|
|
// write pid to after nsexec finishes setting up the environment.
|
|
static int get_init_pipe()
|
|
{
|
|
char buf[PATH_MAX];
|
|
char *initpipe;
|
|
int pipenum = -1;
|
|
|
|
initpipe = getenv("_LIBCONTAINER_INITPIPE");
|
|
if (initpipe == NULL) {
|
|
return -1;
|
|
}
|
|
|
|
pipenum = atoi(initpipe);
|
|
snprintf(buf, sizeof(buf), "%d", pipenum);
|
|
if (strcmp(initpipe, buf)) {
|
|
pr_perror("Unable to parse _LIBCONTAINER_INITPIPE");
|
|
exit(1);
|
|
}
|
|
|
|
return pipenum;
|
|
}
|
|
|
|
// num_namespaces returns the number of additional namespaces to setns. The
|
|
// argument is a comma-separated string of namespace paths.
|
|
static int num_namespaces(char *nspaths)
|
|
{
|
|
int i;
|
|
int size = 0;
|
|
|
|
for (i = 0; nspaths[i]; i++) {
|
|
if (nspaths[i] == ',') {
|
|
size += 1;
|
|
}
|
|
}
|
|
|
|
return size + 1;
|
|
}
|
|
|
|
static uint32_t readint32(char *buf)
|
|
{
|
|
return *(uint32_t *)buf;
|
|
}
|
|
|
|
static uint8_t readint8(char *buf)
|
|
{
|
|
return *(uint8_t *)buf;
|
|
}
|
|
|
|
static void update_process_idmap(char *pathfmt, int pid, char *map, int map_len)
|
|
{
|
|
char buf[PATH_MAX];
|
|
int len;
|
|
int fd;
|
|
|
|
len = snprintf(buf, sizeof(buf), pathfmt, pid);
|
|
if (len < 0) {
|
|
pr_perror("failed to construct '%s' for %d", pathfmt, pid);
|
|
exit(1);
|
|
}
|
|
|
|
fd = open(buf, O_RDWR);
|
|
if (fd == -1) {
|
|
pr_perror("failed to open %s", buf);
|
|
exit(1);
|
|
}
|
|
|
|
len = write(fd, map, map_len);
|
|
if (len == -1) {
|
|
pr_perror("failed to write to %s", buf);
|
|
close(fd);
|
|
exit(1);
|
|
} else if (len != map_len) {
|
|
pr_perror("Failed to write data to %s (%d/%d)",
|
|
buf, len, map_len);
|
|
close(fd);
|
|
exit(1);
|
|
}
|
|
|
|
close(fd);
|
|
}
|
|
|
|
static void update_process_uidmap(int pid, char *map, int map_len)
|
|
{
|
|
if ((map == NULL) || (map_len <= 0)) {
|
|
return;
|
|
}
|
|
|
|
update_process_idmap("/proc/%d/uid_map", pid, map, map_len);
|
|
}
|
|
|
|
static void update_process_gidmap(int pid, uint8_t is_setgroup, char *map, int map_len)
|
|
{
|
|
if ((map == NULL) || (map_len <= 0)) {
|
|
return;
|
|
}
|
|
|
|
if (is_setgroup == 1) {
|
|
int fd;
|
|
int len;
|
|
char buf[PATH_MAX];
|
|
|
|
len = snprintf(buf, sizeof(buf), "/proc/%d/setgroups", pid);
|
|
if (len < 0) {
|
|
pr_perror("failed to get setgroups path for %d", pid);
|
|
exit(1);
|
|
}
|
|
|
|
fd = open(buf, O_RDWR);
|
|
if (fd == -1) {
|
|
pr_perror("failed to open %s", buf);
|
|
exit(1);
|
|
}
|
|
if (write(fd, "allow", 5) != 5) {
|
|
// If the kernel is too old to support
|
|
// /proc/PID/setgroups, write will return
|
|
// ENOENT; this is OK.
|
|
if (errno != ENOENT) {
|
|
pr_perror("failed to write allow to %s", buf);
|
|
close(fd);
|
|
exit(1);
|
|
}
|
|
}
|
|
close(fd);
|
|
}
|
|
|
|
update_process_idmap("/proc/%d/gid_map", pid, map, map_len);
|
|
}
|
|
|
|
|
|
static void start_child(int pipenum, jmp_buf *env, int syncpipe[2],
|
|
struct nsenter_config *config)
|
|
{
|
|
int len;
|
|
int childpid;
|
|
char buf[PATH_MAX];
|
|
uint8_t syncbyte = 1;
|
|
|
|
// We must fork to actually enter the PID namespace, use CLONE_PARENT
|
|
// so the child can have the right parent, and we don't need to forward
|
|
// the child's exit code or resend its death signal.
|
|
childpid = clone_parent(env, config->cloneflags);
|
|
if (childpid < 0) {
|
|
pr_perror("Unable to fork");
|
|
exit(1);
|
|
}
|
|
|
|
// update uid_map and gid_map for the child process if they
|
|
// were provided
|
|
update_process_uidmap(childpid, config->uidmap, config->uidmap_len);
|
|
update_process_gidmap(childpid, config->is_setgroup, config->gidmap, config->gidmap_len);
|
|
|
|
// Send the sync signal to the child
|
|
close(syncpipe[0]);
|
|
syncbyte = 1;
|
|
if (write(syncpipe[1], &syncbyte, 1) != 1) {
|
|
pr_perror("failed to write sync byte to child");
|
|
exit(1);
|
|
}
|
|
|
|
// Send the child pid back to our parent
|
|
len = snprintf(buf, sizeof(buf), "{ \"pid\" : %d }\n", childpid);
|
|
if ((len < 0) || (write(pipenum, buf, len) != len)) {
|
|
pr_perror("Unable to send a child pid");
|
|
kill(childpid, SIGKILL);
|
|
exit(1);
|
|
}
|
|
|
|
exit(0);
|
|
}
|
|
|
|
static struct nsenter_config process_nl_attributes(int pipenum, char *data, int data_size)
|
|
{
|
|
struct nsenter_config config = {0};
|
|
struct nlattr *nlattr;
|
|
int payload_len;
|
|
int start = 0;
|
|
|
|
config.consolefd = -1;
|
|
while (start < data_size) {
|
|
nlattr = (struct nlattr *)(data + start);
|
|
start += NLA_HDRLEN;
|
|
payload_len = nlattr->nla_len - NLA_HDRLEN;
|
|
|
|
if (nlattr->nla_type == CLONE_FLAGS_ATTR) {
|
|
config.cloneflags = readint32(data + start);
|
|
} else if (nlattr->nla_type == CONSOLE_PATH_ATTR) {
|
|
// get the console path before setns because it may
|
|
// change mnt namespace
|
|
config.consolefd = open(data + start, O_RDWR);
|
|
if (config.consolefd < 0) {
|
|
pr_perror("Failed to open console %s",
|
|
data + start);
|
|
exit(1);
|
|
}
|
|
} else if (nlattr->nla_type == NS_PATHS_ATTR) {
|
|
// if custom namespaces are required, open all
|
|
// descriptors and perform setns on them
|
|
int i, j;
|
|
int nslen = num_namespaces(data + start);
|
|
int fds[nslen];
|
|
char *nslist[nslen];
|
|
char *ns;
|
|
char *saveptr;
|
|
|
|
for (i = 0; i < nslen; i++) {
|
|
char *str = NULL;
|
|
|
|
if (i == 0) {
|
|
str = data + start;
|
|
}
|
|
ns = strtok_r(str, ",", &saveptr);
|
|
if (ns == NULL) {
|
|
break;
|
|
}
|
|
fds[i] = open(ns, O_RDONLY);
|
|
if (fds[i] == -1) {
|
|
for (j = 0; j < i; j++) {
|
|
close(fds[j]);
|
|
}
|
|
pr_perror("Failed to open %s", ns);
|
|
exit(1);
|
|
}
|
|
nslist[i] = ns;
|
|
}
|
|
|
|
for (i = 0; i < nslen; i++) {
|
|
if (setns(fds[i], 0) != 0) {
|
|
pr_perror("Failed to setns to %s", nslist[i]);
|
|
exit(1);
|
|
}
|
|
close(fds[i]);
|
|
}
|
|
} else if (nlattr->nla_type == UIDMAP_ATTR) {
|
|
config.uidmap = data + start;
|
|
config.uidmap_len = payload_len;
|
|
} else if (nlattr->nla_type == GIDMAP_ATTR) {
|
|
config.gidmap = data + start;
|
|
config.gidmap_len = payload_len;
|
|
} else if (nlattr->nla_type == SETGROUP_ATTR) {
|
|
config.is_setgroup = readint8(data + start);
|
|
} else {
|
|
pr_perror("Unknown netlink message type %d",
|
|
nlattr->nla_type);
|
|
exit(1);
|
|
}
|
|
|
|
start += NLA_ALIGN(payload_len);
|
|
}
|
|
|
|
return config;
|
|
}
|
|
|
|
void nsexec(void)
|
|
{
|
|
int pipenum;
|
|
|
|
// If we don't have init pipe, then just return to the go routine,
|
|
// we'll only have init pipe for start or exec
|
|
pipenum = get_init_pipe();
|
|
if (pipenum == -1) {
|
|
return;
|
|
}
|
|
|
|
// Retrieve the netlink header
|
|
struct nlmsghdr nl_msg_hdr;
|
|
int len;
|
|
|
|
if ((len = read(pipenum, &nl_msg_hdr, NLMSG_HDRLEN)) != NLMSG_HDRLEN) {
|
|
pr_perror("Invalid netlink header length %d", len);
|
|
exit(1);
|
|
}
|
|
|
|
if (nl_msg_hdr.nlmsg_type == NLMSG_ERROR) {
|
|
pr_perror("Failed to read netlink message");
|
|
exit(1);
|
|
}
|
|
|
|
if (nl_msg_hdr.nlmsg_type != INIT_MSG) {
|
|
pr_perror("Unexpected msg type %d", nl_msg_hdr.nlmsg_type);
|
|
exit(1);
|
|
}
|
|
|
|
// Retrieve data
|
|
int nl_total_size = NLMSG_PAYLOAD(&nl_msg_hdr, 0);
|
|
char data[nl_total_size];
|
|
|
|
if ((len = read(pipenum, data, nl_total_size)) != nl_total_size) {
|
|
pr_perror("Failed to read netlink payload, %d != %d", len,
|
|
nl_total_size);
|
|
exit(1);
|
|
}
|
|
|
|
jmp_buf env;
|
|
int syncpipe[2] = {-1, -1};
|
|
struct nsenter_config config = process_nl_attributes(pipenum,
|
|
data, nl_total_size);
|
|
|
|
// required clone_flags to be passed
|
|
if (config.cloneflags == -1) {
|
|
pr_perror("Missing clone_flags");
|
|
exit(1);
|
|
}
|
|
// prepare sync pipe between parent and child. We need this to let the
|
|
// child know that the parent has finished setting up
|
|
if (pipe(syncpipe) != 0) {
|
|
pr_perror("Failed to setup sync pipe between parent and child");
|
|
exit(1);
|
|
}
|
|
|
|
if (setjmp(env) == 1) {
|
|
// Child
|
|
uint8_t s = 0;
|
|
int consolefd = config.consolefd;
|
|
|
|
// close the writing side of pipe
|
|
close(syncpipe[1]);
|
|
|
|
// sync with parent
|
|
if ((read(syncpipe[0], &s, 1) != 1) || (s != 1)) {
|
|
pr_perror("Failed to read sync byte from parent");
|
|
exit(1);
|
|
}
|
|
|
|
if (setsid() == -1) {
|
|
pr_perror("setsid failed");
|
|
exit(1);
|
|
}
|
|
|
|
if (setuid(0) == -1) {
|
|
pr_perror("setuid failed");
|
|
exit(1);
|
|
}
|
|
|
|
if (setgid(0) == -1) {
|
|
pr_perror("setgid failed");
|
|
exit(1);
|
|
}
|
|
|
|
if (setgroups(0, NULL) == -1) {
|
|
pr_perror("setgroups failed");
|
|
exit(1);
|
|
}
|
|
|
|
if (consolefd != -1) {
|
|
if (ioctl(consolefd, TIOCSCTTY, 0) == -1) {
|
|
pr_perror("ioctl TIOCSCTTY failed");
|
|
exit(1);
|
|
}
|
|
if (dup3(consolefd, STDIN_FILENO, 0) != STDIN_FILENO) {
|
|
pr_perror("Failed to dup stdin");
|
|
exit(1);
|
|
}
|
|
if (dup3(consolefd, STDOUT_FILENO, 0) != STDOUT_FILENO) {
|
|
pr_perror("Failed to dup stdout");
|
|
exit(1);
|
|
}
|
|
if (dup3(consolefd, STDERR_FILENO, 0) != STDERR_FILENO) {
|
|
pr_perror("Failed to dup stderr");
|
|
exit(1);
|
|
}
|
|
}
|
|
|
|
// Finish executing, let the Go runtime take over.
|
|
return;
|
|
}
|
|
|
|
// Parent
|
|
start_child(pipenum, &env, syncpipe, &config);
|
|
}
|