github/skopeo
1
0
Fork 0
mirror of https://github.com/containers/skopeo.git synced 2025-09-21 09:57:19 +00:00
Code Issues Projects Releases Wiki Activity

Vendor after merging containers/image#436

Browse Source 
Signed-off-by: Miloslav Trmač <mitr@redhat.com>
This commit is contained in:
Miloslav Trmač
2018-04-05 21:33:04 +02:00
parent c61482d2cf
commit 7aba888e99
101 changed files with 10538 additions and 312 deletions
Download Patch File Download Diff File Expand all files Collapse all files

44
vendor/github.com/opencontainers/runc/libcontainer/nsenter/README.md generated vendored Normal file
View File

@@ -0,0 +1,44 @@
## nsenter
The `nsenter` package registers a special init constructor that is called before
the Go runtime has a chance to boot. This provides us the ability to `setns` on
existing namespaces and avoid the issues that the Go runtime has with multiple
threads. This constructor will be called if this package is registered,
imported, in your go application.
The `nsenter` package will `import "C"` and it uses [cgo](https://golang.org/cmd/cgo/)
package. In cgo, if the import of "C" is immediately preceded by a comment, that comment,
called the preamble, is used as a header when compiling the C parts of the package.
So every time we import package `nsenter`, the C code function `nsexec()` would be
called. And package `nsenter` is now only imported in `main_unix.go`, so every time
before we call `cmd.Start` on linux, that C code would run.
Because `nsexec()` must be run before the Go runtime in order to use the
Linux kernel namespace, you must `import` this library into a package if
you plan to use `libcontainer` directly. Otherwise Go will not execute
the `nsexec()` constructor, which means that the re-exec will not cause
the namespaces to be joined. You can import it like this:
```go
import _ "github.com/opencontainers/runc/libcontainer/nsenter"
```
`nsexec()` will first get the file descriptor number for the init pipe
from the environment variable `_LIBCONTAINER_INITPIPE` (which was opened
by the parent and kept open across the fork-exec of the `nsexec()` init
process). The init pipe is used to read bootstrap data (namespace paths,
clone flags, uid and gid mappings, and the console path) from the parent
process. `nsexec()` will then call `setns(2)` to join the namespaces
provided in the bootstrap data (if available), `clone(2)` a child process
with the provided clone flags, update the user and group ID mappings, do
some further miscellaneous setup steps, and then send the PID of the
child process to the parent of the `nsexec()` "caller". Finally,
the parent `nsexec()` will exit and the child `nsexec()` process will
return to allow the Go runtime take over.
NOTE: We do both `setns(2)` and `clone(2)` even if we don't have any
CLONE_NEW* clone flags because we must fork a new process in order to
enter the PID namespace.

32
vendor/github.com/opencontainers/runc/libcontainer/nsenter/namespace.h generated vendored Normal file
View File

@@ -0,0 +1,32 @@
#ifndef NSENTER_NAMESPACE_H
#define NSENTER_NAMESPACE_H
#ifndef _GNU_SOURCE
# define _GNU_SOURCE
#endif
#include <sched.h>
/* All of these are taken from include/uapi/linux/sched.h */
#ifndef CLONE_NEWNS
# define CLONE_NEWNS 0x00020000 /* New mount namespace group */
#endif
#ifndef CLONE_NEWCGROUP
# define CLONE_NEWCGROUP 0x02000000 /* New cgroup namespace */
#endif
#ifndef CLONE_NEWUTS
# define CLONE_NEWUTS 0x04000000 /* New utsname namespace */
#endif
#ifndef CLONE_NEWIPC
# define CLONE_NEWIPC 0x08000000 /* New ipc namespace */
#endif
#ifndef CLONE_NEWUSER
# define CLONE_NEWUSER 0x10000000 /* New user namespace */
#endif
#ifndef CLONE_NEWPID
# define CLONE_NEWPID 0x20000000 /* New pid namespace */
#endif
#ifndef CLONE_NEWNET
# define CLONE_NEWNET 0x40000000 /* New network namespace */
#endif
#endif /* NSENTER_NAMESPACE_H */

12
vendor/github.com/opencontainers/runc/libcontainer/nsenter/nsenter.go generated vendored Normal file
View File

@@ -0,0 +1,12 @@
// +build linux,!gccgo
package nsenter
/*
#cgo CFLAGS: -Wall
extern void nsexec();
void __attribute__((constructor)) init(void) {
nsexec();
}
*/
import "C"

25
vendor/github.com/opencontainers/runc/libcontainer/nsenter/nsenter_gccgo.go generated vendored Normal file
View File

@@ -0,0 +1,25 @@
// +build linux,gccgo
package nsenter
/*
#cgo CFLAGS: -Wall
extern void nsexec();
void __attribute__((constructor)) init(void) {
nsexec();
}
*/
import "C"
// AlwaysFalse is here to stay false
// (and be exported so the compiler doesn't optimize out its reference)
var AlwaysFalse bool
func init() {
if AlwaysFalse {
// by referencing this C init() in a noop test, it will ensure the compiler
// links in the C function.
// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65134
C.init()
}
}

5
vendor/github.com/opencontainers/runc/libcontainer/nsenter/nsenter_unsupported.go generated vendored Normal file
View File

@@ -0,0 +1,5 @@
// +build !linux !cgo
package nsenter
import "C"

963
vendor/github.com/opencontainers/runc/libcontainer/nsenter/nsexec.c generated vendored Normal file
View File

@@ -0,0 +1,963 @@
#define _GNU_SOURCE
#include <endian.h>
#include <errno.h>
#include <fcntl.h>
#include <grp.h>
#include <sched.h>
#include <setjmp.h>
#include <signal.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/prctl.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <linux/limits.h>
#include <linux/netlink.h>
#include <linux/types.h>
/* Get all of the CLONE_NEW* flags. */
#include "namespace.h"
/* Synchronisation values. */
enum sync_t {
SYNC_USERMAP_PLS = 0x40, /* Request parent to map our users. */
SYNC_USERMAP_ACK = 0x41, /* Mapping finished by the parent. */
SYNC_RECVPID_PLS = 0x42, /* Tell parent we're sending the PID. */
SYNC_RECVPID_ACK = 0x43, /* PID was correctly received by parent. */
SYNC_GRANDCHILD = 0x44, /* The grandchild is ready to run. */
SYNC_CHILD_READY = 0x45, /* The child or grandchild is ready to return. */
/* XXX: This doesn't help with segfaults and other such issues. */
SYNC_ERR = 0xFF, /* Fatal error, no turning back. The error code follows. */
};
/* longjmp() arguments. */
#define JUMP_PARENT 0x00
#define JUMP_CHILD 0xA0
#define JUMP_INIT 0xA1
/* JSON buffer. */
#define JSON_MAX 4096
/* Assume the stack grows down, so arguments should be above it. */
struct clone_t {
/*
* Reserve some space for clone() to locate arguments
* and retcode in this place
*/
char stack[4096] __attribute__ ((aligned(16)));
char stack_ptr[0];
/* There's two children. This is used to execute the different code. */
jmp_buf *env;
int jmpval;
};
struct nlconfig_t {
char *data;
/* Process settings. */
uint32_t cloneflags;
char *oom_score_adj;
size_t oom_score_adj_len;
/* User namespace settings. */
char *uidmap;
size_t uidmap_len;
char *gidmap;
size_t gidmap_len;
char *namespaces;
size_t namespaces_len;
uint8_t is_setgroup;
/* Rootless container settings. */
uint8_t is_rootless;
char *uidmappath;
size_t uidmappath_len;
char *gidmappath;
size_t gidmappath_len;
};
/*
* List of netlink message types sent to us as part of bootstrapping the init.
* These constants are defined in libcontainer/message_linux.go.
*/
#define INIT_MSG 62000
#define CLONE_FLAGS_ATTR 27281
#define NS_PATHS_ATTR 27282
#define UIDMAP_ATTR 27283
#define GIDMAP_ATTR 27284
#define SETGROUP_ATTR 27285
#define OOM_SCORE_ADJ_ATTR 27286
#define ROOTLESS_ATTR 27287
#define UIDMAPPATH_ATTR 27288
#define GIDMAPPATH_ATTR 27289
/*
* Use the raw syscall for versions of glibc which don't include a function for
* it, namely (glibc 2.12).
*/
#if __GLIBC__ == 2 && __GLIBC_MINOR__ < 14
# define _GNU_SOURCE
# include "syscall.h"
# if !defined(SYS_setns) && defined(__NR_setns)
# define SYS_setns __NR_setns
# endif
#ifndef SYS_setns
# error "setns(2) syscall not supported by glibc version"
#endif
int setns(int fd, int nstype)
{
return syscall(SYS_setns, fd, nstype);
}
#endif
/* XXX: This is ugly. */
static int syncfd = -1;
/* TODO(cyphar): Fix this so it correctly deals with syncT. */
#define bail(fmt, ...) \
do { \
int ret = __COUNTER__ + 1; \
fprintf(stderr, "nsenter: " fmt ": %m\n", ##__VA_ARGS__); \
if (syncfd >= 0) { \
enum sync_t s = SYNC_ERR; \
if (write(syncfd, &s, sizeof(s)) != sizeof(s)) \
fprintf(stderr, "nsenter: failed: write(s)"); \
if (write(syncfd, &ret, sizeof(ret)) != sizeof(ret)) \
fprintf(stderr, "nsenter: failed: write(ret)"); \
} \
exit(ret); \
} while(0)
static int write_file(char *data, size_t data_len, char *pathfmt, ...)
{
int fd, len, ret = 0;
char path[PATH_MAX];
va_list ap;
va_start(ap, pathfmt);
len = vsnprintf(path, PATH_MAX, pathfmt, ap);
va_end(ap);
if (len < 0)
return -1;
fd = open(path, O_RDWR);
if (fd < 0) {
return -1;
}
len = write(fd, data, data_len);
if (len != data_len) {
ret = -1;
goto out;
}
out:
close(fd);
return ret;
}
enum policy_t {
SETGROUPS_DEFAULT = 0,
SETGROUPS_ALLOW,
SETGROUPS_DENY,
};
/* This *must* be called before we touch gid_map. */
static void update_setgroups(int pid, enum policy_t setgroup)
{
char *policy;
switch (setgroup) {
case SETGROUPS_ALLOW:
policy = "allow";
break;
case SETGROUPS_DENY:
policy = "deny";
break;
case SETGROUPS_DEFAULT:
default:
/* Nothing to do. */
return;
}
if (write_file(policy, strlen(policy), "/proc/%d/setgroups", pid) < 0) {
/*
* If the kernel is too old to support /proc/pid/setgroups,
* open(2) or write(2) will return ENOENT. This is fine.
*/
if (errno != ENOENT)
bail("failed to write '%s' to /proc/%d/setgroups", policy, pid);
}
}
static int try_mapping_tool(const char *app, int pid, char *map, size_t map_len)
{
int child;
/*
* If @app is NULL, execve will segfault. Just check it here and bail (if
* we're in this path, the caller is already getting desparate and there
* isn't a backup to this failing). This usually would be a configuration
* or programming issue.
*/
if (!app)
bail("mapping tool not present");
child = fork();
if (child < 0)
bail("failed to fork");
if (!child) {
#define MAX_ARGV 20
char *argv[MAX_ARGV];
char *envp[] = { NULL };
char pid_fmt[16];
int argc = 0;
char *next;
snprintf(pid_fmt, 16, "%d", pid);
argv[argc++] = (char *)app;
argv[argc++] = pid_fmt;
/*
* Convert the map string into a list of argument that
* newuidmap/newgidmap can understand.
*/
while (argc < MAX_ARGV) {
if (*map == '\0') {
argv[argc++] = NULL;
break;
}
argv[argc++] = map;
next = strpbrk(map, "\n ");
if (next == NULL)
break;
*next++ = '\0';
map = next + strspn(next, "\n ");
}
execve(app, argv, envp);
bail("failed to execv");
} else {
int status;
while (true) {
if (waitpid(child, &status, 0) < 0) {
if (errno == EINTR)
continue;
bail("failed to waitpid");
}
if (WIFEXITED(status) || WIFSIGNALED(status))
return WEXITSTATUS(status);
}
}
return -1;
}
static void update_uidmap(const char *path, int pid, char *map, size_t map_len)
{
if (map == NULL || map_len <= 0)
return;
if (write_file(map, map_len, "/proc/%d/uid_map", pid) < 0) {
if (errno != EPERM)
bail("failed to update /proc/%d/uid_map", pid);
if (try_mapping_tool(path, pid, map, map_len))
bail("failed to use newuid map on %d", pid);
}
}
static void update_gidmap(const char *path, int pid, char *map, size_t map_len)
{
if (map == NULL || map_len <= 0)
return;
if (write_file(map, map_len, "/proc/%d/gid_map", pid) < 0) {
if (errno != EPERM)
bail("failed to update /proc/%d/gid_map", pid);
if (try_mapping_tool(path, pid, map, map_len))
bail("failed to use newgid map on %d", pid);
}
}
static void update_oom_score_adj(char *data, size_t len)
{
if (data == NULL || len <= 0)
return;
if (write_file(data, len, "/proc/self/oom_score_adj") < 0)
bail("failed to update /proc/self/oom_score_adj");
}
/* A dummy function that just jumps to the given jumpval. */
static int child_func(void *arg) __attribute__ ((noinline));
static int child_func(void *arg)
{
struct clone_t *ca = (struct clone_t *)arg;
longjmp(*ca->env, ca->jmpval);
}
static int clone_parent(jmp_buf *env, int jmpval) __attribute__ ((noinline));
static int clone_parent(jmp_buf *env, int jmpval)
{
struct clone_t ca = {
.env = env,
.jmpval = jmpval,
};
return clone(child_func, ca.stack_ptr, CLONE_PARENT | SIGCHLD, &ca);
}
/*
* Gets the init pipe fd from the environment, which is used to read the
* bootstrap data and tell the parent what the new pid is after we finish
* setting up the environment.
*/
static int initpipe(void)
{
int pipenum;
char *initpipe, *endptr;
initpipe = getenv("_LIBCONTAINER_INITPIPE");
if (initpipe == NULL || *initpipe == '\0')
return -1;
pipenum = strtol(initpipe, &endptr, 10);
if (*endptr != '\0')
bail("unable to parse _LIBCONTAINER_INITPIPE");
return pipenum;
}
/* Returns the clone(2) flag for a namespace, given the name of a namespace. */
static int nsflag(char *name)
{
if (!strcmp(name, "cgroup"))
return CLONE_NEWCGROUP;
else if (!strcmp(name, "ipc"))
return CLONE_NEWIPC;
else if (!strcmp(name, "mnt"))
return CLONE_NEWNS;
else if (!strcmp(name, "net"))
return CLONE_NEWNET;
else if (!strcmp(name, "pid"))
return CLONE_NEWPID;
else if (!strcmp(name, "user"))
return CLONE_NEWUSER;
else if (!strcmp(name, "uts"))
return CLONE_NEWUTS;
/* If we don't recognise a name, fallback to 0. */
return 0;
}
static uint32_t readint32(char *buf)
{
return *(uint32_t *) buf;
}
static uint8_t readint8(char *buf)
{
return *(uint8_t *) buf;
}
static void nl_parse(int fd, struct nlconfig_t *config)
{
size_t len, size;
struct nlmsghdr hdr;
char *data, *current;
/* Retrieve the netlink header. */
len = read(fd, &hdr, NLMSG_HDRLEN);
if (len != NLMSG_HDRLEN)
bail("invalid netlink header length %zu", len);
if (hdr.nlmsg_type == NLMSG_ERROR)
bail("failed to read netlink message");
if (hdr.nlmsg_type != INIT_MSG)
bail("unexpected msg type %d", hdr.nlmsg_type);
/* Retrieve data. */
size = NLMSG_PAYLOAD(&hdr, 0);
current = data = malloc(size);
if (!data)
bail("failed to allocate %zu bytes of memory for nl_payload", size);
len = read(fd, data, size);
if (len != size)
bail("failed to read netlink payload, %zu != %zu", len, size);
/* Parse the netlink payload. */
config->data = data;
while (current < data + size) {
struct nlattr *nlattr = (struct nlattr *)current;
size_t payload_len = nlattr->nla_len - NLA_HDRLEN;
/* Advance to payload. */
current += NLA_HDRLEN;
/* Handle payload. */
switch (nlattr->nla_type) {
case CLONE_FLAGS_ATTR:
config->cloneflags = readint32(current);
break;
case ROOTLESS_ATTR:
config->is_rootless = readint8(current);
break;
case OOM_SCORE_ADJ_ATTR:
config->oom_score_adj = current;
config->oom_score_adj_len = payload_len;
break;
case NS_PATHS_ATTR:
config->namespaces = current;
config->namespaces_len = payload_len;
break;
case UIDMAP_ATTR:
config->uidmap = current;
config->uidmap_len = payload_len;
break;
case GIDMAP_ATTR:
config->gidmap = current;
config->gidmap_len = payload_len;
break;
case UIDMAPPATH_ATTR:
config->uidmappath = current;
config->uidmappath_len = payload_len;
break;
case GIDMAPPATH_ATTR:
config->gidmappath = current;
config->gidmappath_len = payload_len;
break;
case SETGROUP_ATTR:
config->is_setgroup = readint8(current);
break;
default:
bail("unknown netlink message type %d", nlattr->nla_type);
}
current += NLA_ALIGN(payload_len);
}
}
void nl_free(struct nlconfig_t *config)
{
free(config->data);
}
void join_namespaces(char *nslist)
{
int num = 0, i;
char *saveptr = NULL;
char *namespace = strtok_r(nslist, ",", &saveptr);
struct namespace_t {
int fd;
int ns;
char type[PATH_MAX];
char path[PATH_MAX];
} *namespaces = NULL;
if (!namespace || !strlen(namespace) || !strlen(nslist))
bail("ns paths are empty");
/*
* We have to open the file descriptors first, since after
* we join the mnt namespace we might no longer be able to
* access the paths.
*/
do {
int fd;
char *path;
struct namespace_t *ns;
/* Resize the namespace array. */
namespaces = realloc(namespaces, ++num * sizeof(struct namespace_t));
if (!namespaces)
bail("failed to reallocate namespace array");
ns = &namespaces[num - 1];
/* Split 'ns:path'. */
path = strstr(namespace, ":");
if (!path)
bail("failed to parse %s", namespace);
*path++ = '\0';
fd = open(path, O_RDONLY);
if (fd < 0)
bail("failed to open %s", path);
ns->fd = fd;
ns->ns = nsflag(namespace);
strncpy(ns->path, path, PATH_MAX);
} while ((namespace = strtok_r(NULL, ",", &saveptr)) != NULL);
/*
* The ordering in which we join namespaces is important. We should
* always join the user namespace *first*. This is all guaranteed
* from the container_linux.go side of this, so we're just going to
* follow the order given to us.
*/
for (i = 0; i < num; i++) {
struct namespace_t ns = namespaces[i];
if (setns(ns.fd, ns.ns) < 0)
bail("failed to setns to %s", ns.path);
close(ns.fd);
}
free(namespaces);
}
void nsexec(void)
{
int pipenum;
jmp_buf env;
int sync_child_pipe[2], sync_grandchild_pipe[2];
struct nlconfig_t config = { 0 };
/*
* If we don't have an init pipe, just return to the go routine.
* We'll only get an init pipe for start or exec.
*/
pipenum = initpipe();
if (pipenum == -1)
return;
/* Parse all of the netlink configuration. */
nl_parse(pipenum, &config);
/* Set oom_score_adj. This has to be done before !dumpable because
* /proc/self/oom_score_adj is not writeable unless you're an privileged
* user (if !dumpable is set). All children inherit their parent's
* oom_score_adj value on fork(2) so this will always be propagated
* properly.
*/
update_oom_score_adj(config.oom_score_adj, config.oom_score_adj_len);
/*
* Make the process non-dumpable, to avoid various race conditions that
* could cause processes in namespaces we're joining to access host
* resources (or potentially execute code).
*
* However, if the number of namespaces we are joining is 0, we are not
* going to be switching to a different security context. Thus setting
* ourselves to be non-dumpable only breaks things (like rootless
* containers), which is the recommendation from the kernel folks.
*/
if (config.namespaces) {
if (prctl(PR_SET_DUMPABLE, 0, 0, 0, 0) < 0)
bail("failed to set process as non-dumpable");
}
/* Pipe so we can tell the child when we've finished setting up. */
if (socketpair(AF_LOCAL, SOCK_STREAM, 0, sync_child_pipe) < 0)
bail("failed to setup sync pipe between parent and child");
/*
* We need a new socketpair to sync with grandchild so we don't have
* race condition with child.
*/
if (socketpair(AF_LOCAL, SOCK_STREAM, 0, sync_grandchild_pipe) < 0)
bail("failed to setup sync pipe between parent and grandchild");
/* TODO: Currently we aren't dealing with child deaths properly. */
/*
* Okay, so this is quite annoying.
*
* In order for this unsharing code to be more extensible we need to split
* up unshare(CLONE_NEWUSER) and clone() in various ways. The ideal case
* would be if we did clone(CLONE_NEWUSER) and the other namespaces
* separately, but because of SELinux issues we cannot really do that. But
* we cannot just dump the namespace flags into clone(...) because several
* usecases (such as rootless containers) require more granularity around
* the namespace setup. In addition, some older kernels had issues where
* CLONE_NEWUSER wasn't handled before other namespaces (but we cannot
* handle this while also dealing with SELinux so we choose SELinux support
* over broken kernel support).
*
* However, if we unshare(2) the user namespace *before* we clone(2), then
* all hell breaks loose.
*
* The parent no longer has permissions to do many things (unshare(2) drops
* all capabilities in your old namespace), and the container cannot be set
* up to have more than one {uid,gid} mapping. This is obviously less than
* ideal. In order to fix this, we have to first clone(2) and then unshare.
*
* Unfortunately, it's not as simple as that. We have to fork to enter the
* PID namespace (the PID namespace only applies to children). Since we'll
* have to double-fork, this clone_parent() call won't be able to get the
* PID of the _actual_ init process (without doing more synchronisation than
* I can deal with at the moment). So we'll just get the parent to send it
* for us, the only job of this process is to update
* /proc/pid/{setgroups,uid_map,gid_map}.
*
* And as a result of the above, we also need to setns(2) in the first child
* because if we join a PID namespace in the topmost parent then our child
* will be in that namespace (and it will not be able to give us a PID value
* that makes sense without resorting to sending things with cmsg).
*
* This also deals with an older issue caused by dumping cloneflags into
* clone(2): On old kernels, CLONE_PARENT didn't work with CLONE_NEWPID, so
* we have to unshare(2) before clone(2) in order to do this. This was fixed
* in upstream commit 1f7f4dde5c945f41a7abc2285be43d918029ecc5, and was
* introduced by 40a0d32d1eaffe6aac7324ca92604b6b3977eb0e. As far as we're
* aware, the last mainline kernel which had this bug was Linux 3.12.
* However, we cannot comment on which kernels the broken patch was
* backported to.
*
* -- Aleksa "what has my life come to?" Sarai
*/
switch (setjmp(env)) {
/*
* Stage 0: We're in the parent. Our job is just to create a new child
* (stage 1: JUMP_CHILD) process and write its uid_map and
* gid_map. That process will go on to create a new process, then
* it will send us its PID which we will send to the bootstrap
* process.
*/
case JUMP_PARENT:{
int len;
pid_t child, first_child = -1;
char buf[JSON_MAX];
bool ready = false;
/* For debugging. */
prctl(PR_SET_NAME, (unsigned long)"runc:[0:PARENT]", 0, 0, 0);
/* Start the process of getting a container. */
child = clone_parent(&env, JUMP_CHILD);
if (child < 0)
bail("unable to fork: child_func");
/*
* State machine for synchronisation with the children.
*
* Father only return when both child and grandchild are
* ready, so we can receive all possible error codes
* generated by children.
*/
while (!ready) {
enum sync_t s;
int ret;
syncfd = sync_child_pipe[1];
close(sync_child_pipe[0]);
if (read(syncfd, &s, sizeof(s)) != sizeof(s))
bail("failed to sync with child: next state");
switch (s) {
case SYNC_ERR:
/* We have to mirror the error code of the child. */
if (read(syncfd, &ret, sizeof(ret)) != sizeof(ret))
bail("failed to sync with child: read(error code)");
exit(ret);
case SYNC_USERMAP_PLS:
/*
* Enable setgroups(2) if we've been asked to. But we also
* have to explicitly disable setgroups(2) if we're
* creating a rootless container (this is required since
* Linux 3.19).
*/
if (config.is_rootless && config.is_setgroup) {
kill(child, SIGKILL);
bail("cannot allow setgroup in an unprivileged user namespace setup");
}
if (config.is_setgroup)
update_setgroups(child, SETGROUPS_ALLOW);
if (config.is_rootless)
update_setgroups(child, SETGROUPS_DENY);
/* Set up mappings. */
update_uidmap(config.uidmappath, child, config.uidmap, config.uidmap_len);
update_gidmap(config.gidmappath, child, config.gidmap, config.gidmap_len);
s = SYNC_USERMAP_ACK;
if (write(syncfd, &s, sizeof(s)) != sizeof(s)) {
kill(child, SIGKILL);
bail("failed to sync with child: write(SYNC_USERMAP_ACK)");
}
break;
case SYNC_RECVPID_PLS:{
first_child = child;
/* Get the init_func pid. */
if (read(syncfd, &child, sizeof(child)) != sizeof(child)) {
kill(first_child, SIGKILL);
bail("failed to sync with child: read(childpid)");
}
/* Send ACK. */
s = SYNC_RECVPID_ACK;
if (write(syncfd, &s, sizeof(s)) != sizeof(s)) {
kill(first_child, SIGKILL);
kill(child, SIGKILL);
bail("failed to sync with child: write(SYNC_RECVPID_ACK)");
}
}
break;
case SYNC_CHILD_READY:
ready = true;
break;
default:
bail("unexpected sync value: %u", s);
}
}
/* Now sync with grandchild. */
ready = false;
while (!ready) {
enum sync_t s;
int ret;
syncfd = sync_grandchild_pipe[1];
close(sync_grandchild_pipe[0]);
s = SYNC_GRANDCHILD;
if (write(syncfd, &s, sizeof(s)) != sizeof(s)) {
kill(child, SIGKILL);
bail("failed to sync with child: write(SYNC_GRANDCHILD)");
}
if (read(syncfd, &s, sizeof(s)) != sizeof(s))
bail("failed to sync with child: next state");
switch (s) {
case SYNC_ERR:
/* We have to mirror the error code of the child. */
if (read(syncfd, &ret, sizeof(ret)) != sizeof(ret))
bail("failed to sync with child: read(error code)");
exit(ret);
case SYNC_CHILD_READY:
ready = true;
break;
default:
bail("unexpected sync value: %u", s);
}
}
/*
* Send the init_func pid and the pid of the first child back to our parent.
*
* We need to send both back because we can't reap the first child we created (CLONE_PARENT).
* It becomes the responsibility of our parent to reap the first child.
*/
len = snprintf(buf, JSON_MAX, "{\"pid\": %d, \"pid_first\": %d}\n", child, first_child);
if (len < 0) {
kill(child, SIGKILL);
bail("unable to generate JSON for child pid");
}
if (write(pipenum, buf, len) != len) {
kill(child, SIGKILL);
bail("unable to send child pid to bootstrapper");
}
exit(0);
}
/*
* Stage 1: We're in the first child process. Our job is to join any
* provided namespaces in the netlink payload and unshare all
* of the requested namespaces. If we've been asked to
* CLONE_NEWUSER, we will ask our parent (stage 0) to set up
* our user mappings for us. Then, we create a new child
* (stage 2: JUMP_INIT) for PID namespace. We then send the
* child's PID to our parent (stage 0).
*/
case JUMP_CHILD:{
pid_t child;
enum sync_t s;
/* We're in a child and thus need to tell the parent if we die. */
syncfd = sync_child_pipe[0];
close(sync_child_pipe[1]);
/* For debugging. */
prctl(PR_SET_NAME, (unsigned long)"runc:[1:CHILD]", 0, 0, 0);
/*
* We need to setns first. We cannot do this earlier (in stage 0)
* because of the fact that we forked to get here (the PID of
* [stage 2: JUMP_INIT]) would be meaningless). We could send it
* using cmsg(3) but that's just annoying.
*/
if (config.namespaces)
join_namespaces(config.namespaces);
/*
* Unshare all of the namespaces. Now, it should be noted that this
* ordering might break in the future (especially with rootless
* containers). But for now, it's not possible to split this into
* CLONE_NEWUSER + [the rest] because of some RHEL SELinux issues.
*
* Note that we don't merge this with clone() because there were
* some old kernel versions where clone(CLONE_PARENT | CLONE_NEWPID)
* was broken, so we'll just do it the long way anyway.
*/
if (unshare(config.cloneflags) < 0)
bail("failed to unshare namespaces");
/*
* Deal with user namespaces first. They are quite special, as they
* affect our ability to unshare other namespaces and are used as
* context for privilege checks.
*/
if (config.cloneflags & CLONE_NEWUSER) {
/*
* We don't have the privileges to do any mapping here (see the
* clone_parent rant). So signal our parent to hook us up.
*/
/* Switching is only necessary if we joined namespaces. */
if (config.namespaces) {
if (prctl(PR_SET_DUMPABLE, 1, 0, 0, 0) < 0)
bail("failed to set process as dumpable");
}
s = SYNC_USERMAP_PLS;
if (write(syncfd, &s, sizeof(s)) != sizeof(s))
bail("failed to sync with parent: write(SYNC_USERMAP_PLS)");
/* ... wait for mapping ... */
if (read(syncfd, &s, sizeof(s)) != sizeof(s))
bail("failed to sync with parent: read(SYNC_USERMAP_ACK)");
if (s != SYNC_USERMAP_ACK)
bail("failed to sync with parent: SYNC_USERMAP_ACK: got %u", s);
/* Switching is only necessary if we joined namespaces. */
if (config.namespaces) {
if (prctl(PR_SET_DUMPABLE, 0, 0, 0, 0) < 0)
bail("failed to set process as dumpable");
}
}
/*
* TODO: What about non-namespace clone flags that we're dropping here?
*
* We fork again because of PID namespace, setns(2) or unshare(2) don't
* change the PID namespace of the calling process, because doing so
* would change the caller's idea of its own PID (as reported by getpid()),
* which would break many applications and libraries, so we must fork
* to actually enter the new PID namespace.
*/
child = clone_parent(&env, JUMP_INIT);
if (child < 0)
bail("unable to fork: init_func");
/* Send the child to our parent, which knows what it's doing. */
s = SYNC_RECVPID_PLS;
if (write(syncfd, &s, sizeof(s)) != sizeof(s)) {
kill(child, SIGKILL);
bail("failed to sync with parent: write(SYNC_RECVPID_PLS)");
}
if (write(syncfd, &child, sizeof(child)) != sizeof(child)) {
kill(child, SIGKILL);
bail("failed to sync with parent: write(childpid)");
}
/* ... wait for parent to get the pid ... */
if (read(syncfd, &s, sizeof(s)) != sizeof(s)) {
kill(child, SIGKILL);
bail("failed to sync with parent: read(SYNC_RECVPID_ACK)");
}
if (s != SYNC_RECVPID_ACK) {
kill(child, SIGKILL);
bail("failed to sync with parent: SYNC_RECVPID_ACK: got %u", s);
}
s = SYNC_CHILD_READY;
if (write(syncfd, &s, sizeof(s)) != sizeof(s)) {
kill(child, SIGKILL);
bail("failed to sync with parent: write(SYNC_CHILD_READY)");
}
/* Our work is done. [Stage 2: JUMP_INIT] is doing the rest of the work. */
exit(0);
}
/*
* Stage 2: We're the final child process, and the only process that will
* actually return to the Go runtime. Our job is to just do the
* final cleanup steps and then return to the Go runtime to allow
* init_linux.go to run.
*/
case JUMP_INIT:{
/*
* We're inside the child now, having jumped from the
* start_child() code after forking in the parent.
*/
enum sync_t s;
/* We're in a child and thus need to tell the parent if we die. */
syncfd = sync_grandchild_pipe[0];
close(sync_grandchild_pipe[1]);
close(sync_child_pipe[0]);
close(sync_child_pipe[1]);
/* For debugging. */
prctl(PR_SET_NAME, (unsigned long)"runc:[2:INIT]", 0, 0, 0);
if (read(syncfd, &s, sizeof(s)) != sizeof(s))
bail("failed to sync with parent: read(SYNC_GRANDCHILD)");
if (s != SYNC_GRANDCHILD)
bail("failed to sync with parent: SYNC_GRANDCHILD: got %u", s);
if (setsid() < 0)
bail("setsid failed");
if (setuid(0) < 0)
bail("setuid failed");
if (setgid(0) < 0)
bail("setgid failed");
if (!config.is_rootless && config.is_setgroup) {
if (setgroups(0, NULL) < 0)
bail("setgroups failed");
}
s = SYNC_CHILD_READY;
if (write(syncfd, &s, sizeof(s)) != sizeof(s))
bail("failed to sync with patent: write(SYNC_CHILD_READY)");
/* Close sync pipes. */
close(sync_grandchild_pipe[0]);
/* Free netlink data. */
nl_free(&config);
/* Finish executing, let the Go runtime take over. */
return;
}
default:
bail("unexpected jump value");
}
/* Should never be reached. */
bail("should never be reached");
}