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Diffstat (limited to 'pkg/rootless/rootless.go')
-rw-r--r--pkg/rootless/rootless.go145
1 files changed, 145 insertions, 0 deletions
diff --git a/pkg/rootless/rootless.go b/pkg/rootless/rootless.go
new file mode 100644
index 000000000..737fc91c7
--- /dev/null
+++ b/pkg/rootless/rootless.go
@@ -0,0 +1,145 @@
+package rootless
+
+import (
+ "fmt"
+ "io/ioutil"
+ "os"
+ "os/exec"
+ gosignal "os/signal"
+ "runtime"
+ "syscall"
+
+ "github.com/containers/storage/pkg/idtools"
+ "github.com/docker/docker/pkg/signal"
+ "github.com/pkg/errors"
+)
+
+/*
+extern int reexec_in_user_namespace(int ready);
+extern int reexec_in_user_namespace_wait(int pid);
+*/
+import "C"
+
+func runInUser() error {
+ os.Setenv("_LIBPOD_USERNS_CONFIGURED", "done")
+ return nil
+}
+
+// IsRootless tells us if we are running in rootless mode
+func IsRootless() bool {
+ return os.Getuid() != 0 || os.Getenv("_LIBPOD_USERNS_CONFIGURED") != ""
+}
+
+func tryMappingTool(tool string, pid int, hostID int, mappings []idtools.IDMap) error {
+ path, err := exec.LookPath(tool)
+ if err != nil {
+ return err
+ }
+
+ appendTriplet := func(l []string, a, b, c int) []string {
+ return append(l, fmt.Sprintf("%d", a), fmt.Sprintf("%d", b), fmt.Sprintf("%d", c))
+ }
+
+ args := []string{path, fmt.Sprintf("%d", pid)}
+ args = appendTriplet(args, 0, hostID, 1)
+ if mappings != nil {
+ for _, i := range mappings {
+ args = appendTriplet(args, i.ContainerID+1, i.HostID, i.Size)
+ }
+ }
+ cmd := exec.Cmd{
+ Path: path,
+ Args: args,
+ }
+ return cmd.Run()
+}
+
+// BecomeRootInUserNS re-exec podman in a new userNS
+func BecomeRootInUserNS() (bool, error) {
+
+ if os.Getuid() == 0 || os.Getenv("_LIBPOD_USERNS_CONFIGURED") != "" {
+ if os.Getenv("_LIBPOD_USERNS_CONFIGURED") == "init" {
+ return false, runInUser()
+ }
+ return false, nil
+ }
+
+ runtime.LockOSThread()
+ defer runtime.UnlockOSThread()
+
+ r, w, err := os.Pipe()
+ if err != nil {
+ return false, err
+ }
+ defer r.Close()
+ defer w.Close()
+
+ pidC := C.reexec_in_user_namespace(C.int(r.Fd()))
+ pid := int(pidC)
+ if pid < 0 {
+ return false, errors.Errorf("cannot re-exec process")
+ }
+
+ setgroups := fmt.Sprintf("/proc/%d/setgroups", pid)
+ err = ioutil.WriteFile(setgroups, []byte("deny\n"), 0666)
+ if err != nil {
+ return false, errors.Wrapf(err, "cannot write setgroups file")
+ }
+
+ var uids, gids []idtools.IDMap
+ username := os.Getenv("USER")
+ mappings, err := idtools.NewIDMappings(username, username)
+ if err == nil {
+ uids = mappings.UIDs()
+ gids = mappings.GIDs()
+ }
+
+ uidsMapped := false
+ if mappings != nil && uids != nil {
+ uidsMapped = tryMappingTool("newuidmap", pid, os.Getuid(), uids) == nil
+ }
+ if !uidsMapped {
+ uidMap := fmt.Sprintf("/proc/%d/uid_map", pid)
+ err = ioutil.WriteFile(uidMap, []byte(fmt.Sprintf("%d %d 1\n", 0, os.Getuid())), 0666)
+ if err != nil {
+ return false, errors.Wrapf(err, "cannot write uid_map")
+ }
+ }
+
+ gidsMapped := false
+ if mappings != nil && gids != nil {
+ gidsMapped = tryMappingTool("newgidmap", pid, os.Getgid(), gids) == nil
+ }
+ if !gidsMapped {
+ gidMap := fmt.Sprintf("/proc/%d/gid_map", pid)
+ err = ioutil.WriteFile(gidMap, []byte(fmt.Sprintf("%d %d 1\n", 0, os.Getgid())), 0666)
+ if err != nil {
+ return false, errors.Wrapf(err, "cannot write gid_map")
+ }
+ }
+
+ _, err = w.Write([]byte("1"))
+ if err != nil {
+ return false, errors.Wrapf(err, "write to sync pipe")
+ }
+
+ c := make(chan os.Signal, 1)
+
+ gosignal.Notify(c)
+ defer gosignal.Reset()
+ go func() {
+ for s := range c {
+ if s == signal.SIGCHLD || s == signal.SIGPIPE {
+ continue
+ }
+
+ syscall.Kill(int(pidC), s.(syscall.Signal))
+ }
+ }()
+
+ if C.reexec_in_user_namespace_wait(pidC) < 0 {
+ return false, errors.Wrapf(err, "error waiting for the re-exec process")
+ }
+
+ return true, nil
+}