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//go:build linux || freebsd || darwin
package open
import (
"bytes"
"encoding/json"
"errors"
"fmt"
"os"
"syscall"
"github.com/containers/storage/pkg/reexec"
"golang.org/x/sys/unix"
)
const (
inChrootCommand = "buildah-open-in-chroot"
)
func init() {
reexec.Register(inChrootCommand, inChrootMain)
}
func inChroot(requests requests) results {
sock, err := unix.Socketpair(unix.AF_UNIX, unix.SOCK_STREAM, 0)
if err != nil {
return results{Err: fmt.Errorf("creating socket pair: %w", err).Error()}
}
parentSock := sock[0]
childSock := sock[1]
parentEnd := os.NewFile(uintptr(parentSock), "parent end of socket pair")
childEnd := os.NewFile(uintptr(childSock), "child end of socket pair")
cmd := reexec.Command(inChrootCommand)
cmd.ExtraFiles = append(cmd.ExtraFiles, childEnd)
err = cmd.Start()
childEnd.Close()
defer parentEnd.Close()
if err != nil {
return results{Err: err.Error()}
}
encoder := json.NewEncoder(parentEnd)
if err := encoder.Encode(&requests); err != nil {
return results{Err: fmt.Errorf("sending request down socket: %w", err).Error()}
}
if err := unix.Shutdown(parentSock, unix.SHUT_WR); err != nil {
return results{Err: fmt.Errorf("finishing sending request down socket: %w", err).Error()}
}
b := make([]byte, 65536)
oob := make([]byte, 65536)
n, oobn, _, _, err := unix.Recvmsg(parentSock, b, oob, 0)
if err != nil {
return results{Err: fmt.Errorf("receiving message: %w", err).Error()}
}
if err := unix.Shutdown(parentSock, unix.SHUT_RD); err != nil {
return results{Err: fmt.Errorf("finishing socket: %w", err).Error()}
}
if n > len(b) {
return results{Err: fmt.Errorf("too much regular data: %d > %d", n, len(b)).Error()}
}
if oobn > len(oob) {
return results{Err: fmt.Errorf("too much OOB data: %d > %d", oobn, len(oob)).Error()}
}
scms, err := unix.ParseSocketControlMessage(oob[:oobn])
if err != nil {
return results{Err: fmt.Errorf("parsing control message: %w", err).Error()}
}
var receivedFds []int
for i := range scms {
fds, err := unix.ParseUnixRights(&scms[i])
if err != nil {
return results{Err: fmt.Errorf("parsing rights message %d: %w", i, err).Error()}
}
receivedFds = append(receivedFds, fds...)
}
decoder := json.NewDecoder(bytes.NewReader(b[:n]))
var result results
if err := decoder.Decode(&result); err != nil {
return results{Err: fmt.Errorf("decoding results: %w", err).Error()}
}
j := 0
for i := range result.Open {
if result.Open[i].Err == "" {
if j >= len(receivedFds) {
for _, fd := range receivedFds {
unix.Close(fd)
}
return results{Err: fmt.Errorf("didn't receive enough FDs").Error()}
}
result.Open[i].Fd = uintptr(receivedFds[j])
j++
}
}
return result
}
func inChrootMain() {
var theseRequests requests
var theseResults results
sockFd := 3
sock := os.NewFile(uintptr(sockFd), "socket connection to parent process")
defer sock.Close()
encoder := json.NewEncoder(sock)
decoder := json.NewDecoder(sock)
if err := decoder.Decode(&theseRequests); err != nil {
if err := encoder.Encode(results{Err: fmt.Errorf("decoding request: %w", err).Error()}); err != nil {
os.Exit(1)
}
}
if theseRequests.Root != "" {
if err := os.Chdir(theseRequests.Root); err != nil {
if err := encoder.Encode(results{Err: fmt.Errorf("changing to %q: %w", theseRequests.Root, err).Error()}); err != nil {
os.Exit(1)
}
os.Exit(1)
}
if err := unix.Chroot(theseRequests.Root); err != nil {
if err := encoder.Encode(results{Err: fmt.Errorf("chrooting to %q: %w", theseRequests.Root, err).Error()}); err != nil {
os.Exit(1)
}
os.Exit(1)
}
if err := os.Chdir("/"); err != nil {
if err := encoder.Encode(results{Err: fmt.Errorf("changing to new root: %w", err).Error()}); err != nil {
os.Exit(1)
}
os.Exit(1)
}
}
if theseRequests.Wd != "" {
if err := os.Chdir(theseRequests.Wd); err != nil {
if err := encoder.Encode(results{Err: fmt.Errorf("changing to %q in chroot: %w", theseRequests.Wd, err).Error()}); err != nil {
os.Exit(1)
}
os.Exit(1)
}
}
var fds []int
for _, request := range theseRequests.Open {
fd, err := unix.Open(request.Path, request.Mode, request.Perms)
thisResult := result{Fd: uintptr(fd)}
if err == nil {
fds = append(fds, fd)
} else {
var errno syscall.Errno
thisResult.Err = err.Error()
if errors.As(err, &errno) {
thisResult.Errno = errno
}
}
theseResults.Open = append(theseResults.Open, thisResult)
}
rights := unix.UnixRights(fds...)
inband, err := json.Marshal(&theseResults)
if err != nil {
if err := encoder.Encode(results{Err: fmt.Errorf("sending response: %w", err).Error()}); err != nil {
os.Exit(1)
}
os.Exit(1)
}
if err := unix.Sendmsg(sockFd, inband, rights, nil, 0); err != nil {
if err := encoder.Encode(results{Err: fmt.Errorf("sending response: %w", err).Error()}); err != nil {
os.Exit(1)
}
os.Exit(1)
}
os.Exit(0)
}
|
