84 lines
2.6 KiB
Go
84 lines
2.6 KiB
Go
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//go:build linux
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package binfmt
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import (
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"bufio"
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"errors"
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"fmt"
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"os"
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"path/filepath"
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"strings"
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"syscall"
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"github.com/containers/storage/pkg/unshare"
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"github.com/sirupsen/logrus"
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"golang.org/x/sys/unix"
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)
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// MaybeRegister() calls Register() if the current context is a rootless one,
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// or if the "container" environment variable suggests that we're in a
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// container.
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func MaybeRegister(configurationSearchDirectories []string) error {
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if unshare.IsRootless() || os.Getenv("container") != "" { // we _also_ own our own mount namespace
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return Register(configurationSearchDirectories)
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}
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return nil
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}
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// Register() registers binfmt.d emulators described by configuration files in
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// the passed-in slice of directories, or in the union of /etc/binfmt.d,
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// /run/binfmt.d, and /usr/lib/binfmt.d if the slice has no items. If any
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// emulators are configured, it will attempt to mount a binfmt_misc filesystem
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// in the current mount namespace first, ignoring only EPERM and EACCES errors.
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func Register(configurationSearchDirectories []string) error {
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if len(configurationSearchDirectories) == 0 {
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configurationSearchDirectories = []string{"/etc/binfmt.d", "/run/binfmt.d", "/usr/lib/binfmt.d"}
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}
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mounted := false
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for _, searchDir := range configurationSearchDirectories {
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globs, err := filepath.Glob(filepath.Join(searchDir, "*.conf"))
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if err != nil {
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return fmt.Errorf("looking for binfmt.d configuration in %q: %w", searchDir, err)
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}
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for _, conf := range globs {
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f, err := os.Open(conf)
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if err != nil {
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return fmt.Errorf("reading binfmt.d configuration: %w", err)
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}
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scanner := bufio.NewScanner(f)
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for scanner.Scan() {
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line := strings.TrimSpace(scanner.Text())
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if len(line) == 0 || line[0] == ';' || line[0] == '#' {
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continue
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}
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if !mounted {
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if err = unix.Mount("none", "/proc/sys/fs/binfmt_misc", "binfmt_misc", 0, ""); err != nil {
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if errors.Is(err, syscall.EPERM) || errors.Is(err, syscall.EACCES) {
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// well, we tried. no need to make a stink about it
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return nil
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}
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return fmt.Errorf("mounting binfmt_misc: %w", err)
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}
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mounted = true
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}
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reg, err := os.Create("/proc/sys/fs/binfmt_misc/register")
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if err != nil {
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return fmt.Errorf("registering(open): %w", err)
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}
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if _, err = fmt.Fprintf(reg, "%s\n", line); err != nil {
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return fmt.Errorf("registering(write): %w", err)
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}
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logrus.Tracef("registered binfmt %q", line)
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if err = reg.Close(); err != nil {
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return fmt.Errorf("registering(close): %w", err)
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}
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}
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if err := f.Close(); err != nil {
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return fmt.Errorf("reading binfmt.d configuration: %w", err)
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}
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}
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}
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return nil
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}
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