diff --git a/cmd/buildah/main.go b/cmd/buildah/main.go index 524d87b32b5..ec25f84dcc3 100644 --- a/cmd/buildah/main.go +++ b/cmd/buildah/main.go @@ -12,6 +12,7 @@ import ( "github.com/containers/buildah" "github.com/containers/buildah/define" + "github.com/containers/buildah/pkg/binfmt" "github.com/containers/buildah/pkg/cli" "github.com/containers/buildah/pkg/parse" "github.com/containers/common/pkg/config" @@ -40,6 +41,7 @@ type globalFlags struct { MemoryProfile string UserShortNameAliasConfPath string CgroupManager string + registerBinfmt bool } var rootCmd = &cobra.Command{ @@ -118,6 +120,10 @@ func init() { if err := rootCmd.PersistentFlags().MarkHidden("memory-profile"); err != nil { logrus.Fatalf("unable to mark memory-profile flag as hidden: %v", err) } + rootCmd.PersistentFlags().BoolVar(&globalFlagResults.registerBinfmt, "register-binfmt", os.Getenv("container") != "", "attempt to register binfmt_misc interpreters") + if err := rootCmd.PersistentFlags().MarkHidden("register-binfmt"); err != nil { + logrus.Fatalf("unable to mark register-binfmt flag as hidden: %v", err) + } } func initConfig() { @@ -147,6 +153,11 @@ func before(cmd *cobra.Command) error { } debugCapabilities() unshare.MaybeReexecUsingUserNamespace(false) + if globalFlagResults.registerBinfmt { + if err := binfmt.Register(nil); err != nil { + logrus.Debugf("registering binfmt_misc interpreters: %v", err) + } + } if globalFlagResults.CPUProfile != "" { globalFlagResults.cpuProfileFile, err = os.Create(globalFlagResults.CPUProfile) if err != nil { diff --git a/pkg/binfmt/binfmt.go b/pkg/binfmt/binfmt.go new file mode 100644 index 00000000000..e6f0ac62fc0 --- /dev/null +++ b/pkg/binfmt/binfmt.go @@ -0,0 +1,83 @@ +//go:build linux + +package binfmt + +import ( + "bufio" + "errors" + "fmt" + "os" + "path/filepath" + "strings" + "syscall" + + "github.com/containers/storage/pkg/unshare" + "github.com/sirupsen/logrus" + "golang.org/x/sys/unix" +) + +// MaybeRegister() calls Register() if the current context is a rootless one, +// or if the "container" environment variable suggests that we're in a +// container. +func MaybeRegister(configurationSearchDirectories []string) error { + if unshare.IsRootless() || os.Getenv("container") != "" { // we _also_ own our own mount namespace + return Register(configurationSearchDirectories) + } + return nil +} + +// Register() registers binfmt.d emulators described by configuration files in +// the passed-in slice of directories, or in the union of /etc/binfmt.d, +// /run/binfmt.d, and /usr/lib/binfmt.d if the slice has no items. If any +// emulators are configured, it will attempt to mount a binfmt_misc filesystem +// in the current mount namespace first, ignoring only EPERM and EACCES errors. +func Register(configurationSearchDirectories []string) error { + if len(configurationSearchDirectories) == 0 { + configurationSearchDirectories = []string{"/etc/binfmt.d", "/run/binfmt.d", "/usr/lib/binfmt.d"} + } + mounted := false + for _, searchDir := range configurationSearchDirectories { + globs, err := filepath.Glob(filepath.Join(searchDir, "*.conf")) + if err != nil { + return fmt.Errorf("looking for binfmt.d configuration in %q: %w", searchDir, err) + } + for _, conf := range globs { + f, err := os.Open(conf) + if err != nil { + return fmt.Errorf("reading binfmt.d configuration: %w", err) + } + scanner := bufio.NewScanner(f) + for scanner.Scan() { + line := strings.TrimSpace(scanner.Text()) + if len(line) == 0 || line[0] == ';' || line[0] == '#' { + continue + } + if !mounted { + if err = unix.Mount("none", "/proc/sys/fs/binfmt_misc", "binfmt_misc", 0, ""); err != nil { + if errors.Is(err, syscall.EPERM) || errors.Is(err, syscall.EACCES) { + // well, we tried. no need to make a stink about it + return nil + } + return fmt.Errorf("mounting binfmt_misc: %w", err) + } + mounted = true + } + reg, err := os.Create("/proc/sys/fs/binfmt_misc/register") + if err != nil { + return fmt.Errorf("registering(open): %w", err) + } + if _, err = fmt.Fprintf(reg, "%s\n", line); err != nil { + return fmt.Errorf("registering(write): %w", err) + } + logrus.Tracef("registered binfmt %q", line) + if err = reg.Close(); err != nil { + return fmt.Errorf("registering(close): %w", err) + } + } + if err := f.Close(); err != nil { + return fmt.Errorf("reading binfmt.d configuration: %w", err) + } + } + } + return nil +} diff --git a/pkg/binfmt/binfmt_unsupported.go b/pkg/binfmt/binfmt_unsupported.go new file mode 100644 index 00000000000..6bb1667e50c --- /dev/null +++ b/pkg/binfmt/binfmt_unsupported.go @@ -0,0 +1,15 @@ +//go:build !linux + +package binfmt + +import "syscall" + +// MaybeRegister() returns no error. +func MaybeRegister(configurationSearchDirectories []string) error { + return nil +} + +// Register() returns an error. +func Register(configurationSearchDirectories []string) error { + return syscall.ENOSYS +}