container/init: wrap syscall helper functions

This allows tests to stub all kernel behaviour, enabling measurement of all function call arguments and error injection.

Signed-off-by: Ophestra <cat@gensokyo.uk>

container/dispatcher.go

@@ -0,0 +1,229 @@
+package container
+
+import (
+	"io"
+	"io/fs"
+	"log"
+	"os"
+	"os/exec"
+	"os/signal"
+	"path/filepath"
+	"syscall"
+
+	"hakurei.app/container/seccomp"
+)
+
+type osFile interface {
+	Name() string
+	io.Writer
+	fs.File
+}
+
+// syscallDispatcher provides methods that make state-dependent system calls as part of their behaviour.
+type syscallDispatcher interface {
+	// setPtracer provides [SetPtracer].
+	setPtracer(pid uintptr) error
+	// setDumpable provides [SetDumpable].
+	setDumpable(dumpable uintptr) error
+	// setNoNewPrivs provides [SetNoNewPrivs].
+	setNoNewPrivs() error
+
+	// lastcap provides [LastCap].
+	lastcap() uintptr
+	// capset provides capset.
+	capset(hdrp *capHeader, datap *[2]capData) error
+	// capBoundingSetDrop provides capBoundingSetDrop.
+	capBoundingSetDrop(cap uintptr) error
+	// capAmbientClearAll provides capAmbientClearAll.
+	capAmbientClearAll() error
+	// capAmbientRaise provides capAmbientRaise.
+	capAmbientRaise(cap uintptr) error
+	// isatty provides [Isatty].
+	isatty(fd int) bool
+	// receive provides [Receive].
+	receive(key string, e any, v **os.File) (closeFunc func() error, err error)
+
+	// bindMount provides procPaths.bindMount.
+	bindMount(source, target string, flags uintptr, eq bool) error
+	// remount provides procPaths.remount.
+	remount(target string, flags uintptr) error
+	// mountTmpfs provides mountTmpfs.
+	mountTmpfs(fsname, target string, flags uintptr, size int, perm os.FileMode) error
+	// ensureFile provides ensureFile.
+	ensureFile(name string, perm, pperm os.FileMode) error
+
+	// seccompLoad provides [seccomp.Load].
+	seccompLoad(rules []seccomp.NativeRule, flags seccomp.ExportFlag) error
+	// notify provides [signal.Notify].
+	notify(c chan<- os.Signal, sig ...os.Signal)
+	// start starts [os/exec.Cmd].
+	start(c *exec.Cmd) error
+	// signal signals the underlying process of [os/exec.Cmd].
+	signal(c *exec.Cmd, sig os.Signal) error
+	// evalSymlinks provides [filepath.EvalSymlinks].
+	evalSymlinks(path string) (string, error)
+
+	// exit provides [os.Exit].
+	exit(code int)
+	// getpid provides [os.Getpid].
+	getpid() int
+	// stat provides [os.Stat].
+	stat(name string) (os.FileInfo, error)
+	// mkdir provides [os.Mkdir].
+	mkdir(name string, perm os.FileMode) error
+	// mkdirTemp provides [os.MkdirTemp].
+	mkdirTemp(dir, pattern string) (string, error)
+	// mkdirAll provides [os.MkdirAll].
+	mkdirAll(path string, perm os.FileMode) error
+	// readdir provides [os.ReadDir].
+	readdir(name string) ([]os.DirEntry, error)
+	// writeFile provides [os.WriteFile].
+	writeFile(name string, data []byte, perm os.FileMode) error
+	// createTemp provides [os.CreateTemp].
+	createTemp(dir, pattern string) (osFile, error)
+	// remove provides os.Remove.
+	remove(name string) error
+	// newFile provides os.NewFile.
+	newFile(fd uintptr, name string) *os.File
+	// symlink provides os.Symlink.
+	symlink(oldname, newname string) error
+	// readlink provides [os.Readlink].
+	readlink(name string) (string, error)
+
+	// umask provides syscall.Umask.
+	umask(mask int) (oldmask int)
+	// sethostname provides syscall.Sethostname
+	sethostname(p []byte) (err error)
+	// chdir provides syscall.Chdir
+	chdir(path string) (err error)
+	// fchdir provides syscall.Fchdir
+	fchdir(fd int) (err error)
+	// open provides syscall.Open
+	open(path string, mode int, perm uint32) (fd int, err error)
+	// close provides syscall.Close
+	close(fd int) (err error)
+	// pivotRoot provides syscall.PivotRoot
+	pivotRoot(newroot, putold string) (err error)
+	// mount provides syscall.Mount
+	mount(source, target, fstype string, flags uintptr, data string) (err error)
+	// unmount provides syscall.Unmount
+	unmount(target string, flags int) (err error)
+	// wait4 provides syscall.Wait4
+	wait4(pid int, wstatus *syscall.WaitStatus, options int, rusage *syscall.Rusage) (wpid int, err error)
+
+	// printf provides [log.Printf].
+	printf(format string, v ...any)
+	// fatal provides [log.Fatal]
+	fatal(v ...any)
+	// fatalf provides [log.Fatalf]
+	fatalf(format string, v ...any)
+	// verbose provides [Msg.Verbose].
+	verbose(v ...any)
+	// verbosef provides [Msg.Verbosef].
+	verbosef(format string, v ...any)
+	// suspend provides [Msg.Suspend].
+	suspend()
+	// resume provides [Msg.Resume].
+	resume() bool
+	// beforeExit provides [Msg.BeforeExit].
+	beforeExit()
+	// printBaseErr provides [Msg.PrintBaseErr].
+	printBaseErr(err error, fallback string)
+}
+
+// direct implements syscallDispatcher on the current kernel.
+type direct struct{}
+
+func (direct) setPtracer(pid uintptr) error       { return SetPtracer(pid) }
+func (direct) setDumpable(dumpable uintptr) error { return SetDumpable(dumpable) }
+func (direct) setNoNewPrivs() error               { return SetNoNewPrivs() }
+
+func (direct) lastcap() uintptr                                { return LastCap() }
+func (direct) capset(hdrp *capHeader, datap *[2]capData) error { return capset(hdrp, datap) }
+func (direct) capBoundingSetDrop(cap uintptr) error            { return capBoundingSetDrop(cap) }
+func (direct) capAmbientClearAll() error                       { return capAmbientClearAll() }
+func (direct) capAmbientRaise(cap uintptr) error               { return capAmbientRaise(cap) }
+func (direct) isatty(fd int) bool                              { return Isatty(fd) }
+func (direct) receive(key string, e any, v **os.File) (func() error, error) {
+	return Receive(key, e, v)
+}
+
+func (direct) bindMount(source, target string, flags uintptr, eq bool) error {
+	return hostProc.bindMount(source, target, flags, eq)
+}
+func (direct) remount(target string, flags uintptr) error {
+	return hostProc.remount(target, flags)
+}
+func (direct) mountTmpfs(fsname, target string, flags uintptr, size int, perm os.FileMode) error {
+	return mountTmpfs(fsname, target, flags, size, perm)
+}
+func (direct) ensureFile(name string, perm, pperm os.FileMode) error {
+	return ensureFile(name, perm, pperm)
+}
+
+func (direct) seccompLoad(rules []seccomp.NativeRule, flags seccomp.ExportFlag) error {
+	return seccomp.Load(rules, flags)
+}
+func (direct) notify(c chan<- os.Signal, sig ...os.Signal) { signal.Notify(c, sig...) }
+func (direct) start(c *exec.Cmd) error                     { return c.Start() }
+func (direct) signal(c *exec.Cmd, sig os.Signal) error     { return c.Process.Signal(sig) }
+func (direct) evalSymlinks(path string) (string, error)    { return filepath.EvalSymlinks(path) }
+
+func (direct) exit(code int)                                 { os.Exit(code) }
+func (direct) getpid() int                                   { return os.Getpid() }
+func (direct) stat(name string) (os.FileInfo, error)         { return os.Stat(name) }
+func (direct) mkdir(name string, perm os.FileMode) error     { return os.Mkdir(name, perm) }
+func (direct) mkdirTemp(dir, pattern string) (string, error) { return os.MkdirTemp(dir, pattern) }
+func (direct) mkdirAll(path string, perm os.FileMode) error  { return os.MkdirAll(path, perm) }
+func (direct) readdir(name string) ([]os.DirEntry, error)    { return os.ReadDir(name) }
+func (direct) writeFile(name string, data []byte, perm os.FileMode) error {
+	return os.WriteFile(name, data, perm)
+}
+func (direct) createTemp(dir, pattern string) (osFile, error) {
+	return os.CreateTemp(dir, pattern)
+}
+func (direct) remove(name string) error {
+	return os.Remove(name)
+}
+func (direct) newFile(fd uintptr, name string) *os.File {
+	return os.NewFile(fd, name)
+}
+func (direct) symlink(oldname, newname string) error {
+	return os.Symlink(oldname, newname)
+}
+func (direct) readlink(name string) (string, error) {
+	return os.Readlink(name)
+}
+
+func (direct) umask(mask int) (oldmask int)     { return syscall.Umask(mask) }
+func (direct) sethostname(p []byte) (err error) { return syscall.Sethostname(p) }
+func (direct) chdir(path string) (err error)    { return syscall.Chdir(path) }
+func (direct) fchdir(fd int) (err error)        { return syscall.Fchdir(fd) }
+func (direct) open(path string, mode int, perm uint32) (fd int, err error) {
+	return syscall.Open(path, mode, perm)
+}
+func (direct) close(fd int) (err error) {
+	return syscall.Close(fd)
+}
+func (direct) pivotRoot(newroot, putold string) (err error) {
+	return syscall.PivotRoot(newroot, putold)
+}
+func (direct) mount(source, target, fstype string, flags uintptr, data string) (err error) {
+	return syscall.Mount(source, target, fstype, flags, data)
+}
+func (direct) unmount(target string, flags int) (err error) {
+	return syscall.Unmount(target, flags)
+}
+func (direct) wait4(pid int, wstatus *syscall.WaitStatus, options int, rusage *syscall.Rusage) (wpid int, err error) {
+	return syscall.Wait4(pid, wstatus, options, rusage)
+}
+
+func (direct) printf(format string, v ...any)          { log.Printf(format, v...) }
+func (direct) fatal(v ...any)                          { log.Fatal(v...) }
+func (direct) fatalf(format string, v ...any)          { log.Fatalf(format, v...) }
+func (direct) verbose(v ...any)                        { msg.Verbose(v...) }
+func (direct) verbosef(format string, v ...any)        { msg.Verbosef(format, v...) }
+func (direct) suspend()                                { msg.Suspend() }
+func (direct) resume() bool                            { return msg.Resume() }
+func (direct) beforeExit()                             { msg.BeforeExit() }
+func (direct) printBaseErr(err error, fallback string) { msg.PrintBaseErr(err, fallback) }