mirror of
https://github.com/autc04/Retro68.git
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630 lines
17 KiB
Go
630 lines
17 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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//go:build linux
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package syscall
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import (
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"internal/itoa"
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"unsafe"
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)
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//sysnb raw_prctl(option int, arg2 int, arg3 int, arg4 int, arg5 int) (ret int, err Errno)
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//prctl(option _C_int, arg2 _C_long, arg3 _C_long, arg4 _C_long, arg5 _C_long) _C_int
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//sysnb rawUnshare(flags int) (err Errno)
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//unshare(flags _C_int) _C_int
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//sysnb rawMount(source *byte, target *byte, fstype *byte, flags uintptr, data *byte) (err Errno)
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//mount(source *byte, target *byte, fstype *byte, flags _C_long, data *byte) _C_int
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//sysnb rawOpenat(dirfd int, pathname *byte, flags int, perm uint32) (fd int, err Errno)
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//__go_openat(dirfd _C_int, pathname *byte, flags _C_int, perm Mode_t) _C_int
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// SysProcIDMap holds Container ID to Host ID mappings used for User Namespaces in Linux.
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// See user_namespaces(7).
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type SysProcIDMap struct {
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ContainerID int // Container ID.
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HostID int // Host ID.
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Size int // Size.
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}
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type SysProcAttr struct {
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Chroot string // Chroot.
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Credential *Credential // Credential.
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// Ptrace tells the child to call ptrace(PTRACE_TRACEME).
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// Call runtime.LockOSThread before starting a process with this set,
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// and don't call UnlockOSThread until done with PtraceSyscall calls.
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Ptrace bool
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Setsid bool // Create session.
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// Setpgid sets the process group ID of the child to Pgid,
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// or, if Pgid == 0, to the new child's process ID.
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Setpgid bool
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// Setctty sets the controlling terminal of the child to
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// file descriptor Ctty. Ctty must be a descriptor number
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// in the child process: an index into ProcAttr.Files.
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// This is only meaningful if Setsid is true.
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Setctty bool
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Noctty bool // Detach fd 0 from controlling terminal
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Ctty int // Controlling TTY fd
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// Foreground places the child process group in the foreground.
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// This implies Setpgid. The Ctty field must be set to
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// the descriptor of the controlling TTY.
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// Unlike Setctty, in this case Ctty must be a descriptor
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// number in the parent process.
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Foreground bool
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Pgid int // Child's process group ID if Setpgid.
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Pdeathsig Signal // Signal that the process will get when its parent dies (Linux and FreeBSD only)
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Cloneflags uintptr // Flags for clone calls (Linux only)
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Unshareflags uintptr // Flags for unshare calls (Linux only)
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UidMappings []SysProcIDMap // User ID mappings for user namespaces.
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GidMappings []SysProcIDMap // Group ID mappings for user namespaces.
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// GidMappingsEnableSetgroups enabling setgroups syscall.
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// If false, then setgroups syscall will be disabled for the child process.
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// This parameter is no-op if GidMappings == nil. Otherwise for unprivileged
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// users this should be set to false for mappings work.
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GidMappingsEnableSetgroups bool
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AmbientCaps []uintptr // Ambient capabilities (Linux only)
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}
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var (
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none = [...]byte{'n', 'o', 'n', 'e', 0}
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slash = [...]byte{'/', 0}
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)
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// Implemented in runtime package.
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func runtime_BeforeFork()
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func runtime_AfterFork()
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func runtime_AfterForkInChild()
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// Implemented in clone_linux.c
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//go:noescape
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func rawClone(flags _C_ulong, child_stack *byte, ptid *Pid_t, ctid *Pid_t, regs unsafe.Pointer) _C_long
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// Fork, dup fd onto 0..len(fd), and exec(argv0, argvv, envv) in child.
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// If a dup or exec fails, write the errno error to pipe.
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// (Pipe is close-on-exec so if exec succeeds, it will be closed.)
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// In the child, this function must not acquire any locks, because
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// they might have been locked at the time of the fork. This means
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// no rescheduling, no malloc calls, and no new stack segments.
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// For the same reason compiler does not race instrument it.
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// The calls to RawSyscall are okay because they are assembly
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// functions that do not grow the stack.
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//go:norace
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func forkAndExecInChild(argv0 *byte, argv, envv []*byte, chroot, dir *byte, attr *ProcAttr, sys *SysProcAttr, pipe int) (pid int, err Errno) {
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// Set up and fork. This returns immediately in the parent or
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// if there's an error.
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r1, err1, p, locked := forkAndExecInChild1(argv0, argv, envv, chroot, dir, attr, sys, pipe)
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if locked {
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runtime_AfterFork()
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}
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if err1 != 0 {
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return 0, err1
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}
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// parent; return PID
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pid = int(r1)
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if sys.UidMappings != nil || sys.GidMappings != nil {
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Close(p[0])
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var err2 Errno
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// uid/gid mappings will be written after fork and unshare(2) for user
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// namespaces.
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if sys.Unshareflags&CLONE_NEWUSER == 0 {
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if err := writeUidGidMappings(pid, sys); err != nil {
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err2 = err.(Errno)
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}
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}
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raw_write(p[1], (*byte)(unsafe.Pointer(&err2)), int(unsafe.Sizeof(err2)))
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Close(p[1])
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}
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return pid, 0
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}
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const _LINUX_CAPABILITY_VERSION_3 = 0x20080522
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type capHeader struct {
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version uint32
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pid int32
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}
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type capData struct {
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effective uint32
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permitted uint32
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inheritable uint32
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}
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type caps struct {
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hdr capHeader
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data [2]capData
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}
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// See CAP_TO_INDEX in linux/capability.h:
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func capToIndex(cap uintptr) uintptr { return cap >> 5 }
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// See CAP_TO_MASK in linux/capability.h:
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func capToMask(cap uintptr) uint32 { return 1 << uint(cap&31) }
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// forkAndExecInChild1 implements the body of forkAndExecInChild up to
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// the parent's post-fork path. This is a separate function so we can
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// separate the child's and parent's stack frames if we're using
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// vfork.
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//
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// This is go:noinline because the point is to keep the stack frames
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// of this and forkAndExecInChild separate.
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//
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//go:noinline
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//go:norace
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func forkAndExecInChild1(argv0 *byte, argv, envv []*byte, chroot, dir *byte, attr *ProcAttr, sys *SysProcAttr, pipe int) (r1 uintptr, err1 Errno, p [2]int, locked bool) {
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// Defined in linux/prctl.h starting with Linux 4.3.
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const (
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PR_CAP_AMBIENT = 0x2f
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PR_CAP_AMBIENT_RAISE = 0x2
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)
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// vfork requires that the child not touch any of the parent's
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// active stack frames. Hence, the child does all post-fork
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// processing in this stack frame and never returns, while the
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// parent returns immediately from this frame and does all
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// post-fork processing in the outer frame.
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// Declare all variables at top in case any
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// declarations require heap allocation (e.g., err1).
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var (
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err2 Errno
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nextfd int
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i int
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r2 int
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caps caps
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fd1 int
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puid, psetgroups, pgid []byte
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uidmap, setgroups, gidmap []byte
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)
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if sys.UidMappings != nil {
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puid = []byte("/proc/self/uid_map\000")
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uidmap = formatIDMappings(sys.UidMappings)
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}
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if sys.GidMappings != nil {
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psetgroups = []byte("/proc/self/setgroups\000")
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pgid = []byte("/proc/self/gid_map\000")
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if sys.GidMappingsEnableSetgroups {
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setgroups = []byte("allow\000")
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} else {
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setgroups = []byte("deny\000")
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}
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gidmap = formatIDMappings(sys.GidMappings)
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}
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// Record parent PID so child can test if it has died.
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ppid := raw_getpid()
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// Guard against side effects of shuffling fds below.
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// Make sure that nextfd is beyond any currently open files so
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// that we can't run the risk of overwriting any of them.
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fd := make([]int, len(attr.Files))
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nextfd = len(attr.Files)
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for i, ufd := range attr.Files {
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if nextfd < int(ufd) {
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nextfd = int(ufd)
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}
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fd[i] = int(ufd)
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}
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nextfd++
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// Allocate another pipe for parent to child communication for
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// synchronizing writing of User ID/Group ID mappings.
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if sys.UidMappings != nil || sys.GidMappings != nil {
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if err := forkExecPipe(p[:]); err != nil {
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err1 = err.(Errno)
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return
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}
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}
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// About to call fork.
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// No more allocation or calls of non-assembly functions.
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runtime_BeforeFork()
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locked = true
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r2 = int(rawClone(_C_ulong(uintptr(SIGCHLD)|sys.Cloneflags), nil, nil, nil, unsafe.Pointer(nil)))
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if r2 < 0 {
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err1 = GetErrno()
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}
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if r2 != 0 {
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// If we're in the parent, we must return immediately
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// so we're not in the same stack frame as the child.
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// This can at most use the return PC, which the child
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// will not modify, and the results of
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// rawVforkSyscall, which must have been written after
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// the child was replaced.
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r1 = uintptr(r2)
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return
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}
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// Fork succeeded, now in child.
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// Enable the "keep capabilities" flag to set ambient capabilities later.
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if len(sys.AmbientCaps) > 0 {
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_, err1 = raw_prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0)
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if err1 != 0 {
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goto childerror
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}
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}
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// Wait for User ID/Group ID mappings to be written.
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if sys.UidMappings != nil || sys.GidMappings != nil {
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if err1 = raw_close(p[1]); err1 != 0 {
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goto childerror
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}
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r2, err1 = raw_read(p[0], (*byte)(unsafe.Pointer(&err2)), int(unsafe.Sizeof(err2)))
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if err1 != 0 {
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goto childerror
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}
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if r2 != int(unsafe.Sizeof(err2)) {
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err1 = EINVAL
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goto childerror
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}
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if err2 != 0 {
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err1 = err2
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goto childerror
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}
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}
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// Session ID
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if sys.Setsid {
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err1 = raw_setsid()
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if err1 != 0 {
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goto childerror
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}
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}
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// Set process group
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if sys.Setpgid || sys.Foreground {
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// Place child in process group.
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err1 = raw_setpgid(0, sys.Pgid)
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if err1 != 0 {
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goto childerror
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}
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}
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if sys.Foreground {
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pgrp := Pid_t(sys.Pgid)
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if pgrp == 0 {
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pgrp = raw_getpid()
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}
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// Place process group in foreground.
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_, err1 = raw_ioctl_ptr(sys.Ctty, TIOCSPGRP, unsafe.Pointer(&pgrp))
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if err1 != 0 {
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goto childerror
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}
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}
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// Restore the signal mask. We do this after TIOCSPGRP to avoid
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// having the kernel send a SIGTTOU signal to the process group.
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runtime_AfterForkInChild()
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// Unshare
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if sys.Unshareflags != 0 {
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err1 = rawUnshare(int(sys.Unshareflags))
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if err1 != 0 {
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goto childerror
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}
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if sys.Unshareflags&CLONE_NEWUSER != 0 && sys.GidMappings != nil {
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dirfd := int(_AT_FDCWD)
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if fd1, err1 = rawOpenat(dirfd, &psetgroups[0], O_WRONLY, 0); err1 != 0 {
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goto childerror
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}
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_, err1 = raw_write(fd1, &setgroups[0], len(setgroups))
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if err1 != 0 {
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goto childerror
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}
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if err1 = raw_close(fd1); err1 != 0 {
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goto childerror
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}
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if fd1, err1 = rawOpenat(dirfd, &pgid[0], O_WRONLY, 0); err1 != 0 {
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goto childerror
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}
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_, err1 = raw_write(fd1, &gidmap[0], len(gidmap))
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if err1 != 0 {
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goto childerror
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}
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if err1 = raw_close(fd1); err1 != 0 {
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goto childerror
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}
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}
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if sys.Unshareflags&CLONE_NEWUSER != 0 && sys.UidMappings != nil {
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dirfd := int(_AT_FDCWD)
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if fd1, err1 = rawOpenat(dirfd, &puid[0], O_WRONLY, 0); err1 != 0 {
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goto childerror
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}
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_, err1 = raw_write(fd1, &uidmap[0], len(uidmap))
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if err1 != 0 {
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goto childerror
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}
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if err1 = raw_close(fd1); err1 != 0 {
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goto childerror
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}
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}
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// The unshare system call in Linux doesn't unshare mount points
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// mounted with --shared. Systemd mounts / with --shared. For a
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// long discussion of the pros and cons of this see debian bug 739593.
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// The Go model of unsharing is more like Plan 9, where you ask
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// to unshare and the namespaces are unconditionally unshared.
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// To make this model work we must further mark / as MS_PRIVATE.
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// This is what the standard unshare command does.
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if sys.Unshareflags&CLONE_NEWNS == CLONE_NEWNS {
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err1 = rawMount(&none[0], &slash[0], nil, MS_REC|MS_PRIVATE, nil)
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if err1 != 0 {
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goto childerror
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}
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}
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}
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// Chroot
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if chroot != nil {
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err1 = raw_chroot(chroot)
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if err1 != 0 {
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goto childerror
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}
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}
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// User and groups
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if cred := sys.Credential; cred != nil {
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ngroups := len(cred.Groups)
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var groups unsafe.Pointer
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if ngroups > 0 {
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groups = unsafe.Pointer(&cred.Groups[0])
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}
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if !(sys.GidMappings != nil && !sys.GidMappingsEnableSetgroups && ngroups == 0) && !cred.NoSetGroups {
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err1 = raw_setgroups(ngroups, groups)
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if err1 != 0 {
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goto childerror
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}
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}
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_, _, err1 = RawSyscall(sys_SETGID, uintptr(cred.Gid), 0, 0)
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if err1 != 0 {
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goto childerror
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}
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_, _, err1 = RawSyscall(sys_SETUID, uintptr(cred.Uid), 0, 0)
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if err1 != 0 {
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goto childerror
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}
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}
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if len(sys.AmbientCaps) != 0 {
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// Ambient capabilities were added in the 4.3 kernel,
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// so it is safe to always use _LINUX_CAPABILITY_VERSION_3.
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caps.hdr.version = _LINUX_CAPABILITY_VERSION_3
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if _, _, err1 = RawSyscall(SYS_CAPGET, uintptr(unsafe.Pointer(&caps.hdr)), uintptr(unsafe.Pointer(&caps.data[0])), 0); err1 != 0 {
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goto childerror
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}
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for _, c := range sys.AmbientCaps {
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// Add the c capability to the permitted and inheritable capability mask,
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// otherwise we will not be able to add it to the ambient capability mask.
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caps.data[capToIndex(c)].permitted |= capToMask(c)
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caps.data[capToIndex(c)].inheritable |= capToMask(c)
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}
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if _, _, err1 = RawSyscall(SYS_CAPSET, uintptr(unsafe.Pointer(&caps.hdr)), uintptr(unsafe.Pointer(&caps.data[0])), 0); err1 != 0 {
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goto childerror
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}
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for _, c := range sys.AmbientCaps {
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_, _, err1 = RawSyscall6(SYS_PRCTL, PR_CAP_AMBIENT, uintptr(PR_CAP_AMBIENT_RAISE), c, 0, 0, 0)
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if err1 != 0 {
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goto childerror
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}
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}
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}
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// Chdir
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if dir != nil {
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err1 = raw_chdir(dir)
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if err1 != 0 {
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goto childerror
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}
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}
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// Parent death signal
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if sys.Pdeathsig != 0 {
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_, err1 = raw_prctl(PR_SET_PDEATHSIG, int(sys.Pdeathsig), 0, 0, 0)
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if err1 != 0 {
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goto childerror
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}
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// Signal self if parent is already dead. This might cause a
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// duplicate signal in rare cases, but it won't matter when
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// using SIGKILL.
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r1 := raw_getppid()
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if r1 != ppid {
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pid := raw_getpid()
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err1 = raw_kill(pid, sys.Pdeathsig)
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if err1 != 0 {
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goto childerror
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}
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}
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}
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// Pass 1: look for fd[i] < i and move those up above len(fd)
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// so that pass 2 won't stomp on an fd it needs later.
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if pipe < nextfd {
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err1 = raw_dup3(pipe, nextfd, O_CLOEXEC)
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if err1 != 0 {
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goto childerror
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}
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pipe = nextfd
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nextfd++
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}
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for i = 0; i < len(fd); i++ {
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if fd[i] >= 0 && fd[i] < int(i) {
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if nextfd == pipe { // don't stomp on pipe
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nextfd++
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}
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err1 = raw_dup3(fd[i], nextfd, O_CLOEXEC)
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if err1 != 0 {
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goto childerror
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}
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fd[i] = nextfd
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nextfd++
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}
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}
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|
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// Pass 2: dup fd[i] down onto i.
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for i = 0; i < len(fd); i++ {
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if fd[i] == -1 {
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raw_close(i)
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continue
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}
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if fd[i] == int(i) {
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// dup2(i, i) won't clear close-on-exec flag on Linux,
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// probably not elsewhere either.
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_, err1 = raw_fcntl(fd[i], F_SETFD, 0)
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if err1 != 0 {
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goto childerror
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}
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continue
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}
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// The new fd is created NOT close-on-exec,
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|
// which is exactly what we want.
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|
err1 = raw_dup3(fd[i], i, 0)
|
|
if err1 != 0 {
|
|
goto childerror
|
|
}
|
|
}
|
|
|
|
// By convention, we don't close-on-exec the fds we are
|
|
// started with, so if len(fd) < 3, close 0, 1, 2 as needed.
|
|
// Programs that know they inherit fds >= 3 will need
|
|
// to set them close-on-exec.
|
|
for i = len(fd); i < 3; i++ {
|
|
raw_close(i)
|
|
}
|
|
|
|
// Detach fd 0 from tty
|
|
if sys.Noctty {
|
|
_, err1 = raw_ioctl(0, TIOCNOTTY, 0)
|
|
if err1 != 0 {
|
|
goto childerror
|
|
}
|
|
}
|
|
|
|
// Set the controlling TTY to Ctty
|
|
if sys.Setctty {
|
|
_, err1 = raw_ioctl(sys.Ctty, TIOCSCTTY, 1)
|
|
if err1 != 0 {
|
|
goto childerror
|
|
}
|
|
}
|
|
|
|
// Enable tracing if requested.
|
|
// Do this right before exec so that we don't unnecessarily trace the runtime
|
|
// setting up after the fork. See issue #21428.
|
|
if sys.Ptrace {
|
|
err1 = raw_ptrace(_PTRACE_TRACEME, 0, 0, 0)
|
|
if err1 != 0 {
|
|
goto childerror
|
|
}
|
|
}
|
|
|
|
// Time to exec.
|
|
err1 = raw_execve(argv0, &argv[0], &envv[0])
|
|
|
|
childerror:
|
|
// send error code on pipe
|
|
raw_write(pipe, (*byte)(unsafe.Pointer(&err1)), int(unsafe.Sizeof(err1)))
|
|
for {
|
|
raw_exit(253)
|
|
}
|
|
}
|
|
|
|
// Try to open a pipe with O_CLOEXEC set on both file descriptors.
|
|
func forkExecPipe(p []int) (err error) {
|
|
return Pipe2(p, O_CLOEXEC)
|
|
}
|
|
|
|
func formatIDMappings(idMap []SysProcIDMap) []byte {
|
|
var data []byte
|
|
for _, im := range idMap {
|
|
data = append(data, []byte(itoa.Itoa(im.ContainerID)+" "+itoa.Itoa(im.HostID)+" "+itoa.Itoa(im.Size)+"\n")...)
|
|
}
|
|
return data
|
|
}
|
|
|
|
// writeIDMappings writes the user namespace User ID or Group ID mappings to the specified path.
|
|
func writeIDMappings(path string, idMap []SysProcIDMap) error {
|
|
fd, err := Open(path, O_RDWR, 0)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
|
|
if _, err := Write(fd, formatIDMappings(idMap)); err != nil {
|
|
Close(fd)
|
|
return err
|
|
}
|
|
|
|
if err := Close(fd); err != nil {
|
|
return err
|
|
}
|
|
|
|
return nil
|
|
}
|
|
|
|
// writeSetgroups writes to /proc/PID/setgroups "deny" if enable is false
|
|
// and "allow" if enable is true.
|
|
// This is needed since kernel 3.19, because you can't write gid_map without
|
|
// disabling setgroups() system call.
|
|
func writeSetgroups(pid int, enable bool) error {
|
|
sgf := "/proc/" + itoa.Itoa(pid) + "/setgroups"
|
|
fd, err := Open(sgf, O_RDWR, 0)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
|
|
var data []byte
|
|
if enable {
|
|
data = []byte("allow")
|
|
} else {
|
|
data = []byte("deny")
|
|
}
|
|
|
|
if _, err := Write(fd, data); err != nil {
|
|
Close(fd)
|
|
return err
|
|
}
|
|
|
|
return Close(fd)
|
|
}
|
|
|
|
// writeUidGidMappings writes User ID and Group ID mappings for user namespaces
|
|
// for a process and it is called from the parent process.
|
|
func writeUidGidMappings(pid int, sys *SysProcAttr) error {
|
|
if sys.UidMappings != nil {
|
|
uidf := "/proc/" + itoa.Itoa(pid) + "/uid_map"
|
|
if err := writeIDMappings(uidf, sys.UidMappings); err != nil {
|
|
return err
|
|
}
|
|
}
|
|
|
|
if sys.GidMappings != nil {
|
|
// If the kernel is too old to support /proc/PID/setgroups, writeSetGroups will return ENOENT; this is OK.
|
|
if err := writeSetgroups(pid, sys.GidMappingsEnableSetgroups); err != nil && err != ENOENT {
|
|
return err
|
|
}
|
|
gidf := "/proc/" + itoa.Itoa(pid) + "/gid_map"
|
|
if err := writeIDMappings(gidf, sys.GidMappings); err != nil {
|
|
return err
|
|
}
|
|
}
|
|
|
|
return nil
|
|
}
|