mirror of
https://github.com/criyle/go-sandbox.git
synced 2025-09-26 23:19:11 +08:00
140 lines
3.3 KiB
Go
140 lines
3.3 KiB
Go
package forkexec
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import (
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"syscall"
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"unsafe"
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"golang.org/x/sys/unix"
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)
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// Start will fork, load seccomp and execve and being traced by ptrace
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// Return pid and potential error
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// The runtime OS thread must be locked before calling this function
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// if ptrace is set to true
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func (r *Runner) Start() (int, error) {
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argv0, argv, env, err := prepareExec(r.Args, r.Env)
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if err != nil {
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return 0, err
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}
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// prepare work dir
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workdir, err := syscallStringFromString(r.WorkDir)
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if err != nil {
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return 0, err
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}
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// prepare sandbox profile
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profile, err := syscallStringFromString(r.SandboxProfile)
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if err != nil {
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return 0, err
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}
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// ensure the socketpair created did not leak to child
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syscall.ForkLock.Lock()
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// socketpair p is also used to sync with parent before final execve
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// p[0] is used by parent and p[1] is used by child
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var p [2]int
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if err := forkExecSocketPair(&p); err != nil {
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syscall.ForkLock.Unlock()
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return 0, err
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}
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// fork in child
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pid, err1 := forkAndExecInChild(r, argv0, argv, env, workdir, profile, p)
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// restore all signals
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afterFork()
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syscall.ForkLock.Unlock()
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return syncWithChild(r, p, int(pid), err1)
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}
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func forkExecSocketPair(p *[2]int) error {
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var err error
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*p, err = syscall.Socketpair(syscall.AF_LOCAL, syscall.SOCK_STREAM, 0)
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if err != nil {
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return err
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}
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_, err = fcntl(p[0], syscall.F_SETFD, syscall.FD_CLOEXEC)
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if err != nil {
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return err
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}
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_, err = fcntl(p[1], syscall.F_SETFD, syscall.FD_CLOEXEC)
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if err != nil {
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return err
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}
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return nil
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}
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func syncWithChild(r *Runner, p [2]int, pid int, err1 syscall.Errno) (int, error) {
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var (
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r1 uintptr
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err2 syscall.Errno
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err error
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)
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// sync with child
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unix.Close(p[1])
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// clone syscall failed
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if err1 != 0 {
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unix.Close(p[0])
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return 0, syscall.Errno(err1)
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}
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r1, _, err1 = syscall3(libc_read_trampoline_addr, uintptr(p[0]), uintptr(unsafe.Pointer(&err2)), uintptr(unsafe.Sizeof(err2)))
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// child returned error code
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if r1 != unsafe.Sizeof(err2) || err2 != 0 || err1 != 0 {
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err = handlePipeError(r1, err2)
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goto fail
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}
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// if syncfunc return error, then fail child immediately
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if r.SyncFunc != nil {
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if err = r.SyncFunc(int(pid)); err != nil {
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goto fail
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}
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}
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// otherwise, ack child (err1 == 0)
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r1, _, err1 = syscall3(libc_write_trampoline_addr, uintptr(p[0]), uintptr(unsafe.Pointer(&err1)), uintptr(unsafe.Sizeof(err1)))
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if err1 != 0 {
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goto fail
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}
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// if read anything mean child failed after sync (close_on_exec so it should not block)
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r1, _, err1 = syscall3(libc_read_trampoline_addr, uintptr(p[0]), uintptr(unsafe.Pointer(&err2)), uintptr(unsafe.Sizeof(err2)))
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unix.Close(p[0])
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if r1 != 0 || err1 != 0 {
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err = handlePipeError(r1, err2)
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goto failAfterClose
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}
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return int(pid), nil
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fail:
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unix.Close(p[0])
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failAfterClose:
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handleChildFailed(int(pid))
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return 0, err
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}
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// check pipe error
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func handlePipeError(r1 uintptr, errno syscall.Errno) error {
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if r1 == unsafe.Sizeof(errno) {
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return syscall.Errno(errno)
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}
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return syscall.EPIPE
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}
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func handleChildFailed(pid int) {
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var wstatus syscall.WaitStatus
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// make sure not blocked
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syscall.Kill(pid, syscall.SIGKILL)
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// child failed; wait for it to exit, to make sure the zombies don't accumulate
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_, err := syscall.Wait4(pid, &wstatus, 0, nil)
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for err == syscall.EINTR {
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_, err = syscall.Wait4(pid, &wstatus, 0, nil)
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}
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}
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