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gobox.go
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package main
import (
"bufio"
"errors"
"flag"
"fmt"
"os"
"os/exec"
"strings"
"syscall"
"github.com/gobwas/glob"
)
type Request struct {
path string
syscall string
allowed bool
}
func requestPermission(path string) (Request, error) {
scanner := bufio.NewScanner(os.Stdin)
fmt.Println(fmt.Sprintf("Wanting to READ %s [y/n]", path))
for scanner.Scan() {
input := strings.ToLower(scanner.Text())
if input == "y" {
break
}
if scanner.Text() == "n" {
return Request{path, "READ", false}, nil
}
// Make a sounds
fmt.Printf("\a")
}
return Request{path, "READ", true}, nil
}
func Exec(bin string, args, allowedPatterns, blockedPatterns []string) (map[string]Request, error) {
var regs syscall.PtraceRegs
reqs := make(map[string]Request)
cmd := exec.Command(bin, args...)
cmd.Stderr = nil
cmd.Stdin = nil
cmd.Stdout = nil
cmd.SysProcAttr = &syscall.SysProcAttr{
Ptrace: true,
// TODO Pdeathsig a linux only
Pdeathsig: syscall.SIGKILL,
}
cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr
err := cmd.Start()
if err != nil {
return nil, fmt.Errorf("error while starting: %w", err)
}
_ = cmd.Wait()
pid := cmd.Process.Pid
for {
err := syscall.PtraceGetRegs(pid, ®s)
if err != nil {
break
}
// https://stackoverflow.com/questions/33431994/extracting-system-call-name-and-arguments-using-ptrace
if regs.Orig_rax == 0 {
// TODO this is a cross-x barrier
path, err := os.Readlink(fmt.Sprintf("/proc/%d/fd/%d", pid, regs.Rdi))
if err != nil {
return nil, err
}
for _, pattern := range allowedPatterns {
g := glob.MustCompile(pattern)
matched := g.Match(path)
if matched {
matchedReq := Request{path, "READ", true}
reqs[path] = matchedReq
}
}
for _, pattern := range blockedPatterns {
g := glob.MustCompile(pattern)
matched := g.Match(path)
if matched {
matchedReq := Request{path, "READ", false}
reqs[path] = matchedReq
}
}
req, ok := reqs[path]
if !ok {
req, err := requestPermission(path)
if err != nil {
return nil, err
}
reqs[req.path] = req
// Throw and exit the command
if !req.allowed {
return nil, errors.New(fmt.Sprintf("Blocked %s on %s", req.syscall, req.path))
}
} else {
// Throw and exit the command
if !req.allowed {
return nil, errors.New(fmt.Sprintf("Blocked %s on %s", req.syscall, req.path))
}
}
}
err = syscall.PtraceSyscall(pid, 0)
if err != nil {
return nil, err
}
_, err = syscall.Wait4(pid, nil, 0, nil)
if err != nil {
return nil, err
}
}
return reqs, nil
}
type arrayFlags []string
func (i *arrayFlags) String() string {
return ""
}
func (i *arrayFlags) Set(value string) error {
*i = append(*i, value)
return nil
}
func main() {
var allowedPattern arrayFlags
var blockedPattern arrayFlags
// TODO add sane defaults like libc etc
allowedPattern = append(allowedPattern, "")
flag.Var(&allowedPattern, "y", "A glob pattern for automatically allowing file reads.")
flag.Var(&blockedPattern, "n", "A glob pattern for automatically blocking file reads.")
help := flag.Bool("h", false, "Print Usage.")
flag.Parse()
if *help == true {
flag.Usage()
return
}
args := flag.Args()
_, err := Exec(args[0], args[1:], allowedPattern, blockedPattern)
if err != nil {
fmt.Println(err)
}
}