87 lines
2.8 KiB
Go
87 lines
2.8 KiB
Go
package main
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import (
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"os"
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"os/exec"
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"os/user"
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"path/filepath"
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"runtime"
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"strconv"
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"syscall"
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"github.com/jedisct1/dlog"
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)
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func (proxy *Proxy) dropPrivilege(userStr string, fds []*os.File) {
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currentUser, err := user.Current()
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if err != nil && currentUser.Uid != "0" {
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dlog.Fatal("Root privileges are required in order to switch to a different user. Maybe try again with 'sudo'")
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}
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userInfo, err := user.Lookup(userStr)
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args := os.Args
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if err != nil {
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uid, err2 := strconv.Atoi(userStr)
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if err2 != nil || uid <= 0 {
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dlog.Fatalf("Unable to retrieve any information about user [%s]: [%s] - Remove the user_name directive from the configuration file in order to avoid identity switch", userStr, err)
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}
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dlog.Warnf("Unable to retrieve any information about user [%s]: [%s] - Switching to user id [%v] with the same group id, as [%v] looks like a user id. But you should remove or fix the user_name directive in the configuration file if possible", userStr, err, uid, uid)
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userInfo = &user.User{Uid: userStr, Gid: userStr}
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}
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uid, err := strconv.Atoi(userInfo.Uid)
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if err != nil {
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dlog.Fatal(err)
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}
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gid, err := strconv.Atoi(userInfo.Gid)
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if err != nil {
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dlog.Fatal(err)
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}
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execPath, err := exec.LookPath(args[0])
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if err != nil {
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dlog.Fatalf("Unable to get the path to the dnscrypt-proxy executable file: [%s]", err)
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}
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path, err := filepath.Abs(execPath)
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if err != nil {
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dlog.Fatal(err)
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}
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ServiceManagerReadyNotify()
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args = append(args, "-child")
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dlog.Notice("Dropping privileges")
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runtime.LockOSThread()
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if _, _, rcode := syscall.RawSyscall(syscall.SYS_SETGROUPS, uintptr(0), uintptr(0), 0); rcode != 0 {
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dlog.Fatalf("Unable to drop additional groups: [%s]", rcode.Error())
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}
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if _, _, rcode := syscall.RawSyscall(syscall.SYS_SETGID, uintptr(gid), 0, 0); rcode != 0 {
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dlog.Fatalf("Unable to drop user privileges: [%s]", rcode.Error())
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}
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if _, _, rcode := syscall.RawSyscall(syscall.SYS_SETUID, uintptr(uid), 0, 0); rcode != 0 {
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dlog.Fatalf("Unable to drop user privileges: [%s]", rcode.Error())
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}
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maxfd := uintptr(0)
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for _, fd := range fds {
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if fd.Fd() > maxfd {
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maxfd = fd.Fd()
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}
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}
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fdbase := maxfd + 1
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for i, fd := range fds {
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if _, _, rcode := syscall.RawSyscall(syscall.SYS_DUP3, fd.Fd(), fdbase+uintptr(i), 0); rcode != 0 {
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dlog.Fatalf("Unable to clone file descriptor: [%s]", rcode.Error())
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}
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if _, _, rcode := syscall.RawSyscall(syscall.SYS_FCNTL, fd.Fd(), syscall.F_SETFD, syscall.FD_CLOEXEC); rcode != 0 {
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dlog.Fatalf("Unable to set the close on exec flag: [%s]", rcode.Error())
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}
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}
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for i := range fds {
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if _, _, rcode := syscall.RawSyscall(syscall.SYS_DUP3, fdbase+uintptr(i), uintptr(i)+3, 0); rcode != 0 {
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dlog.Fatalf("Unable to reassign descriptor: [%s]", rcode.Error())
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}
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}
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err = syscall.Exec(path, args, os.Environ())
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dlog.Fatalf("Unable to reexecute [%s]: [%s]", path, err)
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os.Exit(1)
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}
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