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out-of-tree/qemu/qemu-kernel.go

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// Copyright 2018 Mikhail Klementev. All rights reserved.
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// Use of this source code is governed by a AGPLv3 license
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// (or later) that can be found in the LICENSE file.
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package qemu
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import (
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"bytes"
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"errors"
"fmt"
"io"
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"math/rand"
"net"
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"os"
"os/exec"
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"runtime"
"strings"
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"syscall"
"time"
"golang.org/x/crypto/ssh"
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)
func readUntilEOF(pipe io.ReadCloser, buf *[]byte) (err error) {
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bufSize := 1024
for err != io.EOF {
stdout := make([]byte, bufSize)
var n int
n, err = pipe.Read(stdout)
if err != nil && err != io.EOF {
return
}
*buf = append(*buf, stdout[:n]...)
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}
if err == io.EOF {
err = nil
}
return
}
type arch string
const (
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// X86x64 is the qemu-system-x86_64
X86x64 arch = "x86_64"
// X86x32 is the qemu-system-i386
X86x32 = "i386"
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// TODO add other
unsupported = "unsupported" // for test purposes
)
// Kernel describe kernel parameters for qemu
type Kernel struct {
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Name string
KernelPath string
InitrdPath string
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}
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// System describe qemu parameters and executed process
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type System struct {
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arch arch
kernel Kernel
drivePath string
Cpus int
Memory int
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debug bool
gdb string // tcp::1234
noKASLR bool
noSMEP bool
noSMAP bool
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noKPTI bool
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// Timeout works after Start invocation
Timeout time.Duration
KilledByTimeout bool
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KernelPanic bool
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Died bool
sshAddrPort string
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// accessible while qemu is running
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cmd *exec.Cmd
pipe struct {
stdin io.WriteCloser
stderr io.ReadCloser
stdout io.ReadCloser
}
Stdout, Stderr []byte
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// accessible after qemu is closed
exitErr error
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}
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// NewSystem constructor
func NewSystem(arch arch, kernel Kernel, drivePath string) (q *System, err error) {
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if _, err = exec.LookPath("qemu-system-" + string(arch)); err != nil {
return
}
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q = &System{}
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q.arch = arch
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if _, err = os.Stat(kernel.KernelPath); err != nil {
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return
}
q.kernel = kernel
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if _, err = os.Stat(drivePath); err != nil {
return
}
q.drivePath = drivePath
// Default values
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q.Cpus = 1
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q.Memory = 512 // megabytes
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return
}
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func getRandomAddrPort() (addr string) {
// 127.1-255.0-255.0-255:10000-50000
ip := fmt.Sprintf("127.%d.%d.%d",
rand.Int()%254+1, rand.Int()%255, rand.Int()%254)
port := rand.Int()%40000 + 10000
return fmt.Sprintf("%s:%d", ip, port)
}
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func getRandomPort(ip string) (addr string) {
// ip:1024-65535
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port := rand.Int()%(65536-1024) + 1024
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return fmt.Sprintf("%s:%d", ip, port)
}
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func getFreeAddrPort() (addrPort string) {
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timeout := time.Now().Add(time.Second)
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for {
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if runtime.GOOS == "linux" {
addrPort = getRandomAddrPort()
} else {
addrPort = getRandomPort("127.0.0.1")
}
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ln, err := net.Listen("tcp", addrPort)
if err == nil {
ln.Close()
return
}
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if time.Now().After(timeout) {
panic("Can't found free address:port on localhost")
}
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}
}
func kvmExists() bool {
if _, err := os.Stat("/dev/kvm"); err != nil {
return false
}
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file, err := os.OpenFile("/dev/kvm", os.O_WRONLY, 0666)
if err != nil {
if os.IsPermission(err) {
return false
}
}
file.Close()
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return true
}
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func (q *System) panicWatcher() {
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for {
time.Sleep(time.Second)
if bytes.Contains(q.Stdout, []byte("Kernel panic")) {
time.Sleep(time.Second)
// There is no reason to stay alive after kernel panic
q.Stop()
q.KernelPanic = true
return
}
}
}
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func (q System) cmdline() (s string) {
s = "root=/dev/sda ignore_loglevel console=ttyS0 rw"
if q.noKASLR {
s += " nokaslr"
}
if q.noSMEP {
s += " nosmep"
}
if q.noSMAP {
s += " nosmap"
}
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if q.noKPTI {
s += " nokpti"
}
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return
}
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// Start qemu process
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func (q *System) Start() (err error) {
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rand.Seed(time.Now().UnixNano()) // Are you sure?
q.sshAddrPort = getFreeAddrPort()
hostfwd := fmt.Sprintf("hostfwd=tcp:%s-:22", q.sshAddrPort)
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qemuArgs := []string{"-snapshot", "-nographic",
"-hda", q.drivePath,
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"-kernel", q.kernel.KernelPath,
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"-smp", fmt.Sprintf("%d", q.Cpus),
"-m", fmt.Sprintf("%d", q.Memory),
"-device", "e1000,netdev=n1",
"-netdev", "user,id=n1," + hostfwd,
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}
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if q.debug {
qemuArgs = append(qemuArgs, "-gdb", q.gdb)
}
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if q.kernel.InitrdPath != "" {
qemuArgs = append(qemuArgs, "-initrd", q.kernel.InitrdPath)
}
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if (q.arch == X86x64 || q.arch == X86x32) && kvmExists() {
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qemuArgs = append(qemuArgs, "-enable-kvm", "-cpu", "host")
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}
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if q.arch == X86x64 && runtime.GOOS == "darwin" {
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qemuArgs = append(qemuArgs, "-accel", "hvf", "-cpu", "host")
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}
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qemuArgs = append(qemuArgs, "-append", q.cmdline())
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q.cmd = exec.Command("qemu-system-"+string(q.arch), qemuArgs...)
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if q.pipe.stdin, err = q.cmd.StdinPipe(); err != nil {
return
}
if q.pipe.stdout, err = q.cmd.StdoutPipe(); err != nil {
return
}
if q.pipe.stderr, err = q.cmd.StderrPipe(); err != nil {
return
}
err = q.cmd.Start()
if err != nil {
return
}
go readUntilEOF(q.pipe.stdout, &q.Stdout)
go readUntilEOF(q.pipe.stderr, &q.Stderr)
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go func() {
q.exitErr = q.cmd.Wait()
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q.Died = true
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}()
time.Sleep(time.Second / 10) // wait for immediately die
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if q.Died {
err = errors.New("qemu died immediately: " + string(q.Stderr))
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}
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go q.panicWatcher()
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if q.Timeout != 0 {
go func() {
time.Sleep(q.Timeout)
q.KilledByTimeout = true
q.Stop()
}()
}
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return
}
// Stop qemu process
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func (q *System) Stop() {
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// 1 00/01 01 01 SOH (Ctrl-A) START OF HEADING
fmt.Fprintf(q.pipe.stdin, "%cx", 1)
// wait for die
time.Sleep(time.Second / 10)
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if !q.Died {
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q.cmd.Process.Signal(syscall.SIGTERM)
time.Sleep(time.Second / 10)
q.cmd.Process.Signal(syscall.SIGKILL)
}
}
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func (q System) ssh(user string) (client *ssh.Client, err error) {
cfg := &ssh.ClientConfig{
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User: user,
HostKeyCallback: ssh.InsecureIgnoreHostKey(),
}
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client, err = ssh.Dial("tcp", q.sshAddrPort, cfg)
return
}
// Command executes shell commands on qemu system
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func (q System) Command(user, cmd string) (output string, err error) {
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client, err := q.ssh(user)
if err != nil {
return
}
defer client.Close()
session, err := client.NewSession()
if err != nil {
return
}
bytesOutput, err := session.CombinedOutput(cmd)
output = string(bytesOutput)
return
}
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// AsyncCommand executes command on qemu system but does not wait for exit
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func (q System) AsyncCommand(user, cmd string) (err error) {
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client, err := q.ssh(user)
if err != nil {
return
}
defer client.Close()
session, err := client.NewSession()
if err != nil {
return
}
return session.Run(fmt.Sprintf(
"nohup sh -c '%s' > /dev/null 2> /dev/null < /dev/null &", cmd))
}
// CopyFile is copy file from local machine to remote through ssh/scp
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func (q *System) CopyFile(user, localPath, remotePath string) (err error) {
addrPort := strings.Split(q.sshAddrPort, ":")
addr := addrPort[0]
port := addrPort[1]
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cmd := exec.Command("scp", "-P", port,
"-o", "StrictHostKeyChecking=no",
"-o", "LogLevel=error",
localPath, user+"@"+addr+":"+remotePath)
output, err := cmd.CombinedOutput()
if err != nil {
return errors.New(string(output))
}
return
}
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// CopyAndInsmod copy kernel module to temporary file on qemu then insmod it
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func (q *System) CopyAndInsmod(localKoPath string) (output string, err error) {
remoteKoPath := fmt.Sprintf("/tmp/module_%d.ko", rand.Int())
err = q.CopyFile("root", localKoPath, remoteKoPath)
if err != nil {
return
}
return q.Command("root", "insmod "+remoteKoPath)
}
// CopyAndRun is copy local file to qemu vm then run it
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func (q *System) CopyAndRun(user, path string) (output string, err error) {
remotePath := fmt.Sprintf("/tmp/executable_%d", rand.Int())
err = q.CopyFile(user, path, remotePath)
if err != nil {
return
}
return q.Command(user, "chmod +x "+remotePath+" && "+remotePath)
}
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// Debug is for enable qemu debug and set hostname and port for listen
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func (q *System) Debug(conn string) {
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q.debug = true
q.gdb = conn
}
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// SetKASLR is changing KASLR state through kernel boot args
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func (q *System) SetKASLR(state bool) {
q.noKASLR = !state
}
// SetSMEP is changing SMEP state through kernel boot args
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func (q *System) SetSMEP(state bool) {
q.noSMEP = !state
}
// SetSMAP is changing SMAP state through kernel boot args
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func (q *System) SetSMAP(state bool) {
q.noSMAP = !state
}
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// SetKPTI is changing KPTI state through kernel boot args
func (q *System) SetKPTI(state bool) {
q.noKPTI = !state
}
// GetKASLR is retrieve KASLR settings
func (q *System) GetKASLR() bool {
return !q.noKASLR
}
// GetSMEP is retrieve SMEP settings
func (q *System) GetSMEP() bool {
return !q.noSMEP
}
// GetSMAP is retrieve SMAP settings
func (q *System) GetSMAP() bool {
return !q.noSMAP
}
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// GetKPTI is retrieve KPTI settings
func (q *System) GetKPTI() bool {
return !q.noKPTI
}
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// GetSSHCommand returns command for connect to qemu machine over ssh
func (q System) GetSSHCommand() (cmd string) {
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addrPort := strings.Split(q.sshAddrPort, ":")
addr := addrPort[0]
port := addrPort[1]
cmd = "ssh -o StrictHostKeyChecking=no"
cmd += " -p " + port + " root@" + addr
return
}