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之前使用preseed安装ubuntu luks全盘加密，这样每次重启系统都要通过vnc输入密码，可以将dropbear添加到initramfs，通过ssh解锁要方便很多。
安装dropbear-initramfs：

apt install dropbear-initramfs

安装时会提示：

dropbear: WARNING: Invalid authorized_keys file, remote unlocking of cryptroot via SSH won't work!

因为生成initramfs时要包含/etc/dropbear-initramfs/authorized_keys，复制ssh验证密钥：

#本地执行
ssh-copy-id  root@www.haiyun.me
#远程执行
cp -p ~/.ssh/authorized_keys /etc/dropbear-initramfs/

修改dropbear ssh端口：

echo 'DROPBEAR_OPTIONS="-p 2222"' >> /etc/dropbear-initramfs/config

配置initramfs ip：

#IP="${ip_address}::${gateway_ip}:${netmask}:${optional_fqdn}:${interface_name}:${auto_config}:${name_server}
echo 'IP=192.168.1.2::192.168.1.1:255.255.255.0::eth0:none:1.1.1.1' >> /etc/initramfs-tools/initramfs.conf

ip配置也可添加到grub启动参数：

GRUB_CMDLINE_LINUX="ip=192.168.1.2::192.168.1.1:255.255.255.0::eth0:none:1.1.1.1"

可选修改cryptroot-unlock解锁程序通过参数输入加密密码：

sed -i  '/^set/i if [ ! -n "\$1" ] ; then echo "use cryptroot-unlock password";exit;fi' /usr/share/cryptsetup/initramfs/bin/cryptroot-unlock
sed -i 's/read -rs/#read -rs/' /usr/share/cryptsetup/initramfs/bin/cryptroot-unlock
sed -i 's/\$REPLY/\$1/' /usr/share/cryptsetup/initramfs/bin/cryptroot-unlock

重新生成initramfs：

update-initramfs -u -k all

重启后通过ssh连接执行解锁luks：

cryptroot-unlock password

虽然/usr/share/initramfs-tools/scripts/init-bottom/dropbear有包含解锁luks后删除ip信息，但是启动后还是包含在initramfs内配置的ip信息，使用ubuntu在配置网络前清除ip信息：

sed -i '/iface eth0/a pre-up ip addr flush dev eth0' /etc/network/interfaces

20240325更新，debian12新版本ssh不能登录，提示：

debug1: Offering public key: /dev/shm/id_rsa RSA SHA256:xxxxx explicit                    
debug1: send_pubkey_test: no mutual signature algorithm                                                                         
debug1: No more authentication methods to try.  
root@www.haiyun.me: Permission denied (publickey).  

添加ssh配置：

cat .ssh/config 
Host *
    PubkeyAcceptedKeyTypes=+ssh-rsa
    HostKeyAlgorithms=+ssh-rsa

使用php调用expect ssh远程自动解锁luks：

<?php
ini_set("expect.timeout", 5);
ini_set("expect.loguser", "off");
$host = "www.haiyun.me";
$port = 22;
$pass = "xxxxxx";
$stream = expect_popen("ssh -o StrictHostKeyChecking=no -p {$port} root@{$host}");
$cases = array(
  array("password:", "pass"),
  array("Enter 'help'", "shell"),
  array("Please unlock disk", "unlock"),
  array("set up successfully", "sus"),
  array("Permission denied", "den"),
  array("cryptsetup failed", "fai")
);

while (true) {
  switch (expect_expectl($stream, $cases)) {
  case "den":
    echo 'Permission denied'.PHP_EOL;
    break 2;
  case "pass":
    fwrite($stream, "password\n");
    break;
  case "shell":
    fwrite($stream, "/usr/bin/cryptroot-unlock\n");
    //fwrite($stream, "/usr/bin/cryptroot-unlock {$pass}\n");
    break;
  case "unlock":
    fwrite($stream, "{$pass}\n");
    break;
  case "fai":
    echo 'unlock failed, bad password or options?'.PHP_EOL;
    break 2;
  case "sus":
    echo 'unlock sus'.PHP_EOL;
    break 2;
  case EXP_TIMEOUT:
    echo 'timeout'.PHP_EOL;
    break 2;
  case EXP_EOF:
    echo 'eof'.PHP_EOL;
    break 2; 
  default:
    die("Error has occurred!");
  }
}
fclose ($stream);

php调用ssh2扩展远程解锁luks加密：

<?php
$host = 'www.haiyun.me';
$port = 2222;
$pass = 'xxxx';
if (!($conn = ssh2_connect($host, $port, array('hostkey'=>'ssh-rsa')))) {
  die("conn fail\n");
}
//注意路径不要使用~/.ssh/id_rsa.pub，会遇到段错误和其它莫名其妙的问题
if (ssh2_auth_pubkey_file($conn, 'root', '/root/.ssh/id_rsa.pub', '/root/.ssh/id_rsa')) {
  echo "auth sus\n";
} else {
  die("auth fail\n");
}
function expect($stream, $match) {
  $time = time();
  $res = '';
  while(!feof($stream)){
    //if (($buffer = fgets($stream, 4096)) !== false) {
    if (($buffer = fread($stream, 4096)) !== false) {
      $res .= $buffer;
    }
    if (stristr($res, $match)) {
      return 'sus';
    }
    $now = time();
    if (($now - $time) >= 10) {
      return 'timeout';
    }
    usleep(100);
  }
  return 'disconnect';
}
 
$shell=ssh2_shell($conn, 'xterm');
fwrite($shell, "/usr/bin/cryptroot-unlock\n");
$res = expect($shell, 'Please unlock disk');
if ($res == 'sus') {
  fwrite($shell, "{$pass}\n");
  $res = expect($shell, 'set up successfully');
  if ($res == 'sus') {
  }
  var_dump($res);
}

发现的问题：此方法在ubuntu20.04使用编译的4.14内核bbrplus下导致系统启动很慢，5.4及5.10内核测试正常。
另外一种通过dracut生成initramfs调用openssh解锁luks的方法：
https://github.com/gsauthof/dracut-sshd
参考：
https://hamy.io/post/0009/how-to-install-luks-encrypted-ubuntu-18.04.x-server-and-enable-remote-unlocking/

标签：luks, 硬盘加密, 全盘加密, luks加密, ssh解锁luks