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
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/
