Properly format a string into a Private Key

setup_privkey.php

#!/usr/local/bin/php
<?php

// Does the environment variable exist?
if (!isset($_ENV['ID_RSA'])) {
    error_log("ID_RSA Environment Variable not set");
    return;
}

$id_rsa = $_ENV['ID_RSA'];
$file = '/root/.ssh/id_rsa';

// Create folder if does not exist
if (!file_exists(dirname($file))) {
    mkdir(dirname($file));
}

$header = '-----BEGIN RSA PRIVATE KEY-----';
$footer = '-----END RSA PRIVATE KEY-----';

$lines = str_split($id_rsa, 64);

$text = '';
$text .= $header.PHP_EOL;
array_walk($lines, function ($line) use (&$text) {
    $text .= $line.PHP_EOL;
});
$text .= $footer.PHP_EOL;

file_put_contents($file, $text);
chmod($file, 0600);

This particular script was written for turning a Bitbucket Pipeline environment variable (ID_RSA) into a Private Key file for ssh private key authentication deployments.

Since Pipeline environment variables do not allow newlines, this was necessary in order to create a private key file on a docker image without building it into the docker image