Script showing how db credentials in drushrc.php of an Aegir site can be updated.

update-drushrc-db-credentials.php

<?php


$password = 'blahblahblacksheep1';
$user = 'db_user';
$db_name = 'test';

$lines = file('drushrc.php');
foreach ($lines as $index => $line) {
    if (preg_match('/^\$options\[\'db_passwd\'\]\s*\=\s*\'.*?\'\s*\;/', $line)) {
        $lines[$index] = "\$options['db_passwd'] = '$password';\n";
    }
    elseif (preg_match('/^\$options\[\'db_name\'\]\s*\=\s*\'.*?\'\s*\;/', $line)) {
        $lines[$index] = "\$options['db_name'] = '$db_name';\n";
    }
    elseif (preg_match('/^\$options\[\'db_user\'\]\s*\=\s*\'.*?\'\s*\;/', $line)) {
        $lines[$index] = "\$options['db_user'] = '$user';\n";
    }
}

$new_file = file_put_contents('drushrc.php', implode('', $lines));