docs: add security hardening implementation plan

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2026-04-20 09:44:48 +02:00
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# Security Hardening & Bug Fixes Implementation Plan
> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development (recommended) or superpowers:executing-plans to implement this plan task-by-task. Steps use checkbox (`- [ ]`) syntax for tracking.
**Goal:** Harden http2pic with optional API key auth, opt-in SSRF protection, viewport cap, and fix two correctness bugs (60ms timeout, viewport set after page load).
**Architecture:** All PHP changes stay in `web/index.php` and `src/helpers.php`. Config vars flow from `docker-compose.yml` env → `docker/start.sh``src/config.inc.php` defines. No new dependencies.
**Tech Stack:** PHP 8.4, php-webdriver, Caddy, Docker
---
## File Map
| File | What changes |
|------|-------------|
| `tests/test_helpers.php` | New — unit tests for `isPrivateIP()` and `getUserIP()` |
| `src/helpers.php` | Add `isPrivateIP()`, fix `getUserIP()`, fix `addToLog()` log injection |
| `docker/start.sh` | Write `API_KEY` and `BLOCK_PRIVATE_IPS` defines into config |
| `docker-compose.yml` | Add commented env var examples |
| `web/index.php` | API key check, SSRF check, viewport cap, viewport-before-get, timeout fix, generic errors |
---
## Task 1: Write failing tests for helpers
**Files:**
- Create: `tests/test_helpers.php`
- [ ] **Step 1: Create test file**
```php
<?php
define('DS', DIRECTORY_SEPARATOR);
define('ROOT', dirname(__FILE__) . '/..');
require_once ROOT . '/src/helpers.php';
$passed = 0;
$failed = 0;
function check(bool $condition, string $label): void {
global $passed, $failed;
if ($condition) { echo "PASS: $label\n"; $passed++; }
else { echo "FAIL: $label\n"; $failed++; }
}
// --- isPrivateIP ---
check(isPrivateIP('127.0.0.1'), 'loopback 127.0.0.1');
check(isPrivateIP('127.255.255.255'), 'loopback 127.255.255.255');
check(isPrivateIP('10.0.0.1'), '10.x private');
check(isPrivateIP('10.255.255.255'), '10.255.x private');
check(isPrivateIP('172.16.0.1'), '172.16.x private');
check(isPrivateIP('172.31.255.255'), '172.31.x private');
check(!isPrivateIP('172.15.255.255'), '172.15.x is public');
check(!isPrivateIP('172.32.0.0'), '172.32.x is public');
check(isPrivateIP('192.168.0.1'), '192.168.x private');
check(isPrivateIP('169.254.169.254'), 'AWS metadata IP');
check(!isPrivateIP('8.8.8.8'), 'Google DNS is public');
check(!isPrivateIP('93.184.216.34'), 'example.com IP is public');
check(isPrivateIP('not-an-ip'), 'unparseable IP blocked');
// --- getUserIP ---
unset($_SERVER['HTTP_X_FORWARDED_FOR']);
$_SERVER['REMOTE_ADDR'] = '5.6.7.8';
check(getUserIP() === '5.6.7.8', 'getUserIP falls back to REMOTE_ADDR');
$_SERVER['HTTP_X_FORWARDED_FOR'] = '1.2.3.4, 10.0.0.1, 172.16.0.5';
check(getUserIP() === '1.2.3.4', 'getUserIP takes first X-Forwarded-For IP');
$_SERVER['HTTP_X_FORWARDED_FOR'] = ' 9.9.9.9 ';
check(getUserIP() === '9.9.9.9', 'getUserIP trims whitespace');
echo "\n$passed passed, $failed failed\n";
exit($failed > 0 ? 1 : 0);
```
- [ ] **Step 2: Run tests — expect failures**
```bash
php tests/test_helpers.php
```
Expected: several `FAIL:` lines (functions don't exist yet or have wrong logic). PHP fatal error on `isPrivateIP` is fine.
---
## Task 2: Implement helpers changes
**Files:**
- Modify: `src/helpers.php`
- [ ] **Step 1: Replace `getUserIP()` and fix `addToLog()`, add `isPrivateIP()`**
Replace the entire contents of `src/helpers.php` with:
```php
<?php
function renderTemplate($templatename, $variables = [], $basepath = ROOT . '/src')
{
ob_start();
if (is_array($variables))
extract($variables);
if (file_exists($basepath . DS . 'templates' . DS . $templatename . '.php'))
include($basepath . DS . 'templates' . DS . $templatename . '.php');
else if (file_exists($basepath . DS . 'templates' . DS . $templatename))
include($basepath . DS . 'templates' . DS . $templatename);
$rendered = ob_get_contents();
ob_end_clean();
return $rendered;
}
function addToLog(string $data): void
{
$data = str_replace(["\n", "\r", "\t"], ' ', $data);
$fp = fopen(ROOT . DS . 'logs' . DS . 'app.log', 'a');
fwrite($fp, date("d.m.y H:i") . "\t" . $data . "\n");
fclose($fp);
}
function getUserIP(): string
{
if (!empty($_SERVER['HTTP_X_FORWARDED_FOR']))
return trim(explode(',', $_SERVER['HTTP_X_FORWARDED_FOR'])[0]);
return $_SERVER['REMOTE_ADDR'];
}
function isPrivateIP(string $ip): bool
{
if (filter_var($ip, FILTER_VALIDATE_IP) === false) return true;
$long = ip2long($ip);
if ($long === false) return true;
foreach ([
[ip2long('127.0.0.0'), 0xFF000000], // 127.0.0.0/8 loopback
[ip2long('10.0.0.0'), 0xFF000000], // 10.0.0.0/8 RFC1918
[ip2long('172.16.0.0'), 0xFFF00000], // 172.16.0.0/12 RFC1918
[ip2long('192.168.0.0'), 0xFFFF0000], // 192.168.0.0/16 RFC1918
[ip2long('169.254.0.0'), 0xFFFF0000], // 169.254.0.0/16 link-local/metadata
] as [$base, $mask]) {
if (($long & $mask) === ($base & $mask)) return true;
}
return false;
}
```
- [ ] **Step 2: Run tests — expect all pass**
```bash
php tests/test_helpers.php
```
Expected output ends with: `N passed, 0 failed`
- [ ] **Step 3: Commit**
```bash
git add src/helpers.php tests/test_helpers.php
git commit -m "feat: add isPrivateIP helper, fix getUserIP and addToLog"
```
---
## Task 3: Update config generation
**Files:**
- Modify: `docker/start.sh`
- Modify: `docker-compose.yml`
- [ ] **Step 1: Update `_buildConfig` in `docker/start.sh`**
Replace the `_buildConfig` function:
```bash
_buildConfig() {
echo "<?php"
echo "date_default_timezone_set('Europe/Vienna');"
echo "define('URL','${URL:-http://localhost:8080}');"
echo "define('API_KEY','${API_KEY:-}');"
echo "define('BLOCK_PRIVATE_IPS',${BLOCK_PRIVATE_IPS:-false});"
echo ""
}
```
- [ ] **Step 2: Add commented env var examples to `docker-compose.yml`**
Replace the `environment:` block:
```yaml
environment:
- URL=http://localhost:8080
# - API_KEY=your-secret-key # if set, all /api requests must provide it
# - BLOCK_PRIVATE_IPS=true # block LAN/loopback/metadata IPs (recommended for public hosting)
```
- [ ] **Step 3: Verify config generation manually**
```bash
URL=http://localhost:8080 API_KEY=test BLOCK_PRIVATE_IPS=true bash -c '
_buildConfig() {
echo "<?php"
echo "date_default_timezone_set('"'"'Europe/Vienna'"'"');"
echo "define('"'"'URL'"'"','"'"'${URL:-http://localhost:8080}'"'"');"
echo "define('"'"'API_KEY'"'"','"'"'${API_KEY:-}'"'"');"
echo "define('"'"'BLOCK_PRIVATE_IPS'"'"',${BLOCK_PRIVATE_IPS:-false});"
echo ""
}
_buildConfig'
```
Expected output:
```
<?php
date_default_timezone_set('Europe/Vienna');
define('URL','http://localhost:8080');
define('API_KEY','test');
define('BLOCK_PRIVATE_IPS',true);
```
- [ ] **Step 4: Commit**
```bash
git add docker/start.sh docker-compose.yml
git commit -m "feat: add API_KEY and BLOCK_PRIVATE_IPS config vars"
```
---
## Task 4: Fix index.php bugs + viewport cap + generic errors
**Files:**
- Modify: `web/index.php`
This task rewrites the `case 'api':` block. Read the current state of `web/index.php` first, then replace the entire `case 'api':` block (from `case 'api':` through `break;`) with the following.
- [ ] **Step 1: Replace `case 'api':` block**
```php
case 'api':
$target = substr($_SERVER['REQUEST_URI'], 5);
if (!$target || !filter_var($target, FILTER_VALIDATE_URL))
$target = $_REQUEST['url'];
if (!filter_var($target, FILTER_VALIDATE_URL)) {
header('HTTP/1.0 400 Bad Request');
echo 'Invalid URL';
exit;
}
$ip = getUserIP();
$viewport = $_REQUEST['viewport'] ?: '1024x768';
if (!preg_match('/^\d+x\d+$/', $viewport)) {
header('HTTP/1.0 400 Bad Request');
echo 'Invalid viewport format. Use WIDTHxHEIGHT (e.g., 1024x768)';
exit;
}
$vpParts = array_map('intval', explode('x', $viewport));
if ($vpParts[0] > 3840 || $vpParts[1] > 2160) {
header('HTTP/1.0 400 Bad Request');
echo 'Viewport exceeds maximum (3840x2160)';
exit;
}
$js = $_REQUEST['js'] == 'false' ? false : true;
$serverUrl = 'http://localhost:4444';
$options = new \Facebook\WebDriver\Chrome\ChromeOptions();
$options->addArguments(['--headless', '--disable-gpu', '--no-sandbox', '--disable-dev-shm-usage']);
$capabilities = DesiredCapabilities::chrome();
$capabilities->setCapability(\Facebook\WebDriver\Chrome\ChromeOptions::CAPABILITY, $options);
if (!$js)
$capabilities->setCapability('javascriptEnabled', false);
$driver = null;
$error = null;
try {
$driver = RemoteWebDriver::create($serverUrl, $capabilities, 30000, 60000);
$driver->manage()->window()->setSize(new \Facebook\WebDriver\WebDriverDimension($vpParts[0], $vpParts[1]));
$driver->get($target);
$driver->executeScript('document.body.style.overflow = "hidden";');
addToLog("$ip\tRequested $target with viewport $viewport and js " . ($js ? 'enabled' : 'disabled'));
$screenshot = $driver->takeScreenshot();
header('Content-Type: image/png');
header('Content-Length: ' . strlen($screenshot));
echo $screenshot;
} catch (Exception $e) {
$error = $e->getMessage();
addToLog("$ip\tRequested $target but resulted in error:\t" . $error);
} finally {
if ($driver instanceof RemoteWebDriver) {
try { $driver->quit(); } catch (Exception $q) {}
}
}
if ($error !== null) {
header('HTTP/1.0 500 Internal Server Error');
echo 'Screenshot failed';
}
break;
```
- [ ] **Step 2: Test viewport cap with curl**
```bash
curl -s -o /dev/null -w "%{http_code}" "http://localhost:8080/api?url=https://example.com&viewport=99999x99999"
```
Expected: `400`
```bash
curl -s -o /dev/null -w "%{http_code}" "http://localhost:8080/api?url=https://example.com&viewport=1024x768"
```
Expected: `200`
- [ ] **Step 3: Commit**
```bash
git add web/index.php
git commit -m "fix: viewport before page load, 60ms→60s timeout, viewport cap, generic errors"
```
---
## Task 5: Add API key authentication
**Files:**
- Modify: `web/index.php`
- [ ] **Step 1: Add API key check at top of `case 'api':` block**
Insert immediately after `case 'api':` (before the `$target` line):
```php
if (defined('API_KEY') && API_KEY !== '') {
$provided = $_SERVER['HTTP_X_API_KEY'] ?? $_REQUEST['key'] ?? '';
if ($provided !== API_KEY) {
header('HTTP/1.0 401 Unauthorized');
echo 'Invalid or missing API key';
exit;
}
}
```
- [ ] **Step 2: Test without key (no API_KEY configured)**
```bash
curl -s -o /dev/null -w "%{http_code}" "http://localhost:8080/api?url=https://example.com"
```
Expected: `200` (API_KEY not set in local config → open access)
- [ ] **Step 3: Test with key via header**
Temporarily set `API_KEY` in `src/config.inc.php` to `'testkey'`, then:
```bash
# missing key → 401
curl -s -o /dev/null -w "%{http_code}" "http://localhost:8080/api?url=https://example.com"
# header → 200
curl -s -o /dev/null -w "%{http_code}" -H "X-API-Key: testkey" "http://localhost:8080/api?url=https://example.com"
# query param → 200
curl -s -o /dev/null -w "%{http_code}" "http://localhost:8080/api?key=testkey&url=https://example.com"
# wrong key → 401
curl -s -o /dev/null -w "%{http_code}" -H "X-API-Key: wrongkey" "http://localhost:8080/api?url=https://example.com"
```
Expected: `401`, `200`, `200`, `401`
Revert the manual edit to `src/config.inc.php` after testing (it gets regenerated by `start.sh` in Docker).
- [ ] **Step 4: Document API key usage in CLAUDE.md**
In `CLAUDE.md`, add a new section under the existing content:
```markdown
## API Key
Set `API_KEY` env var in docker-compose to require authentication on all `/api` requests.
Leave unset (default) for open access.
```bash
# via header (preferred — not logged in access logs)
curl -H "X-API-Key: your-secret-key" "http://host/api?url=https://example.com"
# via query param
curl "http://host/api?key=your-secret-key&url=https://example.com"
```
## SSRF Protection
Set `BLOCK_PRIVATE_IPS=true` to reject requests to LAN, loopback, and cloud metadata IPs.
Recommended when hosting publicly. Default is off (allows local/LAN addresses).
```
- [ ] **Step 5: Commit**
```bash
git add web/index.php CLAUDE.md
git commit -m "feat: optional API key auth via X-API-Key header or ?key= param"
```
---
## Task 6: Add SSRF protection
**Files:**
- Modify: `web/index.php`
- [ ] **Step 1: Add SSRF check after viewport validation**
Insert after the `$js = ...` line (before `$serverUrl = ...`):
```php
if (defined('BLOCK_PRIVATE_IPS') && BLOCK_PRIVATE_IPS) {
$host = parse_url($target, PHP_URL_HOST);
if (filter_var($host, FILTER_VALIDATE_IP)) {
$resolvedIp = $host;
} else {
$resolvedIp = gethostbyname($host);
if ($resolvedIp === $host) {
header('HTTP/1.0 403 Forbidden');
echo 'URL not allowed';
exit;
}
}
if (isPrivateIP($resolvedIp)) {
header('HTTP/1.0 403 Forbidden');
echo 'URL not allowed';
exit;
}
}
```
- [ ] **Step 2: Test SSRF protection**
Temporarily set `BLOCK_PRIVATE_IPS` to `true` in `src/config.inc.php`, then:
```bash
# private IP → 403
curl -s -o /dev/null -w "%{http_code}" "http://localhost:8080/api?url=http://192.168.1.1/"
# loopback → 403
curl -s -o /dev/null -w "%{http_code}" "http://localhost:8080/api?url=http://127.0.0.1/"
# metadata → 403
curl -s -o /dev/null -w "%{http_code}" "http://localhost:8080/api?url=http://169.254.169.254/"
# public URL → 200
curl -s -o /dev/null -w "%{http_code}" "http://localhost:8080/api?url=https://example.com"
```
Expected: `403`, `403`, `403`, `200`
Revert the manual edit to `src/config.inc.php` after testing.
- [ ] **Step 3: Commit**
```bash
git add web/index.php
git commit -m "feat: opt-in SSRF protection via BLOCK_PRIVATE_IPS env var"
```
---
## Final state of `web/index.php` `case 'api':` block
For reference, the complete block after all tasks:
```php
case 'api':
if (defined('API_KEY') && API_KEY !== '') {
$provided = $_SERVER['HTTP_X_API_KEY'] ?? $_REQUEST['key'] ?? '';
if ($provided !== API_KEY) {
header('HTTP/1.0 401 Unauthorized');
echo 'Invalid or missing API key';
exit;
}
}
$target = substr($_SERVER['REQUEST_URI'], 5);
if (!$target || !filter_var($target, FILTER_VALIDATE_URL))
$target = $_REQUEST['url'];
if (!filter_var($target, FILTER_VALIDATE_URL)) {
header('HTTP/1.0 400 Bad Request');
echo 'Invalid URL';
exit;
}
$ip = getUserIP();
$viewport = $_REQUEST['viewport'] ?: '1024x768';
if (!preg_match('/^\d+x\d+$/', $viewport)) {
header('HTTP/1.0 400 Bad Request');
echo 'Invalid viewport format. Use WIDTHxHEIGHT (e.g., 1024x768)';
exit;
}
$vpParts = array_map('intval', explode('x', $viewport));
if ($vpParts[0] > 3840 || $vpParts[1] > 2160) {
header('HTTP/1.0 400 Bad Request');
echo 'Viewport exceeds maximum (3840x2160)';
exit;
}
$js = $_REQUEST['js'] == 'false' ? false : true;
if (defined('BLOCK_PRIVATE_IPS') && BLOCK_PRIVATE_IPS) {
$host = parse_url($target, PHP_URL_HOST);
if (filter_var($host, FILTER_VALIDATE_IP)) {
$resolvedIp = $host;
} else {
$resolvedIp = gethostbyname($host);
if ($resolvedIp === $host) {
header('HTTP/1.0 403 Forbidden');
echo 'URL not allowed';
exit;
}
}
if (isPrivateIP($resolvedIp)) {
header('HTTP/1.0 403 Forbidden');
echo 'URL not allowed';
exit;
}
}
$serverUrl = 'http://localhost:4444';
$options = new \Facebook\WebDriver\Chrome\ChromeOptions();
$options->addArguments(['--headless', '--disable-gpu', '--no-sandbox', '--disable-dev-shm-usage']);
$capabilities = DesiredCapabilities::chrome();
$capabilities->setCapability(\Facebook\WebDriver\Chrome\ChromeOptions::CAPABILITY, $options);
if (!$js)
$capabilities->setCapability('javascriptEnabled', false);
$driver = null;
$error = null;
try {
$driver = RemoteWebDriver::create($serverUrl, $capabilities, 30000, 60000);
$driver->manage()->window()->setSize(new \Facebook\WebDriver\WebDriverDimension($vpParts[0], $vpParts[1]));
$driver->get($target);
$driver->executeScript('document.body.style.overflow = "hidden";');
addToLog("$ip\tRequested $target with viewport $viewport and js " . ($js ? 'enabled' : 'disabled'));
$screenshot = $driver->takeScreenshot();
header('Content-Type: image/png');
header('Content-Length: ' . strlen($screenshot));
echo $screenshot;
} catch (Exception $e) {
$error = $e->getMessage();
addToLog("$ip\tRequested $target but resulted in error:\t" . $error);
} finally {
if ($driver instanceof RemoteWebDriver) {
try { $driver->quit(); } catch (Exception $q) {}
}
}
if ($error !== null) {
header('HTTP/1.0 500 Internal Server Error');
echo 'Screenshot failed';
}
break;
```