Server Side Template Injection in Restify with Cockroachdb

Server Side Template Injection (SSTI) occurs when an attacker can inject template directives that are subsequently evaluated by a server-side template engine. In a Restify service that renders responses using a templating engine (for example to produce dynamic HTML or error pages) and that also queries Cockroachdb, SSTI becomes a critical risk when user-controlled input is incorporated into templates without proper escaping or sandboxing.

Consider a typical Restify handler that builds a response using a template string derived from request parameters or configuration. If the handler passes unchecked input into the template engine, an attacker can inject control structures that cause arbitrary code execution. Because the application connects to Cockroachdb, the injected template may be used to form database queries or to process results, enabling second-order attacks such as extracting sensitive rows or manipulating data before they are rendered.

The combination of Restify, a Node.js-focused HTTP framework, with Cockroachdb, a distributed SQL database, can amplify exposure when templates are constructed dynamically using data from the database. For example, an endpoint might fetch a user profile from Cockroachdb and then render it using a template that includes fields like username or bio. If those fields are stored with untrusted content and later rendered without escaping, an attacker who can influence stored content might achieve SSTI. Additionally, if the application uses template-level functions to format dates or currency obtained from Cockroachdb, malicious input can trigger unexpected execution paths when those functions are invoked through injected template syntax.

Real-world attack patterns mirror known OWASP API Top 10 items such as Injection and Broken Object Level Authorization when templates expose database fields used in conditional logic. An attacker may attempt to break out of the template context to execute arbitrary JavaScript, potentially reaching for environment variables or configuration that includes connection strings or credentials for Cockroachdb. Because middleBrick scans test input validation and unsafe consumption in parallel with data exposure checks, it can surface cases where unescaped data from Cockroachdb reaches templates, indicating a high-risk exposure that requires immediate remediation.

In practice, developers should treat any data flowing from Cockroachdb into a Restify response pipeline as potentially hostile. This includes query results, metadata, and any configuration values that templates consume. Without strict output encoding and strict separation of data and logic, SSTI against Restify with Cockroachdb can lead to unauthorized data access, manipulation of database operations, or further pivots within the infrastructure.

Remediation focuses on preventing untrusted data from being interpreted as template directives and ensuring that database interactions remain strictly parameterized. Below are concrete Restify examples that demonstrate secure handling of Cockroachdb results.

1. Use explicit escaping when rendering database fields

Always escape data inserted into HTML templates. If you use a templating library such as handlebars, enable autoescape or apply escaping explicitly.

const escapeHtml = (unsafe) => {
  if (!unsafe) return '';
  return unsafe
    .replace(/&/g, '&')
    .replace(/</g, '<')
    .replace(/>/g, '>')
    .replace(/"/g, '"')
    .replace(/'/g, ''');
};

server.get('/profile/:userId', async (req, res, next) => {
  const userId = req.params.userId;
  // Assume getProfile queries Cockroachdb and returns an object
  const profile = await getProfile(userId);
  // Explicitly escape fields used in templates
  const safeData = {
    username: escapeHtml(profile.username),
    bio: escapeHtml(profile.bio),
    displayName: escapeHtml(profile.displayName)
  };
  res.send(template.render('profile.hbs', safeData));
  next();
});

2. Parameterized SQL queries to avoid injection at the database layer

Never concatenate user input into SQL strings. Use parameterized queries with Cockroachdb drivers to ensure values are never interpreted as executable SQL.

const { Client } = require('pg'); // Cockroachdb compatible PostgreSQL driver

async function getUserById(userId) {
  const client = new Client({ connectionString: process.env.DATABASE_URL });
  await client.connect();
  try {
    const result = await client.query('SELECT id, username, email FROM users WHERE id = $1', [userId]);
    return result.rows[0];
  } finally {
    await client.end();
  }
}

3. Validate and sanitize inputs before database and template use

Apply strict validation on identifiers such as userId. Use allowlists and reject unexpected formats to reduce the attack surface that could lead to SSTI or malformed queries.

function isValidUserId(userId) {
  // Allow only alphanumeric and underscores, typical UUID or integer-like patterns
  return /^[a-zA-Z0-9_-]{1,64}$/.test(userId);
}

server.get('/settings/:userId', async (req, res, next) => {
  const userId = req.params.userId;
  if (!isValidUserId(userId)) {
    res.code(400).send({ error: 'invalid user id' });
    return next();
  }
  const settings = await getSettingsFromCockroachdb(userId);
  res.send(settings);
  next();
});

4. Prefer data-only templates and avoid eval-like features

Avoid template engines that permit arbitrary JavaScript execution. When you must use features like helpers or partials, ensure they are explicitly whitelisted and do not execute code based on raw user input.

// Example: Configure handlebars to disallow inline expressions that could execute code
const Handlebars = require('handlebars');
const safeHelper = Handlebars.registerHelper('formatCurrency', (value) => {
  // Pure transformation, no eval or dynamic code execution
  return new Intl.NumberFormat('en-US', { style: 'currency', currency: 'USD' }).format(value);
});

// Render with strict context
const source = Handlebars.compile('Total: {{formatCurrency total}}');
const html = source({ total: 12999 }); // total from Cockroachdb, already validated
res.send(html);