Injection Flaws in Sinatra with Cockroachdb

Injection flaws occur when untrusted data is interpreted as part of a command or query. In Sinatra applications that use CockroachDB, the combination of dynamic SQL construction and CockroachDB SQL compatibility with PostgreSQL syntax can expose injection risks if inputs are not properly handled. Sinatra does not enforce parameterized queries by default, and developers may concatenate user input into SQL strings, which CockroachDB will execute as written. Because CockroachDB supports rich SQL features (e.g., JSONB operators, array functions, and PostgreSQL-like type casting), an injected payload can traverse nested structures or exploit type coercion to bypass simple validation checks.

For example, an endpoint like /users/:id might build a query using string interpolation: "SELECT * FROM users WHERE id = '#{params[:id]}'". If an attacker supplies 1 OR 1=1 as the id, CockroachDB receives a syntactically valid query that returns all rows. CockroachDB's JSON operators (e.g., -> and ->>) can also be abused if input is embedded into JSON path expressions, allowing an attacker to manipulate traversal and extract unintended data. Additionally, CockroachDB's support for prepared statements via the PostgreSQL protocol means that improperly parameterized queries still reach the database as raw strings, preserving injection vectors. Middleware or libraries that modify request parameters before they reach route handlers may also inadvertently pass tainted values into queries, compounding the risk.

Another subtle vector involves type confusion: CockroachDB's implicit type casting (e.g., treating a string that looks like a number as an integer) can cause injection payloads to bypass naive type checks. An attacker might supply '1'::jsonb as input, which CockroachDB accepts and interprets as a JSONB value, potentially altering query logic when used inside jsonb_set or similar functions. Because Sinatra applications often lack strict input validation and schema-level constraints, these payloads can propagate into administrative queries or logging routines, leading to data exposure or privilege escalation patterns mapped by middleBrick's BOLA/IDOR and Property Authorization checks.

Remediation centers on strict use of parameterized statements and avoiding string interpolation for SQL. With CockroachDB, use the pg Ruby gem (which speaks the PostgreSQL protocol) and always use prepared statements or query placeholders. Never embed user input directly into SQL strings, even for dynamic table or column names; if dynamic identifiers are required, use an allowlist and strict validation.

Safe query patterns with examples

• Using placeholders with the pg gem:

require 'sinatra'
require 'pg'

configure do
  set :db_config, {
    host: 'localhost',
    port: 26257,
    dbname: 'appdb',
    user: 'appuser',
    password: 'secure_password'
  }
end

def db
  @db ||= PG.connect(settings.db_config)
end

# Safe parameterized query
get '/users/:id' do
  user_id = params[:id]
  result = db.exec_params('SELECT id, name, email FROM users WHERE id = $1', [user_id])
  result.ntuples.zero? ? { error: 'Not found' }.to_json : result.first.to_json
end

• Handling JSONB inputs safely:

# Assume we query a jsonb column 'profile' for a key provided by the user
get '/profile' do
  key = params[:key]
  # Validate key against an allowlist to prevent injection via JSON path-like input
  allowed_keys = ['theme', 'language', 'timezone']
  halt 400, { error: 'Invalid key' }.to_json unless allowed_keys.include?(key)

  result = db.exec_params('SELECT profile -> $1 AS value FROM accounts WHERE id = $2', [key, current_user_id])
  result.ntuples.zero? ? { error: 'Not found' }.to_json : result.first.to_json
end

• Dynamic identifiers with strict allowlist:

VALID_SORT_COLUMNS = %w[name created_at updated_at]

get '/users' do
  column = params[:sort] || 'created_at'
  direction = %w[asc desc].include?(params[:dir]&.downcase) ? params[:dir].upcase : 'ASC'
  column = 'created_at' unless VALID_SORT_COLUMNS.include?(column)

  # Safe: column and direction are controlled by allowlist, not user input directly
  db.exec("SELECT id, name FROM users ORDER BY #{column} #{direction}").map(&:to_h).to_json
end

Additional practices: enable CockroachDB's prepared statement pooling where available, and validate input lengths and formats before use. middleBrick scans can surface injection-prone endpoints by correlating API paths with database interaction patterns; the Pro plan's continuous monitoring can alert you when new endpoints introduce risky query construction.