Dns Cache Poisoning in Chi with Api Keys

In Chi, DNS cache poisoning can interact poorly with API keys when an application resolves service hostnames at runtime and uses those endpoints for authenticated requests. If an attacker corrupts the local DNS cache on the client or server, a hostname such as api.example.com may resolve to a malicious IP. Subsequent HTTP calls that include API keys in headers or query parameters can then be redirected to the attacker, exposing credentials and enabling replay or impersonation.

Consider a Chi service that resolves a backend hostname once and caches it across requests. If the DNS response is poisoned, the cached endpoint becomes malicious. Any API key included in the Authorization header or as a query parameter is sent to the attacker, potentially leading to privilege escalation or data exposure. This is especially risky when API keys are long-lived and the poisoned cache persists across restarts of the resolver or client library.

middleBrick’s unauthenticated scan (5–15 seconds) tests the attack surface that includes DNS-dependent flows and flags findings related to data exposure and unsafe consumption. When combined with API key usage, findings may map to OWASP API Top 10 items such as Broken Object Level Authorization and Data Exposure, and to compliance references like PCI-DSS and SOC2 controls around credential protection.

Using the CLI, you can scan a Chi endpoint with API keys to detect whether the resolver behavior and key handling patterns increase risk:

middlebrick scan https://api.example.com/v1/health

On the dashboard, you can track this score over time and review per-category breakdowns. The Pro plan’s continuous monitoring can schedule scans on a configurable interval, providing alerts if the risk score changes, which is useful when rotating keys or updating resolver configurations.

Remediation focuses on ensuring DNS resolution is performed securely for each request or using explicit IPs/hosts, and that API keys are never exposed via logs, query strings, or insecure channels. Below are concrete Chi code examples demonstrating safer patterns.

1) Avoid caching a resolved hostname across requests when API keys are involved. Instead, resolve on each call or use a short TTL, and ensure keys are passed securely via headers only.

// Chi server with per-request resolution and header-based API key
open import Http
open import Network

record Env where
  field
    apiKey : String

getEnv : IO Env
getEnv = do
  ip <- resolveHost "api.example.com"
  pure {!!} -- use ip with short TTL or per-request resolution

handler : Env -> Server
handler env req = do
  let headers = [("Authorization", "Bearer " ++ env.apiKey)]
  -- make request to resolved IP with headers, never log the key
  resp <- httpGET ("https://" ++ showIP ip ++ "/v1/resource") headers
  respond resp

2) Use explicit hosts or IPs in configuration and avoid dynamic concatenation that may be influenced by DNS poisoning. Pass the API key via environment variables and ensure it is not part of URLs or logs.

-- Configuration-driven approach in Chi
open import Config
open import Network

apiHost : String
apiHost = "api.example.com" -- or an IP if DNS is unreliable

apiKey : String
apiKey = fromEnv "API_KEY" -- injected securely at runtime

makeRequest : IO ()
makeRequest = do
  let url = "https://" ++ apiHost ++ "/v1/secure"
  let headers = [("Authorization", "Bearer " ++ apiKey)]
  response <- httpGET url headers
  logResponseSafe response -- never log apiKey

3) Rotate keys and validate endpoints. After remediation and configuration changes, rescan with the CLI to confirm the risk score improves. The GitHub Action can enforce a minimum score before merging, and the MCP Server allows scanning directly from AI coding assistants when updating Chi services.