Memory Leak in Chi with Basic Auth

A memory leak in a Chi application using HTTP Basic Authentication can occur when request-scoped resources are not released correctly, and the authentication mechanism inadvertently retains references that prevent garbage collection. In Chi, a common pattern is to attach user identity or parsed credentials to the request context via middleware. If the middleware stores parsed Basic Auth values (username and password) in request context without cleaning up, or if handlers allocate buffers for authentication payloads on each request without releasing them, the cumulative effect is a gradual increase in memory usage over time.

For example, consider a Chi handler that decodes the Authorization header on every request and places the decoded credentials into the request state for downstream handlers. If the decoding logic allocates new objects for each request and those objects are referenced in a context that persists beyond the request lifecycle (e.g., through closures or global caches), the garbage collector cannot reclaim that memory. This becomes more pronounced under sustained load, where many authenticated requests accumulate unreleased objects. The leak is not in the authentication logic per se, but in how the application manages the lifecycle of objects associated with authenticated requests.

Additionally, if the application uses response writers or logging mechanisms that capture request details including authentication tokens, and those logs are held in memory before being flushed or rotated, memory consumption can grow unexpectedly. chi middleware that wraps handlers and retains references to request bodies or headers without explicit cleanup can contribute to this pattern. Because Basic Auth credentials are often base64-encoded strings attached to every request, their repeated allocation without release can exacerbate the leak.

In a black-box scan using middleBrick, such leaks may not be directly detected within the 5–15 second window, but the scanner’s checks around Input Validation and Unsafe Consumption can surface indicators that request handling paths retain unexpected state. Findings related to improper resource handling can map to broader categories such as OWASP API Top 10:2023 A04 (Insecure Design) and A07 (Identification and Authentication Failures), emphasizing the need for disciplined memory management in authenticated endpoints.

To identify potential memory-related issues, developers can use runtime profiling alongside middleBrick’s security posture scoring, combining operational telemetry with security insights. The scanner’s unauthenticated attack surface testing can reveal endpoints that accept malformed or repeated authentication inputs, which may correlate with inefficient resource handling when those inputs are processed repeatedly.

To mitigate memory leaks in Chi when using HTTP Basic Authentication, ensure that all per-request allocations are short-lived and do not escape the request scope. Avoid storing parsed credentials in long-lived structures or request context fields that persist beyond the handler chain. Instead, process credentials inline within the handler or middleware and release references as soon as possible.

Below are concrete Chi code examples demonstrating safe handling of Basic Auth credentials.

Example 1: Parsing and discarding credentials within a handler

import Network.HTTP.Types
import Web.Hex (Request, Response, responseLBS)
import qualified Data.ByteString.Char8 as BC
import qualified Data.ByteString.Base64 as B64

authHandler :: Request -> IO Response
authHandler req = do
  let authHeader = lookup "Authorization" (requestHeaders req)
  case authHeader of
    Just (h, val) | BC.isPrefixOf "Basic " h ->
      let encodedCreds = BC.drop 6 val
          decoded = either (const "") BC.pack (B64.decode encodedCreds)
          (user, pass) = break (== ':') decoded
      in responseLBS status200 [] ("Authenticated: " <> BC.pack user)
    _ -> responseLBS status401 [] "Missing credentials"

This approach decodes the credentials within the handler’s execution and does not retain references beyond the response is constructed, allowing garbage collection to reclaim memory promptly.

Example 2: Middleware that validates credentials without persistent context storage

import Network.HTTP.Types
import Web.Hex (Middleware, Request, Response, responseLBS, modifyResponse)
import qualified Data.ByteString.Char8 as BC
import qualified Data.ByteString.Base64 as B64

basicAuthMiddleware :: Middleware
basicAuthMiddleware app req respond =
  case lookup "Authorization" (requestHeaders req) of
    Just (h, val) | BC.isPrefixOf "Basic " h ->
      let encodedCreds = BC.drop 6 val
          decoded = either (const "") BC.pack (B64.decode encodedCreds)
          isValid = checkCredentials decoded
      in if isValid
           then app req respond
           else respond (responseLBS status403 [] "Forbidden")
    _ -> respond (responseLBS status401 [] "Unauthorized")
  where
    checkCredentials creds = creds == "admin:secret"

This middleware validates credentials on each request and immediately passes control to the application or returns an error, without storing parsed values in global or long-lived state. The basicAuthMiddleware function is applied to the Chi application pipeline and ensures no authentication artifacts remain in memory after the response is sent.

Developers should also consider using more secure authentication mechanisms where feasible, but when Basic Auth is required, ensuring transient handling and avoiding context retention are key practices to prevent memory leaks.