GHSA-3q34-rx83-r6mq Heimdall has an authorization bypass via path normalization mismatch

• Go github.com/dadrus/heimdall: < 0.17.14 → fixed in 0.17.14

Summary Heimdall performs rule matching on the raw (non-normalized) request path, while downstream components may normalize dot-segments according to RFC 3986, Section 6.2.2.3. This discrepancy can result in heimdall authorizing a request for one path (e.g., `/user/../admin`, or URL-encoded variants such as `/user/%2e%2e/admin` or `/user/%2e%2e%2fadmin`. The latter would require the `allow_encoded_slashes` option to be set to `on` or `no_decode`.) while the downstream ultimately processes a different, normalized path (`/admin`). Details This vulnerability can be exploited by an adversary if rule matching is performed using free (named or unnamed) wildcards without further constraints, as shown in the example snippets below. ```yaml id: rule-1 match: routes: • path: /user/ execute: # configured to require authentication and authorization # ... ``` ```yaml id: rule-2 match: routes: • path: /public/ execute: # configured to allow anonymous access # ... ``` If an adversary sends a request to `/public/../user/whatever`, rule-2 will be matched and executed. The downstream service may, however, normalize the request path and interpret it as `/user/whatever`. Impact Bypass of access control policies enforced by heimdall may lead to the following consequences: • Access to or modification of data that should be restricted • Invocation of functionality that is expected to require authentication or authorization • In certain configurations, escalation of privileges depending on the exposed functionality Workarounds • Normalize HTTP paths or reject HTTP paths containing relative path expressions in the layers in front of Heimdall - this is good practice anyway. Some proxies do that by default, such as Traefik; others, such as Envoy, require additional configuration (for Envoy see `normalize_path`). • Include the ID of the rule expected to be executed in the JWT issued by heimdall and check that value in the consuming project's service.