Description
Ory Oathkeeper is often deployed behind other components like CDNs, WAFs, or reverse proxies. Depending on the setup, another component might forward the request to the Oathkeeper proxy with a different protocol (http vs. https) than the original request. In order to properly match the request against the configured rules, Oathkeeper considers the X-Forwarded-Proto header when evaluating rules. The configuration option serve.proxy.trust_forwarded_headers (defaults to false) governs whether this and other X-Forwarded-* headers should be trusted. Oathkeeper did not properly respect this configuration, and would always consider the X-Forwarded-Proto header.
Preconditions
In order for an attacker to abuse this, an installation of Ory Oathkeeper needs to have distinct rules for HTTP and HTTPS requests. Also, the attacker needs to be able to trigger one but not the other rule. In this scenario, the attacker can send the same request but with the X-Forwarded-Proto header in order to trigger the other rule. We do not expect many configurations to meet these preconditions.
Mitigation
It is generally recommended to drop any unexpected headers as early as possible when a request is handled, e.g. in the WAF.
Ory Oathkeeper will correctly respect the serve.proxy.trust_forwarded_headers configuration going forward, thereby eliminating the attack scenario. We recommend upgrading to a fixed version even if the preconditions are not met.
References
Description
Ory Oathkeeper is often deployed behind other components like CDNs, WAFs, or reverse proxies. Depending on the setup, another component might forward the request to the Oathkeeper proxy with a different protocol (http vs. https) than the original request. In order to properly match the request against the configured rules, Oathkeeper considers the
X-Forwarded-Protoheader when evaluating rules. The configuration optionserve.proxy.trust_forwarded_headers(defaults to false) governs whether this and otherX-Forwarded-*headers should be trusted. Oathkeeper did not properly respect this configuration, and would always consider theX-Forwarded-Protoheader.Preconditions
In order for an attacker to abuse this, an installation of Ory Oathkeeper needs to have distinct rules for HTTP and HTTPS requests. Also, the attacker needs to be able to trigger one but not the other rule. In this scenario, the attacker can send the same request but with the
X-Forwarded-Protoheader in order to trigger the other rule. We do not expect many configurations to meet these preconditions.Mitigation
It is generally recommended to drop any unexpected headers as early as possible when a request is handled, e.g. in the WAF.
Ory Oathkeeper will correctly respect the
serve.proxy.trust_forwarded_headersconfiguration going forward, thereby eliminating the attack scenario. We recommend upgrading to a fixed version even if the preconditions are not met.References