Below we articulate the Envoy threat model, which is of relevance to Envoy operators, developers and security researchers. We detail our security release process at https://github.com/envoyproxy/envoy/security/policy.
Confidentiality, integrity and availability¶
We consider vulnerabilities leading to the compromise of data confidentiality or integrity to be our highest priority concerns. Availability, in particular in areas relating to DoS and resource exhaustion, is also a serious security concern for Envoy operators, in particular those utilizing Envoy in edge deployments.
The Envoy availability stance around CPU and memory DoS, as well as Query-of-Death (QoD), is still evolving. We will continue to iterate and fix well known resource issues in the open, e.g. overload manager and watermark improvements. We will activate the security process for disclosures that appear to present a risk profile that is significantly greater than the current Envoy availability hardening status quo. Examples of disclosures that would elicit this response:
QoD; where a single query from a client can bring down an Envoy server.
Highly asymmetric resource exhaustion attacks, where very little traffic can cause resource exhaustion, e.g. that delivered by a single client.
Note that we do not currently consider the default settings for Envoy to be safe from an availability perspective. It is necessary for operators to explicitly configure watermarks, the overload manager, circuit breakers and other resource related features in Envoy to provide a robust availability story. We will not act on any security disclosure that relates to a lack of safe defaults. Over time, we will work towards improved safe-by-default configuration, but due to backwards compatibility and performance concerns, this will require following the breaking change deprecation policy.
Data and control plane¶
We divide our threat model into data and control plane, reflecting the internal division in Envoy of these concepts from an architectural perspective. Our highest priority in risk assessment is the threat posed by untrusted downstream client traffic on the data plane. This reflects the use of Envoy in an edge serving capacity and also the use of Envoy as an inbound destination in a service mesh deployment.
In addition, we have an evolving position towards any vulnerability that might be exploitable by untrusted upstreams. We recognize that these constitute a serious security consideration, given the use of Envoy as an egress proxy. We will activate the security release process for disclosures that appear to present a risk profile that is significantly greater than the current Envoy upstream hardening status quo.
The control plane management server is generally trusted. We do not consider wire-level exploits against the xDS transport protocol to be a concern as a result. However, the configuration delivered to Envoy over xDS may originate from untrusted sources and may not be fully sanitized. An example of this might be a service operator that hosts multiple tenants on an Envoy, where tenants may specify a regular expression on a header match in RouteConfiguration. In this case, we expect that Envoy is resilient against the risks posed by malicious configuration from a confidentiality, integrity and availability perspective, as described above.
We generally assume that services utilized for side calls during the request processing, e.g. external authorization, credential suppliers, rate limit services, are trusted. When this is not the case, an extension will explicitly state this in its documentation.
Core and extensions¶
Anything in the Envoy core may be used in both untrusted and trusted deployments. As a consequence, it should be hardened with this model in mind. Security issues related to core code will usually trigger the security release process as described in this document.
The following extensions are intended to be hardened against untrusted downstream and upstreams:
The following extensions should not be exposed to data plane attack vectors and hence are intended to be robust to untrusted downstreams and upstreams:
The following extensions are intended to be hardened against untrusted downstreams but assume trusted upstreams:
The following extensions should only be used when both the downstream and upstream are trusted:
The following extensions have an unknown security posture:
Envoy currently has two dynamic filter extensions that support loadable code; WASM and Lua. In both cases, we assume that the dynamically loaded code is trusted. We expect the runtime for Lua to be robust to untrusted data plane traffic with the assumption of a trusted script. WASM is still in development, but will eventually have a similar security stance.