otelgrpc DoS vulnerability due to unbound cardinality metrics

Summary

The grpc Unary Server Interceptor opentelemetry-go-contrib/instrumentation/google.golang.org/grpc/otelgrpc/interceptor.go

// UnaryServerInterceptor returns a grpc.UnaryServerInterceptor suitable
// for use in a grpc.NewServer call.
func UnaryServerInterceptor(opts ...Option) grpc.UnaryServerInterceptor {

out of the box adds labels

• net.peer.sock.addr
• net.peer.sock.port

that have unbound cardinality. It leads to the server’s potential memory exhaustion when many malicious requests are sent.

Details

An attacker can easily flood the peer address and port for requests.

PoC

Apply the attached patch to the example and run the client multiple times. Observe how each request will create a unique histogram and how the memory consumption increases during it.

Impact

In order to be affected, the program has to configure a metrics pipeline, use UnaryServerInterceptor, and does not filter any client IP address and ports via middleware or proxies, etc.

Others

It is similar to already reported vulnerabilities.

• GHSA-rcjv-mgp8-qvmr (open-telemetry/opentelemetry-go-contrib)

• GHSA-5r5m-65gx-7vrh (open-telemetry/opentelemetry-go-contrib)
• GHSA-cg3q-j54f-5p7p (prometheus/client_golang)

Workaround for affected versions

As a workaround to stop being affected, a view removing the attributes can be used.

The other possibility is to disable grpc metrics instrumentation by passing otelgrpc.WithMeterProvider option with noop.NewMeterProvider.

Solution provided by upgrading

In PR #4322, to be released with v0.46.0, the attributes were removed.

References

• #4322