Add blog post on hardening the Collector

content/en/blog/2024/hardening-the-collector-one.md

@@ -0,0 +1,134 @@
+---
+title: 'Hardening the Collector Episode 1: A new default bind address'
+linkTitle: A new default bind address for the Collector
+date: 2024-07-02
+author: '[Pablo Baeyens](https://github.com/mx-psi) (OpenTelemetry, Datadog)'
+# prettier-ignore
+cSpell:ignore: awsfirehose awsproxy awsxray Baeyens jaegerremotesampling loki remotetap sapm signalfx skywalking splunk
+issue: 4760
+sig: Collector SIG
+---
+
+The OpenTelemetry Collector recently went through a security audit sponsored by
+the [CNCF](https://www.cncf.io/). As part of this process we recently published
+a security advisory related to a [DoS vulnerability](/blog/2024/cve-2024-36129/)
+that was fully addressed in v0.102.1.
+
+The security audit also motivated us to think about ways to harden official
+Collector builds and have a more secure default configuration. We are
+[actively][releases-586] [working][core-10469] [on several changes][core-10470]
+to achieve this and we will be publishing a series of blog posts to keep the
+community informed.
+
+One of the changes we have recently been working on is changing the default bind
+address for Collector servers, such as those exposed by receivers or extensions
+that listen for incoming connections. Up to v0.103.0, the default behavior was
+to listen on all network interfaces by using the
+[unspecified address `0.0.0.0`](https://en.wikipedia.org/wiki/0.0.0.0) on server
+addresses. While this is a convenient default for test cases and development
+environments, it is
+[not the recommended practice for production environments](https://cwe.mitre.org/data/definitions/1327.html),
+since it can expose the Collector servers to unnecessary risks. Starting on
+v0.104.0 the default bind address becomes `localhost` for all Collector servers.
+
+It has been a long way to get here. We started discussing changing this in
+relation to [CVE-2022-27664](https://github.com/advisories/GHSA-69cg-p879-7622)
+on [v0.63.0 (September 2022)][core-6151], when we added a warning and improved
+our documentation. On [v0.94.0 (September 2023)][core-8510], we decided to add a
+feature gate, `component.UseLocalHostAsDefaultHost` to allow users to opt-in to
+the new behavior. Finally, this feature gate was enabled by default on [v0.104.0
+(June 2024)][core-10352] motivated by
+[CVE-2024-36129](/blog/2024/cve-2024-36129/).
+
+## What is changing?
+
+Starting on v0.104.0, the default bind address of all servers exposed by the
+Collector are `localhost` instead of `0.0.0.0`. For example, the OTLP receiver
+default endpoints for OTLP/gRPC and OTLP/HTTP are now `localhost:4317` and
+`localhost:4318` respectively. The full list of components affected by this
+change is:
+
+- [`otlp` receiver](https://github.com/open-telemetry/opentelemetry-collector/tree/main/receiver/otlpreceiver#otlp-receiver)
+- [`awsfirehose` receiver](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/receiver/awsfirehosereceiver#aws-kinesis-data-firehose-receiver)
+- [`awsxray` receiver](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/receiver/awsxrayreceiver#aws-x-ray-receiver)
+- [`influxdb` receiver](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/receiver/influxdbreceiver#influxdb-receiver)
+- [`jaeger` receiver](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/receiver/jaegerreceiver#jaeger-receiver)
+- [`loki` receiver](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/receiver/lokireceiver#loki-receiver)
+- [`opencensus` receiver](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/receiver/opencensusreceiver#opencensus-receiver)
+- [`sapm` receiver](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/receiver/sapmreceiver#sapm-receiver)
+- [`signalfx` receiver](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/receiver/signalfxreceiver#signalfx-receiver)
+- [`skywalking` receiver](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/receiver/skywalkingreceiver#skywalking-receiver)
+- [`splunk_hec` receiver](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/receiver/splunkhecreceiver#splunk-hec-receiver)
+- [`zipkin` receiver](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/receiver/zipkinreceiver#zipkin-receiver)
+- [`zookeeper` receiver](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/receiver/zookeeperreceiver#zookeeper-receiver)
+- [`awsproxy` extension](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/extension/awsproxy#aws-proxy)
+- [`health_check` extension](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/extension/healthcheckextension#health-check)
+- [`jaegerremotesampling` extension](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/extension/jaegerremotesampling#jaegers-remote-sampling-extension)
+- [`remotetap` processor](https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/processor/remotetapprocessor#remote-tap-processor)
+
+When in doubt, check the specific components' documentation to see the new
+default values.
+
+## What does it mean to me?
+
+If you are relying on the default configuration you may need to start explicitly
+setting the endpoint on your Collector components. For example, if you are using
+the following configuration with the OTLP receiver:
+
+```yaml
+receivers:
+  otlp:
+    protocols:
+      grpc:
+```
+
+You may now need to explicitly set the `otlp::protocols::grpc::endpoint`
+[configuration setting](https://github.com/open-telemetry/opentelemetry-collector/blob/v0.103.0/receiver/otlpreceiver/config.md):
+
+```yaml
+receivers:
+  otlp:
+    protocols:
+      grpc:
+        endpoint: ${env:HOST_IP}:4317
+```
+
+where the `HOST_IP` environment variable should is set to the bind address you
+want to use (for example, `status.podIP` on Kubernetes).
+
+Note that you are not affected if using the default configuration on the
+[OpenTelemetry Collector Helm Chart][helm-chart] or if you use the default
+configuration on any of the officially released OpenTelemetry Collector Docker
+images.
+
+## How can I prepare for this change?
+
+Since v0.63.0 the Collector logs a warning related to this when you have an
+endpoint using the 0.0.0.0 address. Before upgrading, you can check for this
+warning and address it. From v0.94.0 to v0.103.0 you can also preview the impact
+of this change by [enabling][feature-gate] the
+`component.UseLocalHostAsDefaultHost` feature gate.
+
+Addressing this change should be straightforward, however, due to the number of
+components that are impacted, starting on v0.104.0 you can temporarily opt out
+of this change by disabling the `component.UseLocalHostAsDefaultHost` feature
+gate so you can work on addressing this at your own pace. This feature gate will
+be marked as stable in a future Collector release, so we recommend addressing
+this as soon as possible.
+
+[helm-chart]:
+  https://github.com/open-telemetry/opentelemetry-helm-charts?tab=readme-ov-file#opentelemetry-collector
+[feature-gate]:
+  https://github.com/open-telemetry/opentelemetry-collector/tree/v0.103.0/featuregate#controlling-gates
+[releases-586]:
+  https://github.com/open-telemetry/opentelemetry-collector-releases/issues/586
+[core-6151]:
+  https://github.com/open-telemetry/opentelemetry-collector/issues/6151
+[core-8510]:
+  https://github.com/open-telemetry/opentelemetry-collector/issues/8510
+[core-10469]:
+  https://github.com/open-telemetry/opentelemetry-collector/issues/10469
+[core-10470]:
+  https://github.com/open-telemetry/opentelemetry-collector/issues/10470
+[core-10352]:
+  https://github.com/open-telemetry/opentelemetry-collector/pull/10352