[extension/opamp] Redact values in effective config (#33267)

**Description:** <Describe what has changed.>

Redacts primitive values in the effective config reported by the
extension.

Necessary for
#31641
until
open-telemetry/opentelemetry-collector#10139 is
resolved.

Relates to
#32983

.chloggen/redact-effective-config.yaml

@@ -0,0 +1,33 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: breaking
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: extension/opamp
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Redact all values in the effective config
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [33267]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: |
+  All values will be treated as if they are a `configopaque.String` type. This will
+  be changed once the Collector APIs are updated to unmarshal the config while
+  only redacting actual `configopaque.String`-typed values.
+
+  The exception to redaction is the `service::pipelines` section, which is useful
+  for debugging and does not contain any `configopaque.String` values.
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

extension/opampextension/opamp_agent.go

@@ -28,6 +28,13 @@ import (
 	"github.com/open-telemetry/opentelemetry-collector-contrib/extension/opampcustommessages"
 )
 
+const redactedVal = "[REDACTED]"
+
+// Paths that will not have values redacted when reporting the effective config.
+var unredactedPaths = []string{
+	"service::pipelines",
+}
+
 type opampAgent struct {
 	cfg    *Config
 	logger *zap.Logger
@@ -261,6 +268,46 @@ func (o *opampAgent) updateAgentIdentity(instanceID ulid.ULID) {
 	o.instanceID = instanceID
 }
 
+func redactConfig(cfg any, parentPath string) {
+	switch val := cfg.(type) {
+	case map[string]any:
+		for k, v := range val {
+			path := parentPath
+			if path == "" {
+				path = k
+			} else {
+				path += "::" + k
+			}
+			// We don't want to redact certain parts of the config
+			// that are known not to contain secrets, e.g. pipelines.
+			for _, p := range unredactedPaths {
+				if p == path {
+					return
+				}
+			}
+			switch x := v.(type) {
+			case map[string]any:
+				redactConfig(x, path)
+			case []any:
+				redactConfig(x, path)
+			default:
+				val[k] = redactedVal
+			}
+		}
+	case []any:
+		for i, v := range val {
+			switch x := v.(type) {
+			case map[string]any:
+				redactConfig(x, parentPath)
+			case []any:
+				redactConfig(x, parentPath)
+			default:
+				val[i] = redactedVal
+			}
+		}
+	}
+}
+
 func (o *opampAgent) composeEffectiveConfig() *protobufs.EffectiveConfig {
 	o.eclk.RLock()
 	defer o.eclk.RUnlock()
@@ -269,7 +316,9 @@ func (o *opampAgent) composeEffectiveConfig() *protobufs.EffectiveConfig {
 		return nil
 	}
 
-	conf, err := yaml.Marshal(o.effectiveConfig.ToStringMap())
+	m := o.effectiveConfig.ToStringMap()
+	redactConfig(m, "")
+	conf, err := yaml.Marshal(m)
 	if err != nil {
 		o.logger.Error("cannot unmarshal effectiveConfig", zap.Any("conf", o.effectiveConfig), zap.Error(err))
 		return nil

extension/opampextension/opamp_agent_test.go

@@ -176,7 +176,8 @@ func TestComposeEffectiveConfig(t *testing.T) {
 	ecFileName := filepath.Join("testdata", "effective.yaml")
 	cm, err := confmaptest.LoadConf(ecFileName)
 	assert.NoError(t, err)
-	expected, err := os.ReadFile(ecFileName)
+	redactedFileName := filepath.Join("testdata", "effective-redacted.yaml")
+	expected, err := os.ReadFile(redactedFileName)
 	assert.NoError(t, err)
 
 	o.updateEffectiveConfig(cm)

extension/opampextension/testdata/effective-redacted.yaml

@@ -0,0 +1,27 @@
+exporters:
+  otlp:
+    endpoint: "[REDACTED]"
+receivers:
+  otlp:
+    protocols:
+      grpc: {}
+      http: {}
+processors:
+  transform:
+    error_mode: "[REDACTED]"
+    metric_statements:
+      - context: "[REDACTED]"
+        conditions: 
+          - "[REDACTED]"
+        statements:
+          - "[REDACTED]"
+service:
+  pipelines:
+    traces:
+      receivers: [otlp]
+      processors: []
+      exporters: [otlp]
+    metrics:
+      receivers: [otlp]
+      processors: [transform]
+      exporters: [otlp]

extension/opampextension/testdata/effective.yaml

@@ -6,9 +6,22 @@ receivers:
     protocols:
       grpc: {}
       http: {}
+processors:
+  transform:
+    error_mode: ignore
+    metric_statements:
+      - context: metric
+        conditions: 
+          - type == METRIC_DATA_TYPE_SUM
+        statements:
+          - set(description, "Sum")
 service:
   pipelines:
     traces:
       receivers: [otlp]
       processors: []
       exporters: [otlp]
+    metrics:
+      receivers: [otlp]
+      processors: [transform]
+      exporters: [otlp]