Add an option to disable APM user redaction (#176566)

## Summary

Fix https://github.com/elastic/kibana/issues/174743

Add an `elastic.apm.redactUsers` configuration option that defaults to
`true` (preserving current behavior)

---------

Co-authored-by: Kibana Machine <42973632+kibanamachine@users.noreply.github.com>

packages/kbn-apm-config-loader/src/apm_config.ts

@@ -24,4 +24,5 @@ const apmReusableConfigSchema = schema.object(
 
 export const apmConfigSchema = apmReusableConfigSchema.extends({
   servicesOverrides: schema.maybe(schema.recordOf(schema.string(), apmReusableConfigSchema)),
+  redactUsers: schema.maybe(schema.boolean({ defaultValue: true })),
 });

packages/kbn-apm-config-loader/src/config.test.ts

@@ -405,4 +405,30 @@ describe('ApmConfiguration', () => {
       );
     });
   });
+
+  describe('isUsersRedactionEnabled', () => {
+    it('defaults to true', () => {
+      const kibanaConfig = {
+        elastic: {
+          apm: {},
+        },
+      };
+
+      const config = new ApmConfiguration(mockedRootDir, kibanaConfig, false);
+      expect(config.isUsersRedactionEnabled()).toEqual(true);
+    });
+
+    it('uses the value defined in the config if specified', () => {
+      const kibanaConfig = {
+        elastic: {
+          apm: {
+            redactUsers: false,
+          },
+        },
+      };
+
+      const config = new ApmConfiguration(mockedRootDir, kibanaConfig, false);
+      expect(config.isUsersRedactionEnabled()).toEqual(false);
+    });
+  });
 });

packages/kbn-apm-config-loader/src/config.ts

@@ -93,6 +93,11 @@ export class ApmConfiguration {
     return baseConfig;
   }
 
+  public isUsersRedactionEnabled(): boolean {
+    const { redactUsers = true } = this.getConfigFromKibanaConfig();
+    return redactUsers;
+  }
+
   private getBaseConfig() {
     if (!this.baseConfig) {
       const configFromSources = this.getConfigFromAllSources();
@@ -287,7 +292,8 @@ export class ApmConfiguration {
    * Reads APM configuration from different sources and merges them together.
    */
   private getConfigFromAllSources(): AgentConfigOptions {
-    const { servicesOverrides, ...configFromKibanaConfig } = this.getConfigFromKibanaConfig();
+    const { servicesOverrides, redactUsers, ...configFromKibanaConfig } =
+      this.getConfigFromKibanaConfig();
     const configFromEnv = this.getConfigFromEnv(configFromKibanaConfig);
     const config = merge({}, configFromKibanaConfig, configFromEnv);
 

packages/kbn-apm-config-loader/src/init_apm.test.ts

@@ -15,14 +15,17 @@ describe('initApm', () => {
   let apmAddFilterMock: jest.Mock;
   let apmStartMock: jest.Mock;
   let getConfig: jest.Mock;
+  let isUsersRedactionEnabled: jest.Mock;
 
   beforeEach(() => {
     apmAddFilterMock = apm.addFilter as jest.Mock;
     apmStartMock = apm.start as jest.Mock;
     getConfig = jest.fn();
+    isUsersRedactionEnabled = jest.fn();
 
     mockLoadConfiguration.mockImplementation(() => ({
       getConfig,
+      isUsersRedactionEnabled,
     }));
   });
 
@@ -46,13 +49,29 @@ describe('initApm', () => {
     expect(getConfig).toHaveBeenCalledWith('service-name');
   });
 
-  it('registers a filter using `addFilter`', () => {
+  it('calls `apmConfigLoader.isUsersRedactionEnabled`', () => {
+    initApm(['foo', 'bar'], 'rootDir', true, 'service-name');
+
+    expect(isUsersRedactionEnabled).toHaveBeenCalledTimes(1);
+  });
+
+  it('registers a filter using `addFilter` when user redaction is enabled', () => {
+    isUsersRedactionEnabled.mockReturnValue(true);
+
     initApm(['foo', 'bar'], 'rootDir', true, 'service-name');
 
     expect(apmAddFilterMock).toHaveBeenCalledTimes(1);
     expect(apmAddFilterMock).toHaveBeenCalledWith(expect.any(Function));
   });
 
+  it('does not register a filter using `addFilter` when user redaction is disabled', () => {
+    isUsersRedactionEnabled.mockReturnValue(false);
+
+    initApm(['foo', 'bar'], 'rootDir', true, 'service-name');
+
+    expect(apmAddFilterMock).not.toHaveBeenCalled();
+  });
+
   it('starts apm with the config returned from `getConfig`', () => {
     const config = {
       foo: 'bar',

packages/kbn-apm-config-loader/src/init_apm.ts

@@ -16,24 +16,27 @@ export const initApm = (
 ) => {
   const apmConfigLoader = loadConfiguration(argv, rootDir, isDistributable);
   const apmConfig = apmConfigLoader.getConfig(serviceName);
+  const shouldRedactUsers = apmConfigLoader.isUsersRedactionEnabled();
 
   // we want to only load the module when effectively used
   // eslint-disable-next-line @typescript-eslint/no-var-requires
   const apm = require('elastic-apm-node');
 
   // Filter out all user PII
-  apm.addFilter((payload: Record<string, any>) => {
-    try {
-      if (payload.context?.user && typeof payload.context.user === 'object') {
-        Object.keys(payload.context.user).forEach((key) => {
-          payload.context.user[key] = '[REDACTED]';
-        });
+  if (shouldRedactUsers) {
+    apm.addFilter((payload: Record<string, any>) => {
+      try {
+        if (payload.context?.user && typeof payload.context.user === 'object') {
+          Object.keys(payload.context.user).forEach((key) => {
+            payload.context.user[key] = '[REDACTED]';
+          });
+        }
+      } catch (e) {
+        // just silently ignore the error
       }
-    } catch (e) {
-      // just silently ignore the error
-    }
-    return payload;
-  });
+      return payload;
+    });
+  }
 
   apm.start(apmConfig);
 };