feature: automatically redact passwords in logs

config.default.ini

@@ -31,6 +31,7 @@ log_static_requests=false
 log_404_to_error_log=false
 log_not_modified=false
 log_redirects=false
+ignore_post_fields=password,pass,passwd,password_confirm,password_confirmation,current_password,new_password,old_password,secret,client_secret,token,access_token,refresh_token,id_token,api_key,apikey,authorization,auth,bearer,otp,totp,mfa_code,verification_code,recovery_code,card_number,cc_number,credit_card,cvv,cvc,pin
 debug_to_javascript=true
 stderr_level=ERROR
 type=stdout

src/Application.php

@@ -41,6 +41,8 @@
  * @SuppressWarnings("PHPMD.ExcessiveClassComplexity")
  */
 class Application {
+	private const string REDACTED_LOG_VALUE = "[redacted]";
+
 	private Redirect $redirect;
 	private Timer $timer;
 	private OutputBuffer $outputBuffer;
@@ -575,6 +577,59 @@ private function shouldLogRequest(Response $response):bool {
 	 */
 	private function filterLoggedPostBody(array $postBody):array {
 		unset($postBody[HTMLDocumentProtector::TOKEN_NAME]);
+		return $this->redactIgnoredPostFields(
+			$postBody,
+			$this->getIgnoredPostFieldLookup(),
+		);
+	}
+
+	/** @return array<string, true> */
+	private function getIgnoredPostFieldLookup():array {
+		$configuredFields = explode(
+			",",
+			$this->config->getString("logger.ignore_post_fields") ?? "",
+		);
+
+		$lookup = [];
+		foreach($configuredFields as $field) {
+			$field = strtolower(trim($field));
+			if($field === "") {
+				continue;
+			}
+
+			$lookup[$field] = true;
+		}
+
+		return $lookup;
+	}
+
+	/**
+	 * @param array<array-key, mixed> $postBody
+	 * @param array<string, true> $ignoredFieldLookup
+	 * @return array<array-key, mixed>
+	 */
+	private function redactIgnoredPostFields(
+		array $postBody,
+		array $ignoredFieldLookup,
+	):array {
+		if(!$ignoredFieldLookup) {
+			return $postBody;
+		}
+
+		foreach($postBody as $key => $value) {
+			if(is_string($key) && isset($ignoredFieldLookup[strtolower($key)])) {
+				$postBody[$key] = self::REDACTED_LOG_VALUE;
+				continue;
+			}
+
+			if(is_array($value)) {
+				$postBody[$key] = $this->redactIgnoredPostFields(
+					$value,
+					$ignoredFieldLookup,
+				);
+			}
+		}
+
 		return $postBody;
 	}
 

test/phpunit/ApplicationTest.php

@@ -41,6 +41,8 @@ public function testDefaultConfig_usesHtmlRoutingAndDoesNotLogNotModifiedRespons
 
 		self::assertSame("text/html", $config["router"]["default_content_type"]);
 		self::assertSame("false", $config["logger"]["log_not_modified"]);
+		self::assertStringContainsString("password", $config["logger"]["ignore_post_fields"]);
+		self::assertStringContainsString("pass", $config["logger"]["ignore_post_fields"]);
 	}
 
 	public function testStart_callsRedirectExecute():void {
@@ -860,7 +862,7 @@ public function testBuildLogContext_omitsObjectParsedBodyAndKeepsQueryContext():
 		self::assertArrayNotHasKey("post", $context);
 	}
 
-	public function testBuildLogContext_filtersConfiguredCsrfTokenNameOnly():void {
+	public function testBuildLogContext_filtersCsrfTokenBeforeRedactingIgnoredFields():void {
 		$sut = new Application(
 			config: $this->createTestConfig([]),
 			requestFactory: $this->createRequestFactory(),
@@ -872,14 +874,76 @@ public function testBuildLogContext_filtersConfiguredCsrfTokenNameOnly():void {
 			$sut,
 			"buildLogContext",
 			"/send",
+			[],
+				[
+					HTMLDocumentProtector::TOKEN_NAME => "CSRF_secret",
+					"token" => "business-token",
+				],
+			);
+
+		self::assertSame(["token" => "[redacted]"], $context["post"]);
+	}
+
+	public function testBuildLogContext_redactsIgnoredPostFields():void {
+		$sut = new Application(
+			config: $this->createTestConfig([]),
+			requestFactory: $this->createRequestFactory(),
+			dispatcherFactory: self::createStub(DispatcherFactory::class),
+			globalProtection: self::createStub(Protection::class),
+		);
+
+		$context = $this->invokePrivateMethod(
+			$sut,
+			"buildLogContext",
+			"/login",
 			[],
 			[
-				HTMLDocumentProtector::TOKEN_NAME => "CSRF_secret",
-				"token" => "business-token",
+				"username" => "ada",
+				"password" => "correct horse battery staple",
+				"pass" => "secret",
 			],
 		);
 
-		self::assertSame(["token" => "business-token"], $context["post"]);
+		self::assertSame([
+			"username" => "ada",
+			"password" => "[redacted]",
+			"pass" => "[redacted]",
+		], $context["post"]);
+	}
+
+	public function testBuildLogContext_redactsConfiguredPostFieldsRecursively():void {
+		$sut = new Application(
+			config: $this->createTestConfig([
+				"logger.ignore_post_fields" => " password , secret , ",
+			]),
+			requestFactory: $this->createRequestFactory(),
+			dispatcherFactory: self::createStub(DispatcherFactory::class),
+			globalProtection: self::createStub(Protection::class),
+		);
+
+		$context = $this->invokePrivateMethod(
+			$sut,
+			"buildLogContext",
+			"/account",
+			[],
+			[
+				"user" => [
+					"name" => "Grace",
+					"password" => "hidden",
+				],
+				"SECRET" => "hidden",
+				"message" => "hello",
+			],
+		);
+
+		self::assertSame([
+			"user" => [
+				"name" => "Grace",
+				"password" => "[redacted]",
+			],
+			"SECRET" => "[redacted]",
+			"message" => "hello",
+		], $context["post"]);
 	}
 
 	public function testStart_logsAllRequestsWithRequestContext():void {
@@ -924,7 +988,7 @@ public function testStart_logsAllRequestsWithRequestContext():void {
 		self::assertSame("HTTP 204", TestLogHandler::$records[0]["message"]);
 		self::assertSame("/search", TestLogHandler::$records[0]["context"]["uri"]);
 		self::assertSame(["q" => "php"], TestLogHandler::$records[0]["context"]["query"]);
-		self::assertSame(["token" => "abc"], TestLogHandler::$records[0]["context"]["post"]);
+		self::assertSame(["token" => "[redacted]"], TestLogHandler::$records[0]["context"]["post"]);
 		self::assertSame("127.0.0.1:", TestLogHandler::$records[0]["context"]["id"]);
 	}