fix: redact sensitive error values

integration-tests/it-exporter/it-exporter-test/src/test/java/io/prometheus/metrics/it/exporter/test/ExporterIT.java

@@ -157,7 +157,11 @@ void testErrorHandling() throws IOException {
     start("error");
     Response response = scrape("GET", "");
     assertThat(response.status).isEqualTo(500);
-    assertThat(response.stringBody()).contains("Simulating an error.");
+    assertThat(response.stringBody()).contains(expectedErrorResponseBody());
+  }
+
+  String expectedErrorResponseBody() {
+    return "Simulating an error.";
   }
 
   @Test

integration-tests/it-exporter/it-exporter-test/src/test/java/io/prometheus/metrics/it/exporter/test/HttpServerIT.java

@@ -7,4 +7,9 @@ class HttpServerIT extends ExporterIT {
   public HttpServerIT() throws IOException, URISyntaxException {
     super("exporter-httpserver-sample");
   }
+
+  @Override
+  String expectedErrorResponseBody() {
+    return "An Exception occurred while scraping metrics.";
+  }
 }

prometheus-metrics-config/src/main/java/io/prometheus/metrics/config/ExporterPushgatewayProperties.java

@@ -94,9 +94,8 @@ static ExporterPushgatewayProperties load(PropertySource propertySource)
     if (scheme != null) {
       if (!scheme.equals("http") && !scheme.equals("https")) {
         throw new PrometheusPropertiesException(
-            String.format(
-                "%s.%s: Illegal value. Expecting 'http' or 'https'. Found: %s",
-                PREFIX, SCHEME, scheme));
+            Util.invalidValueMessage(
+                PREFIX + "." + SCHEME, "Illegal value. Expecting 'http' or 'https'."));
       }
     }
 
@@ -119,10 +118,9 @@ static ExporterPushgatewayProperties load(PropertySource propertySource)
         return EscapingScheme.DOTS_ESCAPING;
       default:
         throw new PrometheusPropertiesException(
-            String.format(
-                "%s.%s: Illegal value. Expecting 'allow-utf-8', 'values', 'underscores', "
-                    + "or 'dots'. Found: %s",
-                PREFIX, ESCAPING_SCHEME, scheme));
+            Util.invalidValueMessage(
+                PREFIX + "." + ESCAPING_SCHEME,
+                "Illegal value. Expecting 'allow-utf-8', 'values', 'underscores', or 'dots'."));
     }
   }
 

prometheus-metrics-config/src/main/java/io/prometheus/metrics/config/MetricsProperties.java

@@ -227,11 +227,8 @@ private void validate(String prefix) throws PrometheusPropertiesException {
       for (double quantile : summaryQuantiles) {
         if (quantile < 0 || quantile > 1) {
           throw new PrometheusPropertiesException(
-              prefix
-                  + "."
-                  + SUMMARY_QUANTILES
-                  + ": Expecting 0.0 <= quantile <= 1.0. Found: "
-                  + quantile);
+              Util.invalidValueMessage(
+                  prefix + "." + SUMMARY_QUANTILES, "Expecting 0.0 <= quantile <= 1.0."));
         }
       }
     }

prometheus-metrics-config/src/main/java/io/prometheus/metrics/config/Util.java

@@ -24,7 +24,7 @@ static Boolean loadBoolean(String prefix, String propertyName, PropertySource pr
       String fullKey = prefix.isEmpty() ? propertyName : prefix + "." + propertyName;
       if (!"true".equalsIgnoreCase(property) && !"false".equalsIgnoreCase(property)) {
         throw new PrometheusPropertiesException(
-            String.format("%s: Expecting 'true' or 'false'. Found: %s", fullKey, property));
+            invalidValueMessage(fullKey, "Expecting 'true' or 'false'."));
       }
       return Boolean.parseBoolean(property);
     }
@@ -88,7 +88,7 @@ static List<Double> loadDoubleList(
           }
         } catch (NumberFormatException e) {
           throw new PrometheusPropertiesException(
-              fullKey + "=" + property + ": Expecting comma separated list of double values");
+              invalidValueMessage(fullKey, "Expecting comma separated list of double values"));
         }
       }
       return Arrays.asList(result);
@@ -130,7 +130,7 @@ static Integer loadInteger(String prefix, String propertyName, PropertySource pr
         return Integer.parseInt(property);
       } catch (NumberFormatException e) {
         throw new PrometheusPropertiesException(
-            fullKey + "=" + property + ": Expecting integer value");
+            invalidValueMessage(fullKey, "Expecting integer value"));
       }
     }
     return null;
@@ -146,7 +146,7 @@ static Double loadDouble(String prefix, String propertyName, PropertySource prop
         return Double.parseDouble(property);
       } catch (NumberFormatException e) {
         throw new PrometheusPropertiesException(
-            fullKey + "=" + property + ": Expecting double value");
+            invalidValueMessage(fullKey, "Expecting double value"));
       }
     }
     return null;
@@ -162,7 +162,7 @@ static Long loadLong(String prefix, String propertyName, PropertySource property
         return Long.parseLong(property);
       } catch (NumberFormatException e) {
         throw new PrometheusPropertiesException(
-            fullKey + "=" + property + ": Expecting long value");
+            invalidValueMessage(fullKey, "Expecting long value"));
       }
     }
     return null;
@@ -193,8 +193,12 @@ static <T extends Number> void assertValue(
     if (number != null && !predicate.test(number)) {
       String fullKey =
           (prefix == null || prefix.isEmpty()) ? propertyName : prefix + "." + propertyName;
-      String fullMessage = String.format("%s: %s Found: %s", fullKey, message, number);
-      throw new PrometheusPropertiesException(fullMessage);
+      throw new PrometheusPropertiesException(invalidValueMessage(fullKey, message));
     }
   }
+
+  static String invalidValueMessage(String fullKey, String message) {
+    String separator = message.endsWith(".") ? " " : ". ";
+    return fullKey + ": " + message + separator + "Found: <redacted>";
+  }
 }

prometheus-metrics-config/src/test/java/io/prometheus/metrics/config/ExemplarsPropertiesTest.java

@@ -25,18 +25,21 @@ void load() {
         .isThrownBy(
             () -> load(Map.of("io.prometheus.exemplars.min_retention_period_seconds", "-1")))
         .withMessage(
-            "io.prometheus.exemplars.min_retention_period_seconds: Expecting value > 0. Found: -1");
+            "io.prometheus.exemplars.min_retention_period_seconds: Expecting value > 0. Found:"
+                + " <redacted>");
 
     assertThatExceptionOfType(PrometheusPropertiesException.class)
         .isThrownBy(() -> load(Map.of("io.prometheus.exemplars.max_retention_period_seconds", "0")))
         .withMessage(
-            "io.prometheus.exemplars.max_retention_period_seconds: Expecting value > 0. Found: 0");
+            "io.prometheus.exemplars.max_retention_period_seconds: Expecting value > 0. Found:"
+                + " <redacted>");
 
     assertThatExceptionOfType(PrometheusPropertiesException.class)
         .isThrownBy(
             () -> load(Map.of("io.prometheus.exemplars.sample_interval_milliseconds", "-1")))
         .withMessage(
-            "io.prometheus.exemplars.sample_interval_milliseconds: Expecting value > 0. Found: -1");
+            "io.prometheus.exemplars.sample_interval_milliseconds: Expecting value > 0. Found:"
+                + " <redacted>");
   }
 
   private static ExemplarsProperties load(Map<String, String> map) {

prometheus-metrics-config/src/test/java/io/prometheus/metrics/config/ExporterHttpServerPropertiesTest.java

@@ -18,7 +18,8 @@ void load() {
 
     assertThatExceptionOfType(PrometheusPropertiesException.class)
         .isThrownBy(() -> load(Map.of("io.prometheus.exporter.http_server.port", "0")))
-        .withMessage("io.prometheus.exporter.http_server.port: Expecting value > 0. Found: 0");
+        .withMessage(
+            "io.prometheus.exporter.http_server.port: Expecting value > 0. Found: <redacted>");
   }
 
   @Test

prometheus-metrics-config/src/test/java/io/prometheus/metrics/config/ExporterPropertiesTest.java

@@ -28,7 +28,7 @@ void load() {
                         Map.of("io.prometheus.exporter.include_created_timestamps", "invalid"))))
         .withMessage(
             "io.prometheus.exporter.include_created_timestamps: Expecting 'true' or 'false'. Found:"
-                + " invalid");
+                + " <redacted>");
     assertThatExceptionOfType(PrometheusPropertiesException.class)
         .isThrownBy(
             () ->
@@ -37,7 +37,7 @@ void load() {
                         Map.of("io.prometheus.exporter.exemplars_on_all_metric_types", "invalid"))))
         .withMessage(
             "io.prometheus.exporter.exemplars_on_all_metric_types: Expecting 'true' or 'false'."
-                + " Found: invalid");
+                + " Found: <redacted>");
   }
 
   private static ExporterProperties load(Map<String, String> map) {
@@ -85,6 +85,6 @@ void prometheusTimestampsInMs() {
                         Map.of("io.prometheus.exporter.prometheus_timestamps_in_ms", "invalid"))))
         .withMessage(
             "io.prometheus.exporter.prometheus_timestamps_in_ms: Expecting 'true' or 'false'."
-                + " Found: invalid");
+                + " Found: <redacted>");
   }
 }

prometheus-metrics-config/src/test/java/io/prometheus/metrics/config/ExporterPushgatewayPropertiesTest.java

@@ -27,7 +27,7 @@ void load() {
         .isThrownBy(() -> load(Map.of("io.prometheus.exporter.pushgateway.scheme", "foo")))
         .withMessage(
             "io.prometheus.exporter.pushgateway.scheme: Illegal value. Expecting 'http' or 'https'."
-                + " Found: foo");
+                + " Found: <redacted>");
   }
 
   @Test
@@ -60,7 +60,7 @@ void loadWithInvalidEscapingScheme() {
             () -> load(Map.of("io.prometheus.exporter.pushgateway.escaping_scheme", "invalid")))
         .withMessage(
             "io.prometheus.exporter.pushgateway.escaping_scheme: Illegal value. Expecting"
-                + " 'allow-utf-8', 'values', 'underscores', or 'dots'. Found: invalid");
+                + " 'allow-utf-8', 'values', 'underscores', or 'dots'. Found: <redacted>");
   }
 
   @Test

prometheus-metrics-config/src/test/java/io/prometheus/metrics/config/MetricsPropertiesTest.java

@@ -47,11 +47,11 @@ void builder() {
 
     assertThatExceptionOfType(PrometheusPropertiesException.class)
         .isThrownBy(() -> MetricsProperties.builder().summaryNumberOfAgeBuckets(0).build())
-        .withMessage("summary_number_of_age_buckets: Expecting value > 0. Found: 0");
+        .withMessage("summary_number_of_age_buckets: Expecting value > 0. Found: <redacted>");
 
     assertThatExceptionOfType(PrometheusPropertiesException.class)
         .isThrownBy(() -> MetricsProperties.builder().summaryQuantiles(2L).build())
-        .withMessage(".summary_quantiles: Expecting 0.0 <= quantile <= 1.0. Found: 2.0");
+        .withMessage(".summary_quantiles: Expecting 0.0 <= quantile <= 1.0. Found: <redacted>");
 
     assertThatExceptionOfType(PrometheusPropertiesException.class)
         .isThrownBy(() -> MetricsProperties.builder().summaryQuantileErrors(0.9).build())
@@ -114,24 +114,29 @@ void nativeBuilder() {
     assertThatExceptionOfType(PrometheusPropertiesException.class)
         .isThrownBy(() -> MetricsProperties.builder().histogramNativeInitialSchema(10).build())
         .withMessage(
-            "histogram_native_initial_schema: Expecting number between -4 and +8. Found: 10");
+            "histogram_native_initial_schema: Expecting number between -4 and +8. Found:"
+                + " <redacted>");
 
     assertThatExceptionOfType(PrometheusPropertiesException.class)
         .isThrownBy(() -> MetricsProperties.builder().histogramNativeMinZeroThreshold(-1.0).build())
-        .withMessage("histogram_native_min_zero_threshold: Expecting value >= 0. Found: -1.0");
+        .withMessage(
+            "histogram_native_min_zero_threshold: Expecting value >= 0. Found: <redacted>");
 
     assertThatExceptionOfType(PrometheusPropertiesException.class)
         .isThrownBy(() -> MetricsProperties.builder().histogramNativeMaxZeroThreshold(-1.0).build())
-        .withMessage("histogram_native_max_zero_threshold: Expecting value >= 0. Found: -1.0");
+        .withMessage(
+            "histogram_native_max_zero_threshold: Expecting value >= 0. Found: <redacted>");
 
     assertThatExceptionOfType(PrometheusPropertiesException.class)
         .isThrownBy(() -> MetricsProperties.builder().histogramNativeMaxNumberOfBuckets(-1).build())
-        .withMessage("histogram_native_max_number_of_buckets: Expecting value >= 0. Found: -1");
+        .withMessage(
+            "histogram_native_max_number_of_buckets: Expecting value >= 0. Found: <redacted>");
 
     assertThatExceptionOfType(PrometheusPropertiesException.class)
         .isThrownBy(
             () -> MetricsProperties.builder().histogramNativeResetDurationSeconds(-1L).build())
-        .withMessage("histogram_native_reset_duration_seconds: Expecting value >= 0. Found: -1");
+        .withMessage(
+            "histogram_native_reset_duration_seconds: Expecting value >= 0. Found: <redacted>");
 
     assertThatExceptionOfType(PrometheusPropertiesException.class)
         .isThrownBy(

prometheus-metrics-config/src/test/java/io/prometheus/metrics/config/OpenMetrics2PropertiesTest.java

@@ -38,7 +38,7 @@ void loadInvalidValue() {
         .isThrownBy(
             () -> load(new HashMap<>(Map.of("io.prometheus.openmetrics2.enabled", "invalid"))))
         .withMessage(
-            "io.prometheus.openmetrics2.enabled: Expecting 'true' or 'false'. Found: invalid");
+            "io.prometheus.openmetrics2.enabled: Expecting 'true' or 'false'. Found: <redacted>");
     assertThatExceptionOfType(PrometheusPropertiesException.class)
         .isThrownBy(
             () ->
@@ -47,7 +47,7 @@ void loadInvalidValue() {
                         Map.of("io.prometheus.openmetrics2.content_negotiation", "invalid"))))
         .withMessage(
             "io.prometheus.openmetrics2.content_negotiation: Expecting 'true' or 'false'. Found:"
-                + " invalid");
+                + " <redacted>");
     assertThatExceptionOfType(PrometheusPropertiesException.class)
         .isThrownBy(
             () ->
@@ -56,7 +56,7 @@ void loadInvalidValue() {
                         Map.of("io.prometheus.openmetrics2.composite_values", "invalid"))))
         .withMessage(
             "io.prometheus.openmetrics2.composite_values: Expecting 'true' or 'false'. Found:"
-                + " invalid");
+                + " <redacted>");
     assertThatExceptionOfType(PrometheusPropertiesException.class)
         .isThrownBy(
             () ->
@@ -65,7 +65,7 @@ void loadInvalidValue() {
                         Map.of("io.prometheus.openmetrics2.exemplar_compliance", "invalid"))))
         .withMessage(
             "io.prometheus.openmetrics2.exemplar_compliance: Expecting 'true' or 'false'. Found:"
-                + " invalid");
+                + " <redacted>");
     assertThatExceptionOfType(PrometheusPropertiesException.class)
         .isThrownBy(
             () ->
@@ -74,7 +74,7 @@ void loadInvalidValue() {
                         Map.of("io.prometheus.openmetrics2.native_histograms", "invalid"))))
         .withMessage(
             "io.prometheus.openmetrics2.native_histograms: Expecting 'true' or 'false'. Found:"
-                + " invalid");
+                + " <redacted>");
   }
 
   private static OpenMetrics2Properties load(Map<String, String> map) {

prometheus-metrics-config/src/test/java/io/prometheus/metrics/config/UtilTest.java

@@ -41,7 +41,7 @@ void loadOptionalDuration_negative_throws() {
 
     assertThatExceptionOfType(PrometheusPropertiesException.class)
         .isThrownBy(() -> Util.loadOptionalDuration("", "foo", propertySource))
-        .withMessage("foo: Expecting value >= 0. Found: -1");
+        .withMessage("foo: Expecting value >= 0. Found: <redacted>");
   }
 
   @Test
@@ -51,6 +51,6 @@ void loadOptionalDuration_invalidNumber_throws() {
 
     assertThatExceptionOfType(PrometheusPropertiesException.class)
         .isThrownBy(() -> Util.loadOptionalDuration("", "foo", propertySource))
-        .withMessage("foo=abc: Expecting long value");
+        .withMessage("foo: Expecting long value. Found: <redacted>");
   }
 }

prometheus-metrics-exporter-httpserver/src/main/java/io/prometheus/metrics/exporter/httpserver/HttpExchangeAdapter.java

@@ -6,8 +6,6 @@
 import io.prometheus.metrics.exporter.common.PrometheusHttpResponse;
 import java.io.IOException;
 import java.io.OutputStream;
-import java.io.PrintWriter;
-import java.io.StringWriter;
 import java.net.URI;
 import java.nio.charset.StandardCharsets;
 import java.util.Collections;
@@ -92,26 +90,23 @@ public HttpResponse getResponse() {
 
   @Override
   public void handleException(IOException e) throws IOException {
-    sendErrorResponseWithStackTrace(e);
+    sendErrorResponse(e);
   }
 
   @Override
   public void handleException(RuntimeException e) {
-    sendErrorResponseWithStackTrace(e);
+    sendErrorResponse(e);
   }
 
-  private void sendErrorResponseWithStackTrace(Exception requestHandlerException) {
+  private void sendErrorResponse(Exception requestHandlerException) {
     if (!responseSent) {
       responseSent = true;
       try {
-        StringWriter stringWriter = new StringWriter();
-        PrintWriter printWriter = new PrintWriter(stringWriter);
-        printWriter.write("An Exception occurred while scraping metrics: ");
-        requestHandlerException.printStackTrace(new PrintWriter(printWriter));
-        byte[] stackTrace = stringWriter.toString().getBytes(StandardCharsets.UTF_8);
+        byte[] message =
+            "An Exception occurred while scraping metrics.".getBytes(StandardCharsets.UTF_8);
         httpExchange.getResponseHeaders().set("Content-Type", "text/plain; charset=utf-8");
-        httpExchange.sendResponseHeaders(500, stackTrace.length);
-        httpExchange.getResponseBody().write(stackTrace);
+        httpExchange.sendResponseHeaders(500, message.length);
+        httpExchange.getResponseBody().write(message);
       } catch (IOException errorWriterException) {
         // We want to avoid logging so that we don't mess with application logs when the HTTPServer
         // is used in a Java agent.

prometheus-metrics-exporter-httpserver/src/test/java/io/prometheus/metrics/exporter/httpserver/HTTPServerTest.java

@@ -171,7 +171,8 @@ public MetricSnapshots scrape(PrometheusScrapeRequest scrapeRequest) {
                   }
                 })
             .buildAndStart();
-    run(server, "/metrics", 500, "An Exception occurred while scraping metrics");
+    String body = run(server, "/metrics", 500, "An Exception occurred while scraping metrics");
+    assertThat(body).doesNotContain("test");
   }
 
   @Test
@@ -234,7 +235,7 @@ void healthDisabled() throws Exception {
         "");
   }
 
-  private static void run(
+  private static String run(
       HTTPServer server, String path, int expectedStatusCode, String expectedBody)
       throws Exception {
     // we cannot use try-with-resources or even client.close(), or the test will fail with Java 17
@@ -248,6 +249,7 @@ private static void run(
           client.send(request, HttpResponse.BodyHandlers.ofString());
       assertThat(response.statusCode()).isEqualTo(expectedStatusCode);
       assertThat(response.body()).contains(expectedBody);
+      return response.body();
     } finally {
       server.stop();
     }