fix(api): mask access token in Payload.toString()

rollbar-api/src/main/java/com/rollbar/api/payload/Payload.java

@@ -16,6 +16,10 @@ public class Payload implements JsonSerializable, StringTruncatable<Payload> {
 
   private static final long serialVersionUID = 3054041443735286159L;
 
+  private static final String TOKEN_MASK = "****";
+
+  private static final int UNMASKED_TOKEN_SUFFIX_LENGTH = 4;
+
   private final String accessToken;
 
   private final Data data;
@@ -86,11 +90,26 @@ public int hashCode() {
   @Override
   public String toString() {
     return "Payload{"
-        + "accessToken='" + accessToken + '\''
+        + "accessToken=" + maskAccessToken(accessToken)
         + ", data=" + data
         + '}';
   }
 
+  /**
+   * Masks the token so it never ends up in logs. Keeps the last characters of long enough tokens
+   * so a misconfigured token can still be told apart from the right one.
+   */
+  private static String maskAccessToken(String accessToken) {
+    if (accessToken == null) {
+      return "null";
+    }
+    if (accessToken.length() <= UNMASKED_TOKEN_SUFFIX_LENGTH * 2) {
+      return "'" + TOKEN_MASK + "'";
+    }
+    return "'" + TOKEN_MASK
+        + accessToken.substring(accessToken.length() - UNMASKED_TOKEN_SUFFIX_LENGTH) + "'";
+  }
+
   @Override
   public Map<String, Object> asJson() {
     Map<String, Object> values = new HashMap<>();

rollbar-api/src/test/java/com/rollbar/api/payload/PayloadTest.java

@@ -1,6 +1,8 @@
 package com.rollbar.api.payload;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
 
 import com.rollbar.api.payload.data.Data;
 import java.util.HashMap;
@@ -53,6 +55,40 @@ public void shouldReturnAsJson() {
     assertEquals(expected, payload.asJson());
   }
 
+  @Test
+  public void toStringShouldNotContainAccessToken() {
+    Payload payload = new Payload.Builder()
+        .accessToken(ACCESS_TOKEN)
+        .data(DATA)
+        .build();
+
+    String result = payload.toString();
+
+    assertFalse(result.contains(ACCESS_TOKEN));
+    assertTrue(result.contains("accessToken='****ddsf'"));
+  }
+
+  @Test
+  public void toStringShouldFullyMaskShortAccessToken() {
+    Payload payload = new Payload.Builder()
+        .accessToken("abcd1234")
+        .build();
+
+    String result = payload.toString();
+
+    assertFalse(result.contains("1234"));
+    assertTrue(result.contains("accessToken='****'"));
+  }
+
+  @Test
+  public void toStringShouldHandleNullAccessToken() {
+    Payload payload = new Payload.Builder()
+        .data(DATA)
+        .build();
+
+    assertTrue(payload.toString().contains("accessToken=null"));
+  }
+
   @Test
   public void shouldReturnJsonAsJson() {
     String json = "{\"foo\":\"bar\"}";