fix(feature-flags): redact agentless base URL telemetry and reject malformed sites safely

Author: pavlokhrebto

tracer/src/Datadog.Trace/FeatureFlags/Agentless/AgentlessEndpoint.cs

@@ -72,13 +72,25 @@ public static bool TryCreate(string? site, string? env, string? baseUrl, out Age
                 return false;
             }
 
-            var managed = new UriBuilder("https", ManagedHostPrefix + trimmedSite!.ToLowerInvariant()) { Path = DefaultPath };
+            var managedHost = ManagedHostPrefix + trimmedSite!.ToLowerInvariant();
+            if (managedHost.Contains("://") || HasWhitespace(managedHost))
+            {
+                error = "The configured Datadog site is not valid";
+                return false;
+            }
+
+            if (!Uri.TryCreate($"https://{managedHost}{DefaultPath}", UriKind.Absolute, out var managedUri))
+            {
+                error = "The configured Datadog site is not valid";
+                return false;
+            }
+
             if (!StringUtil.IsNullOrEmpty(env))
             {
-                managed.Query = "dd_env=" + Uri.EscapeDataString(env!);
+                managedUri = new UriBuilder(managedUri) { Query = "dd_env=" + Uri.EscapeDataString(env!) }.Uri;
             }
 
-            endpoint = new AgentlessEndpoint(managed.Uri, isManaged: true);
+            endpoint = new AgentlessEndpoint(managedUri, isManaged: true);
             return true;
         }
 
@@ -113,4 +125,17 @@ public static bool TryCreate(string? site, string? env, string? baseUrl, out Age
         endpoint = new AgentlessEndpoint(custom, isManaged: false);
         return true;
     }
+
+    private static bool HasWhitespace(string value)
+    {
+        foreach (var c in value)
+        {
+            if (char.IsWhiteSpace(c))
+            {
+                return true;
+            }
+        }
+
+        return false;
+    }
 }

tracer/src/Datadog.Trace/FeatureFlags/FeatureFlagsSettings.cs

@@ -62,9 +62,10 @@ public FeatureFlagsSettings(IConfigurationSource? source, IConfigurationTelemetr
 
         Source = ResolveSource(enabled, configuredSource, legacyEnabled);
 
-        AgentlessBaseUrl = config
-                          .WithKeys(ConfigurationKeys.FeatureFlags.FeatureFlagsConfigurationSourceAgentlessBaseUrl)
-                          .AsString(url => !StringUtil.IsNullOrEmpty(url?.Trim()));
+        var agentlessBaseUrl = config
+                                .WithKeys(ConfigurationKeys.FeatureFlags.FeatureFlagsConfigurationSourceAgentlessBaseUrl)
+                                .AsRedactedString();
+        AgentlessBaseUrl = !StringUtil.IsNullOrEmpty(agentlessBaseUrl?.Trim()) ? agentlessBaseUrl : null;
 
         PollInterval = TimeSpan.FromSeconds(
             InRangeOrDefault(

tracer/test/Datadog.Trace.Tests/FeatureFlags/AgentlessEndpointTests.cs

@@ -104,6 +104,17 @@ public void RejectsWhitespaceOnlySiteWithoutBaseUrl()
         error.Should().Be("No Datadog site is configured");
     }
 
+    [Theory]
+    [InlineData("https://datadoghq.com")] // user accidentally includes the scheme
+    [InlineData("data dog hq.com")] // internal spaces
+    [InlineData("datadoghq.com:99999")] // invalid port
+    public void RejectsMalformedSiteWithoutThrowing(string site)
+    {
+        AgentlessEndpoint.TryCreate(site, env: null, baseUrl: null, out var endpoint, out var error)
+            .Should().BeFalse();
+        error.Should().Be("The configured Datadog site is not valid");
+    }
+
     [Fact]
     public void ErrorNeverContainsUrl()
     {