Modified RobustNetworkOperation to send a UserAgent string

CHANGELOG.md

@@ -23,6 +23,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - [SIL.Core.Clearshare] New methods "GetIsStringAvailableForLangId" and "GetDynamicStringOrEnglish" were added to Localizer for use in LicenseInfo's "GetBestLicenseTranslation" method, to remove LicenseInfo's L10NSharp dependency.
 - [SIL.Windows.Forms.Clearshare] New ILicenseWithImage interface handles "GetImage" method for Winforms-dependent licenses, implemented in CreativeCommonsLicense and CustomLicense, and formerly included in LicenseInfo.
 - [SIL.Core.Clearshare] New tests MetadataBareTests are based on previous MetadataTests in SIL.Windows.Forms.Clearshare. The tests were updated to use ImageSharp instead of Winforms for handling images.
+- [SIL.Core.Desktop] Added a constant (kBrowserCompatibleUserAgent) to RobustNetworkOperation: a browser-like User Agent string that can be used when making HTTP requests to strict servers.
 
 ### Fixed
 - [SIL.DictionaryServices] Fix memory leak in LiftWriter
@@ -49,6 +50,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - [SIL.Windows.Forms] BREAKING CHANGE: ToolStripExtensions.InitializeWithAvailableUILocales() removed the ILocalizationManager parameter. This method no longer provides functionality to display the localization dialog box in response to the user clicking More.
 - [SIL.Windows.Forms] BREAKING CHANGE: Removed optional moreSelected parameter from ToolStripExtensions.InitializeWithAvailableUILocales method. This parameter was no longer being used. Clients that want to have a More menu item that performs a custom action will now need to add it themselves.
 - [SIL.Windows.Forms] BREAKING CHANGE: LocalizationIncompleteDlg's EmailAddressForLocalizationRequests is no longer autopopulated from LocalizationManager. A new optional constructor parameter, emailAddressForLocalizationRequests, can be used instead. If not supplied, the "More information" controls will be hidden.
+- [SIL.Core.Desktop] Added an optional userAgentHeader parameter to DoHttpGetAndGetProxyInfo to allow a client to mimic a real browser if necessary.
 
 ### Removed
 - [SIL.Windows.Forms] In .NET 8 builds, removed Scanner and Camera options from the Image Toolbox.

SIL.Core.Desktop.Tests/Network/RobustNetworkOperation.Tests.cs

@@ -1,4 +1,4 @@
-using System.Diagnostics;
+using System.Diagnostics;
 using NUnit.Framework;
 using SIL.Network;
 
@@ -19,7 +19,8 @@ public void DoHttpGetAndGetProxyInfo_404()
 		public void DoHttpGetAndGetProxyInfo_NoProxy_ReturnsFalse()
 		{
 			var gotProxy = RobustNetworkOperation.DoHttpGetAndGetProxyInfo(
-				"https://sil.org/", out _, out _, out _, s => Debug.WriteLine(s));
+				"https://sil.org/", out _, out _, out _, s => Debug.WriteLine(s),
+				RobustNetworkOperation.kBrowserCompatibleUserAgent);
 			Assert.That(gotProxy, Is.False);
 		}
 	}

SIL.Core.Desktop/Network/RobustNetworkOperation.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Net;
 using System.Security.Cryptography;
 using System.Text;
@@ -8,6 +8,14 @@ namespace SIL.Network
 
 	public class RobustNetworkOperation
 	{
+		/// <summary>
+		/// A browser-like User Agent string that can be used when making HTTP requests to servers
+		/// that reject requests lacking a typical browser User-Agent header. Used in tests and
+		/// available to callers that encounter 403 responses due to restrictive server filtering.
+		/// </summary>
+		public const string kBrowserCompatibleUserAgent =
+			"Mozilla/5.0 (Windows NT 10.0; Win64; x64) libpalaso";
+
 		/// <summary>
 		/// Perform a web action, trying various things to use a proxy if needed, including requesting
 		/// (and remembering) user credentials from the user.
@@ -22,7 +30,7 @@ public static IWebProxy Do(Action<IWebProxy> action, Action<string> verboseLog)
 			var proxy = new WebProxy();
 			action(proxy);
 
-			//!!!!!!!!!!!!!! in Sept 2011, hatton disabled proxy lookup. It was reportedly causing grief in Nigeria,
+			//!!!!!!!!!!!!!! in Sept 2011, Hatton disabled proxy lookup. It was reportedly causing grief in Nigeria,
 			//asking for credentials over and over, and SIL PNG doesn't use a proxy anymore. So for now...
 
 
@@ -109,10 +117,51 @@ public static string GetClearText(string encryptedString)
 		}
 
 		/// <summary>
-		/// Used by Chorus to get proxy name, user name, and password of the remote repository.
+		/// Used to determine whether an HTTP GET request requires a proxy and, if so, to retrieve
+		/// the proxy host and credentials needed to access the specified remote repository URL.
 		/// </summary>
-		/// <returns>true if a proxy is needed. THROWS if it just can't get through</returns>
-		public static bool DoHttpGetAndGetProxyInfo(string url, out string hostAndPort, out string userName, out string password, Action<string> verboseLog)
+		/// <param name="url">
+		/// The full URL to send an HTTP GET request to. Used to test connectivity and determine
+		/// whether proxy credentials are required.
+		/// </param>
+		/// <param name="hostAndPort">
+		/// Outputs the proxy host (including port, if applicable) if a proxy is required;
+		/// otherwise, an empty string.
+		/// </param>
+		/// <param name="userName">
+		/// Outputs the proxy username if authentication is required; otherwise an empty string.
+		/// </param>
+		/// <param name="password">
+		/// Outputs the proxy password if authentication is required; otherwise an empty string.
+		/// </param>
+		/// <param name="verboseLog">
+		/// Optional callback for logging diagnostic information about the request and proxy
+		/// detection process.
+		/// </param>
+		/// <param name="userAgentHeader">
+		/// Optional user agent header string to send with the request. Some servers require a
+		/// browser-like user agent and may reject requests that appear to come from automated
+		/// clients. See <see cref="kBrowserCompatibleUserAgent"/> for an example value.
+		/// </param>
+		/// <returns>
+		/// True if a proxy is required and credentials were obtained; false if no proxy is needed.
+		/// </returns>
+		/// <exception cref="ArgumentNullException">
+		/// Thrown if <paramref name="url"/> is null.
+		/// </exception>
+		/// <exception cref="UriFormatException">
+		/// Thrown if <paramref name="url"/> is not a valid URI.
+		/// </exception>
+		/// <exception cref="WebException">
+		/// Thrown if the HTTP request fails due to network errors, proxy configuration
+		/// issues, or authentication failures.
+		/// </exception>
+		/// <exception cref="NotSupportedException">
+		/// Thrown if the URI scheme is not supported.
+		/// </exception>
+		public static bool DoHttpGetAndGetProxyInfo(string url, out string hostAndPort,
+			out string userName, out string password, Action<string> verboseLog,
+			string userAgentHeader = null)
 		{
 			hostAndPort = string.Empty;
 			userName = string.Empty;
@@ -125,6 +174,8 @@ public static bool DoHttpGetAndGetProxyInfo(string url, out string hostAndPort,
 				proxy =>
 				{
 					client.Proxy = proxy;
+					if (userAgentHeader != null)
+						client.Headers[HttpRequestHeader.UserAgent] = userAgentHeader;
 					client.DownloadData(url);
 					//we don't actually care what comes back
 				}, verboseLog
@@ -150,9 +201,7 @@ public static bool DoHttpGetAndGetProxyInfo(string url, out string hostAndPort,
 			var networkCredential = proxyInfo.Credentials.GetCredential(destination, "");
 			userName = networkCredential.UserName;
 			password = networkCredential.Password;
-			if (verboseLog != null)
-				verboseLog.Invoke("DoHttpGetAndGetProxyInfo Returning with credentials. UserName is " + userName);
-
+			verboseLog?.Invoke("DoHttpGetAndGetProxyInfo Returning with credentials. UserName is " + userName);
 
 			return true;
 		}