Add proxy support in kpm

- Add proxy option to "kpm restore" subcommand
- "kpm restore" uses global proxy (http_proxy env var) by default
- Add support for authenticated proxies

Author: ChengTian

src/Microsoft.Framework.PackageManager/Program.cs

@@ -56,6 +56,8 @@ public int Main(string[] args)
                     CommandOptionType.MultipleValue);
                 var optFallbackSource = c.Option("-f|--fallbacksource <FEED>",
                     "A list of packages sources to use as a fallback", CommandOptionType.MultipleValue);
+                var optProxy = c.Option("-p|--proxy <ADDRESS>", "The HTTP proxy to use when retrieving packages",
+                    CommandOptionType.SingleValue);
                 c.HelpOption("-?|-h|--help");
 
                 c.OnExecute(() =>
@@ -73,6 +75,16 @@ public int Main(string[] args)
                         {
                             command.FallbackSources = optFallbackSource.Values;
                         }
+                        if (optProxy.HasValue())
+                        {
+#if NET45
+                            Environment.SetEnvironmentVariable("http_proxy", optProxy.Value(),
+                                EnvironmentVariableTarget.Process);
+#else
+                            throw new NotImplementedException(
+                                "TODO: \"kpm --proxy\" is not supported on current target framework");
+#endif
+                        }
                         var success = command.ExecuteCommand();
 
                         return success ? 0 : 1;

src/Microsoft.Framework.PackageManager/Restore/NuGet/PackageFeed.cs

@@ -9,6 +9,7 @@
 using System.IO.Compression;
 using System.IO.Packaging;
 using System.Linq;
+using System.Net;
 using System.Net.Http;
 using System.Net.Http.Headers;
 using System.Text;
@@ -44,7 +45,37 @@ public PackageFeed(
             _userName = userName;
             _password = password;
             _report = report;
-            _httpClient = new HttpClient();
+
+            var proxy = Environment.GetEnvironmentVariable("http_proxy");
+            if (string.IsNullOrEmpty(proxy))
+            {
+                _httpClient = new HttpClient();
+            }
+            else
+            {
+                // To use an authenticated proxy, the proxy address should be in the form of
+                // "http://user:[email protected]:8888"
+                var proxyUriBuilder = new UriBuilder(proxy);
+                var webProxy = new WebProxy(proxy);
+                if (string.IsNullOrEmpty(proxyUriBuilder.UserName))
+                {
+                    // If no credentials were specified we use default credentials
+                    webProxy.Credentials = CredentialCache.DefaultCredentials;
+                }
+                else
+                {
+                    ICredentials credentials = new NetworkCredential(proxyUriBuilder.UserName,
+                        proxyUriBuilder.Password);
+                    webProxy.Credentials = credentials;
+                }
+
+                var handler = new HttpClientHandler
+                {
+                    Proxy = webProxy,
+                    UseProxy = true
+                };
+                _httpClient = new HttpClient(handler);
+            }
         }
 
         Dictionary<string, Task<IEnumerable<PackageInfo>>> _cache = new Dictionary<string, Task<IEnumerable<PackageInfo>>>();