Fix the usage of proxies which require authentication (#140)

If the configured HTTP proxy requires basic authentication then the Username and Password
which are configured on the "Advanced" section in "Manage Plugins" section are not used
to route traffic. This leads to HTTP 407 error when trying to connect to the Github or
enterprise Git domain.

This commit ensures that if the username and proxy are configured for the currently configured
HTTP_PROXY that these are also used. The solution has been manually tested, but no unit tests
have been provided.

This commit fixes [JENKINS-67383]

Co-authored-by: Vanio Begic <[email protected]>

src/main/java/org/jenkinsci/plugins/GithubSecurityRealm.java

@@ -57,10 +57,15 @@ of this software and associated documentation files (the "Software"), to deal
 import org.apache.commons.lang.builder.HashCodeBuilder;
 import org.apache.http.HttpEntity;
 import org.apache.http.HttpHost;
+import org.apache.http.auth.AuthScope;
+import org.apache.http.auth.UsernamePasswordCredentials;
+import org.apache.http.client.CredentialsProvider;
 import org.apache.http.client.config.RequestConfig;
 import org.apache.http.client.methods.HttpPost;
 import org.apache.http.client.methods.HttpUriRequest;
+import org.apache.http.impl.client.BasicCredentialsProvider;
 import org.apache.http.impl.client.CloseableHttpClient;
+import org.apache.http.impl.client.HttpClientBuilder;
 import org.apache.http.impl.client.HttpClients;
 import org.apache.http.util.EntityUtils;
 import org.kohsuke.github.GHEmail;
@@ -448,15 +453,11 @@ public HttpResponse doFinishLogin(StaplerRequest request)
     @Nullable
     private String getAccessToken(@NonNull String code) throws IOException {
         String content;
-        try (CloseableHttpClient httpClient = HttpClients.createDefault()) {
-            HttpPost httpost = new HttpPost(githubWebUri
-                    + "/login/oauth/access_token?" + "client_id=" + clientID + "&"
-                    + "client_secret=" + clientSecret.getPlainText() + "&" + "code=" + code);
-            HttpHost proxy = getProxy(httpost);
-            if (proxy != null) {
-                RequestConfig requestConfig = RequestConfig.custom().setProxy(proxy).build();
-                httpost.setConfig(requestConfig);
-            }
+        HttpPost httpost = new HttpPost(githubWebUri
+                + "/login/oauth/access_token?" + "client_id=" + clientID + "&"
+                + "client_secret=" + clientSecret.getPlainText() + "&" + "code=" + code);
+
+        try (CloseableHttpClient httpClient = configureClientWithProxy(httpost)) {
             org.apache.http.HttpResponse response = httpClient.execute(httpost);
             HttpEntity entity = response.getEntity();
             content = EntityUtils.toString(entity);
@@ -472,6 +473,35 @@ private String getAccessToken(@NonNull String code) throws IOException {
         return null;
     }
 
+    private CloseableHttpClient configureClientWithProxy(HttpPost postLocation) {
+        ProxyConfiguration proxyConfiguration = Jenkins.get().proxy;
+
+        if (proxyConfiguration == null) return HttpClients.createDefault();
+
+        HttpHost proxyHost = getProxy(proxyConfiguration, postLocation.getURI().getHost());
+
+        HttpClientBuilder httpClientBuilder = HttpClients.custom();
+
+        if (proxyHost != null) {
+            RequestConfig requestConfig = RequestConfig.custom()
+                    .setProxy(proxyHost)
+                    .build();
+
+            postLocation.setConfig(requestConfig);
+
+            if(proxyConfiguration.getUserName() != null && proxyConfiguration.getSecretPassword() != null ) {
+                CredentialsProvider credsProvider = new BasicCredentialsProvider();
+                credsProvider.setCredentials(
+                        new AuthScope(proxyHost.getHostName(), proxyHost.getPort()),
+                        new UsernamePasswordCredentials(proxyConfiguration.getUserName(), proxyConfiguration.getSecretPassword().getPlainText()));
+                httpClientBuilder.setDefaultCredentialsProvider(credsProvider);
+            }
+        }
+
+        return httpClientBuilder.build();
+    }
+
+
     /**
      * Generates a random URL Safe String of n characters
      */
@@ -490,11 +520,8 @@ private String getSecureRandomString(int n) {
     /**
      * Returns the proxy to be used when connecting to the given URI.
      */
-    private HttpHost getProxy(HttpUriRequest method) {
-        ProxyConfiguration proxy = Jenkins.get().proxy;
-        if (proxy==null)    return null;    // defensive check
-
-        Proxy p = proxy.createProxy(method.getURI().getHost());
+    private HttpHost getProxy(ProxyConfiguration proxy, String host) {
+        Proxy p = proxy.createProxy(host);
         switch (p.type()) {
         case DIRECT:
             return null;        // no proxy