C#: Set proxy environment variables, if Dependabot proxy is detected

csharp/extractor/Semmle.Extraction.CSharp.DependencyFetching/DependabotProxy.cs

@@ -0,0 +1,67 @@
+using System;
+using System.Diagnostics;
+using System.IO;
+using Semmle.Util;
+using Semmle.Util.Logging;
+
+namespace Semmle.Extraction.CSharp.DependencyFetching
+{
+    internal class DependabotProxy
+    {
+        private readonly string? host;
+        private readonly string? port;
+        private readonly FileInfo? certFile;
+
+        /// <summary>
+        /// The full address of the Dependabot proxy, if available.
+        /// </summary>
+        internal readonly string? Address;
+
+        /// <summary>
+        /// Gets a value indicating whether a Dependabot proxy is configured.
+        /// </summary>
+        internal bool IsConfigured => !string.IsNullOrEmpty(this.Address);
+
+        internal DependabotProxy(TemporaryDirectory tempWorkingDirectory)
+        {
+            // Obtain and store the address of the Dependabot proxy, if available.
+            this.host = Environment.GetEnvironmentVariable(EnvironmentVariableNames.ProxyHost);
+            this.port = Environment.GetEnvironmentVariable(EnvironmentVariableNames.ProxyPort);
+
+            if (string.IsNullOrWhiteSpace(host) || string.IsNullOrWhiteSpace(port))
+            {
+                return;
+            }
+
+            this.Address = $"http://{this.host}:{this.port}";
+
+            // Obtain and store the proxy's certificate, if available.
+            var cert = Environment.GetEnvironmentVariable(EnvironmentVariableNames.ProxyCertificate);
+
+            if (string.IsNullOrWhiteSpace(cert))
+            {
+                return;
+            }
+
+            var certDirPath = new DirectoryInfo(Path.Join(tempWorkingDirectory.DirInfo.FullName, ".dependabot-proxy"));
+            Directory.CreateDirectory(certDirPath.FullName);
+
+            this.certFile = new FileInfo(Path.Join(certDirPath.FullName, "proxy.crt"));
+
+            using var writer = this.certFile.CreateText();
+            writer.Write(cert);
+        }
+
+        internal void ApplyProxy(ILogger logger, ProcessStartInfo startInfo)
+        {
+            // If the proxy isn't configured, we have nothing to do.
+            if (!this.IsConfigured) return;
+
+            logger.LogInfo($"Setting up Dependabot proxy at {this.Address}");
+
+            startInfo.EnvironmentVariables["HTTP_PROXY"] = this.Address;
+            startInfo.EnvironmentVariables["HTTPS_PROXY"] = this.Address;
+            startInfo.EnvironmentVariables["SSL_CERT_FILE"] = this.certFile?.FullName;
+        }
+    }
+}

csharp/extractor/Semmle.Extraction.CSharp.DependencyFetching/DotNet.cs

@@ -27,7 +27,7 @@ private DotNet(IDotNetCliInvoker dotnetCliInvoker, ILogger logger, TemporaryDire
             Info();
         }
 
-        private DotNet(ILogger logger, string? dotNetPath, TemporaryDirectory tempWorkingDirectory) : this(new DotNetCliInvoker(logger, Path.Combine(dotNetPath ?? string.Empty, "dotnet")), logger, tempWorkingDirectory) { }
+        private DotNet(ILogger logger, string? dotNetPath, TemporaryDirectory tempWorkingDirectory) : this(new DotNetCliInvoker(logger, Path.Combine(dotNetPath ?? string.Empty, "dotnet"), tempWorkingDirectory), logger, tempWorkingDirectory) { }
 
         internal static IDotNet Make(IDotNetCliInvoker dotnetCliInvoker, ILogger logger) => new DotNet(dotnetCliInvoker, logger);
 

csharp/extractor/Semmle.Extraction.CSharp.DependencyFetching/DotNetCliInvoker.cs

@@ -12,12 +12,14 @@ namespace Semmle.Extraction.CSharp.DependencyFetching
     internal sealed class DotNetCliInvoker : IDotNetCliInvoker
     {
         private readonly ILogger logger;
+        private readonly DependabotProxy proxy;
 
         public string Exec { get; }
 
-        public DotNetCliInvoker(ILogger logger, string exec)
+        public DotNetCliInvoker(ILogger logger, string exec, TemporaryDirectory tempWorkingDirectory)
         {
             this.logger = logger;
+            this.proxy = new DependabotProxy(tempWorkingDirectory);
             this.Exec = exec;
             logger.LogInfo($"Using .NET CLI executable: '{Exec}'");
         }
@@ -38,6 +40,10 @@ private ProcessStartInfo MakeDotnetStartInfo(string args, string? workingDirecto
             startInfo.EnvironmentVariables["DOTNET_CLI_UI_LANGUAGE"] = "en";
             startInfo.EnvironmentVariables["MSBUILDDISABLENODEREUSE"] = "1";
             startInfo.EnvironmentVariables["DOTNET_SKIP_FIRST_TIME_EXPERIENCE"] = "true";
+
+            // Configure the proxy settings, if applicable.
+            this.proxy.ApplyProxy(this.logger, startInfo);
+
             return startInfo;
         }
 

csharp/extractor/Semmle.Extraction.CSharp.DependencyFetching/EnvironmentVariableNames.cs

@@ -74,5 +74,20 @@ internal static class EnvironmentVariableNames
         /// Specifies the location of the diagnostic directory.
         /// </summary>
         public const string DiagnosticDir = "CODEQL_EXTRACTOR_CSHARP_DIAGNOSTIC_DIR";
+
+        /// <summary>
+        /// Specifies the hostname of the Dependabot proxy.
+        /// </summary>
+        public const string ProxyHost = "CODEQL_PROXY_HOST";
+
+        /// <summary>
+        /// Specifies the hostname of the Dependabot proxy.
+        /// </summary>
+        public const string ProxyPort = "CODEQL_PROXY_PORT";
+
+        /// <summary>
+        /// Contains the certificate used by the Dependabot proxy.
+        /// </summary>
+        public const string ProxyCertificate = "CODEQL_PROXY_CA_CERTIFICATE";
     }
 }