allow methods to be disabled and redirected via config

To prevent accidents like adding http-sources while using tor+http it
can make sense to allow disabling methods. It might even make sense to
allow "redirections" and adding "symlinked" methods via configuration.
This could e.g. allow using different options for certain sources by
adding and configuring a "virtual" new method which picks up the config
based on the name it was called with like e.g. http does if called as
tor+http.

1 files changed, 24 insertions, 7 deletions

diff --git a/apt-pkg/acquire-worker.cc b/apt-pkg/acquire-worker.cc
index 1ee78d070..7a4f8177f 100644
--- a/apt-pkg/acquire-worker.cc
+++ b/apt-pkg/acquire-worker.cc
@@ -93,9 +93,22 @@ pkgAcquire::Worker::~Worker()
 bool pkgAcquire::Worker::Start()
 {
    // Get the method path
-   string Method = _config->FindDir("Dir::Bin::Methods") + Access;
+   constexpr char const * const methodsDir = "Dir::Bin::Methods";
+   std::string const confItem = std::string(methodsDir) + "::" + Access;
+   std::string Method;
+   if (_config->Exists(confItem))
+	 Method = _config->FindFile(confItem.c_str());
+   else
+	 Method = _config->FindDir(methodsDir) + Access;
    if (FileExists(Method) == false)
    {
+      if (flNotDir(Method) == "false")
+      {
+	 _error->Error(_("The method '%s' is explicitly disabled via configuration."), Access.c_str());
+	 if (Access == "http" || Access == "https")
+	    _error->Notice(_("If you meant to use Tor remember to use %s instead of %s."), ("tor+" + Access).c_str(), Access.c_str());
+	 return false;
+      }
       _error->Error(_("The method driver %s could not be found."),Method.c_str());
       std::string const A(Access.cbegin(), std::find(Access.cbegin(), Access.cend(), '+'));
       std::string pkg;
@@ -103,9 +116,15 @@ bool pkgAcquire::Worker::Start()
       _error->Notice(_("Is the package %s installed?"), pkg.c_str());
       return false;
    }
+   std::string const Calling = _config->FindDir(methodsDir) + Access;
 
    if (Debug == true)
-      clog << "Starting method '" << Method << '\'' << endl;
+   {
+      std::clog << "Starting method '" << Calling << "'";
+      if (Calling != Method)
+	 std::clog << " ( via " << Method << " )";
+      std::clog << endl;
+   }
 
    // Create the pipes
    int Pipes[4] = {-1,-1,-1,-1};
@@ -130,11 +149,9 @@ bool pkgAcquire::Worker::Start()
       SetCloseExec(STDIN_FILENO,false);
       SetCloseExec(STDERR_FILENO,false);
 
-      const char *Args[2];
-      Args[0] = Method.c_str();
-      Args[1] = 0;
-      execv(Args[0],(char **)Args);
-      cerr << "Failed to exec method " << Args[0] << endl;
+      const char * const Args[] = { Calling.c_str(), nullptr };
+      execv(Method.c_str() ,const_cast<char **>(Args));
+      std::cerr << "Failed to exec method " << Calling << " ( via " << Method << ")" << endl;
       _exit(100);
    }