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.

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);
    }
 

test/integration/test-apt-https-no-redirect

@@ -14,6 +14,7 @@ echo 'alright' > aptarchive/working
 changetohttpswebserver
 webserverconfig 'aptwebserver::redirect::replace::/redirectme/' "http://localhost:${APTHTTPPORT}/"
 webserverconfig 'aptwebserver::redirect::replace::/redirectme2/' "https://localhost:${APTHTTPSPORT}/"
+echo 'Dir::Bin::Methods::https+http "https";' > rootdir/etc/apt/apt.conf.d/99add-https-http-method
 
 msgtest 'download of a file works via' 'http'
 testsuccess --nomsg downloadfile "http://localhost:${APTHTTPPORT}/working" httpfile
@@ -22,9 +23,23 @@ testfileequal httpfile 'alright'
 msgtest 'download of a file works via' 'https'
 testsuccess --nomsg downloadfile "https://localhost:${APTHTTPSPORT}/working" httpsfile
 testfileequal httpsfile 'alright'
+rm -f httpfile httpsfile
+
+msgtest 'download of http file works via' 'https+http'
+testsuccess --nomsg downloadfile "http://localhost:${APTHTTPPORT}/working" httpfile
+testfileequal httpfile 'alright'
+
+msgtest 'download of https file works via' 'https+http'
+testsuccess --nomsg downloadfile "https://localhost:${APTHTTPSPORT}/working" httpsfile
+testfileequal httpsfile 'alright'
+rm -f httpfile httpsfile
 
 msgtest 'download of a file does not work if' 'https redirected to http'
 testfailure --nomsg downloadfile "https://localhost:${APTHTTPSPORT}/redirectme/working" redirectfile
 
 msgtest 'libcurl has forbidden access in last request to' 'http resource'
 testsuccess --nomsg grep -q -E -- "Redirection from https to 'http://.*' is forbidden" rootdir/tmp/testfailure.output
+
+msgtest 'download of a file does work if' 'https+http redirected to https'
+testsuccess --nomsg downloadfile "https+http://localhost:${APTHTTPPORT}/redirectme2/working" redirectfile
+testfileequal redirectfile 'alright'

test/integration/test-apt-update-failure-propagation

@@ -27,10 +27,11 @@ for FILE in rootdir/etc/apt/sources.list.d/*-sid-* ; do
 done
 
 pretest() {
+	msgmsg "$@"
 	rm -rf rootdir/var/lib/apt/lists
 	testsuccessequal 'N: Unable to locate package foo' aptcache policy foo
 }
-pretest
+pretest 'initialize test' 'update'
 testsuccess aptget update
 testsuccessequal "foo:
   Installed: (none)
@@ -41,7 +42,7 @@ testsuccessequal "foo:
      1 500
         500 https://localhost:${APTHTTPSPORT} stable/main all Packages" aptcache policy foo
 
-pretest
+pretest 'not found' 'release files'
 mv aptarchive/dists/stable aptarchive/dists/stable.good
 testfailuremsg "E: The repository 'https://localhost:${APTHTTPSPORT} stable Release' does not have a Release file.
 N: Updating from such a repository can't be done securely, and is therefore disabled by default.
@@ -76,7 +77,16 @@ posttest() {
 }
 posttest
 
-pretest
+pretest 'method disabled' 'https'
+echo 'Dir::Bin::Methods::https "false";' > rootdir/etc/apt/apt.conf.d/99disable-https
+testfailuremsg "E: The method 'https' is explicitly disabled via configuration.
+N: If you meant to use Tor remember to use tor+https instead of https.
+E: Failed to fetch https://localhost:${APTHTTPSPORT}/dists/stable/InRelease  
+E: Some index files failed to download. They have been ignored, or old ones used instead." aptget update
+rm -f rootdir/etc/apt/apt.conf.d/99disable-https
+posttest
+
+pretest 'method not installed' 'https'
 rm "${NEWMETHODS}/https"
 testfailuremsg "E: The method driver ${TMPWORKINGDIRECTORY}/rootdir/usr/lib/apt/methods/https could not be found.
 N: Is the package apt-transport-https installed?
@@ -84,13 +94,12 @@ E: Failed to fetch https://localhost:${APTHTTPSPORT}/dists/stable/InRelease
 E: Some index files failed to download. They have been ignored, or old ones used instead." aptget update
 posttest
 
-ln -s "$OLDMETHODS/https" "$NEWMETHODS"
-pretest
+pretest 'https connection refused' 'doom port'
 for FILE in rootdir/etc/apt/sources.list.d/*-stable-* ; do
 	# lets see how many testservers run also Doom
 	sed -i -e "s#:${APTHTTPSPORT}/#:666/#" "$FILE"
 done
-testwarning aptget update
+testwarning aptget update -o Dir::Bin::Methods::https="${OLDMETHODS}/https"
 testequalor2 "W: Failed to fetch https://localhost:666/dists/stable/InRelease  Failed to connect to localhost port 666: Connection refused
 W: Some index files failed to download. They have been ignored, or old ones used instead." "W: Failed to fetch https://localhost:666/dists/stable/InRelease  couldn't connect to host
 W: Some index files failed to download. They have been ignored, or old ones used instead." tail -n 2 rootdir/tmp/testwarning.output

test/integration/test-bug-738785-switch-protocol

@@ -38,28 +38,12 @@ cd - >/dev/null
 testsuccess aptget install apt -y
 testdpkginstalled 'apt'
 
-# install a slowed down file: otherwise its to fast to reproduce combining
-NEWMETHODS="$(readlink -f rootdir)/usr/lib/apt/methods"
-OLDMETHODS="$(readlink -f rootdir/usr/lib/apt/methods)"
-rm "$NEWMETHODS"
-mkdir "$NEWMETHODS"
-backupIFS="$IFS"
-IFS="$(printf "\n\b")"
-for METH in $(find "$OLDMETHODS" -maxdepth 1 ! -type d); do
-	ln -s "$OLDMETHODS/$(basename "$METH")" "$NEWMETHODS"
-done
-IFS="$backupIFS"
-rm "$NEWMETHODS/https"
-
 cd downloaded
-testfailureequal "E: The method driver $(readlink -f './../')/rootdir/usr/lib/apt/methods/https could not be found.
-N: Is the package apt-transport-https installed?" aptget download apt
+testfailureequal "E: The method 'https' is explicitly disabled via configuration.
+N: If you meant to use Tor remember to use tor+https instead of https." aptget download apt -o Dir::Bin::Methods::https=false
 testfailure test -e apt_1.0_all.deb
 cd - >/dev/null
 
-# revert to all methods
-ln -s "$OLDMETHODS/https" "$NEWMETHODS"
-
 # check that downgrades from https to http are not allowed
 webserverconfig 'aptwebserver::support::http' 'true'
 sed -i -e "s#:${APTHTTPPORT}/redirectme#:${APTHTTPSPORT}/downgrademe#" -e 's# http:# https:#' rootdir/etc/apt/sources.list.d/*

test/integration/test-different-methods-for-same-source

@@ -10,21 +10,10 @@ insertpackage 'stable' 'foo' 'all' '1'
 insertsource 'stable' 'foo' 'all' '1'
 setupaptarchive --no-update
 
-# install a slowed down file: otherwise its to fast to reproduce combining
-NEWMETHODS="$(readlink -f rootdir)/usr/lib/apt/methods"
-OLDMETHODS="$(readlink -f rootdir/usr/lib/apt/methods)"
-rm "$NEWMETHODS"
-mkdir "$NEWMETHODS"
-backupIFS="$IFS"
-IFS="$(printf "\n\b")"
-for METH in $(find "$OLDMETHODS" -maxdepth 1 ! -type d); do
-	ln -s "$OLDMETHODS/$(basename "$METH")" "$NEWMETHODS"
-done
-IFS="$backupIFS"
-ln -s "${OLDMETHODS}/http" "${NEWMETHODS}/http-ng"
-
 changetowebserver
 webserverconfig 'aptwebserver::redirect::replace::/redirectme/' "http://localhost:${APTHTTPPORT}/"
+
+echo 'Dir::Bin::Methods::http-ng "http";' > rootdir/etc/apt/apt.conf.d/99add-http-ng-method
 sed -i -e 's# http:# http-ng:#' $(find rootdir/etc/apt/sources.list.d -name '*-deb-src.list')
 
 testsuccess apt update -o Debug::Acquire::http-ng=1