From 42610b9d5a95ec108b74ffbc6446542cf6b0176a Mon Sep 17 00:00:00 2001
From: David Kalnischkies <david@kalnischkies.de>
Date: Wed, 29 Jun 2016 10:16:14 +0200
Subject: if conf unset, don't read / as conf/pref/sources dir

Usually these config options are set to sensible values, but if init
isn't run or the user interferes with configuration clearing or similar
the options could indeed carry an empty value, which will result in
FindDir returning a '/'. That feels kinda wrong, but as a public
interface there isn't much we can do about it and instead make it so
that we get the special file /dev/null back we know how to deal with in
such cases.
---
 apt-pkg/init.cc       | 7 ++++---
 apt-pkg/policy.cc     | 4 ++--
 apt-pkg/sourcelist.cc | 9 +++++----
 3 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/apt-pkg/init.cc b/apt-pkg/init.cc
index 9543ca7e8..fa679e6c6 100644
--- a/apt-pkg/init.cc
+++ b/apt-pkg/init.cc
@@ -15,6 +15,7 @@
 #include <apt-pkg/error.h>
 #include <apt-pkg/pkgsystem.h>
 #include <apt-pkg/configuration.h>
+#include <apt-pkg/strutl.h>
 #include <apt-pkg/macros.h>
 
 #include <string.h>
@@ -134,14 +135,14 @@ bool pkgInitConfig(Configuration &Cnf)
    }
 
    // Read the configuration parts dir
-   std::string Parts = Cnf.FindDir("Dir::Etc::parts");
+   std::string const Parts = Cnf.FindDir("Dir::Etc::parts", "/dev/null");
    if (DirectoryExists(Parts) == true)
       Res &= ReadConfigDir(Cnf,Parts);
-   else
+   else if (APT::String::Endswith(Parts, "/dev/null") == false)
       _error->WarningE("DirectoryExists",_("Unable to read %s"),Parts.c_str());
 
    // Read the main config file
-   std::string FName = Cnf.FindFile("Dir::Etc::main");
+   std::string const FName = Cnf.FindFile("Dir::Etc::main", "/dev/null");
    if (RealFileExists(FName) == true)
       Res &= ReadConfigFile(Cnf,FName);
 
diff --git a/apt-pkg/policy.cc b/apt-pkg/policy.cc
index 2bdd96d8c..ff59fb0ac 100644
--- a/apt-pkg/policy.cc
+++ b/apt-pkg/policy.cc
@@ -307,11 +307,11 @@ APT_PURE signed short pkgPolicy::GetPriority(pkgCache::PkgFileIterator const &Fi
 bool ReadPinDir(pkgPolicy &Plcy,string Dir)
 {
    if (Dir.empty() == true)
-      Dir = _config->FindDir("Dir::Etc::PreferencesParts");
+      Dir = _config->FindDir("Dir::Etc::PreferencesParts", "/dev/null");
 
    if (DirectoryExists(Dir) == false)
    {
-      if (Dir != "/dev/null")
+      if (APT::String::Endswith(Dir, "/dev/null") == false)
 	 _error->WarningE("DirectoryExists",_("Unable to read %s"),Dir.c_str());
       return true;
    }
diff --git a/apt-pkg/sourcelist.cc b/apt-pkg/sourcelist.cc
index afbf3e665..022aff2fe 100644
--- a/apt-pkg/sourcelist.cc
+++ b/apt-pkg/sourcelist.cc
@@ -311,18 +311,19 @@ bool pkgSourceList::ReadMainList()
    Reset();
    // CNC:2003-11-28 - Entries in sources.list have priority over
    //                  entries in sources.list.d.
-   string Main = _config->FindFile("Dir::Etc::sourcelist");
-   string Parts = _config->FindDir("Dir::Etc::sourceparts");
+   string Main = _config->FindFile("Dir::Etc::sourcelist", "/dev/null");
+   string Parts = _config->FindDir("Dir::Etc::sourceparts", "/dev/null");
    
    if (RealFileExists(Main) == true)
       Res &= ReadAppend(Main);
-   else if (DirectoryExists(Parts) == false)
+   else if (DirectoryExists(Parts) == false && APT::String::Endswith(Parts, "/dev/null") == false)
       // Only warn if there are no sources.list.d.
       _error->WarningE("DirectoryExists", _("Unable to read %s"), Parts.c_str());
 
    if (DirectoryExists(Parts) == true)
       Res &= ReadSourceDir(Parts);
-   else if (RealFileExists(Main) == false)
+   else if (Main.empty() == false && RealFileExists(Main) == false &&
+	 APT::String::Endswith(Parts, "/dev/null") == false)
       // Only warn if there is no sources.list file.
       _error->WarningE("RealFileExists", _("Unable to read %s"), Main.c_str());
 
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