show warnings instead of errors if files are unreadable

We used to fail on unreadable config/preferences/sources files, but at
least for sources we didn't in the past and it seems harsh to refuse to
work because of a single file, especially as the error messages are
inconsistent and end up being silly (like suggesting to run apt update
to fix the problem…).

LP: #1701852

3 files changed, 16 insertions, 9 deletions

diff --git a/apt-pkg/contrib/configuration.cc b/apt-pkg/contrib/configuration.cc
index 65242bec5..eb873bdba 100644
--- a/apt-pkg/contrib/configuration.cc
+++ b/apt-pkg/contrib/configuration.cc
@@ -1150,13 +1150,10 @@ bool ReadConfigFile(Configuration &Conf,const string &FName,bool const &AsSectio
 bool ReadConfigDir(Configuration &Conf,const string &Dir,
 		   bool const &AsSectional, unsigned const &Depth)
 {
-   vector<string> const List = GetListOfFilesInDir(Dir, "conf", true, true);
-
-   // Read the files
-   for (vector<string>::const_iterator I = List.begin(); I != List.end(); ++I)
-      if (ReadConfigFile(Conf,*I,AsSectional,Depth) == false)
-	 return false;
-   return true;
+   bool good = true;
+   for (auto const &I : GetListOfFilesInDir(Dir, "conf", true, true))
+      good = ReadConfigFile(Conf, I, AsSectional, Depth) && good;
+   return good;
 }
 									/*}}}*/
 // MatchAgainstConfig Constructor					/*{{{*/
diff --git a/apt-pkg/contrib/fileutl.cc b/apt-pkg/contrib/fileutl.cc
index 7633b07ef..33f4f7e09 100644
--- a/apt-pkg/contrib/fileutl.cc
+++ b/apt-pkg/contrib/fileutl.cc
@@ -402,7 +402,10 @@ std::vector<string> GetListOfFilesInDir(string const &Dir, std::vector<string> c
    DIR *D = opendir(Dir.c_str());
    if (D == 0) 
    {
-      _error->Errno("opendir",_("Unable to read %s"),Dir.c_str());
+      if (errno == EACCES)
+	 _error->WarningE("opendir", _("Unable to read %s"), Dir.c_str());
+      else
+	 _error->Errno("opendir", _("Unable to read %s"), Dir.c_str());
       return List;
    }
 
@@ -3126,7 +3129,13 @@ bool DropPrivileges()							/*{{{*/
 									/*}}}*/
 bool OpenConfigurationFileFd(std::string const &File, FileFd &Fd) /*{{{*/
 {
+   int const fd = open(File.c_str(), O_RDONLY | O_CLOEXEC | O_NOCTTY);
+   if (fd == -1)
+      return _error->WarningE("open", _("Unable to read %s"), File.c_str());
    APT::Configuration::Compressor none(".", "", "", nullptr, nullptr, 0);
-   return Fd.Open(File, FileFd::ReadOnly, none);
+   if (Fd.OpenDescriptor(fd, FileFd::ReadOnly, none) == false)
+      return false;
+   Fd.SetFileName(File);
+   return true;
 }
 									/*}}}*/
diff --git a/apt-pkg/contrib/fileutl.h b/apt-pkg/contrib/fileutl.h
index 06c303809..19b4ed49e 100644
--- a/apt-pkg/contrib/fileutl.h
+++ b/apt-pkg/contrib/fileutl.h
@@ -161,6 +161,7 @@ class FileFd
    inline bool Eof() {return (Flags & HitEof) == HitEof;};
    inline bool IsCompressed() {return (Flags & Compressed) == Compressed;};
    inline std::string &Name() {return FileName;};
+   inline void SetFileName(std::string const &name) { FileName = name; };
 
    FileFd(std::string FileName,unsigned int const Mode,unsigned long AccessMode = 0666);
    FileFd(std::string FileName,unsigned int const Mode, CompressMode Compress, unsigned long AccessMode = 0666);