allow a method to request auxiliary files

If a method needs a file to operate like e.g. mirror needs to get a list
of mirrors before it can redirect the the actual requests to them. That
could easily be solved by moving the logic into libapt directly, but by
allowing a method to request other methods to do something we can keep
this logic contained in the method and allow e.g. also methods which
perform binary patching or similar things.

Previously they would need to implement their own acquire system inside
the existing one which in all likelyhood will not support the same
features and methods nor operate with similar security compared to what
we have already running 'above' the requesting method. That said, to
avoid methods producing conflicts with "proper" files we are downloading
a new directory is introduced to keep the auxiliary files in.

[The message magic number 351 is a tribute to the german Grundgesetz
article 35 paragraph 1 which defines that all authorities of the
state(s) help each other on request.]

1 files changed, 25 insertions, 15 deletions

diff --git a/apt-pkg/acquire.cc b/apt-pkg/acquire.cc
index aabcb0aba..5fa456ce3 100644
--- a/apt-pkg/acquire.cc
+++ b/apt-pkg/acquire.cc
@@ -78,13 +78,13 @@ void pkgAcquire::Initialize()
 }
 									/*}}}*/
 // Acquire::GetLock - lock directory and prepare for action		/*{{{*/
-static bool SetupAPTPartialDirectory(std::string const &grand, std::string const &parent)
+static bool SetupAPTPartialDirectory(std::string const &grand, std::string const &parent, std::string const &postfix, mode_t const mode)
 {
-   std::string const partial = parent + "partial";
-   mode_t const mode = umask(S_IWGRP | S_IWOTH);
+   std::string const partial = parent + postfix;
+   mode_t const old_umask = umask(S_IWGRP | S_IWOTH);
    bool const creation_fail = (CreateAPTDirectoryIfNeeded(grand, partial) == false &&
 	 CreateAPTDirectoryIfNeeded(parent, partial) == false);
-   umask(mode);
+   umask(old_umask);
    if (creation_fail == true)
       return false;
 
@@ -100,7 +100,7 @@ static bool SetupAPTPartialDirectory(std::string const &grand, std::string const
             _error->WarningE("SetupAPTPartialDirectory", "chown to %s:root of directory %s failed", SandboxUser.c_str(), partial.c_str());
       }
    }
-   if (chmod(partial.c_str(), 0700) != 0)
+   if (chmod(partial.c_str(), mode) != 0)
       _error->WarningE("SetupAPTPartialDirectory", "chmod 0700 of directory %s failed", partial.c_str());
 
    _error->PushToStack();
@@ -117,10 +117,12 @@ bool pkgAcquire::Setup(pkgAcquireStatus *Progress, string const &Lock)
    if (Lock.empty())
    {
       string const listDir = _config->FindDir("Dir::State::lists");
-      if (SetupAPTPartialDirectory(_config->FindDir("Dir::State"), listDir) == false)
+      if (SetupAPTPartialDirectory(_config->FindDir("Dir::State"), listDir, "partial", 0700) == false)
 	 return _error->Errno("Acquire", _("List directory %spartial is missing."), listDir.c_str());
+      if (SetupAPTPartialDirectory(_config->FindDir("Dir::State"), listDir, "auxfiles", 0755) == false)
+	 return _error->Errno("Acquire", _("List directory %sauxfiles is missing."), listDir.c_str());
       string const archivesDir = _config->FindDir("Dir::Cache::Archives");
-      if (SetupAPTPartialDirectory(_config->FindDir("Dir::Cache"), archivesDir) == false)
+      if (SetupAPTPartialDirectory(_config->FindDir("Dir::Cache"), archivesDir, "partial", 0700) == false)
 	 return _error->Errno("Acquire", _("Archives directory %spartial is missing."), archivesDir.c_str());
       return true;
    }
@@ -137,14 +139,19 @@ bool pkgAcquire::GetLock(std::string const &Lock)
 
    if (Lock == listDir)
    {
-      if (SetupAPTPartialDirectory(_config->FindDir("Dir::State"), listDir) == false)
+      if (SetupAPTPartialDirectory(_config->FindDir("Dir::State"), listDir, "partial", 0700) == false)
 	 return _error->Errno("Acquire", _("List directory %spartial is missing."), listDir.c_str());
    }
    if (Lock == archivesDir)
    {
-      if (SetupAPTPartialDirectory(_config->FindDir("Dir::Cache"), archivesDir) == false)
+      if (SetupAPTPartialDirectory(_config->FindDir("Dir::Cache"), archivesDir, "partial", 0700) == false)
 	 return _error->Errno("Acquire", _("Archives directory %spartial is missing."), archivesDir.c_str());
    }
+   if (Lock == listDir || Lock == archivesDir)
+   {
+      if (SetupAPTPartialDirectory(_config->FindDir("Dir::State"), listDir, "auxfiles", 0755) == false)
+	 return _error->Errno("Acquire", _("List directory %sauxfiles is missing."), listDir.c_str());
+   }
 
    if (_config->FindB("Debug::NoLocking", false) == true)
       return true;
@@ -288,7 +295,6 @@ static bool CheckForBadItemAndFailIt(pkgAcquire::Item * const Item,
 	 "\nFilename: " + Item->DestFile +
 	 "\nFailReason: WeakHashSums";
 
-      auto SavedDesc = Item->GetItemDesc();
       Item->Status = pkgAcquire::Item::StatAuthError;
       Item->Failed(Message, Config);
       if (Log != nullptr)
@@ -303,7 +309,10 @@ void pkgAcquire::Enqueue(ItemDesc &Item)
    const MethodConfig *Config;
    string Name = QueueName(Item.URI,Config);
    if (Name.empty() == true)
+   {
+      Item.Owner->Status = pkgAcquire::Item::StatError;
       return;
+   }
 
    /* the check for running avoids that we produce errors
       in logging before we actually have started, which would
@@ -769,11 +778,12 @@ bool pkgAcquire::Clean(string Dir)
    for (struct dirent *E = readdir(D); E != nullptr; E = readdir(D))
    {
       // Skip some entries
-      if (strcmp(E->d_name,"lock") == 0 ||
-	  strcmp(E->d_name,"partial") == 0 ||
-	  strcmp(E->d_name,"lost+found") == 0 ||
-	  strcmp(E->d_name,".") == 0 ||
-	  strcmp(E->d_name,"..") == 0)
+      if (strcmp(E->d_name, "lock") == 0 ||
+	  strcmp(E->d_name, "partial") == 0 ||
+	  strcmp(E->d_name, "auxfiles") == 0 ||
+	  strcmp(E->d_name, "lost+found") == 0 ||
+	  strcmp(E->d_name, ".") == 0 ||
+	  strcmp(E->d_name, "..") == 0)
 	 continue;
 
       // Look in the get list and if not found nuke