Use correct filename on IMS-hit reverify for indices

If we have no old Release file, but old indices we can't compare
hashsums with the new Release file and hence must request the indices
again and have to react to IMS hits if they didn't change.

We used to symlink the old index file to the partial directory, but that
usually meant that we linked an uncompressed file to a compressed file,
which  not all uncompressors can deal with transparently resulting in
strange failures.

We could do without the symlink, but that would require changes in the
codepaths dealing with failure as they would rename the file to FAILED.

1 files changed, 6 insertions, 11 deletions

diff --git a/apt-pkg/acquire-item.cc b/apt-pkg/acquire-item.cc
index a108eb213..062b39cad 100644
--- a/apt-pkg/acquire-item.cc
+++ b/apt-pkg/acquire-item.cc
@@ -3265,19 +3265,14 @@ void pkgAcqIndex::StageDownloadDone(string const &Message)
 
    // we need to verify the file against the current Release file again
    // on if-modfied-since hit to avoid a stale attack against us
-   if(StringToBool(LookupTag(Message,"IMS-Hit"),false) == true)
+   if (StringToBool(LookupTag(Message, "IMS-Hit"), false))
    {
-      // copy FinalFile into partial/ so that we check the hash again
-      string const FinalFile = GetExistingFilename(GetFinalFileNameFromURI(Target.URI));
-      if (symlink(FinalFile.c_str(), DestFile.c_str()) != 0)
-	 _error->WarningE("pkgAcqIndex::StageDownloadDone", "Symlinking final file %s back to %s failed", FinalFile.c_str(), DestFile.c_str());
-      else
-      {
-	 EraseFileName = DestFile;
-	 Filename = DestFile;
-      }
+      Filename = GetExistingFilename(GetFinalFileNameFromURI(Target.URI));
+      EraseFileName = DestFile = flCombine(flNotFile(DestFile), flNotDir(Filename));
+      if (symlink(Filename.c_str(), DestFile.c_str()) != 0)
+	 _error->WarningE("pkgAcqIndex::StageDownloadDone", "Symlinking file %s to %s failed", Filename.c_str(), DestFile.c_str());
       Stage = STAGE_DECOMPRESS_AND_VERIFY;
-      Desc.URI = "store:" + Filename;
+      Desc.URI = "store:" + DestFile;
       QueueURI(Desc);
       SetActiveSubprocess(::URI(Desc.URI).Access);
       return;