Fix backward compatiblity of the new pkgAcquireMethod::DropPrivsOrDie()

Do not drop privileges in the methods when using a older version of
libapt that does not support the chown magic in partial/ yet. To
do this DropPrivileges() now will ignore a empty Apt::Sandbox::User.

Cleanup all hardcoded _apt along the way.

4 files changed, 21 insertions, 6 deletions

diff --git a/apt-pkg/acquire-item.cc b/apt-pkg/acquire-item.cc
index 97ff1bd18..44d45cedb 100644
--- a/apt-pkg/acquire-item.cc
+++ b/apt-pkg/acquire-item.cc
@@ -215,7 +215,11 @@ bool pkgAcquire::Item::Rename(string From,string To)
 void pkgAcquire::Item::QueueURI(ItemDesc &Item)
 {
    if (RealFileExists(DestFile))
-      ChangeOwnerAndPermissionOfFile("GetPartialFileName", DestFile.c_str(), "_apt", "root", 0600);
+   {
+      std::string SandboxUser = _config->Find("APT::Sandbox::User");
+      ChangeOwnerAndPermissionOfFile("GetPartialFileName", DestFile.c_str(),
+                                     SandboxUser.c_str(), "root", 0600);
+   }
    Owner->Enqueue(Item);
 }
 void pkgAcquire::Item::Dequeue()
@@ -2486,7 +2490,8 @@ bool pkgAcqArchive::QueueNext()
 	 else
 	 {
 	    PartialSize = Buf.st_size;
-	    ChangeOwnerAndPermissionOfFile("pkgAcqArchive::QueueNext", DestFile.c_str(), "_apt", "root", 0600);
+            std::string SandboxUser = _config->Find("APT::Sandbox::User");
+	    ChangeOwnerAndPermissionOfFile("pkgAcqArchive::QueueNext",DestFile.c_str(), SandboxUser.c_str(), "root", 0600);
 	 }
       }
 
@@ -2654,7 +2659,8 @@ pkgAcqFile::pkgAcqFile(pkgAcquire *Owner,string URI, HashStringList const &Hashe
       else
       {
 	 PartialSize = Buf.st_size;
-	 ChangeOwnerAndPermissionOfFile("pkgAcqFile", DestFile.c_str(), "_apt", "root", 0600);
+         std::string SandboxUser = _config->Find("APT::Sandbox::User");
+	 ChangeOwnerAndPermissionOfFile("pkgAcqFile", DestFile.c_str(), SandboxUser.c_str(), "root", 0600);
       }
    }
 
diff --git a/apt-pkg/acquire.cc b/apt-pkg/acquire.cc
index 34c7f06de..3ef912600 100644
--- a/apt-pkg/acquire.cc
+++ b/apt-pkg/acquire.cc
@@ -83,10 +83,11 @@ static bool SetupAPTPartialDirectory(std::string const &grand, std::string const
 
    if (getuid() == 0) // if we aren't root, we can't chown, so don't try it
    {
-      struct passwd *pw = getpwnam("_apt");
+      std::string SandboxUser = _config->Find("APT::Sandbox::User");
+      struct passwd *pw = getpwnam(SandboxUser.c_str());
       struct group *gr = getgrnam("root");
       if (pw != NULL && gr != NULL && chown(partial.c_str(), pw->pw_uid, gr->gr_gid) != 0)
-	 _error->WarningE("SetupAPTPartialDirectory", "chown to _apt:root of directory %s failed", partial.c_str());
+	 _error->WarningE("SetupAPTPartialDirectory", "chown to %s:root of directory %s failed", SandboxUser.c_str(), partial.c_str());
    }
    if (chmod(partial.c_str(), 0700) != 0)
       _error->WarningE("SetupAPTPartialDirectory", "chmod 0700 of directory %s failed", partial.c_str());
diff --git a/apt-pkg/contrib/fileutl.cc b/apt-pkg/contrib/fileutl.cc
index 3e592d94f..f6351b7b5 100644
--- a/apt-pkg/contrib/fileutl.cc
+++ b/apt-pkg/contrib/fileutl.cc
@@ -2168,6 +2168,12 @@ bool DropPrivileges()							/*{{{*/
    if(_config->FindB("Debug::NoDropPrivs", false) == true)
       return true;
 
+   // empty setting disables DropPrivilidges - this also ensures
+   // backward compatibility, see bug #764506
+   const std::string toUser = _config->Find("APT::Sandbox::User");
+   if (toUser.empty())
+      return true;
+
 #if __gnu_linux__
 #if defined(PR_SET_NO_NEW_PRIVS) && ( PR_SET_NO_NEW_PRIVS != 38 )
 #error "PR_SET_NO_NEW_PRIVS is defined, but with a different value than expected!"
@@ -2186,7 +2192,6 @@ bool DropPrivileges()							/*{{{*/
    if (old_uid != 0)
       return true;
 
-   const std::string toUser = _config->Find("APT::Sandbox::User", "_apt");
    struct passwd *pw = getpwnam(toUser.c_str());
    if (pw == NULL)
       return _error->Error("No user %s, can not drop rights", toUser.c_str());
diff --git a/apt-pkg/init.cc b/apt-pkg/init.cc
index 82dff4ee8..8d206e428 100644
--- a/apt-pkg/init.cc
+++ b/apt-pkg/init.cc
@@ -95,6 +95,9 @@ bool pkgInitConfig(Configuration &Cnf)
    // Default cdrom mount point
    Cnf.CndSet("Acquire::cdrom::mount", "/media/cdrom/");
 
+   // The default user we drop to in the methods
+   Cnf.CndSet("APT::Sandbox::User", "_apt");
+
    bool Res = true;
    
    // Read an alternate config file