chown finished partial files earlier

partial files are chowned by the Item baseclass to let the methods work
with them. Now, this baseclass is also responsible for chowning the
files back to root instead of having various deeper levels do this.

The consequence is that all overloaded Failed() methods now call the
Item::Failed base as their first step. The same is done for Done().

The effect is that even in partial files usually don't belong to
_apt anymore, helping sneakernets and reducing possibilities of a bad
method modifying files not belonging to them.

The change is supported by the framework not only supporting being run
as root, but with proper permission management, too, so that privilege
dropping can be tested with them.

1 files changed, 25 insertions, 15 deletions

diff --git a/apt-pkg/acquire.cc b/apt-pkg/acquire.cc
index 1e20b74be..2c89c2dea 100644
--- a/apt-pkg/acquire.cc
+++ b/apt-pkg/acquire.cc
@@ -54,23 +54,38 @@ pkgAcquire::pkgAcquire() : LockFD(-1), Queues(0), Workers(0), Configs(0), Log(NU
 			   Debug(_config->FindB("Debug::pkgAcquire",false)),
 			   Running(false)
 {
-   string const Mode = _config->Find("Acquire::Queue-Mode","host");
-   if (strcasecmp(Mode.c_str(),"host") == 0)
-      QueueMode = QueueHost;
-   if (strcasecmp(Mode.c_str(),"access") == 0)
-      QueueMode = QueueAccess;
+   Initialize();
 }
 pkgAcquire::pkgAcquire(pkgAcquireStatus *Progress) : LockFD(-1), Queues(0), Workers(0),
 			   Configs(0), Log(NULL), ToFetch(0),
 			   Debug(_config->FindB("Debug::pkgAcquire",false)),
 			   Running(false)
 {
+   Initialize();
+   SetLog(Progress);
+}
+void pkgAcquire::Initialize()
+{
    string const Mode = _config->Find("Acquire::Queue-Mode","host");
    if (strcasecmp(Mode.c_str(),"host") == 0)
       QueueMode = QueueHost;
    if (strcasecmp(Mode.c_str(),"access") == 0)
       QueueMode = QueueAccess;
-   SetLog(Progress);
+
+   // chown the auth.conf file as it will be accessed by our methods
+   std::string const SandboxUser = _config->Find("APT::Sandbox::User");
+   if (getuid() == 0 && SandboxUser.empty() == false) // if we aren't root, we can't chown, so don't try it
+   {
+      struct passwd const * const pw = getpwnam(SandboxUser.c_str());
+      struct group const * const gr = getgrnam("root");
+      if (pw != NULL && gr != NULL)
+      {
+	 std::string const AuthConf = _config->FindFile("Dir::Etc::netrc");
+	 if(AuthConf.empty() == false && RealFileExists(AuthConf) &&
+	       chown(AuthConf.c_str(), pw->pw_uid, gr->gr_gid) != 0)
+	    _error->WarningE("SetupAPTPartialDirectory", "chown to %s:root of file %s failed", SandboxUser.c_str(), AuthConf.c_str());
+      }
+   }
 }
 									/*}}}*/
 // Acquire::GetLock - lock directory and prepare for action		/*{{{*/
@@ -81,21 +96,16 @@ static bool SetupAPTPartialDirectory(std::string const &grand, std::string const
 	 CreateAPTDirectoryIfNeeded(parent, partial) == false)
       return false;
 
-   if (getuid() == 0) // if we aren't root, we can't chown, so don't try it
+   std::string const SandboxUser = _config->Find("APT::Sandbox::User");
+   if (getuid() == 0 && SandboxUser.empty() == false) // if we aren't root, we can't chown, so don't try it
    {
-      std::string SandboxUser = _config->Find("APT::Sandbox::User");
-      struct passwd *pw = getpwnam(SandboxUser.c_str());
-      struct group *gr = getgrnam("root");
+      struct passwd const * const pw = getpwnam(SandboxUser.c_str());
+      struct group const * const gr = getgrnam("root");
       if (pw != NULL && gr != NULL)
       {
          // chown the partial dir
          if(chown(partial.c_str(), pw->pw_uid, gr->gr_gid) != 0)
             _error->WarningE("SetupAPTPartialDirectory", "chown to %s:root of directory %s failed", SandboxUser.c_str(), partial.c_str());
-         // chown the auth.conf file
-         std::string const AuthConf = _config->FindFile("Dir::Etc::netrc");
-	 if(AuthConf.empty() == false && RealFileExists(AuthConf) &&
-	       chown(AuthConf.c_str(), pw->pw_uid, gr->gr_gid) != 0)
-	    _error->WarningE("SetupAPTPartialDirectory", "chown to %s:root of file %s failed", SandboxUser.c_str(), AuthConf.c_str());
       }
    }
    if (chmod(partial.c_str(), 0700) != 0)