ignore for _apt inaccessible TMPDIR in pkgAcqChangelog

Using libpam-tmpdir caused us to create our download tmp directory in
root's private tmp before changing to _apt, which wouldn't have access
to it.

By extending our GetTempDir method with an optional wrapper changing the
effective user, we can test if a given user can access the directory and
ignore TMPDIR if not instead of ignoring TMPDIR completely.

Closes: 797270

1 files changed, 2 insertions, 2 deletions

diff --git a/apt-pkg/acquire-item.cc b/apt-pkg/acquire-item.cc
index f505531c1..b6b6d8e48 100644
--- a/apt-pkg/acquire-item.cc
+++ b/apt-pkg/acquire-item.cc
@@ -2999,7 +2999,8 @@ void pkgAcqChangelog::Init(std::string const &DestDir, std::string const &DestFi
 
    if (DestDir.empty())
    {
-      std::string const systemTemp = GetTempDir();
+      std::string const SandboxUser = _config->Find("APT::Sandbox::User");
+      std::string const systemTemp = GetTempDir(SandboxUser);
       char tmpname[100];
       snprintf(tmpname, sizeof(tmpname), "%s/apt-changelog-XXXXXX", systemTemp.c_str());
       if (NULL == mkdtemp(tmpname))
@@ -3010,7 +3011,6 @@ void pkgAcqChangelog::Init(std::string const &DestDir, std::string const &DestFi
       }
       DestFile = TemporaryDirectory = tmpname;
 
-      std::string SandboxUser = _config->Find("APT::Sandbox::User");
       ChangeOwnerAndPermissionOfFile("Item::QueueURI", DestFile.c_str(),
                                      SandboxUser.c_str(), "root", 0700);
    }