Bug#577226: [apt] improve Dpkg::Chroot-Directory for installation of packages in chroot

[Kel Modderman <kel@otaku42.de>]

Package: apt
Version: 0.7.25.3
Severity: wishlist
Tags: patch

Hi,

Here is a python program which bootstraps a sid system, then attempts to 
install a package in the chroot:
---
#!/usr/bin/python

import apt.cache
import apt_pkg
import os
import subprocess
import sys

subprocess.call('debootstrap --variant=minbase sid /tmp/crap http://localhost:9999/debian/'.split())
apt_pkg.init()
apt_pkg.config.set('Dpkg::Chroot-Directory', '/tmp/crap')
cache = apt.cache.Cache(rootdir='/tmp/crap')
apt_pkg.Config.clear("DPkg::Pre-Install-Pkgs")
cache.update()
cache.open()
cache['hello'].mark_install()
cache.commit()
---

It fails, because after chroot('/tmp/crap') the later dpkg process gets given
a filename argument which begins with the pathname to chroot itself and is
not accessible:
---
Reading package lists... Done
Building dependency tree... Done
Building data structures... Done
Reading package lists... Done
Building dependency tree... Done
Building data structures... Done
Chrooting into /tmp/crap/
dpkg: error processing /tmp/crap/var/cache/apt/archives/hello_2.5-1_amd64.deb (--unpack):
 cannot access archive: No such file or directory
Errors were encountered while processing:
 /tmp/crap/var/cache/apt/archives/hello_2.5-1_amd64.deb
Traceback (most recent call last):
  File "./test_apt.py", line 17, in <module>
    cache.commit()
  File "/usr/lib/python2.5/site-packages/apt/deprecation.py", line 98, in deprecated_function
    return func(*args, **kwds)
  File "/usr/lib/python2.5/site-packages/apt/cache.py", line 381, in commit
    raise SystemError("installArchives() failed")
SystemError: installArchives() failed
---

The following patch adds some logic to check each File, when
DPkg::Chroot-Directory != '/', to see if it begins with the pathname
of the chroot. If it does, it returns a substring of File without the
chroot pathname. It is careful not to strip the leading / from any File.
---
--- a/apt-pkg/deb/dpkgpm.cc
+++ b/apt-pkg/deb/dpkgpm.cc
@@ -124,6 +124,18 @@ bool pkgDPkgPM::Install(PkgIterator Pkg,
    if (File.empty() == true || Pkg.end() == true)
       return _error->Error("Internal Error, No file name for %s",Pkg.Name());
 
+   // If the filename string begins with DPkg::Chroot-Directory, return the
+   // substr that is within the chroot so dpkg can access it.
+   string chrootdir = _config->FindDir("DPkg::Chroot-Directory","/");
+   if (chrootdir.compare("/") != 0 && File.find(chrootdir) == 0)
+   {
+      size_t len = chrootdir.length();
+      if (chrootdir.at(len - 1) == '/')
+	 len--;
+      List.push_back(Item(Item::Install,Pkg,File.substr(len)));
+      return true;
+   }
+
    List.push_back(Item(Item::Install,Pkg,File));
    return true;
 }
---

Can you please consider applying it?

Thanks, Kel.

--- System information. ---
Architecture: amd64
Kernel:       Linux 2.6.33-2.slh.3-sidux-amd64

Debian Release: squeeze/sid
  500 unstable        localhost 
    1 experimental    localhost 

--- Package information. ---
Depends                       (Version) | Installed
=======================================-+-=============
libc6                        (>= 2.3.4) | 2.10.2-6
libgcc1                    (>= 1:4.1.1) | 1:4.4.3-7
libstdc++6                   (>= 4.4.0) | 4.4.3-7
debian-archive-keyring                  | 2009.01.31


Package's Recommends field is empty.

Suggests        (Version) | Installed
=========================-+-===========
aptitude                  | 
 OR synaptic              | 
 OR wajig                 | 
dpkg-dev                  | 1.15.5.6
apt-doc                   | 
bzip2                     | 1.0.5-4
lzma                      | 4.43-14
python-apt                | 0.7.94.2