[PATCH] fetch2: handle absolute paths in subdir

[PATCH] fetch2: handle absolute paths in subdir

[Ross Burton]

Currently if you use the subdir parameter in a SRC_URI and pass an absolute path
then it gets appended to the unpack directory instead of being used directly.
This is inconvenient as it may be useful to use ${S} when you want to unpack a
file into the source tree.

Change this behaviour so that absolute paths are used directly instead of being
appended to the root directory.  To ensure that recipes cannot write files to an
arbitrary location enforce that the subdir starts with the unpack root.

Signed-off-by: Ross Burton <ross.burton@intel.com>
---
 bitbake/lib/bb/fetch2/__init__.py | 8 +++++++-
 bitbake/lib/bb/tests/fetch.py     | 9 +++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/bitbake/lib/bb/fetch2/__init__.py b/bitbake/lib/bb/fetch2/__init__.py
index 06f1eb4..cd7362c 100644
--- a/bitbake/lib/bb/fetch2/__init__.py
+++ b/bitbake/lib/bb/fetch2/__init__.py
@@ -1420,7 +1420,13 @@ class FetchMethod(object):
 
         # If 'subdir' param exists, create a dir and use it as destination for unpack cmd
         if 'subdir' in urldata.parm:
-            unpackdir = '%s/%s' % (rootdir, urldata.parm.get('subdir'))
+            subdir = urldata.parm.get('subdir')
+            if os.path.isabs(subdir):
+                if not os.path.realpath(subdir).startswith(os.path.realpath(rootdir)):
+                    raise UnpackError("subdir argument isn't a subdirectory of unpack root %s" % rootdir, urldata.url)
+                unpackdir = subdir
+            else:
+                unpackdir = os.path.join(rootdir, subdir)
             bb.utils.mkdirhier(unpackdir)
         else:
             unpackdir = rootdir
diff --git a/bitbake/lib/bb/tests/fetch.py b/bitbake/lib/bb/tests/fetch.py
index d7c73dd..0fd2c02 100644
--- a/bitbake/lib/bb/tests/fetch.py
+++ b/bitbake/lib/bb/tests/fetch.py
@@ -508,6 +508,15 @@ class FetcherLocalTest(FetcherTest):
         tree = self.fetchUnpack(['file://dir/subdir/e;subdir=bar'])
         self.assertEqual(tree, ['bar/dir/subdir/e'])
 
+    def test_local_absolutedir(self):
+        # Unpacking to an absolute path that is a subdirectory of the root
+        # should work
+        tree = self.fetchUnpack(['file://a;subdir=%s' % os.path.join(self.unpackdir, 'bar')])
+
+        # Unpacking to an absolute path outside of the root should fail
+        with self.assertRaises(bb.fetch2.UnpackError):
+            self.fetchUnpack(['file://a;subdir=/bin/sh'])
+
 class FetcherNetworkTest(FetcherTest):
 
     if os.environ.get("BB_SKIP_NETTESTS") == "yes":
-- 
2.8.1

Re: [PATCH] fetch2: handle absolute paths in subdir

[Christopher Larson]

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On Wed, Sep 21, 2016 at 9:48 AM, Ross Burton <ross.burton@intel.com> wrote:

> Currently if you use the subdir parameter in a SRC_URI and pass an
> absolute path
> then it gets appended to the unpack directory instead of being used
> directly.
> This is inconvenient as it may be useful to use ${S} when you want to
> unpack a
> file into the source tree.
>
> Change this behaviour so that absolute paths are used directly instead of
> being
> appended to the root directory.  To ensure that recipes cannot write files
> to an
> arbitrary location enforce that the subdir starts with the unpack root.
>
> Signed-off-by: Ross Burton <ross.burton@intel.com>
>

Looks good to me, thanks for your work on this.
-- 
Christopher Larson
clarson at kergoth dot com
Founder - BitBake, OpenEmbedded, OpenZaurus
Maintainer - Tslib
Senior Software Engineer, Mentor Graphics

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