bitbake: lib/bb/utils: add safeguard against recursively deleting things we shouldn't

Add some very basic safeguard against recursively deleting paths such
as / and /home in the event of bugs or user mistakes.

Addresses [YOCTO #7620].

(Bitbake master rev: 56cddeb9e1e4d249f84ccd6ef65db245636e38ea)

(Bitbake rev: fbf1c39641f78d553961974a2bb96256eb9496e7)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/tests/utils.py

@@ -21,6 +21,7 @@
 
 import unittest
 import bb
+import os
 
 class VerCmpString(unittest.TestCase):
 
@@ -51,3 +52,52 @@ class VerCmpString(unittest.TestCase):
         result = bb.utils.explode_dep_versions2("foo ( =1.10 )")
         self.assertEqual(result, correctresult)
 
+    def test_vercmp_string_op(self):
+        compareops = [('1', '1', '=', True),
+                      ('1', '1', '==', True),
+                      ('1', '1', '!=', False),
+                      ('1', '1', '>', False),
+                      ('1', '1', '<', False),
+                      ('1', '1', '>=', True),
+                      ('1', '1', '<=', True),
+                      ('1', '0', '=', False),
+                      ('1', '0', '==', False),
+                      ('1', '0', '!=', True),
+                      ('1', '0', '>', True),
+                      ('1', '0', '<', False),
+                      ('1', '0', '>>', True),
+                      ('1', '0', '<<', False),
+                      ('1', '0', '>=', True),
+                      ('1', '0', '<=', False),
+                      ('0', '1', '=', False),
+                      ('0', '1', '==', False),
+                      ('0', '1', '!=', True),
+                      ('0', '1', '>', False),
+                      ('0', '1', '<', True),
+                      ('0', '1', '>>', False),
+                      ('0', '1', '<<', True),
+                      ('0', '1', '>=', False),
+                      ('0', '1', '<=', True)]
+
+        for arg1, arg2, op, correctresult in compareops:
+            result = bb.utils.vercmp_string_op(arg1, arg2, op)
+            self.assertEqual(result, correctresult, 'vercmp_string_op("%s", "%s", "%s") != %s' % (arg1, arg2, op, correctresult))
+
+        # Check that clearly invalid operator raises an exception
+        self.assertRaises(bb.utils.VersionStringException, bb.utils.vercmp_string_op, '0', '0', '$')
+
+
+class Path(unittest.TestCase):
+    def test_unsafe_delete_path(self):
+        checkitems = [('/', True),
+                      ('//', True),
+                      ('///', True),
+                      (os.getcwd().count(os.sep) * ('..' + os.sep), True),
+                      (os.environ.get('HOME', '/home/test'), True),
+                      ('/home/someone', True),
+                      ('/home/other/', True),
+                      ('/home/other/subdir', False),
+                      ('', False)]
+        for arg1, correctresult in checkitems:
+            result = bb.utils._check_unsafe_delete_path(arg1)
+            self.assertEqual(result, correctresult, '_check_unsafe_delete_path("%s") != %s' % (arg1, correctresult))

bitbake/lib/bb/utils.py

@@ -575,11 +575,30 @@ def build_environment(d):
         if export:
             os.environ[var] = d.getVar(var, True) or ""
 
+def _check_unsafe_delete_path(path):
+    """
+    Basic safeguard against recursively deleting something we shouldn't. If it returns True,
+    the caller should raise an exception with an appropriate message.
+    NOTE: This is NOT meant to be a security mechanism - just a guard against silly mistakes
+    with potentially disastrous results.
+    """
+    extra = ''
+    # HOME might not be /home/something, so in case we can get it, check against it
+    homedir = os.environ.get('HOME', '')
+    if homedir:
+        extra = '|%s' % homedir
+    if re.match('(/|//|/home|/home/[^/]*%s)$' % extra, os.path.abspath(path)):
+        return True
+    return False
+
 def remove(path, recurse=False):
     """Equivalent to rm -f or rm -rf"""
     if not path:
         return
     if recurse:
+        for name in glob.glob(path):
+            if _check_unsafe_delete_path(path):
+                raise Exception('bb.utils.remove: called with dangerous path "%s" and recurse=True, refusing to delete!' % path)
         # shutil.rmtree(name) would be ideal but its too slow
         subprocess.call(['rm', '-rf'] + glob.glob(path))
         return
@@ -593,6 +612,8 @@ def remove(path, recurse=False):
 def prunedir(topdir):
     # Delete everything reachable from the directory named in 'topdir'.
     # CAUTION:  This is dangerous!
+    if _check_unsafe_delete_path(topdir):
+        raise Exception('bb.utils.prunedir: called with dangerous path "%s", refusing to delete!' % topdir)
     for root, dirs, files in os.walk(topdir, topdown = False):
         for name in files:
             os.remove(os.path.join(root, name))