Add deletion safeguard

index 507de2d..6e09858 100644
@@ -21,6 +21,7 @@
 
 import unittest
 import bb
+import os
 
 class VerCmpString(unittest.TestCase):
 

@@ -88,3 +89,19 @@ class VerCmpString(unittest.TestCase):
 
         # 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))

index 5ac9bcf..c97f3ef 100644
@@ -601,11 +601,30 @@ 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

@@ -619,6 +638,8 @@ 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))