From 9163511743a6d8c9b62fb6cd4b2a47f2ceae0b61 Mon Sep 17 00:00:00 2001
From: Michał Górny <mgorny@gentoo.org>
Date: Wed, 25 Oct 2017 00:07:19 +0200
Subject: verify: Support checking for cross-filesystem files

---
 gemato/exceptions.py | 12 ++++++++++++
 gemato/verify.py     | 15 ++++++++++++---
 tests/test_verify.py | 24 ++++++++++++++++++++++++
 3 files changed, 48 insertions(+), 3 deletions(-)

diff --git a/gemato/exceptions.py b/gemato/exceptions.py
index e580309..c9cb646 100644
--- a/gemato/exceptions.py
+++ b/gemato/exceptions.py
@@ -38,3 +38,15 @@ class ManifestMismatch(Exception):
         self.path = path
         self.entry = entry
         self.diff = diff
+
+
+class ManifestCrossDevice(Exception):
+    """
+    An exception caused by attempting to cross filesystem boundaries.
+    """
+
+    def __init__(self, path):
+        self.path = path
+        super(ManifestCrossDevice, self).__init__(
+            "Path {} crosses filesystem boundaries, it must be IGNORE-d explicitly"
+            .format(path))
diff --git a/gemato/verify.py b/gemato/verify.py
index ef8092b..74791ee 100644
--- a/gemato/verify.py
+++ b/gemato/verify.py
@@ -13,7 +13,7 @@ import gemato.hash
 import gemato.manifest
 
 
-def verify_path(path, e):
+def verify_path(path, e, expected_dev=None):
     """
     Verify the file at system path @path against the data in entry @e.
     The path/filename is not matched against the entry -- the correct
@@ -24,6 +24,11 @@ def verify_path(path, e):
     the file at path and the Manifest entry. Each list element is
     a tuple of (name, expected, got).
 
+    If @expected_dev is not None, verifies that the file resides
+    on specified device. If the device does not match, raises
+    ManifestCrossDevice exception. It can be used to verify that
+    the files do not cross filesystem boundaries.
+
     Each name can be:
     - __exists__ (boolean) to indicate whether the file existed,
     - __type__ (string) as a human-readable description of file type,
@@ -70,6 +75,10 @@ def verify_path(path, e):
         st = os.fstat(fd)
     else:
         st = os.stat(path)
+    if expected_dev is not None and st.st_dev != expected_dev:
+        if opened:
+            os.close(fd)
+        raise gemato.exceptions.ManifestCrossDevice(path)
     if not opened or not stat.S_ISREG(st.st_mode):
         if opened:
             os.close(fd)
@@ -169,12 +178,12 @@ def verify_entry_compatibility(e1, e2):
     return (ret, diff)
 
 
-def assert_path_verifies(path, e):
+def assert_path_verifies(path, e, expected_dev=None):
     """
     Verify the path @path against entry @e. Raises an exception if it
     does not pass the verification.
     """
 
-    ret, diff = verify_path(path, e)
+    ret, diff = verify_path(path, e, expected_dev=expected_dev)
     if not ret:
         raise gemato.exceptions.ManifestMismatch(path, e, diff)
diff --git a/tests/test_verify.py b/tests/test_verify.py
index 4902ec8..bc41532 100644
--- a/tests/test_verify.py
+++ b/tests/test_verify.py
@@ -241,6 +241,30 @@ class EmptyFileVerificationTest(unittest.TestCase):
         self.assertEqual(gemato.verify.verify_path(self.path, None),
                 (False, [('__exists__', False, True)]))
 
+    def testCrossFilesystem(self):
+        try:
+            st = os.stat('/proc')
+        except OSError:
+            raise unittest.SkipTest('Unable to stat /proc')
+
+        e = gemato.manifest.ManifestEntryDATA.from_list(
+                ('DATA', os.path.basename(self.path), '0'))
+        self.assertRaises(gemato.exceptions.ManifestCrossDevice,
+                gemato.verify.verify_path, self.path, e,
+                expected_dev=st.st_dev)
+
+    def testCrossFilesystemAssert(self):
+        try:
+            st = os.stat('/proc')
+        except OSError:
+            raise unittest.SkipTest('Unable to stat /proc')
+
+        e = gemato.manifest.ManifestEntryDATA.from_list(
+                ('DATA', os.path.basename(self.path), '0'))
+        self.assertRaises(gemato.exceptions.ManifestCrossDevice,
+                gemato.verify.assert_path_verifies, self.path, e,
+                expected_dev=st.st_dev)
+
 
 class NonEmptyFileVerificationTest(unittest.TestCase):
     def setUp(self):
-- 
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