filelog: raise CensoredNodeError when hash checks fail with censor metadata
With this change, when a revlog revision hash does not match its content, and
the content is empty with a special metadata key, the integrity failure is
assumed to be intentionally caused to remove sensitive content from repository
history.
To allow different Mercurial functionality to handle this scenario differently
a more specific exception is raised than "ordinary" hash failures.
Alternatives to this approach include, but are not limited to:
- Calling a hook when hashes mismatch to allow arbitrary tombstone validation.
Cons: Irresponsibly easy to disable integrity checking altogether.
- Returning empty revision data eagerly instead of raising, masking the error.
Cons: Push/pull won't roundtrip the tombstone, so client repos are unusable.
- Doing nothing differently at this layer. Callers must do their own detection
of tombstoned data if they want to handle some hash checks and not others.
- Impacts dozens of callsites, many of which don't have the revision data
- Would probably be missing one or two callsites at any given time
- Currently we throw a RevlogError, as do 12 other places in revlog.py.
Callers would need to parse the exception message and/or ensure
RevlogError is not thrown from any other part of their call tree.
--- a/mercurial/filelog.py Wed Sep 03 15:59:03 2014 -0400
+++ b/mercurial/filelog.py Wed Sep 03 22:14:20 2014 -0400
@@ -5,7 +5,7 @@
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
-import revlog
+import error, revlog
import re
_mdre = re.compile('\1\n')
@@ -27,6 +27,10 @@
metatext = "".join("%s: %s\n" % (k, meta[k]) for k in keys)
return "\1\n%s\1\n%s" % (metatext, text)
+def _censoredtext(text):
+ m, offs = parsemeta(text)
+ return m and "censored" in m and not text[offs:]
+
class filelog(revlog.revlog):
def __init__(self, opener, path):
super(filelog, self).__init__(opener,
@@ -86,5 +90,13 @@
return True
+ def checkhash(self, text, p1, p2, node, rev=None):
+ try:
+ super(filelog, self).checkhash(text, p1, p2, node, rev=rev)
+ except error.RevlogError:
+ if _censoredtext(text):
+ raise error.CensoredNodeError(self.indexfile, node)
+ raise
+
def _file(self, f):
return filelog(self.opener, f)