procutil: make stream detection in make_line_buffered more correct and strict
In make_line_buffered(), we don’t want to wrap the stream if we know that lines
get flushed to the underlying raw stream already.
Previously, the heuristic was too optimistic. It assumed that any stream which
is not an instance of io.BufferedIOBase doesn’t need wrapping. However, there
are buffered streams that aren’t instances of io.BufferedIOBase, like
Mercurial’s own winstdout.
The new logic is different in two ways:
First, only for the check, if unwraps any combination of WriteAllWrapper and
winstdout.
Second, it skips wrapping the stream only if it is an instance of io.RawIOBase
(or already wrapped). If it is an instance of io.BufferedIOBase, it gets
wrapped. In any other case, the function raises an exception. This ensures
that, if an unknown stream is passed or we add another wrapper in the future,
we don’t wrap the stream if it’s already line buffered or not wrap the stream
if it’s not line buffered. In fact, this was already helpful during development
of this change. Without it, I possibly would have forgot that WriteAllWrapper
needs to be ignored for the check, leading to unnecessary wrapping if stdout is
unbuffered.
The alternative would have been to always wrap unknown streams. However, I
don’t think that anyone would benefit from being less strict. We can expect
streams from the standard library to be subclassing either io.RawIOBase or
io.BufferedIOBase, so running Mercurial in the standard way should not regress
by this change. Py2exe might replace sys.stdout and sys.stderr, but that
currently breaks Mercurial anyway and also these streams don’t claim to be
interactive, so this function is not called for them.
$ hg init empty-repo
$ cd empty-repo
Flags on revlog version 0 are rejected
>>> with open('.hg/store/00changelog.i', 'wb') as fh:
... fh.write(b'\x00\x01\x00\x00') and None
$ hg log
abort: unknown flags (0x01) in version 0 revlog 00changelog
[50]
Unknown flags on revlog version 1 are rejected
>>> with open('.hg/store/00changelog.i', 'wb') as fh:
... fh.write(b'\x00\x04\x00\x01') and None
$ hg log
abort: unknown flags (0x04) in version 1 revlog 00changelog
[50]
Unknown version is rejected
>>> with open('.hg/store/00changelog.i', 'wb') as fh:
... fh.write(b'\x00\x00\xbe\xef') and None
$ hg log
abort: unknown version (48879) in revlog 00changelog
[50]
$ cd ..
Test for CVE-2016-3630
$ mkdir test2; cd test2
$ hg init
>>> import codecs
>>> open("a.i", "wb").write(codecs.decode(codecs.decode(
... b"""eJxjYGZgZIAAYQYGxhgom+k/FMx8YKx9ZUaKSOyqo4cnuKb8mbqHV5cBCVTMWb1Cwqkhe4Gsg9AD
... Joa3dYtcYYYBAQ8Qr4OqZAYRICPTSr5WKd/42rV36d+8/VmrNpv7NP1jQAXrQE4BqQUARngwVA==""",
... "base64"), "zlib")) and None
$ hg debugrevlogindex a.i
rev linkrev nodeid p1 p2
0 2 99e0332bd498 000000000000 000000000000
1 3 6674f57a23d8 99e0332bd498 000000000000
>>> from mercurial.revlogutils.constants import KIND_OTHER
>>> from mercurial import revlog, vfs
>>> tvfs = vfs.vfs(b'.')
>>> tvfs.options = {b'revlogv1': True}
>>> rl = revlog.revlog(tvfs, target=(KIND_OTHER, b'test'), radix=b'a')
>>> rl.revision(1)
mpatchError(*'patch cannot be decoded'*) (glob)
$ cd ..
Regression test for support for the old repos with strange diff encoding.
Apparently it used to be possible (maybe it's still possible, but we don't know how)
to create commits whose diffs are encoded relative to a nullrev.
This test checks that a repo with that encoding can still be read.
This is what we did to produce the repo in test-revlog-diff-relative-to-nullrev.tar:
- tweak the code in mercurial/revlogutils/deltas.py to produce such "trivial" deltas:
> if deltainfo is None:
> - deltainfo = self._fullsnapshotinfo(fh, revinfo, target_rev)
> + deltainfo = self._builddeltainfo(revinfo, nullrev, fh)
- hg init
- echo hi > a
- hg commit -Am_
- remove some cache files
$ tar --force-local -xf "$TESTDIR"/bundles/test-revlog-diff-relative-to-nullrev.tar
$ cd nullrev-diff
$ hg debugdeltachain a
rev p1 p2 chain# chainlen prev delta size rawsize chainsize ratio lindist extradist extraratio readsize largestblk rddensity srchunks
0 -1 -1 1 2 -1 p1 15 3 15 5.00000 15 0 0.00000 15 15 1.00000 1
1 0 -1 1 2 -1 p2 15 3 15 5.00000 30 15 1.00000 30 30 0.50000 1
2 -1 -1 1 2 -1 p1 15 3 15 5.00000 45 30 2.00000 45 45 0.33333 1
$ hg cat --config rhg.cat=true -r 0 a
hi
$ hg cat --config rhg.cat=true -r 1 a
ho
$ hg cat --config rhg.cat=true -r 2 a
ha
$ cd ..