tests/test-url.py

cborutil: implement sans I/O decoder

The vendored CBOR package decodes by calling read(n) on an object.
There are a number of disadvantages to this:

* Uses blocking I/O. If sufficient data is not available, the decoder
  will hang until it is.
* No support for partial reads. If the read(n) returns less data than
  requested, the decoder raises an error.
* Requires the use of a file like object. If the original data is in
  say a buffer, we need to "cast" it to e.g. a BytesIO to appease the
  decoder.

In addition, the vendored CBOR decoder doesn't provide flexibility
that we desire. Specifically:

* It buffers indefinite length bytestrings instead of streaming them.
* It doesn't allow limiting the set of types that can be decoded. This
  property is useful when implementing a "hardened" decoder that is
  less susceptible to abusive input.
* It doesn't provide sufficient "hook points" and introspection to
  institute checks around behavior. These are useful for implementing
  a "hardened" decoder.

This all adds up to a reasonable set of justifications for writing our
own decoder.

So, this commit implements our own CBOR decoder.

At the heart of the decoder is a function that decodes a single "item"
from a buffer. This item can be a complete simple value or a special
value, such as "start of array." Using this function, we can build a
decoder that effectively iterates over the stream of decoded items and
builds up higher-level values, such as arrays, maps, sets, and indefinite
length bytestrings. And we can do this without performing I/O in the
decoder itself.

The core of the sans I/O decoder will probably not be used directly.
Instead, it is expected that we'll build utility functions for invoking
the decoder given specific input types. This will allow extreme
flexibility in how data is delivered to the decoder.

I'm pretty happy with the state of the decoder modulo the TODO items
to track wanted features to help with a "hardened" decoder. The one
thing I could be convinced to change is the handling of semantic tags.
Since we only support a single semantic tag (sets), I thought it would
be easier to handle them inline in decodeitem(). This is simpler now.
But if we add support for other semantic tags, it will likely be easier
to move semantic tag handling outside of decodeitem(). But, properly
supporting semantic tags opens up a whole can of worms, as many
semantic tags imply new types. I'm optimistic we won't need these in
Mercurial. But who knows.

I'm also pretty happy with the test coverage. Writing comprehensive
tests for partial decoding did flush out a handful of bugs. One
general improvement to testing would be fuzz testing for partial
decoding. I may implement that later. I also anticipate switching the
wire protocol code to this new decoder will flush out any lingering
bugs.

Differential Revision: https://phab.mercurial-scm.org/D4414

# coding=utf-8
from __future__ import absolute_import, print_function

import doctest
import os

def check(a, b):
    if a != b:
        print((a, b))

def cert(cn):
    return {'subject': ((('commonName', cn),),)}

from mercurial import (
    sslutil,
)

_verifycert = sslutil._verifycert
# Test non-wildcard certificates
check(_verifycert(cert('example.com'), 'example.com'),
      None)
check(_verifycert(cert('example.com'), 'www.example.com'),
      b'certificate is for example.com')
check(_verifycert(cert('www.example.com'), 'example.com'),
      b'certificate is for www.example.com')

# Test wildcard certificates
check(_verifycert(cert('*.example.com'), 'www.example.com'),
      None)
check(_verifycert(cert('*.example.com'), 'example.com'),
      b'certificate is for *.example.com')
check(_verifycert(cert('*.example.com'), 'w.w.example.com'),
      b'certificate is for *.example.com')

# Test subjectAltName
san_cert = {'subject': ((('commonName', 'example.com'),),),
            'subjectAltName': (('DNS', '*.example.net'),
                               ('DNS', 'example.net'))}
check(_verifycert(san_cert, 'example.net'),
      None)
check(_verifycert(san_cert, 'foo.example.net'),
      None)
# no fallback to subject commonName when subjectAltName has DNS
check(_verifycert(san_cert, 'example.com'),
      b'certificate is for *.example.net, example.net')
# fallback to subject commonName when no DNS in subjectAltName
san_cert = {'subject': ((('commonName', 'example.com'),),),
            'subjectAltName': (('IP Address', '8.8.8.8'),)}
check(_verifycert(san_cert, 'example.com'), None)

# Avoid some pitfalls
check(_verifycert(cert('*.foo'), 'foo'),
      b'certificate is for *.foo')
check(_verifycert(cert('*o'), 'foo'), None)

check(_verifycert({'subject': ()},
                  'example.com'),
      b'no commonName or subjectAltName found in certificate')
check(_verifycert(None, 'example.com'),
      b'no certificate received')

# Unicode (IDN) certname isn't supported
check(_verifycert(cert(u'\u4f8b.jp'), 'example.jp'),
      b'IDN in certificate not supported')

# The following tests are from CPython's test_ssl.py.
check(_verifycert(cert('example.com'), 'example.com'), None)
check(_verifycert(cert('example.com'), 'ExAmple.cOm'), None)
check(_verifycert(cert('example.com'), 'www.example.com'),
      b'certificate is for example.com')
check(_verifycert(cert('example.com'), '.example.com'),
      b'certificate is for example.com')
check(_verifycert(cert('example.com'), 'example.org'),
      b'certificate is for example.com')
check(_verifycert(cert('example.com'), 'exampleXcom'),
      b'certificate is for example.com')
check(_verifycert(cert('*.a.com'), 'foo.a.com'), None)
check(_verifycert(cert('*.a.com'), 'bar.foo.a.com'),
      b'certificate is for *.a.com')
check(_verifycert(cert('*.a.com'), 'a.com'),
      b'certificate is for *.a.com')
check(_verifycert(cert('*.a.com'), 'Xa.com'),
      b'certificate is for *.a.com')
check(_verifycert(cert('*.a.com'), '.a.com'),
      b'certificate is for *.a.com')

# only match one left-most wildcard
check(_verifycert(cert('f*.com'), 'foo.com'), None)
check(_verifycert(cert('f*.com'), 'f.com'), None)
check(_verifycert(cert('f*.com'), 'bar.com'),
      b'certificate is for f*.com')
check(_verifycert(cert('f*.com'), 'foo.a.com'),
      b'certificate is for f*.com')
check(_verifycert(cert('f*.com'), 'bar.foo.com'),
      b'certificate is for f*.com')

# NULL bytes are bad, CVE-2013-4073
check(_verifycert(cert('null.python.org\x00example.org'),
                  'null.python.org\x00example.org'), None)
check(_verifycert(cert('null.python.org\x00example.org'),
                  'example.org'),
      b'certificate is for null.python.org\x00example.org')
check(_verifycert(cert('null.python.org\x00example.org'),
                  'null.python.org'),
      b'certificate is for null.python.org\x00example.org')

# error cases with wildcards
check(_verifycert(cert('*.*.a.com'), 'bar.foo.a.com'),
      b'certificate is for *.*.a.com')
check(_verifycert(cert('*.*.a.com'), 'a.com'),
      b'certificate is for *.*.a.com')
check(_verifycert(cert('*.*.a.com'), 'Xa.com'),
      b'certificate is for *.*.a.com')
check(_verifycert(cert('*.*.a.com'), '.a.com'),
      b'certificate is for *.*.a.com')

check(_verifycert(cert('a.*.com'), 'a.foo.com'),
      b'certificate is for a.*.com')
check(_verifycert(cert('a.*.com'), 'a..com'),
      b'certificate is for a.*.com')
check(_verifycert(cert('a.*.com'), 'a.com'),
      b'certificate is for a.*.com')

# wildcard doesn't match IDNA prefix 'xn--'
idna = u'püthon.python.org'.encode('idna').decode('ascii')
check(_verifycert(cert(idna), idna), None)
check(_verifycert(cert('x*.python.org'), idna),
      b'certificate is for x*.python.org')
check(_verifycert(cert('xn--p*.python.org'), idna),
      b'certificate is for xn--p*.python.org')

# wildcard in first fragment and  IDNA A-labels in sequent fragments
# are supported.
idna = u'www*.pythön.org'.encode('idna').decode('ascii')
check(_verifycert(cert(idna),
                  u'www.pythön.org'.encode('idna').decode('ascii')),
      None)
check(_verifycert(cert(idna),
                  u'www1.pythön.org'.encode('idna').decode('ascii')),
      None)
check(_verifycert(cert(idna),
                  u'ftp.pythön.org'.encode('idna').decode('ascii')),
      b'certificate is for www*.xn--pythn-mua.org')
check(_verifycert(cert(idna),
                  u'pythön.org'.encode('idna').decode('ascii')),
      b'certificate is for www*.xn--pythn-mua.org')

c = {
    'notAfter': 'Jun 26 21:41:46 2011 GMT',
    'subject': (((u'commonName', u'linuxfrz.org'),),),
    'subjectAltName': (
        ('DNS', 'linuxfr.org'),
        ('DNS', 'linuxfr.com'),
        ('othername', '<unsupported>'),
    )
}
check(_verifycert(c, 'linuxfr.org'), None)
check(_verifycert(c, 'linuxfr.com'), None)
# Not a "DNS" entry
check(_verifycert(c, '<unsupported>'),
      b'certificate is for linuxfr.org, linuxfr.com')
# When there is a subjectAltName, commonName isn't used
check(_verifycert(c, 'linuxfrz.org'),
      b'certificate is for linuxfr.org, linuxfr.com')

# A pristine real-world example
c = {
    'notAfter': 'Dec 18 23:59:59 2011 GMT',
    'subject': (
        ((u'countryName', u'US'),),
        ((u'stateOrProvinceName', u'California'),),
        ((u'localityName', u'Mountain View'),),
        ((u'organizationName', u'Google Inc'),),
        ((u'commonName', u'mail.google.com'),),
    ),
}
check(_verifycert(c, 'mail.google.com'), None)
check(_verifycert(c, 'gmail.com'), b'certificate is for mail.google.com')

# Only commonName is considered
check(_verifycert(c, 'California'), b'certificate is for mail.google.com')

# Neither commonName nor subjectAltName
c = {
    'notAfter': 'Dec 18 23:59:59 2011 GMT',
    'subject': (
        ((u'countryName', u'US'),),
        ((u'stateOrProvinceName', u'California'),),
        ((u'localityName', u'Mountain View'),),
        ((u'organizationName', u'Google Inc'),),
    ),
}
check(_verifycert(c, 'mail.google.com'),
      b'no commonName or subjectAltName found in certificate')

# No DNS entry in subjectAltName but a commonName
c = {
    'notAfter': 'Dec 18 23:59:59 2099 GMT',
    'subject': (
        ((u'countryName', u'US'),),
        ((u'stateOrProvinceName', u'California'),),
        ((u'localityName', u'Mountain View'),),
        ((u'commonName', u'mail.google.com'),),
    ),
    'subjectAltName': (('othername', 'blabla'),),
}
check(_verifycert(c, 'mail.google.com'), None)

# No DNS entry subjectAltName and no commonName
c = {
    'notAfter': 'Dec 18 23:59:59 2099 GMT',
    'subject': (
        ((u'countryName', u'US'),),
        ((u'stateOrProvinceName', u'California'),),
        ((u'localityName', u'Mountain View'),),
        ((u'organizationName', u'Google Inc'),),
    ),
    'subjectAltName': (('othername', 'blabla'),),
}
check(_verifycert(c, 'google.com'),
      b'no commonName or subjectAltName found in certificate')

# Empty cert / no cert
check(_verifycert(None, 'example.com'), b'no certificate received')
check(_verifycert({}, 'example.com'), b'no certificate received')

# avoid denials of service by refusing more than one
# wildcard per fragment.
check(_verifycert({'subject': (((u'commonName', u'a*b.com'),),)},
                  'axxb.com'), None)
check(_verifycert({'subject': (((u'commonName', u'a*b.co*'),),)},
                  'axxb.com'), b'certificate is for a*b.co*')
check(_verifycert({'subject': (((u'commonName', u'a*b*.com'),),)},
                  'axxbxxc.com'),
      b'too many wildcards in certificate DNS name: a*b*.com')

def test_url():
    """
    >>> from mercurial import error, pycompat
    >>> from mercurial.util import url
    >>> from mercurial.utils.stringutil import forcebytestr

    This tests for edge cases in url.URL's parsing algorithm. Most of
    these aren't useful for documentation purposes, so they aren't
    part of the class's doc tests.

    Query strings and fragments:

    >>> url(b'http://host/a?b#c')
    <url scheme: 'http', host: 'host', path: 'a', query: 'b', fragment: 'c'>
    >>> url(b'http://host/a?')
    <url scheme: 'http', host: 'host', path: 'a'>
    >>> url(b'http://host/a#b#c')
    <url scheme: 'http', host: 'host', path: 'a', fragment: 'b#c'>
    >>> url(b'http://host/a#b?c')
    <url scheme: 'http', host: 'host', path: 'a', fragment: 'b?c'>
    >>> url(b'http://host/?a#b')
    <url scheme: 'http', host: 'host', path: '', query: 'a', fragment: 'b'>
    >>> url(b'http://host/?a#b', parsequery=False)
    <url scheme: 'http', host: 'host', path: '?a', fragment: 'b'>
    >>> url(b'http://host/?a#b', parsefragment=False)
    <url scheme: 'http', host: 'host', path: '', query: 'a#b'>
    >>> url(b'http://host/?a#b', parsequery=False, parsefragment=False)
    <url scheme: 'http', host: 'host', path: '?a#b'>

    IPv6 addresses:

    >>> url(b'ldap://[2001:db8::7]/c=GB?objectClass?one')
    <url scheme: 'ldap', host: '[2001:db8::7]', path: 'c=GB',
         query: 'objectClass?one'>
    >>> url(b'ldap://joe:xxx@[2001:db8::7]:80/c=GB?objectClass?one')
    <url scheme: 'ldap', user: 'joe', passwd: 'xxx', host: '[2001:db8::7]',
         port: '80', path: 'c=GB', query: 'objectClass?one'>

    Missing scheme, host, etc.:

    >>> url(b'://192.0.2.16:80/')
    <url path: '://192.0.2.16:80/'>
    >>> url(b'https://mercurial-scm.org')
    <url scheme: 'https', host: 'mercurial-scm.org'>
    >>> url(b'/foo')
    <url path: '/foo'>
    >>> url(b'bundle:/foo')
    <url scheme: 'bundle', path: '/foo'>
    >>> url(b'a?b#c')
    <url path: 'a?b', fragment: 'c'>
    >>> url(b'http://x.com?arg=/foo')
    <url scheme: 'http', host: 'x.com', query: 'arg=/foo'>
    >>> url(b'http://joe:xxx@/foo')
    <url scheme: 'http', user: 'joe', passwd: 'xxx', path: 'foo'>

    Just a scheme and a path:

    >>> url(b'mailto:[e-mail]')
    <url scheme: 'mailto', path: '[e-mail]'>
    >>> url(b'a:b:c:d')
    <url path: 'a:b:c:d'>
    >>> url(b'aa:bb:cc:dd')
    <url scheme: 'aa', path: 'bb:cc:dd'>

    SSH examples:

    >>> url(b'ssh://joe@host//home/joe')
    <url scheme: 'ssh', user: 'joe', host: 'host', path: '/home/joe'>
    >>> url(b'ssh://joe:xxx@host/src')
    <url scheme: 'ssh', user: 'joe', passwd: 'xxx', host: 'host', path: 'src'>
    >>> url(b'ssh://joe:xxx@host')
    <url scheme: 'ssh', user: 'joe', passwd: 'xxx', host: 'host'>
    >>> url(b'ssh://joe@host')
    <url scheme: 'ssh', user: 'joe', host: 'host'>
    >>> url(b'ssh://host')
    <url scheme: 'ssh', host: 'host'>
    >>> url(b'ssh://')
    <url scheme: 'ssh'>
    >>> url(b'ssh:')
    <url scheme: 'ssh'>

    Non-numeric port:

    >>> url(b'http://example.com:dd')
    <url scheme: 'http', host: 'example.com', port: 'dd'>
    >>> url(b'ssh://joe:xxx@host:ssh/foo')
    <url scheme: 'ssh', user: 'joe', passwd: 'xxx', host: 'host', port: 'ssh',
         path: 'foo'>

    Bad authentication credentials:

    >>> url(b'http://joe@joeville:123@4:@host/a?b#c')
    <url scheme: 'http', user: 'joe@joeville', passwd: '123@4:',
         host: 'host', path: 'a', query: 'b', fragment: 'c'>
    >>> url(b'http://!*#?/@!*#?/:@host/a?b#c')
    <url scheme: 'http', host: '!*', fragment: '?/@!*#?/:@host/a?b#c'>
    >>> url(b'http://!*#?@!*#?:@host/a?b#c')
    <url scheme: 'http', host: '!*', fragment: '?@!*#?:@host/a?b#c'>
    >>> url(b'http://!*@:!*@@host/a?b#c')
    <url scheme: 'http', user: '!*@', passwd: '!*@', host: 'host',
         path: 'a', query: 'b', fragment: 'c'>

    File paths:

    >>> url(b'a/b/c/d.g.f')
    <url path: 'a/b/c/d.g.f'>
    >>> url(b'/x///z/y/')
    <url path: '/x///z/y/'>
    >>> url(b'/foo:bar')
    <url path: '/foo:bar'>
    >>> url(b'\\\\foo:bar')
    <url path: '\\\\foo:bar'>
    >>> url(b'./foo:bar')
    <url path: './foo:bar'>

    Non-localhost file URL:

    >>> try:
    ...   u = url(b'file://mercurial-scm.org/foo')
    ... except error.Abort as e:
    ...   forcebytestr(e)
    'file:// URLs can only refer to localhost'

    Empty URL:

    >>> u = url(b'')
    >>> u
    <url path: ''>
    >>> str(u)
    ''

    Empty path with query string:

    >>> str(url(b'http://foo/?bar'))
    'http://foo/?bar'

    Invalid path:

    >>> u = url(b'http://foo/bar')
    >>> u.path = b'bar'
    >>> str(u)
    'http://foo/bar'

    >>> u = url(b'file:/foo/bar/baz')
    >>> u
    <url scheme: 'file', path: '/foo/bar/baz'>
    >>> str(u)
    'file:///foo/bar/baz'
    >>> pycompat.bytestr(u.localpath())
    '/foo/bar/baz'

    >>> u = url(b'file:///foo/bar/baz')
    >>> u
    <url scheme: 'file', path: '/foo/bar/baz'>
    >>> str(u)
    'file:///foo/bar/baz'
    >>> pycompat.bytestr(u.localpath())
    '/foo/bar/baz'

    >>> u = url(b'file:///f:oo/bar/baz')
    >>> u
    <url scheme: 'file', path: 'f:oo/bar/baz'>
    >>> str(u)
    'file:///f:oo/bar/baz'
    >>> pycompat.bytestr(u.localpath())
    'f:oo/bar/baz'

    >>> u = url(b'file://localhost/f:oo/bar/baz')
    >>> u
    <url scheme: 'file', host: 'localhost', path: 'f:oo/bar/baz'>
    >>> str(u)
    'file://localhost/f:oo/bar/baz'
    >>> pycompat.bytestr(u.localpath())
    'f:oo/bar/baz'

    >>> u = url(b'file:foo/bar/baz')
    >>> u
    <url scheme: 'file', path: 'foo/bar/baz'>
    >>> str(u)
    'file:foo/bar/baz'
    >>> pycompat.bytestr(u.localpath())
    'foo/bar/baz'
    """

if 'TERM' in os.environ:
    del os.environ['TERM']

doctest.testmod(optionflags=doctest.NORMALIZE_WHITESPACE)