view mercurial/narrowspec.py @ 37047:fddcb51b5084

wireproto: define permissions-based routing of HTTPv2 wire protocol

Now that we have a scaffolding for serving version 2 of the HTTP
protocol, let's start implementing it.

A good place to start is URL routing and basic request processing
semantics. We can focus on content types, capabilities detect, etc
later.

Version 2 of the HTTP wire protocol encodes the needed permissions
of the request in the URL path. The reasons for this are documented
in the added documentation. In short, a) it makes it really easy and
fail proof for server administrators to implement path-based
authentication and b) it will enable clients to realize very early in
a server exchange that authentication will be required to complete
the operation. This latter point avoids all kinds of complexity and
problems, like dealing with Expect: 100-continue and clients finding
out later during `hg push` that they need to provide authentication.
This will avoid the current badness where clients send a full bundle,
get an HTTP 403, provide authentication, then retransmit the bundle.

In order to implement command checking, we needed to implement a
protocol handler for the new wire protocol. Our handler is just
small enough to run the code we've implemented.

Tests for the defined functionality have been added.

I very much want to refactor the permissions checking code and define
a better response format. But this can be done later. Nothing is
covered by backwards compatibility at this point.

Differential Revision: https://phab.mercurial-scm.org/D2836

# narrowspec.py - methods for working with a narrow view of a repository
#
# Copyright 2017 Google, Inc.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

import errno

from .i18n import _
from . import (
    error,
    match as matchmod,
    util,
)

FILENAME = 'narrowspec'

def _parsestoredpatterns(text):
    """Parses the narrowspec format that's stored on disk."""
    patlist = None
    includepats = []
    excludepats = []
    for l in text.splitlines():
        if l == '[includes]':
            if patlist is None:
                patlist = includepats
            else:
                raise error.Abort(_('narrowspec includes section must appear '
                                    'at most once, before excludes'))
        elif l == '[excludes]':
            if patlist is not excludepats:
                patlist = excludepats
            else:
                raise error.Abort(_('narrowspec excludes section must appear '
                                    'at most once'))
        else:
            patlist.append(l)

    return set(includepats), set(excludepats)

def parseserverpatterns(text):
    """Parses the narrowspec format that's returned by the server."""
    includepats = set()
    excludepats = set()

    # We get one entry per line, in the format "<key> <value>".
    # It's OK for value to contain other spaces.
    for kp in (l.split(' ', 1) for l in text.splitlines()):
        if len(kp) != 2:
            raise error.Abort(_('Invalid narrowspec pattern line: "%s"') % kp)
        key = kp[0]
        pat = kp[1]
        if key == 'include':
            includepats.add(pat)
        elif key == 'exclude':
            excludepats.add(pat)
        else:
            raise error.Abort(_('Invalid key "%s" in server response') % key)

    return includepats, excludepats

def normalizesplitpattern(kind, pat):
    """Returns the normalized version of a pattern and kind.

    Returns a tuple with the normalized kind and normalized pattern.
    """
    pat = pat.rstrip('/')
    _validatepattern(pat)
    return kind, pat

def _numlines(s):
    """Returns the number of lines in s, including ending empty lines."""
    # We use splitlines because it is Unicode-friendly and thus Python 3
    # compatible. However, it does not count empty lines at the end, so trick
    # it by adding a character at the end.
    return len((s + 'x').splitlines())

def _validatepattern(pat):
    """Validates the pattern and aborts if it is invalid.

    Patterns are stored in the narrowspec as newline-separated
    POSIX-style bytestring paths. There's no escaping.
    """

    # We use newlines as separators in the narrowspec file, so don't allow them
    # in patterns.
    if _numlines(pat) > 1:
        raise error.Abort(_('newlines are not allowed in narrowspec paths'))

    components = pat.split('/')
    if '.' in components or '..' in components:
        raise error.Abort(_('"." and ".." are not allowed in narrowspec paths'))

def normalizepattern(pattern, defaultkind='path'):
    """Returns the normalized version of a text-format pattern.

    If the pattern has no kind, the default will be added.
    """
    kind, pat = matchmod._patsplit(pattern, defaultkind)
    return '%s:%s' % normalizesplitpattern(kind, pat)

def parsepatterns(pats):
    """Parses a list of patterns into a typed pattern set."""
    return set(normalizepattern(p) for p in pats)

def format(includes, excludes):
    output = '[includes]\n'
    for i in sorted(includes - excludes):
        output += i + '\n'
    output += '[excludes]\n'
    for e in sorted(excludes):
        output += e + '\n'
    return output

def match(root, include=None, exclude=None):
    if not include:
        # Passing empty include and empty exclude to matchmod.match()
        # gives a matcher that matches everything, so explicitly use
        # the nevermatcher.
        return matchmod.never(root, '')
    return matchmod.match(root, '', [], include=include or [],
                          exclude=exclude or [])

def needsexpansion(includes):
    return [i for i in includes if i.startswith('include:')]

def load(repo):
    try:
        spec = repo.vfs.read(FILENAME)
    except IOError as e:
        # Treat "narrowspec does not exist" the same as "narrowspec file exists
        # and is empty".
        if e.errno == errno.ENOENT:
            # Without this the next call to load will use the cached
            # non-existence of the file, which can cause some odd issues.
            repo.invalidate(clearfilecache=True)
            return set(), set()
        raise
    return _parsestoredpatterns(spec)

def save(repo, includepats, excludepats):
    spec = format(includepats, excludepats)
    repo.vfs.write(FILENAME, spec)

def restrictpatterns(req_includes, req_excludes, repo_includes, repo_excludes):
    r""" Restricts the patterns according to repo settings,
    results in a logical AND operation

    :param req_includes: requested includes
    :param req_excludes: requested excludes
    :param repo_includes: repo includes
    :param repo_excludes: repo excludes
    :return: include patterns, exclude patterns, and invalid include patterns.

    >>> restrictpatterns({'f1','f2'}, {}, ['f1'], [])
    (set(['f1']), {}, [])
    >>> restrictpatterns({'f1'}, {}, ['f1','f2'], [])
    (set(['f1']), {}, [])
    >>> restrictpatterns({'f1/fc1', 'f3/fc3'}, {}, ['f1','f2'], [])
    (set(['f1/fc1']), {}, [])
    >>> restrictpatterns({'f1_fc1'}, {}, ['f1','f2'], [])
    ([], set(['path:.']), [])
    >>> restrictpatterns({'f1/../f2/fc2'}, {}, ['f1','f2'], [])
    (set(['f2/fc2']), {}, [])
    >>> restrictpatterns({'f1/../f3/fc3'}, {}, ['f1','f2'], [])
    ([], set(['path:.']), [])
    >>> restrictpatterns({'f1/$non_exitent_var'}, {}, ['f1','f2'], [])
    (set(['f1/$non_exitent_var']), {}, [])
    """
    res_excludes = set(req_excludes)
    res_excludes.update(repo_excludes)
    invalid_includes = []
    if not req_includes:
        res_includes = set(repo_includes)
    elif 'path:.' not in repo_includes:
        res_includes = []
        for req_include in req_includes:
            req_include = util.expandpath(util.normpath(req_include))
            if req_include in repo_includes:
                res_includes.append(req_include)
                continue
            valid = False
            for repo_include in repo_includes:
                if req_include.startswith(repo_include + '/'):
                    valid = True
                    res_includes.append(req_include)
                    break
            if not valid:
                invalid_includes.append(req_include)
        if len(res_includes) == 0:
            res_excludes = {'path:.'}
        else:
            res_includes = set(res_includes)
    else:
        res_includes = set(req_includes)
    return res_includes, res_excludes, invalid_includes