src/mercurialserver/ruleset.py
author Paul Crowley <paul@lshift.net>
Mon, 18 Apr 2011 12:03:14 +0100
changeset 301 f88549f44c8e
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Further refactor, dispense with unnecessary method
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"""
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Glob-based, order-based rules matcher that can answer "maybe"
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where the inputs make clear that something is unknown.
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"""
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import sys
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import re
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import os
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import os.path
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def globmatcher(pattern):
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    p = "[^/]*".join(re.escape(c) for c in pattern.split("*"))
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    # ** means "match recursively" ie "ignore directories"
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    return re.compile(p.replace("[^/]*[^/]*", ".*") + "$")
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# Returns 1 for a definite match
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# -1 for a definite non-match
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# 0 where we can't be sure because a key is None
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def rmatch(k, m, kw):
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    if k not in kw:
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        return -1
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    kkw = kw[k]
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    if kkw is None:
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        return 0
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    elif m.match(kkw) is None:
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        return -1
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    else:
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        return 1
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def rule(pairs):
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    matchers = [(k, globmatcher(v)) for k, v in pairs]
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    def c(kw):
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        return min(rmatch(k, m, kw) for k, m in matchers)
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    return c
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class Ruleset(object):
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    '''Class representing the rules in a rule file'''
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    levels = ["init", "write", "read", "deny"]
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    def __init__(self):
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        self.rules = []
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        self.preset = {}
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    def set(self, **kw):
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        self.preset.update(kw)
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    def get(self, k):
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        return self.preset.get(k, None)
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    def allow(self, level, **kw):
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        levelindex = self.levels.index(level)
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        d = self.preset.copy()
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        d.update(kw)
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        for a, c in self.rules:
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            m = c(d)
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            if m == 1:
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                # Definite match - what it says goes
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                return a <= levelindex
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            elif m == 0:
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                # "Maybe match" - allow if it says yes, ignore if no
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                if a <= levelindex:
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                    return True
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        return False
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    def readfile(self, fn):
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        f = open(fn)
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        try:
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            for l in f:
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                l = l.strip()
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                if len(l) == 0 or l.startswith("#"):
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                    continue
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                l = l.split()
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                # Unrecognized actions are off the high end
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                if l[0] in self.levels:
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                    ix = self.levels.index(l[0])
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                else:
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                    ix = len(self.levels)
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                self.rules.append((ix, 
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                    rule([c.split("=", 1) for c in l[1:]])))
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        finally:
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            f.close()
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rules = Ruleset()
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