Arguments containing colons can be mis-cached

[akx]

Since the default key construction uses a colon (:) to separate raw string values, strings arguments with colons in them can lead to mis-caching.

(If an argument is user input, this could theoretically be a security issue allowing an user to access the "wrong" object from the cache.)

POC – the assertion fails since only one call was made, since the cache key is a:b:c:bla for both invocations.

def test_colons():
    calls_made = []
    @cache_memoize(10)
    def fun(a, b, k="bla"):
        calls_made.append((a, b, k))
        return (a, b, k)

    fun('a:b', 'c')
    fun('a', 'b:c')
    assert len(calls_made) == 2