Special characters are not escaped for named groups

[th3-s3m]

In the modify_message function, when dynamically generating the regex value, special characters are not escaped if they're part of a named group (?P<{}>{}). When executing "match_exp = re_compile(exp + groups_exp)", groups_exp may contain special that will either generate an error or unexpected behavior.

Workaround:
In my case I was extracting a string that sometimes contains a + (base64-ish) with the following regex "token": "(?P<token>[^"]+).
I substituted lines 462, 463

    match_exp = re_compile(exp + groups_exp)
    self.logger.debug('match_exp adjusted to:\n{}'.format(match_exp.pattern))

with

    try:
        match_exp = re_compile(exp + groups_exp.replace('+','\+'))
    except re_error as e:
        self.logger.error(exc_invalid_regex.format(ph_target_exp, e))
        return msg_as_string

This workaround only fixed my case (+ char in extracted group), groups_exp should be properly escaped for all regex special characters before being recompiled.

Edit: workaround was not so clear.

[elespike]

Great catch, thank you!

Fixed here: 8d46886#diff-d59f892b7de1f2c8e5a2321095f452b4R451