321 lines
10 KiB
Python
321 lines
10 KiB
Python
# PyMod-Milter is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# PyMod-Milter is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with PyMod-Milter. If not, see <http://www.gnu.org/licenses/>.
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#
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__all__ = [
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"AddHeader",
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"ModHeader",
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"DelHeader",
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"AddDisclaimer",
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"RewriteLinks"]
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import logging
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from base64 import b64encode
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from bs4 import BeautifulSoup
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from collections import defaultdict
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from copy import copy
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from email.message import MIMEPart
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from pymodmilter import replace_illegal_chars
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class AddHeader:
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"""Add a mail header field."""
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def __init__(self, field, value):
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self.field = field
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self.value = value
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def execute(self, milter, pretend=False,
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logger=logging.getLogger(__name__)):
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header = f"{self.field}: {self.value}"
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if logger.getEffectiveLevel() == logging.DEBUG:
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logger.debug(f"add_header: {header}")
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else:
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logger.info(f"add_header: {header[0:70]}")
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milter.msg.add_header(self.field, self.value)
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if not pretend:
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milter.addheader(self.field, self.value)
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class ModHeader:
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"""Change the value of a mail header field."""
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def __init__(self, field, value, search=None):
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self.field = field
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self.value = value
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self.search = search
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def execute(self, milter, pretend=False,
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logger=logging.getLogger(__name__)):
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idx = defaultdict(int)
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for i, (field, value) in enumerate(milter.msg.items()):
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field_lower = field.lower()
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idx[field_lower] += 1
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if not self.field.match(field):
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continue
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new_value = value
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if self.search is not None:
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new_value = self.search.sub(self.value, value).strip()
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else:
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new_value = self.value
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if not new_value:
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logger.warning(
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"mod_header: resulting value is empty, "
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"skip modification")
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continue
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if new_value == value:
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continue
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header = f"{field}: {value}"
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new_header = f"{field}: {new_value}"
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if logger.getEffectiveLevel() == logging.DEBUG:
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logger.debug(f"mod_header: {header}: {new_header}")
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else:
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logger.info(f"mod_header: {header[0:70]}: {new_header[0:70]}")
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milter.msg.replace_header(
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field, replace_illegal_chars(new_value), idx=idx[field_lower])
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if not pretend:
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milter.chgheader(field, new_value, idx=idx[field_lower])
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class DelHeader:
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"""Delete a mail header field."""
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def __init__(self, field, value=None):
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self.field = field
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self.value = value
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def execute(self, milter, pretend=False,
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logger=logging.getLogger(__name__)):
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idx = defaultdict(int)
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for field, value in milter.msg.items():
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field_lower = field.lower()
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idx[field_lower] += 1
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if not self.field.match(field):
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continue
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if self.value is not None and not self.value.search(value):
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continue
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header = f"{field}: {value}"
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if logger.getEffectiveLevel() == logging.DEBUG:
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logger.debug(f"del_header: {header}")
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else:
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logger.info(f"del_header: {header[0:70]}")
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milter.msg.remove_header(field, idx=idx[field_lower])
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if not pretend:
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milter.chgheader(field, "", idx=idx[field_lower])
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idx[field_lower] -= 1
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def _get_body_content(msg, pref):
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part = None
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content = None
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if not msg.is_multipart() and msg.get_content_type() == f"text/{pref}":
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part = msg
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else:
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part = msg.get_body(preferencelist=(pref))
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if part is not None:
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content = part.get_content()
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return (part, content)
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def _has_content_before_body_tag(soup):
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s = copy(soup)
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for element in s.find_all("head") + s.find_all("body"):
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element.extract()
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if len(s.text.strip()) > 0:
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return True
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return False
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def _inject_body(milter):
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if not milter.msg.is_multipart():
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milter.msg.make_mixed()
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attachments = []
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for attachment in milter.msg.iter_attachments():
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if "content-disposition" not in attachment:
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attachment["Content-Disposition"] = "attachment"
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attachments.append(attachment)
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milter.msg.clear_content()
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milter.msg.set_content("")
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milter.msg.add_alternative("", subtype="html")
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milter.msg.make_mixed()
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for attachment in attachments:
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milter.msg.attach(attachment)
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def _wrap_message(milter):
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attachment = MIMEPart()
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attachment.set_content(milter.msg.as_bytes(),
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maintype="plain", subtype="text",
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disposition="attachment",
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filename=f"{milter.qid}.eml",
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params={"name": f"{milter.qid}.eml"})
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milter.msg.clear_content()
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milter.msg.set_content(
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"Please see the original email attached.")
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milter.msg.add_alternative(
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"<html><body>Please see the original email attached.</body></html>",
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subtype="html")
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milter.msg.make_mixed()
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milter.msg.attach(attachment)
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class AddDisclaimer:
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"""Append or prepend a disclaimer to the mail body."""
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def __init__(self, text_template, html_template, action, error_policy):
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self.text_template = text_template
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self.html_template = html_template
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self.action = action
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self.error_policy = error_policy
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def patch_message_body(self, milter, logger):
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text_body, text_content = _get_body_content(milter.msg, "plain")
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html_body, html_content = _get_body_content(milter.msg, "html")
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if text_content is None and html_content is None:
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raise RuntimeError("message does not contain any body part")
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if text_content is not None:
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logger.info(f"{self.action} text disclaimer")
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if self.action == "prepend":
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content = f"{self.text_template}{text_content}"
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else:
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content = f"{text_content}{self.text_template}"
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text_body.set_content(
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content.encode(), maintype="text", subtype="plain")
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text_body.set_param("charset", "UTF-8", header="Content-Type")
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del text_body["MIME-Version"]
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if html_content is not None:
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logger.info(f"{self.action} html disclaimer")
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soup = BeautifulSoup(html_content, "html.parser")
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body = soup.find('body')
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if not body:
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body = soup
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elif _has_content_before_body_tag(soup):
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body = soup
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if self.action == "prepend":
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body.insert(0, copy(self.html_template))
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else:
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body.append(self.html_template)
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html_body.set_content(
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str(soup).encode(), maintype="text", subtype="html")
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html_body.set_param("charset", "UTF-8", header="Content-Type")
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del html_body["MIME-Version"]
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def execute(self, milter, pretend=False,
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logger=logging.getLogger(__name__)):
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old_headers = milter.msg.items()
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try:
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try:
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self.patch_message_body(milter, logger)
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except RuntimeError as e:
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logger.info(f"{e}, inject empty plain and html body")
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_inject_body(milter)
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self.patch_message_body(milter, logger)
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except Exception as e:
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logger.warning(e)
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if self.error_policy == "ignore":
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logger.info(
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"unable to add disclaimer to message body, "
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"ignore error according to policy")
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return
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elif self.error_policy == "reject":
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logger.info(
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"unable to add disclaimer to message body, "
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"reject message according to policy")
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return [
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("reject", "Message rejected due to error")]
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logger.info("wrap original message in a new message envelope")
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try:
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_wrap_message(milter)
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self.patch_message_body(milter, logger)
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except Exception as e:
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logger.error(e)
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raise Exception(
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"unable to wrap message in a new message envelope, "
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"give up ...")
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if not pretend:
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milter.update_headers(old_headers)
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milter.replacebody()
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class RewriteLinks:
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"""Rewrite link targets in the mail html body."""
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def __init__(self, repl):
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self.repl = repl
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def execute(self, milter, pretend=False,
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logger=logging.getLogger(__name__)):
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html_body, html_content = _get_body_content(milter.msg, "html")
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if html_content is not None:
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soup = BeautifulSoup(html_content, "html.parser")
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rewritten = 0
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for link in soup.find_all("a", href=True):
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if not link["href"]:
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continue
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if "{URL_B64}" in self.repl:
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url_b64 = b64encode(link["href"].encode()).decode()
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target = self.repl.replace("{URL_B64}", url_b64)
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else:
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target = self.repl
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link["href"] = target
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rewritten += 1
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if rewritten:
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logger.info(f"rewrote {rewritten} link(s) in html body")
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html_body.set_content(
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str(soup).encode(), maintype="text", subtype="html")
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html_body.set_param("charset", "UTF-8", header="Content-Type")
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del html_body["MIME-Version"]
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if not pretend:
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milter.replacebody()
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