Slack -> (API Gateway -> ) Lambda -> SES (Reply Email)

config.ini

[slack]
hook_url = https://hooks.slack.com/services/xxxxxxxxxx/yyyyyyyyyy/zzzzzzzzzzzzzzzzzzzzzzz
username = alert_bot
channel = #alert
icon_emoji = :guardsman:
token = TOKEN

[s3]
region = ap-northeast-1
bucket_name = BUCKET_NAME

[ses]
mail_from = no-reply@SES_RECEIVE_DOMAIN

lambda_function_skack2email_reply.py

# coding: utf-8
import boto3
import re
import struct
import traceback
import json
import ConfigParser
from email.parser import FeedParser
from email.header import decode_header, Header
from email.utils import parseaddr, formatdate
from email.mime.text import MIMEText
import slackweb

def send_raw_mail(region, subject, message_id, mail_from, reply_to, mail_body, slack_user):
  ses = boto3.client('ses', region_name=region)
  body = u"""[Slackユーザ %s からの返信です。]

%s""" % (slack_user, mail_body)

  msg = MIMEText(body, 'plain', 'utf-8')
  msg['Subject'] = subject
  msg['From'] = "%s <%s>" % (slack_user, mail_from)
  msg['To'] = reply_to
  msg['In-Reply-To'] = message_id
  msg['References'] = message_id

  res = ses.send_raw_email(
                  Source = mail_from,
                  Destinations = [reply_to],
		  RawMessage = {'Data': msg.as_string()}
		  )

  return res

def lambda_handler(event, context):
  inifile = ConfigParser.SafeConfigParser()
  inifile.read("./config.ini")

  if not event['token'] == inifile.get('slack', 'token'):
    return ""

  text = event['text']
  user_name = event['user_name']
  channel_name = event['channel_name']

  response = ""

  try:
    bucket_region = inifile.get('s3', 'region')
    bucket_name =  inifile.get('s3', 'bucket_name')

    reply_pattern = u"^@alert_bot:?\s+reply\s+(.*?)\s+(.*)"
    r = re.search(reply_pattern, text, re.DOTALL)
    if r:
      mail_object_key = r.group(1)
      mail_body = r.group(2)
    
      ses_region = mail_object_key.split('/')[0]

      s3 = boto3.client('s3', region_name=bucket_region)
      mail_object = s3.get_object(Bucket = bucket_name, Key = mail_object_key)
      mail = ''
      try:
        mail = mail_object["Body"].read().decode('utf-8')
      except:
        try:
          mail = mail_object["Body"].read().decode('iso-2022-jp')
        except:
          mail = mail_object["Body"].read()
    
      parser = FeedParser()
      parser.feed(mail)
      parsed_mail = parser.close()
    
      (d_sub, sub_charset) = decode_header(parsed_mail['Subject'])[0]
      subject = u"Re: %s" % d_sub.decode(sub_charset)
      message_id = parsed_mail['Message-ID']
      if parsed_mail.has_key('Reply-To'):
        reply_to = parsed_mail['Reply-To']
      else:
        reply_to = parseaddr(parsed_mail['From'])[1]

      send_raw_mail(ses_region, subject, message_id, inifile.get('ses', 'mail_from'), reply_to, mail_body, user_name)

      response = u"@%s: 受け付けました" % user_name
    else:
      response = u"@%s: その操作は受け付けられません。" % user_name

  except:
    response = u"@%s: error" % user_name
    print traceback.format_exc()
  finally:
    return response