feat: add SMTP proxy server (#177)

smtp_proxy_server/.env.example

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+proxy_url=https://temp-email-api.xxx.xxx
+port=8025

smtp_proxy_server/.gitignore

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+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
+
+# C extensions
+*.so
+
+# Distribution / packaging
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+share/python-wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+MANIFEST
+
+# PyInstaller
+#  Usually these files are written by a python script from a template
+#  before PyInstaller builds the exe, so as to inject date/other infos into it.
+*.manifest
+*.spec
+
+# Installer logs
+pip-log.txt
+pip-delete-this-directory.txt
+
+# Unit test / coverage reports
+htmlcov/
+.tox/
+.nox/
+.coverage
+.coverage.*
+.cache
+nosetests.xml
+coverage.xml
+*.cover
+*.py,cover
+.hypothesis/
+.pytest_cache/
+cover/
+
+# Translations
+*.mo
+*.pot
+
+# Django stuff:
+*.log
+local_settings.py
+db.sqlite3
+db.sqlite3-journal
+
+# Flask stuff:
+instance/
+.webassets-cache
+
+# Scrapy stuff:
+.scrapy
+
+# Sphinx documentation
+docs/_build/
+
+# PyBuilder
+.pybuilder/
+target/
+
+# Jupyter Notebook
+.ipynb_checkpoints
+
+# IPython
+profile_default/
+ipython_config.py
+
+# pyenv
+#   For a library or package, you might want to ignore these files since the code is
+#   intended to run in multiple environments; otherwise, check them in:
+# .python-version
+
+# pipenv
+#   According to pypa/pipenv#598, it is recommended to include Pipfile.lock in version control.
+#   However, in case of collaboration, if having platform-specific dependencies or dependencies
+#   having no cross-platform support, pipenv may install dependencies that don't work, or not
+#   install all needed dependencies.
+#Pipfile.lock
+
+# poetry
+#   Similar to Pipfile.lock, it is generally recommended to include poetry.lock in version control.
+#   This is especially recommended for binary packages to ensure reproducibility, and is more
+#   commonly ignored for libraries.
+#   https://python-poetry.org/docs/basic-usage/#commit-your-poetrylock-file-to-version-control
+#poetry.lock
+
+# pdm
+#   Similar to Pipfile.lock, it is generally recommended to include pdm.lock in version control.
+#pdm.lock
+#   pdm stores project-wide configurations in .pdm.toml, but it is recommended to not include it
+#   in version control.
+#   https://pdm.fming.dev/#use-with-ide
+.pdm.toml
+
+# PEP 582; used by e.g. github.com/David-OConnor/pyflow and github.com/pdm-project/pdm
+__pypackages__/
+
+# Celery stuff
+celerybeat-schedule
+celerybeat.pid
+
+# SageMath parsed files
+*.sage.py
+
+# Environments
+.env
+.venv
+env/
+venv/
+ENV/
+env.bak/
+venv.bak/
+
+# Spyder project settings
+.spyderproject
+.spyproject
+
+# Rope project settings
+.ropeproject
+
+# mkdocs documentation
+/site
+
+# mypy
+.mypy_cache/
+.dmypy.json
+dmypy.json
+
+# Pyre type checker
+.pyre/
+
+# pytype static type analyzer
+.pytype/
+
+# Cython debug symbols
+cython_debug/
+
+# PyCharm
+#  JetBrains specific template is maintained in a separate JetBrains.gitignore that can
+#  be found at https://github.com/github/gitignore/blob/main/Global/JetBrains.gitignore
+#  and can be added to the global gitignore or merged into this file.  For a more nuclear
+#  option (not recommended) you can uncomment the following to ignore the entire idea folder.
+#.idea/
+test*

smtp_proxy_server/docker-compose.yaml

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+services:
+  smtp_proxy_server:
+    image: ghcr.io/dreamhunter2333/cloudflare_temp_email/smtp_proxy_server:latest
+    # build:
+    #   context: .
+    #   dockerfile: dockerfile
+    container_name: "smtp_proxy_server"
+    ports:
+      - "8025:8025"
+    environment:
+      - proxy_url=https://temp-email-api.xxx.xxx
+      - port=8025

smtp_proxy_server/dockerfile

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+FROM python:3.12-slim
+
+WORKDIR /app
+COPY requirements.txt /requirements.txt
+RUN python3 -m pip install -r /requirements.txt
+COPY . /app
+ENTRYPOINT [ "python3", "server.py" ]

smtp_proxy_server/requirements.txt

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+aiosmtpd==1.4.5
+pydantic-settings==2.2.1
+requests==2.31.0

smtp_proxy_server/server.py

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+import asyncio
+import logging
+import email
+import requests
+
+from pydantic_settings import BaseSettings
+from aiosmtpd.controller import Controller
+from aiosmtpd.smtp import SMTP, Session, Envelope, AuthResult, LoginPassword
+
+logging.basicConfig(
+    format='%(asctime)s - %(name)s - %(levelname)s - %(message)s',
+)
+
+_logger = logging.getLogger(__name__)
+_logger.setLevel(logging.INFO)
+
+
+class Settings(BaseSettings):
+    proxy_url: str = "http://localhost:8787"
+    port: int = 8025
+
+    class Config:
+        env_file = ".env"
+
+
+class CustomSMTPHandler:
+
+    def authenticator(self, server, session, envelope, mechanism, auth_data):
+        fail_nothandled = AuthResult(success=False, handled=False)
+        if mechanism not in ("LOGIN", "PLAIN"):
+            _logger.warning(f"Unsupported mechanism {mechanism}")
+            return fail_nothandled
+        if not isinstance(auth_data, LoginPassword):
+            _logger.warning(f"Invalid auth data {auth_data}")
+            return fail_nothandled
+        return AuthResult(success=True, auth_data=auth_data)
+
+    async def handle_DATA(self, server: SMTP, session: Session, envelope: Envelope) -> str:
+        _logger.info(
+            f"handle_DATA from {envelope.mail_from} to {envelope.rcpt_tos}"
+        )
+        if not isinstance(session.auth_data, LoginPassword):
+            return '530 Authentication required'
+        if len(envelope.rcpt_tos) != 1:
+            return '500 Only one recipient allowed'
+        # Only one recipient allowed
+        to_mail = envelope.rcpt_tos[0]
+        # Parse email
+        msg = email.message_from_string(envelope.content)
+        content_list = []
+        if msg.is_multipart():
+            for part in msg.walk():
+                content_type = part.get_content_type()
+                payload = part.get_payload(decode=True)
+                if content_type not in ["text/plain", "text/html"]:
+                    _logger.warning(f"Skipping {content_type}")
+                    continue
+                if not payload:
+                    continue
+                content_list.append({
+                    "type": content_type,
+                    "value": payload.decode()
+                })
+        elif msg.get_content_type() in ["text/plain", "text/html"] and msg.get_payload(decode=True):
+            content_list.append({
+                "type": msg.get_content_type(),
+                "value": msg.get_payload(decode=True).decode()
+            })
+
+        if not content_list:
+            return '500 Invalid content'
+        body = max(
+            content_list,
+            key=lambda x: (x["type"] == "text/html", len(x["value"]))
+        )
+        from_name, _ = email.utils.parseaddr(
+            str(email.header.make_header(
+                email.header.decode_header(msg['From'])
+            ))
+        )
+        to_mail_map = {}
+        for to in str(email.header.make_header(
+            email.header.decode_header(msg['To'])
+        )).split(","):
+            tmp_to_name, tmp_to_mail = email.utils.parseaddr(to)
+            to_mail_map[tmp_to_mail] = tmp_to_name
+        _logger.info(f"Parsed mail from {from_name} to {to_mail_map}")
+        # Send mail
+        send_body = {
+            "from_name": from_name,
+            "to_name": to_mail_map.get(to_mail),
+            "to_mail": to_mail,
+            "subject": str(email.header.make_header(
+                email.header.decode_header(msg['Subject'])
+            )),
+            "is_html": body["type"] == "text/html",
+            "content": body["value"],
+        }
+        _logger.info(f"Send mail {send_body}")
+        try:
+            res = requests.post(
+                f"{settings.proxy_url}/api/send_mail",
+                json=send_body, headers={
+                    "Authorization": f"Bearer {session.auth_data.password.decode()}",
+                    "Content-Type": "application/json"
+                }
+            )
+            if res.status_code != 200:
+                _logger.error(
+                    "Failed to send mail "
+                    f"code=[{res.status_code}] text=[{res.text}]"
+                )
+                return f'500 Internal server error code=[{res.status_code}] text=[{res.text}]'
+        except Exception as e:
+            _logger.error(e)
+            return '500 Internal server error'
+
+        return '250 OK'
+
+
+settings = Settings()
+handler = CustomSMTPHandler()
+server = Controller(
+    handler,
+    port=settings.port,
+    auth_require_tls=False,
+    decode_data=True,
+    authenticator=handler.authenticator,
+    auth_exclude_mechanism=["DONT"]
+)
+
+
+async def start():
+    _logger.info(f"Starting server settings[{settings}]")
+    server.start()
+
+
+if __name__ == "__main__":
+    loop = asyncio.new_event_loop()
+    asyncio.set_event_loop(loop)
+    task = loop.create_task(start())
+    try:
+        loop.run_forever()
+    except KeyboardInterrupt:
+        _logger.info("Got KeyboardInterrupt, stopping")
+        server.stop()