smtprd-ng/tests/test_smtprd_ng.py

#     SMTP forwarding relay daemon with signing and encryption
#
#     Copyright (C) 2024  F. Brandes (additions to original code)
#
#     This program is free software: you can redistribute it and/or modify
#     it under the terms of the GNU Affero General Public License as
#     published by the Free Software Foundation, either version 3 of the
#     License, or (at your option) any later version.
#
#     This program is distributed in the hope that it will be useful,
#     but WITHOUT ANY WARRANTY; without even the implied warranty of
#     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#     GNU Affero General Public License for more details.
#
#     You should have received a copy of the GNU Affero General Public License
#     along with this program.  If not, see <http://www.gnu.org/licenses/>.

"""
Tests for smtprd_ng
"""
# pylint: disable=protected-access

import configparser
import email
import email.message
from pathlib import Path

import pytest
from M2Crypto import BIO, SMIME, X509

from smtprd_ng import smtprd


def config() -> smtprd.ClientConfig:
    """Return method for settings used here in test"""
    cfg = smtprd.ClientConfig(
        hostname="localhost",
        port=1234,
        username="user",
        password="pass",
        use_tls=False,
        start_tls=False,
        sender="sender",
        set_reply_to="",
        smime_cert=Path("tests", "signer.pem"),
        smime_cert_private=Path("tests", "privkey.pem"),
    )
    return cfg


def emails() -> smtprd.EmailConfig:
    """Return the email dict"""

    cfg = smtprd.EmailConfig(
        email_certs={"recipient": Path("tests", "signer.pem")},
    )
    return cfg


def test_config_from_config():
    """Test opening and reading the config file"""
    config_parser: configparser.ConfigParser = configparser.ConfigParser()
    with open(Path("config.example"), "r", encoding="utf8") as fp:
        config_parser.read_file(fp)
    cfg = smtprd.Config._from_config(config_parser)
    assert cfg.server.hostname == "localhost"
    assert cfg.client.port == 465
    assert cfg.client.smime_cert == ""
    assert cfg.client.use_tls is True
    assert cfg.client.password == ""


def test_config_from_ini():
    """Test parsing the config file and using fallbacks.
    This is mostly redundant to the above test"""
    cfg = smtprd.Config.from_ini(Path("config.example"))
    assert cfg.server.hostname == "localhost"
    assert cfg.client.port == 465
    assert cfg.client.smime_cert == ""
    assert cfg.client.use_tls is True


def test_read_from_file():
    """Test read_from_file function and the fallback"""
    existing_file = "config.example"
    non_existing_file = "abcde"
    empty_file = "tests/__init__.py"
    empty_string = ""
    assert smtprd.Config._read_from_file(existing_file) == "# [server]"
    with pytest.raises(Exception) as e_info:
        smtprd.Config._read_from_file(non_existing_file)
    assert e_info.typename == "OSError"
    assert str(e_info.value) == "File wasn't found: abcde"
    assert smtprd.Config._read_from_file(empty_string) == ""
    with pytest.raises(Exception) as e_info:
        smtprd.Config._read_from_file(empty_file)
    assert e_info.typename == "OSError"
    assert str(e_info.value) == "Empty file supplied: tests/__init__.py"


def test_config_emailcerts():
    """test retrieval of email/cert pair"""
    email_list = [("email1", "cert1"), ("email2", "cert2")]
    cfg = smtprd.Config._get_emails_and_certs(email_list)
    assert cfg["email2"] == "cert2"


def test_client_encrypt():
    """Test encryption. Keys were generated with
    openssl req -newkey rsa:1024 -nodes -x509 -days 365 -out signer.pem
    """

    client = smtprd.SMTPClient(config(), emails())
    encrypted = client._encrypt(b"abc", "subject", "recipient")
    lines = encrypted.decode().splitlines()
    # Test format of header
    assert lines[0] == "From: " + str(config().sender)
    assert lines[1] == "To: recipient"
    assert lines[2] == "Subject: " + "subject"
    assert lines[3] == "MIME-Version: 1.0"
    assert lines[4] == 'Content-Disposition: attachment; filename="smime.p7m"'
    assert (
        lines[5]
        == 'Content-Type: application/x-pkcs7-mime; smime-type=enveloped-data; name="smime.p7m"'
    )
    assert lines[6] == "Content-Transfer-Encoding: base64"
    # new line is important to seperate header from body
    assert lines[7] == ""
    assert (
        lines[8] == "MIIBTgYJKoZIhvcNAQcDoIIBPzCCATsCAQAxgfcwgfQCAQAwXTBFMQswCQYDVQQG"
    )

    # test decryption
    s = SMIME.SMIME()
    s.load_key(config().smime_cert_private, emails().email_certs["recipient"])
    buf = BIO.MemoryBuffer(encrypted)
    p7, _ = SMIME.smime_load_pkcs7_bio(buf)
    out = s.decrypt(p7)
    assert b"abc" in out


def test_client_sign():
    """Test signing"""
    client = smtprd.SMTPClient(config(), emails())
    message = email.message.EmailMessage()
    message.set_content("Test to sign")
    # header are needed, because email.message.Emailmessage will add a
    # newline between the boundary and the content if no header is found
    message.add_header("From", config().sender)
    message.add_header("To", "recipient")
    message.add_header("Subject", "Test")
    signed = client._sign(message)
    assert "This is an S/MIME signed message" in signed.decode()
    assert "Test to sign" in signed.decode()

    s = SMIME.SMIME()
    # Load the signer's cert.
    x509 = X509.load_cert(Path(config().smime_cert))
    sk = X509.X509_Stack()
    sk.push(x509)
    s.set_x509_stack(sk)
    # Load the signer's CA cert. In this case, because the signer's
    # cert is self-signed, it is the signer's cert itself.
    st = X509.X509_Store()
    st.load_info(str(config().smime_cert))
    s.set_x509_store(st)
    # Load the data, verify it.
    buf = BIO.MemoryBuffer(signed)
    p7, data = SMIME.smime_load_pkcs7_bio(buf)
    v = s.verify(p7, data)
    assert "Test to sign" in v.decode()


def test_cli_no_config_file():
    """Test whether config file parameter is supplied"""
    test_args = ["--config", ""]
    with pytest.raises(Exception) as e_info:
        smtprd.main(test_args)
    assert e_info.typename == "OSError"
    assert str(e_info.value) == "No config file supplied"


def test_cli_config_file_not_found():
    """Test whether config file is found"""
    test_args = ["--config", "doesnotexist.conf"]
    with pytest.raises(Exception) as e_info:
        smtprd.main(test_args)
    assert e_info.typename == "OSError"
    assert str(e_info.value) == "Config file not found: doesnotexist.conf"