improve email validation

blossomtune_gradio/federation.py

@@ -6,6 +6,7 @@ from datetime import datetime
 
 from blossomtune_gradio import config as cfg
 from blossomtune_gradio import mail
+from blossomtune_gradio import util
 from blossomtune_gradio.settings import settings
 
 
@@ -45,7 +46,7 @@ def check_participant_status(pid_to_check: str, email: str, activation_code: str
     if result is None:
         if activation_code:
             return (False, settings.get_text("activation_invalid_md"))
-        if not email or "@" not in email:
+        if not util.validate_email(email):
             return (False, settings.get_text("invalid_email_md"))
 
         with sqlite3.connect(cfg.DB_PATH) as conn:

blossomtune_gradio/util.py

@@ -1,4 +1,39 @@
+import re
+import dns.resolver
+
+
+def validate_email(email_address: str) -> bool:
+    """
+    Validates an email address using regex for format and
+    DNS for domain's MX record.
+
+    Args:
+        email_address (str): The email address to validate.
+
+    Returns:
+        bool: True if the email is syntactically valid and
+              the domain has an MX record, False otherwise.
+    """
+    # Regex validation for basic format
+    regex = r"[^@]+@[^@]+\.[^@]+"
+    if not re.match(regex, email_address):
+        return False
+
+    # DNS MX record validation
+    try:
+        domain = email_address.rsplit("@", 1)[-1]
+        dns.resolver.query(domain, "MX")
+        return True
+    except (dns.resolver.NoAnswer, dns.resolver.NXDOMAIN, IndexError):
+        return False
+    except Exception as e:
+        print(f"An unexpected error occurred: {e}")
+        return False
+
+
 def strtobool(value: str) -> bool:
+    if not value:
+        return False
     value = value.lower()
     if value in ("y", "yes", "on", "1", "true", "t"):
         return True

pyproject.toml

@@ -68,6 +68,7 @@ convention = "google"  # Accepts: "google", "numpy", or "pep257".
 
 [dependency-groups]
 dev = [
+    "dnspython>=2.8.0",
     "pytest>=8.4.1",
     "pytest-mock>=3.15.1",
 ]

tests/test_util.py

@@ -0,0 +1,74 @@
+import pytest
+import dns.resolver
+from unittest.mock import MagicMock
+
+from blossomtune_gradio.util import validate_email, strtobool
+
+
+def test_validate_email_valid(monkeypatch):
+    """Tests a syntactically valid email with an existing MX record."""
+    # Mock the dns.resolver.query to return a successful result.
+    mock_query = MagicMock()
+    monkeypatch.setattr(dns.resolver, "query", mock_query)
+
+    email = "test@google.com"
+    assert validate_email(email) is True
+    # Verify that the query function was called with the correct arguments.
+    mock_query.assert_called_once_with("google.com", "MX")
+
+
+def test_validate_email_invalid_format():
+    """Tests an email with an invalid regex format."""
+    assert validate_email("invalid-email") is False
+    assert validate_email("user@.com") is False
+    assert validate_email("@domain.com") is False
+
+
+def test_validate_email_no_mx_record(monkeypatch):
+    """Tests a domain that exists but has no MX record."""
+    # Mock the dns.resolver.query to raise a NoAnswer exception.
+    mock_query = MagicMock(side_effect=dns.resolver.NoAnswer)
+    monkeypatch.setattr(dns.resolver, "query", mock_query)
+
+    email = "user@example.com"
+    assert validate_email(email) is False
+    mock_query.assert_called_once_with("example.com", "MX")
+
+
+def test_validate_email_non_existent_domain(monkeypatch):
+    """Tests a domain that does not exist."""
+    # Mock the dns.resolver.query to raise an NXDOMAIN exception.
+    mock_query = MagicMock(side_effect=dns.resolver.NXDOMAIN)
+    monkeypatch.setattr(dns.resolver, "query", mock_query)
+
+    email = "user@not-a-real-domain-123.com"
+    assert validate_email(email) is False
+    mock_query.assert_called_once_with("not-a-real-domain-123.com", "MX")
+
+
+@pytest.mark.parametrize(
+    "value, expected",
+    [
+        ("y", True),
+        ("yes", True),
+        ("on", True),
+        ("1", True),
+        ("true", True),
+        ("t", True),
+        ("Y", True),
+        ("YES", True),
+        ("On", True),
+        ("0", False),
+        ("n", False),
+        ("off", False),
+        ("false", False),
+        ("f", False),
+        ("no", False),
+        ("anything else", False),
+        ("", False),
+        (None, False),  # Test with None to ensure it doesn't crash
+    ],
+)
+def test_strtobool(value, expected):
+    """Tests the strtobool function with various inputs."""
+    assert strtobool(value) == expected

uv.lock

@@ -241,6 +241,7 @@ dependencies = [
 
 [package.dev-dependencies]
 dev = [
+    { name = "dnspython" },
     { name = "pytest" },
     { name = "pytest-mock" },
 ]
@@ -261,6 +262,7 @@ requires-dist = [
 
 [package.metadata.requires-dev]
 dev = [
+    { name = "dnspython", specifier = ">=2.8.0" },
     { name = "pytest", specifier = ">=8.4.1" },
     { name = "pytest-mock", specifier = ">=3.15.1" },
 ]
@@ -637,6 +639,15 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/c9/7a/cef76fd8438a42f96db64ddaa85280485a9c395e7df3db8158cfec1eee34/dill-0.3.8-py3-none-any.whl", hash = "sha256:c36ca9ffb54365bdd2f8eb3eff7d2a21237f8452b57ace88b1ac615b7e815bd7", size = 116252, upload-time = "2024-01-27T23:42:14.239Z" },
 ]
 
+[[package]]
+name = "dnspython"
+version = "2.8.0"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/8c/8b/57666417c0f90f08bcafa776861060426765fdb422eb10212086fb811d26/dnspython-2.8.0.tar.gz", hash = "sha256:181d3c6996452cb1189c4046c61599b84a5a86e099562ffde77d26984ff26d0f", size = 368251, upload-time = "2025-09-07T18:58:00.022Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/ba/5a/18ad964b0086c6e62e2e7500f7edc89e3faa45033c71c1893d34eed2b2de/dnspython-2.8.0-py3-none-any.whl", hash = "sha256:01d9bbc4a2d76bf0db7c1f729812ded6d912bd318d3b1cf81d30c0f845dbf3af", size = 331094, upload-time = "2025-09-07T18:57:58.071Z" },
+]
+
 [[package]]
 name = "evaluate"
 version = "0.4.5"