Update to pass the flake8 hook

Make the necessary changes to pass the `flake8` pre-commit hook. This
is almost exclusively to satisfy the flake8-docstring plugin.

src/trustymail/cli.py

@@ -1,4 +1,5 @@
 """trustymail: A tool for scanning DNS mail records for evaluating security.
+
 Usage:
   trustymail (INPUT ...) [options]
   trustymail (INPUT ...) [--output=OUTFILE] [--timeout=TIMEOUT] [--smtp-timeout=TIMEOUT] [--smtp-localhost=HOSTNAME] [--smtp-ports=PORTS] [--no-smtp-cache] [--mx] [--starttls] [--spf] [--dmarc] [--debug] [--json] [--dns=HOSTNAMES] [--psl-filename=FILENAME] [--psl-read-only]
@@ -65,6 +66,7 @@
 
 
 def main():
+    """Perform a trustymail scan using the provided options."""
     args = docopt.docopt(__doc__, version=__version__)
 
     # Monkey patching trustymail to make it cache the PSL where we want
@@ -163,6 +165,7 @@ def main():
 
 
 def write(content, out_file):
+    """Write the provided content to a file after ensuring all intermediate directories exist."""
     parent = os.path.dirname(out_file)
     if parent != "":
         mkdir_p(parent)
@@ -175,6 +178,7 @@ def write(content, out_file):
 # mkdir -p in python, from:
 # http://stackoverflow.com/questions/600268/mkdir-p-functionality-in-python
 def mkdir_p(path):
+    """Make a directory and all intermediate directories in its path."""
     try:
         os.makedirs(path)
     except OSError as exc:  # Python >2.5

src/trustymail/domain.py

@@ -1,3 +1,5 @@
+"""Provide a data model for domains and some utility functions."""
+
 # Standard Python Libraries
 from collections import OrderedDict
 from datetime import datetime, timedelta
@@ -12,7 +14,7 @@
 
 def get_psl():
     """
-    Gets the Public Suffix List - either new, or cached in the CWD for 24 hours
+    Get the Public Suffix List - either new, or cached in the CWD for 24 hours.
 
     Returns
     -------
@@ -42,14 +44,14 @@ def download_psl():
 
 
 def get_public_suffix(domain):
-    """Returns the public suffix of a given domain"""
+    """Return the public suffix of a given domain."""
     public_list = get_psl()
 
     return public_list.get_public_suffix(domain)
 
 
 def format_list(record_list):
-    """Format a list into a string to increase readability in CSV"""
+    """Format a list into a string to increase readability in CSV."""
     # record_list should only be a list, not an integer, None, or
     # anything else.  Thus this if clause handles only empty
     # lists.  This makes a "null" appear in the JSON output for
@@ -61,7 +63,9 @@ def format_list(record_list):
 
 
 class Domain:
-    base_domains: Dict[str, Domain] = {}
+    """Store information about a domain."""
+
+    base_domains: Dict[str, "Domain"] = {}
 
     def __init__(
         self,
@@ -73,6 +77,7 @@ def __init__(
         smtp_cache,
         dns_hostnames,
     ):
+        """Retrieve information about a given domain name."""
         self.domain_name = domain_name.lower()
 
         self.base_domain_name = get_public_suffix(self.domain_name)
@@ -137,15 +142,13 @@ def __init__(
         self.ports_tested = set()
 
     def has_mail(self):
+        """Check if there are any mail servers associated with this domain."""
         if self.mail_servers is not None:
             return len(self.mail_servers) > 0
         return None
 
     def has_supports_smtp(self):
-        """
-        Returns True if any of the mail servers associated with this
-        domain are listening and support SMTP.
-        """
+        """Check if any of the mail servers associated with this domain are listening and support SMTP."""
         result = None
         if len(self.starttls_results) > 0:
             result = (
@@ -160,10 +163,7 @@ def has_supports_smtp(self):
         return result
 
     def has_starttls(self):
-        """
-        Returns True if any of the mail servers associated with this
-        domain are listening and support STARTTLS.
-        """
+        """Check if any of the mail servers associated with this domain are listening and support STARTTLS."""
         result = None
         if len(self.starttls_results) > 0:
             result = (
@@ -178,16 +178,19 @@ def has_starttls(self):
         return result
 
     def has_spf(self):
+        """Check if this domain has any Sender Policy Framework records."""
         if self.spf is not None:
             return len(self.spf) > 0
         return None
 
     def has_dmarc(self):
+        """Check if this domain has a Domain-based Message Authentication, Reporting, and Conformance record."""
         if self.dmarc is not None:
             return len(self.dmarc) > 0
         return None
 
     def add_mx_record(self, record):
+        """Add a mail server record for this domain."""
         if self.mx_records is None:
             self.mx_records = []
         self.mx_records.append(record)
@@ -198,30 +201,35 @@ def add_mx_record(self, record):
         self.mail_servers.append(record.exchange.to_text().rstrip(".").lower())
 
     def parent_has_dmarc(self):
+        """Check if a domain or its parent has a Domain-based Message Authentication, Reporting, and Conformance record."""
         ans = self.has_dmarc()
         if self.base_domain:
             ans = self.base_domain.has_dmarc()
         return ans
 
     def parent_dmarc_dnssec(self):
+        """Get this domain or its parent's DMARC DNSSEC information."""
         ans = self.dmarc_dnssec
         if self.base_domain:
             ans = self.base_domain.dmarc_dnssec
         return ans
 
     def parent_valid_dmarc(self):
+        """Check if this domain or its parent have a valid DMARC record."""
         ans = self.valid_dmarc
         if self.base_domain:
             return self.base_domain.valid_dmarc
         return ans
 
     def parent_dmarc_results(self):
+        """Get this domain or its parent's DMARC information."""
         ans = format_list(self.dmarc)
         if self.base_domain:
             ans = format_list(self.base_domain.dmarc)
         return ans
 
     def get_dmarc_policy(self):
+        """Get this domain or its parent's DMARC policy."""
         ans = self.dmarc_policy
         # If the policy was never set, or isn't in the list of valid
         # policies, check the parents.
@@ -239,6 +247,7 @@ def get_dmarc_policy(self):
         return ans
 
     def get_dmarc_subdomain_policy(self):
+        """Get this domain or its parent's DMARC subdomain policy."""
         ans = self.dmarc_subdomain_policy
         # If the policy was never set, or isn't in the list of valid
         # policies, check the parents.
@@ -250,41 +259,47 @@ def get_dmarc_subdomain_policy(self):
         return ans
 
     def get_dmarc_pct(self):
+        """Get this domain or its parent's DMARC percentage information."""
         ans = self.dmarc_pct
         if not ans and self.base_domain:
             # Check the parents
             ans = self.base_domain.get_dmarc_pct()
         return ans
 
     def get_dmarc_has_aggregate_uri(self):
+        """Get this domain or its parent's DMARC aggregate URI."""
         ans = self.dmarc_has_aggregate_uri
         # If there are no aggregate URIs then check the parents.
         if not ans and self.base_domain:
             ans = self.base_domain.get_dmarc_has_aggregate_uri()
         return ans
 
     def get_dmarc_has_forensic_uri(self):
+        """Check if this domain or its parent have a DMARC forensic URI."""
         ans = self.dmarc_has_forensic_uri
         # If there are no forensic URIs then check the parents.
         if not ans and self.base_domain:
             ans = self.base_domain.get_dmarc_has_forensic_uri()
         return ans
 
     def get_dmarc_aggregate_uris(self):
+        """Get this domain or its parent's DMARC aggregate URIs."""
         ans = self.dmarc_aggregate_uris
         # If there are no aggregate URIs then check the parents.
         if not ans and self.base_domain:
             ans = self.base_domain.get_dmarc_aggregate_uris()
         return ans
 
     def get_dmarc_forensic_uris(self):
+        """Get this domain or its parent's DMARC forensic URIs."""
         ans = self.dmarc_forensic_uris
         # If there are no forensic URIs then check the parents.
         if not ans and self.base_domain:
             ans = self.base_domain.get_dmarc_forensic_uris()
         return ans
 
     def generate_results(self):
+        """Generate the results for this domain."""
         if len(self.starttls_results.keys()) == 0:
             domain_supports_smtp = None
             domain_supports_starttls = None

src/trustymail/trustymail.py

@@ -1,3 +1,5 @@
+"""Functions to check a domain's configuration for trustworthy mail."""
+
 # Standard Python Libraries
 from collections import OrderedDict
 import csv
@@ -27,6 +29,7 @@
 
 
 def domain_list_from_url(url):
+    """Get a list of domains from a provided URL."""
     if not url:
         return []
 
@@ -38,6 +41,7 @@ def domain_list_from_url(url):
 
 
 def domain_list_from_csv(csv_file):
+    """Get a list of domains from a provided CSV file."""
     domain_list = list(csv.reader(csv_file, delimiter=","))
 
     # Check the headers for the word domain - use that column.
@@ -61,7 +65,9 @@ def domain_list_from_csv(csv_file):
 
 
 def check_dnssec(domain, domain_name, record_type):
-    """Checks whether the domain has a record of type that is protected
+    """Test to see if a DNSSEC record is valid and correct.
+
+    Checks a domain for DNSSEC whether the domain has a record of type that is protected
     by DNSSEC or NXDOMAIN or NoAnswer that is protected by DNSSEC.
 
     TODO: Probably does not follow redirects (CNAMEs).  Should work on
@@ -82,6 +88,7 @@ def check_dnssec(domain, domain_name, record_type):
 
 
 def mx_scan(resolver, domain):
+    """Scan a domain to see if it has any mail servers."""
     try:
         if domain.mx_records is None:
             domain.mx_records = []
@@ -426,9 +433,10 @@ def get_spf_record_text(resolver, domain_name, domain, follow_redirect=False):
 
 
 def spf_scan(resolver, domain):
-    """Scan a domain to see if it supports SPF.  If the domain has an SPF
-    record, verify that it properly handles mail sent from an IP known
-    not to be listed in an MX record for ANY domain.
+    """Scan a domain to see if it supports SPF.
+
+    If the domain has an SPF record, verify that it properly handles mail sent from
+    an IP known not to be listed in an MX record for ANY domain.
 
     Parameters
     ----------
@@ -460,7 +468,7 @@ def spf_scan(resolver, domain):
 
 def parse_dmarc_report_uri(uri):
     """
-    Parses a DMARC Reporting (i.e. ``rua``/``ruf)`` URI
+    Parse a DMARC Reporting (i.e. ``rua``/``ruf)`` URI.
 
     Notes
     -----
@@ -492,6 +500,7 @@ def parse_dmarc_report_uri(uri):
 
 
 def dmarc_scan(resolver, domain):
+    """Scan a domain to see if it supports DMARC."""
     # dmarc records are kept in TXT records for _dmarc.domain_name.
     try:
         if domain.dmarc is None:
@@ -773,6 +782,7 @@ def dmarc_scan(resolver, domain):
 
 
 def find_host_from_ip(resolver, ip_addr):
+    """Find the host name for a given IP address."""
     # Use TCP, since we care about the content and correctness of the records
     # more than whether their records fit in a single UDP packet.
     hostname, _ = resolver.query(dns.reversename.from_address(ip_addr), "PTR", tcp=True)
@@ -789,6 +799,7 @@ def scan(
     scan_types,
     dns_hostnames,
 ):
+    """Parse a domain's DNS information for mail related records."""
     #
     # Configure the dnspython library
     #
@@ -878,9 +889,10 @@ def scan(
 
 
 def handle_error(prefix, domain, error, syntax_error=False):
-    """Handle an error by logging via the Python logging library and
-    recording it in the debug_info or syntax_error members of the
-    trustymail.Domain object.
+    """Handle the provided error by logging a message and storing it in the Domain object.
+
+    Logging is performed via the Python logging library and recording it in the
+    debug_info or syntax_error members of the trustymail.Domain object.
 
     Since the "Debug Info" and "Syntax Error" fields in the CSV output
     of trustymail come directly from the debug_info and syntax_error
@@ -946,11 +958,12 @@ def handle_error(prefix, domain, error, syntax_error=False):
 
 
 def handle_syntax_error(prefix, domain, error):
-    """Convenience method for handle_error"""
+    """Handle a syntax error by passing it to handle_error()."""
     handle_error(prefix, domain, error, syntax_error=True)
 
 
 def generate_csv(domains, file_name):
+    """Generate a CSV file with the given domain information."""
     with open(file_name, "w", encoding="utf-8", newline="\n") as output_file:
         writer = csv.DictWriter(
             output_file, fieldnames=domains[0].generate_results().keys()
@@ -965,6 +978,7 @@ def generate_csv(domains, file_name):
 
 
 def generate_json(domains):
+    """Generate a JSON string with the given domain information."""
     output = []
     for domain in domains:
         output.append(domain.generate_results())
@@ -974,6 +988,7 @@ def generate_json(domains):
 
 # Taken from pshtt to keep formatting similar
 def format_datetime(obj):
+    """Format the provided datetime information."""
     if isinstance(obj, datetime.date):
         return obj.isoformat()
     elif isinstance(obj, str):
@@ -983,7 +998,7 @@ def format_datetime(obj):
 
 
 def remove_quotes(txt_record):
-    """Remove double quotes and contatenate strings in a DNS TXT record
+    """Remove double quotes and contatenate strings in a DNS TXT record.
 
     A DNS TXT record can contain multiple double-quoted strings, and
     in that case the client has to remove the quotes and concatenate the

tests/test_trustymail.py

@@ -1,7 +1,11 @@
+"""Tests for the trustymail module."""
 # Standard Python Libraries
 import unittest
 
 
 class TestLiveliness(unittest.TestCase):
+    """Test the liveliness of a domain."""
+
     def test_domain_list_parsing(self):
+        """Test that a domain list is correctly parsed."""
         pass