Source code for

Utilities for validating inputs related to user objects.

The validate_* methods in this file return simple messages that do not contain
user inputs - so these methods do not need to be escaped.
import logging
import re

import dns.resolver
from dns.exception import DNSException
from sqlalchemy import func
from typing_extensions import LiteralString

log = logging.getLogger(__name__)

# Email validity parameters
# Many words (and regexes) have been written about validating email addresses and there is no perfect answer on how it
# should be done. We choose to use the HTML5 spec (and corresponding regex) that engages in a "willful violation" of RFC
# 5322 to provide a reasonably good validation. Additionally, we allow Unicode characters in both the user and domain
# parts of the email by using re's '\w' character. Note that \w includes "word" characters but appears to exclude emoji
# characters, which should in fact be valid.
VALID_EMAIL_RE = re.compile(r"^[\w.!#$%&'*+\/=?^_`{|}~-]+@[\w](?:[\w-]{0,61}[\w])?(?:\.[\w](?:[\w-]{0,61}[\w])?)*$")

# Public name validity parameters
VALID_PUBLICNAME_RE = re.compile(r"^[a-z0-9._\-]+$")
VALID_PUBLICNAME_SUB = re.compile(r"[^a-z0-9._\-]")

# Password validity parameters

[docs]def validate_email_str(email): """Validates a string containing an email address.""" if not email: return "No email address was provided." if not (VALID_EMAIL_RE.match(email)): return "The format of the email address is not correct." elif len(email) > EMAIL_MAX_LEN: return "Email address cannot be more than %d characters in length." % EMAIL_MAX_LEN return ""
[docs]def validate_password_str(password): if not password or len(password) < PASSWORD_MIN_LEN: return "Use a password of at least %d characters." % PASSWORD_MIN_LEN return ""
[docs]def validate_publicname_str(publicname): """Validates a string containing a public username.""" if not publicname: return "Public name cannot be empty" if len(publicname) > PUBLICNAME_MAX_LEN: return "Public name cannot be more than %d characters in length." % (PUBLICNAME_MAX_LEN) if not (VALID_PUBLICNAME_RE.match(publicname)): return "Public name must contain only lower-case letters, numbers, '.', '_' and '-'." return ""
[docs]def validate_email(trans, email, user=None, check_dup=True, allow_empty=False, validate_domain=False): """ Validates the email format, also checks whether the domain is blocklisted in the disposable domains configuration. """ if (user and == email) or (email == "" and allow_empty): return "" message = validate_email_str(email) if not message and validate_domain: domain = extract_domain(email) message = validate_email_domain_name(domain) if ( not message and check_dup and trans.sa_session.query( .filter(func.lower( == email.lower()) .first() ): message = f"User with email '{email}' already exists." if not message: # If the allowlist is not empty filter out any domain not in the list and ignore blocklist. if is not None: domain = extract_domain(email) if domain not in message = "Please enter an allowed domain email address for this server." # If the blocklist is not empty filter out the disposable domains. elif is not None: domain = extract_domain(email, base_only=True) if domain in message = "Please enter your permanent email address." return message
[docs]def validate_email_domain_name(domain: str) -> LiteralString: message = "" try: dns.resolver.resolve(domain, "MX") except DNSException: try: # Per RFC 5321, try to fall back to the A record (implicit MX) for # the domain, see dns.resolver.resolve(domain, "A") except DNSException: message = "The email domain cannot be resolved." return message
[docs]def extract_domain(email, base_only=False): domain = email.rsplit("@", 1)[-1] parts = domain.split(".") if len(parts) > 2 and base_only: return (".").join(parts[-2:]) return domain
[docs]def validate_publicname(trans, publicname, user=None): """ Check that publicname respects the minimum and maximum string length, the allowed characters, and that the username is not taken already. """ if user and user.username == publicname: return "" message = validate_publicname_str(publicname) if message: return message if trans.sa_session.query( return "Public name is taken; please choose another." return ""
[docs]def transform_publicname(publicname): """ Transform publicname to respect the minimum and maximum string length, and the allowed characters. FILL_CHAR is used to extend or replace characters. """ # TODO: Enhance to allow generation of semi-random publicnnames e.g., when valid but taken if not publicname: raise ValueError("Public name cannot be empty") publicname = publicname.lower() publicname = re.sub(VALID_PUBLICNAME_SUB, FILL_CHAR, publicname) publicname = publicname[:PUBLICNAME_MAX_LEN] return publicname
[docs]def validate_password(trans, password, confirm): if password != confirm: return "Passwords do not match." return validate_password_str(password)