Function validate_email_domain_literal

email_validator/syntax.py:765–822

(domain_literal: str)

def validate_email_domain_literal(domain_literal: str) -> DomainLiteralValidationResult:
    # This is obscure domain-literal syntax. Parse it and return
    # a compressed/normalized address.
    # RFC 5321 4.1.3 and RFC 5322 3.4.1.

    addr: Union[ipaddress.IPv4Address, ipaddress.IPv6Address]

    # Try to parse the domain literal as an IPv4 address.
    # There is no tag for IPv4 addresses, so we can never
    # be sure if the user intends an IPv4 address.
    if re.match(r"^[0-9\.]+$", domain_literal):
        try:
            addr = ipaddress.IPv4Address(domain_literal)
        except ValueError as e:
            raise EmailSyntaxError(f"The address in brackets after the @-sign is not valid: It is not an IPv4 address ({e}) or is missing an address literal tag.") from e

        # Return the IPv4Address object and the domain back unchanged.
        return {
            "domain_address": addr,
            "domain": f"[{addr}]",
        }

    # If it begins with "IPv6:" it's an IPv6 address.
    if domain_literal.startswith("IPv6:"):
        try:
            addr = ipaddress.IPv6Address(domain_literal[5:])
        except ValueError as e:
            raise EmailSyntaxError(f"The IPv6 address in brackets after the @-sign is not valid ({e}).") from e

        # Return the IPv6Address object and construct a normalized
        # domain literal.
        return {
            "domain_address": addr,
            "domain": f"[IPv6:{addr.compressed}]",
        }

    # Nothing else is valid.

    if ":" not in domain_literal:
        raise EmailSyntaxError("The part after the @-sign in brackets is not an IPv4 address and has no address literal tag.")

    # The tag (the part before the colon) has character restrictions,
    # but since it must come from a registry of tags (in which only "IPv6" is defined),
    # there's no need to check the syntax of the tag. See RFC 5321 4.1.2.

    # Check for permitted ASCII characters. This actually doesn't matter
    # since there will be an exception after anyway.
    bad_chars = {
        safe_character_display(c)
        for c in domain_literal
        if not DOMAIN_LITERAL_CHARS.match(c)
    }
    if bad_chars:
        raise EmailSyntaxError("The part after the @-sign contains invalid characters in brackets: " + ", ".join(sorted(bad_chars)) + ".")

    # There are no other domain literal tags.
    # https://www.iana.org/assignments/address-literal-tags/address-literal-tags.xhtml
    raise EmailSyntaxError("The part after the @-sign contains an invalid address literal tag in brackets.")