second commit

env/lib/python3.11/site-packages/email_validator/deliverability.py

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+from typing import Any, List, Optional, Tuple, TypedDict
+
+import ipaddress
+
+from .exceptions_types import EmailUndeliverableError
+
+import dns.resolver
+import dns.exception
+
+
+def caching_resolver(*, timeout: Optional[int] = None, cache: Any = None, dns_resolver: Optional[dns.resolver.Resolver] = None) -> dns.resolver.Resolver:
+    if timeout is None:
+        from . import DEFAULT_TIMEOUT
+        timeout = DEFAULT_TIMEOUT
+    resolver = dns_resolver or dns.resolver.Resolver()
+    resolver.cache = cache or dns.resolver.LRUCache()
+    resolver.lifetime = timeout  # timeout, in seconds
+    return resolver
+
+
+DeliverabilityInfo = TypedDict("DeliverabilityInfo", {
+    "mx": List[Tuple[int, str]],
+    "mx_fallback_type": Optional[str],
+    "unknown-deliverability": str,
+}, total=False)
+
+
+def validate_email_deliverability(domain: str, domain_i18n: str, timeout: Optional[int] = None, dns_resolver: Optional[dns.resolver.Resolver] = None) -> DeliverabilityInfo:
+    # Check that the domain resolves to an MX record. If there is no MX record,
+    # try an A or AAAA record which is a deprecated fallback for deliverability.
+    # Raises an EmailUndeliverableError on failure. On success, returns a dict
+    # with deliverability information.
+
+    # If no dns.resolver.Resolver was given, get dnspython's default resolver.
+    # Override the default resolver's timeout. This may affect other uses of
+    # dnspython in this process.
+    if dns_resolver is None:
+        from . import DEFAULT_TIMEOUT
+        if timeout is None:
+            timeout = DEFAULT_TIMEOUT
+        dns_resolver = dns.resolver.get_default_resolver()
+        dns_resolver.lifetime = timeout
+    elif timeout is not None:
+        raise ValueError("It's not valid to pass both timeout and dns_resolver.")
+
+    deliverability_info: DeliverabilityInfo = {}
+
+    try:
+        try:
+            # Try resolving for MX records (RFC 5321 Section 5).
+            response = dns_resolver.resolve(domain, "MX")
+
+            # For reporting, put them in priority order and remove the trailing dot in the qnames.
+            mtas = sorted([(r.preference, str(r.exchange).rstrip('.')) for r in response])
+
+            # RFC 7505: Null MX (0, ".") records signify the domain does not accept email.
+            # Remove null MX records from the mtas list (but we've stripped trailing dots,
+            # so the 'exchange' is just "") so we can check if there are no non-null MX
+            # records remaining.
+            mtas = [(preference, exchange) for preference, exchange in mtas
+                    if exchange != ""]
+            if len(mtas) == 0:  # null MX only, if there were no MX records originally a NoAnswer exception would have occurred
+                raise EmailUndeliverableError(f"The domain name {domain_i18n} does not accept email.")
+
+            deliverability_info["mx"] = mtas
+            deliverability_info["mx_fallback_type"] = None
+
+        except dns.resolver.NoAnswer:
+            # If there was no MX record, fall back to an A or AAA record
+            # (RFC 5321 Section 5). Check A first since it's more common.
+
+            # If the A/AAAA response has no Globally Reachable IP address,
+            # treat the response as if it were NoAnswer, i.e., the following
+            # address types are not allowed fallbacks: Private-Use, Loopback,
+            # Link-Local, and some other obscure ranges. See
+            # https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml
+            # https://www.iana.org/assignments/iana-ipv6-special-registry/iana-ipv6-special-registry.xhtml
+            # (Issue #134.)
+            def is_global_addr(address: Any) -> bool:
+                try:
+                    ipaddr = ipaddress.ip_address(address)
+                except ValueError:
+                    return False
+                return ipaddr.is_global
+
+            try:
+                response = dns_resolver.resolve(domain, "A")
+
+                if not any(is_global_addr(r.address) for r in response):
+                    raise dns.resolver.NoAnswer  # fall back to AAAA
+
+                deliverability_info["mx"] = [(0, domain)]
+                deliverability_info["mx_fallback_type"] = "A"
+
+            except dns.resolver.NoAnswer:
+
+                # If there was no A record, fall back to an AAAA record.
+                # (It's unclear if SMTP servers actually do this.)
+                try:
+                    response = dns_resolver.resolve(domain, "AAAA")
+
+                    if not any(is_global_addr(r.address) for r in response):
+                        raise dns.resolver.NoAnswer
+
+                    deliverability_info["mx"] = [(0, domain)]
+                    deliverability_info["mx_fallback_type"] = "AAAA"
+
+                except dns.resolver.NoAnswer as e:
+                    # If there was no MX, A, or AAAA record, then mail to
+                    # this domain is not deliverable, although the domain
+                    # name has other records (otherwise NXDOMAIN would
+                    # have been raised).
+                    raise EmailUndeliverableError(f"The domain name {domain_i18n} does not accept email.") from e
+
+            # Check for a SPF (RFC 7208) reject-all record ("v=spf1 -all") which indicates
+            # no emails are sent from this domain (similar to a Null MX record
+            # but for sending rather than receiving). In combination with the
+            # absence of an MX record, this is probably a good sign that the
+            # domain is not used for email.
+            try:
+                response = dns_resolver.resolve(domain, "TXT")
+                for rec in response:
+                    value = b"".join(rec.strings)
+                    if value.startswith(b"v=spf1 "):
+                        if value == b"v=spf1 -all":
+                            raise EmailUndeliverableError(f"The domain name {domain_i18n} does not send email.")
+            except dns.resolver.NoAnswer:
+                # No TXT records means there is no SPF policy, so we cannot take any action.
+                pass
+
+    except dns.resolver.NXDOMAIN as e:
+        # The domain name does not exist --- there are no records of any sort
+        # for the domain name.
+        raise EmailUndeliverableError(f"The domain name {domain_i18n} does not exist.") from e
+
+    except dns.resolver.NoNameservers:
+        # All nameservers failed to answer the query. This might be a problem
+        # with local nameservers, maybe? We'll allow the domain to go through.
+        return {
+            "unknown-deliverability": "no_nameservers",
+        }
+
+    except dns.exception.Timeout:
+        # A timeout could occur for various reasons, so don't treat it as a failure.
+        return {
+            "unknown-deliverability": "timeout",
+        }
+
+    except EmailUndeliverableError:
+        # Don't let these get clobbered by the wider except block below.
+        raise
+
+    except Exception as e:
+        # Unhandled conditions should not propagate.
+        raise EmailUndeliverableError(
+            "There was an error while checking if the domain name in the email address is deliverable: " + str(e)
+        ) from e
+
+    return deliverability_info