{-# LANGUAGE DoAndIfThenElse #-}
{-# LANGUAGE RecordWildCards #-}
-module Main
+module Main (main)
where
import Control.Concurrent.ParallelIO.Global (
parallelInterleaved,
- stopGlobalPool)
-import Control.Monad (unless)
+ stopGlobalPool )
import qualified Data.ByteString.Char8 as BS (
hGetContents,
hPutStrLn,
lines,
null,
- pack,
- readFile)
+ pack )
import Network.DNS (
Domain,
Resolver,
- ResolvConf(..),
+ ResolvConf( resolvTimeout ),
defaultResolvConf,
makeResolvSeed,
- withResolver)
-import Network.DNS.Lookup (lookupA, lookupMX)
-import System.Directory (doesFileExist)
-import System.Exit (exitWith, ExitCode(..))
+ withResolver )
+import Network.DNS.Lookup ( lookupA, lookupMX )
import System.IO (
- IOMode( WriteMode ),
- hClose,
hFlush,
- openFile,
stdin,
- stdout)
+ stdout )
-import CommandLine (Args(..), apply_args)
-import EmailAddress
-import ExitCodes (exit_input_file_doesnt_exist)
+import CommandLine (
+ Args( Args, accept_a, rfc5322 ),
+ get_args )
+import EmailAddress(
+ Address,
+ parts,
+ validate_syntax )
-- | Resolver parameters. We increase the default timeout from 3 to 10
resolv_conf :: ResolvConf
resolv_conf = defaultResolvConf { resolvTimeout = 10 * 1000 * 1000 }
--- | A list of common domains, there's no need to waste MX lookups
--- on these.
+-- | A list of common domains, there's no need to waste MX lookups on
+-- these. This is a very limited list; I don't want to be in the
+-- business of monitoring a million domains for MX record updates.
common_domains :: [Domain]
common_domains = map BS.pack [ "aol.com",
"comcast.net",
+ "cox.net",
"gmail.com",
+ "gmx.de",
+ "googlemail.com",
+ "hotmail.com",
+ "icloud.com",
+ "live.com",
+ "me.com",
"msn.com",
+ "outlook.com",
+ "proton.me",
+ "protonmail.ch",
+ "protonmail.com",
"yahoo.com",
"verizon.net" ]
-- | Check whether the given domain has a valid MX record.
-validate_mx :: Resolver -> Domain -> IO Bool
+--
+-- NULLMX (RFC7505) records consisting of a single period must not
+-- be accepted. Moreover, the existence of a NULLMX must be reported
+-- back to the caller because the whole point of a NULLMX is that
+-- its existence should preempt an @A@ record check. We abuse the
+-- return type for this, and return @Nothing@ in the event of a
+-- NULLMX. Otherwise we return @Just True@ or @Just False@ to
+-- indicate the existence (or not) of MX records.
+--
+-- RFC7505 states that a domain MUST NOT have any other MX records
+-- if it has a NULLMX record. We enforce this. If you have a NULLMX
+-- record and some other MX record, we consider the set invalid.
+--
+validate_mx :: Resolver -> Domain -> IO (Maybe Bool)
validate_mx resolver domain
- | domain `elem` common_domains = return True
+ | domain `elem` common_domains = return $ Just True
| otherwise = do
result <- lookupMX resolver domain
case result of
- -- A list of one or more elements?
- Right (_:_) -> return True
- _ -> return False
-
+ Left _ ->
+ return $ Just False
+ Right mxs ->
+ case mxs of
+ [] -> return $ Just False
+ _ -> if any (is_null) mxs
+ then return Nothing
+ else return $ Just True
+ where
+ nullmx :: Domain
+ nullmx = BS.pack "."
+
+ is_null :: (Domain,Int) -> Bool
+ is_null (mx,prio) = mx == nullmx && prio == 0
-- | Check whether the given domain has a valid A record.
validate_a :: Resolver -> Domain -> IO Bool
-- | Validate an email address by doing some simple syntax checks and
--- (if those fail) an MX lookup. We don't count an A record as a mail
--- exchanger.
+-- (if those fail) an MX lookup. We don't count an @A@ record as a mail
+-- exchanger unless @accept_a@ is True. And even then, the existence
+-- of a NULLMX record will preclude the acceptance of an @A@ record.
+-- The domain @example.com@ is a great test case for this behavior.
validate :: Resolver -> Bool -> Bool -> Address -> IO (Address, Bool)
validate resolver accept_a rfc5322 address = do
let valid_syntax = validate_syntax rfc5322 address
if valid_syntax then do
let (_,domain) = parts address
mx_result <- validate_mx resolver domain
- if mx_result
- then return (address, True)
- else
- if accept_a
- then do
- a_result <- validate_a resolver domain
- return (address, a_result)
- else
- return (address, False)
- else
- return (address, False)
-
+ case mx_result of
+ Nothing ->
+ -- NULLMX, don't fall back to 'A' records under any
+ -- circumstances.
+ return (address, False)
+ Just mxr ->
+ if mxr
+ then return (address, True)
+ else
+ if accept_a
+ then do
+ a_result <- validate_a resolver domain
+ return (address, a_result)
+ else
+ return (address, False)
+ else
+ return (address, False)
main :: IO ()
main = do
- Args{..} <- apply_args
-
- -- Get the input from either stdin, or the file given on the command
- -- line.
- input <- case input_file of
- Nothing -> BS.hGetContents stdin
- Just path -> do
- is_file <- doesFileExist path
- unless is_file $
- exitWith (ExitFailure exit_input_file_doesnt_exist)
- BS.readFile path
-
- -- Do the same for the output handle and stdout.
- output_handle <- case output_file of
- Nothing -> return stdout
- Just path -> openFile path WriteMode
-
- -- Split the input into lines.
+ Args{..} <- get_args
+
+ -- Split stdin into lines, which should result in a list of addresses.
+ input <- BS.hGetContents stdin
let addresses = BS.lines input
-- And remove the empty ones.
-- Output the results.
let valid_addresses = map fst valid_results
- _ <- mapM (BS.hPutStrLn output_handle) valid_addresses
+ mapM_ (BS.hPutStrLn stdout) valid_addresses
stopGlobalPool
-
- -- Clean up. It's safe to try to close stdout.
- hFlush output_handle
- hClose output_handle
+ hFlush stdout
projects / email-validator.git / blobdiff