{-# LANGUAGE DoAndIfThenElse #-}
{-# LANGUAGE RecordWildCards #-}
-module Main
+module Main (main)
where
-import Control.Concurrent.ParallelIO.Global (parallel, stopGlobalPool)
-import Control.Monad (when)
-import qualified Data.ByteString as BS
-import qualified Data.ByteString.UTF8 as BSU
+import Control.Concurrent.ParallelIO.Global (
+ parallelInterleaved,
+ stopGlobalPool )
+import qualified Data.ByteString.Char8 as BS (
+ hGetContents,
+ hPutStrLn,
+ lines,
+ null,
+ pack )
import Network.DNS (
Domain,
Resolver,
- ResolvConf(..),
+ ResolvConf( resolvTimeout ),
defaultResolvConf,
makeResolvSeed,
- withResolver)
-import Network.DNS.Lookup (lookupMX)
-import System.Directory (doesFileExist)
-import System.Exit (exitWith, ExitCode(..))
+ withResolver )
+import Network.DNS.Lookup ( lookupA, lookupMX )
import System.IO (
- Handle,
- IOMode( WriteMode ),
- hClose,
hFlush,
- openFile,
stdin,
- stdout)
-import Text.Regex.PCRE.Light (compile, match, utf8)
+ stdout )
-import CommandLine (Args(..), apply_args)
-import ExitCodes (exit_input_file_doesnt_exist)
-type Address = BSU.ByteString
+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 5
+
+-- | Resolver parameters. We increase the default timeout from 3 to 10
-- seconds.
resolv_conf :: ResolvConf
-resolv_conf = defaultResolvConf { resolvTimeout = 5 * 1000 * 1000 }
+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 BSU.fromString [ "aol.com",
- "comcast.net",
- "gmail.com",
- "msn.com",
- "yahoo.com",
- "verizon.net" ]
-
-validate_mx :: Resolver -> Domain -> IO Bool
+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.
+--
+-- 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
- Nothing -> return False
- _ -> return True
+ 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 "."
--- | Split an address into local/domain parts.
-parts :: Address -> (BSU.ByteString, BSU.ByteString)
-parts address = bytestring_split address '@'
+ is_null :: (Domain,Int) -> Bool
+ is_null (mx,prio) = mx == nullmx && prio == 0
--- | Check that the lengths of the local/domain parts are within spec.
-validate_length :: Address -> Bool
-validate_length address =
- (BSU.length localpart <= 64) && (BSU.length domain <= 255)
- where
- (localpart, domain) = parts address
-
--- | Validate an email address against a simple regex. This should
--- catch common addresses but disallows a lot of (legal) weird stuff.
-validate_regex :: Address -> Bool
-validate_regex address =
- case matches of
- Nothing -> False
- _ -> True
- where
- regex_str = "(\\w+)([\\w\\-\\.]*)@(([0-9a-zA-Z\\-]+\\.)+)[a-zA-Z]{2,4}"
- regex_bs = BSU.fromString regex_str
- regex = compile regex_bs [utf8]
- matches = match regex address []
-
--- | Validate the syntax of an email address by checking its length
--- and validating it against a simple regex.
-validate_syntax :: Address -> Bool
-validate_syntax address =
- (validate_length address) && (validate_regex address)
-
--- | Split a 'ByteString' @s@ at the first occurrence of @character@.
-bytestring_split :: BSU.ByteString -> Char -> (BSU.ByteString, BSU.ByteString)
-bytestring_split s character =
- (before, after)
- where
- break_func = (== character)
- (before, rest) = BSU.break break_func s
- after = BS.tail rest
+-- | Check whether the given domain has a valid A record.
+validate_a :: Resolver -> Domain -> IO Bool
+validate_a resolver domain
+ | domain `elem` common_domains = return True
+ | otherwise = do
+ result <- lookupA resolver domain
+ case result of
+ Right (_:_) -> return True
+ _ -> return False
-- | 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.
-validate :: Resolver -> Address -> IO (Address, Bool)
-validate resolver address = do
- let valid_syntax = validate_syntax address
+-- (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
- return (address, mx_result)
- else do
- return (address, False)
-
-
-append_handle_with_newline :: Handle -> BS.ByteString -> IO ()
-append_handle_with_newline h bs = do
- BS.hPutStr h bs
- BS.hPutStr h newline
- where
- newline = BSU.fromString "\n"
+ 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
+ Args{..} <- get_args
- input <- case input_file of
- Nothing -> BS.hGetContents stdin
- Just path -> do
- is_file <- doesFileExist path
- when (not is_file) $ do
- exitWith (ExitFailure exit_input_file_doesnt_exist)
- BS.readFile path
+ -- Split stdin into lines, which should result in a list of addresses.
+ input <- BS.hGetContents stdin
+ let addresses = BS.lines input
- output_handle <- case output_file of
- Nothing -> return stdout
- Just path -> openFile path WriteMode
-
- let addresses = BSU.lines input
+ -- And remove the empty ones.
let nonempty_addresses = filter (not . BS.null) addresses
rs <- makeResolvSeed resolv_conf
- withResolver rs $ \resolver -> do
- let actions = map (validate resolver) nonempty_addresses
- results <- parallel actions
- stopGlobalPool
- let good_pairs = filter snd results
- mapM_ ((append_handle_with_newline output_handle) . fst) good_pairs
- hFlush output_handle
- hClose output_handle
+ let validate' addr = withResolver rs $ \resolver ->
+ validate resolver accept_a rfc5322 addr
+
+ -- Construct a list of [IO (Address, Bool)]. The withResolver calls
+ -- are the ones that should be run in parallel.
+ let actions = map validate' nonempty_addresses
+
+ -- Run the lookup actions in parallel.
+ results <- parallelInterleaved actions
+
+ -- Filter the bad ones.
+ let valid_results = filter snd results
+
+ -- Output the results.
+ let valid_addresses = map fst valid_results
+ mapM_ (BS.hPutStrLn stdout) valid_addresses
+
+ stopGlobalPool
+ hFlush stdout
projects / email-validator.git / blobdiff