{-# LANGUAGE DoAndIfThenElse #-}
{-# LANGUAGE RecordWildCards #-}
-module Main
+module Main (main)
where
-import Control.Concurrent.ParallelIO.Global (parallel, stopGlobalPool)
-import Control.Monad (unless)
-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 (lookupA, 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)
+ 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 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" ]
+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
- 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 "."
+ 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
| otherwise = do
result <- lookupA resolver domain
case result of
- Nothing -> return False
- _ -> return True
+ 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 -> Bool -> Address -> IO (Address, Bool)
-validate resolver accept_a 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
- 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)
-
-
--- | Append a ByteString to a file Handle, followed by a newline.
-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
-
- -- 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.
- let addresses = BSU.lines input
+ 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.
let nonempty_addresses = filter (not . BS.null) addresses
rs <- makeResolvSeed resolv_conf
- withResolver rs $ \resolver -> do
- -- Construst a list of [IO (Address, Bool)]
- let actions = map (validate resolver accept_a) nonempty_addresses
- -- And compute them in parallel.
- results <- parallel actions
- stopGlobalPool
- -- Find the pairs with a True in the second position.
- let good_pairs = filter snd results
- -- And output the results.
- mapM_ ((append_handle_with_newline output_handle) . fst) good_pairs
-
- -- Clean up. It's safe to try to close stdout.
- 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