From 06201bc22e17465b74c4f1a3e109ca5a753b5143 Mon Sep 17 00:00:00 2001
From: Steffen Jost <jost@tcs.ifi.lmu.de>
Date: Tue, 12 Apr 2022 11:30:53 +0200
Subject: [PATCH] refactor(lms): better lms indentifiers and passwords

---
 src/Handler/Utils/LMS.hs | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/src/Handler/Utils/LMS.hs b/src/Handler/Utils/LMS.hs
index f56eeaaca..3cd3e3403 100644
--- a/src/Handler/Utils/LMS.hs
+++ b/src/Handler/Utils/LMS.hs
@@ -23,9 +23,8 @@ import Import
 import Handler.Utils
 import qualified Database.Esqueleto.Legacy as E
 
-import qualified Data.Text    as T
-import qualified Data.UUID    as UUID (toText) 
-import qualified Data.UUID.V4 as UUID (nextRandom)
+import Control.Monad.Random.Class (uniform)
+import Control.Monad.Trans.Random (evalRandTIO)
 
 -- generic Column names 
 csvLmsIdent   :: IsString a => a
@@ -101,11 +100,12 @@ lengthPassword = 8
 maxLmsUserIdentRetries :: Int 
 maxLmsUserIdentRetries = 27
 
-randomText :: MonadIO m => Int -> m Text 
-randomText n 
-  | n <=  8   = T.take n                     . UUID.toText <$> liftIO UUID.nextRandom
-  | n <= 32   = T.take n . T.filter ('-' ==) . UUID.toText <$> liftIO UUID.nextRandom
-  | otherwise = (<>) <$> randomText 32 <*> randomText (n - 32)
+-- | Generate Random Text of specified length using numbers and lower case letters plus supplied extra characters
+randomText :: MonadIO m => String -> Int -> m Text 
+randomText extra n = fmap pack . evalRandTIO . replicateM n $ uniform range 
+  where 
+    num_letters = ['0'..'9'] ++ ['a'..'z']
+    range       = extra ++ num_letters
 
 --TODO: consider using package elocrypt for user-friendly passwords here, licence requires mentioning of author, etc. though
 -- import qualified Data.Elocrypt as Elo
@@ -115,8 +115,10 @@ randomText n
 --     eopt = Elo.genOptions -- { genCapitals = False, genSpecials = False, genDigitis = True }
 
 randomLMSIdent :: MonadIO m => m LmsIdent 
-randomLMSIdent = LmsIdent <$> randomText lengthIdent
+randomLMSIdent = LmsIdent <$> randomText [] lengthIdent
 
 randomLMSpw :: MonadIO m => m Text 
-randomLMSpw = randomText lengthPassword
+randomLMSpw = randomText extra lengthPassword
+  where 
+    extra = "_-+*.:;=!?#"
   
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