From d225c857d0f445a9842a197d9796925555e0ece5 Mon Sep 17 00:00:00 2001
From: Benjamin Barenblat <bbaren@google.com>
Date: Thu, 23 Aug 2018 12:24:31 -0400
Subject: Codec.Crypto.HKDF: Implement `hkdf` convenience function

---
 src/Codec/Crypto/HKDF.hs        | 6 +++++-
 tests/Codec/Crypto/HKDFTests.hs | 3 ++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/Codec/Crypto/HKDF.hs b/src/Codec/Crypto/HKDF.hs
index bd2d7a5..ac86bcc 100644
--- a/src/Codec/Crypto/HKDF.hs
+++ b/src/Codec/Crypto/HKDF.hs
@@ -14,7 +14,7 @@
 
 module Codec.Crypto.HKDF
   ( AssociatedData(AssociatedData), Salt(Salt), SecretKey(SecretKey), noSalt
-  , extract, expand
+  , hkdf, extract, expand
   ) where
 
 import qualified Data.ByteString as ByteString
@@ -31,6 +31,10 @@ import BTLS.Types
   , SecretKey(SecretKey), noSalt
   )
 
+-- | Computes an HKDF as specified by RFC 5869.
+hkdf :: Algorithm -> Salt -> AssociatedData -> Int -> SecretKey -> SecretKey
+hkdf md salt info outLen = expand md info outLen . extract md salt
+
 -- | Computes an HKDF pseudorandom key (PRK) as specified by RFC 5869.
 extract :: Algorithm -> Salt -> SecretKey -> SecretKey
 extract (Algorithm md) (Salt salt) (SecretKey secret) =
diff --git a/tests/Codec/Crypto/HKDFTests.hs b/tests/Codec/Crypto/HKDFTests.hs
index b3b2a28..44a41cd 100644
--- a/tests/Codec/Crypto/HKDFTests.hs
+++ b/tests/Codec/Crypto/HKDFTests.hs
@@ -91,7 +91,8 @@ testRFC5869 = testGroup "RFC 5869 examples"
   ]
   where
     t name hash ikm salt info len prk okm =
-      testGroup name [ testCase "extract" $ HKDF.extract hash salt ikm @?= prk
+      testGroup name [ testCase "hkdf" $ HKDF.hkdf hash salt info len ikm @?= okm
+                     , testCase "extract" $ HKDF.extract hash salt ikm @?= prk
                      , testCase "expand" $ HKDF.expand hash info len prk @?= okm
                      ]
 
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