From afc67c87e25638f19676491af9471b37a37d43a7 Mon Sep 17 00:00:00 2001
From: Kevin Jones <kevin@vcsjones.com>
Date: Wed, 15 Jul 2020 16:50:49 -0400
Subject: [PATCH] Make CreateHMAC(ReadOnlySpan<byte> key) public.

---
 .../ref/System.Security.Cryptography.Algorithms.cs |  1 +
 .../Security/Cryptography/IncrementalHash.cs       | 24 +++++++++++++++++++++-
 .../tests/IncrementalHashTests.cs                  | 15 +++++++++++++-
 3 files changed, 38 insertions(+), 2 deletions(-)

diff --git a/src/libraries/System.Security.Cryptography.Algorithms/ref/System.Security.Cryptography.Algorithms.cs b/src/libraries/System.Security.Cryptography.Algorithms/ref/System.Security.Cryptography.Algorithms.cs
index 339a77a..3ed7662 100644
--- a/src/libraries/System.Security.Cryptography.Algorithms/ref/System.Security.Cryptography.Algorithms.cs
+++ b/src/libraries/System.Security.Cryptography.Algorithms/ref/System.Security.Cryptography.Algorithms.cs
@@ -470,6 +470,7 @@ namespace System.Security.Cryptography
         public void AppendData(System.ReadOnlySpan<byte> data) { }
         public static System.Security.Cryptography.IncrementalHash CreateHash(System.Security.Cryptography.HashAlgorithmName hashAlgorithm) { throw null; }
         public static System.Security.Cryptography.IncrementalHash CreateHMAC(System.Security.Cryptography.HashAlgorithmName hashAlgorithm, byte[] key) { throw null; }
+        public static System.Security.Cryptography.IncrementalHash CreateHMAC(System.Security.Cryptography.HashAlgorithmName hashAlgorithm, System.ReadOnlySpan<byte> key) { throw null; }
         public void Dispose() { }
         public byte[] GetCurrentHash() { throw null; }
         public int GetCurrentHash(System.Span<byte> destination) { throw null; }
diff --git a/src/libraries/System.Security.Cryptography.Algorithms/src/System/Security/Cryptography/IncrementalHash.cs b/src/libraries/System.Security.Cryptography.Algorithms/src/System/Security/Cryptography/IncrementalHash.cs
index 5dadb52..acf433e 100644
--- a/src/libraries/System.Security.Cryptography.Algorithms/src/System/Security/Cryptography/IncrementalHash.cs
+++ b/src/libraries/System.Security.Cryptography.Algorithms/src/System/Security/Cryptography/IncrementalHash.cs
@@ -354,7 +354,29 @@ namespace System.Security.Cryptography
             return CreateHMAC(hashAlgorithm, (ReadOnlySpan<byte>)key);
         }
 
-        internal static IncrementalHash CreateHMAC(HashAlgorithmName hashAlgorithm, ReadOnlySpan<byte> key)
+        /// <summary>
+        /// Create an <see cref="IncrementalHash"/> for the Hash-based Message Authentication Code (HMAC)
+        /// algorithm utilizing the hash algorithm specified by <paramref name="hashAlgorithm"/>, and a
+        /// key specified by <paramref name="key"/>.
+        /// </summary>
+        /// <param name="hashAlgorithm">The name of the hash algorithm to perform within the HMAC.</param>
+        /// <param name="key">
+        ///     The secret key for the HMAC. The key can be any length, but a key longer than the output size
+        ///     of the hash algorithm specified by <paramref name="hashAlgorithm"/> will be hashed (using the
+        ///     algorithm specified by <paramref name="hashAlgorithm"/>) to derive a correctly-sized key. Therefore,
+        ///     the recommended size of the secret key is the output size of the hash specified by
+        ///     <paramref name="hashAlgorithm"/>.
+        /// </param>
+        /// <returns>
+        /// An <see cref="IncrementalHash"/> instance ready to compute the hash algorithm specified
+        /// by <paramref name="hashAlgorithm"/>.
+        /// </returns>
+        /// <exception cref="ArgumentException">
+        ///     <paramref name="hashAlgorithm"/>.<see cref="HashAlgorithmName.Name"/> is <c>null</c>, or
+        ///     the empty string.
+        /// </exception>
+        /// <exception cref="CryptographicException"><paramref name="hashAlgorithm"/> is not a known hash algorithm.</exception>
+        public static IncrementalHash CreateHMAC(HashAlgorithmName hashAlgorithm, ReadOnlySpan<byte> key)
         {
             if (string.IsNullOrEmpty(hashAlgorithm.Name))
                 throw new ArgumentException(SR.Cryptography_HashAlgorithmNameNullOrEmpty, nameof(hashAlgorithm));
diff --git a/src/libraries/System.Security.Cryptography.Algorithms/tests/IncrementalHashTests.cs b/src/libraries/System.Security.Cryptography.Algorithms/tests/IncrementalHashTests.cs
index 8b2b343..4b876c3 100644
--- a/src/libraries/System.Security.Cryptography.Algorithms/tests/IncrementalHashTests.cs
+++ b/src/libraries/System.Security.Cryptography.Algorithms/tests/IncrementalHashTests.cs
@@ -87,6 +87,19 @@ namespace System.Security.Cryptography.Algorithms.Tests
             }
         }
 
+        [Theory]
+        [MemberData(nameof(GetHMACs))]
+        public static void VerifyIncrementalHMAC_SpanKey(HMAC referenceAlgorithm, HashAlgorithmName hashAlgorithm)
+        {
+            using (referenceAlgorithm)
+            using (IncrementalHash incrementalHash = IncrementalHash.CreateHMAC(hashAlgorithm, new ReadOnlySpan<byte>(s_hmacKey)))
+            {
+                referenceAlgorithm.Key = s_hmacKey;
+
+                VerifyIncrementalResult(referenceAlgorithm, incrementalHash);
+            }
+        }
+
         private static void VerifyIncrementalResult(HashAlgorithm referenceAlgorithm, IncrementalHash incrementalHash)
         {
             byte[] referenceHash = referenceAlgorithm.ComputeHash(s_inputBytes);
@@ -471,7 +484,7 @@ namespace System.Security.Cryptography.Algorithms.Tests
         public static void VerifyGetCurrentHash_Digest(HashAlgorithm referenceAlgorithm, HashAlgorithmName hashAlgorithm)
         {
             referenceAlgorithm.Dispose();
-            
+
             using (IncrementalHash single = IncrementalHash.CreateHash(hashAlgorithm))
             using (IncrementalHash accumulated = IncrementalHash.CreateHash(hashAlgorithm))
             {
-- 
2.7.4