3 files changed, 23 insertions, 6 deletions
diff --git a/crypto/src/tls/TlsUtilities.cs b/crypto/src/tls/TlsUtilities.cs
index 4cec13bae..52b554801 100644
--- a/crypto/src/tls/TlsUtilities.cs
+++ b/crypto/src/tls/TlsUtilities.cs
@@ -1491,14 +1491,10 @@ namespace Org.BouncyCastle.Tls
                     :   securityParameters.BaseKeyClient;
 
                 TlsSecret finishedKey = DeriveSecret(securityParameters, baseKey, "finished", EmptyBytes);
+                int cryptoHashAlgorithm = TlsCryptoUtilities.GetHash(securityParameters.PrfHashAlgorithm);
                 byte[] transcriptHash = GetCurrentPrfHash(handshakeHash);
 
-                TlsCrypto crypto = context.Crypto;
-                byte[] hmacKey = crypto.AdoptSecret(finishedKey).Extract();
-                TlsHmac hmac = crypto.CreateHmacForHash(TlsCryptoUtilities.GetHash(securityParameters.PrfHashAlgorithm));
-                hmac.SetKey(hmacKey, 0, hmacKey.Length);
-                hmac.Update(transcriptHash, 0, transcriptHash.Length);
-                return hmac.CalculateMac();
+                return finishedKey.CalculateHmac(cryptoHashAlgorithm, transcriptHash, 0, transcriptHash.Length);
             }
 
             if (negotiatedVersion.IsSsl)
diff --git a/crypto/src/tls/crypto/TlsSecret.cs b/crypto/src/tls/crypto/TlsSecret.cs
index 0499d37c3..8c39c56f7 100644
--- a/crypto/src/tls/crypto/TlsSecret.cs
+++ b/crypto/src/tls/crypto/TlsSecret.cs
@@ -7,6 +7,14 @@ namespace Org.BouncyCastle.Tls.Crypto
     /// </summary>
     public interface TlsSecret
     {
+        /// <summary>Calculate an HMAC with this secret's data as the key.</summary>
+        /// <param name="cryptoHashAlgorithm">the hash algorithm to instantiate HMAC with. See
+        /// <see cref="CryptoHashAlgorithm"/> for values.</param>
+        /// <param name="buf">array containing the input data.</param>
+        /// <param name="off">offset into the input array the input starts at.</param>
+        /// <param name="len">the length of the input data.</param>
+        byte[] CalculateHmac(int cryptoHashAlgorithm, byte[] buf, int off, int len);
+
         /// <summary>Return a new secret based on applying a PRF to this one.</summary>
         /// <param name="prfAlgorithm">PRF algorithm to use.</param>
         /// <param name="label">the label details.</param>
diff --git a/crypto/src/tls/crypto/impl/AbstractTlsSecret.cs b/crypto/src/tls/crypto/impl/AbstractTlsSecret.cs
index e8298193f..1ea25344d 100644
--- a/crypto/src/tls/crypto/impl/AbstractTlsSecret.cs
+++ b/crypto/src/tls/crypto/impl/AbstractTlsSecret.cs
@@ -26,6 +26,19 @@ namespace Org.BouncyCastle.Tls.Crypto.Impl
 
         protected abstract AbstractTlsCrypto Crypto { get; }
 
+        public virtual byte[] CalculateHmac(int cryptoHashAlgorithm, byte[] buf, int off, int len)
+        {
+            lock (this)
+            {
+                CheckAlive();
+
+                TlsHmac hmac = Crypto.CreateHmacForHash(cryptoHashAlgorithm);
+                hmac.SetKey(m_data, 0, m_data.Length);
+                hmac.Update(buf, off, len);
+                return hmac.CalculateMac();
+            }
+        }
+
         public abstract TlsSecret DeriveUsingPrf(int prfAlgorithm, string label, byte[] seed, int length);
 
         public virtual void Destroy()