1 files changed, 69 insertions, 0 deletions
diff --git a/crypto/src/tls/SimulatedTlsSrpIdentityManager.cs b/crypto/src/tls/SimulatedTlsSrpIdentityManager.cs
new file mode 100644
index 000000000..904bdae6d
--- /dev/null
+++ b/crypto/src/tls/SimulatedTlsSrpIdentityManager.cs
@@ -0,0 +1,69 @@
+using System;
+using System.IO;
+
+using Org.BouncyCastle.Math;
+using Org.BouncyCastle.Tls.Crypto;
+using Org.BouncyCastle.Utilities;
+
+namespace Org.BouncyCastle.Tls
+{
+    /// <summary>An implementation of <see cref="TlsSrpIdentityManager"/> that simulates the existence of "unknown"
+    /// identities to obscure the fact that there is no verifier for them.</summary>
+    public class SimulatedTlsSrpIdentityManager
+        : TlsSrpIdentityManager
+    {
+        private static readonly byte[] PrefixPassword = Strings.ToByteArray("password");
+        private static readonly byte[] PrefixSalt = Strings.ToByteArray("salt");
+
+        /// <summary>Create a <see cref="SimulatedTlsSrpIdentityManager"/> that implements the algorithm from RFC 5054
+        /// 2.5.1.3.</summary>
+        /// <param name="crypto"><see cref="TlsCrypto"/></param>
+        /// <param name="group">the <see cref="Srp6Group"/> defining the group that SRP is operating in.</param>
+        /// <param name="seedKey">the secret "seed key" referred to in RFC 5054 2.5.1.3.</param>
+        /// <returns>an instance of <see cref="SimulatedTlsSrpIdentityManager"/>.</returns>
+        /// <exception cref="IOException"/>
+        public static SimulatedTlsSrpIdentityManager GetRfc5054Default(TlsCrypto crypto, Srp6Group group, byte[] seedKey)
+        {
+            TlsMac mac = crypto.CreateHmac(MacAlgorithm.hmac_sha1);
+
+            mac.SetKey(seedKey, 0, seedKey.Length);
+
+            TlsSrpConfig srpConfig = new TlsSrpConfig();
+
+            srpConfig.SetExplicitNG(new BigInteger[]{ group.N, group.G });
+
+            return new SimulatedTlsSrpIdentityManager(group, crypto.CreateSrp6VerifierGenerator(srpConfig), mac);
+        }
+
+        protected readonly Srp6Group m_group;
+        protected readonly TlsSrp6VerifierGenerator m_verifierGenerator;
+        protected readonly TlsMac m_mac;
+
+        public SimulatedTlsSrpIdentityManager(Srp6Group group, TlsSrp6VerifierGenerator verifierGenerator, TlsMac mac)
+        {
+            this.m_group = group;
+            this.m_verifierGenerator = verifierGenerator;
+            this.m_mac = mac;
+        }
+
+        public virtual TlsSrpLoginParameters GetLoginParameters(byte[] identity)
+        {
+            m_mac.Update(PrefixSalt, 0, PrefixSalt.Length);
+            m_mac.Update(identity, 0, identity.Length);
+
+            byte[] salt = m_mac.CalculateMac();
+
+            m_mac.Update(PrefixPassword, 0, PrefixPassword.Length);
+            m_mac.Update(identity, 0, identity.Length);
+
+            byte[] password = m_mac.CalculateMac();
+
+            BigInteger verifier = m_verifierGenerator.GenerateVerifier(salt, identity, password);
+
+            TlsSrpConfig srpConfig = new TlsSrpConfig();
+            srpConfig.SetExplicitNG(new BigInteger[]{ m_group.N, m_group.G });
+
+            return new TlsSrpLoginParameters(identity, srpConfig, verifier, salt);
+        }
+    }
+}