Verify the VBS enclave key binding on the async attestation path

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/VirtualSecureModeEnclaveProviderBase.cs

@@ -124,11 +124,8 @@ internal override void CreateEnclaveSession(byte[] attestationInfo, ECDiffieHell
                         // Perform Attestation per VSM protocol
                         VerifyAttestationInfo(enclaveSessionParameters.AttestationUrl, info.HealthReport, info.EnclaveReportPackage);
 
-                        // Verify the enclave public key is bound to the signed report, before it is used for key exchange
-                        VerifyEnclavePublicKeyBinding(info.EnclaveReportPackage, info.Identity);
-
                         // Set up shared secret and validate signature
-                        byte[] sharedSecret = GetSharedSecret(info.Identity, info.EnclaveDHInfo, clientDHKey);
+                        byte[] sharedSecret = GetSharedSecret(info.EnclaveReportPackage, info.Identity, info.EnclaveDHInfo, clientDHKey);
 
                         // add session to cache
                         sqlEnclaveSession = AddEnclaveSessionToCache(enclaveSessionParameters, sharedSecret, info.SessionId, out counter);
@@ -186,7 +183,7 @@ await VerifyAttestationInfoAsync(
                 cancellationToken).ConfigureAwait(false);
 
             // Set up shared secret and validate signature
-            byte[] sharedSecret = GetSharedSecret(info.Identity, info.EnclaveDHInfo, clientDHKey);
+            byte[] sharedSecret = GetSharedSecret(info.EnclaveReportPackage, info.Identity, info.EnclaveDHInfo, clientDHKey);
 
             // add session to cache
             SqlEnclaveSession sqlEnclaveSession =
@@ -608,9 +605,15 @@ private void VerifyEnclavePolicyProperty(string property, uint actual, uint expe
             }
         }
 
-        // Derives the shared secret between the client and enclave.
-        private byte[] GetSharedSecret(EnclavePublicKey enclavePublicKey, EnclaveDiffieHellmanInfo enclaveDHInfo, ECDiffieHellman clientDHKey)
+        // Derives the session's shared secret from the enclave's public key, after verifying that the
+        // signed report commits to that key. The binding check lives here, rather than in each caller,
+        // so that no attestation path can derive a secret from an unbound key.
+        // This is internal to allow for targeted unit testing.
+        internal static byte[] GetSharedSecret(EnclaveReportPackage enclaveReportPackage, EnclavePublicKey enclavePublicKey, EnclaveDiffieHellmanInfo enclaveDHInfo, ECDiffieHellman clientDHKey)
         {
+            // Verify the enclave public key is bound to the signed report, before it is used for key exchange
+            VerifyEnclavePublicKeyBinding(enclaveReportPackage, enclavePublicKey);
+
             // Perform signature verification. The enclave's DiffieHellman public key was signed by the enclave's RSA public key.
             using (RSA rsa = KeyConverter.CreateRSAFromPublicKeyBlob(enclavePublicKey.PublicKey))
             {

src/Microsoft.Data.SqlClient/tests/UnitTests/Microsoft/Data/SqlClient/VirtualSecureModeEnclaveProviderTest.cs

@@ -62,6 +62,32 @@ public void VerifyEnclavePublicKeyBinding_SwappedKey_Throws()
         Assert.Equal(Strings.VerifyEnclaveKeyBindingFailed, ex.Message);
     }
 
+    /// <summary>
+    /// Deriving the session secret rejects an enclave public key the signed report doesn't commit
+    /// to, before using the key. Both the sync and async attestation paths derive the secret through
+    /// this method, so neither can skip the binding check; the async path did skip it when the check
+    /// lived in each caller.
+    /// </summary>
+    [Fact]
+    public void GetSharedSecret_UnboundKey_Throws()
+    {
+        // Arrange
+        EnclaveReportPackage testPackage = BuildReportPackage(Sha256(Encoding.UTF8.GetBytes("committed-enclave-public-key-blob")));
+        EnclavePublicKey substitutedKey = new EnclavePublicKey(Encoding.UTF8.GetBytes("substituted-enclave-public-key"));
+
+        // Act
+        // The Diffie-Hellman inputs are null: the binding check must reject the key before they are used.
+        Action action = () => VirtualizationBasedSecurityEnclaveProviderBase.GetSharedSecret(
+            testPackage,
+            substitutedKey,
+            enclaveDHInfo: null,
+            clientDHKey: null);
+
+        // Assert
+        ArgumentException ex = Assert.Throws<ArgumentException>(action);
+        Assert.Equal(Strings.VerifyEnclaveKeyBindingFailed, ex.Message);
+    }
+
     // Builds a minimal EnclaveReportPackage whose report EnclaveData begins with the given 32-byte
     // binding value. The signature is empty because this targets the binding, not the report signature.
     private static EnclaveReportPackage BuildReportPackage(byte[] enclaveDataFirst32)