SM2 user ID length checks

Author: peterdettman

core/src/main/java/org/bouncycastle/crypto/agreement/SM2KeyExchange.java

@@ -53,6 +53,12 @@ public void init(
         {
             baseParam = (SM2KeyExchangePrivateParameters)((ParametersWithID)privParam).getParameters();
             userID = ((ParametersWithID)privParam).getID();
+
+            if (userID.length >= 8192)
+            {
+                // The length in bits must be expressible in two bytes
+                throw new IllegalArgumentException("SM2 user ID must be less than 2^16 bits long");
+            }
         }
         else
         {
@@ -276,6 +282,7 @@ private byte[] getZ(Digest digest, byte[] userID, ECPoint pubPoint)
     private void addUserID(Digest digest, byte[] userID)
     {
         int len = userID.length * 8;
+//        assert len >>> 16 == 0;
 
         digest.update((byte)(len >>> 8));
         digest.update((byte)len);

core/src/main/java/org/bouncycastle/crypto/signers/SM2Signer.java

@@ -81,7 +81,8 @@ public void init(boolean forSigning, CipherParameters param)
 
             if (userID.length >= 8192)
             {
-                throw new IllegalArgumentException("SM2 user ID must be less than 2^13 bits long");
+                // The length in bits must be expressible in two bytes
+                throw new IllegalArgumentException("SM2 user ID must be less than 2^16 bits long");
             }
         }
         else
@@ -323,6 +324,8 @@ private byte[] getZ(byte[] userID)
     private void addUserID(Digest digest, byte[] userID)
     {
         int len = userID.length * 8;
+//        assert len >>> 16 == 0;
+
         digest.update((byte)(len >>> 8));
         digest.update((byte)len);
         digest.update(userID, 0, userID.length);