8174756: Extra validation for public keys

Reviewed-by: valeriep

src/share/classes/sun/security/rsa/RSAPublicKeyImpl.java

@@ -48,6 +48,7 @@ import sun.security.x509.X509Key;
 public final class RSAPublicKeyImpl extends X509Key implements RSAPublicKey {
 
     private static final long serialVersionUID = 2644735423591199609L;
+    private static final BigInteger THREE = BigInteger.valueOf(3);
 
     private BigInteger n;       // modulus
     private BigInteger e;       // public exponent
@@ -61,6 +62,7 @@ public final class RSAPublicKeyImpl extends X509Key implements RSAPublicKey {
         this.n = n;
         this.e = e;
         RSAKeyFactory.checkRSAProviderKeyLengths(n.bitLength(), e);
+        checkExponentRange();
         // generate the encoding
         algid = RSAPrivateCrtKeyImpl.rsaId;
         try {
@@ -83,6 +85,19 @@ public final class RSAPublicKeyImpl extends X509Key implements RSAPublicKey {
     public RSAPublicKeyImpl(byte[] encoded) throws InvalidKeyException {
         decode(encoded);
         RSAKeyFactory.checkRSAProviderKeyLengths(n.bitLength(), e);
+        checkExponentRange();
+    }
+
+    private void checkExponentRange() throws InvalidKeyException {
+        // the exponent should be smaller than the modulus
+        if (e.compareTo(n) >= 0) {
+            throw new InvalidKeyException("exponent is larger than modulus");
+        }
+
+        // the exponent should be at least 3
+        if (e.compareTo(THREE) < 0) {
+            throw new InvalidKeyException("exponent is smaller than 3");
+        }
     }
 
     // see JCA doc