crypto: better error message for createHash

calling digest or update on a hash object after digest has been called
now gives a topical error message instead of an error message saying that the
hash failed to initialize.

src/node_crypto.cc

@@ -3676,6 +3676,7 @@ bool Hash::HashInit(const char* hash_type) {
     return false;
   }
   initialised_ = true;
+  finalized_ = false;
   return true;
 }
 
@@ -3695,6 +3696,13 @@ void Hash::HashUpdate(const FunctionCallbackInfo<Value>& args) {
 
   THROW_AND_RETURN_IF_NOT_STRING_OR_BUFFER(args[0], "Data");
 
+  if (!hash->initialised_) {
+    return env->ThrowError("Not initialized");
+  }
+  if (hash->finalized_) {
+    return env->ThrowError("Digest already called");
+  }
+
   // Only copy the data if we have to, because it's a string
   bool r;
   if (args[0]->IsString()) {
@@ -3722,6 +3730,9 @@ void Hash::HashDigest(const FunctionCallbackInfo<Value>& args) {
   if (!hash->initialised_) {
     return env->ThrowError("Not initialized");
   }
+  if (hash->finalized_) {
+    return env->ThrowError("Digest already called");
+  }
 
   enum encoding encoding = BUFFER;
   if (args.Length() >= 1) {
@@ -3735,7 +3746,7 @@ void Hash::HashDigest(const FunctionCallbackInfo<Value>& args) {
 
   EVP_DigestFinal_ex(&hash->mdctx_, md_value, &md_len);
   EVP_MD_CTX_cleanup(&hash->mdctx_);
-  hash->initialised_ = false;
+  hash->finalized_ = true;
 
   Local<Value> rc = StringBytes::Encode(env->isolate(),
                                         reinterpret_cast<const char*>(md_value),

src/node_crypto.h

@@ -538,6 +538,7 @@ class Hash : public BaseObject {
   EVP_MD_CTX mdctx_; /* coverity[member_decl] */
   const EVP_MD* md_; /* coverity[member_decl] */
   bool initialised_;
+  bool finalized_;
 };
 
 class SignBase : public BaseObject {

test/parallel/test-crypto-hash.js

@@ -98,3 +98,15 @@ assert.equal(
 assert.notEqual(
     hutf8,
     crypto.createHash('sha512').update('УТФ-8 text', 'binary').digest('hex'));
+
+var h3 = crypto.createHash('sha256');
+h3.digest();
+assert.throws(function() {
+  h3.digest();
+},
+  /Digest already called/);
+
+assert.throws(function() {
+  h3.update('foo');
+},
+  /Digest already called/);