crypto: fix crash when calling digest after piping

When piping data into an SHA3 hash, EVP_DigestFinal_ex is called in hash._flush, bypassing safeguards in the JavaScript layer. Calling hash.digest causes EVP_DigestFinal_ex to be called again, resulting in a segmentation fault in the SHA3 implementation of OpenSSL. A relatively easy solution is to cache the result of calling EVP_DigestFinal_ex until the Hash object is garbage collected. PR-URL: nodejs#28251 Fixes: nodejs#28245 Reviewed-By: James M Snell <[email protected]> Reviewed-By: Ben Noordhuis <[email protected]>
evanlucas · Feb 4, 2021 · 2a0571a · 2a0571a
1 parent bc0617f
commit 2a0571a
Show file tree

Hide file tree

Showing 2 changed files with 18 additions and 7 deletions.
diff --git a/src/node_crypto.cc b/src/node_crypto.cc
@@ -3419,16 +3419,20 @@ void Hash::HashDigest(const FunctionCallbackInfo<Value>& args) {
     encoding = ParseEncoding(env->isolate(), args[0], BUFFER);
   }
 
-  unsigned char md_value[EVP_MAX_MD_SIZE];
-  unsigned int md_len;
-
-  EVP_DigestFinal_ex(hash->mdctx_.get(), md_value, &md_len);
+  if (hash->md_len_ == 0) {
+    // Some hash algorithms such as SHA3 do not support calling
+    // EVP_DigestFinal_ex more than once, however, Hash._flush
+    // and Hash.digest can both be used to retrieve the digest,
+    // so we need to cache it.
+    // See https://github.com/nodejs/node/issues/28245.
+    EVP_DigestFinal_ex(hash->mdctx_.get(), hash->md_value_, &hash->md_len_);
+  }
 
   Local<Value> error;
   MaybeLocal<Value> rc =
       StringBytes::Encode(env->isolate(),
-                          reinterpret_cast<const char*>(md_value),
-                          md_len,
+                          reinterpret_cast<const char*>(hash->md_value_),
+                          hash->md_len_,
                           encoding,
                           &error);
   if (rc.IsEmpty()) {

diff --git a/src/node_crypto.h b/src/node_crypto.h
@@ -475,12 +475,19 @@ class Hash : public BaseObject {
 
   Hash(Environment* env, v8::Local<v8::Object> wrap)
       : BaseObject(env, wrap),
-        mdctx_(nullptr) {
+        mdctx_(nullptr),
+        md_len_(0) {
     MakeWeak();
   }
 
+  ~Hash() override {
+    OPENSSL_cleanse(md_value_, md_len_);
+  }
+
  private:
   EVPMDPointer mdctx_;
+  unsigned char md_value_[EVP_MAX_MD_SIZE];
+  unsigned int md_len_;
 };
 
 class SignBase : public BaseObject {