crypto: dh secret should be left-padded

DH_compute_secret() may return key that is smaller than input buffer,
in such cases key should be left-padded because it is a BN (big number).

fix #5239

1 files changed, 2 insertions, 1 deletions

diff --git a/src/node_crypto.cc b/src/node_crypto.cc
index eb7e5546c..1b9c7b6b5 100644
--- a/src/node_crypto.cc
+++ b/src/node_crypto.cc
@@ -3586,7 +3586,8 @@ class DiffieHellman : public ObjectWrap {
     // allocated buffer.
     if (size != dataSize) {
       assert(dataSize > size);
-      memset(data + size, 0, dataSize - size);
+      memmove(data + dataSize - size, data, size);
+      memset(data, 0, dataSize - size);
     }
 
     Local<Value> outString;