Fix crypto.hmac behavior with empty keys.

node 0.9.6 introduced Buffer changes that cause the key argument of
Hmac::HmacInit (used in crypto.createHmac) to be NULL when the key is
empty. This argument is passed to OpenSSL's HMAC_Init, which does not
like NULL keys.

This change works around the issue by passing an empty string to
HMAC_Init when the key is empty, and adds crypto.createHmac tests for
the edge cases of empty keys and values.

1 files changed, 5 insertions, 1 deletions

diff --git a/src/node_crypto.cc b/src/node_crypto.cc
index e861bb34f..7fe81876f 100644
--- a/src/node_crypto.cc
+++ b/src/node_crypto.cc
@@ -2641,7 +2641,11 @@ class Hmac : public ObjectWrap {
       return false;
     }
     HMAC_CTX_init(&ctx);
-    HMAC_Init(&ctx, key, key_len, md);
+    if (key_len == 0) {
+      HMAC_Init(&ctx, "", 0, md);
+    } else {
+      HMAC_Init(&ctx, key, key_len, md);
+    }
     initialised_ = true;
     return true;