Clean up |ECDH_compute_key|.

1. Check for the presence of the private key before allocating or
   computing anything.
2. Check the return value of |BN_CTX_get|.
3. Don't bother computing the Y coordinate since it is not used.
4. Remove conditional logic in cleanup section.

Change-Id: I4d8611603363c7e5d16a8e9f1d6c3a56809f27ae
Reviewed-on: https://boringssl-review.googlesource.com/6171
Reviewed-by: Adam Langley <alangley@gmail.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/include/openssl/ecdh.h b/include/openssl/ecdh.h
index 878cbeb5..5fe3ae99 100644
--- a/include/openssl/ecdh.h
+++ b/include/openssl/ecdh.h
@@ -80,14 +80,14 @@ extern "C" {
 
 
 /* ECDH_compute_key calculates the shared key between |pub_key| and |priv_key|.
- * If |KDF| is not NULL, then it is called with the bytes of the shared key and
- * the parameter |out|. When |KDF| returns, the value of |*outlen| becomes the
+ * If |kdf| is not NULL, then it is called with the bytes of the shared key and
+ * the parameter |out|. When |kdf| returns, the value of |*outlen| becomes the
  * return value. Otherwise, as many bytes of the shared key as will fit are
  * copied directly to, at most, |outlen| bytes at |out|. It returns the number
  * of bytes written to |out|, or -1 on error. */
 OPENSSL_EXPORT int ECDH_compute_key(void *out, size_t outlen,
                                     const EC_POINT *pub_key, EC_KEY *priv_key,
-                                    void *(*KDF)(const void *in, size_t inlen,
+                                    void *(*kdf)(const void *in, size_t inlen,
                                                  void *out, size_t *outlen));