CryptoPkg: Add EC key retrieving and signature interface.

This patch is used to retrieve EC key from PEM and X509 and
carry out the EC-DSA signature and verify it.

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4102

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Xiaoyu Lu <xiaoyu1.lu@intel.com>
Cc: Guomin Jiang <guomin.jiang@intel.com>
Signed-off-by: Qi Zhang <qi1.zhang@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>

CryptoPkg/Library/BaseCryptLibNull/Pem/CryptPemNull.c

@@ -36,3 +36,33 @@ RsaGetPrivateKeyFromPem (
   ASSERT (FALSE);
   return FALSE;
 }
+
+/**
+  Retrieve the EC Private Key from the password-protected PEM key data.
+
+  @param[in]  PemData      Pointer to the PEM-encoded key data to be retrieved.
+  @param[in]  PemSize      Size of the PEM key data in bytes.
+  @param[in]  Password     NULL-terminated passphrase used for encrypted PEM key data.
+  @param[out] EcContext    Pointer to new-generated EC DSA context which contain the retrieved
+                           EC private key component. Use EcFree() function to free the
+                           resource.
+
+  If PemData is NULL, then return FALSE.
+  If EcContext is NULL, then return FALSE.
+
+  @retval  TRUE   EC Private Key was retrieved successfully.
+  @retval  FALSE  Invalid PEM key data or incorrect password.
+
+**/
+BOOLEAN
+EFIAPI
+EcGetPrivateKeyFromPem (
+  IN   CONST UINT8  *PemData,
+  IN   UINTN        PemSize,
+  IN   CONST CHAR8  *Password,
+  OUT  VOID         **EcContext
+  )
+{
+  ASSERT (FALSE);
+  return FALSE;
+}