Revert "swupdate_class: Add support for engine signing"

This reverts commit 3ba81db8065a42b22a93f83d7436296ef36166c2.

README

@@ -31,33 +31,6 @@ sw-description.sig which is included in the SWU file.
 Encrypted private keys are not currently supported since a secure 
 mechanism must exist to provide the passphrase.
 
-SWU image hardware signing
---------------------------
-
-One may prefer to sign the SWU image with a hardware token or hardware security
-module (HSM) which doesn't expose the private key.
-
-To enable, SWUPDATE_SIGNING_ENGINE must be set to an available openssl engine.
-
-Example:
-    SWUPDATE_SIGNING_ENGINE = "pkcs11"
-
-SWUPDATE_SIGNING_ENGINE_PATH may need to be set so that openssl can locate the
-engine.
-
-Example:
-    SWUPDATE_SIGNING_ENGINE_PATH = "/usr/lib"
-
-Instead of setting SWUPDATE_PRIVATE_KEY to the full path of a file, set it to
-a key string recognized by the engine used.
-
-Example:
-    SWUPDATE_PRIVATE_KEY = "pkcs11:model=SoftHSM%20v2;" \
-                           "manufacturer=SoftHSM%20project;" \
-                           "serial=1234567890;" \
-                           "token=test-token;pin-value=123456;" \
-                           "object=swupdate-test"
-
 Maintainer
 ----------
 

classes/swupdate.bbclass

@@ -144,34 +144,16 @@ python do_swuimage () {
         privkey = d.getVar('SWUPDATE_PRIVATE_KEY', True)
         if not privkey:
             bb.fatal("SWUPDATE_PRIVATE_KEY isn't set")
-
-        engine = d.getVar('SWUPDATE_SIGNING_ENGINE', True)
-        if engine:
-            engine = "-engine '%s' -keyform engine " % (engine)
-        elif not os.path.exists(privkey):
+        if not os.path.exists(privkey):
             bb.fatal("SWUPDATE_PRIVATE_KEY %s doesn't exist" % (privkey))
-        else:
-            engine = ""
-
-        engine_path = d.getVar('SWUPDATE_SIGNING_ENGINE_PATH', True)
-        if engine and engine_path:
-            engine_path = 'OPENSSL_ENGINES="%s" ' % (engine_path)
-        else:
-            engine_path = ""
-
         passout = d.getVar('SWUPDATE_PASSWORD_FILE', True)
         if passout:
             passout = "-passin file:'%s' " % (passout)
         else:
             passout = ""
-
-        # Sign with openssl.real, provided by openssl-native so OPENSSL_ENGINES
-        # can be overridden
-        signcmd = "%sopenssl.real dgst -sha256 -sign '%s' %s%s -out '%s' '%s'" % (
-            engine_path,
+        signcmd = "openssl dgst -sha256 -sign '%s' %s -out '%s' '%s'" % (
             privkey,
             passout,
-            engine,
             os.path.join(s, 'sw-description.sig'),
             os.path.join(s, 'sw-description'))
         if os.system(signcmd) != 0: