add cig_sha256

Signed-off-by: John Crispin <john@phrozen.org>

renderer/signature.uc

@@ -1,7 +1,33 @@
+let fs = require('fs');
+
 let key_info = {
 	'dummy_static': function(file, signature) {
 		return signature == 'aaaaaaaaaa';
 	},
+	'cig_sha256': function(file, signature) {
+		// Decrypt from base64 to binary and write to a tmp file
+		let decoded = b64dec(signature);
+		if (!decoded) {
+			return false;
+		}
+		let pub_key_file_name = "/etc/ucentral/sign_pubkey.pem";
+		let sign_file_name = "/tmp/sign_file.txt";
+		let sign_file = fs.open(sign_file_name, "w");
+		sign_file.write(decoded);
+		sign_file.close();
+
+		// Verify the signature
+		let sign_verify_cmd = "openssl dgst -sha256 -verify " + pub_key_file_name + " -signature " + sign_file_name + " " + file;
+		let pipe = fs.popen(sign_verify_cmd);
+		let result = pipe.read("all");
+		let retcode = pipe.close();
+		// Return code of 0 is valid signature
+		if (retcode == 0) {
+			return true;
+		} else {
+			return false;
+		}
+	},
 };
 
 return {