patternpassword: update large grid password scheme

CM13 and up no longer use the two method scheme.

Change-Id: I21154becb5d7e77a54a5a07e649fe64829173a01

gui/patternpassword.cpp

@@ -15,7 +15,7 @@ extern "C" {
 #include "../twcommon.h"
 }
 #include "../minuitwrp/minui.h"
-
+#include "../twrp-functions.hpp"
 #include "rapidxml.hpp"
 #include "objects.hpp"
 
@@ -403,6 +403,17 @@ int GUIPatternPassword::NotifyVarChange(const std::string& varName, const std::s
 	return 0;
 }
 
+static unsigned int getSDKVersion(void) {
+	unsigned int sdkver = 23;
+	string sdkverstr = TWFunc::System_Property_Get("ro.build.version.sdk");
+	if (!sdkverstr.empty()) {
+		sdkver = (unsigned int)strtoull(sdkverstr.c_str(), NULL, 10);
+		sdkver = (sdkver != 0) ? sdkver : 23;
+	}
+	LOGINFO("sdk version is %u\n", sdkver);
+	return sdkver;
+}
+
 std::string GUIPatternPassword::GeneratePassphrase()
 {
 	char pattern[mConnectedDotsLen];
@@ -411,12 +422,17 @@ std::string GUIPatternPassword::GeneratePassphrase()
 	}
 
 	std::stringstream pass;
+	char buffer[3] = {0};
 
-	for(size_t i = 0; i < mConnectedDotsLen; i++) {
-		int digit = pattern[i] & 0xff;
-
+	if ((mGridSize == 3) || (getSDKVersion() >= 23)) {
+		// Marshmallow uses a consistent method
+		for (size_t i = 0; i < mConnectedDotsLen; i++) {
+			buffer[0] = (pattern[i] & 0xff) + '1';
+			pass << std::string(buffer);
+		}
+	} else {
 		/*
-		 * Okay, rant time.
+		 * Okay, rant time for pre-Marshmallow ROMs.
 		 * It turns out that Android and CyanogenMod have *two* separate methods
 		 * for generating passphrases from patterns. This is a legacy issue, as
 		 * Android only supports 3x3 grids, and so we need to support both.
@@ -431,14 +447,8 @@ std::string GUIPatternPassword::GeneratePassphrase()
 		 * they are generated by taking "%.2x" for each dot index and
 		 * concatenating the results (without adding 1).
 		 */
-
-		if(mGridSize == 3)
-			// Android (legacy) 3x3 grids.
-			pass << digit + 1;
-		else {
-			// Other NxN grids.
-			char buffer[3];
-			snprintf(buffer, 3, "%.2x", digit);
+		for (size_t i = 0; i < mConnectedDotsLen; i++) {
+			snprintf(buffer, 3, "%.2x", pattern[i] & 0xff);
 			pass << std::string(buffer);
 		}
 	}