Windows: Implement support for mounting partially encrypted system partitions

For now, we force ReadOnly mounting for such partitions.

src/Common/Apidrvr.h

@@ -166,6 +166,7 @@ typedef struct
 	BOOL RecoveryMode;
 	int pkcs5_prf;
 	int ProtectedHidVolPkcs5Prf;
+	BOOL VolumeMountedReadOnlyAfterPartialSysEnc;
 	uint32 BytesPerPhysicalSector;
 	int VolumePim;
 	int ProtectedHidVolPim;

src/Common/Dlgcode.c

@@ -9253,6 +9253,17 @@ retry:
 		}
 	}
 
+	if (mount.VolumeMountedReadOnlyAfterPartialSysEnc
+		&& !Silent
+		&& bDevice)
+	{
+		wchar_t msg[1024];
+		wchar_t mountPoint[] = { L'A' + (wchar_t) driveNo, L':', 0 };
+		StringCbPrintfW (msg, sizeof(msg), GetString ("PARTIAL_SYSENC_MOUNT_READONLY"), mountPoint);
+
+		WarningDirect (msg, hwndDlg);
+	}
+
 	if (mount.wszLabel[0] && !mount.bDriverSetLabel)
 	{
 		// try setting the drive label on user-mode using registry

src/Common/Language.xml

@@ -1631,6 +1631,7 @@
     <entry lang="en" key="EXPANDER_MOUNTING_VOLUME">Mounting volume ...\n</entry>
     <entry lang="en" key="EXPANDER_UNMOUNTING_VOLUME">Unmounting volume ...\n</entry>
     <entry lang="en" key="EXPANDER_EXTENDING_FILESYSTEM">Extending file system ...\n</entry>
+    <entry lang="en" key="PARTIAL_SYSENC_MOUNT_READONLY">Warning: The system partition you attempted to mount was not fully encrypted. As a safety measure to prevent potential corruption or unwanted modifications, volume '%s' was mounted as read-only.</entry>
   </localization>
   <xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema">
     <xs:element name="VeraCrypt">