api: unify and document resource loading

Signed-off-by: Simon Rozman <simon@rozman.si>

api/driver.c

@@ -135,22 +135,12 @@ static WINTUN_STATUS
 InstallCertificate(_In_z_ const WCHAR *SignedResource)
 {
     WINTUN_LOGGER(WINTUN_LOG_INFO, L"Trusting code signing certificate");
-    HRSRC FoundResource = FindResourceW(ResourceModule, SignedResource, RT_RCDATA);
+    const VOID *LockedResource;
-    if (!FoundResource)
+    DWORD SizeResource;
-        return WINTUN_LOGGER_LAST_ERROR(L"Failed to find resource");
+    DWORD Result = ResourceGetAddress(SignedResource, &LockedResource, &SizeResource);
-    DWORD SizeResource = SizeofResource(ResourceModule, FoundResource);
+    if (Result != ERROR_SUCCESS)
-    if (!SizeResource)
+        return WINTUN_LOGGER_ERROR("Failed to locate resource", Result);
-        return WINTUN_LOGGER_LAST_ERROR(L"Failed to size resource");
+    const CERT_BLOB CertBlob = { .cbData = SizeResource, .pbData = (BYTE *)LockedResource };
-    HGLOBAL LoadedResource = LoadResource(ResourceModule, FoundResource);
-    if (!LoadedResource)
-        return WINTUN_LOGGER_LAST_ERROR(L"Failed to load resource");
-    LPVOID LockedResource = LockResource(LoadedResource);
-    if (!LockedResource)
-    {
-        WINTUN_LOGGER(WINTUN_LOG_ERR, L"Failed to lock resource");
-        return ERROR_LOCK_FAILED;
-    }
-    const CERT_BLOB CertBlob = { .cbData = SizeResource, .pbData = LockedResource };
     HCERTSTORE QueriedStore;
     if (!CryptQueryObject(
             CERT_QUERY_OBJECT_BLOB,
@@ -165,7 +155,6 @@ InstallCertificate(_In_z_ const WCHAR *SignedResource)
             0,
             NULL))
         return WINTUN_LOGGER_LAST_ERROR("Failed to find certificate");
-    DWORD Result = ERROR_SUCCESS;
     HCERTSTORE TrustedStore =
         CertOpenStore(CERT_STORE_PROV_SYSTEM, 0, 0, CERT_SYSTEM_STORE_LOCAL_MACHINE, L"TrustedPublisher");
     if (!TrustedStore)
@@ -285,11 +274,11 @@ InstallDriver(_In_ BOOL UpdateExisting)
         WINTUN_LOGGER_ERROR(L"Unable to install code signing certificate", Result);
 
     WINTUN_LOGGER(WINTUN_LOG_INFO, L"Copying resources to temporary path");
-    if ((Result = CopyResource(CatPath, &SecurityAttributes, UseWHQL ? L"wintun-whql.cat" : L"wintun.cat")) !=
+    if ((Result = ResourceCopyToFile(CatPath, &SecurityAttributes, UseWHQL ? L"wintun-whql.cat" : L"wintun.cat")) !=
             ERROR_SUCCESS ||
-        (Result = CopyResource(SysPath, &SecurityAttributes, UseWHQL ? L"wintun-whql.sys" : L"wintun.sys")) !=
+        (Result = ResourceCopyToFile(SysPath, &SecurityAttributes, UseWHQL ? L"wintun-whql.sys" : L"wintun.sys")) !=
             ERROR_SUCCESS ||
-        (Result = CopyResource(InfPath, &SecurityAttributes, UseWHQL ? L"wintun-whql.inf" : L"wintun.inf")) !=
+        (Result = ResourceCopyToFile(InfPath, &SecurityAttributes, UseWHQL ? L"wintun-whql.inf" : L"wintun.inf")) !=
             ERROR_SUCCESS)
     {
         Result = WINTUN_LOGGER_LAST_ERROR(L"Failed to copy resources");

api/resource.c

@@ -5,27 +5,60 @@
 
 #include "pch.h"
 
+/**
+ * Locates RT_RCDATA resource memory address and size.
+ *
+ * ResourceName         Name of the RT_RCDATA resource. Use MAKEINTRESOURCEW to locate resource by ID.
+ *
+ * Address              Pointer to a pointer variable to receive resource address.
+ *
+ * Size                 Pointer to a variable to receive resource size.
+ *
+ * @return ERROR_SUCCESS on success; Win32 error code otherwise.
+ */
 WINTUN_STATUS
-CopyResource(
+ResourceGetAddress(_In_z_ const WCHAR *ResourceName, _Out_ const VOID **Address, _Out_ DWORD *Size)
-    _In_z_ const WCHAR *DestinationPath,
-    _In_opt_ SECURITY_ATTRIBUTES *SecurityAttributes,
-    _In_z_ const WCHAR *ResourceName)
 {
     HRSRC FoundResource = FindResourceW(ResourceModule, ResourceName, RT_RCDATA);
     if (!FoundResource)
         return WINTUN_LOGGER_LAST_ERROR(L"Failed to find resource");
-    DWORD SizeResource = SizeofResource(ResourceModule, FoundResource);
+    *Size = SizeofResource(ResourceModule, FoundResource);
-    if (!SizeResource)
+    if (!*Size)
         return WINTUN_LOGGER_LAST_ERROR(L"Failed to size resource");
     HGLOBAL LoadedResource = LoadResource(ResourceModule, FoundResource);
     if (!LoadedResource)
         return WINTUN_LOGGER_LAST_ERROR(L"Failed to load resource");
-    LPVOID LockedResource = LockResource(LoadedResource);
+    *Address = LockResource(LoadedResource);
-    if (!LockedResource)
+    if (!*Address)
     {
         WINTUN_LOGGER(WINTUN_LOG_ERR, L"Failed to lock resource");
         return ERROR_LOCK_FAILED;
     }
+    return ERROR_SUCCESS;
+}
+
+/**
+ * Copies resource to a file.
+ *
+ * DestinationPath      File path
+ *
+ * SecurityAttributes   File security attributes. May be NULL for detault.
+ *
+ * ResourceName         Name of the RT_RCDATA resource. Use MAKEINTRESOURCEW to locate resource by ID.
+ *
+ * @return ERROR_SUCCESS on success; Win32 error code otherwise.
+ */
+WINTUN_STATUS
+ResourceCopyToFile(
+    _In_z_ const WCHAR *DestinationPath,
+    _In_opt_ SECURITY_ATTRIBUTES *SecurityAttributes,
+    _In_z_ const WCHAR *ResourceName)
+{
+    const VOID *LockedResource;
+    DWORD SizeResource;
+    DWORD Result = ResourceGetAddress(ResourceName, &LockedResource, &SizeResource);
+    if (Result != ERROR_SUCCESS)
+        return WINTUN_LOGGER_ERROR("Failed to locate resource", Result);
     HANDLE DestinationHandle = CreateFileW(
         DestinationPath,
         GENERIC_WRITE,
@@ -37,7 +70,6 @@ CopyResource(
     if (DestinationHandle == INVALID_HANDLE_VALUE)
         return WINTUN_LOGGER_LAST_ERROR(L"Failed to create file");
     DWORD BytesWritten;
-    DWORD Result = ERROR_SUCCESS;
     if (!WriteFile(DestinationHandle, LockedResource, SizeResource, &BytesWritten, NULL))
         Result = WINTUN_LOGGER_LAST_ERROR(L"Failed to write file");
     if (BytesWritten != SizeResource)

api/resource.h

@@ -9,7 +9,10 @@
 #include <Windows.h>
 
 WINTUN_STATUS
-CopyResource(
+ResourceGetAddress(_In_z_ const WCHAR *ResourceName, _Out_ const VOID **Address, _Out_ DWORD *Size);
+
+WINTUN_STATUS
+ResourceCopyToFile(
     _In_z_ const WCHAR *DestinationPath,
     _In_opt_ SECURITY_ATTRIBUTES *SecurityAttributes,
     _In_z_ const WCHAR *ResourceName);