ncfcrypt.c

/*
NCF Crypt
=========

NCF Crypt is a tiny tool to encrypt or decrypt ncf files so they can be
validated in CFToolbox or to play the game with Steam.

Why do we need this tool?
-------------------------
Some games on Steam are encrytped so they can be preloaded even before the game
has been released. After the release Steam decrypts all files but in some cases
flags in the NCF file aren't set properly. That means that even if you have the
decrypted files steam and other tools will recognize them as encrytped just
becaues the NCF file says so. This tool only changes the flags to and does not
decrypt associated files.

Usage
-----
Just drag a NCF file on the executable and it will be decrytpted or encrytped.

### Advanced

    ncfcrypt [/S | /E | /D] filenames

        filenames - one ore more files to be crypted

        /S - Swaps the encryption flag for each entry (default behavior)
        /E - Encrypts all entries
        /D - Decrypts all entires

It's recommned to backup ncf files if you use /E or /D because mixed
attributes cannot be restored after encryption or decrypting the whole file.
*/

#include <Windows.h>

// Custom entry for smaller executable size.
#pragma comment(linker, "/entry:Start")

// NCF file format:
// http://singularity.us.to/dev/steam/Development.Non-Cache-File-Format.ashx.htm
enum {
    FLAG_CONFIG     = 1 << 0,
    FLAG_LAUNCH     = 1 << 1,
    FLAG_UNKNOWN1   = 1 << 2,
    FLAG_LOCKED     = 1 << 3,
    FLAG_UNKNOWN2   = 1 << 4,
    FLAG_NOCACHE    = 1 << 5,
    FLAG_BACKUP     = 1 << 6,
    FLAG_PURGE      = 1 << 7,
    FLAG_ENCRYPTED  = 1 << 8,
    FLAG_READONLY   = 1 << 9,
    FLAG_HIDDEN     = 1 << 10,
    FLAG_EXECUTABLE = 1 << 11,
    FLAG_UNKNOWN3   = 1 << 12,
    FLAG_UNKNOWN4   = 1 << 13,
    FLAG_FILE       = 1 << 14
};

typedef struct _FILE_HEADER {
    DWORD dwHeaderVersion;
    DWORD dwCacheType;
    DWORD dwFormatVersion;
    DWORD dwApplicationID;
    DWORD dwApplicationVersion;
    DWORD dwIsMounted;
    DWORD dwDummy0;
    DWORD dwFileSize;
    DWORD dwClusterSize;
    DWORD dwClusterCount;
    DWORD dwChecksum;
} FILE_HEADER, *PFILE_HEADER;

typedef struct _MANIFEST_HEADER {
    DWORD dwHeaderVersion;
    DWORD dwApplicationID;
    DWORD dwApplicationVersion;
    DWORD dwNodeCount;
    DWORD dwFileCount;
    DWORD dwCompressionBlockSize;
    DWORD dwBinarySize;
    DWORD dwNameSize;
    DWORD dwHashTableKeyCount;
    DWORD dwNumOfMinimumFootprintFiles;
    DWORD dwNumOfUserConfigFiles;
    DWORD dwBitmask;
    DWORD dwFingerprint;
    DWORD dwChecksum;
} MANIFEST_HEADER, *PMANIFEST_HEADER;

typedef struct _MANIFEST_NODE {
    DWORD dwNameOffset;
    DWORD dwCountOrSize;
    DWORD dwFileId;
    DWORD dwAttributes;
    DWORD dwParentIndex;
    DWORD dwNextIndex;
    DWORD dwChildIndex;
} MANIFEST_NODE, *PMANIFEST_NODE;

static BOOL ValidateFileHeader(PFILE_HEADER pFileHeader)
{
    DWORD i, dwChecksum = 0;
    PBYTE data = (PBYTE)pFileHeader;

    // add every single byte to the checksum
    for (i = 0; i < sizeof(FILE_HEADER) - sizeof(DWORD); i++) {
        dwChecksum += data[i];
    }

    return pFileHeader->dwChecksum == dwChecksum;
}

enum {
    OPTION_SWAP,
    OPTION_ENCRYPT,
    OPTION_DECRYPT
};

static void Swap(PMANIFEST_NODE rgManifestNodes, UINT dwManifestNodes)
{
    DWORD i;

    for (i = 0; i < dwManifestNodes; i++) {
        // folders don't have any flags, do nothing
        if (!rgManifestNodes[i].dwAttributes)
            continue;

        if (rgManifestNodes[i].dwAttributes & FLAG_ENCRYPTED)
            rgManifestNodes[i].dwAttributes ^= FLAG_ENCRYPTED;
        else
            rgManifestNodes[i].dwAttributes |= FLAG_ENCRYPTED;
    }
}

static void Encrypt(PMANIFEST_NODE rgManifestNodes, UINT dwManifestNodes)
{
    DWORD i;

    for (i = 0; i < dwManifestNodes; i++) {
        // folders don't have any flags, do nothing
        if (!rgManifestNodes[i].dwAttributes)
            continue;

        if (!(rgManifestNodes[i].dwAttributes & FLAG_ENCRYPTED))
            rgManifestNodes[i].dwAttributes |= FLAG_ENCRYPTED;
    }
}

static void Decrypt(PMANIFEST_NODE rgManifestNodes, UINT dwManifestNodes)
{
    DWORD i;

    for (i = 0; i < dwManifestNodes; i++) {
        // folders don't have any flags, do nothing
        if (!rgManifestNodes[i].dwAttributes)
            continue;

        if (rgManifestNodes[i].dwAttributes & FLAG_ENCRYPTED)
            rgManifestNodes[i].dwAttributes ^= FLAG_ENCRYPTED;
    }
}

static void CryptFile(PCWSTR pszFileName, DWORD dwOption)
{
    HANDLE hFile, hFileMapping;
    PVOID pBaseAddress;
    PBYTE pData;
    PFILE_HEADER pFileHeader;
    PMANIFEST_HEADER pManifestHeader;
    PMANIFEST_NODE grpManifestNodes;

    // open file
    hFile = CreateFileW(pszFileName, GENERIC_READ | GENERIC_WRITE, 0, NULL,
                        OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
    if (hFile == INVALID_HANDLE_VALUE)
        FatalAppExitW(0, L"Opening file failed");

    // map into memory
    hFileMapping = CreateFileMappingW(hFile, NULL, PAGE_READWRITE, 0, 0, NULL);
    if (!hFileMapping)
        FatalAppExitW(0, L"Cannot map file in memory");

    pBaseAddress = MapViewOfFile(hFileMapping, FILE_MAP_WRITE, 0, 0, 0);
    pData = (PBYTE)pBaseAddress;

    // FileHeader
    pFileHeader = (PFILE_HEADER)pData;
    pData += sizeof(FILE_HEADER);
    // check if file is a valid ncf file
    if (!ValidateFileHeader(pFileHeader))
        FatalAppExitW(0, L"File is not a valid ncf");

    // ManifestHeader
    pManifestHeader = (PMANIFEST_HEADER)pData;
    pData += sizeof(MANIFEST_HEADER);

    // ManifestNodes
    grpManifestNodes = (PMANIFEST_NODE)pData;
    pData += (sizeof(MANIFEST_NODE) * pManifestHeader->dwNodeCount);

    switch (dwOption) {
    case OPTION_SWAP:
        Swap(grpManifestNodes, pManifestHeader->dwNodeCount);
        break;
    case OPTION_ENCRYPT:
        Encrypt(grpManifestNodes, pManifestHeader->dwNodeCount);
        break;
    case OPTION_DECRYPT:
        Decrypt(grpManifestNodes, pManifestHeader->dwNodeCount);
        break;
    }

    // write and close file
    dwOption = UnmapViewOfFile(pBaseAddress);
        CloseHandle(hFileMapping);
        CloseHandle(hFile);
}

int WINAPI Start(void)
{
    PWSTR *ppszArgs;
    DWORD dwOption, i, iNumArgs;

    ppszArgs = CommandLineToArgvW(GetCommandLineW(), &iNumArgs);
    dwOption = OPTION_SWAP;

    for (i = 1; i < iNumArgs; i++) {
        if (ppszArgs[i][0] == '/') {
            switch (ppszArgs[i][1]) {
            case 'S': dwOption = OPTION_SWAP;    break;
            case 'E': dwOption = OPTION_ENCRYPT; break;
            case 'D': dwOption = OPTION_DECRYPT; break;
            }
        } else {
            CryptFile(ppszArgs[i], dwOption);
        }
    }

    return 0;
}