CWE-ou-minkata/Sources/Plasma/PubUtilLib/plFile/plEncryptedStream.cpp

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*==LICENSE==*/
#include "plEncryptedStream.h"

#include "plFileUtils.h"
#include "hsSTLStream.h"

#include <time.h>
#include <wchar.h>

static const uint32_t kDefaultKey[4] = { 0x6c0a5452, 0x3827d0f, 0x3a170b92, 0x16db7fc2 };
static const int kEncryptChunkSize = 8;

static const char* kOldMagicString = "BriceIsSmart";
static const char* kMagicString    = "whatdoyousee";
static const int kMagicStringLen = 12;

static const int kFileStartOffset = kMagicStringLen + sizeof(uint32_t);

static const int kMaxBufferedFileSize = 10*1024;

plEncryptedStream::plEncryptedStream(uint32_t* key) :
    fRef(nil),
    fActualFileSize(0),
    fBufferedStream(false),
    fRAMStream(nil),
    fWriteFileName(nil),
    fOpenMode(kOpenFail)
{
    if (key)
        memcpy(&fKey, key, sizeof(kDefaultKey));
    else
        memcpy(&fKey, &kDefaultKey, sizeof(kDefaultKey));
}

plEncryptedStream::~plEncryptedStream()
{
}

//
// Tiny Encryption Algorithm
// http://vader.brad.ac.uk/tea/tea.shtml
//
// A potential weakness in this implementation is the fact that a known value
// (length of the original file) is written at the start of the encrypted file.  -Colin
//
// Oh, and also there's some kind of potential weakness in TEA that they fixed with XTEA,
// but frankly, who cares.  No one is going to break the encryption, they'll just get the
// key out of the exe or memory.
//
void plEncryptedStream::IEncipher(uint32_t* const v)
{
    register uint32_t y=v[0], z=v[1], sum=0, delta=0x9E3779B9, n=32;

    while (n-- > 0)
    {
        y += (z << 4 ^ z >> 5) + z ^ sum + fKey[sum&3];
        sum += delta;
        z += (y << 4 ^ y >> 5) + y ^ sum + fKey[sum>>11 & 3];
    }

   v[0]=y; v[1]=z;
}

void plEncryptedStream::IDecipher(uint32_t* const v)
{
    register uint32_t y=v[0], z=v[1], sum=0xC6EF3720, delta=0x9E3779B9, n=32;

    // sum = delta<<5, in general sum = delta * n

    while (n-- > 0)
    {
        z -= (y << 4 ^ y >> 5) + y ^ sum + fKey[sum>>11 & 3];
        sum -= delta;
        y -= (z << 4 ^ z >> 5) + z ^ sum + fKey[sum&3];
    }
   
    v[0]=y; v[1]=z;
}

bool plEncryptedStream::Open(const plFileName& name, const char* mode)
{
    if (strcmp(mode, "rb") == 0)
    {
        fRef = plFileSystem::Open(name, mode);
        fPosition = 0;

        if (!fRef)
            return false;

        // Make sure our special magic string is there
        if (!ICheckMagicString(fRef))
        {
            fclose(fRef);
            return false;
        }

        fread(&fActualFileSize, sizeof(uint32_t), 1, fRef);

        // The encrypted stream is inefficient if you do reads smaller than
        // 8 bytes.  Since we do a lot of those, any file under a size threshold
        // is buffered in memory
        if (fActualFileSize <= kMaxBufferedFileSize)
            IBufferFile();

        fOpenMode = kOpenRead;

        return true;
    }
    else if (strcmp(mode, "wb") == 0)
    {
        fRAMStream = new hsVectorStream;
        fWriteFileName = name;
        fPosition = 0;

        fOpenMode = kOpenWrite;
        fBufferedStream = true;

        return true;
    }
    else
    {
        hsAssert(0, "Unsupported open mode");
        fOpenMode = kOpenFail;
        return false;
    }
}

bool plEncryptedStream::Close()
{
    int rtn = false;

    if (fOpenMode == kOpenWrite)
    {
        fRAMStream->Rewind();
        rtn = IWriteEncypted(fRAMStream, fWriteFileName);
    }
    if (fRef)
    {
        rtn = (fclose(fRef) == 0);
        fRef = nil;
    }

    if (fRAMStream)
    {
        delete fRAMStream;
        fRAMStream = nil;
    }

    fWriteFileName = plString::Null;
    fActualFileSize = 0;
    fBufferedStream = false;
    fOpenMode = kOpenFail;

    return rtn;
}

uint32_t plEncryptedStream::IRead(uint32_t bytes, void* buffer)
{
    if (!fRef)
        return 0;
    int numItems = (int)(::fread(buffer, 1 /*size*/, bytes /*count*/, fRef));
    fBytesRead += numItems;
    fPosition += numItems;
    if ((unsigned)numItems < bytes) {
        if (feof(fRef)) {
            // EOF ocurred
            char str[128];
            sprintf(str, "Hit EOF on UNIX Read, only read %d out of requested %d bytes\n", numItems, bytes);
            hsDebugMessage(str, 0);
        }
        else {
            hsDebugMessage("Error on UNIX Read", ferror(fRef));
        }
    }
    return numItems;
}

void plEncryptedStream::IBufferFile()
{
    fRAMStream = new hsVectorStream;
    char buf[1024];
    while (!AtEnd())
    {
        uint32_t numRead = Read(1024, buf);
        fRAMStream->Write(numRead, buf);
    }
    fRAMStream->Rewind();

    fBufferedStream = true;
    fclose(fRef);
    fRef = nil;
    fPosition = 0;
}

bool plEncryptedStream::AtEnd()
{
    if (fBufferedStream)
        return fRAMStream->AtEnd();
    else
        return (GetPosition() == fActualFileSize);
}

void plEncryptedStream::Skip(uint32_t delta)
{
    if (fBufferedStream)
    {
        fRAMStream->Skip(delta);
        fPosition = fRAMStream->GetPosition();
    }
    else if (fRef)
    {
        fBytesRead += delta;
        fPosition += delta;
        fseek(fRef, delta, SEEK_CUR);
    }
}

void plEncryptedStream::Rewind()
{
    if (fBufferedStream)
    {
        fRAMStream->Rewind();
        fPosition = fRAMStream->GetPosition();
    }
    else if (fRef)
    {
        fBytesRead = 0;
        fPosition = 0;
        fseek(fRef, kFileStartOffset, SEEK_SET);
    }
}

void plEncryptedStream::FastFwd()
{
    if (fBufferedStream)
    {
        fRAMStream->FastFwd();
        fPosition = fRAMStream->GetPosition();
    }
    else if (fRef)
    {
        fseek(fRef, kFileStartOffset+fActualFileSize, SEEK_SET);
        fBytesRead = fPosition = ftell(fRef);
    }
}

uint32_t plEncryptedStream::GetEOF()
{
    return fActualFileSize;
}

uint32_t plEncryptedStream::Read(uint32_t bytes, void* buffer)
{
    if (fBufferedStream)
    {
        uint32_t numRead = fRAMStream->Read(bytes, buffer);
        fPosition = fRAMStream->GetPosition();
        return numRead;
    }

    uint32_t startPos = fPosition;

    // Offset into the first buffer (0 if we are aligned on a chunk, which means no extra block read)
    uint32_t startChunkPos = startPos % kEncryptChunkSize;
    // Amount of data in the partial first chunk (0 if we're aligned)
    uint32_t startAmt = (startChunkPos != 0) ? hsMinimum(kEncryptChunkSize - startChunkPos, bytes) : 0;

    uint32_t totalNumRead = IRead(bytes, buffer);

    uint32_t numMidChunks = (totalNumRead - startAmt) / kEncryptChunkSize;
    uint32_t endAmt = (totalNumRead - startAmt) % kEncryptChunkSize;

    // If the start position is in the middle of a chunk we need to rewind and
    // read that whole chunk in and decrypt it.
    if (startChunkPos != 0)
    {
        // Move to the start of this chunk
        SetPosition(startPos-startChunkPos);

        // Read in the chunk and decrypt it
        char buf[kEncryptChunkSize];
        uint32_t numRead = IRead(kEncryptChunkSize, &buf);
        IDecipher((uint32_t*)&buf);

        // Copy the relevant portion to the output buffer
        memcpy(buffer, &buf[startChunkPos], startAmt);

        SetPosition(startPos+totalNumRead);
    }

    if (numMidChunks != 0)
    {
        uint32_t* bufferPos = (uint32_t*)(((char*)buffer)+startAmt);
        for (int i = 0; i < numMidChunks; i++)
        {
            // Decrypt chunk
            IDecipher(bufferPos);
            bufferPos += (kEncryptChunkSize / sizeof(uint32_t));
        }
    }

    if (endAmt != 0)
    {
        // Read in the final chunk and decrypt it
        char buf[kEncryptChunkSize];
        SetPosition(startPos + startAmt + numMidChunks*kEncryptChunkSize);
        uint32_t numRead = IRead(kEncryptChunkSize, &buf);
        IDecipher((uint32_t*)&buf);

        memcpy(((char*)buffer)+totalNumRead-endAmt, &buf, endAmt);
        
        SetPosition(startPos+totalNumRead);
    }

    // If we read into the padding at the end, update the total read to not include that
    if (totalNumRead > 0 && startPos + totalNumRead > fActualFileSize)
    {
        totalNumRead -= (startPos + totalNumRead) - fActualFileSize;
        SetPosition(fActualFileSize);
    }

    return totalNumRead;
}

uint32_t plEncryptedStream::Write(uint32_t bytes, const void* buffer)
{
    if (fOpenMode != kOpenWrite)
    {
        hsAssert(0, "Trying to write to a read stream");
        return 0;
    }

    return fRAMStream->Write(bytes, buffer);
}

bool plEncryptedStream::IWriteEncypted(hsStream* sourceStream, const plFileName& outputFile)
{
    hsUNIXStream outputStream;

    if (!outputStream.Open(outputFile, "wb"))
        return false;

    outputStream.Write(kMagicStringLen, kMagicString);

    // Save some space to write the file size at the end
    outputStream.WriteLE32(0);

    // Write out all the full size encrypted blocks we can
    char buf[kEncryptChunkSize];
    uint32_t amtRead;
    while ((amtRead = sourceStream->Read(kEncryptChunkSize, &buf)) == kEncryptChunkSize)
    {
        IEncipher((uint32_t*)&buf);
        outputStream.Write(kEncryptChunkSize, &buf);
    }

    // Pad with random data and write out the final partial block, if there is one
    if (amtRead > 0)
    {
        static bool seededRand = false;
        if (!seededRand)
        {
            seededRand = true;
            srand((unsigned int)time(nil));
        }

        for (int i = amtRead; i < kEncryptChunkSize; i++)
            buf[i] = rand();

        IEncipher((uint32_t*)&buf);

        outputStream.Write(kEncryptChunkSize, &buf);
    }

    // Write the original file size at the start
    uint32_t actualSize = sourceStream->GetPosition();
    outputStream.Rewind();
    outputStream.Skip(kMagicStringLen);
    outputStream.WriteLE32(actualSize);

    outputStream.Close();

    return true;
}

bool plEncryptedStream::FileEncrypt(const plFileName& fileName)
{
    hsUNIXStream sIn;
    if (!sIn.Open(fileName))
        return false;

    // Don't double encrypt any files
    if (ICheckMagicString(sIn.GetFILE()))
    {
        sIn.Close();
        return true;
    }
    sIn.Rewind();

    plEncryptedStream sOut;
    bool wroteEncrypted = sOut.IWriteEncypted(&sIn, "crypt.dat");

    sIn.Close();
    sOut.Close();

    if (wroteEncrypted)
    {
        plFileSystem::Unlink(fileName);
        plFileSystem::Move("crypt.dat", fileName);
    }

    return true;
}

bool plEncryptedStream::FileDecrypt(const plFileName& fileName)
{
    plEncryptedStream sIn;
    if (!sIn.Open(fileName))
        return false;

    hsUNIXStream sOut;
    if (!sOut.Open("crypt.dat", "wb"))
    {
        sIn.Close();
        return false;
    }

    char buf[1024];

    while (!sIn.AtEnd())
    {
        uint32_t numRead = sIn.Read(sizeof(buf), buf);
        sOut.Write(numRead, buf);
    }

    sIn.Close();
    sOut.Close();

    plFileSystem::Unlink(fileName);
    plFileSystem::Move("crypt.dat", fileName);

    return true;
}

bool plEncryptedStream::ICheckMagicString(FILE* fp)
{
    char magicString[kMagicStringLen];
    fread(&magicString, kMagicStringLen, 1, fp);
    return memcmp(magicString, kMagicString, kMagicStringLen) == 0 ||
           memcmp(magicString, kOldMagicString, kMagicStringLen) == 0;
}

bool plEncryptedStream::IsEncryptedFile(const plFileName& fileName)
{
    FILE* fp = plFileSystem::Open(fileName, "rb");
    if (!fp)
        return false;

    bool isEncrypted = ICheckMagicString(fp);

    fclose(fp);

    return isEncrypted;
}

hsStream* plEncryptedStream::OpenEncryptedFile(const plFileName& fileName, uint32_t* cryptKey)
{

    bool isEncrypted = IsEncryptedFile(fileName);

    hsStream* s = nil;
    if (isEncrypted)
        s = new plEncryptedStream(cryptKey);
    else
        s = new hsUNIXStream;

    s->Open(fileName, "rb");
    return s;
}

hsStream* plEncryptedStream::OpenEncryptedFileWrite(const plFileName& fileName, uint32_t* cryptKey)
{
    hsStream* s = nil;
    if (IsEncryptedFile(fileName))
        s = new plEncryptedStream(cryptKey);
    else
        s = new hsUNIXStream;

    s->Open(fileName, "wb");
    return s;
}