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

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*==LICENSE==*/
#include <string>
#include <ctime>

#include "plSecureStream.h"
#include "hsWindows.h"

#include "hsSTLStream.h"

#if !HS_BUILD_FOR_WIN32
#include <errno.h>
#define INVALID_HANDLE_VALUE 0
#endif

// our default encryption key
const uint32_t plSecureStream::kDefaultKey[4] = { 0x6c0a5452, 0x3827d0f, 0x3a170b92, 0x16db7fc2 };

static const int kEncryptChunkSize = 8;

static const char* kMagicString    = "notthedroids";
static const int kMagicStringLen = 12;

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

static const int kMaxBufferedFileSize = 10*1024;

const char plSecureStream::kKeyFilename[] = "encryption.key";

plSecureStream::plSecureStream(bool deleteOnExit, uint32_t* key) :
fRef(INVALID_HANDLE_VALUE),
fActualFileSize(0),
fBufferedStream(false),
fRAMStream(nil),
fOpenMode(kOpenFail),
fDeleteOnExit(deleteOnExit)
{
    if (key)
        memcpy(&fKey, key, sizeof(kDefaultKey));
    else
        memcpy(&fKey, &kDefaultKey, sizeof(kDefaultKey));
}

plSecureStream::plSecureStream(hsStream* base, uint32_t* key) :
fRef(INVALID_HANDLE_VALUE),
fActualFileSize(0),
fBufferedStream(false),
fRAMStream(nil),
fOpenMode(kOpenFail),
fDeleteOnExit(false)
{
    if (key)
        memcpy(&fKey, key, sizeof(kDefaultKey));
    else
        memcpy(&fKey, &kDefaultKey, sizeof(kDefaultKey));
    Open(base);
}

plSecureStream::~plSecureStream()
{
}

//
// XXTEA
// http://www-users.cs.york.ac.uk/~matthew/TEA/
//
// 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
//

#define MX (z>>5 ^ y<<2) + (y>>3 ^ z<<4) ^ (sum^y) + (fKey[p&3^e]^z)

void plSecureStream::IEncipher(uint32_t* const v, uint32_t n)
{
    unsigned long y=v[0], z=v[n-1], e, delta=0x9E3779B9;
    unsigned long q = 6 + 52/n, p, sum = 0;

    while (q-- > 0)
    {
        sum += delta;
        e = (sum >> 2) & 3;
        for (p = 0; p < n - 1; p++)
        {
            y = v[p + 1];
            v[p] += MX;
            z = v[p];
        }
        y = v[0];
        v[n - 1] += MX;
        z = v[n - 1];
    }
}

void plSecureStream::IDecipher(uint32_t* const v, uint32_t n)
{
    unsigned long y=v[0], z=v[n-1], e, delta=0x9E3779B9;
    unsigned long q = 6 + 52/n, p, sum = q * delta;

    while (sum > 0)
    {
        e = (sum >> 2) & 3;
        for (p = n - 1; p > 0; p--)
        {
            z = v[p - 1];
            v[p] -= MX;
            y = v[p];
        }
        z = v[n - 1];
        v[0] -= MX;
        y = v[0];
        sum -= delta;
    }
}

bool plSecureStream::Open(const plFileName& name, const char* mode)
{
    if (strcmp(mode, "rb") == 0)
    {
#if HS_BUILD_FOR_WIN32
        if (fDeleteOnExit)
        {
            fRef = CreateFileW(name.AsString().ToWchar(),
                                GENERIC_READ,   // open for reading
                                0,              // no one can open the file until we're done
                                NULL,           // default security
                                OPEN_EXISTING,  // only open existing files (no creation)
                                FILE_FLAG_DELETE_ON_CLOSE,  // delete the file from disk when we close the handle
                                NULL);          // no template
        }
        else
        {
            fRef = CreateFileW(name.AsString().ToWchar(),
                                GENERIC_READ,   // open for reading
                                0,              // no one can open the file until we're done
                                NULL,           // default security
                                OPEN_EXISTING,  // only open existing files (no creation)
                                FILE_ATTRIBUTE_NORMAL,  // normal file attributes
                                NULL);          // no template
        }

        fPosition = 0;

        if (fRef == INVALID_HANDLE_VALUE)
            return false;

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

        DWORD numBytesRead;
        ReadFile(fRef, &fActualFileSize, sizeof(uint32_t), &numBytesRead, NULL);
#elif HS_BUILD_FOR_UNIX
        fRef = plFileSystem::Open(name, "rb");
        fPosition = 0;

        if (fRef == INVALID_HANDLE_VALUE)
            return false;

        if (!ICheckMagicString(fRef))
        {
            fclose(fRef);
            fRef = INVALID_HANDLE_VALUE;
            return false;
        }
#endif

        // 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 plSecureStream::Open(hsStream* stream)
{
    uint32_t pos = stream->GetPosition();
    stream->Rewind();
    if (!ICheckMagicString(stream))
        return false;

    fActualFileSize = stream->ReadLE32();
    uint32_t trimSize = kMagicStringLen + sizeof(uint32_t) + fActualFileSize;
    fRAMStream = new hsRAMStream;
    while (!stream->AtEnd())
    {
        // Don't write out any garbage
        uint32_t size;
        if ((trimSize - stream->GetPosition()) < kEncryptChunkSize)
            size = (trimSize - stream->GetPosition());
        else
            size = kEncryptChunkSize;

        uint8_t buf[kEncryptChunkSize];
        stream->Read(kEncryptChunkSize, &buf);
        IDecipher((uint32_t*)&buf, kEncryptChunkSize / sizeof(uint32_t));
        fRAMStream->Write(size, &buf);
    }

    stream->SetPosition(pos);
    fRAMStream->Rewind();
    fPosition = 0;
    fBufferedStream = true;
    fOpenMode = kOpenRead;
    return true;
}

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

    if (fOpenMode == kOpenWrite)
    {
        fRAMStream->Rewind();
        rtn = IWriteEncrypted(fRAMStream, fWriteFileName);
    }
    if (fRef != INVALID_HANDLE_VALUE)
    {
#if HS_BUILD_FOR_WIN32
        rtn = CloseHandle(fRef);
#elif HS_BUILD_FOR_UNIX
        rtn = fclose(fRef);
#endif
        fRef = INVALID_HANDLE_VALUE;
    }

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

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

    return rtn;
}

uint32_t plSecureStream::IRead(uint32_t bytes, void* buffer)
{
    if (fRef == INVALID_HANDLE_VALUE)
        return 0;
    uint32_t numItems;
#if HS_BUILD_FOR_WIN32
    bool success = (ReadFile(fRef, buffer, bytes, (LPDWORD)&numItems, NULL) != 0);
#elif HS_BUILD_FOR_UNIX
    numItems = fread(buffer, bytes, 1, fRef);
    bool success = numItems != 0;
#endif
    fBytesRead += numItems;
    fPosition += numItems;
    if ((unsigned)numItems < bytes)
    {
        if (success)
        {
            // EOF ocurred
            char str[128];
            sprintf(str, "Hit EOF on Windows read, only read %d out of requested %d bytes\n", numItems, bytes);
            hsDebugMessage(str, 0);
        }
        else
        {
#if HS_BUILD_FOR_WIN32
            hsDebugMessage("Error on Windows read", GetLastError());
#else
            hsDebugMessage("Error on POSIX read", errno);
#endif
        }
    }
    return numItems;
}

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

    fBufferedStream = true;
#if HS_BUILD_FOR_WIN32
    CloseHandle(fRef);
#elif HS_BUILD_FOR_UNIX
    fclose(fRef);
#endif
    fRef = INVALID_HANDLE_VALUE;
    fPosition = 0;
}

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

void plSecureStream::Skip(uint32_t delta)
{
    if (fBufferedStream)
    {
        fRAMStream->Skip(delta);
        fPosition = fRAMStream->GetPosition();
    }
    else if (fRef != INVALID_HANDLE_VALUE)
    {
        fBytesRead += delta;
        fPosition += delta;
#if HS_BUILD_FOR_WIN32
        SetFilePointer(fRef, delta, 0, FILE_CURRENT);
#elif HS_BUILD_FOR_UNIX
        fseek(fRef, delta, SEEK_CUR);
#endif
    }
}

void plSecureStream::Rewind()
{
    if (fBufferedStream)
    {
        fRAMStream->Rewind();
        fPosition = fRAMStream->GetPosition();
    }
    else if (fRef != INVALID_HANDLE_VALUE)
    {
        fBytesRead = 0;
        fPosition = 0;
#if HS_BUILD_FOR_WIN32
        SetFilePointer(fRef, kFileStartOffset, 0, FILE_BEGIN);
#elif HS_BUILD_FOR_UNIX
        fseek(fRef, kFileStartOffset, SEEK_SET);
#endif
    }
}

void plSecureStream::FastFwd()
{
    if (fBufferedStream)
    {
        fRAMStream->FastFwd();
        fPosition = fRAMStream->GetPosition();
    }
    else if (fRef != INVALID_HANDLE_VALUE)
    {
#if HS_BUILD_FOR_WIN32
        fBytesRead = fPosition = SetFilePointer(fRef, kFileStartOffset + fActualFileSize, 0, FILE_BEGIN);
#elif HS_BUILD_FOR_UNIX
        fBytesRead = fPosition = fseek(fRef, 0, SEEK_END);
#endif
    }
}

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

uint32_t plSecureStream::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) ? std::min(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, kEncryptChunkSize / sizeof(uint32_t));

        // 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, kEncryptChunkSize / sizeof(uint32_t));
            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, kEncryptChunkSize / sizeof(uint32_t));

        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 plSecureStream::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 plSecureStream::IWriteEncrypted(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, kEncryptChunkSize / sizeof(uint32_t));
        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, kEncryptChunkSize / sizeof(uint32_t));

        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 plSecureStream::FileEncrypt(const plFileName& fileName, uint32_t* key /* = nil */)
{
    hsUNIXStream sIn;
    if (!sIn.Open(fileName))
        return false;

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

    plSecureStream sOut(false, key);
    bool wroteEncrypted = sOut.IWriteEncrypted(&sIn, "crypt.dat");

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

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

    return true;
}

bool plSecureStream::FileDecrypt(const plFileName& fileName, uint32_t* key /* = nil */)
{
    plSecureStream sIn(false, key);
    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 plSecureStream::ICheckMagicString(hsStream* s)
{
    char magicString[kMagicStringLen+1];
    s->Read(kMagicStringLen, &magicString);
    magicString[kMagicStringLen] = '\0';
    return (strcmp(magicString, kMagicString) == 0);
}

bool plSecureStream::ICheckMagicString(hsFD fp)
{
    char magicString[kMagicStringLen+1];
#ifdef HS_BUILD_FOR_WIN32
    DWORD numread;
    ReadFile(fp, &magicString, kMagicStringLen, &numread, NULL);
#elif HS_BUILD_FOR_UNIX
    fread(&magicString, kMagicStringLen, 1, fp);
#endif
    magicString[kMagicStringLen] = '\0';
    return (strcmp(magicString, kMagicString) == 0);
}

bool plSecureStream::IsSecureFile(const plFileName& fileName)
{
    hsFD fp = INVALID_HANDLE_VALUE;

#if HS_BUILD_FOR_WIN32
    fp = CreateFileW(fileName.AsString().ToWchar(),
        GENERIC_READ,   // open for reading
        0,              // no one can open the file until we're done
        NULL,           // default security
        OPEN_EXISTING,  // only open existing files (no creation)
        FILE_ATTRIBUTE_NORMAL,  // normal file attributes
        NULL);          // no template
#elif HS_BUILD_FOR_UNIX
    fp = plFileSystem::Open(fileName, "rb");
#endif

    if (fp == INVALID_HANDLE_VALUE)
        return false;

    bool isEncrypted = ICheckMagicString(fp);

#if HS_BUILD_FOR_WIN32
    CloseHandle(fp);
#elif HS_BUILD_FOR_UNIX
    fclose(fp);
#endif

    return isEncrypted;
}

hsStream* plSecureStream::OpenSecureFile(const plFileName& fileName, const uint32_t flags /* = kRequireEncryption */, uint32_t* key /* = nil */)
{
    bool requireEncryption = flags & kRequireEncryption;
    bool deleteOnExit = flags & kDeleteOnExit;
    bool isEncrypted = IsSecureFile(fileName);

    hsStream* s = nullptr;
    if (isEncrypted)
        s = new plSecureStream(deleteOnExit, key);
    else if (!requireEncryption)
        s = new hsUNIXStream;

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

hsStream* plSecureStream::OpenSecureFileWrite(const plFileName& fileName, uint32_t* key /* = nil */)
{
    hsStream* s = nil;
#ifdef PLASMA_EXTERNAL_RELEASE
    s = new plSecureStream(false, key);
#else
    s = new hsUNIXStream;
#endif

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

//// GetSecureEncryptionKey //////////////////////////////////////////////////

bool plSecureStream::GetSecureEncryptionKey(const plFileName& filename, uint32_t* key, unsigned length)
{
    // looks for an encryption key file in the same directory, and reads it
    plFileName keyFile = plFileName::Join(filename.StripFileName(), kKeyFilename);

    if (plFileInfo(keyFile).Exists())
    {
        // file exists, read from it
        hsUNIXStream file;
        file.Open(keyFile, "rb");

        unsigned bytesToRead = length * sizeof(uint32_t);
        uint8_t* buffer = (uint8_t*)malloc(bytesToRead);
        unsigned bytesRead = file.Read(bytesToRead, buffer);

        file.Close();

        unsigned memSize = std::min(bytesToRead, bytesRead);
        memcpy(key, buffer, memSize);
        free(buffer);

        return true;
    }

    // file doesn't exist, use default key
    unsigned memSize = std::min(size_t(length), arrsize(plSecureStream::kDefaultKey));
    memSize *= sizeof(uint32_t);
    memcpy(key, plSecureStream::kDefaultKey, memSize);

    return false;
}