Crypto ++导致应用程序失败

Question

I am developing an AIR Native Extension of Crypto++ for Flash which I will release as public domain. I started with some code to test hashing (with SHA-256 in this case) but for some reason CryptoPP::SHA256().CalculateDigest(abDigest, pbData, nDataLen); (as discovered by the process of elimination) causes the Flash compiler to not recognize any available methods (The extension context does not have a method with the name isSupported.):

Here's the full C++ code:

FREObject isSupported(FREContext ctx, void* funcData, uint32_t argc, FREObject argv[])
{
    FREObject result;

    uint32_t isSupportedSwitch = 1;
    FRENewObjectFromBool(isSupportedSwitch, &result);

    return result;
}

FREObject computeHash(FREContext ctx, void* funcData, uint32_t argc, FREObject argv[])
{
    FREObject result;
    FREByteArray actualBytes;

    FREAcquireByteArray(argv[0], &actualBytes);

    byte const* pbData = (byte*) actualBytes.bytes;
    unsigned int nDataLen = strlen((const char*) pbData);
    byte abDigest[CryptoPP::SHA256::DIGESTSIZE];
    CryptoPP::SHA256().CalculateDigest(abDigest, pbData, nDataLen);

    memcpy(actualBytes.bytes, (uint8_t*) abDigest, 32);

    FREReleaseByteArray(argv[0]);

    FRENewObjectFromBool(1, &result);
    return result;
}

void testContextInitializer(void* extData, const uint8_t* ctxType, FREContext ctx, uint32_t* numFunctions, const FRENamedFunction** functions)
{
    *numFunctions = 2;

    FRENamedFunction* func = (FRENamedFunction*) malloc(sizeof(FRENamedFunction) * (*numFunctions));

    func[0].name = (const uint8_t*) "isSupported";
    func[0].functionData = NULL;
    func[0].function = &isSupported;

    func[1].name = (const uint8_t*) "computeHash";
    func[1].functionData = NULL;
    func[1].function = &computeHash;

    *functions = func;
}

void testContextFinalizer(FREContext ctx)
{
    return;
}

void testInitializer(void** extData, FREContextInitializer* ctxInitializer, FREContextFinalizer* ctxFinalizer)
{
    *ctxInitializer = &testContextInitializer;
    *ctxFinalizer = &testContextFinalizer;
}

void testFinalizer(void* extData)
{
    return;
}

Any help on this would be deeply appreciated and would go a long way in helping me in this project.

EDIT: To clarify, I am asking why CryptoPP::SHA256().CalculateDigest(abDigest, pbData, nDataLen); causes the application failure mentioned above and possible ways to fix it.

Answer 1

It looks like you're assuming that actualBytes.bytes is a pointer to a block of memory that is at least 32 bytes, since you've hard-coded 32 as the third argument in memcpy.

This is probably an invalid assumption and you should check to make sure that actualBytes.length >= 32 before performing the memcpy

The safest approach might be to ensure that you've allocated a sufficiently large block of memory from the ActionScript side. Alternatively you could try allocating memory in C++ and then modifying the actualBytes contents to point to that allocation and change the length value. But this definitely seems frought with dangers.