devilution/Source/codec.cpp at master · berney/devilution · GitHub

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//HEADER_GOES_HERE

#include "../types.h"

int __fastcall codec_decode(void *pbSrcDst, int size, char *pszPassword)
{
	unsigned int v3; // ebx
	char *v4;        // esi
	int v5;          // ebx
	signed int v7;   // ecx
	int v8;          // esi
	char v9[128];    // [esp+8h] [ebp-98h]
	char dst[20];    // [esp+88h] [ebp-18h]
	int v11;         // [esp+9Ch] [ebp-4h]
	char *passworda; // [esp+A8h] [ebp+8h]

	v3 = size;
	v4 = (char *)pbSrcDst;
	codec_init_key(0, pszPassword);
	if (v3 <= 8)
		return 0;
	v5 = v3 - 8;
	v11 = v5;
	if (v5 & 0x3F)
		return 0;
	passworda = (char *)v5;
	if (v5) {
		do {
			memcpy(v9, v4, 0x40u);
			SHA1Result(0, dst);
			v7 = 0;
			do {
				v9[v7] ^= dst[v7 % 20];
				++v7;
			} while (v7 < 64);
			SHA1Calculate(0, v9, NULL);
			memset(dst, 0, sizeof(dst));
			memcpy(v4, v9, 0x40u);
			v4 += 64;
			passworda -= 64;
		} while (passworda);
		v5 = v11;
	}
	memset(v9, 0, sizeof(v9));
	if (!v4[4]) {
		SHA1Result(0, dst);
		if (*(_DWORD *)v4 == *(_DWORD *)dst) {
			v8 = v5 + (unsigned char)v4[5] - 64;
			goto LABEL_14;
		}
		memset(dst, 0, sizeof(dst));
	}
	v8 = 0;
LABEL_14:
	SHA1Clear();
	return v8;
}
// 4034D9: using guessed type char var_98[128];

void __fastcall codec_init_key(int unused, char *pszPassword)
{
	int i, ch, n;
	char key[136]; // last 64 bytes are the SHA1
	char pw[64];
	char digest[SHA1HashSize];
	char *keyInit;

	srand(0x7058);

	keyInit = key;
	for (i = 0; i < 136; i++) {
		*keyInit = rand();
		keyInit++;
	}
	ch = 0;
	for (i = 0; i < 64; i++) {
		if (!pszPassword[ch])
			ch = 0;
		pw[i] = pszPassword[ch];
		ch++;
	}
	SHA1Reset(0);
	SHA1Calculate(0, pw, digest);
	SHA1Clear();
	for (i = 0; (DWORD)i < 136; i++)
		key[i] ^= digest[i % 20];
	memset(pw, 0, sizeof(pw));
	memset(digest, 0, sizeof(digest));
	for (n = 0; n < 3; n++) {
		SHA1Reset(n);
		SHA1Calculate(n, &key[72], NULL);
	}
	memset(key, 0, sizeof(key));
}
// 4035DB: using guessed type char var_E0[72];
// 4035DB: using guessed type char var_58[64];
// 4035DB: using guessed type char dst[20];

int __fastcall codec_get_encoded_len(int dwSrcBytes)
{
	if (dwSrcBytes & 0x3F)
		dwSrcBytes += 64 - (dwSrcBytes & 0x3F);
	return dwSrcBytes + 8;
}

void __fastcall codec_encode(void *pbSrcDst, int size, int size_64, char *pszPassword)
{
	char *v4;      // esi
	char v5;       // bl
	size_t v6;     // edi
	signed int v7; // ecx
	char v9[128];  // [esp+8h] [ebp-ACh]
	char v10[20];  // [esp+88h] [ebp-2Ch]
	char dst[20];  // [esp+9Ch] [ebp-18h]
	size_t v12;    // [esp+B0h] [ebp-4h]

	v4 = (char *)pbSrcDst;
	v12 = size;
	if (size_64 != codec_get_encoded_len(size))
		TermMsg("Invalid encode parameters");
	codec_init_key(1, pszPassword);
	v5 = 0;
	if (v12) {
		do {
			v6 = v12;
			if (v12 >= 0x40)
				v6 = 64;
			memcpy(v9, v4, v6);
			if (v6 < 0x40)
				memset(&v9[v6], 0, 64 - v6);
			SHA1Result(0, dst);
			SHA1Calculate(0, v9, NULL);
			v7 = 0;
			do {
				v9[v7] ^= dst[v7 % 20];
				++v7;
			} while (v7 < 64);
			memset(dst, 0, sizeof(dst));
			memcpy(v4, v9, 0x40u);
			v4 += 64;
			v12 -= v6;
		} while (v12);
		v5 = v6;
	}
	memset(v9, 0, sizeof(v9));
	SHA1Result(0, v10);
	v4[4] = 0;
	*((_WORD *)v4 + 3) = 0;
	*(_DWORD *)v4 = *(_DWORD *)v10;
	v4[5] = v5;
	SHA1Clear();
}
// 4036BE: using guessed type char var_AC[128];
// 4036BE: using guessed type char dst[20];