102 lines
2.8 KiB
C
102 lines
2.8 KiB
C
#ifndef _MC161_STREAMFILE_H_
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#define _MC161_STREAMFILE_H_
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#include "../streamfile.h"
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typedef struct {
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int32_t base_key;
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int32_t curr_key;
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uint32_t curr_offset;
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} mc161_io_data;
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static void decrypt_chunk(uint8_t* buf, int buf_size, mc161_io_data* data) {
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int i;
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int32_t hash = data->curr_key;
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for (i = 0; i < buf_size; i++) {
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buf[i] = (uint8_t)(buf[i] ^ ((hash >> 8) & 0xFF));
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hash = (int32_t)(hash * 498729871) + (85731 * (int8_t)buf[i]); /* signed */
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}
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data->curr_key = hash;
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data->curr_offset += buf_size;
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}
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static void update_key(STREAMFILE* sf, off_t offset, mc161_io_data* data) {
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uint8_t buf[0x800];
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size_t bytes;
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size_t to_skip;
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if (offset < data->curr_offset || offset == 0x00) {
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data->curr_key = data->base_key;
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data->curr_offset = 0x00;
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to_skip = offset;
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}
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else {
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to_skip = offset - data->curr_offset;
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}
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/* update key by reading and decrypt all data between current offset + last known key to requested offset */
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while (to_skip > 0) {
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size_t read_size = sizeof(buf);
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if (read_size > to_skip)
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read_size = to_skip;
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bytes = read_streamfile(buf, data->curr_offset, read_size, sf);
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if (!bytes) /* ??? */
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break;
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decrypt_chunk(buf, bytes, data); /* updates curr_offset and key */
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to_skip -= bytes;
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}
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}
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/* XOR depends on decrypted data, meanings having to decrypt linearly to reach some offset. */
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static size_t mc161_io_read(STREAMFILE* sf, uint8_t* dest, off_t offset, size_t length, mc161_io_data* data) {
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size_t bytes;
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/* read and decrypt unneded data */
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update_key(sf, offset, data);
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/* read and decrypt current data */
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bytes = read_streamfile(dest, offset, length, sf);
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decrypt_chunk(dest, bytes, data);
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return bytes;
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}
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/* String.hashCode() should be equivalent to this on Windows (though implementation-defined), note Java has no unsigned */
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static int32_t mc161_get_java_hashcode(STREAMFILE* sf) {
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char filename[1024];
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int i = 0;
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int32_t hash = 0;
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get_streamfile_filename(sf, filename, sizeof(filename));
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while (filename[i] != '\0') {
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hash = 31 * hash + (uint8_t)filename[i];
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i++;
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}
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return hash;
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}
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/* decrypts Minecraft old streams (some info from: https://github.com/ata4/muscode) */
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static STREAMFILE* setup_mc161_streamfile(STREAMFILE* sf) {
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STREAMFILE* new_sf = NULL;
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mc161_io_data io_data = {0};
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io_data.base_key = mc161_get_java_hashcode(sf);
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io_data.curr_key = io_data.base_key;
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io_data.curr_offset = 0x00;
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new_sf = open_wrap_streamfile(sf);
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new_sf = open_io_streamfile_f(new_sf, &io_data, sizeof(mc161_io_data), mc161_io_read, NULL);
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new_sf = open_fakename_streamfile_f(new_sf, NULL, "ogg");
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return new_sf;
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}
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#endif /* _MC161_STREAMFILE_H_ */
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