Minecraft Pi Patched.

README.md

MCPI Patched

How to use this patch?

First, you'll need to make sure you have libsdl2-dev and libopengl-dev installed:

sudo apt-get install -y libsdl2-dev libopengl-dev

If the second isn't avaiable, install libgl-dev.

Then compile it as following:

gcc -shared -fPIC preload.c -o preload.so

To use it, give the mcpi-patch.sh execution permissions (with sudo chmod a+x mcpi-patch.sh, for example), and replace PRELOAD_PATH_HERE with the path of the preload.so file.

mcpi-patch.sh

#!/bin/sh

cd /opt/minecraft-pi

if grep -q okay /proc/device-tree/soc/v3d@7ec00000/status \
	/proc/device-tree/soc/firmwarekms@7e600000/status 2> /dev/null; then
	export LD_PRELOAD=libbcm_host.so.1.0
	export LD_LIBRARY_PATH=./lib/mesa
else
	export LD_LIBRARY_PATH=./lib/brcm
fi

export LD_PRELOAD=PRELOAD_PATH_HERE # Replace `PRELOAD_PATH_HERE` with the actual preload.so path.

./minecraft-pi

preload.c

/*
 * preload.c - Minecraft Pi Dynamic Patches.
 * 
 * Copyright 2020 Alvarito050506 <donfrutosgomez@gmail.com>
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2 of the License.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA 02110-1301, USA.
 * 
 * 
 */

#define _GNU_SOURCE /* Required for RTLD_NEXT */

/* Lots of standard includes and libraries, for types and function prototypes. */
#include <stdio.h>
#include <dlfcn.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <stdint.h>
#include <libgen.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/user.h>
#include <sys/socket.h>
#include <sys/ptrace.h>
#include <unistd.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <GL/gl.h>
#include <SDL2/SDL.h>
#include <errno.h>

/* Standard/POSIX. */
static FILE* (*old_fopen)(const char* pathname, const char* mode) = NULL;
ssize_t (*old_sendto)(int sockfd, const void* buf, size_t len, int flags, const struct sockaddr* dest_addr, socklen_t addrlen);
ssize_t (*old_recv)(int sockfd, void *buf, size_t len, int flags);
ssize_t (*old_send)(int sockfd, const void* buf, size_t len, int flags);
ssize_t (*old_recvfrom)(int sockfd, void *buf, size_t len, int flags, struct sockaddr* src_addr, socklen_t* addrlen);
int (*old_open)(const char *pathname, int flags);

/* OpenGL. */
void (*old_glShadeModel)(GLenum mode);
void (*old_glFogfv)(GLenum pname, const GLfloat* params);

/* SDL. */
int (*old_SDL_PollEvent)(SDL_Event* event);
void (*old_SDL_WM_SetCaption)(const char* title, const char* icon) = NULL;

/* Please ignore the variable names. */
void *addr_0, *addr_1, *addr_2;
int game_mode = 1;
int ex_game_mode = 1;
char level_dat_name[512];
int reading = 1;
int connected = 1;
char buffer[64];
int i = 0;
int api_fd = 0;

int api_setup();
int api_kill();

/* To be optimized. */
void* search(char* data, int from)
{
	void* i;

	i = (void*)from;
	while (i < (void*)0x20000)
	{
		if (memcmp(i, data, 4) == 0 && i != (void*)data)
		{
			return i;
		}
		i += 1;
	}
	return NULL;
}

void unprotect(uint32_t addr)
{
	mprotect((void*)(addr - (addr % 4096)), 4096, PROT_READ|PROT_WRITE|PROT_EXEC);
}

/* [Work In Progress] Dinamyclly change the game mode. */
FILE* fopen(const char* filename, const char* mode)
{
	if (strcmp(basename((char*)filename), "player.dat") == 0)
	{
		FILE* level_dat_file;
		char* andseq;

		level_dat_name[0] = 0;
		sprintf(level_dat_name, "%s/level.dat", dirname((char*)filename));
		level_dat_file = fopen(level_dat_name, "rb");
		fseek(level_dat_file, 0x16, SEEK_SET);
		fread(&game_mode, 1, 1, level_dat_file);

		if (ex_game_mode == 1)
		{
			andseq = "\x00\x2d\x10\x00";
		} else
		{
			andseq = "\x60\x2f\x10\x00";
		}

		/* To be optimized. */
		addr_0 = search(andseq, 0xde60);
		unprotect((uint32_t)(addr_0));
		addr_1 = search(andseq, (int)addr_0 + 4);
		unprotect((uint32_t)(addr_1));

		/* Don't replace this with loops or memory/string functions, it will not work. */
		if (game_mode == 0)
		{
			((char*)addr_0)[0] = '\x60';
			((char*)addr_0)[1] = '\x2f';
			((char*)addr_0)[2] = '\x10';
			((char*)addr_0)[3] = '\x00';
			((char*)addr_1)[0] = '\x60';
			((char*)addr_1)[1] = '\x2f';
			((char*)addr_1)[2] = '\x10';
			((char*)addr_1)[3] = '\x00';
		} else if (game_mode == 1)
		{
			((char*)addr_0)[0] = '\x00';
			((char*)addr_0)[1] = '\x2d';
			((char*)addr_0)[2] = '\x10';
			((char*)addr_0)[3] = '\x00';
			((char*)addr_1)[0] = '\x00';
			((char*)addr_1)[1] = '\x2d';
			((char*)addr_1)[2] = '\x10';
			((char*)addr_1)[3] = '\x00';
		}
		ex_game_mode = (int)game_mode;
		fclose(level_dat_file);
	} else if (strcmp(basename((char*)filename), "entities.dat") == 0 && strcmp(basename((char*)mode), "rb") == 0)
	{
		api_kill();
	}

	return old_fopen(filename, mode);
}

/* Fancy stuff: Change the window name. */
void SDL_WM_SetCaption(const char* title, const char* icon)
{
	return old_SDL_WM_SetCaption("Minecraft - Pi Edition - Patched", "/usr/share/pixmaps/minecraft-pi.png");
}

/* "Smooth" shading. */
void glShadeModel(GLenum mode)
{
	if (connected == 1)
	{
		api_kill();
		api_setup();
	}
	return old_glShadeModel(GL_SMOOTH);
}

/* Fancy stuff: Green fog. */
void glFogfv(GLenum pname, const GLfloat* params)
{
	GLfloat fog[] = {0.0, 1.0, 0.0, 1.0};
	GLfloat start = 0.0;

	if (pname == GL_FOG_COLOR)
	{
		return old_glFogfv(GL_FOG_COLOR, fog);
	} else if (pname == GL_FOG_START)
	{
		return old_glFogfv(GL_FOG_START, &start);
	} else
	{
		return old_glFogfv(pname, params);
	}
}

/* Extends port search: 19132-19139. */
ssize_t sendto(int sockfd, const void *buf, size_t len, int flags, const struct sockaddr* dest_addr, socklen_t addrlen)
{
	struct sockaddr_in* addr = (struct sockaddr_in*)dest_addr;
	int i = 19136;
	if (addr->sin_addr.s_addr == -1 && ntohs(addr->sin_port) == 19135)
	{
		while (i < 19139)
		{
			addr->sin_port = htons(i);
			if (old_sendto(sockfd, buf, len, flags, dest_addr, addrlen) < 0)
			{
				printf("sendto failed with exit errno %i\n", errno);
			}
			i++;
		}
		addr->sin_port = htons(19135);
	}
	return old_sendto(sockfd, buf, len, flags, dest_addr, addrlen);
}

/* Failed, thanks to the lack of debug symbols. Supposed to change the slot number to 2. */
int _ZN3Gui11getNumSlotsEv()
{
	return 2;
}

/* [Work In Progress] T-Chat. Stores the message in `buffer` and then prints it to `stdout`. */
int SDL_PollEvent(SDL_Event* event)
{
	int rt = old_SDL_PollEvent(event);

	/* MCPI uses custom events, and the Mojang folks decided that storing the keycode in the (optional) window ID was a good idea. */
	char chr = (char)event->user.windowID;

	if (event->type == 65538)
	{
		/* 
		 * 0x0d == CR/LF?
		 * 0x1b == Esc.
		 * 0x00 == Ignore, other "special" keys.
		 * 
		 */
		if (reading == 0 && chr != 0x00 && chr != 0x0d && chr != 0x1b && i < 64)
		{
			buffer[i] = chr;
			event->user.windowID = 0x00; /* Say "ignore" to MCPI. */
			i++;
		} else if (reading == 1 && chr == 't')
		{
			reading = 0;
			event->user.windowID = 0x00; /* Say "ignore" to MCPI. */
		} else if (reading == 0 && (chr == 0x0d || chr == 0x1b))
		{
			if (chr == 0x0d)
			{
				write(api_fd, "chat.post(", strlen("chat.post("));
				write(api_fd, buffer, strlen(buffer));
				write(api_fd, ")\n", strlen(")\n"));
			}
			event->user.windowID = 0x00; /* Say "ignore" to MCPI. */
			reading = 1;
			buffer[i] = 0x00;
			i = 0;
			memset(buffer, 0x00, 63); /* Clear the buffer. */
		}
	}
	return rt;
}

/* Setup API connection. */
int api_setup()
{
	int rt = 0;
	struct sockaddr_in api_addr;

	api_addr.sin_family = AF_INET;
	api_addr.sin_port = htons(4711);
	rt = inet_pton(AF_INET, "127.0.0.1", &api_addr.sin_addr);
	api_fd = socket(AF_INET, SOCK_STREAM, 0);

	if (api_fd < -1)
	{
		connected = 1;
		return -1;
	}
	rt = connect(api_fd, (struct sockaddr*)&api_addr, sizeof(api_addr));
	if (rt < 0)
	{
		connected = 1;
		return -1;
	}
	connected = 0;
	return 0;
}

/* Kill API connection. */
int api_kill()
{
	if (connected == 0)
	{
		shutdown(api_fd, SHUT_RDWR);
		close(api_fd);
		connected = 1;
	}
	return 0;
}

/* Constructor, gets called before MCPI itself. */
void __attribute__((constructor)) init()
{
	old_fopen = dlsym(RTLD_NEXT, "fopen");
	old_sendto = dlsym(RTLD_NEXT, "sendto");

	old_glShadeModel = dlsym(RTLD_NEXT, "glShadeModel");
	old_glFogfv = dlsym(RTLD_NEXT, "glFogfv");

	old_SDL_WM_SetCaption = dlsym(RTLD_NEXT, "SDL_WM_SetCaption");
	old_SDL_PollEvent = dlsym(RTLD_NEXT, "SDL_PollEvent");
	return;
}

/* Constructor, gets called when the library is unloaded from memory, and closes the API connection. */
void __attribute__((destructor)) destroy()
{
	api_kill();
	return;
}