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subl.c
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subl.c
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <fcntl.h>
//#include <linux/seccomp.h>
#define SECCOMP_MODE_FILTER 2
#include <sys/mman.h>
#include <sys/prctl.h>
#include <sys/resource.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/types.h>
#include <time.h>
#include <unistd.h>
#define eprintf(format, ...) \
fprintf(stderr, "\x1b[3%dm[%s:%d(%s)]\x1b[m" format, \
__LINE__ % 6 + 1, __FILE__, __LINE__, \
__PRETTY_FUNCTION__, ##__VA_ARGS__)
typedef long long ll;
typedef unsigned long long ull;
// seccomp-tools
// https://github.com/david942j/seccomp-tools
static const unsigned char filter[] = { 32, 0, 0, 0, 4, 0, 0, 0, 21, 0, 0, 13, 62, 0, 0, 192, 32, 0, 0, 0, 0, 0, 0, 0, 53, 0, 11, 0, 0, 0, 0, 64, 21, 0, 9, 0, 0, 0, 0, 0, 21, 0, 8, 0, 1, 0, 0, 0, 21, 0, 7, 0, 19, 0, 0, 0, 21, 0, 6, 0, 20, 0, 0, 0, 21, 0, 5, 0, 96, 0, 0, 0, 21, 0, 4, 0, 228, 0, 0, 0, 21, 0, 3, 0, 60, 0, 0, 0, 21, 0, 2, 0, 231, 0, 0, 0, 21, 0, 1, 0, 35, 0, 0, 0, 6, 0, 0, 0, 38, 0, 5, 0, 6, 0, 0, 0, 0, 0, 255, 127, 6, 0, 0, 0, 0, 0, 0, 0 };
#define EXIT_ON_FAIL_HINT(EXPR, HINT) \
if (EXPR) { \
perror(HINT); \
eprintf(#EXPR " returned with nonzero status\n"); \
exit(-1); \
}
#define WARN_ON_FAIL_HINT(EXPR, HINT) \
if (EXPR) { \
perror(HINT); \
eprintf(#EXPR " returned with nonzero status\n"); \
}
#define EXIT_ON_FAIL(EXPR) EXIT_ON_FAIL_HINT(EXPR, #EXPR)
#define WARN_ON_FAIL(EXPR) WARN_ON_FAIL_HINT(EXPR, #EXPR)
#define FLAG_ADDR ((void*)0x555000)
typedef enum { false,
true } bool;
typedef uint32_t WD;
//extern WD binary[0x4000];
static WD* emu_mem;
static const char* rom;
static void* rom_content;
static int romsz;
static const char* flag; // both filename and flag content
static int rand_fd;
static char random_buffer[0x1000];
static int used;
static void get_random(void* dest, ssize_t size)
{
// hand written random reading
int cur_used = used & 0xfff;
if (size > 0x1000 - used) {
if (cur_used) {
read(rand_fd, random_buffer, cur_used);
cur_used = 0;
}
read(rand_fd, dest, size);
} else {
memcpy(dest, random_buffer + used, size);
cur_used += size;
if (cur_used == 0x1000) {
read(rand_fd, random_buffer, 0x1000);
cur_used = 0;
}
}
used = cur_used;
}
static void init_random_fd(void)
{
// random buffer
rand_fd = open("/dev/urandom", O_RDONLY);
EXIT_ON_FAIL(rand_fd < 0);
read(rand_fd, random_buffer, 4096);
}
static void init_flag(void)
{
// flag
void* flag_addr = NULL;
if (flag) {
int flag_fd = open(flag, O_RDONLY);
EXIT_ON_FAIL(flag_fd < 0);
flag_addr = mmap(FLAG_ADDR, 0x1000, PROT_READ, MAP_PRIVATE, flag_fd, 0);
EXIT_ON_FAIL(flag_addr == MAP_FAILED);
close(flag_fd);
} else {
flag_addr = "";
}
flag = (const char*)flag_addr;
}
static off_t getsz(int fd)
{
struct stat st;
EXIT_ON_FAIL(fstat(fd, &st) < 0);
return st.st_size;
}
static void init_rom(void)
{
// rom
int rom_fd = open(rom, O_RDONLY);
EXIT_ON_FAIL(rom_fd < 0);
// we assume no one race us here ...
// we also assume that rom sz is smaller than some arbitrary limit
int rom_fsz = getsz(rom_fd) & 0xffffff;
if (rom_fsz & 0xfff) {
rom_fsz = (rom_fsz & -0x1000) + 0x1000;
}
// we can allocate at most 0x100000 for code+data, sadly
EXIT_ON_FAIL(rom_fsz > 0x100000);
void* rom_addr = mmap(NULL, rom_fsz, PROT_READ, MAP_PRIVATE, rom_fd, 0);
EXIT_ON_FAIL(rom_addr == MAP_FAILED);
close(rom_fd);
rom_content = rom_addr;
romsz = rom_fsz;
rom = NULL;
}
static void init_vmmem(void)
{
// map vm memory before prctl
void* vm_mem = mmap(NULL, 0x400000, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
EXIT_ON_FAIL(vm_mem == MAP_FAILED);
emu_mem = (WD*)vm_mem;
}
static void init_fds(void)
{
init_random_fd();
init_flag();
init_rom();
init_vmmem();
}
static void init_env(void)
{
// normal prctl protection
EXIT_ON_FAIL(prctl(PR_SET_DUMPABLE, 0) < 0);
EXIT_ON_FAIL(prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) < 0);
alarm(90);
struct rlimit rlim;
// don't check error, since there may be certain limit set up
rlim.rlim_cur = rlim.rlim_max = 0;
setrlimit(RLIMIT_CORE, &rlim);
// cputime limit
rlim.rlim_cur = rlim.rlim_max = 1;
setrlimit(RLIMIT_CPU, &rlim);
// vm limit, 16M is more than reasonable (?)
rlim.rlim_cur = rlim.rlim_max = 0x1000000;
setrlimit(RLIMIT_AS, &rlim);
// forkbomb guard
//rlim.rlim_cur = rlim.rlim_max = 256;
//setrlimit(RLIMIT_NPROC, &rlim);
init_fds();
struct prog {
unsigned short len;
const unsigned char* filter;
} rule = {
.len = sizeof(filter) >> 3,
.filter = filter
};
EXIT_ON_FAIL(prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &rule) < 0);
}
static const WD inv_list[32] = { 1,
2863311531,
3435973837,
3067833783,
954437177,
3123612579,
3303820997,
4008636143,
4042322161,
678152731,
1022611261,
3921491879,
3264175145,
1749801491,
1332920885,
3186588639,
1041204193,
2331553675,
2437684141,
2532929431,
3247414297,
799063683,
2767867813,
1736263375,
438261969,
4210752251,
2350076445,
1483715975,
3089362441,
2693454067,
3238827797,
3204181951 };
static WD rand_integer(void)
{
WD ret;
get_random(&ret, sizeof(ret));
return ret;
}
// subl devices
static void sl_halt(WD code)
{
fprintf(stderr, "Program exited with status %u\n", code);
exit(code);
}
static WD sl_randint(void)
{
return rand_integer();
}
static WD sl_gettime(void)
{
struct timeval tv = {};
int ret = gettimeofday(&tv, NULL);
return tv.tv_sec * 1000 + tv.tv_usec / 1000;
}
static void sl_sleep(WD time)
{
fflush(stdout);
usleep((long)time * 1000);
}
static void sl_putchar(WD c)
{
putchar(c);
}
static WD sl_getchar(void)
{
fflush(stdout);
static int bad_get = 0;
int c = getchar();
if (c == EOF) {
if (!bad_get) {
bad_get = 1 + (rand_integer() & 0xf0);
}
bad_get++;
if (bad_get > 256) {
puts("Broken Pipe");
exit(-32);
}
}
return c;
}
struct control_block {
WD* memory;
union {
WD flag[20];
char flag_text[80];
};
WD flag_key;
WD pc;
WD cycle;
WD jcycle;
WD memstat;
};
static void init_cb(struct control_block* cb)
{
cb->memory = emu_mem; // since we only have one buffer
int flag_len = strlen(flag);
if (flag_len > sizeof(cb->flag_text) - 1)
flag_len = sizeof(cb->flag_text) - 1;
memcpy(cb->flag_text, flag, flag_len);
if (flag_len < sizeof(cb->flag_text) - 1) {
get_random(cb->flag_text + flag_len + 1, sizeof(cb->flag_text) - flag_len - 1);
}
cb->flag_key = 0;
cb->cycle = 0;
cb->jcycle = 0;
// text section
WD aslr = rand_integer() & 0xff;
WD code_base = cb->pc = 0x200000 | (aslr << 12);
//memcpy(cb->memory + (cb->pc >> 2), binary, sizeof(binary));
memcpy(cb->memory + (code_base >> 2), rom_content, romsz);
}
// address mask
static const WD AMSK = (1 << 22) - 1;
// util function for handling subword reads / writes
static WD get_subword(WD word, WD addr, int n)
{
addr = addr & 3 & (-n);
return (word >> (8 * addr)) & ((1l << (8 * n)) - 1);
}
static WD write_subword(WD new_val, WD old_word, WD addr, int n)
{
addr = addr & 3 & (-n);
WD mask = ((1l << (8 * n)) - 1) << (8 * addr);
return (old_word & ~mask) | ((new_val << (8 * addr)) & mask);
}
// read dma mem (<128bytes)
static WD read_dma(const struct control_block* cb, WD address, bool forced)
{
WD code = (address >> 2);
if (code >= 32) {
return 0;
}
if (code >= 12) {
return cb->flag[code - 12] ^ (cb->flag_key * (code * 2 + 1));
}
switch (address >> 2) {
//case 0:
// return 0;
case 1:
return cb->pc;
case 4:
return cb->cycle;
case 5:
return forced && !(address & 3) ? sl_getchar() : 0;
case 6:
return sl_randint();
case 7:
return sl_gettime();
case 8:
return cb->jcycle;
case 9:
return cb->memstat;
default:
return 0;
}
}
// write dma mem (<128bytes)
static void write_dma(struct control_block* cb, WD address, int n, WD value)
{
WD code = (address >> 2);
if (code >= 32) {
return;
}
if (code >= 12) {
WD orig = cb->flag[code - 12];
WD read = orig ^ (cb->flag_key * (code * 2 + 1));
WD v = write_subword(value, read, address, n) ^ orig;
cb->flag_key = v * inv_list[code];
} else if (address == 5 * 4) {
sl_putchar(value & 0xff);
} else if (address == 10 * 4) {
sl_sleep(value);
} else if (address == 11 * 4) {
sl_halt(value);
}
}
// read abs mem, input must be absolute
static WD read_abs(const struct control_block* cb, WD address, int n, bool forced)
{
address &= AMSK;
WD res = 0;
if (address < 128) {
res = read_dma(cb, address, forced);
} else {
WD off = (address >> 2) & ((1 << 20) - 1);
res = cb->memory[off];
}
return get_subword(res, address, n);
}
// write abs mem, input must be absolute
static void write_abs(struct control_block* cb, WD address, int n, WD value)
{
address &= AMSK;
if (address < 128) {
write_dma(cb, address, n, value);
} else {
// no TLB, we let OS to decide whether the page should be mapped
WD off = (address >> 2) & ((1 << 20) - 1);
cb->memory[off] = write_subword(value, cb->memory[off], address, n);
}
}
// address translation, base+offset -> absolute address
static WD addr_translate(const struct control_block* cb, WD address)
{
WD addr_type = (address >> 22) & ((1 << 6) - 1);
WD base_addr = read_abs(cb, addr_type << 2, 4, false);
return (base_addr + address) & AMSK;
}
// single step of vm
static void step(struct control_block* cb)
{
WD pc = cb->pc;
WD op_a = read_abs(cb, pc & AMSK, 4, false);
WD op_b = read_abs(cb, (pc + 4) & AMSK, 4, false);
WD o_op_c = read_abs(cb, (pc + 8) & AMSK, 4, false);
WD new_pc = cb->pc = (pc + 12) & AMSK;
int n = 0xf & (0x1244 >> ((o_op_c & 3) * 4));
WD op_c = o_op_c & -4;
WD ph_a = addr_translate(cb, op_a);
WD ph_b = addr_translate(cb, op_b);
WD ph_c = addr_translate(cb, op_c);
WD A = read_abs(cb, ph_a, n, false);
WD B = read_abs(cb, ph_b, n, true);
write_abs(cb, ph_a, n, (A - B) & ((1l << (8 * n)) - 1));
cb->cycle += 1;
if (ph_c != new_pc && A < B) {
cb->pc = ph_c;
cb->jcycle += 1;
}
// on_step(cb, pc, op_a, op_b, op_c, n, ph_a, ph_b, ph_c, A, B, cb->pc);
}
static void run_forever(struct control_block* cb)
{
int time_limit = 0x100000 + (rand_integer() & 0xfffff);
for (int i = 0; i < time_limit; i++) {
step(cb);
}
puts("Time Limit Exceeded");
exit(-3);
}
static void do_emu(void)
{
struct control_block cb = {};
init_cb(&cb);
run_forever(&cb);
}
int main(int argc, char* argv[])
{
if (argc < 2) {
fprintf(stderr, "Usage:\n\t%s rom.bin [flag]\n", argv[0]);
return -1;
}
rom = argv[1];
flag = argc > 2 ? argv[2] : NULL;
init_env();
do_emu();
return 0;
}