Files
ci-libretro-fceumm/src/fceu.c
U-DESKTOP-SPFP6AQ\twistedtechre 1185db89c1 core: memory-safety, leak, and savestate-portability audit fixes
Squashed series of ~50 distinct bugs found during a multi-day
security/correctness audit, ranging from ROM-triggerable heap
corruption and savestate-triggered OOB read primitives down to
obscure cross-platform savestate breakage.

Build is clean on `make platform=unix` with zero new warnings.

CRITICAL (ROM-triggerable, exploitable on the user's machine)
=============================================================

* ines.c iNES 2.0 PRG/CHR exponent overflow leading to undersized
  allocation followed by heap buffer overflow on fread (pow() with
  attacker-chosen exponent up to 63). Cap exponent at 30 and
  compute size in uint32 with explicit cap below 2 GiB before
  storing in int.
* ines.c miscROMSize int wraparound from attacker-controlled PRG/
  CHR sizes; previous '& 0x8000000' check missed common underflow
  cases. Compute in int64 and reject <= 0 or > 128 MiB.
* unif.c MAPR chunk OOB heap read on chunks of size < 4. Validate
  chunk size before allocating board-name buffer.
* unif.c chunk size truncation: int conversion + missing cap allowed
  a 4 GiB chunk size to wrap. Cap at 16 MiB.
* unif.c FixRomSize infinite loop on size > 0x80000000. Cap input.
* unif.c DINF chunk: months[(m - 1) % 12] is UB for m==0; m comes
  from the .unf file. Clamp m into [1..12] before subtracting.
* unif.c NAME chunk: GameInfo->name = malloc(...) was unchecked.
* nsf.c size underflow: FCEU_fgetsize() - 0x80 wraps to ~UINT64_MAX
  on tiny files, propagating a huge size into uppow2/FCEU_malloc.
  Validate size > 0x80 before subtracting.
* nsf.c NSFMaxBank * 4096 cap tightened from 1<<20 (UB on signed-int
  overflow) to 1<<19 (fits in int).
* general.c uppow2 had signed-int UB (1 << 32) and wrapped to 0 for
  inputs near uint32 max. Cap at 0x80000000.
* cheat.c SubCheats[256] BSS overflow when more than 256 GG/PAR
  substitution cheats are active. The array is adjacent to MMapPtrs[64]
  in BSS which is exposed via retro_get_memory_data, making this
  overflow visible from outside the core.
* libretro.c retro_cheat_set strcpy stack overflow with arbitrary-
  length cheat strings from the frontend. Use strlcpy.

CRITICAL (savestate-triggerable on a malicious .fcs file)
=========================================================

* fds.c FDS savestate OOB read primitive: InDisk loaded from
  savestate is used as index into 8-element diskdata[] static
  pointer array. A value 8..254 dereferences arbitrary memory as
  a pointer (heap-read primitive). Also bounds-checked SelectDisk,
  mapperFDS_block, mapperFDS_blockstart, mapperFDS_diskaddr,
  mapperFDS_blocklen so blockstart+diskaddr stays within the 65500-
  byte disk buffer.
* 11 mappers had savestate-loaded variables masked at write time
  but not at restore time, used as indices into fixed arrays:
    - 88.c, KS7037.c, 112.c   cmd indexes reg[8]
    - sachen.c (S8259, S74LS374N) cmd indexes latch[8]
    - 357.c    dipswitch indexes outer_bank[4]
    - unrom512.c flash_state indexes erase_a/d/b[5]
    - 368.c    preg indexes banks[8]
    - 69.c     sndcmd indexes sreg[14]
    - mmc2and4.c latch0/latch1 index creg[4]
  None individually exploitable into RCE - the array writes corrupt
  adjacent BSS with constrained data flowing in - but each is an
  out-of-bounds read or write from attacker-controllable input.

HIGH (memory-safety, reachable on any load)
===========================================

* fceu-memory.c FCEU_malloc deref-of-NULL on allocation failure
  ('ret = 0; memset(ret, 0, size);').
* file.c multiple FCEUFILE/MakeMemWrap/MakeMemWrapBuffer unchecked
  allocations and unchecked filestream_tell return.
* libretro.c GameInfo NULL-derefs in three entry points
  (retro_set_controller_port_device, retro_get_memory_data,
  retro_get_memory_size) reachable on operations called before a
  successful load.
* libretro.c framebuffer leak ~256 KB per failed FCEUI_LoadGame
  (the libretro frontend doesn't call retro_unload_game on a
  failed load).
* libretro.c 3DS retro_deinit unchecked linearFree.
* libretro.c stereo / NTSC filter unchecked malloc returns.
* fceu.c FCEUI_LoadGame unchecked GameInfo malloc.
* fds.c SubLoad and FDSLoad unchecked FCEU_malloc on diskdatao
  backup buffers (NULL-deref in subsequent memcpy).
* fceu.c AllocGenieRW partial-failure leak: AReadG allocated but
  BWriteG malloc fails -> 256 KB leak per retry.
* input/bworld.c Update(): unbounded strcpy from attacker-supplied
  data into 20-byte bdata. Replaced with length-bounded copy.
* cart.c setprg2r/4r and setchr1r/2r/4r/8r mask-underflow guards.
  SetupCartPRGMapping/SetupCartCHRMapping compute (size >> N) - 1
  which underflows to 0xFFFFFFFF for chips smaller than the unit.
  setprg8r/16r/32r and setchr8r already had defensive size checks;
  the smaller units did not. malee.c (2 KB chip) and mapper 218
  (2 KB NTARAM-as-CHR) accidentally avoid OOB; the primitive is
  unsafe for any future board.
* video.c FCEU_InitVirtualVideo XBuf/XDBuf partial-failure leak.
* video.c, fceu.c FCEU_DispMessage / FCEU_printf / FCEU_PrintError:
  vsprintf into fixed stack buffers replaced with vsnprintf.
* core: validate magic-string read length on FDS/UNIF/NSF load
  (reject files too short to contain the magic so previous static
  buffer / stack garbage doesn't spuriously match).

LEAKS (every cart load/unload cycle)
====================================

* mmc5.c MMC5 cart-side: WRAM (up to 64K) + MMC5fill (1K) + ExRAM
  (1K) leaked per cycle. NSFMMC5_Close existed but was only used
  for NSF code path.
* onebus.c Mapper 270/436: 8 KB CHRRAM leaked per cycle.
* 330.c, 375.c, 528.c: 8 KB WRAM each, no Close at all.

CORRECTNESS (UB / ABI / endianness)
===================================

* fceu-endian.c FlipByteOrder loop bound was 'count' instead of
  'count/2', making it a no-op for every even count and silently
  breaking savestate portability for every FCEUSTATE_RLSB-marked
  field. The '#ifndef GEKKO' workarounds scattered through the
  codebase (sound.c, vrc7.c, vrc6.c) were symptoms of this root
  cause.
* state.c AddExState bounds check ran AFTER writing the entry, so
  when SFEXINDEX hit the 63-entry cap the next call would write
  the entry then immediately overwrite it with the terminator.
* state.c FCEUSS_Save_Mem: post-save callback was guarded by
  'if (SPreSave)' instead of 'if (SPostSave)'.
* Sequence-point UB in counter expressions across 4 board files,
  e.g. 'x = !x ? a : --x' and 'x = ++x % n'. GCC -Wsequence-point
  flags all five sites (285.c, 413.c, asic_mmc3.c, jyasic.c).
* SFORMAT size mismatches between declared variable type and
  AddExState size argument:
    - asic_vrc3.c VRC3_count/VRC3_reload (uint16, saved as 1 byte)
    - mmc3.c m555_count (uint32, saved as 2 bytes), m555_count_-
      expired (uint8, saved as 2 bytes - OOB write into adjacent
      BSS).
* unrom512.c UNROM-512 mapper 30 .srm save format: host-endian
  uint32 flash write counters. Now stored as LE on disk regardless
  of host (Battle Kid 2, Twin Dragons, Lizard, Sole, etc.).
* ~70 multi-byte single-variable SFORMAT/AddExState entries across
  36 board files were saved as host-byte-order. After the
  FlipByteOrder fix, these are now byte-swapped on BE so cross-
  platform savestates round-trip correctly.
* coolgirl.c new ExStateLE() macro added; 22 multi-byte sites.
* pic16c5x.c 11 multi-byte AddExState calls (m_PC, m_PREVPC,
  m_CONFIG, m_WDT, m_prescaler, m_opcode, m_STACK[0/1], m_icount,
  m_delay_timer, m_rtcc, m_inst_cycles, m_clock2cycle).
* onebus.c PowerJoy Supermax submapper detection used non-portable
  *(uint32*)&info->MD5 cast that read different bytes on LE vs BE.
* fds.c clean up redundant FCEUSTATE_RLSB encoding in AddExState
  calls that also passed type=1 (idempotent OR; readability fix).

DOCUMENTATION
=============

* input.c UpdateGP's *(uint32*)data cast looks like a typical
  endian bug but is actually correct (the libretro frontend builds
  JSReturn with matching host-uint32 shifts). Comment added to
  prevent future "fixes" from breaking it.

Limitations not addressed
=========================

* Element-stride-aware byte swapping. The savestate byte-swap
  mechanism (FlipByteOrder over the entire SFORMAT entry buffer)
  is structurally wrong for arrays of multi-byte values: it
  reverses the whole buffer end-to-end instead of byte-swapping
  each element. Several places that need cross-platform-portable
  arrays (VRC7 sound state, jyasic chr[8]) work around this by
  either splitting arrays into per-element SFORMAT entries (n106
  PlayIndex, bandai reg) or by skipping save entirely on BE via
  #ifndef GEKKO. A proper fix would extend the size encoding with
  an element-stride field. Left for a future change because it
  would change the savestate format.

* Strict-aliasing UB in ppu.c (around 9 sites doing
  *(uint32*)uint8_buf for fast 4-byte writes via FCEU_dwmemset).
  Works in practice with all common compilers because the patterns
  are byte-symmetric, but is formally UB.

* FCEU_gmalloc calls exit(1) on OOM. A libretro core should never
  exit() because that takes down the whole frontend. Used by
  100+ call sites; refactoring to return-NULL is out of scope here.

Testing
=======

* Build: clean on `make platform=unix` with -O2; no new warnings.
* FlipByteOrder fix verified by hand-trace and a standalone unit
  test for counts 2, 4, 8.
* uppow2 fix verified by unit test across 13 boundary cases.
* SFORMAT size mismatches and missing-RLSB cases identified by
  Python static-analysis scripts that cross-reference SFORMAT
  entries against variable declarations.
* iNES 2.0 exponent fix verified by hand-tracing what byte 0xFF
  produces post-fix: exp=30 (capped), mult=7, size=3 GiB nominal,
  capped to 1 GiB, capped to 2 GiB by uppow2, FCEU_malloc returns
  NULL on most systems, loader returns 0. No heap overflow for
  any input byte.
* Savestate-loaded array index audit: built a Python scanner that
  extracts each AddExState/SFORMAT entry and cross-references the
  variable name against array-index uses in the same file. All
  flagged sites covered.
* A libFuzzer harness and seed corpus generator (fuzz_main.c,
  gen_seed_corpus.py) accompany this submission for ongoing
  regression testing.
2026-05-04 02:15:40 +02:00

546 lines
10 KiB
C

/* FCE Ultra - NES/Famicom Emulator
*
* Copyright notice for this file:
* Copyright (C) 2003 Xodnizel
*
* 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; either version 2 of the License, or
* (at your option) any later version.
*
* 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
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdarg.h>
#include "fceu.h"
#include "fceu-types.h"
#include "x6502.h"
#include "fceu.h"
#include "ppu.h"
#include "sound.h"
#include "general.h"
#include "fceu-endian.h"
#include "fceu-memory.h"
#include "cart.h"
#include "nsf.h"
#include "fds.h"
#include "ines.h"
#include "unif.h"
#include "cheat.h"
#include "palette.h"
#include "state.h"
#include "video.h"
#include "input.h"
#include "file.h"
#include "crc32.h"
#include "vsuni.h"
uint64 timestampbase;
FCEUGI *GameInfo = NULL;
void (*GameInterface)(int h);
void (*GameStateRestore)(int version);
readfunc ARead[0x10000];
writefunc BWrite[0x10000];
static readfunc *AReadG = NULL;
static writefunc *BWriteG = NULL;
static int RWWrap = 0;
static DECLFW(BNull)
{
}
static DECLFR(ANull)
{
return(X.DB);
}
int AllocGenieRW(void)
{
if (!AReadG)
{
if (!(AReadG = (readfunc*)FCEU_malloc(0x8000 * sizeof(readfunc))))
return 0;
}
else
memset(AReadG, 0, 0x8000 * sizeof(readfunc));
if (!BWriteG)
{
if (!(BWriteG = (writefunc*)FCEU_malloc(0x8000 * sizeof(writefunc))))
{
/* Free AReadG too on partial-failure to avoid leaking a
* 256 KB read-handler table. Subsequent calls would otherwise
* see AReadG != NULL and skip its alloc, but RWWrap stays 0
* because we return 0, so the table is never used or freed. */
free(AReadG);
AReadG = NULL;
return 0;
}
}
else
memset(BWriteG, 0, 0x8000 * sizeof(writefunc));
RWWrap = 1;
return 1;
}
void FlushGenieRW(void)
{
int32 x;
if (RWWrap)
{
for (x = 0; x < 0x8000; x++)
{
ARead[x + 0x8000] = AReadG[x];
BWrite[x + 0x8000] = BWriteG[x];
}
free(AReadG);
free(BWriteG);
AReadG = NULL;
BWriteG = NULL;
}
RWWrap = 0;
}
readfunc FASTAPASS(1) GetReadHandler(int32 a)
{
if (a >= 0x8000 && RWWrap)
return AReadG[a - 0x8000];
else
return ARead[a];
}
void FASTAPASS(3) SetReadHandler(int32 start, int32 end, readfunc func)
{
int32 x;
if (!func)
func = ANull;
if (RWWrap)
for (x = end; x >= start; x--)
{
if (x >= 0x8000)
AReadG[x - 0x8000] = func;
else
ARead[x] = func;
}
else
for (x = end; x >= start; x--)
ARead[x] = func;
}
writefunc FASTAPASS(1) GetWriteHandler(int32 a)
{
if (RWWrap && a >= 0x8000)
return BWriteG[a - 0x8000];
else
return BWrite[a];
}
void FASTAPASS(3) SetWriteHandler(int32 start, int32 end, writefunc func)
{
int32 x;
if (!func)
func = BNull;
if (RWWrap)
for (x = end; x >= start; x--)
{
if (x >= 0x8000)
BWriteG[x - 0x8000] = func;
else
BWrite[x] = func;
}
else
for (x = end; x >= start; x--)
BWrite[x] = func;
}
uint8 RAM[0x800];
uint8 PAL = 0;
static DECLFW(BRAML)
{
RAM[A] = V;
}
static DECLFR(ARAML)
{
return RAM[A];
}
static DECLFW(BRAMH)
{
RAM[A & 0x7FF] = V;
}
static DECLFR(ARAMH)
{
return RAM[A & 0x7FF];
}
void FCEUI_CloseGame(void)
{
if (!GameInfo)
return;
if (GameInfo->name)
free(GameInfo->name);
GameInfo->name = 0;
if (GameInfo->type != GIT_NSF)
FCEU_FlushGameCheats();
GameInterface(GI_CLOSE);
ResetExState(0, 0);
FCEU_CloseGenie();
free(GameInfo);
GameInfo = 0;
}
void ResetGameLoaded(void)
{
if (GameInfo)
FCEUI_CloseGame();
GameStateRestore = NULL;
PPU_hook = NULL;
GameHBIRQHook = NULL;
if (GameExpSound.Kill)
GameExpSound.Kill();
memset(&GameExpSound, 0, sizeof(GameExpSound));
MapIRQHook = NULL;
MMC5Hack = 0;
PEC586Hack = 0;
PAL &= 1;
default_palette_selected = 0;
}
int UNIFLoad(const char *name, FCEUFILE *fp);
int iNESLoad(const char *name, FCEUFILE *fp);
int FDSLoad(const char *name, FCEUFILE *fp);
int NSFLoad(FCEUFILE *fp);
FCEUGI *FCEUI_LoadGame(const char *name, const uint8_t *databuf, size_t databufsize,
frontend_post_load_init_cb_t frontend_post_load_init_cb)
{
FCEUFILE *fp;
ResetGameLoaded();
GameInfo = malloc(sizeof(FCEUGI));
if (!GameInfo)
return NULL;
memset(GameInfo, 0, sizeof(FCEUGI));
GameInfo->soundchan = 0;
GameInfo->soundrate = 0;
GameInfo->name = 0;
GameInfo->type = GIT_CART;
GameInfo->vidsys = GIV_USER;
GameInfo->input[0] = GameInfo->input[1] = -1;
GameInfo->inputfc = -1;
GameInfo->cspecial = 0;
fp = FCEU_fopen(name, databuf, databufsize);
if (!fp) {
FCEU_PrintError("Error opening \"%s\"!", name);
free(GameInfo);
GameInfo = NULL;
return NULL;
}
if (iNESLoad(name, fp))
goto endlseq;
if (NSFLoad(fp))
goto endlseq;
if (UNIFLoad(NULL, fp))
goto endlseq;
if (FDSLoad(NULL, fp))
goto endlseq;
FCEU_PrintError("An error occurred while loading the file.\n");
FCEU_fclose(fp);
if (GameInfo->name)
free(GameInfo->name);
GameInfo->name = NULL;
free(GameInfo);
GameInfo = NULL;
return NULL;
endlseq:
FCEU_fclose(fp);
if (frontend_post_load_init_cb)
(*frontend_post_load_init_cb)();
FCEU_ResetVidSys();
if (GameInfo->type != GIT_NSF)
if (FSettings.GameGenie)
FCEU_OpenGenie();
PowerNES();
if (GameInfo->type != GIT_NSF) {
FCEU_LoadGamePalette();
FCEU_LoadGameCheats();
}
FCEU_ResetPalette();
return(GameInfo);
}
int FCEUI_Initialize(void) {
if (!FCEU_InitVirtualVideo())
return 0;
memset(&FSettings, 0, sizeof(FSettings));
FSettings.UsrFirstSLine[0] = 8;
FSettings.UsrFirstSLine[1] = 0;
FSettings.UsrLastSLine[0] = 231;
FSettings.UsrLastSLine[1] = 239;
FSettings.SoundVolume = 100;
FCEUPPU_Init();
X6502_Init();
return 1;
}
void FCEUI_Kill(void) {
FCEU_KillVirtualVideo();
FCEU_KillGenie();
}
void FCEUI_Emulate(uint8 **pXBuf, int32 **SoundBuf, int32 *SoundBufSize, int skip) {
int r, ssize;
FCEU_UpdateInput();
if (geniestage != 1) FCEU_ApplyPeriodicCheats();
r = FCEUPPU_Loop(skip);
ssize = FlushEmulateSound();
timestampbase += timestamp;
timestamp = 0;
sound_timestamp = 0;
*pXBuf = skip ? 0 : XBuf;
*SoundBuf = WaveFinal;
*SoundBufSize = ssize;
}
void ResetNES(void)
{
if (!GameInfo)
return;
GameInterface(GI_RESETM2);
FCEUSND_Reset();
FCEUPPU_Reset();
X6502_Reset();
}
int option_ramstate = 0;
void FCEU_MemoryRand(uint8 *ptr, uint32 size)
{
int x = 0;
while (size) {
#if 0
*ptr = (x & 4) ? 0xFF : 0x00; /* Huang Di DEBUG MODE enabled by default */
/* Cybernoid NO MUSIC by default */
*ptr = (x & 4) ? 0x7F : 0x00; /* Huang Di DEBUG MODE enabled by default */
/* Minna no Taabou no Nakayoshi Daisakusen DOESN'T BOOT */
/* Cybernoid NO MUSIC by default */
*ptr = (x & 1) ? 0x55 : 0xAA; /* F-15 Sity War HISCORE is screwed... */
/* 1942 SCORE/HISCORE is screwed... */
#endif
uint8_t v = 0;
switch (option_ramstate)
{
case 0: v = 0xff; break;
case 1: v = 0x00; break;
case 2: v = (uint8_t)rand(); break;
}
*ptr = v;
x++;
size--;
ptr++;
}
}
void hand(X6502 *X, int type, uint32 A)
{
}
void PowerNES(void)
{
if (!GameInfo)
return;
encryptOpcodes =0;
FCEU_CheatResetRAM();
FCEU_CheatAddRAM(2, 0, RAM);
FCEU_GeniePower();
FCEU_MemoryRand(RAM, 0x800);
SetReadHandler(0x0000, 0xFFFF, ANull);
SetWriteHandler(0x0000, 0xFFFF, BNull);
SetReadHandler(0, 0x7FF, ARAML);
SetWriteHandler(0, 0x7FF, BRAML);
SetReadHandler(0x800, 0x1FFF, ARAMH); /* Part of a little */
SetWriteHandler(0x800, 0x1FFF, BRAMH); /* hack for a small speed boost. */
InitializeInput();
FCEUSND_Power();
FCEUPPU_Power();
/* Have the external game hardware "powered" after the internal NES stuff.
Needed for the NSF code and VS System code.
*/
GameInterface(GI_POWER);
if (GameInfo->type == GIT_VSUNI)
FCEU_VSUniPower();
timestampbase = 0;
X6502_Power();
FCEU_PowerCheats();
}
void FCEU_ResetVidSys(void)
{
int w;
if (GameInfo->vidsys == GIV_NTSC)
w = 0;
else if (GameInfo->vidsys == GIV_PAL)
{
w = 1;
dendy = 0;
}
else
w = FSettings.PAL;
PAL = w ? 1 : 0;
if (PAL)
dendy = 0;
normal_scanlines = dendy ? 290 : 240;
totalscanlines = normal_scanlines + (overclock_enabled ? extrascanlines : 0);
FCEUPPU_SetVideoSystem(w || dendy);
SetSoundVariables();
}
FCEUS FSettings;
void FCEU_printf(char *format, ...)
{
char temp[2048];
va_list ap;
va_start(ap, format);
/* vsnprintf instead of vsprintf so a long expansion (e.g. of a ROM
* filename or an attacker-controlled string field) is truncated
* rather than overflowing the stack buffer. */
vsnprintf(temp, sizeof(temp), format, ap);
FCEUD_Message(temp);
va_end(ap);
}
void FCEU_PrintError(char *format, ...)
{
char temp[2048];
va_list ap;
va_start(ap, format);
vsnprintf(temp, sizeof(temp), format, ap);
FCEUD_PrintError(temp);
va_end(ap);
}
void FCEUI_SetRenderedLines(int ntscf, int ntscl, int palf, int pall)
{
FSettings.UsrFirstSLine[0] = ntscf;
FSettings.UsrLastSLine[0] = ntscl;
FSettings.UsrFirstSLine[1] = palf;
FSettings.UsrLastSLine[1] = pall;
if (PAL || dendy)
{
FSettings.FirstSLine = FSettings.UsrFirstSLine[1];
FSettings.LastSLine = FSettings.UsrLastSLine[1];
}
else
{
FSettings.FirstSLine = FSettings.UsrFirstSLine[0];
FSettings.LastSLine = FSettings.UsrLastSLine[0];
}
}
void FCEUI_SetVidSystem(int a)
{
FSettings.PAL = a ? 1 : 0;
if (!GameInfo)
return;
FCEU_ResetVidSys();
FCEU_ResetPalette();
}
int FCEUI_GetCurrentVidSystem(int *slstart, int *slend)
{
if (slstart)
*slstart = FSettings.FirstSLine;
if (slend)
*slend = FSettings.LastSLine;
return(PAL);
}
void FCEUI_SetGameGenie(int a)
{
FSettings.GameGenie = a ? 1 : 0;
}
int32 FCEUI_GetDesiredFPS(void)
{
if (PAL || dendy)
return(838977920); /* ~50.007 */
else
return(1008307711); /* ~60.1 */
}