heap-buffer-overflow at jsi_utf_tocase src/jsiString.c:396

[kvenux]

Build environment:

Ubuntu 16.04
gcc 5.4.0
version: 73f457f
build command:
export JSI__SANITIZE=1
make
test command: ./jsish poc

POC

jsish-1024-000124.txt

Description

Below is the ASAN outputs.

=================================================================
==2511==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60d00000ce56 at pc 0x0000004e8763 bp 0x7fff6dd3ff40 sp 0x7fff6dd3ff30
READ of size 1 at 0x60d00000ce56 thread T0
#0 0x4e8762 in jsi_utf_tocase src/jsiString.c:396
#1 0x4e951f in StringToLowerCaseCmd src/jsiString.c:432
#2 0x4c405d in jsi_FuncCallSub src/jsiProto.c:244
#3 0x73eaa4 in jsiFunctionSubCall src/jsiEval.c:790
#4 0x73eaa4 in jsiEvalFunction src/jsiEval.c:825
#5 0x73eaa4 in jsiEvalCodeSub src/jsiEval.c:1250
#6 0x7506ec in jsi_evalcode src/jsiEval.c:2190
#7 0x4c517a in jsi_FuncCallSub src/jsiProto.c:220
#8 0x73e7ca in jsiFunctionSubCall src/jsiEval.c:790
#9 0x73e7ca in jsiEvalFunction src/jsiEval.c:825
#10 0x73e7ca in jsiEvalCodeSub src/jsiEval.c:1250
#11 0x7506ec in jsi_evalcode src/jsiEval.c:2190
#12 0x4c517a in jsi_FuncCallSub src/jsiProto.c:220
#13 0x73e7ca in jsiFunctionSubCall src/jsiEval.c:790
#14 0x73e7ca in jsiEvalFunction src/jsiEval.c:825
#15 0x73e7ca in jsiEvalCodeSub src/jsiEval.c:1250
#16 0x7506ec in jsi_evalcode src/jsiEval.c:2190
#17 0x75317f in jsi_evalStrFile src/jsiEval.c:2496
#18 0x499c46 in Jsi_Main src/jsiInterp.c:917
#19 0xc0345a in jsi_main src/main.c:44
#20 0x7f78c529883f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2083f)
#21 0x434f48 in _start (/home/keven/Fuzzing/jsish-1024/jsish+0x434f48)

0x60d00000ce56 is located 0 bytes to the right of 134-byte region [0x60d00000cdd0,0x60d00000ce56)
allocated by thread T0 here:
#0 0x7f78c5e04602 in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x98602)
#1 0x49e422 in Jsi_Malloc src/jsiUtils.c:52

SUMMARY: AddressSanitizer: heap-buffer-overflow src/jsiString.c:396 jsi_utf_tocase
Shadow bytes around the buggy address:
0x0c1a7fff9970: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c1a7fff9980: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c1a7fff9990: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c1a7fff99a0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c1a7fff99b0: fa fa fa fa fa fa fa fa fa fa 00 00 00 00 00 00
=>0x0c1a7fff99c0: 00 00 00 00 00 00 00 00 00 00[06]fa fa fa fa fa
0x0c1a7fff99d0: fa fa fa fa 00 00 00 00 00 00 00 00 00 00 00 00
0x0c1a7fff99e0: 00 00 00 00 00 00 fa fa fa fa fa fa fa fa 00 00
0x0c1a7fff99f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 04 fa
0x0c1a7fff9a00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c1a7fff9a10: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
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
Heap right redzone: fb
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack partial redzone: f4
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
==2511==ABORTING

[pcmacdon]

The index was mistakenly a char, which wrapped at 128. Terrific find.