Segmentation fault from Object.h

[sihyungyou]

Hi, I found that pdf2json (commit b671b64) crashes with the attached file (pdf2json_crash.pdf) which has syntax errors. The crash was observed on Ubuntu 18.04.3 with kernel 4.15.0-72-generic and x86_64. The crash can be reproduced by the following command:

$ pdf2json pdf2json_crash.pdf

Here’s the the crash stack trace taken with GDB:

#0  0x00007ffff6e6930e in _int_malloc (av=av@entry=0x7ffff71c0c40 <main_arena>, bytes=bytes@entry=4) at malloc.c:3557
#1  0x00007ffff6e6c0fc in __GI___libc_malloc (bytes=4) at malloc.c:3057
#2  0x0000555555849e67 in gmalloc (size=4) at gmem.cc:97
#3  0x000055555584b009 in copyString (s=0x555556d6e0d4 "obj") at gmem.cc:261
#4  0x000055555582751d in Lexer::getObj (this=0x555556d6e0b0, obj=0x555556d6e088) at ./Object.h:103
#5  0x000055555582d8f7 in Parser::shift (this=0x555556d6e060) at Parser.cc:226
#6  0x000055555582bfa2 in Parser::getObj (this=0x555556d6e060, obj=0x7fffff7ff2a8, fileKey=0x0, encAlgorithm=cryptRC4, keyLength=0,
    objNum=0, objGen=0) at Parser.cc:108
#7  0x00005555556b6a99 in XRef::fetch (this=<optimized out>, num=5, gen=0, obj=0x7fffff7ff400) at XRef.cc:811
#8  0x0000555555653927 in Object::fetch (this=<optimized out>, xref=0x555555c708f0, obj=0x7fffff7ff400) at Object.cc:106
#9  0x00005555555c7eaa in Dict::lookup (this=0x555556d6dee0, key=0x5555558f21c1 "Length", obj=0x7fffff7ff400) at Dict.cc:76
#10 0x000055555582db60 in Object::dictLookup (this=<optimized out>, key=0x4 <error: Cannot access memory at address 0x4>,
    obj=0x55550000000d) at ./Object.h:253

This crash was found with Angora fuzzer, and pdf2json_crash is originated from sample pdf file dummy.pdf which is also attached.

Hope this help.

pdf2json_crash.pdf
dummy.pdf