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[bug-libextractor] NULL Pointer Dereference vulneribility in libextracto

From: Leon Zhao
Subject: [bug-libextractor] NULL Pointer Dereference vulneribility in libextractor EXTRACTOR_nsfe_extract_method
Date: Wed, 1 Nov 2017 14:19:11 +0800

Tested Version:
libextractor v1.6

Tested System:
Linux leon-virtual-machine 4.10.0-35-generic #39~16.04.1-Ubuntu SMP Wed Sep 13 09:02:42 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

In function EXTRACTOR_nsfe_extract_method at nsfe_extractor.c 
 345   if (sizeof (struct header) >
 346       ec->read (ec->cls,
 347                 &data,
 348                 sizeof (struct header)))
 349     return;
 350   head = data;
 351   if (0 != memcmp (head->magicid, "NSFE", 4))
 352     return;
 354   if (0 != ec->proc (ec->cls,
 355                      "nsfe",
 356                      EXTRACTOR_METATYPE_MIMETYPE,
 357                      EXTRACTOR_METAFORMAT_UTF8,
 358                      "text/plain",
 359                      "audio/x-nsfe",
 360                      strlen ("audio/x-nsfe") + 1))
 361     return;                        "nsfe",
ec->read function set data to NULL, so it crash when the code want to use magicid of pointer head in line 351.
Crash Information:
The output with address sanitizer enabled
./extract -i extract.EXTRACTOR_nsfe_extract_method.nsfe_extractor.351.crash 
Keywords for file extract.EXTRACTOR_nsfe_extract_method.nsfe_extractor.351.crash:
==19923==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x7ff41c8bdfe4 bp 0x7fffd3ba7bd0 sp 0x7fffd3ba7358 T0)
    #0 0x7ff41c8bdfe3  (/lib/x86_64-linux-gnu/libc.so.6+0x16efe3)
    #1 0x7ff41cdec74e in memcmp (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x7774e)
    #2 0x7ff416a919af in EXTRACTOR_nsfe_extract_method /root/libextractor-1.6/src/plugins/nsfe_extractor.c:351
    #3 0x7ff41cb359a1 in do_extract /root/libextractor-1.6/src/main/extractor.c:583
    #4 0x7ff41cb35db5 in EXTRACTOR_extract /root/libextractor-1.6/src/main/extractor.c:662
    #5 0x4044f9 in main /root/libextractor-1.6/src/main/extract.c:983
    #6 0x7ff41c76f82f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)
    #7 0x4017c8 in _start (/opt/asan/bin/extract+0x4017c8)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV ??:0 ??

Zhao Liang, Huawei Weiran Labs

Attachment is POC file

Attachment: extract.EXTRACTOR_nsfe_extract_method.nsfe_extractor.351.crash
Description: Binary data

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