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Date: Sat, 5 Nov 2016 10:04:30 -0300
From: Gustavo Grieco <gustavo.grieco@...il.com>
To: oss-security@...ts.openwall.com
Subject: CVE request: Null pointer derefence parsing xml file using libxml
 2.9.4 (in recover mode)

Hi,

We found a null pointer dereference when parsing a xml file using recover
mode. It was tested in libxml 2.9.4 (ArchLinux x86_64). To reproduce:

$ xmllint --recover crash-libxml2-recover.xml

==27646==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000
(pc 0x0000004fbd88 bp 0x7ffc3345dff0 sp 0x7ffc3345dfd0 T0)
    #0 0x4fbd87 in xmlDumpElementContent
/home/g/Work/Code/libxml2-2.9.4/valid.c:1181
    #1 0x4fbcd5 in xmlDumpElementContent
/home/g/Work/Code/libxml2-2.9.4/valid.c:1177
    #2 0x4fe5ff in xmlDumpElementDecl
/home/g/Work/Code/libxml2-2.9.4/valid.c:1706
    #3 0x72e714 in xmlBufDumpElementDecl
/home/g/Work/Code/libxml2-2.9.4/xmlsave.c:501
    #4 0x73048f in xmlNodeDumpOutputInternal
/home/g/Work/Code/libxml2-2.9.4/xmlsave.c:939
    #5 0x72fc47 in xmlNodeListDumpOutput
/home/g/Work/Code/libxml2-2.9.4/xmlsave.c:825
    #6 0x72f6d5 in xmlDtdDumpOutput
/home/g/Work/Code/libxml2-2.9.4/xmlsave.c:749
    #7 0x73038f in xmlNodeDumpOutputInternal
/home/g/Work/Code/libxml2-2.9.4/xmlsave.c:931
    #8 0x732412 in xmlDocContentDumpOutput
/home/g/Work/Code/libxml2-2.9.4/xmlsave.c:1234
    #9 0x735883 in xmlSaveDoc /home/g/Work/Code/libxml2-2.9.4/xmlsave.c:1936
    #10 0x40ba0f in parseAndPrintFile
/home/g/Work/Code/libxml2-2.9.4/xmllint.c:2712
    #11 0x411eb6 in main /home/g/Work/Code/libxml2-2.9.4/xmllint.c:3767
    #12 0x7f23dcd4c290 in __libc_start_main (/usr/lib/libc.so.6+0x20290)
    #13 0x4032b9 in _start
(/home/g/Work/Code/libxml2-2.9.4/xmllint+0x4032b9)


A reproducer is attached. It is interesting to note that the developers of
libxml2 strongly recommend not to use recover mode to parse untrusted
inputs. Please assign a CVE if suitable.

Regards,
Gustavo.

[ CONTENT OF TYPE text/html SKIPPED ]

<?xml version="1.0"?>
<!DOCTYPE root [
  <!ELEMENT root (a,b)>
  <!ELEMENT a EMPTY>
  <!ELEMENT b (#PCDATA|c)* >
  <!ELEMENT c ANY>
  <!ELEMENT d ANY>
  <!ELEMENT e ANY>
  <!ELEMENT f ANY>
  <!--* test all pble children,cp,choice,seq patterns in P47,P48,P49,P-->
  <!ELEMENT child0 (a)>
  <!ELEMENT child1 (a|b|c)>
  <!ELEMENT child2 (a ,b,b?,a*,c,c,a,a,b+,c ) >
  <!ELEMENT child3 (a+|b)? >
  <!ELEMENT child4 (a, (b|cp+, (a|d)?, (e|f)* )?>
  <!ELEMENT child5 ( (a,b) | c? | ((d|e),b,c) )* >
  <!ELEMENT child5_1 ( (ab)* | (c,b)? | (d,a)+ | ((e|f),b,c) )* >
  <!ELEMENT child6 (a,b,c)*>
  <!ELEMENT child7 ((a,b)|c*|((d|e),b,c) )+ >
  <!ELEMENT child8 ( a, (bb), b)+>  
]>
<root><a/><b>
   <c></c >
   content of b element
</b></root>
<!--* test: tests P47,P48,P49,P50*-->

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