0

Insecurities Of WhatsApp's, Signal's, And Threema's Group Chats

Recently, the theoretical and practical analysis of secure instant messenger protocols received much attention, but the focus of prior evaluations mostly lay in one-to-one communication. In this blog post we want to presents the results of our work that focuses on group chat protocols of three major instant messenger applications; namely Signal, WhatsApp, and Threema.

In this blog post, we aim to focus on the practical impact and the found weaknesses identified by our analysis. The interested reader may also look into our paper for more details.


Our Aim and What We Were Looking For

End-to-end encryption protects the confidentiality of communication that is forwarded via central servers to the designated receivers. As a consequence, neither parties on the network route of the messages, nor the provider of the central server (e.g. the WhatsApp server) should be able to read any information out of the observation of the communication. In particular, no other user of the application should have access to the communication. Further it might be desirable to require that also the messages' integrity is end-to-end protected and that a sender is informed about the delivery state of sent messages.
Delivery state information in Signal (upper screenshot) and WhatsApp (lower screenshot)

In a two party scenario, this analysis is rather fixed to two components of the protocol: the key establishment between both parties and the communication channel protection using the established key (mostly consisting of an encryption algorithm and a scheme for providing integrity like MACs or signature schemes).

Regarded attackers


In a group setting, the same attackers apply (network, provider, other users). However the requirements for secure communication differ. It is further necessary that only group members can write to and read content from the group. Additionally, only administrators of the group are able to add new members.

In addition to these standard requirements, we also evaluated the protocols' security guarantees if the client's secrets were revealed (forward secrecy and future secrecy).

Our Approach

We analyzed the mentioned protocols by reading the source code and debugging the apps. We also used alternative open source implementations of Threema and WhatsApp as a help and we traced the network traffic. When using alternative implementations, we only took incoming traffic into account, which was generated by official applications. Thereby we extracted the protocol descriptions and evaluated them regarding the defined requirements.

Our Findings

In WhatsApp and Threema, the provider was able to manipulate the set of members. Threema only allowed the provider to rewind the set of members to a previous state. As a consequence previously removed members could have been added to the group again. The WhatsApp provider is able to arbitrarily manipulate the member set. Thereby further members and administrators can be added to the group. Since the authenticity of group manipulation is not protected, the WhatsApp provider can set the real group administrator as the source of manipulation even though this administrator was not active.

Since Signal's key exchange protocol provides future secrecy, we also evaluated the protocol's ability to recover into a secure group state after a member's state was compromised. The essential weakness here is that a sender only needs to know the static group ID to send a message to the group. If a group member receives a message with the correct group ID, no verification regarding the current member set takes place but the message is directly added to the group communication. Consequently it is sufficient to retrieve the group ID in order to send messages to the group. Since Signal treats content messages the same way as messages for the manipulation of the group set, an attacker who knows the group ID can add herself to the group and thereby read the subsequent group communication.

In addition to this, in all cases the delivery state of sent messages was not securely provided. Threema's group chats do not inform the sender about the delivery state while Signal and WhatsApp do not protect the delivery information on the end-to-end layer. Therefore the central provider can forge this information and drop messages without letting the communicating parties detect this.

Also the order of messages was manipulable for the providers of the applications such that the provider is able to deliver the messages in a different order than they were sent. Threema's weakness of rewinding a group state results from missing replay attack protection.

Impact of Weaknesses

Even though end-to-end encryption is implemented in all analyzed applications, the central providers can largely manipulate the communication in groups and partially also read it.
In all applications, the provider can undetectably drop and reorder messages during the delivery and thereby manipulate the view of the communication such that further attacks can be obfuscated.
The central servers of WhatsApp can be used to add arbitrary users to groups and thereby receive their communication.
To achieve the same result for Signal, it suffices to retrieve the group ID. An earlier member who left the group once still knows this ID since it is static. However, in contrast to WhatsApp, the origin of the manipulation is correctly displayed in the Signal application (which was not the fact when we started our analysis).

As a result, the end-to-end protection of WhatsApp is not sufficient to reach confidentiality in groups. For Signal no future secrecy is reached in groups and Threema was vulnerable to replay attacks which resulted in further weaknesses.

Responsible Disclosure

We disclosed our findings to the developers and received varying response. Threema updated their protocol in version 3.14 such that our attacks are not feasible anymore. Moxie Marlinspike responded that Signal is "working on an entirely new group mechanism that we should be deploying soon". WhatsApp did not hold out the prospect of fixing the described vulnerabilities (Update 01/18: According to Facebook's Security Head, the invite links make a fix more difficult [1]; we proposed a way to solve this issue [2]).

[1] https://twitter.com/alexstamos/status/951169036947107840
[2] https://web-in-security.blogspot.de/2018/01/group-instant-messaging-why-baming.html

Continue reading


  1. Hack Tools For Games
  2. Game Hacking
  3. Hack Tools Mac
  4. Hacker Tools Hardware
  5. New Hack Tools
  6. Hacking Tools Name
  7. Pentest Tools Website
  8. Pentest Tools For Android
  9. Pentest Tools For Mac
  10. Wifi Hacker Tools For Windows
  11. Hacking Tools Download
  12. Nsa Hack Tools Download
  13. Hack App
  14. Pentest Tools Windows
  15. New Hacker Tools
  16. Game Hacking
  17. Hacking Tools For Games
  18. Hacker Tools For Mac
  19. Best Hacking Tools 2019
  20. Pentest Tools Alternative
  21. Hacker Tools Windows
  22. Pentest Tools For Mac
  23. Hack Tools Mac
  24. Kik Hack Tools
  25. Hack Tools Mac
  26. Hack And Tools
  27. Hack And Tools
  28. Pentest Tools Framework
  29. Pentest Tools Android
  30. Hacking Tools Windows 10
  31. What Is Hacking Tools
  32. Hack Tools Github
  33. Hacker Security Tools
  34. Hack Tools For Mac
  35. Hacking Tools Free Download
  36. Hack Tools Github
  37. Hack Tools For Pc
  38. Pentest Tools Port Scanner
  39. Pentest Tools For Windows
  40. Pentest Tools
  41. How To Hack
  42. Hacker Tools
  43. Pentest Tools Framework
  44. Hacker Tool Kit
  45. Hacking Apps
  46. Pentest Box Tools Download
  47. How To Install Pentest Tools In Ubuntu
  48. Android Hack Tools Github
  49. Hacker Tools Apk
  50. Tools Used For Hacking
  51. Bluetooth Hacking Tools Kali
  52. Hacker Tools For Mac
  53. Hack Tools For Games
  54. Best Hacking Tools 2019
  55. Hacker Tools Online
  56. Hacking Tools
  57. Hack Tools For Mac
  58. Hack Website Online Tool
  59. Pentest Tools Windows
  60. Hacker Tools For Pc
  61. Pentest Recon Tools
  62. Hacking Tools For Windows
  63. Pentest Reporting Tools
  64. Free Pentest Tools For Windows
  65. Hacker Tools Free Download
  66. Hack Tools
  67. Hacker Tools List
  68. Hack Tools For Ubuntu
  69. Pentest Tools Windows
  70. Best Hacking Tools 2019
  71. Hacking Tools For Windows
  72. Hacking Tools Free Download
  73. Hacking Tools 2019
  74. Hacker Tools For Mac
  75. Nsa Hack Tools Download
  76. Hacking Tools For Windows 7
  77. Pentest Tools Website Vulnerability
  78. Pentest Tools Website Vulnerability
  79. Hacker Tools Apk
  80. Hacker Tools Github
  81. Bluetooth Hacking Tools Kali
  82. Black Hat Hacker Tools
  83. Hacker Tools For Windows
  84. Hack Tools Online
  85. Pentest Tools Bluekeep
  86. Hacking Tools For Windows 7
  87. Hacker Tools Linux
  88. Best Hacking Tools 2020
  89. Hack Apps
  90. Hackrf Tools
  91. Hacking Tools For Windows
  92. Hack And Tools
  93. Hack Tools
  94. Hacking Apps
  95. Hacking Tools For Kali Linux
  96. Pentest Reporting Tools
  97. Nsa Hacker Tools
  98. Pentest Reporting Tools
  99. Hacker Tools Apk Download
  100. Hacker Tools

0 critiques:

Post a Comment

Back to Top