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Attack Tree Analysis for schollz/croc

Objective: To gain unauthorized access to files transferred via croc, intercept and modify files in transit, or disrupt the croc relay service, ultimately compromising the confidentiality, integrity, or availability of data transferred by the application using croc.

Attack Tree Visualization

                                     Compromise Application Using Croc
                                                    |
        -----------------------------------------------------------------------------------------
        |                                               |                                       |
  1. Intercept & Decrypt Data                  2.  Manipulate Data in Transit         3. Disrupt Relay Service
        |                                               |                                       |
  -------------                                 -------------                       -------------
  |           |                                 |                                       |
1.1          1.2                                2.1                                     3.2
Weak         Compromise                         Modify                                  Compromise
PAKE         Relay [CRITICAL]                   File                                    Relay [CRITICAL]
Code                                           Content                                 Server
[HIGH RISK]                                    |                                       |
       |                                        |                                       |
       |-----------------                       |                                       |-----------------
       |                 |                       |                                       |                 |
    1.1.1             1.1.2                   2.1.1                                 3.2.1             3.2.2
    Brute-Force       Dictionary                Replace                                   Exploit           Inject
    PAKE Code         Attack on                 File with                                 Relay             Malicious
    [HIGH RISK]       PAKE Code                 Malware                                   Software          Code
                      [HIGH RISK]               [HIGH RISK]                               Vulnerability     (RCE)
                                                                                          [CRITICAL]        [CRITICAL]
        |                                               |                                       |
  2.2 Man-in-the-Middle (Relay)             1.2.2 Compromise Relay Code (RCE)
  [CRITICAL]                                [CRITICAL]

Attack Tree Path: 1. Intercept & Decrypt Data

  • 1.1 Weak PAKE Code [HIGH RISK]:

    • Description: The attacker exploits the use of a weak Password-Authenticated Key Exchange (PAKE) code chosen by the user. Weak codes are easily guessable or susceptible to brute-force attacks.
    • Sub-Attacks:
      • 1.1.1 Brute-Force PAKE Code [HIGH RISK]: The attacker systematically tries all possible combinations of the PAKE code until the correct one is found. This is more feasible if the PAKE code is short.
      • 1.1.2 Dictionary Attack on PAKE Code [HIGH RISK]: The attacker uses a list of common passwords, phrases, or previously leaked credentials to try and guess the PAKE code.
    • Likelihood: Medium (for weak PAKE codes), Low (for strong PAKE codes, but still high risk due to impact)
    • Impact: High (complete loss of data confidentiality)
    • Effort: Low to Medium (depending on PAKE code strength)
    • Skill Level: Novice to Intermediate
    • Detection Difficulty: Medium (detectable through failed login attempts, but requires proper logging and rate limiting)

  • 1.2 Compromise Relay Server [CRITICAL]:

    • Description: The attacker gains unauthorized access to and control over the croc relay server. This allows them to intercept, decrypt, and potentially modify all data passing through the relay.
    • Sub-Attacks:
      • 1.2.2 Compromise Relay Code (RCE) [CRITICAL]: The attacker exploits a Remote Code Execution (RCE) vulnerability in the relay server software, allowing them to execute arbitrary code on the server and gain full control.
    • Likelihood: Low
    • Impact: Very High (complete compromise of all data transiting the relay)
    • Effort: High to Very High
    • Skill Level: Expert
    • Detection Difficulty: Hard to Very Hard

Attack Tree Path: 2. Manipulate Data in Transit

  • 2.1 Modify File Content:

    • Description: The attacker, having gained access to the data stream (typically through relay compromise or MitM), alters the content of the file being transferred.
    • Sub-Attacks:
      • 2.1.1 Replace File with Malware [HIGH RISK]: The attacker replaces the legitimate file with a malicious file (e.g., a virus, Trojan horse, or ransomware).
    • Likelihood: Low (requires prior compromise)
    • Impact: High to Very High (data integrity loss, potential malware infection)
    • Effort: Medium
    • Skill Level: Intermediate
    • Detection Difficulty: Hard (without external integrity checks)

  • 2.2 Man-in-the-Middle (Relay) [CRITICAL]:

    • Description: The attacker positions themselves as the relay server, either by compromising the legitimate relay or by setting up a rogue relay and tricking the sender and receiver into using it. This allows the attacker to see and modify all traffic.
    • Likelihood: Low
    • Impact: Very High (complete control over the data transfer)
    • Effort: High
    • Skill Level: Expert
    • Detection Difficulty: Hard

Attack Tree Path: 3. Disrupt Relay Service

  • 3.2 Compromise Relay Server [CRITICAL]:
    • Description: Similar to 1.2, the attacker gains control of the relay server, but the goal here is disruption rather than data interception.
    • Sub-Attacks:
      • 3.2.1 Exploit Relay Software Vulnerability [CRITICAL]: The attacker exploits a vulnerability in the relay software to crash the server or otherwise make it unavailable.
      • 3.2.2 Inject Malicious Code (RCE) [CRITICAL]: Same as 1.2.2, but with the intent to disrupt service.
    • Likelihood: Low
    • Impact: Very High (relay becomes unavailable, disrupting all croc transfers using that relay)
    • Effort: High to Very High
    • Skill Level: Expert
    • Detection Difficulty: Hard to Very Hard (for RCE); Easy (for simple DoS)