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Threat Model Analysis for robbiehanson/cocoaasyncsocket

Threat: TLS/SSL Man-in-the-Middle (MitM) Attack via Certificate Validation Bypass

  • Description: An attacker intercepts the TLS/SSL handshake by presenting a forged certificate. The attacker might use a self-signed certificate, a certificate signed by an untrusted CA, or a valid certificate for a different domain. If the application's CocoaAsyncSocket implementation doesn't properly validate the certificate within the delegate methods, the attacker can decrypt, modify, and re-encrypt the traffic. This is a direct misuse of CocoaAsyncSocket's TLS features.
  • Impact: Complete compromise of confidentiality and integrity of communication. Sensitive data can be stolen or modified. The attacker can inject malicious data.
  • Affected Component: GCDAsyncSocket's startTLS: method and related delegate methods: socket:didReceiveTrust:completionHandler:, socket:didConnectToHost:port:. Specifically, incorrect or missing implementation of certificate validation within these methods.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Strict Certificate Validation: Implement correct and complete certificate validation in the socket:didReceiveTrust:completionHandler: delegate method. Never call the completion handler with YES without thorough validation using SecTrustEvaluateWithError.
    • Check Certificate Chain: Verify the entire certificate chain up to a trusted root CA.
    • Hostname Verification: Ensure the certificate's CN or SAN matches the expected hostname.
    • Certificate Pinning (Strongly Recommended): Store a hash of the expected server certificate (or public key) and compare it during the handshake.
    • Disable Weak Ciphers: Configure GCDAsyncSocket (via the sslSettings dictionary in startTLS:) to use only strong cipher suites and TLS versions (TLS 1.2, TLS 1.3).
    • Use kCFStreamSSLValidatesCertificateChain: Set to true in sslSettings.

Threat: Data Tampering in Transit (No TLS/SSL)

  • Description: An attacker on the network path intercepts and modifies data sent over a plain TCP or UDP connection. This occurs when the application chooses not to use CocoaAsyncSocket's TLS/DTLS capabilities. This is a direct result of not using a core security feature of the library.
  • Impact: Loss of data integrity. The attacker can inject malicious data or corrupt existing data.
  • Affected Component: GCDAsyncSocket (when not using startTLS:) and GCDAsyncUdpSocket (when not using DTLS). The absence of using the security features.
  • Risk Severity: Critical (if sensitive data is transmitted), High (otherwise)
  • Mitigation Strategies:
    • Use TLS/SSL (TCP): Always use GCDAsyncSocket's startTLS: method with proper certificate validation for TCP connections.
    • Use DTLS (UDP): Always use GCDAsyncUdpSocket's DTLS support for UDP connections when transmitting sensitive data.

Threat: Resource Exhaustion (Socket Flooding) - Directly related to CocoaAsyncSocket usage

  • Description: An attacker opens many TCP connections or sends a flood of UDP packets. While resource exhaustion is a general concept, this threat is directly related to how the application uses CocoaAsyncSocket to accept connections or receive data. The library provides the mechanism for connection/packet handling, and the application's use (or misuse) of this mechanism creates the vulnerability.
  • Impact: Denial of Service (DoS).
  • Affected Component: GCDAsyncSocket (listening socket, specifically the acceptOnInterface:port:error: and related delegate methods) and GCDAsyncUdpSocket (receiving data). The core socket listening and receiving functionality.
  • Risk Severity: High
  • Mitigation Strategies:
    • Connection Limits: Limit the maximum number of concurrent connections accepted by the GCDAsyncSocket listening socket.
    • Timeouts: Use GCDAsyncSocket's readTimeout and writeTimeout properties on accepted sockets. Use appropriate timeouts for GCDAsyncUdpSocket's receive operations.
    • Rate Limiting (UDP): Implement rate limiting for incoming UDP packets in conjunction with GCDAsyncUdpSocket.

Threat: Slow Read/Write DoS Attack - Directly related to CocoaAsyncSocket usage

  • Description: An attacker establishes a TCP connection but sends/receives data very slowly. This is a direct attack on how the application uses CocoaAsyncSocket's read/write APIs. The vulnerability exists because of how the application handles the asynchronous I/O provided by the library.
  • Impact: Denial of Service (DoS).
  • Affected Component: GCDAsyncSocket's read and write operations (specifically, the asynchronous delegate methods like socket:didReadData:withTag: and socket:didWriteDataWithTag:). The core asynchronous I/O handling.
  • Risk Severity: High
  • Mitigation Strategies:
    • Read and Write Timeouts: Must use GCDAsyncSocket's readTimeout and writeTimeout properties with appropriate values. This is the primary defense and directly uses CocoaAsyncSocket's features.
    • Asynchronous Operations: Ensure all read/write operations are performed asynchronously using CocoaAsyncSocket's delegate methods.

Threat: CocoaAsyncSocket Library Vulnerability Exploitation

  • Description: A vulnerability is discovered within the CocoaAsyncSocket library itself (e.g., a buffer overflow in the parsing of TLS records). This is a direct threat to the library's code.
  • Impact: Varies; could range from DoS to Remote Code Execution (RCE).
  • Affected Component: Potentially any part of GCDAsyncSocket or GCDAsyncUdpSocket.
  • Risk Severity: High to Critical (depending on the vulnerability)
  • Mitigation Strategies:
    • Keep Updated: Regularly update CocoaAsyncSocket to the latest version. This is the most important mitigation.
    • Input Validation (Secondary): While not a direct fix for a library vulnerability, robust input validation in the application can sometimes mitigate the impact.