Use of a Broken or Risky Cryptographic Algorithm (CWE-327) in libcurl

How it was found

Summary:

The DES cipher (Data Encryption Standard) is used in the curl_ntlm_core.c file of libcurl. DES is considered insecure due to its short key length (56 bits) and its susceptibility to brute-force attacks. Modern cryptographic standards recommend replacing DES with AES (Advanced Encryption Standard), which is more robust and secure.

Affected version

[Which curl/libcurl version are you using to reproduce? On which platform? curl -V typically generates good output to include]

Steps To Reproduce:

1. Inspect the lib/curl_ntlm_core.c file of the libcurl source code.
2. Locate the use of the kCCAlgorithmDES constant, which corresponds to the DES cipher.
3. Verify that DES is being used for cryptographic operations in NTLM authentication (NTLMv1).

Supporting Material/References:

• File: lib/curl_ntlm_core.c

• Line Reference: 228:29

• CWE Reference: CWE-327

  • [attachment / reference]

Impact

Summary:

Using DES compromises the security of the application due to the following points:

• Brute-force attacks: The short key length makes it possible to brute-force DES keys in a reasonable amount of time with modern hardware.
• Cryptographic weaknesses: DES is vulnerable to various cryptanalysis techniques, such as differential and linear cryptanalysis.
• Compliance risks: DES does not meet modern cryptographic standards and could lead to non-compliance with security regulations.

An attacker exploiting this vulnerability could:

• Intercept and decrypt sensitive data during NTLM authentication.
• Execute man-in-the-middle (MITM) attacks to impersonate a user or server.
• Gain unauthorized access to systems relying on NTLM authentication.

Recommended Fix:

Replace the use of kCCAlgorithmDES with kCCAlgorithmAES, which supports stronger encryption standards (e.g., AES-128, AES-256). This change will significantly enhance the security of NTLM authentication in libcurl.