ginuerzh/gost vulnerable to Timing Attack

Vulnerability

Overview Gost (GO Simple Tunnel) is a Go-based tunneling tool that supports proxy authentication. The vulnerability lies in the Authenticate function in auth.go [3]. The password comparison is performed using a direct string equality check (password == v) rather than a constant-time comparison function. This allows an attacker to use timing side-channel techniques to differentiate between valid and invalid passwords [1][4].

Exploitation

Method An attacker can send HTTP requests with varying password values in the authorization header and measure the server's response time. Due to the non-constant-time comparison, the processing time may vary based on how many characters match, enabling the attacker to iteratively guess the correct password [4]. No authentication is required to perform the attack; the attacker only needs network access to the gost server.

Impact

Successful exploitation could allow an attacker to bypass authentication and gain unauthorized access to the tunnel proxy, potentially leading to data interception, credential theft, or further compromise of internal networks.

Mitigation

The issue is fixed by using crypto/subtle's ConstantTimeCompare function, as shown in the advisory [4]. Users should update to a patched version or apply the provided patch. The maintainer has addressed the vulnerability in the repository.