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GHSA-qjrq-hm79-49ww

MediumCVSS 5.9 / 10
Published May 22, 2023·Last modified Nov 8, 2023
Affected Components(0)

No affected components available

Description

Timing attacks occur when an attacker can guess a secret by observing a difference in processing time for valid and invalid inputs. Sensitive secrets such as passwords, token and API keys should be compared only using a constant-time comparision function. More information on this attack type can be found in this blog post.

Root Cause Analysis

In this case, the vulnerability occurs due to the following code.

https://github.com/ginuerzh/gost/blob/1c62376e0880e4094bd3731e06bd4f7842638f6a/auth.go#L46-L46

Here, a untrusted input, sourced from a HTTP header, is compared directly with a secret. Since, this comparision is not secure, an attacker can mount a side-channel timing attack to guess the password.

Remediation

This can be easily fixed using a constant time comparing function such as crypto/subtle's ConstantTimeCompare. An example fix can be found in https://github.com/runatlantis/atlantis/commit/48870911974adddaa4c99c8089e79b7d787fa820 Alternatively, one can apply the patch below

From d18cff85e1a565f688f717fd8f2cacea62ff9dbf Mon Sep 17 00:00:00 2001
From: Porcupiney Hairs <porcupiney.hairs@protonmail.com>
Date: Sun, 7 May 2023 01:03:33 +0530
Subject: [PATCH] Fix : Timing attack

---
 auth.go | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/auth.go b/auth.go
index 1be96e9..be13f23 100644
--- a/auth.go
+++ b/auth.go
@@ -2,6 +2,7 @@ package gost
 
 import (
 	"bufio"
+	"crypto/subtle"
 	"io"
 	"strings"
 	"sync"
@@ -43,7 +44,8 @@ func (au *LocalAuthenticator) Authenticate(user, password string) bool {
 	}
 
 	v, ok := au.kvs[user]
-	return ok && (v == "" || password == v)
+	passOk := subtle.ConstantTimeCompare([]byte(password), []byte(v)) == 0
+	return ok && (v == "" || passOk)
 }
 
 // Add adds a key-value pair to the Authenticator.
-- 
2.25.1

Risk Scores
Base Score
5.9

The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information. There is a low impact on the integrity of the data.

Threat Intelligence
5.4

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
0.57%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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