security: fix auth timing attack#345
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hongkongkiwi wants to merge 3 commits intoexpressvpn:mainfrom
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Prevent username enumeration via timing attack by always calling password verification with a fake hash when user is not found. Also use generic 'Authentication failed' log message to prevent username enumeration via log messages. Co-authored-by: Claude <noreply@anthropic.com>
- Remove duplicate "a" test case for min_length - Fix max_length_50 and too_long_51 strings to be exactly 50 and 51 chars - Change "Invalid username format" log to "Authentication failed" to avoid leaking validation rules to potential attackers Co-Authored-By: Claude <noreply@anthropic.com>
- Use valid bcrypt hash for FAKE_HASH to ensure constant-time verification (was using invalid all-ff chars which could short-circuit verification) - Add explicit user_exists check before granting auth to prevent granting access when user doesn't exist even if password verification passes Co-Authored-By: Claude <noreply@anthropic.com>
hongkongkiwi
changed the title
| // Validate username format before any other processing | ||
| if !is_valid_username(user) { | ||
| tracing::info!("Invalid username format"); | ||
| tracing::info!("Authentication failed"); |
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This log is in the server side. I don't understand how does this leak this info to attackers?
| #[test_case("abcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabc" => true; "max_length_50")] | ||
| #[test_case("abcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabca" => false; "too_long_51")] | ||
| #[test_case("abcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcab" => true; "max_length_50")] | ||
| #[test_case("abcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabcabc" => false; "too_long_51")] |
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This commit does not serve any purpose. Please squash all commits into one
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Summary
Prevent username enumeration via timing attack by always calling password verification with a fake hash when user is not found.
Changes
authorize_user_password()inauth.rsto always verify password even when user not foundis_valid_username()Security Impact
Fixes username enumeration vulnerability where attackers could distinguish valid from invalid usernames based on response timing.
Tests Added