security: use constant-time comparison for password hash check - #104
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security: use constant-time comparison for password hash check#104tas50 wants to merge 1 commit into
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CheckPasswd compared the stored password hash against the computed hash with the `!=` operator, which short-circuits on the first differing byte. This endpoint (/authenticate_user) is unauthenticated and accepts an attacker-supplied name/password, so the comparison is a timing oracle. Use crypto/subtle.ConstantTimeCompare instead. Signed-off-by: Tim Smith <tsmith84@proton.me>
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Issue
User.CheckPasswdcompares the stored password hash against the freshly computed hash with!=:Go's string
!=short-circuits on the first differing byte, so comparison time leaks how many leading bytes matched. The/authenticate_userendpoint is unauthenticated and accepts an attacker-controlledname/password, making this a timing oracle on the hash comparison — exactly the path where a constant-time comparison is expected.Fix
Compare with
crypto/subtle.ConstantTimeCompare.Verification
go build ./...,go vet ./user/, andgo test ./user/pass.