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package server
import (
"crypto/subtle"
"testing"
)
// TestConstantTimePasswordCompare verifies that password comparisons use
// constant-time comparison to prevent timing side-channel attacks.
// This is a regression test for the bug where `!=` was used directly,
// leaking timing information to an attacker who can measure response latency.
func TestConstantTimePasswordCompare(t *testing.T) {
t.Parallel()
tests := []struct {
name string
a string
b string
wantSame bool
}{
{"equal passwords", "secret123", "secret123", true},
{"different passwords", "secret123", "wrongpass", false},
{"empty vs non-empty", "", "secret", false},
{"both empty", "", "", true},
{"prefix match only", "secret", "secretXYZ", false},
{"suffix match only", "XYZsecret", "secret", false},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
t.Parallel()
// secretsEqual is the function under test — it must use
// crypto/subtle.ConstantTimeCompare, not plain ==.
got := secretsEqual(tt.a, tt.b)
if got != tt.wantSame {
t.Errorf("secretsEqual(%q, %q) = %v, want %v",
tt.a, tt.b, got, tt.wantSame)
}
// Cross-check with the reference implementation to ensure our
// helper is semantically correct, not just timing-safe.
reference := subtle.ConstantTimeCompare([]byte(tt.a), []byte(tt.b)) == 1
if got != reference {
t.Errorf("secretsEqual(%q, %q) = %v but crypto/subtle gives %v",
tt.a, tt.b, got, reference)
}
})
}
}
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