Paul HittandClaude Opus 4.8
b0c5a108b2
The engine had no head-signature function at all and Trust.head() threw the signature away, so a fork was an accusation rather than evidence. KeyLog.verifyHead now checks the same string the relay signs, the issuer key is pinned in the vault on first sight, and a head that fails under the pin raises the standing fork alarm. Four tests pin the string and the refusals — including a head signed by a different key, which is the substitution the pin exists to stop. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
47 lines
1.8 KiB
Kotlin
47 lines
1.8 KiB
Kotlin
package io.flamenet.e2e
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import kotlin.test.Test
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import kotlin.test.assertFalse
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import kotlin.test.assertTrue
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/**
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* Audit M1: a log head is only evidence if its signature verifies under the
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* PINNED issuer key. These pin the exact string the relay signs
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* (`fnkt-v1|<size>|<root>`) so the two implementations cannot drift apart —
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* a mismatch there would silently turn every head into "unverifiable".
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*/
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class KeyLogHeadSignatureTest {
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private val issuer = Ed25519.generate()
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private fun sign(size: Int, root: String): ByteArray =
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Ed25519.sign(issuer.seed, "fnkt-v1|$size|$root".toByteArray(Charsets.UTF_8))
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@Test fun `a genuine head verifies`() {
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val root = Bytes.b64(ByteArray(32) { 7 })
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assertTrue(KeyLog.verifyHead(12, root, sign(12, root), issuer.publicKey))
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}
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@Test fun `a head signed for a different size is refused`() {
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val root = Bytes.b64(ByteArray(32) { 7 })
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assertFalse(KeyLog.verifyHead(13, root, sign(12, root), issuer.publicKey),
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"a relay must not be able to replay a signature onto another size")
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}
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@Test fun `a head signed for a different root is refused`() {
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val real = Bytes.b64(ByteArray(32) { 7 })
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val forged = Bytes.b64(ByteArray(32) { 9 })
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assertFalse(KeyLog.verifyHead(12, forged, sign(12, real), issuer.publicKey),
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"swapping the root is exactly the fork this signature exists to catch")
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}
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@Test fun `a head signed by another key is refused`() {
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val other = Ed25519.generate()
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val root = Bytes.b64(ByteArray(32) { 7 })
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val bySomeoneElse = Ed25519.sign(
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other.seed, "fnkt-v1|12|$root".toByteArray(Charsets.UTF_8))
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assertFalse(KeyLog.verifyHead(12, root, bySomeoneElse, issuer.publicKey),
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"the PIN is what decides; a freshly served key must not substitute")
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}
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}
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