KeyStoreChallenge.kt

object KeyStoreChallenge {
    private val TAG = "KeyAttestation"

    /**
     * How to verify see to
     * https://developer.android.com/privacy-and-security/security-key-attestation?hl=zh-cn#key_attestation_ext_schema
     */
    fun <T> use(alias: String, challenge: ByteArray, block: (Boolean, List<PEM>) -> T): T {
        if (!this.challenge(alias, true, challenge)) {
            if (!this.challenge(alias, false, challenge)) {
                return block(false, listOf())
            }
        }

        val (okay, certs) = this.load(alias)
        return block(okay, certs)
    }

    fun load(alias: String): Pair<Boolean, List<PEM>> {
        val keyStore = KeyStore.getInstance("AndroidKeyStore")
        keyStore.load(null)
        val certChain = keyStore.getCertificateChain(alias)
        if (certChain == null || certChain.isEmpty()) {
            Log.e(TAG, "cannot found certificate chain within $alias")
            return Pair(false, listOf())
        }

        val certs = mutableListOf<ByteArray>()
        certChain.forEach { cert ->
            certs.add(cert.encoded)
        }

        return Pair(certs.isNotEmpty(), certs)
    }

    fun challenge(
        alias: String,
        devicePropertiesAttestationIncluded: Boolean,
        challenge: ByteArray
    ): Boolean {
        if (challenge.isNotEmpty() && challenge.size < 16) {
            throw RuntimeException("challenge must be gt 16 bytes or be empty(disable challenge)")
        }
        val now = Date()
        // https://docs.oracle.com/en/java/javase/17/docs/specs/security/standard-names.html#parameterspec-names
        val spec = ECGenParameterSpec("secp256r1")
        val builder = KeyGenParameterSpec.Builder(
            alias,
            KeyProperties.PURPOSE_SIGN or KeyProperties.PURPOSE_VERIFY
        ).setAlgorithmParameterSpec(spec)
            .setDigests("SHA-256", "SHA-384", "SHA-512")
            .setKeyValidityStart(now)

        if (Build.VERSION.SDK_INT > 17 && challenge.isNotEmpty()) {
            builder.setAttestationChallenge(challenge)
        }
        if (Build.VERSION.SDK_INT >= 31) {
            // need READ_PHONE_STATE permission
            builder.setDevicePropertiesAttestationIncluded(devicePropertiesAttestationIncluded)
        }

        val generator =
            KeyPairGenerator.getInstance(KeyProperties.KEY_ALGORITHM_EC, "AndroidKeyStore")
        generator.initialize(builder.build())

        val keyPair = try {
            // https://developer.android.com/reference/android/security/keystore/KeyGenParameterSpec.Builder#setDevicePropertiesAttestationIncluded(boolean)
            // KeyGenerator.generateKey() will throw ProviderException if device properties attestation fails or is not supported.
            generator.generateKeyPair()
        } catch (_: ProviderException) {
            return false
        }
        Log.d(TAG, "generate public key success: ${keyPair.public.encoded.toPemString()}")
        // It should be null if the operator from tee
        Log.d(TAG, "generate private key success: ${keyPair.private?.encoded.toPemString()}")

        return true
    }
}

TeeCertChains.kt

    // 依赖项目: https://github.com/android/keyattestation
    fun tee_cert_chains(@RequestBody body: String): String {
        var description: KeyDescription? = null
        val certs = mutableListOf<X509Certificate>()
        val x509 = CertificateFactory.getInstance("X.509")
        body.byteInputStream().use { input ->
            for (certificate in x509.generateCertificates(input)) {
                if (certificate is X509Certificate) {
                    if (certificate.hasAttestationExtension()) {
                        description = certificate.keyDescription()
                    }
                    certs.add(certificate)
                }
            }
        }
        val verifier = Verifier(
            { GoogleTrustAnchors() },
            { setOf<String>() },
            { Instant.now() }
        )
        val result = verifier.verify(certs)
        val j = JSONObject()
        val applicationId = description?.hardwareEnforced?.attestationApplicationId
            ?: description?.softwareEnforced?.attestationApplicationId
        val pkg = JSONArray()
        val sig = JSONArray()
        applicationId?.packages?.forEachIndexed { index, info ->
            JSONObject().put("应用包名", info.name)
                .put("应用版本", info.version)
                .let(pkg::put)
        }
        applicationId?.signatures?.map { sig.put(it.toByteArray().toHexString()) }
        j.put("签名应用", pkg)
        j.put("签名信息", sig)
        j.put("系统版本", description?.hardwareEnforced?.osVersion)
        j.put("系统补丁版本", description?.hardwareEnforced?.osPatchLevel)
        j.put("实际签署时间", description?.softwareEnforced?.creationDateTime)
        j.put("申请签署时间", description?.softwareEnforced?.activeDateTime)
        j.put("证书验证成功", false)

        when (result) {
            is VerificationResult.Success -> {
                j.put("证书验证成功", true)
                j.put("公钥", result.publicKey)
                j.put("安全等级", result.securityLevel)
                j.put("解锁状态", result.verifiedBootState)
                with(result.attestedDeviceIds) {
                    val imei = JSONArray()
                    imeis.forEach { imei.put(it) }
                    JSONObject().put("brand", brand)
                        .put("device", device)
                        .put("product", product)
                        .put("serial number", serialNumber)
                        .put("imei", imei)
                        .put("meid", meid)
                        .put("manufacturer", manufacturer)
                        .put("model", model)
                }.let { j.put("设备标识", it) }

                j.put("设备信息", result.deviceInformation)

                j.put("挑战字符(hex)", result.challenge.toByteArray().toHexString())
            }

            is VerificationResult.PathValidationFailure -> {
                j.put("错误信息", "证书链无效，不能验证来自Google CA签发")
            }

            else -> {
                j.put("错误信息", result.toString())
            }
        }

        return j.toString()
    }