这里有步骤 https://developer.android.com/training/safetynet/attestation.html#verify-attestation-response您需要按照 Google 的建议执行操作。
绝对可以随意浏览所有参考链接，以更好地了解该过程。请查看此处使用的每个库函数，了解它们在做什么以及这是否正是您希望它们执行的操作。我编写了伪代码来解释这些步骤。您可能需要在示例证明令牌上运行它们来测试它们并相应地更改一些内容。
如果能在一个地方查看 SafetyNet 的整个节点实现也是很好的。
// following steps should be performed
// 1. decode the JWS
// 2. the source of the first certificate in x5c array of jws header
// should be attest.google.com
// 3. to make sure if the JWS was not tampered with, validate the signature of JWS (how signature verification is done is explained in the reference links)
// with the certificate whose source we validated
// 4. if the signature was valid, we need to know if the certificate was valid by
// explicitly checking the certificate chain
// 5. Validate the payload by matching the package name, apkCertificateDigest
// and nonce value (apkCertificateDigest is base64 encoding of the hash of signing app's certificate)
// 6. and now you can trust the ctsProfileMatch and BasicIntegrity flags
// let's see some code in node, though this will not run as-is,
// it provides an outline on how to do it and which functions to consider when implementing
const pki = require('node-forge').pki;
const jws = require('jws');
const pem = require("pem");
const forge = require('node-forge');
const signedAttestation = "Your signed attestation here";
function deviceAttestationCheck(signedAttestation) {
// 1. decode the jws
const decodedJws = jws.decode(signedAttestation);
const payload = JSON.parse(decodedJws.payload);
// convert the certificate received in the x5c array into valid certificates by adding
// '-----BEGIN CERTIFICATE-----\n' and '-----END CERTIFICATE-----'
// at the start and end respectively for each certificate in the array
// and by adding '\n' at every 64 char
// you'll have to write your own function to do the simple string reformatting
// get the x5c certificate array
const x5cArray = decodedJws.header.x5c;
updatedX5cArray = doTheReformatting(x5cArray);
// 2. verify the source to be attest.google.com
certToVerify = updatedX5cArray[0];
const details = pem.readCertificateInfo(certToVerify);
// check if details.commanName === "attest.google.com"
const certs = updatedX5cArray.map((cert) => pki.certificateFromPem(cert));
// 3. Verify the signature with the certificate that we received
// the first element of the certificate(certs array) is the one that was issued to us, so we should use that to verify the signature
const isSignatureValid = jws.verify(signedAttestation, 'RS256', certs[0]);
// 4. to be sure if the certificate we used to verify the signature is the valid one, we should validate the certificate chain
const gsr2Reformatted = doTheReformatting(gsr2);
const rootCert = pki.certificateFromPem(gsr2Reformatted);
const caStore = pki.createCaStore([rootCert]);
// NOTE: this pki implementation does not check for certificate revocation list, which is something that you'll need to do separately
const isChainValid = pki.verifyCertificateChain(caStore, certs);
// 5. now we can validate the payload
// check the timestamps, to be within certain time say 1 hour
// check nonce value, to contain the data that you expect, refer links below
// check apkPackageName to be your app's package name
// check apkCertificateDigestSha256 to be from your app - quick tip -look at the function below on how to generate this
// finally you can trust the ctsProfileMatch - true/false depending on strict security need and basicIntegrity - true, minimum to check
}
// this function takes your signing certificate(should be of the form '----BEGIN CERT....data...---END CERT...') and converts into the SHA256 digest in hex, which looks like - 92:8H:N9:84:YT:94:8N.....
// we need to convert this hex digest to base64
// 1. 92:8H:N9:84:YT:94:8N.....
// 2. 928hn984yt948n - remove the colon and toLowerCase
// 3. encode it in base64
function certificateToSha256DigestHex(certPem) {
const cert = pki.certificateFromPem(certPem);
const der = forge.asn1.toDer(pki.certificateToAsn1(cert)).getBytes();
const m = forge.md.sha256.create();
m.start();
m.update(der);
const fingerprint = m.digest()
.toHex()
.match(/.{2}/g)
.join(':')
.toUpperCase();
return fingerprint
}
// 92:8H:N9:84:YT:94:8N => 928hn984yt948n
function stringToHex(sha256string) {
return sha256string.split(":").join('').toLowerCase();
}
// this is what google sends you in apkCertificateDigestSha256 array
// 928hn984yt948n => "OIHf9wjfjkjf9fj0a="
function hexToBase64(hexString) {
return Buffer.from(hexString, 'hex').toString('base64')
}
所有对我有帮助的文章：
- 步骤摘要 -Here https://stackoverflow.com/questions/44262107/how-does-ssl-hostname-matching-work-on-jws
- 深入解释与实施 -Here https://medium.com/@herrjemand/verifying-fido2-safetynet-attestation-bd261ce1978d
- 你应该记住的事情——Here https://android-developers.googleblog.com/2017/11/10-things-you-might-be-doing-wrong-when.html
- 谷歌的清单以正确执行 -Here https://developer.android.com/training/safetynet/attestation-checklist
- 深入研究这个过程 -Here https://www.blackhat.com/docs/eu-17/materials/eu-17-Mulliner-Inside-Androids-SafetyNet-Attestation.pdf
