在Android 上http 訪問采用雙向ssl 認證是一種很常見的場景腮猖。這種通常是Android作為客戶端税稼，訪問后臺服務器。Android 作為服務端的情況比較少見奈附。 下面就談談Android 同時作為服務端和客戶端的情況全度。
Android 客戶端的配置
Android 作為客戶端https 通信，通常需要一個SSLContext斥滤， SSLContext 需要配置一個 TrustManager将鸵，如果是雙向通信，還需要一個 KeyManager佑颇。
- 單行https TrustManager
- 雙向https TrustManager KeyManager
- KeyManager 負責提供證書和私鑰顶掉，證書發(fā)給對方peer
- TrustManager 負責驗證peer 發(fā)來的證書。
生成SSLContext
KeyManagerFactory kmf = KeyManagerFactory.getInstance(KeyManagerFactory.getDefaultAlgorithm());
TrustManagerFactory tmf = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
kmf.init(mKeyStore, mKeyPass.toCharArray());
tmf.init(mTrustStore);
SSLContext sslContext = SSLContext.getInstance("TLS");
sslContext.init(kmf.getKeyManagers(), tmf.getTrustManagers(), null);
和Http 客戶端關(guān)聯(lián)
OkHttp 客戶端如下：
SSLSocketFactory sslSocketFactory = sslContext.getSocketFactory();
X509TrustManager x509TrustManager = Platform.get().trustManager(sslSocketFactory);
OkHttpClient okHttpClient = new OkHttpClient
.Builder()
.addInterceptor(httpLoggingInterceptor)
.sslSocketFactory(sslSocketFactory, x509TrustManager)
.build();
mRetrofit = new Retrofit.Builder()
.baseUrl(mBaseHost)
.client(okHttpClient)
.addConverterFactory(GsonConverterFactory.create())
.build();
AndroidAsync 的客戶端：
AsyncHttpClient.getDefaultInstance().getSSLSocketMiddleware().setSSLContext(sslContext);
AsyncHttpClient.getDefaultInstance().getSSLSocketMiddleware().setTrustManagers(tmf.getTrustManagers());
如果是客戶單的話配置還是比較的簡單明了的
Android 作為Https 的服務端
在技術(shù)選型的時候選擇了 AndroidAsync 作為服務端的框架挑胸。另外一個是 NanoHTTPD
因為要同時實現(xiàn)客戶端和服務端痒筒，而且AndroidAsync 支持異步，更符合現(xiàn)在的Android 趨勢茬贵。
AndroidService 支持客戶端證書請求
客戶端按照上面的配置了一下簿透，服務端也如法炮制sslContext，AndroidAsync 提供了一個SSLTests 的測試用例解藻，采用自簽名證書方式老充。
AsyncHttpServer httpServer = new AsyncHttpServer();
httpServer.listenSecure(8888, sslContext);
httpServer.get("/", new HttpServerRequestCallback() {
@Override
public void onRequest(AsyncHttpServerRequest request, AsyncHttpServerResponse response) {
response.send("hello");
}
});
只能實現(xiàn)單向Https ,無法雙向。通過抓包對比螟左，發(fā)現(xiàn)雙向https 需要服務端向客戶端發(fā)送一個 Certificate Request啡浊。但是服務端沒有發(fā)送觅够。Android 上ssl 握手是通過openssl 實現(xiàn)的。通過查閱一些論文巷嚣，查看boringssl 源碼喘先，是一個變量沒有設置導致 handshake 的時候服務端沒有發(fā)送 Certificate Request。 修改boringssl 不太現(xiàn)實廷粒。換個思路這個變量是不是可以通過Java層控制窘拯。
public void listenSecure(final int port, final SSLContext sslContext) {
AsyncServer.getDefault().listen(null, port, new ListenCallback() {
@Override
public void onAccepted(AsyncSocket socket) {
AsyncSSLSocketWrapper.handshake(socket, null, port, sslContext.createSSLEngine(), null, null, false,
new AsyncSSLSocketWrapper.HandshakeCallback() {
@Override
public void onHandshakeCompleted(Exception e, AsyncSSLSocket socket) {
if (socket != null)
mListenCallback.onAccepted(socket);
}
});
}
......
});
}
通過對 AndroidAsync AsyncHttpServer 的實現(xiàn)分析，SSLContext的方法沒有我們要控制的功能坝茎。但是ssl 握手的時候創(chuàng)建了一個SSLEngine树枫。SSLEngine 的方法比較多的。
SSLEngine.setNeedClientAuth(true);
這個方法看起來比較靠譜景东。但是AndroidAsync 框架并沒有提供API砂轻，想辦法把這個類拿出來重寫。服務端用SslAsyncHttpServer 替換AsyncHttpServer斤吐， Certificate Request 終于發(fā)出來了搔涝。
class SslAsyncHttpServer extends AsyncHttpServer {
private static final String TAG = "SslAsyncHttpServer";
private SSLEngine mSSLEngine
@Override
public void listenSecure(final int port, final SSLContext sslContext) {
AsyncServer.getDefault().listen(null, port, new ListenCallback() {
@Override
public void onAccepted(AsyncSocket socket) {
mSSLEngine = sslContext.createSSLEngine();
mSSLEngine.setNeedClientAuth(true);
AsyncSSLSocketWrapper.handshake(socket, null, port, mSSLEngine, null, null, false,
new AsyncSSLSocketWrapper.HandshakeCallback() {
@Override
public void onHandshakeCompleted(Exception e, AsyncSSLSocket socket) {
if (socket != null)
getListenCallback().onAccepted(socket);
}
});
}
@Override
public void onListening(AsyncServerSocket socket) {
getListenCallback().onListening(socket);
}
@Override
public void onCompleted(Exception ex) {
getListenCallback().onCompleted(ex);
}
});
}
}
使用認證鏈做認證
在生產(chǎn)環(huán)境中 對證書的校驗更為嚴格，通常采用證書鏈的方式和措。還是上面的code, 采用證書鏈的方式以后. handshake 失敗庄呈。
04-27 08:43:33.093 6881-6903/com.louie.certtest W/System.err: javax.net.ssl.SSLHandshakeException: Handshake failed
04-27 08:43:33.093 6881-6903/com.louie.certtest W/System.err: at com.android.org.conscrypt.OpenSSLEngineImpl.unwrap(OpenSSLEngineImpl.java:441)
04-27 08:43:33.093 6881-6903/com.louie.certtest W/System.err: at javax.net.ssl.SSLEngine.unwrap(SSLEngine.java:1270)
04-27 08:43:33.093 6881-6903/com.louie.certtest W/System.err: at com.koushikdutta.async.AsyncSSLSocketWrapper$5.onDataAvailable(AsyncSSLSocketWrapper.java:194)
04-27 08:43:33.093 6881-6903/com.louie.certtest W/System.err: at com.koushikdutta.async.Util.emitAllData(Util.java:23)
04-27 08:43:33.093 6881-6903/com.louie.certtest W/System.err: at com.koushikdutta.async.AsyncNetworkSocket.onReadable(AsyncNetworkSocket.java:152)
04-27 08:43:33.093 6881-6903/com.louie.certtest W/System.err: at com.koushikdutta.async.AsyncServer.runLoop(AsyncServer.java:821)
04-27 08:43:33.093 6881-6903/com.louie.certtest W/System.err: at com.koushikdutta.async.AsyncServer.run(AsyncServer.java:658)
04-27 08:43:33.093 6881-6903/com.louie.certtest W/System.err: at com.koushikdutta.async.AsyncServer.access$800(AsyncServer.java:44)
04-27 08:43:33.093 6881-6903/com.louie.certtest W/System.err: at com.koushikdutta.async.AsyncServer$14.run(AsyncServer.java:600)
04-27 08:43:33.094 6881-6903/com.louie.certtest W/System.err: Caused by: javax.net.ssl.SSLProtocolException: SSL handshake terminated: ssl=0xb31d4fc0: Failure in SSL library, usually a protocol error
04-27 08:43:33.094 6881-6903/com.louie.certtest W/System.err: error:100000c0:SSL routines:OPENSSL_internal:PEER_DID_NOT_RETURN_A_CERTIFICATE (external/boringssl/src/ssl/s3_srvr.c:1945 0xa3b68196:0x00000000)
04-27 08:43:33.094 6881-6903/com.louie.certtest W/System.err: at com.android.org.conscrypt.NativeCrypto.SSL_do_handshake_bio(Native Method)
04-27 08:43:33.094 6881-6903/com.louie.certtest W/System.err: at com.android.org.conscrypt.OpenSSLEngineImpl.unwrap(OpenSSLEngineImpl.java:426)
04-27 08:43:33.094 6881-6903/com.louie.certtest W/System.err: ... 8 more
wireshark 抓包后發(fā)現(xiàn)，服務端發(fā)送了 TCP 的FIN派阱，查看整個握手過程诬留，服務端發(fā)送 Certificate Request 后，客戶端也發(fā)送了 "Certificate"贫母，但是服務端隨后就發(fā)送了 Fin文兑。又是一個讓人頭疼的問題。從源碼來看腺劣，確實是服務端 調(diào)用了close.
4 0.007445 127.0.0.1 127.0.0.1 TLSv1.2 205 Client Hello
6 0.022138 127.0.0.1 127.0.0.1 TLSv1.2 1652 Server Hello, Certificate, Server Key Exchange, Certificate Request, Server Hello Done
8 0.029033 127.0.0.1 127.0.0.1 TLSv1.2 204 Certificate, Client Key Exchange, Change Cipher Spec, Hello Request, Hello Request
9 0.031817 127.0.0.1 127.0.0.1 TCP 66 6666→51878 [FIN, ACK] Seq=1587 Ack=278 Win=131008 Len=0 TSval=1856446 TSecr=1856446
查到了 ssl 握手的 RFC 文檔
7.4.6. Client certificate
When this message will be sent:
This is the first message the client can send after receiving a
server hello done message. This message is only sent if the
server requests a certificate. If no suitable certificate is
available, the client should send a certificate message
containing no certificates. If client authentication is required
by the server for the handshake to continue, it may respond with
a fatal handshake failure alert. Client certificates are sent
using the Certificate structure defined in Section 7.4.2.
然后再看 在wireshark 中看客戶端回的 Certificate 字段绿贞，長度居然為0.
想看下完整的ssl 握手過程，但是Android上并沒有SSL 握手的詳細日志橘原。
使用hugo
stackoverflow 上有一篇帖子清奇：
Client Certificate not working from Android - How to debug?
關(guān)于hugo 的詳細使用參考
hugo
服務端發(fā)送證書
04-27 04:05:02.025 3682-3699/com.louie.certtest V/SslX509KeyManager: ? chooseServerAlias(s="EC", principals=null, socket=null) [Thread:"AsyncServer"]
04-27 04:05:02.025 3682-3699/com.louie.certtest V/SslX509KeyManager: ? chooseServerAlias [0ms] = null
04-27 04:05:02.026 3682-3699/com.louie.certtest V/SslX509KeyManager: ? chooseServerAlias(s="RSA", principals=null, socket=null) [Thread:"AsyncServer"]
04-27 04:05:02.026 3682-3699/com.louie.certtest V/SslX509KeyManager: ? chooseServerAlias [0ms] = "1"
04-27 04:05:02.026 3682-3699/com.louie.certtest V/SslX509KeyManager: ? getPrivateKey(s="1") [Thread:"AsyncServer"]
04-27 04:05:02.026 3682-3699/com.louie.certtest V/SslX509KeyManager: ? getPrivateKey [0ms] = RSA Private CRT Key
- 從日志上看籍铁， 第 1 2 3 4 行是服務端需要發(fā)送 Certificate, 在KeyStore 中選擇和是的證書Alias
- 5 6 行根據(jù)選擇的Alias 獲取PrivateKey.
04-27 04:05:02.026 3682-3699/com.louie.certtest V/SslX509KeyManager: ? getCertificateChain(s="1") [Thread:"AsyncServer"]
04-27 04:05:02.030 3682-3699/com.louie.certtest V/SslX509KeyManager: ? getCertificateChain [0ms] = [Certificate:
Data:
Version: 3 (0x2)
Serial Number:
21:dd:e7:2c:8c:95:d9:f1
Signature Algorithm: sha256WithRSAEncryption
Issuer: CN=XXX_Web_test, O=XXX, C=US
Validity
Not Before: Mar 26 14:38:49 2018 GMT
Not After : Jan 4 20:48:34 2037 GMT
Subject: CN=ae86.XXXXXXX-local.com
- 接下來的日志表示找到服務端的證書，服務端的證書會發(fā)送給客戶端趾断。
服務端發(fā)送 Certificate Request
服務端首先根據(jù)KeyStore 中的證書鏈 找出客戶端需要發(fā)送證書的issure. 從日志上看是一個 Intermediate CA:
04-27 04:05:02.030 3682-3699/com.louie.certtest V/SslX509TrustManager: ? getAcceptedIssuers() [Thread:"AsyncServer"]
04-27 04:05:02.043 3682-3699/com.louie.certtest V/SslX509TrustManager: ? getAcceptedIssuers [0ms] = [Certificate:
Data:
Version: 3 (0x2)
Serial Number:
74:0e:7c:31:e5:5e:2c:9d
Signature Algorithm: sha256WithRSAEncryption
Issuer: CN=XXX Root CA, O=XXX, C=US
Validity
Not Before: Jan 4 20:48:34 2017 GMT
Not After : Jan 4 20:48:34 2037 GMT
Subject: CN=XXX Intermediate CA, O=XXX, C=US
客戶端校驗
客戶端校驗服務端證書：
04-27 08:35:41.909 6640-6660/com.louie.certtest V/SslX509TrustManager: ? checkServerTrusted(chain=[Certificate:
客戶端發(fā)送證書
客戶端根據(jù)服務端發(fā)送的 Certificate Request 選擇合適的證書
從日志上可以看出：
服務端發(fā)送的證書 Subject 為:
- C=US, O=XXX, CN=XXX Intermediate CA,
- C=US, O=XXX, CN=XXX Root CA,
- C=US, O=XXX, CN=XXX Root CA]
客戶端證書的Issure為:
- C=US, O=XXX, CN=XXX_Vehicle_test
客戶端沒有找到合適的證書拒名，所以發(fā)送的證書長度為0。
04-27 08:35:41.914 6640-6660/com.louie.certtest V/SslX509KeyManager: ? chooseClientAlias(strings=["EC", "RSA"], principals=[C=US, O=XXX, CN=XXX Intermediate CA, C=US, O=XXX, CN=XXX Root CA, C=US, O=XXX, CN=XXX Root CA], socket=null) [Thread:"AsyncServer"]
04-27 08:35:41.914 6640-6660/com.louie.certtest V/KeyManagerImpl: ? printVar(name="issuersList", object=[C=US, O=XXX, CN=XXX Intermediate CA, C=US, O=XXX, CN=XXX Root CA, C=US, O=XXX, CN=XXX Root CA]) [Thread:"AsyncServer"]
04-27 08:35:41.915 6640-6660/com.louie.certtest V/KeyManagerImpl: ? printVar [0ms]
04-27 08:35:41.915 6640-6660/com.louie.certtest V/KeyManagerImpl: ? printVar(name="issuerFromChain", object=C=US, O=XXX, CN=XXX_Vehicle_test) [Thread:"AsyncServer"]
04-27 08:35:41.915 6640-6660/com.louie.certtest V/KeyManagerImpl: ? printVar [0ms]
04-27 08:35:41.915 6640-6660/com.louie.certtest V/KeyManagerImpl: ? printVar(name="alias", object="1") [Thread:"AsyncServer"]
04-27 08:35:41.915 6640-6660/com.louie.certtest V/KeyManagerImpl: ? printVar [0ms]
04-27 08:35:41.915 6640-6660/com.louie.certtest V/SslX509KeyManager: ? chooseClientAlias [0ms] = null
concrypt 補丁
找到原因后芋酌，看下服務端為發(fā)送的 Certificate Request 為什么不正確增显。
通過debug ， 服務端調(diào)用 在 SSLParametersImpl.java 中的 setCertificateValidation 調(diào)用 trustManager.getAcceptedIssuers()隔嫡。
然后調(diào)用 encodeIssuerX509Principals 函數(shù)甸怕。
void setCertificateValidation(long sslNativePointer) throws IOException {
if(!this.client_mode) {
boolean certRequested;
。腮恩。梢杭。。秸滴。武契。
if(certRequested) {
X509TrustManager trustManager = this.getX509TrustManager();
X509Certificate[] issuers = trustManager.getAcceptedIssuers();
if(issuers != null && issuers.length != 0) {
byte[][] issuersBytes;
try {
issuersBytes = encodeIssuerX509Principals(issuers);
} catch (CertificateEncodingException var8) {
throw new IOException("Problem encoding principals", var8);
}
NativeCrypto.SSL_set_client_CA_list(sslNativePointer, issuersBytes);
}
}
}
}
在encodeIssuerX509Principals 中調(diào)用getIssuerX500Principal 獲取證書的Issuere.如果我們有三個證書組成認證鏈:
- [subject=RootCA, issure=RootCA],
- [subject=SecondCA, issure=RootCA]
- [subject=ThirdCA, issure=SecondCA]
getIssuerX500Principal 獲取到的是
[RootCA, RootCA, SecondCA]
正確的做法為:getSubjectX500Principal
這樣獲取到的為:
[RootCA, SecondCA, ThirdCA]
static byte[][] encodeIssuerX509Principals(X509Certificate[] certificates) throws CertificateEncodingException {
byte[][] principalBytes = new byte[certificates.length][];
for(int i = 0; i < certificates.length; ++i) {
principalBytes[i] = certificates[i].getIssuerX500Principal().getEncoded();
}
return principalBytes;
}
Two way ssl uses trustchain, android as a service 提交
在Android 8.0 上測試，發(fā)現(xiàn)還是有這個問題荡含。Androd作為客戶端的場景比較常見咒唆，
作為服務端比較少見。向google 提交了一個補妒鸵骸：
Two way ssl uses trustchain, android as a service
https 握手過程中的KeyManager 和TrustManager 調(diào)用
