在Servlet中读取客户端证书

如何将证书（.cer）从客户端发送到服务器？

客户端证书（.cer，.crt，.pem）及其对应的私钥（.key）应首先包装到PKCS＃12（.p12，.pfx）或JKS（.jks）容器中（密钥库）。您还应该将服务器的CA证书打包为JKS（信任库）。

使用HttpClient 3.x的示例：

HttpClient client = new HttpClient();
// truststore
KeyStore trustStore = KeyStore.getInstance("JKS", "SUN");
trustStore.load(TestSupertype.class.getResourceAsStream("/client-truststore.jks"), "amber%".toCharArray());
String alg = KeyManagerFactory.getDefaultAlgorithm();
TrustManagerFactory fac = TrustManagerFactory.getInstance(alg);
fac.init(trustStore);
// keystore
KeyStore keystore = KeyStore.getInstance("PKCS12", "SunJSSE");
keystore.load(X509Test.class.getResourceAsStream("/etomcat_client.p12"), "etomcat".toCharArray());
String keyAlg = KeyManagerFactory.getDefaultAlgorithm();
KeyManagerFactory keyFac = KeyManagerFactory.getInstance(keyAlg);
keyFac.init(keystore, "etomcat".toCharArray());
// context
SSLContext ctx = SSLContext.getInstance("TLS", "SunJSSE");
ctx.init(keyFac.getKeyManagers(), fac.getTrustManagers(), new SecureRandom());
SslContextedSecureProtocolSocketFactory secureProtocolSocketFactory = new SslContextedSecureProtocolSocketFactory(ctx);
Protocol.registerProtocol("https", new Protocol("https", (ProtocolSocketFactory) secureProtocolSocketFactory, 8443));
// test get
HttpMethod get = new GetMethod("https://127.0.0.1:8443/etomcat_x509");
client.executeMethod(get);
// get response body and do what you need with it
byte[] responseBody = get.getResponseBody();

您可以在该项目中找到工作示例，请参见X509Test课程。

使用HttpClient 4.x时，配置和语法会稍有不同：

HttpClient httpclient = new DefaultHttpClient();
// truststore
KeyStore ts = KeyStore.getInstance("JKS", "SUN");
ts.load(PostService.class.getResourceAsStream("/truststore.jks"), "amber%".toCharArray());
// if you remove me, you've got 'javax.net.ssl.SSLPeerUnverifiedException: peer not authenticated' on missing truststore
if(0 == ts.size()) throw new IOException("Error loading truststore");
// tmf
TrustManagerFactory tmf = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
tmf.init(ts);
// keystore
KeyStore ks = KeyStore.getInstance("PKCS12", "SunJSSE");
ks.load(PostService.class.getResourceAsStream("/" + certName), certPwd.toCharArray());
// if you remove me, you've got 'javax.net.ssl.SSLPeerUnverifiedException: peer not authenticated' on missing keystore
if(0 == ks.size()) throw new IOException("Error loading keystore");
// kmf
KeyManagerFactory kmf = KeyManagerFactory.getInstance(KeyManagerFactory.getDefaultAlgorithm());
kmf.init(ks, certPwd.toCharArray());
// SSL
SSLContext ctx = SSLContext.getInstance("TLS");
ctx.init(kmf.getKeyManagers(), tmf.getTrustManagers(), null);
// socket
SSLSocketFactory socketFactory = new SSLSocketFactory(ctx, SSLSocketFactory.ALLOW_ALL_HOSTNAME_VERIFIER);
Scheme sch = new Scheme("https", 8443, socketFactory);
httpclient.getConnectionManager().getSchemeRegistry().register(sch);
// request
HttpMethod get = new GetMethod("https://localhost:8443/foo");
client.executeMethod(get);
IOUtils.copy(get.getResponseBodyAsStream(), System.out);

如何在服务器中接收证书并提取其公钥？

您的服务器必须配置为要求X.509客户端证书身份验证。然后，在SSL握手期间，servlet容器将接收证书，对照trustore进行检查，并将其作为请求属性提供给应用程序。通常，对于单个证书，您可以在servlet环境中使用此方法来提取证书：

protected X509Certificate extractCertificate(HttpServletRequest req) {
    X509Certificate[] certs = (X509Certificate[]) req.getAttribute("javax.servlet.request.X509Certificate");
    if (null != certs && certs.length > 0) {
        return certs[0];
    }
    throw new RuntimeException("No X.509 client certificate found in request");
}