我需要通过java以编程方式获取安全网站的公钥。我还阅读了this，this，this和this以及其他人。 但我还没有找到通过java获得它的解决方案。
EDIT :::
根据Zielu的回答，我写了以下程序：
import java.security.PublicKey;
import java.security.cert.Certificate;
import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.SSLSocket;
import javax.net.ssl.SSLSocketFactory;
public class RetrievePublicKey {
private static PublicKey getKey(String hostname, int port) throws Exception {
SSLSocketFactory factory = HttpsURLConnection.getDefaultSSLSocketFactory();
SSLSocket socket = (SSLSocket) factory.createSocket(hostname, port);
socket.startHandshake();
Certificate[] certs = socket.getSession().getPeerCertificates();
Certificate cert = certs[0];
PublicKey key = cert.getPublicKey();
System.out.println(key);
return key;
}
public static void main(String[] args) throws Exception {
System.out.println(getKey("bctcl-parasuram.bctchn.local", 8443));
}
}
但是当我运行它时，我得到以下异常：
Exception in thread "main" javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
at sun.security.ssl.Alerts.getSSLException(Alerts.java:192)
at sun.security.ssl.SSLSocketImpl.fatal(SSLSocketImpl.java:1937)
at sun.security.ssl.Handshaker.fatalSE(Handshaker.java:302)
at sun.security.ssl.Handshaker.fatalSE(Handshaker.java:296)
at sun.security.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1478)
at sun.security.ssl.ClientHandshaker.processMessage(ClientHandshaker.java:212)
at sun.security.ssl.Handshaker.processLoop(Handshaker.java:957)
at sun.security.ssl.Handshaker.process_record(Handshaker.java:892)
at sun.security.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:1050)
at sun.security.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1363)
at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1391)
at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1375)
at RetrievePublicKey.getKey(RetrievePublicKey.java:22)
at RetrievePublicKey.main(RetrievePublicKey.java:30)
Caused by: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:387)
at sun.security.validator.PKIXValidator.engineValidate(PKIXValidator.java:292)
at sun.security.validator.Validator.validate(Validator.java:260)
at sun.security.ssl.X509TrustManagerImpl.validate(X509TrustManagerImpl.java:324)
at sun.security.ssl.X509TrustManagerImpl.checkTrusted(X509TrustManagerImpl.java:229)
at sun.security.ssl.X509TrustManagerImpl.checkServerTrusted(X509TrustManagerImpl.java:124)
at sun.security.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1460)
... 9 more
Caused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
at sun.security.provider.certpath.SunCertPathBuilder.build(SunCertPathBuilder.java:145)
at sun.security.provider.certpath.SunCertPathBuilder.engineBuild(SunCertPathBuilder.java:131)
at java.security.cert.CertPathBuilder.build(CertPathBuilder.java:280)
at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:382)
... 15 more
答案 0 :(得分：6)
您可以使用SSLSocket获取证书及其公钥：
import javax.net.ssl.SSLSocket;
import javax.net.ssl.SSLSocketFactory;
import java.security.cert.Certificate;
...
String hostname = "your.host";
SSLSocketFactory factory = HttpsURLConnection.getDefaultSSLSocketFactory();
SSLSocket socket = (SSLSocket) factory.createSocket(hostname, 443);
socket.startHandshake();
Certificate[] certs = socket.getSession().getPeerCertificates();
Certificate cert = certs[0];
PublicKey key = cert.getPublicKey();
仅当证书有效（不是自签名或由未知权限签名）时才有效。对于自签名证书，您可以定义自己的TrustManager，它将信任所有内容。见Allowing Java to use an untrusted certificate for SSL/HTTPS connection
但是如果可以的话，应该避免，因为留下的这种代码会在以后产生安全问题。
答案 1 :(得分：0)
当应用程序识别服务器时获取证书可以使用Zielu的答案来完成。但是，如果服务器无法识别（例如，自签名或由未包含在JVM密钥库中的未知根权限签名），则可以使用InstallCert以编程方式检索服务器的证书。缩写版如下： [警告：正如其他人所述，只有在您了解并信任证书所有者的情况下才能以这种方式使用不受信任的证书，否则会产生安全风险。]
import javax.net.ssl.*;
import java.io.*;
import java.security.*;
import java.security.cert.*;
public class FetchCert {
public static void main(String[] args) throws Exception {
//REPLACE THIS WITH YOUR TARGET HOST NAME
String hostname = "example.com";
SSLSocketFactory factory = HttpsURLConnection.getDefaultSSLSocketFactory();
SSLSocket socket = (SSLSocket) factory.createSocket(hostname, 443);
try {
socket.startHandshake();
socket.close();
System.out.println("No errors, certificate is already trusted");
return;
} catch (SSLException e) {
System.out.println("cert likely not found in keystore, will pull cert...");
}
KeyStore ks = KeyStore.getInstance(KeyStore.getDefaultType());
char[] password = "changeit".toCharArray();
ks.load(null, password);
SSLContext context = SSLContext.getInstance("TLS");
TrustManagerFactory tmf =
TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
tmf.init(ks);
X509TrustManager defaultTrustManager = (X509TrustManager) tmf.getTrustManagers()[0];
SavingTrustManager tm = new SavingTrustManager(defaultTrustManager);
context.init(null, new TrustManager[]{tm}, null);
factory = context.getSocketFactory();
socket = (SSLSocket) factory.createSocket(hostname, 443);
try {
socket.startHandshake();
} catch (SSLException e) {
//we should get to here
}
X509Certificate[] chain = tm.chain;
if (chain == null) {
System.out.println("Could not obtain server certificate chain");
return;
}
X509Certificate cert = chain[0];
String alias = hostname;
ks.setCertificateEntry(alias, cert);
System.out.println("saving file jssecacerts to working dir");
System.out.println("copy this file to your jre/lib/security folder");
FileOutputStream fos = new FileOutputStream("jssecacerts");
ks.store(fos, password);
fos.close();
}
private static class SavingTrustManager implements X509TrustManager {
private final X509TrustManager tm;
private X509Certificate[] chain;
SavingTrustManager(X509TrustManager tm) {
this.tm = tm;
}
public X509Certificate[] getAcceptedIssuers() {
return new X509Certificate[0];
}
public void checkClientTrusted(X509Certificate[] chain, String authType)
throws CertificateException {
throw new UnsupportedOperationException();
}
public void checkServerTrusted(X509Certificate[] chain, String authType)
throws CertificateException {
this.chain = chain;
tm.checkServerTrusted(chain, authType);
}
}
}