从终端实体获取根证书和中间证书

Question

我仍然是密码学的一个菜鸟我每天偶然发现简单的事情.而今天只是其中的一天.

我想用弹性城堡库验证java中的smime消息,我想我几乎把它想出来了,但此时的问题是构建PKIXparameters对象.比方说,我有一个具有以下结构的终端实体x509certificate:

root certificate
 +->intermediate certificate
    +->end-entity certificate

为了验证消息,我需要首先建立一个信任链,但我无法弄清楚如何从最终实体中提取根证书和中间证书.

我试图以root身份使用end-entity,但它不起作用:

InputStream isCert = GetFISCertificate();

List list = new ArrayList();
X509Certificate rootCert = (X509Certificate) certificateFactory.generateCertificate(isCert);
list.add(rootCert);
CollectionCertStoreParameters params = new CollectionCertStoreParameters(list);
CertStore store = CertStore.getInstance("Collection", params, BC);

//create cert path
List certChain = new ArrayList();
certChain.add(rootCert);
CertPath certPath = certificateFactory.generateCertPath(certChain);
Set trust = Collections.singleton(new TrustAnchor(rootCert, null));

//validation
CertPathValidator certPathValidator = CertPathValidator.getInstance("PKIX", BC);
PKIXParameters pKIXParameters = new PKIXParameters(trust);
pKIXParameters.addCertStore(store);
pKIXParameters.setDate(new Date());
try {
CertPathValidatorResult result = certPathValidator.validate(certPath, pKIXParameters);
System.out.println("certificate path validated");

} catch (CertPathValidatorException e) {
System.out.println("validation failed on certificate number " + e.getIndex() + ", details: " + e.getMessage());
}

得到这个例外:

validation failed on certificate number -1, details: Trust anchor for certification path not found.

顺便说一句,我可以只使用最终实体证书来验证消息,就好像它是自签名证书一样吗？

Answer 1

我已经使用BouncyCastle 1.56进行此测试.

从终端实体获取颁发者证书的一种方法是查找授权信息访问扩展.

此扩展可能存在(它不是强制性的)并且可能包含获取颁发者证书的URL(发行者是"当前"以上的证书,因此最终实体的发行者是中间人,中间人的发行者是根证书).

您可以使用BouncyCastle获取此扩展值:

import java.security.cert.X509Certificate;
import org.bouncycastle.asn1.x509.AccessDescription;
import org.bouncycastle.asn1.x509.AuthorityInformationAccess;
import org.bouncycastle.asn1.x509.Extension;
import org.bouncycastle.asn1.x509.GeneralName;
import org.bouncycastle.asn1.x509.X509ObjectIdentifiers;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.x509.extension.X509ExtensionUtil;

X509Certificate cert = // end entity certificate

// get Authority Information Access extension (will be null if extension is not present)
byte[] extVal = cert.getExtensionValue(Extension.authorityInfoAccess.getId());
AuthorityInformationAccess aia = AuthorityInformationAccess.getInstance(X509ExtensionUtil.fromExtensionValue(extVal));

// check if there is a URL to issuer's certificate
AccessDescription[] descriptions = aia.getAccessDescriptions();
for (AccessDescription ad : descriptions) {
    // check if it's a URL to issuer's certificate
    if (ad.getAccessMethod().equals(X509ObjectIdentifiers.id_ad_caIssuers)) {
        GeneralName location = ad.getAccessLocation();
        if (location.getTagNo() == GeneralName.uniformResourceIdentifier) {
            String issuerUrl = location.getName().toString();
            // http URL to issuer (test in your browser to see if it's a valid certificate)
            // you can use java.net.URL.openStream() to create a InputStream and create
            // the certificate with your CertificateFactory
            URL url = new URL(issuerUrl);
            X509Certificate issuer = (X509Certificate) certificateFactory.generateCertificate(url.openStream());
        }
    }
}

因此,您可以将此代码与最终实体证书一起使用以获取中间体.然后再用中间体来获取根.

然后你将根添加到你的TrustAnchor,验证应该工作.

注意:但正如我所说,此扩展名不是强制性的,可能不存在.在这种情况下,getExtensionValue将返回null,我知道的唯一选择是在谷歌搜索证书并下载它们(这些证书链通常是公开的,不难找到)