如何从 pem 文件加载公共证书?-Java问题

How to load public certificate from pem file?(如何从 pem 文件加载公共证书?)

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问题描述

我试图从下面的文件中提取 RES 公钥

I was trying to extract RES public key from the file below

这是我做的代码..

public static PublicKey loadPublicKeyFromFile(File publicKeyFile) throws Exception {

    FileReader file = new FileReader(publicKeyFile);
    PemReader reader = new PemReader(file);
    X509EncodedKeySpec caKeySpec = new X509EncodedKeySpec(reader.readPemObject().getContent());
    KeyFactory kf = KeyFactory.getInstance("RSA");
    PublicKey caKey = kf.generatePublic(caKeySpec);
    return caKey;
}

但它抛出了

java.security.InvalidKeyException: IOException: ObjectIdentifier() -- 数据不是对象 ID

java.security.InvalidKeyException: IOException: ObjectIdentifier() -- data isn't an object ID

从文件中提取 RES 公钥的适当方法是什么..

What's the appropriate way to extract RES Public key from a file..

推荐答案

X.509 证书和 X509EncodedKeySpec 是完全不同的结构，尝试将证书解析为密钥是行不通的.Java 的 X509EncodedKeySpec 实际上是 X.509 中的 SubjectPublicKeyInfo 或更方便的等价物 PKIX 也链接自 Key，只是证书的一小部分.

An X.509 certificate and an X509EncodedKeySpec are quite different structures, and trying to parse a cert as a key won't work. Java's X509EncodedKeySpec is actually SubjectPublicKeyInfo from X.509 or equivalent and more convenient PKIX also linked from Key, which is only a small part of a certificate.

您需要做的是读取和解析证书，然后从证书中提取公钥.标准的 SunJCE CertificateFactory 可以做到(并且可以读取 PEM 或 DER 来启动)，如下所示:

What you need to do is read and parse the cert and then extract the pubkey from the cert. Standard SunJCE CertificateFactory can do it (and can read either PEM or DER to boot) like this:

CertificateFactory fact = CertificateFactory.getInstance("X.509");
FileInputStream is = new FileInputStream (args[0]);
X509Certificate cer = (X509Certificate) fact.generateCertificate(is);
PublicKey key = cer.getPublicKey();
is.close();
// add error handling as appropriate, try-with-resources is often good

如果你有 BouncyCastle，你可以以同样的方式使用它的提供者(只需添加第二个参数到 .getInstance 或设置默认提供者列表顺序)，或者你可以使用 PEMParser 和 JcaX509CertificateConverter —— 它有效地做同样的事情，通过 CertificateFactory 在内部运行数据.

If you have BouncyCastle you can use its provider the same way (just add a second argument to .getInstance or set the default provider list order), or you can use PEMParser with JcaX509CertificateConverter -- which effectively does the same thing, internally running the data through a CertificateFactory.

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