问题描述
如何创建可用于 SSH 的 OpenSSH ED25519 私钥?目标是为 OpenSSH 客户端提供与 .ssh/id_ed25519
中相同格式的密钥文件。
import org.bouncycastle.asn1.x9.X9ECParameters;
import org.bouncycastle.crypto.ec.CustomNamedCurves;
import org.bouncycastle.crypto.params.asymmetricKeyParameter;
import org.bouncycastle.crypto.util.OpenSSHPrivateKeyUtil;
import org.bouncycastle.crypto.util.PrivateKeyFactory;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.jce.spec.ECParameterSpec;
import org.bouncycastle.util.io.pem.PemObject;
import org.bouncycastle.util.io.pem.PemWriter;
import java.io.StringWriter;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.Security;
public class Test {
static {
Security.removeProvider("BC");provider
Security.insertProviderAt(new BouncyCastleProvider(),1);
}
public static String createCurve25519PEM() {
try {
X9ECParameters curveParams = CustomNamedCurves.getByName("Curve25519");
ECParameterSpec ecSpec = new ECParameterSpec(curveParams.getCurve(),curveParams.getG(),curveParams.getN(),curveParams.getH(),curveParams.getSeed());
KeyPairGenerator kpg = KeyPairGenerator.getInstance("EC",new BouncyCastleProvider());
kpg.initialize(ecSpec);
KeyPair keypair = kpg.generateKeyPair();
asymmetricKeyParameter akp = PrivateKeyFactory.createKey(keypair.getPrivate().getEncoded());
byte[] content = OpenSSHPrivateKeyUtil.encodePrivateKey(akp);
PemObject o = new PemObject("OPENSSH PRIVATE KEY",content);
StringWriter sw = new StringWriter();
PemWriter w = new PemWriter(sw);
w.writeObject(o);
w.close();
Log.d("createCurve25519PEM","key: " + sw.toString());
return sw.toString();
} catch (Exception e) {
Log.d("createCurve25519PEM",e.toString());
}
return null;
}
}
输出如下:
-----BEGIN OPENSSH PRIVATE KEY-----
MIIBTwIBAQQgA8BjYjSjUgM4PahSZQx3i9DWcEdGiGnBoA0tXCUENzKggeEwgd4C
AQEwKwYHKoZIzj0BAQIgf////////////////////////////////////////+0w
RAQgKqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqmEkUoUQEIHtCXtCXtCXtCXtC
XtCXtCXtCXtCXtCXtCYLXpx3EMhkBEEEKqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq
qqqqqqqtJFogrhmhuKCGtOAe3Sx3SNFMkj1Nfm18YbIp6cWifs7T2QIgEAAAAAAA
AAAAAAAAAAAAABTe+d6i95zWWBJjGlz10+0CAQihRANCAARl0Kc+dO0Er1dpu6mh
/lZmTw3/DMKpltzjosX2u7hQswV+U9o0WOYFd1JOqsGdkLfYuGmdZzWdk74dvV1O
+w5T
-----END OPENSSH PRIVATE KEY-----
.. 但不幸的是不被 SSH 接受。
解决方法
以这种方式使用“Curve25519”以X9使用的简短的Weierstrass形式提供给您;这不适用于 Ed25519,它被定义为使用扭曲的爱德华形式。此外,通过 JCA 不幸的 ECParameterSpec
类填充它给出了原始的 X9 定义的“显式”表示,该表示现在已经过时,甚至几乎从未用于确实使用 Weierstrass 曲线的算法。因此,您创建的数据对于 PEM 类型 OPENSSH PRIVATE KEY 不正确;它对 OpenSSL 的“传统”PEM 类型 EC PRIVATE KEY 有效,并且 OpenSSL(它仍然支持但不喜欢“param_enc 显式”)能够使用 that 类型,尽管它不能用于与其他任何东西互操作。
您需要将 JCA 与 算法“ED25519”(不是“EC”“ECDSA”“ECDH”“ECMQV”等都是 X9/SECG)一起使用,如下所示:
KeyPair pair = KeyPairGenerator.getInstance("ED25519","BC") .generateKeyPair();
AsymmetricKeyParameter bprv = PrivateKeyFactory.createKey(pair.getPrivate().getEncoded());
// then proceed as you already have; I have simplified for my test environment
byte[] oprv = OpenSSHPrivateKeyUtil.encodePrivateKey(bprv);
PemWriter w = new PemWriter(new OutputStreamWriter(System.out));
w.writeObject(new PemObject("OPENSSH PRIVATE KEY",oprv)); w.close();
// BTW if you pass an actual Provider to .getInstance (rather than a String,or letting it search)
// you don't actually need to have put that Provider in the searchlist
// Also in Java 15 up you can use the SunEC provider (normally searched by default)
// but since you still need other Bouncy pieces why bother
或者因为您已经依赖 Bouncy 使用轻量级 API:
AsymmetricCipherKeyPairGenerator gen = new Ed25519KeyPairGenerator();
gen.init(new KeyGenerationParameters(new SecureRandom(),255));
AsymmetricKeyParameter bprv = gen.generateKeyPair().getPrivate();
// ditto