在 AWS 上导入密钥对之前，如何通过 Java 验证 OpenSSH 公钥格式？答案

【问题标题】：How to Valid OpenSSH public key format by Java before importing key pair on AWS?在 AWS 上导入密钥对之前，如何通过 Java 验证 OpenSSH 公钥格式？
【发布时间】：2021-05-05 02:37:12
【问题描述】：

我的任务是使用 Java 验证 AWS 支持的 OpenSSH 公钥（RSA 密钥）。

例如，我有两种 RSA 格式，如何通过 Java 验证它们？

    ---- BEGIN PUBLIC KEY ----
Comment: "4096-bit RSA, converted from OpenSSH by dhopson@VMUbuntu-DSH"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---- END PUBLIC KEY ----

    ssh-rsa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 dhopson@VMUbuntu-DSH

【问题讨论】：

这些密钥是相同的并且是 ssh 格式。带有“-----BEGIN PUBLIC KEY----”的密钥预计将采用不同的格式，即 RFC 5280 中指定的 SubjectPublicKeyInfo ASN.1 结构。不清楚您所说的“有效”或“验证”是什么意思" 在这种情况下。

标签： java ssh rsa ssh-keys openssh

【解决方案1】：

假设您从开头删除“ssh-rsa”位并从末尾删除注释（“dhopson@VMUbuntu-DSH”），这将解码 OpenSSH 格式的密钥：

import java.util.Base64; 
import java.nio.ByteBuffer;
import java.util.Arrays;
import java.lang.UnsupportedOperationException;
import javax.xml.bind.DatatypeConverter;
import java.math.BigInteger;

public class Demo
{
    public static void main(String[] args)
    {
        String key = "AAAAB3NzaC1yc2EAAAABIwAAAgEAwrr66r8n6B8Y0zMF3dOpXEapIQD9DiYQ6D6/zwor9o" +
"39jSkHNiMMER/GETBbzP83LOcekm02aRjo55ArO7gPPVvCXbrirJu9pkm4AC4BBre5xSLS" +
"7soyzwbigFruM8G63jSXqpHqJ/ooi168sKMC2b0Ncsi+JlTfNYlDXJVLKEeZgZOInQyMmt" +
"isaDTUQWTIv1snAizf4iIYENuAkGYGNCL77u5Y5VOu5eQipvFajTnps9QvUx/zdSFYn9e2" +
"sulWM3Bxc/S4IJ67JWHVRpfJxGi3hinRBH8WQdXuUwdJJTiJHKPyYrrM7Q6Xq4TOMFtcRu" +
"LDC6u3BXM1L0gBvHPNOnD5l2Lp5EjUkQ9CBf2j4A4gfH+iWQZyk08esAG/iwArAVxkl368" +
"+dkbMWOXL8BN4x5zYgdzoeypQZZ2RKH780MCTSo4WQ19DP8pw+9q3bSFC9H3xYAxrKAJNW" +
"jeTUJOTrTe+mWXXU770gYyQTxa2ycnYrlZucn1S3vsvn6eq7NZZ8NRbyv1n15Ocg+nHK4f" +
"uKOrwPhU3NbKQwtjb0Wsxx1gAmQqIOLTpAdsrAauPxC7TPYA5qQVCphvimKuhQM/1gMV22" +
"5JrnjspVlthCzuFYUjXOKC3wxz6FFEtwnXu3uC5bVVkmkNadJmD21gD23yk4BraGXVYpRM" +
"IB+X+OTUUI8=";
                
        byte[] keyBytes = Base64.getDecoder().decode(key);
        int offset = 4;
        int length;
        BigInteger publicExponent, modulus;

        length = ByteBuffer.wrap(Arrays.copyOfRange(keyBytes, 0, 4)).getInt();

        byte[] keyType = Arrays.copyOfRange(keyBytes, 4, 4 + length);
        if (!Arrays.equals(keyType, "ssh-rsa".getBytes())) {
            throw new UnsupportedOperationException(
                DatatypeConverter.printHexBinary("ssh-rsa".getBytes()) +
                " key expected - got " +
                DatatypeConverter.printHexBinary(keyType)
            );
        }
        offset+= length;
        length = ByteBuffer.wrap(Arrays.copyOfRange(keyBytes, offset, offset + 4)).getInt();
        offset+= 4;
        publicExponent = new BigInteger(Arrays.copyOfRange(keyBytes, offset, offset + length));
        offset+= length;
        length = ByteBuffer.wrap(Arrays.copyOfRange(keyBytes, offset, offset + 4)).getInt();
        offset+= 4;
        modulus = new BigInteger(Arrays.copyOfRange(keyBytes, offset, offset + length));

        System.out.println(publicExponent.toString());
        System.out.println(modulus.toString());
    }
}

它解码 OpenSSH 密钥这一事实意味着它应该足以验证它。

如果解码在任何时候失败，都会抛出异常。如果没有足够的二进制数据，就像Arrays.copyOfRange() 会抛出ArrayIndexOutOfBoundsException。

即。如果没有抛出异常，则密钥是好的。如果抛出异常，则密钥是错误的。

【讨论】：