如何使用java 7将ssh-rsa公钥转换为PEM PKCS＃1公钥格式

My Public in ssh-rsa is:

我在ssh-rsa的公众是:

ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQClAxT5S/WuX04OXBt9R59WcL45OmaU3M5U063lfyja7ovqaVR7/2kHtLF/LoCQCXSZMny8RTCGDjoXD7G/tGsyHFDHCI//Y1VDLE06AlDzrlu69DQY91+6gkhGjH3SF6us5hXlihrbSFLfAlSdkEs8gwSrspVQyuaOf+39dnMddhEDYYg+z0ce82ta/n8xPBWCp60nDEDayNjOsRgzDJKSujNfngjQTL1x6qKJj8BW/P5lLJE1nbMm9BQD9G7glJk86qh1I/tJCnij6On0m6KcdzVz8cU3sBgNeB433kGjJtpxXXmJB6Vuu5IverhyfpiB4hP9WlKa/LSzW+ZIdvl/

I wanted to convert it to PKCS#1 below format

我想将它转换为PKCS#1格式

-----BEGIN RSA PUBLIC KEY----- MIIBCgKCAQEAoL7K8ijUPfkkpdiIMIoHxzTn+npLzJGHr7QO09Mnz8Q1xFfv9Arr 3Eg2R7LdTMJ+v2Rk3EDRGJEwK8cWv5Hvh7KXIdRqtw2ouxY6pK9RXfvaQ0CF2nI9 Y7VxASdOvnI8byzlw9SvR1eDjpzIh8/wtz3KcJK5aCRsAyH6ddvM4tPisQaKVBGN nCtPq94PspbpEYbNSQXTmnpO099P99oDXT+kpCaNrPvM5xWmUj0R7UwbmYYdNnVB UPFTKj+qVpp8TUTFUgk8noke7ABK6tncf8wmB8mPhgoKznZP5MaLZpB1f4gBeXst GNiLN4LwgRSM56eCEVqQHkVRuRrM9nODWQIDAQAB

----- BEGIN RSA公钥----- MIIBCgKCAQEAoL7K8ijUPfkkpdiIMIoHxzTn + npLzJGHr7QO09Mnz8Q1xFfv9Arr 3Eg2R7LdTMJ + v2Rk3EDRGJEwK8cWv5Hvh7KXIdRqtw2ouxY6pK9RXfvaQ0CF2nI9 Y7VxASdOvnI8byzlw9SvR1eDjpzIh8 / wtz3KcJK5aCRsAyH6ddvM4tPisQaKVBGN nCtPq94PspbpEYbNSQXTmnpO099P99oDXT + kpCaNrPvM5xWmUj0R7UwbmYYdNnVB UPFTKj + qVpp8TUTFUgk8noke7ABK6tncf8wmB8mPhgoKznZP5MaLZpB1f4gBeXst GNiLN4LwgRSM56eCEVqQHkVRuRrM9nODWQIDAQAB

-----END RSA PUBLIC KEY-----

----- END RSA PUBLIC KEY -----

Summary : I want to verify file by using above public key in java 7 as i am facing the invalid key format error for ssh-rsa public key kindly let me know what need to be done.

简介:我想通过在java 7中使用上面的公钥验证文件,因为我面对ssh-rsa公钥的无效密钥格式错误,请让我知道需要做什么。

please find below snippet:

请找下面的代码:

byte[] decoded;
        try {
        decoded = Base64.getDecoder().decode(publickeyStr);
        org.bouncycastle.asn1.pkcs.RSAPublicKey pkcs1PublicKey = org.bouncycastle.asn1.pkcs.RSAPublicKey.getInstance(decoded);
        BigInteger modulus = pkcs1PublicKey.getModulus();
        BigInteger publicExponent = pkcs1PublicKey.getPublicExponent();
        RSAPublicKeySpec keySpec = new RSAPublicKeySpec(modulus, publicExponent);
        KeyFactory kf;
        kf = KeyFactory.getInstance("RSA");
        PublicKey generatedPublic = kf.generatePublic(keySpec);
        System.out.printf("Modulus: %X%n", modulus);
        System.out.printf("Public exponent: %d ... 17? Why?%n", publicExponent);
        System.out.printf("See, Java class result: %s, is RSAPublicKey: %b%n", generatedPublic.getClass().getName(), generatedPublic instanceof RSAPublicKey);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

it is giving below exception:

它给出了以下例外情况:

java.lang.IllegalArgumentException: Illegal base64 character 2d
    at java.util.Base64$Decoder.decode0(Base64.java:714)
    at java.util.Base64$Decoder.decode(Base64.java:526)
    at java.util.Base64$Decoder.decode(Base64.java:549)
    at SignVerify.convertPublicPKCS1StrToPKCS8PublicKeyObj(SignVerify.java:136)
    at SignVerify.main(SignVerify.java:184)

1 个解决方案

#1

I do not find any tool or solutions in java that can do it. So, I read RFC 4253 for public key format description and RFC 4251 for mpint description. Important parts from RFC 4253. section 6.6

我在java中找不到任何可以做到的工具或解决方案。因此,我读取RFC 4253的公钥格式描述和RFC 4251的mpint描述。 RFC 4253的重要部分。第6.6节

 The "ssh-rsa" key format has the following specific encoding:

  string    "ssh-rsa"
  mpint     e
  mpint     n

Here the 'e' and 'n' parameters form the signature key blob.

And important part from RFC 4251

RFC 4251的重要部分

  mpint

  Represents multiple precision integers in two's complement format,
  stored as a string, 8 bits per byte, MSB first.  Negative numbers
  have the value 1 as the most significant bit of the first byte of
  the data partition.  If the most significant bit would be set for
  a positive number, the number MUST be preceded by a zero byte.
  Unnecessary leading bytes with the value 0 or 255 MUST NOT be
  included.  The value zero MUST be stored as a string with zero
  bytes of data.

  By convention, a number that is used in modular computations in
  Z_n SHOULD be represented in the range 0 <= x < n.

     Examples:

     value (hex)        representation (hex)
     -----------        --------------------
     0                  00 00 00 00
     9a378f9b2e332a7    00 00 00 08 09 a3 78 f9 b2 e3 32 a7
     80                 00 00 00 02 00 80
     -1234              00 00 00 02 ed cc
     -deadbeef          00 00 00 05 ff 21 52 41 11

Know all this, write code to convert ssh-rsa key to java format is easy.

知道这一切,编写代码将ssh-rsa密钥转换为java格式很容易。

private static int SIZEOF_INT = 4;
private static String key1 = "AAAAB3NzaC1yc2EAAAADAQABAAABAQClAxT5S/WuX04OXBt9R59WcL45OmaU3M5U063lfyja7ovqaVR7/2kHtLF/LoCQCXSZMny8RTCGDjoXD7G/tGsyHFDHCI//Y1VDLE06AlDzrlu69DQY91+6gkhGjH3SF6us5hXlihrbSFLfAlSdkEs8gwSrspVQyuaOf+39dnMddhEDYYg+z0ce82ta/n8xPBWCp60nDEDayNjOsRgzDJKSujNfngjQTL1x6qKJj8BW/P5lLJE1nbMm9BQD9G7glJk86qh1I/tJCnij6On0m6KcdzVz8cU3sBgNeB433kGjJtpxXXmJB6Vuu5IverhyfpiB4hP9WlKa/LSzW+ZIdvl/";

@Test
public void convertkey() throws Exception {
    byte[] decoded = java.util.Base64.getDecoder().decode(key1);

    try {
        ByteBuffer byteBuffer = ByteBuffer.wrap(decoded);

        AtomicInteger position = new AtomicInteger();
        //first read algorithm, should be ssh-rsa
        String algorithm = readString(byteBuffer, position);
        System.out.println(algorithm);
        assert "ssh-rsa".equals(algorithm);
        // than read exponent
        BigInteger publicExponent = readMpint(byteBuffer, position);
        System.out.println("publicExponent = " + publicExponent);
        // than read modulus
        BigInteger modulus = readMpint(byteBuffer, position);
        System.out.println("modulus = " + modulus);
        RSAPublicKeySpec keySpec = new RSAPublicKeySpec(modulus, publicExponent);
        KeyFactory kf = KeyFactory.getInstance("RSA");
        PublicKey publicKey = kf.generatePublic(keySpec);

        System.out.printf("Modulus: %X%n", modulus);
        System.out.printf("Public exponent: %d ... 17? Why?%n", publicExponent);
        System.out.printf("See, Java class result: %s, is RSAPublicKey: %b%n", publicKey.getClass().getName(), publicKey instanceof RSAPublicKey);

        byte[] pubBytes = publicKey.getEncoded();

        SubjectPublicKeyInfo spkInfo = SubjectPublicKeyInfo.getInstance(pubBytes);
        ASN1Primitive primitive = spkInfo.parsePublicKey();
        writePEM("pubPkcs1.pem", "RSA PUBLIC KEY", primitive.getEncoded() );
    } catch (Exception e) {
        e.printStackTrace();
    }

}

private BigInteger readMpint(ByteBuffer buffer, AtomicInteger pos){
    byte[] bytes = readBytes(buffer, pos);
    if(bytes.length == 0){
        return BigInteger.ZERO;
    }
    return new BigInteger(bytes);
}

private String readString(ByteBuffer buffer, AtomicInteger pos){
    byte[] bytes = readBytes(buffer, pos);
    if(bytes.length == 0){
        return "";
    }
    return new String(bytes, StandardCharsets.US_ASCII);
}

private byte[] readBytes(ByteBuffer buffer, AtomicInteger pos){
    int len = buffer.getInt(pos.get());
    byte buff[] = new byte[len];
    for(int i = 0; i < len; i++) {
        buff[i] = buffer.get(i + pos.get() + SIZEOF_INT);
    }
    pos.set(pos.get() + SIZEOF_INT + len);
    return buff;
}

private void writePEM(String fileName, String header, byte[] content) throws IOException{
    File f = new File(fileName);
    FileWriter fw = new FileWriter(f);
    PemObject pemObject = new PemObject(header, content);
    PemWriter pemWriter = new PemWriter(fw);
    pemWriter.writeObject(pemObject);
    pemWriter.close();
}

output

ssh-rsa
publicExponent = 65537
modulus = 20830840075214895520187085209140532093913000825284169131015003256319574044057453999265862514662442478787476545768050679936827456316397871442660366713280574836948529205417590573371022714192162142283026905055750951413644811120376414428742776306570652231542058994893537065648692533801879404176161589597321580633083481631733302249100913607754671673449460161582195402470090670605789220193388312197339358656479303453367386441996440265509774568364904443092245613429875362588897307051303623648237031289817493491475305022256278911859470009225208699382584578527080735302630318546541433464398236590978005758010444925861059033471
Modulus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
Public exponent: 65537 ... 17? Why?
See, Java class result: sun.security.rsa.RSAPublicKeyImpl, is RSAPublicKey: true

Second part - save java object as pkcs1 public key.

第二部分 - 将java对象保存为pkcs1公钥。

If you write pubkeys.getEncoded() you got pkcs8 public key, RSA public key is different. Format described in RFC 3447 appendix A.1.1

如果你写pubkeys.getEncoded()你得到pkcs8公钥,RSA公钥是不同的。 RFC 3447附录A.1.1中描述的格式

An RSA public key should be represented with the ASN.1 type
RSAPublicKey:

  RSAPublicKey ::= SEQUENCE {
      modulus           INTEGER,  -- n
      publicExponent    INTEGER   -- e
  }

The fields of type RSAPublicKey have the following meanings:
* modulus is the RSA modulus n.
* publicExponent is the RSA public exponent e.

This question ans especially Ian Boyd's answer gives many details.

这个问题尤其是Ian Boyd的回答提供了许多细节。

Bouncy castle already has class SubjectPublicKeyInfo to handle this situation.

Bouncy castle已经有类SubjectPublicKeyInfo来处理这种情况。

Code to convert to pkcs8 and pkcs1 format:

要转换为pkcs8和pkcs1格式的代码:

byte[] pubBytes = publicKey.getEncoded();
//writePEM("pubPkcs8.pem", "PUBLIC KEY", pubBytes ); // if you need pkcs8    
SubjectPublicKeyInfo spkInfo = SubjectPublicKeyInfo.getInstance(pubBytes);
ASN1Primitive primitive = spkInfo.parsePublicKey();
writePEM("pubPkcs1.pem", "RSA PUBLIC KEY", primitive.getEncoded() );

content of pubPkcs1.pem

pubPkcs1.pem的内容

-----BEGIN RSA PUBLIC KEY-----
MIIBCgKCAQEApQMU+Uv1rl9ODlwbfUefVnC+OTpmlNzOVNOt5X8o2u6L6mlUe/9p
B7Sxfy6AkAl0mTJ8vEUwhg46Fw+xv7RrMhxQxwiP/2NVQyxNOgJQ865buvQ0GPdf
uoJIRox90herrOYV5Yoa20hS3wJUnZBLPIMEq7KVUMrmjn/t/XZzHXYRA2GIPs9H
HvNrWv5/MTwVgqetJwxA2sjYzrEYMwySkrozX54I0Ey9ceqiiY/AVvz+ZSyRNZ2z
JvQUA/Ru4JSZPOqodSP7SQp4o+jp9JuinHc1c/HFN7AYDXgeN95BoybacV15iQel
bruSL3q4cn6YgeIT/VpSmvy0s1vmSHb5fwIDAQAB
-----END RSA PUBLIC KEY-----

checking results with openssl

用openssl检查结果

$ openssl asn1parse -in pubPkcs1.pem 
0:d=0  hl=4 l= 266 cons: SEQUENCE          
4:d=1  hl=4 l= 257 prim: INTEGER           :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
265:d=1  hl=2 l=   3 prim: INTEGER           :010001