如何使用bouncycastle解析ASN1数据

Question

我有一个字节数组，它的形式是asn1，format..now，我想解析这个数据，得到所需的，information..Here是他们为c++..now写的代码，我想在java.could中做同样的事情。

ASN1 asn1(in)；

 int startPos = in.tellg();
 asn1.enterObject(asn1.getTag());
 int endPos = asn1.getCurrentLength() + in.tellg();

 ubytearray acctId, valData;

 while (in.tellg() < endPos) {
     asn1.enterObject(0x30); //0x30 TAG_SEQ

     // read the name
     ubytearray nameData = asn1.getContent(ASN1_TAG_UTF8_STRING);
     ubytearray octstr =  asn1.getContent(ASN1_TAG_OCTET_STRING);

字节数组证书(Octstr)；asn2.enterObject(0x30)；ustring urlstr(asn2.getContent(ASN1_TAG_UTF8_STRING))；ustring nameStr(asn2.getContent(ASN1_TAG_UTF8_STRING))；asn2.enterObject(0x30)；ubytearray ASN1 asn2= asn2.getContent(ASN1_TAG_OCTET_STRING)；

     if ((urlstr.length() > 0)  && (nameStr.length() > 0) && (certs.length() > 0)) {
         printf("url %s\n", urlstr.c_str());
         printf("name %s\n", nameStr.c_str());
         printf("certs len:%d\n", certs.length());  

}}

Answer 1

您应该能够使用org.bouncycastle.asn1中的类，从ASN1InputStream开始，从InputStream或byte[]读取ASN.1结构。要理解示例代码有点困难，但下面这样的代码可能会帮助您入门：

    byte[] data = null; // obviously need to supply real data here
    ASN1InputStream input = new ASN1InputStream(data);

    ASN1Primitive p;
    while ((p = input.readObject()) != null) {
        ASN1Sequence asn1 = ASN1Sequence.getInstance(p);

        DERUTF8String nameData = DERUTF8String.getInstance(asn1.getObjectAt(0));
        ASN1OctetString octstr = ASN1OctetString.getInstance(asn1.getObjectAt(1));

        ASN1Sequence asn2 = ASN1Sequence.getInstance(ASN1Primitive.fromByteArray(octstr.getOctets()));

        // ... and so on
    }

如果您发现数据的结构很难理解，也许org.bouncycastle.asn1.util.ASN1Dump类会有所帮助：

    byte[] data = null; // obviously need to supply real data here
    ASN1InputStream input = new ASN1InputStream(data);

    ASN1Primitive p;
    while ((p = input.readObject()) != null) {
        System.out.println(ASN1Dump.dumpAsString(p));
    }

Answer 2

对于PEM编码的签名，您可以使用

String signaturePem = "-----BEGIN PKCS7-----\n...";
PEMParser parser = new PEMParser(new StringReader(signaturePem));
ContentInfo contentInfo = (ContentInfo) parser.readObject();
CMSSignedData signedData = new CMSSignedData(contentInfo);
...

Answer 3

您可以像这样解码byteArray

String base64String = "Here is your byte array data";
byte[] data  = Base64.decode(base64String, Base64.DEFAULT);
String result= new String(data , "UTF-8");