Parsing ASN.1 binary data with Java

问题:

I have binary ASN.1 data objects I need to parse into my Java project. I just want the ASN.1 structure and data as it is parsed for example by the BER viewer:

The ASN.1 parser of BouncyCastle is not able to parse this structure (only returns application specific binary data type).

What ASN.1 library can I use to get such a result? Does anybody has sample code that demonstrates how to parse an ASN.1 object?

BTW: I also tried several free ASN.1 Java compilers but none is able to generate working Java code given may ASN.1 specification.

回答1:

I have to correct myself - it is possible to read out the data using ASN.1 parser included in BouncyCastle - however the process is not that simple.

If you only want to print the data contained in an ASN.1 structure I recommend you to use the class org.bouncycastle.asn1.util.ASN1Dump. It can be used by the following simple code snippet:

ASN1InputStream bIn = new ASN1InputStream(new ByteArrayInputStream(data));
ASN1Primitive obj = bIn.readObject();
System.out.println(ASN1Dump.dumpAsString(obj));

It prints the structure but not the data - but by copying the ASN1Dump into an own class and modifying it to print out for example OCTET_STRINGS this can be done easily.

Additionally the code in ASN1Dump demonstrates to parse ASN.1 structures. For the example the data used in my question can be parsed one level deeper using the following code:

DERApplicationSpecific app = (DERApplicationSpecific) obj;
ASN1Sequence seq = (ASN1Sequence) app.getObject(BERTags.SEQUENCE);
Enumeration secEnum = seq.getObjects();
while (secEnum.hasMoreElements()) {
    ASN1Primitive seqObj = (ASN1Primitive) secEnum.nextElement();
    System.out.println(seqObj);
}

回答2:

Just use "true" to print values

    ASN1InputStream ais = new ASN1InputStream(
        new FileInputStream(new File("d:/myfile.cdr")));
    while (ais.available() > 0) {
        ASN1Primitive obj = ais.readObject();
        System.out.println(ASN1Dump.dumpAsString(obj, true));
    }
    ais.close();

回答3:

It is not clear from your question whether or not you have the ASN.1 specification for the BER you are trying to parse. Please note that without the ASN.1 specification, you can only make partial sense of the data if EXPLICIT TAGS were used in the ASN.1 specification from which it was generated. Some tools, such as the one from OSS Nokalva have a library (jar file) called JIAAPI which allows you to traverse and manipulate BER encodings without prior knowledge of the ASN.1 specification.

If you do have the ASN.1 specification, any ASN.1 Java compiler should be able to handle this.

You can download a free trial of the OSS ASN.1 Tools for Java from http://www.oss.com/asn1/products/asn1-download.html to see if works better for you than the others you unsuccessfully tried.

回答4:

I need to be able to parse any kind of ASN.1 data in krypt. Although krypt is a Ruby project, you may want to have a look at the JRuby extension - the code for handling ASN.1 parsing/encoding is written entirely in Java and modular enough for easy extraction.

I also made a Java-only version, but it is missing some of the higher-level functionality of the former. But since it's concise, maybe it's a good opportunity to get you started.

回答5:

If you just want to decode the BER-encoded data, there are numerous parsers out there. Have you tried any? There are even two in the Sun JDK - com.sun.jmx.snmp.BerDecoder and com.sun.jndi.ldap.BerDecoder.

回答6:

I am using bouncycastle API to print the string structure, below is the code snippet:

ASN1InputStream bIn = new ASN1InputStream(input);
    DERObject obj = bIn.readObject();
    System.out.println(CustomTreeNode.dumpAsString(obj));

In result it is printing structure but in octet string it is printing length instead of value. How to print value?