Package org.apache.wss4j.common.crypto

Class DERDecoder

java.lang.Object
org.apache.wss4j.common.crypto.DERDecoder
Direct Known Subclasses:
X509SubjectPublicKeyInfo
public class DERDecoder extends Object
Provides the means to navigate through a DER-encoded byte array, to help in decoding the contents.

It maintains a "current position" in the array that advances with each operation, providing a simple means to handle the type-length-value encoding of DER. For example 

   decoder.expect(TYPE);
   int length = decoder.getLength();
   byte[] value = decoder.getBytes(len);

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final byte
    TYPE_BIT_STRING
    DER type identifier for a bit string value
    static final byte
    TYPE_OCTET_STRING
    DER type identifier for a octet string value
    static final byte
    TYPE_SEQUENCE
    DER type identifier for a sequence value

  • Constructor Summary

    Constructors
    Constructor
    Description
    DERDecoder(byte[] derEncoded)
    Construct a DERDecoder for the given byte array.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    expect(byte val)
    Confirm that the byte at the current position matches the given value.
    void
    expect(int val)
    Confirm that the byte at the current position matches the given value.
    byte[]
    getBytes(int length)
    Return an array of bytes from the current position.
    int
    getLength()
    Get the DER length at the current position.
    void
    reset()
    Reset the current position to the start of the array.
    void
    skip(int length)
    Advance the current position by the given number of bytes.
    boolean
    test(byte val)
    Test if the byte at the current position matches the given value.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

    • TYPE_BIT_STRING

      public static final byte TYPE_BIT_STRING
      DER type identifier for a bit string value
      See Also:

    • TYPE_OCTET_STRING

      public static final byte TYPE_OCTET_STRING
      DER type identifier for a octet string value
      See Also:

    • TYPE_SEQUENCE

      public static final byte TYPE_SEQUENCE
      DER type identifier for a sequence value
      See Also:

  • Constructor Details

    • DERDecoder

      public DERDecoder(byte[] derEncoded) throws WSSecurityException
      Construct a DERDecoder for the given byte array.
      Parameters:
      derEncoded - the DER-encoded array to decode.
      Throws:
      WSSecurityException - if the given array is null.

  • Method Details

    • reset

      public void reset()
      Reset the current position to the start of the array.

    • skip

      public void skip(int length) throws WSSecurityException
      Advance the current position by the given number of bytes.
      Parameters:
      length - the number of bytes to skip.
      Throws:
      WSSecurityException - if length is negative.

    • expect

      public void expect(int val) throws WSSecurityException
      Confirm that the byte at the current position matches the given value.
      Parameters:
      val - the expected next byte.
      Throws:
      WSSecurityException - if the current position is at the end of the array, or if the byte at the current position doesn't match the expected value.

    • expect

      public void expect(byte val) throws WSSecurityException
      Confirm that the byte at the current position matches the given value.
      Parameters:
      val - the expected next byte.
      Throws:
      WSSecurityException - if the current position is at the end of the array, or if the byte at the current position doesn't match the expected value.

    • test

      public boolean test(byte val) throws WSSecurityException
      Test if the byte at the current position matches the given value.
      Parameters:
      val - the value to test for a match with the current byte.
      Returns:
      true if the byte at the current position matches the given value.
      Throws:
      WSSecurityException - if the current position is at the end of the array.

    • getLength

      public int getLength() throws WSSecurityException
      Get the DER length at the current position.

      DER length is encoded as

      • If the first byte is 0x00 to 0x7F, it describes the actual length.
      • If the first byte is 0x80 + n with 0<n<0x7F, the actual length is described in the following 'n' bytes.
      • The length value 0x80, used only in constructed types, is defined as "indefinite length".
      Returns:
      the length, -1 for indefinite length.
      Throws:
      WSSecurityException - if the current position is at the end of the array or there is an incomplete length specification.

    • getBytes

      public byte[] getBytes(int length) throws WSSecurityException
      Return an array of bytes from the current position.
      Parameters:
      length - the number of bytes to return.
      Returns:
      an array of the requested number of bytes from the current position.
      Throws:
      WSSecurityException - if the current position is at the end of the array, or the length is negative.