Package org.forgerock.json.jose.utils

Class DerUtils

java.lang.Object
org.forgerock.json.jose.utils.DerUtils
public final class DerUtils extends Object
Utility methods for reading and writing DER-encoded values. This is just the absolute minimum needed to decode and encode ECDSA signatures to ES256 format.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final byte
    INTEGER_TAG
    DER tag for integer values.
    static final byte
    SEQUENCE_TAG
    DER tag for sequence values.

  • Method Summary

    Modifier and Type
    Method
    Description
    static byte[]
    decodeEcdsaSignature(byte[] signature, int signatureSize)
    Minimal DER decoder for the format returned by the SunEC signature provider.
    static byte[]
    encodeEcdsaSignature(byte[] signature)
    Minimal DER encoder for the format expected by the SunEC signature provider.
    static int
    readLength(ByteBuffer buffer)
    Reads a DER-encoded length field from the given byte buffer.
    static void
    readUnsignedInteger(ByteBuffer input, byte[] output, int offset, int length)
    Reads an unsigned integer value into the given byte array.
    static void
    writeInteger(ByteBuffer buffer, byte[] data)
    Writes an integer value in DER format to the given buffer.
    static void
    writeLength(ByteBuffer output, int length)
    Writes a length field to the output.

    Methods inherited from class java.lang.Object

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

  • Field Details

    • INTEGER_TAG

      public static final byte INTEGER_TAG
      DER tag for integer values.
      See Also:

    • SEQUENCE_TAG

      public static final byte SEQUENCE_TAG
      DER tag for sequence values.
      See Also:

  • Method Details

    • readUnsignedInteger

      public static void readUnsignedInteger(ByteBuffer input, byte[] output, int offset, int length)
      Reads an unsigned integer value into the given byte array. The output will be in big-endian format and aligned to take up exactly length bytes (leaving untouched any unused leading bytes).
      Parameters:
      input - the input DER-encoded byte buffer.
      output - the output byte array.
      offset - the offset into the byte array to start writing the integer value.
      length - the maximum length of the byte value (excluding any leading sign byte).
      Throws:
      BufferOverflowException - if the integer does not fit in the given output buffer slice.

    • writeInteger

      public static void writeInteger(ByteBuffer buffer, byte[] data)
      Writes an integer value in DER format to the given buffer.
      Parameters:
      buffer - the buffer to write the value to
      data - the integer value (in big-endian format) to write

    • readLength

      public static int readLength(ByteBuffer buffer)
      Reads a DER-encoded length field from the given byte buffer.
      Parameters:
      buffer - the buffer to read a length field from.
      Returns:
      the length field.

    • writeLength

      public static void writeLength(ByteBuffer output, int length)
      Writes a length field to the output. If the length is 127 or less, the byte is the length. If the length is 128 or greater, the first byte is a combination of 0x80 to indicate the length is defined and the number of bytes to specify that length. See DER specification for more information.
      Parameters:
      output - the output buffer.
      length - the length to write.

    • decodeEcdsaSignature

      public static byte[] decodeEcdsaSignature(byte[] signature, int signatureSize)
      Minimal DER decoder for the format returned by the SunEC signature provider.
      Parameters:
      signature - DER signature
      signatureSize - size
      Returns:
      decoded signature

    • encodeEcdsaSignature

      public static byte[] encodeEcdsaSignature(byte[] signature)
      Minimal DER encoder for the format expected by the SunEC signature provider.
      Parameters:
      signature - raw signature
      Returns:
      DER encoded signature