org.bouncycastle.crypto.util.SSHBuffer Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of bcprov-ext-debug-jdk18on Show documentation

The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for Java 1.8 and later with debug enabled.

The newest version!

package org.bouncycastle.crypto.util;

import java.math.BigInteger;

import org.bouncycastle.util.Arrays;
import org.bouncycastle.util.Strings;

/**
 * A Buffer for dealing with SSH key products.
 */
class SSHBuffer
{
    private final byte[] buffer;
    private int pos = 0;

    public SSHBuffer(byte[] magic, byte[] buffer)
    {
        this.buffer = buffer;
        for (int i = 0; i != magic.length; i++)
        {
            if (magic[i] != buffer[i])
            {
                throw new IllegalArgumentException("magic-number incorrect");
            }
        }

        pos += magic.length;
    }

    public SSHBuffer(byte[] buffer)
    {
        this.buffer = buffer;
    }

    public int readU32()
    {
        if (pos > (buffer.length - 4))
        {
            throw new IllegalArgumentException("4 bytes for U32 exceeds buffer.");
        }

        int i = (buffer[pos++] & 0xFF) << 24;
        i |= (buffer[pos++] & 0xFF) << 16;
        i |= (buffer[pos++] & 0xFF) << 8;
        i |= (buffer[pos++] & 0xFF);

        return i;
    }

    public String readString()
    {
        return Strings.fromByteArray(readBlock());
    }

    public byte[] readBlock()
    {
        int len = readU32();
        if (len == 0)
        {
            return new byte[0];
        }

        if (pos > (buffer.length - len))
        {
            throw new IllegalArgumentException("not enough data for block");
        }

        int start = pos; pos += len;
        return Arrays.copyOfRange(buffer, start, pos);
    }

    public void skipBlock()
    {
        int len = readU32();
        if (pos > (buffer.length - len))
        {
            throw new IllegalArgumentException("not enough data for block");
        }

        pos += len;
    }

    public byte[] readPaddedBlock()
    {
        return readPaddedBlock(8);
    }

    public byte[] readPaddedBlock(int blockSize)
    {
        int len = readU32();
        if (len == 0)
        {
            return new byte[0];
        }

        if (pos > (buffer.length - len))
        {
            throw new IllegalArgumentException("not enough data for block");
        }

        int align = len % blockSize;
        if (0 != align)
        {
            throw new IllegalArgumentException("missing padding");
        }

        int start = pos; pos += len;
        int end = pos;

        if (len > 0)
        {
            // TODO If encryption is supported, should be constant-time
            int lastByte = buffer[pos - 1] & 0xFF;
            if (0 < lastByte && lastByte < blockSize)
            {
                int padCount = lastByte;
                end -= padCount;

                for (int i = 1, padPos = end; i <= padCount; ++i, ++padPos)
                {
                    if (i != (buffer[padPos] & 0xFF))
                    {
                        throw new IllegalArgumentException("incorrect padding");
                    }
                }
            }
        }

        return Arrays.copyOfRange(buffer, start, end);
    }

    public BigInteger readBigNumPositive()
    {
        int len = readU32();
        if (pos + len > buffer.length)
        {
            throw new IllegalArgumentException("not enough data for big num");
        }

        int start = pos; pos += len;
        byte[] d = Arrays.copyOfRange(buffer, start, pos);
        return new BigInteger(1, d);
    }

    public byte[] getBuffer()
    {
        return Arrays.clone(buffer);
    }

    public boolean hasRemaining()
    {
        return pos < buffer.length;
    }
}