org.bouncycastle.gpg.SXprUtils Maven / Gradle / Ivy

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The Bouncy Castle Java APIs for the OpenPGP Protocol. The APIs are designed primarily to be used in conjunction with the BC FIPS provider. The APIs may also be used with other providers although if being used in a FIPS context it is the responsibility of the user to ensure that any other providers used are FIPS certified and used appropriately.

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package org.bouncycastle.gpg;

import java.io.IOException;
import java.io.InputStream;

import org.bouncycastle.bcpg.HashAlgorithmTags;
import org.bouncycastle.bcpg.S2K;
import org.bouncycastle.util.io.Streams;

/**
 * Utility functions for looking a S-expression keys. This class will move when it finds a better home!
 * 
 * Format documented here:
 * http://git.gnupg.org/cgi-bin/gitweb.cgi?p=gnupg.git;a=blob;f=agent/keyformat.txt;h=42c4b1f06faf1bbe71ffadc2fee0fad6bec91a97;hb=refs/heads/master
 * 
 */
class SXprUtils
{
    private static int readLength(InputStream in, int ch)
        throws IOException
    {
        int len = ch - '0';

        while ((ch = in.read()) >= 0 && ch != ':')
        {
            len = len * 10 + ch - '0';
        }

        return len;
    }

    static String readString(InputStream in, int ch)
        throws IOException
    {
        int len = readLength(in, ch);

        char[] chars = new char[len];

        for (int i = 0; i != chars.length; i++)
        {
            chars[i] = (char)in.read();
        }

        return new String(chars);
    }

    static byte[] readBytes(InputStream in, int ch)
        throws IOException
    {
        int len = readLength(in, ch);

        byte[] data = new byte[len];

        Streams.readFully(in, data);

        return data;
    }

    static S2K parseS2K(InputStream in)
        throws IOException
    {
        skipOpenParenthesis(in);

        String alg = readString(in, in.read());
        byte[] iv = readBytes(in, in.read());
        final long iterationCount = Long.parseLong(readString(in, in.read()));

        skipCloseParenthesis(in);

        // we have to return the actual iteration count provided.
        S2K s2k = new S2K(HashAlgorithmTags.SHA1, iv, (int)iterationCount)
        {
            public long getIterationCount()
            {
                return iterationCount;
            }
        };

        return s2k;
    }

    static void skipOpenParenthesis(InputStream in)
        throws IOException
    {
        int ch = in.read();
        if (ch != '(')
        {
            throw new IOException("unknown character encountered");
        }
    }

    static void skipCloseParenthesis(InputStream in)
        throws IOException
    {
        int ch = in.read();
        if (ch != ')')
        {
            throw new IOException("unknown character encountered");
        }
    }
}