98 lines
3.0 KiB
Java
98 lines
3.0 KiB
Java
package com.ryanmichela.sshd;
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import org.apache.mina.util.Base64;
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import java.io.Reader;
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import java.math.BigInteger;
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import java.security.KeyFactory;
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import java.security.PublicKey;
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import java.security.spec.DSAPublicKeySpec;
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import java.security.spec.RSAPublicKeySpec;
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/**
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* Copyright 2013 Ryan Michela
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*/
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public class PemDecoder extends java.io.BufferedReader {
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private static final String BEGIN = "^-+\\s*BEGIN.+";
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private static final String END = "^-+\\s*END.+";
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private static final String COMMENT = "Comment:";
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public PemDecoder(Reader in) {
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super(in);
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}
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public PublicKey getPemBytes() throws Exception {
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StringBuffer b64 = new StringBuffer();
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String line = readLine();
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if (!line.matches(BEGIN)) {
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return null;
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}
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for(line = readLine(); line != null; line = readLine()) {
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if (!line.matches(END) && !line.startsWith(COMMENT)) {
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b64.append(line.trim());
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}
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}
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return decodePublicKey(b64.toString());
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}
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private byte[] bytes;
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private int pos;
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private PublicKey decodePublicKey(String keyLine) throws Exception {
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bytes = null;
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pos = 0;
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// look for the Base64 encoded part of the line to decode
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// both ssh-rsa and ssh-dss begin with "AAAA" due to the length bytes
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for (String part : keyLine.split(" ")) {
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if (part.startsWith("AAAA")) {
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bytes = Base64.decodeBase64(part.getBytes());
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break;
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}
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}
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if (bytes == null) {
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throw new IllegalArgumentException("no Base64 part to decode");
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}
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String type = decodeType();
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if (type.equals("ssh-rsa")) {
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BigInteger e = decodeBigInt();
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BigInteger m = decodeBigInt();
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RSAPublicKeySpec spec = new RSAPublicKeySpec(m, e);
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return KeyFactory.getInstance("RSA").generatePublic(spec);
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} else if (type.equals("ssh-dss")) {
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BigInteger p = decodeBigInt();
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BigInteger q = decodeBigInt();
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BigInteger g = decodeBigInt();
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BigInteger y = decodeBigInt();
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DSAPublicKeySpec spec = new DSAPublicKeySpec(y, p, q, g);
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return KeyFactory.getInstance("DSA").generatePublic(spec);
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} else {
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throw new IllegalArgumentException("unknown type " + type);
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}
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}
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private String decodeType() {
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int len = decodeInt();
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String type = new String(bytes, pos, len);
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pos += len;
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return type;
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}
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private int decodeInt() {
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return ((bytes[pos++] & 0xFF) << 24) | ((bytes[pos++] & 0xFF) << 16)
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| ((bytes[pos++] & 0xFF) << 8) | (bytes[pos++] & 0xFF);
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}
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private BigInteger decodeBigInt() {
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int len = decodeInt();
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byte[] bigIntBytes = new byte[len];
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System.arraycopy(bytes, pos, bigIntBytes, 0, len);
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pos += len;
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return new BigInteger(bigIntBytes);
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}
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}
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