Load a RSA private key in Java (algid parse error, not a sequence)

Question

I\'m trying to load a private RSA key generated with ssl into java, my code is:

Generate the key:

openssl genrsa -out mykey.pem 1024         


        

Answer 1

Here's a modified org.apache.jmeter.protocol.oauth.sampler.PrivateKeyReader code using Java runtime only. It works for me, it can load PKCS#1 or PKCS#8 private key file and returns a PrivateKey class. (Please let me know if i messed up anything while copy/pasting).

Use it like this: PrivateKey pk = (new PrivateKeyReader("/path/to/myfile.der")).getPrivateKey();

/**
 * 
 */
package default;

/****************************************************************************
 * Copyright (c) 1998-2010 AOL Inc. 
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Modified 23-4-2015 misterti
 *  
 ****************************************************************************/

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.math.BigInteger;
import java.security.GeneralSecurityException;
import java.security.KeyFactory;
import java.security.PrivateKey;
import java.security.spec.KeySpec;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.RSAPrivateCrtKeySpec;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

import javax.xml.bind.DatatypeConverter;


/**
 * Class for reading RSA private key from PEM file. It uses
 * the JMeter FileServer to find the file. So the file should 
 * be located in the same directory as the test plan if the 
 * path is relative.
 * 
 * 
There is a cache so each file is only read once. If file
 * is changed, it will not take effect until the program 
 * restarts.
 * 
 * 
It can read PEM files with PKCS#8 or PKCS#1 encodings.
 * It doesn't support encrypted PEM files.
 * 
 */
public class PrivateKeyReader {

  // Private key file using PKCS #1 encoding
  public static final String P1_BEGIN_MARKER 
    = "-----BEGIN RSA PRIVATE KEY"; //$NON-NLS-1$
  public static final String P1_END_MARKER
      = "-----END RSA PRIVATE KEY"; //$NON-NLS-1$

  // Private key file using PKCS #8 encoding
  public static final String P8_BEGIN_MARKER 
    = "-----BEGIN PRIVATE KEY"; //$NON-NLS-1$
  public static final String P8_END_MARKER
      = "-----END PRIVATE KEY"; //$NON-NLS-1$

  private static Map keyCache =
    Collections.synchronizedMap(new HashMap());

  protected final String fileName;

  /**
   * Create a PEM private key file reader.
   * 
   * @param fileName The name of the PEM file
   */
  public PrivateKeyReader(String fileName) {
    this.fileName = fileName;
  }

  /**
   * Get a Private Key for the file.
   * 
   * @return Private key
   * @throws IOException
   */

  public PrivateKey getPrivateKey() throws IOException, GeneralSecurityException 
  {
    PrivateKey key = null;
    FileInputStream fis = null;
    boolean isRSAKey = false;
    try {
        File f = new File(fileName);
        fis = new FileInputStream(f);

        BufferedReader br = new BufferedReader(new InputStreamReader(fis));
        StringBuilder builder = new StringBuilder();
        boolean inKey = false;
        for (String line = br.readLine(); line != null; line = br.readLine()) {
            if (!inKey) {
                if (line.startsWith("-----BEGIN ") && 
                        line.endsWith(" PRIVATE KEY-----")) {
                    inKey = true;
                    isRSAKey = line.contains("RSA");
                }
                continue;
            }
            else {
                if (line.startsWith("-----END ") && 
                        line.endsWith(" PRIVATE KEY-----")) {
                    inKey = false;
                    isRSAKey = line.contains("RSA");
                    break;
                }
                builder.append(line);
            }
        }
        KeySpec keySpec = null;
        byte[] encoded = DatatypeConverter.parseBase64Binary(builder.toString());          
        if (isRSAKey)
        {
          keySpec = getRSAKeySpec(encoded);
        }
        else
        {
          keySpec = new PKCS8EncodedKeySpec(encoded);
        }
        KeyFactory kf = KeyFactory.getInstance("RSA");
        key = kf.generatePrivate(keySpec);
    } finally {
      if (fis != null)
        try { fis.close(); } catch (Exception ign) {}  }
    return key;
  }


    /**
     * Convert PKCS#1 encoded private key into RSAPrivateCrtKeySpec.
     * 
     * 
The ASN.1 syntax for the private key with CRT is
     * 
     * 
     * -- 
     * -- Representation of RSA private key with information for the CRT algorithm.
     * --
   * RSAPrivateKey ::= SEQUENCE {
     *   version           Version, 
     *   modulus           INTEGER,  -- n
     *   publicExponent    INTEGER,  -- e
     *   privateExponent   INTEGER,  -- d
     *   prime1            INTEGER,  -- p
     *   prime2            INTEGER,  -- q
     *   exponent1         INTEGER,  -- d mod (p-1)
     *   exponent2         INTEGER,  -- d mod (q-1) 
     *   coefficient       INTEGER,  -- (inverse of q) mod p
     *   otherPrimeInfos   OtherPrimeInfos OPTIONAL 
     * }
     * 
     * 
     * @param keyBytes PKCS#1 encoded key
     * @return KeySpec
     * @throws IOException
     */

    private RSAPrivateCrtKeySpec getRSAKeySpec(byte[] keyBytes) throws IOException  {

      DerParser parser = new DerParser(keyBytes);

      Asn1Object sequence = parser.read();
        if (sequence.getType() != DerParser.SEQUENCE)
          throw new IOException("Invalid DER: not a sequence"); //$NON-NLS-1$

        // Parse inside the sequence
        parser = sequence.getParser();

        parser.read(); // Skip version
        BigInteger modulus = parser.read().getInteger();
        BigInteger publicExp = parser.read().getInteger();
        BigInteger privateExp = parser.read().getInteger();
        BigInteger prime1 = parser.read().getInteger();
        BigInteger prime2 = parser.read().getInteger();
        BigInteger exp1 = parser.read().getInteger();
        BigInteger exp2 = parser.read().getInteger();
        BigInteger crtCoef = parser.read().getInteger();

        RSAPrivateCrtKeySpec keySpec = new RSAPrivateCrtKeySpec(
            modulus, publicExp, privateExp, prime1, prime2,
            exp1, exp2, crtCoef);

        return keySpec;
    }    
}

/**
 * A bare-minimum ASN.1 DER decoder, just having enough functions to 
 * decode PKCS#1 private keys. Especially, it doesn't handle explicitly
 * tagged types with an outer tag.
 * 
 * 
This parser can only handle one layer. To parse nested constructs,
 * get a new parser for each layer using Asn1Object.getParser().
 * 
 * 
There are many DER decoders in JRE but using them will tie this
 * program to a specific JCE/JVM.
 * 
 * @author zhang
 *
 */
class DerParser {

  // Classes
  public final static int UNIVERSAL = 0x00;
  public final static int APPLICATION = 0x40;
  public final static int CONTEXT = 0x80;
  public final static int PRIVATE = 0xC0;

  // Constructed Flag
  public final static int CONSTRUCTED = 0x20;

  // Tag and data types
  public final static int ANY = 0x00;
  public final static int BOOLEAN = 0x01;
  public final static int INTEGER = 0x02;
  public final static int BIT_STRING = 0x03;
  public final static int OCTET_STRING = 0x04;
  public final static int NULL = 0x05;
  public final static int OBJECT_IDENTIFIER = 0x06;
  public final static int REAL = 0x09;
  public final static int ENUMERATED = 0x0a;
  public final static int RELATIVE_OID = 0x0d;

  public final static int SEQUENCE = 0x10;
  public final static int SET = 0x11;

  public final static int NUMERIC_STRING = 0x12;
  public final static int PRINTABLE_STRING = 0x13;
  public final static int T61_STRING = 0x14;
  public final static int VIDEOTEX_STRING = 0x15;
  public final static int IA5_STRING = 0x16;
  public final static int GRAPHIC_STRING = 0x19;
  public final static int ISO646_STRING = 0x1A;
  public final static int GENERAL_STRING = 0x1B;

  public final static int UTF8_STRING = 0x0C;
  public final static int UNIVERSAL_STRING = 0x1C;
  public final static int BMP_STRING = 0x1E;

  public final static int UTC_TIME = 0x17;
  public final static int GENERALIZED_TIME = 0x18;

  protected InputStream in;

  /**
   * Create a new DER decoder from an input stream.
   * 
   * @param in
   *            The DER encoded stream
   */
  public DerParser(InputStream in) throws IOException {
    this.in = in;
  }

  /**
   * Create a new DER decoder from a byte array.
   * 
   * @param The
   *            encoded bytes
   * @throws IOException 
   */
  public DerParser(byte[] bytes) throws IOException {
    this(new ByteArrayInputStream(bytes));
  }

  /**
   * Read next object. If it's constructed, the value holds
   * encoded content and it should be parsed by a new
   * parser from Asn1Object.getParser.
   * 
   * @return A object
   * @throws IOException
   */
  public Asn1Object read() throws IOException {
    int tag = in.read();

    if (tag == -1)
      throw new IOException("Invalid DER: stream too short, missing tag"); //$NON-NLS-1$

    int length = getLength();

    byte[] value = new byte[length];
    int n = in.read(value);
    if (n < length)
      throw new IOException("Invalid DER: stream too short, missing value"); //$NON-NLS-1$

    Asn1Object o = new Asn1Object(tag, length, value);

    return o;
  }

  /**
   * Decode the length of the field. Can only support length
   * encoding up to 4 octets.
   * 
   * 
In BER/DER encoding, length can be encoded in 2 forms,
   * 

   * 
Short form. One octet. Bit 8 has value "0" and bits 7-1
   * give the length.
     * 
Long form. Two to 127 octets (only 4 is supported here). 
     * Bit 8 of first octet has value "1" and bits 7-1 give the 
     * number of additional length octets. Second and following 
     * octets give the length, base 256, most significant digit first.
   * 
   * @return The length as integer
   * @throws IOException
   */
  private int getLength() throws IOException {

    int i = in.read();
    if (i == -1)
      throw new IOException("Invalid DER: length missing"); //$NON-NLS-1$

    // A single byte short length
    if ((i & ~0x7F) == 0)
      return i;

    int num = i & 0x7F;

    // We can't handle length longer than 4 bytes
    if ( i >= 0xFF || num > 4) 
      throw new IOException("Invalid DER: length field too big (" //$NON-NLS-1$
          + i + ")"); //$NON-NLS-1$

    byte[] bytes = new byte[num];     
    int n = in.read(bytes);
    if (n < num)
      throw new IOException("Invalid DER: length too short"); //$NON-NLS-1$

    return new BigInteger(1, bytes).intValue();
  }

}


/**
 * An ASN.1 TLV. The object is not parsed. It can
 * only handle integers and strings.
 * 
 * @author zhang
 *
 */
class Asn1Object {

  protected final int type;
  protected final int length;
  protected final byte[] value;
  protected final int tag;

  /**
   * Construct a ASN.1 TLV. The TLV could be either a
   * constructed or primitive entity.
   * 
   * 
The first byte in DER encoding is made of following fields,
   * 
   *-------------------------------------------------
     *|Bit 8|Bit 7|Bit 6|Bit 5|Bit 4|Bit 3|Bit 2|Bit 1|
     *-------------------------------------------------
     *|  Class    | CF  |     +      Type             |
     *-------------------------------------------------
   * 
   * 

   * 
Class: Universal, Application, Context or Private
   * 
CF: Constructed flag. If 1, the field is constructed.
   * 
Type: This is actually called tag in ASN.1. It
   * indicates data type (Integer, String) or a construct
   * (sequence, choice, set).
   * 
   * 
   * @param tag Tag or Identifier
   * @param length Length of the field
   * @param value Encoded octet string for the field.
   */
  public Asn1Object(int tag, int length, byte[] value) {
    this.tag = tag;
    this.type = tag & 0x1F;
    this.length = length;
    this.value = value;
  }

  public int getType() {
    return type;
  }

  public int getLength() {
    return length;
  }

  public byte[] getValue() {
    return value;
  }

  public boolean isConstructed() {
    return  (tag & DerParser.CONSTRUCTED) == DerParser.CONSTRUCTED;
  }

  /**
   * For constructed field, return a parser for its content.
   * 
   * @return A parser for the construct.
   * @throws IOException
   */
  public DerParser getParser() throws IOException {
    if (!isConstructed()) 
      throw new IOException("Invalid DER: can't parse primitive entity"); //$NON-NLS-1$

    return new DerParser(value);
  }

  /**
   * Get the value as integer
   * 
   * @return BigInteger
   * @throws IOException
   */
  public BigInteger getInteger() throws IOException {
      if (type != DerParser.INTEGER)
        throw new IOException("Invalid DER: object is not integer"); //$NON-NLS-1$

      return new BigInteger(value);
  }

  /**
   * Get value as string. Most strings are treated
   * as Latin-1.
   * 
   * @return Java string
   * @throws IOException
   */
  public String getString() throws IOException {

    String encoding;

    switch (type) {

    // Not all are Latin-1 but it's the closest thing
    case DerParser.NUMERIC_STRING:
    case DerParser.PRINTABLE_STRING:
    case DerParser.VIDEOTEX_STRING:
    case DerParser.IA5_STRING:
    case DerParser.GRAPHIC_STRING:
    case DerParser.ISO646_STRING:
    case DerParser.GENERAL_STRING:
      encoding = "ISO-8859-1"; //$NON-NLS-1$
      break;

    case DerParser.BMP_STRING:
      encoding = "UTF-16BE"; //$NON-NLS-1$
      break;

    case DerParser.UTF8_STRING:
      encoding = "UTF-8"; //$NON-NLS-1$
      break;

    case DerParser.UNIVERSAL_STRING:
      throw new IOException("Invalid DER: can't handle UCS-4 string"); //$NON-NLS-1$

    default:
      throw new IOException("Invalid DER: object is not a string"); //$NON-NLS-1$
    }

    return new String(value, encoding);
  }
}