package com.pengrad.telegrambot.passport.decrypt; import javax.crypto.Cipher; import java.io.ByteArrayInputStream; import java.io.IOException; import java.io.InputStream; import java.math.BigInteger; import java.security.KeyFactory; import java.security.PrivateKey; import java.security.spec.RSAPrivateCrtKeySpec; /** * Stas Parshin * 02 August 2018 */ class RsaOaep { static byte[] decrypt(String privateKey, byte[] secret) throws Exception { String pkcs8Pem = privateKey; pkcs8Pem = pkcs8Pem.replace("-----BEGIN RSA PRIVATE KEY-----", ""); pkcs8Pem = pkcs8Pem.replace("-----END RSA PRIVATE KEY-----", ""); pkcs8Pem = pkcs8Pem.replaceAll("\\s+", ""); byte[] pkcs8EncodedBytes = Base64.decode(pkcs8Pem, 0); KeyFactory kf = KeyFactory.getInstance("RSA"); PrivateKey privKey = kf.generatePrivate(getRSAKeySpec(pkcs8EncodedBytes)); Cipher cipher = Cipher.getInstance("RSA/ECB/OAEPWithSHA-1AndMGF1Padding"); cipher.init(Cipher.DECRYPT_MODE, privKey); return cipher.doFinal(secret); } private static 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; } private static 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 <code>Asn1Object.getParser</code>. * * @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. * <p> * <p/>In BER/DER encoding, length can be encoded in 2 forms, * <ul> * <li>Short form. One octet. Bit 8 has value "0" and bits 7-1 * give the length. * <li>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. * </ul> * * @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 */ private static 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. * <p> * <p/>The first byte in DER encoding is made of following fields, * <pre> * ------------------------------------------------- * |Bit 8|Bit 7|Bit 6|Bit 5|Bit 4|Bit 3|Bit 2|Bit 1| * ------------------------------------------------- * | Class | CF | + Type | * ------------------------------------------------- * </pre> * <ul> * <li>Class: Universal, Application, Context or Private * <li>CF: Constructed flag. If 1, the field is constructed. * <li>Type: This is actually called tag in ASN.1. It * indicates data type (Integer, String) or a construct * (sequence, choice, set). * </ul> * * @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); } } }