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Java API for Telegram Bot API
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 bytes 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
*/
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.
*
*
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 when not constucted
*/
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 invalid der
*/
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);
}
}
}
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