package com.nimbusds.srp6.cli;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
import java.math.BigInteger;
import com.nimbusds.srp6.BigIntegerUtils;
import com.nimbusds.srp6.SRP6CryptoParams;
/**
* The base abstract class for the interactive command-line SRP-6a tools.
*
* @author Vladimir Dzhuvinov
*/
public abstract class SRP6Tool {
/**
* Buffered console input reader.
*/
protected BufferedReader console;
/**
* Creates a new SRP-6a command-line tool.
*
* @throws IOException On console I/O exception.
*/
public SRP6Tool()
throws IOException {
// Prepare console input
InputStreamReader stdin = new InputStreamReader(System.in);
console = new BufferedReader(stdin);
}
/**
* Reads user input from the command-line.
*
* @param def The default string to return if nothing was entered by the
* user, {@code null} if user input is mandatory.
*
* @return The input string (trimmed).
*
* @throws IOException On missing input or console I/O exception.
*/
public String readInput(final String def)
throws IOException {
String input = console.readLine();
if (input == null || input.isEmpty()) {
if (def != null)
return def;
else
throw new IOException("Missing input");
}
return input.trim();
}
/**
* Reads user input from the command-line.
*
* @return The input string (trimmed).
*
* @throws IOException On missing input or console I/O exception.
*/
public String readInput()
throws IOException {
return readInput(null);
}
/**
* Reads a big integer (hex-encoded) from the command-line.
*
* @return The input big integer.
*
* @throws IOException On missing input, bad hex format or console I/O
* exception.
*/
public BigInteger readBigInteger()
throws IOException {
BigInteger bigInt = BigIntegerUtils.fromHex(readInput());
if (bigInt == null)
throw new IOException("Bad hex encoding");
return bigInt;
}
/**
* Interactive command-line session to select the SRP-6a crypto
* parameters.
*
* @param prefix String to prepend to the console output.
*
* @return SRP6CryptoParams The SRP-6a crypto parameters.
*
* @throws IOException On a console I/O exception.
*/
public SRP6CryptoParams getConfig(final String prefix)
throws IOException {
System.out.println(prefix + "Enter prime 'N' (hex): ");
System.out.println(prefix + "\t1 = select precomputed 256-bit");
System.out.println(prefix + "\t2 = select precomputed 512-bit");
System.out.println(prefix + "\t3 = select precomputed 768-bit");
System.out.println(prefix + "\t4 = select precomputed 1024-bit");
System.out.println(prefix + "\t5 = select precomputed 2048-bit");
System.out.println(prefix + "\t6 = enter prime 'N' and generator 'g'");
System.out.println();
System.out.print(prefix + "Your choice [1]: ");
String choice = readInput("1");
BigInteger N;
BigInteger g;
boolean selectedPrecomputed = true;
switch (choice) {
case "1":
N = SRP6CryptoParams.N_256;
g = SRP6CryptoParams.g_common;
break;
case "2":
N = SRP6CryptoParams.N_512;
g = SRP6CryptoParams.g_common;
break;
case "3":
N = SRP6CryptoParams.N_768;
g = SRP6CryptoParams.g_common;
break;
case "4":
N = SRP6CryptoParams.N_1024;
g = SRP6CryptoParams.g_common;
break;
case "5":
N = SRP6CryptoParams.N_2048;
g = SRP6CryptoParams.g_common;
break;
case "6":
System.out.println();
System.out.print(prefix + "Enter prime 'N' (hex): ");
N = readBigInteger();
System.out.print(prefix + "Enter generator 'g' (hex): ");
g = readBigInteger();
selectedPrecomputed = false;
break;
default:
throw new IOException("Unknown choice");
}
System.out.println();
if (selectedPrecomputed) {
System.out.println(prefix + "Selected prime 'N' (hex): " + BigIntegerUtils.toHex(N));
System.out.println(prefix + "Selected generator 'g' (hex): " + BigIntegerUtils.toHex(g));
System.out.println();
}
System.out.print(prefix + "Enter hash algorithm 'H' [SHA-1]: ");
String H = readInput("SHA-1");
System.out.println();
return new SRP6CryptoParams(N, g, H);
}
/**
* Runs the SRP-6a command-line tool.
*
* @throws IOException On missing / bad input or console I/O exception.
*/
public abstract void run() throws IOException;
}