SecureRandom.getInstanceStrong() uses /dev/random on Linux which may block if out of entropy

mark.george / BouncyScrypt

Browse code SecureRandom.getInstanceStrong() uses /dev/random on Linux which may block if out of entropy new SecureRandom() uses /dev/urandom master
1 parent f9a7fba commit 860fcd86997125049e472eeab3cb87b191cf92eb Mark George authored on 6 May

Patch

Showing 1 changed file

Ignore Space Show notes View src/main/java/helpers/ScryptHelper.java
package helpers; import java.nio.ByteBuffer; import java.nio.CharBuffer; import java.nio.charset.Charset; import java.nio.charset.CharsetEncoder; import java.nio.charset.StandardCharsets; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; import java.security.SecureRandom; import java.util.Arrays; import org.bouncycastle.crypto.generators.SCrypt; import org.bouncycastle.util.encoders.Base64; /** * Wrapper for Bouncy Castle's scrypt implementation. * * Generates salted scrypt hashes in a format similar to Modular Crypt Format * (MCF). * * @author Mark George <mark.george@otago.ac.nz> / public final class ScryptHelper { // the standard work factors for scrypt private static final int N = 32768; private static final int r = 8; private static final int p = 1; private static final int saltSize = 64; private static final int dkLen = 64; private static final Charset utf8 = StandardCharsets.UTF_8; private ScryptHelper() { } /* * Generates an MCF-like formatted salted scrypt hash for the password. * * @param password The password to hash. * @return The MCF formatted hash. / public static CharBuffer hash(CharSequence password) { byte[] salt = salt(); byte[] hash = hash(password, salt, N, r, p, dkLen); int costParams = (log2(N)) << 16 \| r << 8 \| p; byte[] dollar = "$".getBytes(utf8); byte[] params = String.valueOf(costParams).getBytes(utf8); byte[] b64salt = Base64.encode(salt); byte[] b64hash = Base64.encode(hash); int size = (4 dollar.length) + params.length + b64salt.length + b64hash.length; ByteBuffer mcf = ByteBuffer.allocate(size); mcf.put(dollar).put(params); mcf.put(dollar).put(b64salt); mcf.put(dollar).put(b64hash); mcf.put(dollar); mcf.flip(); CharBuffer result = utf8.decode(mcf); Arrays.fill(hash, (byte) 0); Arrays.fill(salt, (byte) 0); Arrays.fill(b64hash, (byte) 0); Arrays.fill(b64salt, (byte) 0); Arrays.fill(mcf.array(), (byte) 0); return result; } /** * Checks a hash (as generated by the hash method) against a password. * * @param mcfHash The MCF formatted hash. * @param password The password. * * @return True if the password matches the hash, false if not. / public static boolean check(CharSequence mcfHash, CharSequence password) { if (mcfHash == null \|\| mcfHash.length() == 0 \|\| mcfHash.charAt(0) != '$') { throw new IllegalArgumentException("Hash is not in a recognisable format"); } int[] indices = new int[4]; int count = 0; for (int i = 0; i < mcfHash.length() && count < 4; i++) { if (mcfHash.charAt(i) == '$') { indices[count++] = i; } } if (count != 4) { throw new IllegalArgumentException("Invalid format: missing delimiters"); } // Parse costParams int costParams = parseAsInt(mcfHash.subSequence(indices[0] + 1, indices[1])); // Use toBytes to get a clean byte array of the B64 encoded segments byte[] saltB64 = toBytes(mcfHash.subSequence(indices[1] + 1, indices[2])); byte[] hashB64 = toBytes(mcfHash.subSequence(indices[2] + 1, indices[3])); // Bouncy Castle decode to pre-allocated arrays byte[] salt = Base64.decode(saltB64); byte[] hash = Base64.decode(hashB64); try { int hN = 1 << (costParams >> 16); int hr = (costParams >> 8) & 255; int hp = costParams & 255; byte[] cHash = hash(password, salt, hN, hr, hp, hash.length); boolean matches = MessageDigest.isEqual(cHash, hash); Arrays.fill(cHash, (byte) 0); return matches; } finally { // Thorough cleanup Arrays.fill(saltB64, (byte) 0); Arrays.fill(hashB64, (byte) 0); Arrays.fill(salt, (byte) 0); Arrays.fill(hash, (byte) 0); } } /* * Parses a CharSequence as an integer without creating a String. / private static int parseAsInt(CharSequence s) { int val = 0; for (int i = 0; i < s.length(); i++) { int digit = Character.digit(s.charAt(i), 10); if (digit < 0) { throw new NumberFormatException("Invalid digit: " + s.charAt(i)); } val = val 10 + digit; } return val; } static byte[] hash(CharSequence password, byte[] salt, int N, int r, int p, int dkLen) { return SCrypt.generate(toBytes(password), salt, N, r, p, dkLen); } private static byte[] salt() { byte[] salt = new byte[saltSize]; new SecureRandom().nextBytes(salt); return salt; } private static int log2(int n) { if (n <= 0 \|\| (n & (n - 1)) != 0) { throw new IllegalArgumentException("N must be a power of 2"); } return Integer.numberOfTrailingZeros(n); } /* * Source: https://stackoverflow.com/a/9670279 / private static byte[] toBytes(CharSequence chars) { CharBuffer charBuffer = CharBuffer.wrap(chars); ByteBuffer byteBuffer = ByteBuffer.allocate(charBuffer.remaining() 3); // 3 bytes per char UTF-8 CharsetEncoder encoder = utf8.newEncoder(); encoder.encode(charBuffer, byteBuffer, true); encoder.flush(byteBuffer); byteBuffer.flip(); byte[] result = new byte[byteBuffer.remaining()]; byteBuffer.get(result); Arrays.fill(byteBuffer.array(), (byte) 0); return result; } } package helpers; import java.nio.ByteBuffer; import java.nio.CharBuffer; import java.nio.charset.Charset; import java.nio.charset.CharsetEncoder; import java.nio.charset.StandardCharsets; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; import java.security.SecureRandom; import java.util.Arrays; import org.bouncycastle.crypto.generators.SCrypt; import org.bouncycastle.util.encoders.Base64; /** * Wrapper for Bouncy Castle's scrypt implementation. * * Generates salted scrypt hashes in a format similar to Modular Crypt Format * (MCF). * * @author Mark George <mark.george@otago.ac.nz> / public final class ScryptHelper { // the standard work factors for scrypt private static final int N = 32768; private static final int r = 8; private static final int p = 1; private static final int saltSize = 64; private static final int dkLen = 64; private static final Charset utf8 = StandardCharsets.UTF_8; private ScryptHelper() { } /* * Generates an MCF-like formatted salted scrypt hash for the password. * * @param password The password to hash. * @return The MCF formatted hash. / public static CharBuffer hash(CharSequence password) { byte[] salt = salt(); byte[] hash = hash(password, salt, N, r, p, dkLen); int costParams = (log2(N)) << 16 \| r << 8 \| p; byte[] dollar = "$".getBytes(utf8); byte[] params = String.valueOf(costParams).getBytes(utf8); byte[] b64salt = Base64.encode(salt); byte[] b64hash = Base64.encode(hash); int size = (4 dollar.length) + params.length + b64salt.length + b64hash.length; ByteBuffer mcf = ByteBuffer.allocate(size); mcf.put(dollar).put(params); mcf.put(dollar).put(b64salt); mcf.put(dollar).put(b64hash); mcf.put(dollar); mcf.flip(); CharBuffer result = utf8.decode(mcf); Arrays.fill(hash, (byte) 0); Arrays.fill(salt, (byte) 0); Arrays.fill(b64hash, (byte) 0); Arrays.fill(b64salt, (byte) 0); Arrays.fill(mcf.array(), (byte) 0); return result; } /** * Checks a hash (as generated by the hash method) against a password. * * @param mcfHash The MCF formatted hash. * @param password The password. * * @return True if the password matches the hash, false if not. / public static boolean check(CharSequence mcfHash, CharSequence password) { if (mcfHash == null \|\| mcfHash.length() == 0 \|\| mcfHash.charAt(0) != '$') { throw new IllegalArgumentException("Hash is not in a recognisable format"); } int[] indices = new int[4]; int count = 0; for (int i = 0; i < mcfHash.length() && count < 4; i++) { if (mcfHash.charAt(i) == '$') { indices[count++] = i; } } if (count != 4) { throw new IllegalArgumentException("Invalid format: missing delimiters"); } // Parse costParams int costParams = parseAsInt(mcfHash.subSequence(indices[0] + 1, indices[1])); // Use toBytes to get a clean byte array of the B64 encoded segments byte[] saltB64 = toBytes(mcfHash.subSequence(indices[1] + 1, indices[2])); byte[] hashB64 = toBytes(mcfHash.subSequence(indices[2] + 1, indices[3])); // Bouncy Castle decode to pre-allocated arrays byte[] salt = Base64.decode(saltB64); byte[] hash = Base64.decode(hashB64); try { int hN = 1 << (costParams >> 16); int hr = (costParams >> 8) & 255; int hp = costParams & 255; byte[] cHash = hash(password, salt, hN, hr, hp, hash.length); boolean matches = MessageDigest.isEqual(cHash, hash); Arrays.fill(cHash, (byte) 0); return matches; } finally { // Thorough cleanup Arrays.fill(saltB64, (byte) 0); Arrays.fill(hashB64, (byte) 0); Arrays.fill(salt, (byte) 0); Arrays.fill(hash, (byte) 0); } } /* * Parses a CharSequence as an integer without creating a String. / private static int parseAsInt(CharSequence s) { int val = 0; for (int i = 0; i < s.length(); i++) { int digit = Character.digit(s.charAt(i), 10); if (digit < 0) { throw new NumberFormatException("Invalid digit: " + s.charAt(i)); } val = val 10 + digit; } return val; } static byte[] hash(CharSequence password, byte[] salt, int N, int r, int p, int dkLen) { return SCrypt.generate(toBytes(password), salt, N, r, p, dkLen); } private static byte[] salt() { try { byte[] salt = new byte[saltSize]; SecureRandom.getInstanceStrong().nextBytes(salt); return salt; } catch (NoSuchAlgorithmException ex) { throw new IllegalStateException("Strong RNG not supported on this computer", ex); } } private static int log2(int n) { if (n <= 0 \|\| (n & (n - 1)) != 0) { throw new IllegalArgumentException("N must be a power of 2"); } return Integer.numberOfTrailingZeros(n); } /* * Source: https://stackoverflow.com/a/9670279 / private static byte[] toBytes(CharSequence chars) { CharBuffer charBuffer = CharBuffer.wrap(chars); ByteBuffer byteBuffer = ByteBuffer.allocate(charBuffer.remaining() 3); // 3 bytes per char UTF-8 CharsetEncoder encoder = utf8.newEncoder(); encoder.encode(charBuffer, byteBuffer, true); encoder.flush(byteBuffer); byteBuffer.flip(); byte[] result = new byte[byteBuffer.remaining()]; byteBuffer.get(result); Arrays.fill(byteBuffer.array(), (byte) 0); return result; } }

Ignore Space Show notes View

src/main/java/helpers/ScryptHelper.java

package helpers;

import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Arrays;
import org.bouncycastle.crypto.generators.SCrypt;
import org.bouncycastle.util.encoders.Base64;

/**
 * Wrapper for Bouncy Castle's scrypt implementation.
 *
 * Generates salted scrypt hashes in a format similar to Modular Crypt Format
 * (MCF).
 *
 * @author Mark George <mark.george@otago.ac.nz>
 */
public final class ScryptHelper {

// the standard work factors for scrypt
	private static final int N = 32768;
	private static final int r = 8;
	private static final int p = 1;

private static final int saltSize = 64;
	private static final int dkLen = 64;

private static final Charset utf8 = StandardCharsets.UTF_8;

private ScryptHelper() {
	}

/**
	 * Generates an MCF-like formatted salted scrypt hash for the password.
	 *
	 * @param password The password to hash.
	 * @return The MCF formatted hash.
	 */
	public static CharBuffer hash(CharSequence password) {
		byte[] salt = salt();
		byte[] hash = hash(password, salt, N, r, p, dkLen);

int costParams = (log2(N)) << 16 | r << 8 | p;
		byte[] dollar = "$".getBytes(utf8);
		byte[] params = String.valueOf(costParams).getBytes(utf8);
		byte[] b64salt = Base64.encode(salt);
		byte[] b64hash = Base64.encode(hash);

int size = (4 * dollar.length) + params.length + b64salt.length + b64hash.length;

ByteBuffer mcf = ByteBuffer.allocate(size);
		mcf.put(dollar).put(params);
		mcf.put(dollar).put(b64salt);
		mcf.put(dollar).put(b64hash);
		mcf.put(dollar);
		mcf.flip();

CharBuffer result = utf8.decode(mcf);

Arrays.fill(hash, (byte) 0);
		Arrays.fill(salt, (byte) 0);
		Arrays.fill(b64hash, (byte) 0);
		Arrays.fill(b64salt, (byte) 0);
		Arrays.fill(mcf.array(), (byte) 0);

return result;
	}

/**
	 * Checks a hash (as generated by the hash method) against a password.
	 *
	 * @param mcfHash The MCF formatted hash.
	 * @param password The password.
	 *
	 * @return True if the password matches the hash, false if not.
	 */
	public static boolean check(CharSequence mcfHash, CharSequence password) {

if (mcfHash == null || mcfHash.length() == 0 || mcfHash.charAt(0) != '$') {
			throw new IllegalArgumentException("Hash is not in a recognisable format");
		}

int[] indices = new int[4];
		int count = 0;

for (int i = 0; i < mcfHash.length() && count < 4; i++) {
			if (mcfHash.charAt(i) == '$') {
				indices[count++] = i;
			}
		}

if (count != 4) {
			throw new IllegalArgumentException("Invalid format: missing delimiters");
		}

// Parse costParams
		int costParams = parseAsInt(mcfHash.subSequence(indices[0] + 1, indices[1]));

// Use toBytes to get a clean byte array of the B64 encoded segments
		byte[] saltB64 = toBytes(mcfHash.subSequence(indices[1] + 1, indices[2]));
		byte[] hashB64 = toBytes(mcfHash.subSequence(indices[2] + 1, indices[3]));

// Bouncy Castle decode to pre-allocated arrays
		byte[] salt = Base64.decode(saltB64);
		byte[] hash = Base64.decode(hashB64);

try {
			int hN = 1 << (costParams >> 16);
			int hr = (costParams >> 8) & 255;
			int hp = costParams & 255;

byte[] cHash = hash(password, salt, hN, hr, hp, hash.length);

boolean matches = MessageDigest.isEqual(cHash, hash);

Arrays.fill(cHash, (byte) 0);
			return matches;

} finally {
			// Thorough cleanup
			Arrays.fill(saltB64, (byte) 0);
			Arrays.fill(hashB64, (byte) 0);
			Arrays.fill(salt, (byte) 0);
			Arrays.fill(hash, (byte) 0);
		}
	}

/**
	 * Parses a CharSequence as an integer without creating a String.
	 */
	private static int parseAsInt(CharSequence s) {
		int val = 0;
		for (int i = 0; i < s.length(); i++) {
			int digit = Character.digit(s.charAt(i), 10);
			if (digit < 0) {
				throw new NumberFormatException("Invalid digit: " + s.charAt(i));
			}
			val = val * 10 + digit;
		}
		return val;
	}

static byte[] hash(CharSequence password, byte[] salt, int N, int r, int p, int dkLen) {
		return SCrypt.generate(toBytes(password), salt, N, r, p, dkLen);
	}

private static byte[] salt() {
		byte[] salt = new byte[saltSize];
		new SecureRandom().nextBytes(salt);
		return salt;
	}

private static int log2(int n) {
		if (n <= 0 || (n & (n - 1)) != 0) {
			throw new IllegalArgumentException("N must be a power of 2");
		}
		return Integer.numberOfTrailingZeros(n);
	}

/*
	 * Source: https://stackoverflow.com/a/9670279
	 */
	private static byte[] toBytes(CharSequence chars) {
		CharBuffer charBuffer = CharBuffer.wrap(chars);
		ByteBuffer byteBuffer = ByteBuffer.allocate(charBuffer.remaining() * 3); // 3 bytes per char UTF-8

CharsetEncoder encoder = utf8.newEncoder();
		encoder.encode(charBuffer, byteBuffer, true);
		encoder.flush(byteBuffer);

byteBuffer.flip();
		byte[] result = new byte[byteBuffer.remaining()];
		byteBuffer.get(result);

Arrays.fill(byteBuffer.array(), (byte) 0);
		return result;
	}

}