1 files changed, 129 insertions, 0 deletions
diff --git a/src/main/java/eu/siacs/conversations/utils/CryptoHelper.java b/src/main/java/eu/siacs/conversations/utils/CryptoHelper.java
new file mode 100644
index 00000000..2dec203d
--- /dev/null
+++ b/src/main/java/eu/siacs/conversations/utils/CryptoHelper.java
@@ -0,0 +1,129 @@
+package eu.siacs.conversations.utils;
+
+import java.security.SecureRandom;
+import java.text.Normalizer;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.LinkedHashSet;
+import java.util.List;
+
+import eu.siacs.conversations.Config;
+
+public final class CryptoHelper {
+	public static final String FILETRANSFER = "?FILETRANSFERv1:";
+	private final static char[] hexArray = "0123456789abcdef".toCharArray();
+	private final static char[] vowels = "aeiou".toCharArray();
+	private final static char[] consonants = "bcdfghjklmnpqrstvwxyz".toCharArray();
+	final public static byte[] ONE = new byte[] { 0, 0, 0, 1 };
+
+	public static String bytesToHex(byte[] bytes) {
+		char[] hexChars = new char[bytes.length * 2];
+		for (int j = 0; j < bytes.length; j++) {
+			int v = bytes[j] & 0xFF;
+			hexChars[j * 2] = hexArray[v >>> 4];
+			hexChars[j * 2 + 1] = hexArray[v & 0x0F];
+		}
+		return new String(hexChars);
+	}
+
+	public static byte[] hexToBytes(String hexString) {
+		int len = hexString.length();
+		byte[] array = new byte[len / 2];
+		for (int i = 0; i < len; i += 2) {
+			array[i / 2] = (byte) ((Character.digit(hexString.charAt(i), 16) << 4) + Character
+					.digit(hexString.charAt(i + 1), 16));
+		}
+		return array;
+	}
+
+	public static String hexToString(final String hexString) {
+		return new String(hexToBytes(hexString));
+	}
+
+	public static byte[] concatenateByteArrays(byte[] a, byte[] b) {
+		byte[] result = new byte[a.length + b.length];
+		System.arraycopy(a, 0, result, 0, a.length);
+		System.arraycopy(b, 0, result, a.length, b.length);
+		return result;
+	}
+
+	public static String randomMucName(SecureRandom random) {
+		return randomWord(3, random) + "." + randomWord(7, random);
+	}
+
+	private static String randomWord(int lenght, SecureRandom random) {
+		StringBuilder builder = new StringBuilder(lenght);
+		for (int i = 0; i < lenght; ++i) {
+			if (i % 2 == 0) {
+				builder.append(consonants[random.nextInt(consonants.length)]);
+			} else {
+				builder.append(vowels[random.nextInt(vowels.length)]);
+			}
+		}
+		return builder.toString();
+	}
+
+	/**
+	 * Escapes usernames or passwords for SASL.
+	 */
+	public static String saslEscape(final String s) {
+		final StringBuilder sb = new StringBuilder((int) (s.length() * 1.1));
+		for (int i = 0; i < s.length(); i++) {
+			char c = s.charAt(i);
+			switch (c) {
+				case ',':
+					sb.append("=2C");
+					break;
+				case '=':
+					sb.append("=3D");
+					break;
+				default:
+					sb.append(c);
+					break;
+			}
+		}
+		return sb.toString();
+	}
+
+	public static String saslPrep(final String s) {
+		return Normalizer.normalize(s, Normalizer.Form.NFKC);
+	}
+
+	public static String prettifyFingerprint(String fingerprint) {
+		if (fingerprint==null) {
+			return "";
+		} else if (fingerprint.length() < 40) {
+			return fingerprint;
+		}
+		StringBuilder builder = new StringBuilder(fingerprint);
+		builder.insert(8, " ");
+		builder.insert(17, " ");
+		builder.insert(26, " ");
+		builder.insert(35, " ");
+		return builder.toString();
+	}
+
+	public static String[] getOrderedCipherSuites(final String[] platformSupportedCipherSuites) {
+		final Collection<String> cipherSuites = new LinkedHashSet<>(Arrays.asList(Config.ENABLED_CIPHERS));
+		final List<String> platformCiphers = Arrays.asList(platformSupportedCipherSuites);
+		cipherSuites.retainAll(platformCiphers);
+		cipherSuites.addAll(platformCiphers);
+		filterWeakCipherSuites(cipherSuites);
+		return cipherSuites.toArray(new String[cipherSuites.size()]);
+	}
+
+	private static void filterWeakCipherSuites(final Collection<String> cipherSuites) {
+		final Iterator<String> it = cipherSuites.iterator();
+		while (it.hasNext()) {
+			String cipherName = it.next();
+			// remove all ciphers with no or very weak encryption or no authentication
+			for (String weakCipherPattern : Config.WEAK_CIPHER_PATTERNS) {
+				if (cipherName.contains(weakCipherPattern)) {
+					it.remove();
+					break;
+				}
+			}
+		}
+	}
+}