1package eu.siacs.conversations.utils;
2
3import java.security.SecureRandom;
4import java.text.Normalizer;
5import java.util.Arrays;
6import java.util.Collection;
7import java.util.Iterator;
8import java.util.LinkedHashSet;
9import java.util.List;
10
11import eu.siacs.conversations.Config;
12
13public final class CryptoHelper {
14 public static final String FILETRANSFER = "?FILETRANSFERv1:";
15 private final static char[] hexArray = "0123456789abcdef".toCharArray();
16 private final static char[] vowels = "aeiou".toCharArray();
17 private final static char[] consonants = "bcdfghjklmnpqrstvwxyz".toCharArray();
18 final public static byte[] ONE = new byte[] { 0, 0, 0, 1 };
19
20 public static String bytesToHex(byte[] bytes) {
21 char[] hexChars = new char[bytes.length * 2];
22 for (int j = 0; j < bytes.length; j++) {
23 int v = bytes[j] & 0xFF;
24 hexChars[j * 2] = hexArray[v >>> 4];
25 hexChars[j * 2 + 1] = hexArray[v & 0x0F];
26 }
27 return new String(hexChars);
28 }
29
30 public static byte[] hexToBytes(String hexString) {
31 int len = hexString.length();
32 byte[] array = new byte[len / 2];
33 for (int i = 0; i < len; i += 2) {
34 array[i / 2] = (byte) ((Character.digit(hexString.charAt(i), 16) << 4) + Character
35 .digit(hexString.charAt(i + 1), 16));
36 }
37 return array;
38 }
39
40 public static String hexToString(final String hexString) {
41 return new String(hexToBytes(hexString));
42 }
43
44 public static byte[] concatenateByteArrays(byte[] a, byte[] b) {
45 byte[] result = new byte[a.length + b.length];
46 System.arraycopy(a, 0, result, 0, a.length);
47 System.arraycopy(b, 0, result, a.length, b.length);
48 return result;
49 }
50
51 public static String randomMucName(SecureRandom random) {
52 return randomWord(3, random) + "." + randomWord(7, random);
53 }
54
55 private static String randomWord(int lenght, SecureRandom random) {
56 StringBuilder builder = new StringBuilder(lenght);
57 for (int i = 0; i < lenght; ++i) {
58 if (i % 2 == 0) {
59 builder.append(consonants[random.nextInt(consonants.length)]);
60 } else {
61 builder.append(vowels[random.nextInt(vowels.length)]);
62 }
63 }
64 return builder.toString();
65 }
66
67 /**
68 * Escapes usernames or passwords for SASL.
69 */
70 public static String saslEscape(final String s) {
71 final StringBuilder sb = new StringBuilder((int) (s.length() * 1.1));
72 for (int i = 0; i < s.length(); i++) {
73 char c = s.charAt(i);
74 switch (c) {
75 case ',':
76 sb.append("=2C");
77 break;
78 case '=':
79 sb.append("=3D");
80 break;
81 default:
82 sb.append(c);
83 break;
84 }
85 }
86 return sb.toString();
87 }
88
89 public static String saslPrep(final String s) {
90 return Normalizer.normalize(s, Normalizer.Form.NFKC);
91 }
92
93 public static String prettifyFingerprint(String fingerprint) {
94 if (fingerprint==null) {
95 return "";
96 } else if (fingerprint.length() < 40) {
97 return fingerprint;
98 }
99 StringBuilder builder = new StringBuilder(fingerprint.replaceAll("\\s",""));
100 for(int i=8;i<builder.length();i+=9) {
101 builder.insert(i, ' ');
102 }
103 return builder.toString();
104 }
105
106 public static String[] getOrderedCipherSuites(final String[] platformSupportedCipherSuites) {
107 final Collection<String> cipherSuites = new LinkedHashSet<>(Arrays.asList(Config.ENABLED_CIPHERS));
108 final List<String> platformCiphers = Arrays.asList(platformSupportedCipherSuites);
109 cipherSuites.retainAll(platformCiphers);
110 cipherSuites.addAll(platformCiphers);
111 filterWeakCipherSuites(cipherSuites);
112 return cipherSuites.toArray(new String[cipherSuites.size()]);
113 }
114
115 private static void filterWeakCipherSuites(final Collection<String> cipherSuites) {
116 final Iterator<String> it = cipherSuites.iterator();
117 while (it.hasNext()) {
118 String cipherName = it.next();
119 // remove all ciphers with no or very weak encryption or no authentication
120 for (String weakCipherPattern : Config.WEAK_CIPHER_PATTERNS) {
121 if (cipherName.contains(weakCipherPattern)) {
122 it.remove();
123 break;
124 }
125 }
126 }
127 }
128}