Neels Hofmeyr | d20f93a | 2020-02-24 22:42:22 +0100 | [diff] [blame] | 1 | /* Copyright 2020 sysmocom s.f.m.c. GmbH |
| 2 | * SPDX-License-Identifier: Apache-2.0 */ |
| 3 | package org.osmocom.IMSIPseudo; |
| 4 | |
| 5 | public class MobileIdentity { |
| 6 | public static final byte MI_IMSI = 1; |
| 7 | |
| 8 | /* Convert BCD-encoded digit into printable character |
| 9 | * \param[in] bcd A single BCD-encoded digit |
| 10 | * \returns single printable character |
| 11 | */ |
| 12 | public static byte bcd2char(byte bcd) |
| 13 | { |
| 14 | if (bcd < 0xa) |
| 15 | return (byte)('0' + bcd); |
| 16 | else |
| 17 | return (byte)('A' + (bcd - 0xa)); |
| 18 | } |
| 19 | |
| 20 | /* Convert BCD to string. |
| 21 | * The given nibble offsets are interpreted in BCD order, i.e. nibble 0 is bcd[0] & 0xf, nibble 1 is bcd[0] >> 4, nibble |
| 22 | * 3 is bcd[1] & 0xf, etc.. |
| 23 | * \param[out] dst Output byte array. |
| 24 | * \param[in] dst_ofs Where to start writing in dst. |
| 25 | * \param[in] dst_len How many bytes are available at dst_ofs. |
| 26 | * \param[in] bcd Binary coded data buffer. |
| 27 | * \param[in] start_nibble Offset to start from, in nibbles. |
| 28 | * \param[in] end_nibble Offset to stop before, in nibbles. |
| 29 | * \param[in] allow_hex If false, return false if there are digits other than 0-9. |
| 30 | * \returns true on success, false otherwise |
| 31 | */ |
| 32 | public static boolean bcd2str(byte dst[], byte dst_ofs, byte dst_len, |
| 33 | byte bcd[], byte start_nibble, byte end_nibble, boolean allow_hex) |
| 34 | { |
| 35 | byte nibble_i; |
| 36 | byte dst_i = dst_ofs; |
| 37 | byte dst_end = (byte)(dst_ofs + dst_len); |
| 38 | boolean rc = true; |
| 39 | |
| 40 | for (nibble_i = start_nibble; nibble_i < end_nibble && dst_i < dst_end; nibble_i++, dst_i++) { |
| 41 | byte nibble = bcd[(byte)nibble_i >> 1]; |
| 42 | if ((nibble_i & 1) != 0) |
| 43 | nibble >>= 4; |
| 44 | nibble &= 0xf; |
| 45 | |
| 46 | if (!allow_hex && nibble > 9) |
| 47 | rc = false; |
| 48 | |
| 49 | dst[dst_i] = bcd2char(nibble); |
| 50 | } |
| 51 | |
| 52 | return rc; |
| 53 | } |
| 54 | |
Neels Hofmeyr | 483f5a4 | 2020-02-25 03:06:12 +0100 | [diff] [blame^] | 55 | public static byte[] mi2str(byte mi[]) |
Neels Hofmeyr | d20f93a | 2020-02-24 22:42:22 +0100 | [diff] [blame] | 56 | { |
| 57 | /* The IMSI byte array by example: |
| 58 | * 08 99 10 07 00 00 10 74 90 |
| 59 | * |
| 60 | * This is encoded according to 3GPP TS 24.008 10.5.1.4 Mobile |
| 61 | * Identity, short the Mobile Identity IEI: |
| 62 | * |
| 63 | * 08 length for the following MI, in bytes. |
| 64 | * 9 = 0b1001 |
| 65 | * 1 = odd nr of digits |
| 66 | * 001 = MI type = IMSI |
| 67 | * 9 first IMSI digit (BCD) |
| 68 | * 0 second digit |
| 69 | * 1 third |
| 70 | * ... |
| 71 | * 0 14th digit |
| 72 | * 9 15th and last digit |
| 73 | * |
| 74 | * If the IMSI had an even number of digits: |
| 75 | * |
| 76 | * 08 98 10 07 00 00 10 74 f0 |
| 77 | * |
| 78 | * 08 length for the following MI, in bytes. |
| 79 | * 8 = 0b0001 |
| 80 | * 0 = even nr of digits |
| 81 | * 001 = MI type = IMSI |
| 82 | * 9 first IMSI digit |
| 83 | * 0 second digit |
| 84 | * 1 third |
| 85 | * ... |
| 86 | * 0 14th and last digit |
| 87 | * f filler |
| 88 | */ |
| 89 | byte bytelen = mi[0]; |
| 90 | byte mi_type = (byte)(mi[1] & 0xf); |
| 91 | boolean odd_nr_of_digits = ((mi_type & 0x08) != 0); |
| 92 | byte start_nibble = 2 + 1; // 2 to skip the bytelen, 1 to skip the mi_type |
| 93 | byte end_nibble = (byte)(2 + bytelen * 2 - (odd_nr_of_digits ? 0 : 1)); |
Neels Hofmeyr | 483f5a4 | 2020-02-25 03:06:12 +0100 | [diff] [blame^] | 94 | byte str[] = new byte[end_nibble - start_nibble]; |
| 95 | bcd2str(str, (byte)0, (byte)str.length, mi, start_nibble, end_nibble, true); |
| 96 | return str; |
Neels Hofmeyr | d20f93a | 2020-02-24 22:42:22 +0100 | [diff] [blame] | 97 | } |
| 98 | |
| 99 | public static byte char2bcd(byte c) |
| 100 | { |
| 101 | if (c >= '0' && c <= '9') |
| 102 | return (byte)(c - '0'); |
| 103 | else if (c >= 'A' && c <= 'F') |
| 104 | return (byte)(0xa + (c - 'A')); |
| 105 | else if (c >= 'a' && c <= 'f') |
| 106 | return (byte)(0xa + (c - 'a')); |
| 107 | else |
| 108 | return 0; |
| 109 | } |
| 110 | |
| 111 | public static byte[] str2mi(byte str[], byte mi_type, byte min_buflen) |
| 112 | { |
| 113 | boolean odd_digits = ((str.length & 1) != 0); |
| 114 | /* 1 nibble of mi_type. |
| 115 | * str.length nibbles of MI BCD. |
| 116 | */ |
| 117 | byte mi_nibbles = (byte)(1 + str.length); |
| 118 | byte mi_bytes = (byte)(mi_nibbles / 2 + ((mi_nibbles & 1) != 0? 1 : 0)); |
| 119 | /* 1 byte of total MI length in bytes, plus the MI nibbles */ |
| 120 | byte buflen = (byte)(1 + mi_bytes); |
| 121 | /* Fill up with 0xff to the requested buffer size */ |
| 122 | if (buflen < min_buflen) |
| 123 | buflen = min_buflen; |
| 124 | byte buf[] = new byte[buflen]; |
| 125 | |
| 126 | for (byte i = 0; i < buf.length; i++) |
| 127 | buf[i] = (byte)0xff; |
| 128 | |
| 129 | /* 1 byte of following MI length in bytes */ |
| 130 | buf[0] = mi_bytes; |
| 131 | |
| 132 | /* first MI byte: low nibble has the MI type and odd/even indicator bit, |
| 133 | * high nibble has the first BCD digit. |
| 134 | */ |
| 135 | mi_type = (byte)(mi_type & 0x07); |
| 136 | if (odd_digits) |
| 137 | mi_type |= 0x08; |
| 138 | buf[1] = (byte)((char2bcd(str[0]) << 4) + mi_type); |
| 139 | |
| 140 | /* fill in the remaining MI nibbles */ |
| 141 | byte str_i = 1; |
| 142 | for (byte mi_i = 1; mi_i < mi_bytes; mi_i++) { |
| 143 | byte data = char2bcd(str[str_i++]); |
| 144 | if (str_i < str.length) |
| 145 | data |= char2bcd(str[str_i++]) << 4; |
| 146 | else |
| 147 | data |= 0xf0; |
| 148 | buf[1 + mi_i] = data; |
| 149 | } |
| 150 | return buf; |
| 151 | } |
| 152 | } |