| /* Copyright 2020 sysmocom s.f.m.c. GmbH |
| * SPDX-License-Identifier: Apache-2.0 */ |
| package org.osmocom.IMSIPseudo; |
| |
| public class MobileIdentity { |
| public static final byte MI_IMSI = 1; |
| |
| /* Convert BCD-encoded digit into printable character |
| * \param[in] bcd A single BCD-encoded digit |
| * \returns single printable character |
| */ |
| public static byte bcd2char(byte bcd) |
| { |
| if (bcd < 0xa) |
| return (byte)('0' + bcd); |
| else |
| return (byte)('A' + (bcd - 0xa)); |
| } |
| |
| /* Convert BCD to string. |
| * The given nibble offsets are interpreted in BCD order, i.e. nibble 0 is bcd[0] & 0xf, nibble 1 is bcd[0] >> 4, nibble |
| * 3 is bcd[1] & 0xf, etc.. |
| * \param[out] dst Output byte array. |
| * \param[in] dst_ofs Where to start writing in dst. |
| * \param[in] dst_len How many bytes are available at dst_ofs. |
| * \param[in] bcd Binary coded data buffer. |
| * \param[in] start_nibble Offset to start from, in nibbles. |
| * \param[in] end_nibble Offset to stop before, in nibbles. |
| * \param[in] allow_hex If false, return false if there are digits other than 0-9. |
| * \returns true on success, false otherwise |
| */ |
| public static boolean bcd2str(byte dst[], byte dst_ofs, byte dst_len, |
| byte bcd[], byte start_nibble, byte end_nibble, boolean allow_hex) |
| { |
| byte nibble_i; |
| byte dst_i = dst_ofs; |
| byte dst_end = (byte)(dst_ofs + dst_len); |
| boolean rc = true; |
| |
| for (nibble_i = start_nibble; nibble_i < end_nibble && dst_i < dst_end; nibble_i++, dst_i++) { |
| byte nibble = bcd[(byte)nibble_i >> 1]; |
| if ((nibble_i & 1) != 0) |
| nibble >>= 4; |
| nibble &= 0xf; |
| |
| if (!allow_hex && nibble > 9) |
| rc = false; |
| |
| dst[dst_i] = bcd2char(nibble); |
| } |
| |
| return rc; |
| } |
| |
| public static byte mi2str(byte dst[], byte dst_ofs, byte dst_len, |
| byte mi[], boolean allow_hex) |
| { |
| /* The IMSI byte array by example: |
| * 08 99 10 07 00 00 10 74 90 |
| * |
| * This is encoded according to 3GPP TS 24.008 10.5.1.4 Mobile |
| * Identity, short the Mobile Identity IEI: |
| * |
| * 08 length for the following MI, in bytes. |
| * 9 = 0b1001 |
| * 1 = odd nr of digits |
| * 001 = MI type = IMSI |
| * 9 first IMSI digit (BCD) |
| * 0 second digit |
| * 1 third |
| * ... |
| * 0 14th digit |
| * 9 15th and last digit |
| * |
| * If the IMSI had an even number of digits: |
| * |
| * 08 98 10 07 00 00 10 74 f0 |
| * |
| * 08 length for the following MI, in bytes. |
| * 8 = 0b0001 |
| * 0 = even nr of digits |
| * 001 = MI type = IMSI |
| * 9 first IMSI digit |
| * 0 second digit |
| * 1 third |
| * ... |
| * 0 14th and last digit |
| * f filler |
| */ |
| byte bytelen = mi[0]; |
| byte mi_type = (byte)(mi[1] & 0xf); |
| boolean odd_nr_of_digits = ((mi_type & 0x08) != 0); |
| byte start_nibble = 2 + 1; // 2 to skip the bytelen, 1 to skip the mi_type |
| byte end_nibble = (byte)(2 + bytelen * 2 - (odd_nr_of_digits ? 0 : 1)); |
| bcd2str(dst, dst_ofs, dst_len, mi, start_nibble, end_nibble, allow_hex); |
| return (byte)(end_nibble - start_nibble); |
| } |
| |
| public static byte char2bcd(byte c) |
| { |
| if (c >= '0' && c <= '9') |
| return (byte)(c - '0'); |
| else if (c >= 'A' && c <= 'F') |
| return (byte)(0xa + (c - 'A')); |
| else if (c >= 'a' && c <= 'f') |
| return (byte)(0xa + (c - 'a')); |
| else |
| return 0; |
| } |
| |
| public static byte[] str2mi(byte str[], byte mi_type, byte min_buflen) |
| { |
| boolean odd_digits = ((str.length & 1) != 0); |
| /* 1 nibble of mi_type. |
| * str.length nibbles of MI BCD. |
| */ |
| byte mi_nibbles = (byte)(1 + str.length); |
| byte mi_bytes = (byte)(mi_nibbles / 2 + ((mi_nibbles & 1) != 0? 1 : 0)); |
| /* 1 byte of total MI length in bytes, plus the MI nibbles */ |
| byte buflen = (byte)(1 + mi_bytes); |
| /* Fill up with 0xff to the requested buffer size */ |
| if (buflen < min_buflen) |
| buflen = min_buflen; |
| byte buf[] = new byte[buflen]; |
| |
| for (byte i = 0; i < buf.length; i++) |
| buf[i] = (byte)0xff; |
| |
| /* 1 byte of following MI length in bytes */ |
| buf[0] = mi_bytes; |
| |
| /* first MI byte: low nibble has the MI type and odd/even indicator bit, |
| * high nibble has the first BCD digit. |
| */ |
| mi_type = (byte)(mi_type & 0x07); |
| if (odd_digits) |
| mi_type |= 0x08; |
| buf[1] = (byte)((char2bcd(str[0]) << 4) + mi_type); |
| |
| /* fill in the remaining MI nibbles */ |
| byte str_i = 1; |
| for (byte mi_i = 1; mi_i < mi_bytes; mi_i++) { |
| byte data = char2bcd(str[str_i++]); |
| if (str_i < str.length) |
| data |= char2bcd(str[str_i++]) << 4; |
| else |
| data |= 0xf0; |
| buf[1 + mi_i] = data; |
| } |
| return buf; |
| } |
| } |