diff options
Diffstat (limited to 'sim-applet/src/org/osmocom/IMSIPseudo/MobileIdentity.java')
| -rw-r--r-- | sim-applet/src/org/osmocom/IMSIPseudo/MobileIdentity.java | 152 |
1 files changed, 152 insertions, 0 deletions
diff --git a/sim-applet/src/org/osmocom/IMSIPseudo/MobileIdentity.java b/sim-applet/src/org/osmocom/IMSIPseudo/MobileIdentity.java new file mode 100644 index 0000000..e363932 --- /dev/null +++ b/sim-applet/src/org/osmocom/IMSIPseudo/MobileIdentity.java @@ -0,0 +1,152 @@ +/* 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; + } +} |