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properly read IMSI as Mobile Identity (3GPP TS 24.008)

This commit is contained in:
Neels Hofmeyr 2020-02-24 18:58:56 +01:00
parent 89879a09c2
commit b7a20e3bfc
1 changed files with 92 additions and 13 deletions
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105
sim-applet/src/org/osmocom/IMSIPseudo/IMSIPseudo.java
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@ -99,11 +99,101 @@ public class IMSIPseudo extends Applet implements ToolkitInterface, ToolkitConst
showMsg(msg);
}
/* Convert BCD-encoded digit into printable character
* \param[in] bcd A single BCD-encoded digit
* \returns single printable character
*/
private 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
*/
private 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;
}
private boolean 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));
return bcd2str(dst, dst_ofs, dst_len, mi, start_nibble, end_nibble, allow_hex);
}
private void showIMSI() {
/* 3GPP TS 31.102 4.2.2: IMSI */
byte[] IMSI = new byte[9];
byte[] msg = {'C', 'u', 'r', 'r', 'e', 'n', 't', ' ', 'I', 'M', 'S', 'I', ':', ' ',
'_', '_', '_', '_', '_', '_', '_', '_', '_', '_', '_', '_', '_', '_', '_', '_', '_', '_'};
' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '};
gsmFile.select((short) SIMView.FID_DF_GSM);
gsmFile.select((short) SIMView.FID_EF_IMSI);
@ -114,19 +204,8 @@ public class IMSIPseudo extends Applet implements ToolkitInterface, ToolkitConst
showError(e.getReason());
return;
}
byte len = (byte) (IMSI[0] * 2);
for (byte i = (byte)0; i < (byte)18; i++) {
byte msg_i = (byte)(14 + i);
if (i >= len) {
msg[msg_i] = ' ';
} else if (i % (byte)2 == (byte)0) {
msg[msg_i] = (byte)('0' + (IMSI[i / (byte)2] & 0x0f));
} else {
msg[msg_i] = (byte)('0' + (IMSI[i / (byte)2] >>> 4));
}
showMsg(msg); /* DEBUG */
}
mi2str(msg, (byte)14, (byte)16, IMSI, false);
showMsg(msg);
}