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Revise decode_wiegand function

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This commit is contained in:
Donny 2025-02-27 11:29:33 -08:00
commit d2e8066cbf
3 changed files with 15 additions and 43 deletions
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6
client/src/cmdwiegand.c
View file

@ -69,8 +69,7 @@ static int wiegand_new_pacs(uint8_t *padded_pacs, uint8_t plen) {
PrintAndLogEx(NORMAL, "");
PrintAndLogEx(INFO, "------------------------- " _CYAN_("SIO - Wiegand") " ---------------------------");
wiegand_message_t packed = initialize_message_object(top, mid, bot, strlen(binstr));
HIDTryUnpack(&packed);
decode_wiegand(top, mid, bot, strlen(binstr));
free(binstr);
return PM3_SUCCESS;
}
@ -215,8 +214,7 @@ int CmdWiegandDecode(const char *Cmd) {
PrintAndLogEx(NORMAL, "");
PrintAndLogEx(INFO, "Wiegand decode");
wiegand_message_t packed = initialize_message_object(top, mid, bot, blen);
HIDTryUnpack(&packed);
decode_wiegand(top, mid, bot, blen);
return PM3_SUCCESS;
}

16
client/src/wiegand_formats.c
View file

@ -1647,24 +1647,16 @@ bool decode_wiegand(uint32_t top, uint32_t mid, uint32_t bot, int n) {
return res;
}
if (n || ((mid & 0xFFFFFFC0) > 0)) { // if n > 0 or there's more than 38 bits
if (n > 0) {
wiegand_message_t packed = initialize_message_object(top, mid, bot, n);
res = HIDTryUnpack(&packed);
} else { // n <= 0 and 39-64 bits are all 0, try two possible bitlens
} else {
wiegand_message_t packed = initialize_message_object(top, mid, bot, n); // 26-37 bits
res = HIDTryUnpack(&packed);
n = packed.Length - 1;
PrintAndLogEx(INFO, "Trying without a preamble bit...");
packed = initialize_message_object(top, mid, bot, n); // iclass has only a preamble bit.
PrintAndLogEx(INFO, "Trying with a preamble bit...");
packed.Length += 1;
res |= HIDTryUnpack(&packed);
if (res == false) {
packed = initialize_message_object(top, mid, bot, 38); // 38 bits
res |= HIDTryUnpack(&packed);
}
}
if (res == false) {

36
client/src/wiegand_formatutils.c
View file

@ -132,8 +132,6 @@ static uint8_t get_length_from_header(wiegand_message_t *data) {
/**
* detect if message has "preamble" / "sentinel bit"
* Right now we just calculate the highest bit set
* 38 bits format is handled by directly setting n=38 in initialize_message_object()
* since it's hard to distinguish 38 bits with formats with preamble bit (26-36 bits)
*
* (from http://www.proxmark.org/forum/viewtopic.php?pid=5368#p5368)
* 0000 0010 0000 0000 01xx xxxx xxxx xxxx xxxx xxxx xxxx 26-bit
@ -148,7 +146,6 @@ static uint8_t get_length_from_header(wiegand_message_t *data) {
* 0000 0010 1xxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx 35-bit
* 0000 0011 xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx 36-bit
* 0000 000x xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx 37-bit
* 0000 00xx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx 38-bit
*/
uint8_t len = 0;
uint32_t hfmt = 0; // for calculating card length
@ -156,26 +153,15 @@ static uint8_t get_length_from_header(wiegand_message_t *data) {
if ((data->Top & 0x000FFFFF) > 0) { // > 64 bits
hfmt = data->Top & 0x000FFFFF;
len = 64;
} else if (data->Mid > 0) {
// detect HID format b38 set
if (data->Mid & 0xFFFFFFC0) { // 39-64 bits
hfmt = data->Mid;
len = 31; // remove leading 1 (preamble) in 39-64 bits format
} else { // detect card format 26-37 bits using "preamble" / "sentinel bit"
PrintAndLogEx(DEBUG, "hid preamble detected");
// if bit 38 is set: => 26-36 bits
if (((data->Mid >> 5) & 1) == 1) {
hfmt = (((data->Mid & 31) << 12) | (data->Bot >> 26)); //get bits 27-37 to check for format len bit
len = 19;
} else { // if bit 38 is not set => 37 bits
hfmt = 0;
len = 37;
}
}
} else {
hfmt = data->Bot;
len = 0;
} else if (data->Mid & 0xFFFFFFC0) { // handle 38bit and above format
hfmt = data->Mid;
len = 31; // remove leading 1 (preamble) in 38-64 bits format
} else if (((data->Mid >> 5) & 1) == 1) { // bit 38 is set => 26-36bit format
hfmt = (((data->Mid & 31) << 12) | (data->Bot >> 26)); // get bits 27-37 to check for format len bit
len = 19;
} else { // if bit 38 is not set => 37bit format
hfmt = 0;
len = 37;
}
while (hfmt > 0) {
@ -183,10 +169,6 @@ static uint8_t get_length_from_header(wiegand_message_t *data) {
len++;
}
// everything less than 26 bits found, assume 26 bits
if (len < 26)
len = 26;
return len;
}