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LFRFID: Guard GProxII Wiegand Check Against False Positive and Correc…
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…t 36-bit Parsing (#3868)

* Update protocol_gproxii.c
* 36 bit format parsing fix
* Update protocol_gproxii.c
* wiegand checks as single function
* LfRfid: simplify gprox wiegand payload validation flow
* LfRfid: extra furi_check in gprox wiegand validation code

Co-authored-by: Aleksandr Kutuzov <[email protected]>
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@zinongli @skotopes
zinongli and skotopes authored Sep 8, 2024
1 parent 8c2223d commit a122ee7
Showing 1 changed file with 67 additions and 15 deletions.
82 changes: 67 additions & 15 deletions lib/lfrfid/protocols/protocol_gproxii.c
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Original file line number Diff line number Diff line change
Expand Up @@ -38,8 +38,48 @@ void protocol_gproxii_free(ProtocolGProxII* protocol) {
free(protocol);
}

uint8_t* protocol_gproxii_get_data(ProtocolGProxII* proto) {
return proto->decoded_data;
uint8_t* protocol_gproxii_get_data(ProtocolGProxII* protocol) {
return protocol->decoded_data;
}

bool wiegand_check(uint64_t fc_and_card, bool even_parity, bool odd_parity, int card_len) {
uint8_t even_parity_sum = 0;
uint8_t odd_parity_sum = 1;
switch(card_len) {
case 26:
for(int8_t i = 12; i < 24; i++) {
if(((fc_and_card >> i) & 1) == 1) {
even_parity_sum++;
}
}
if(even_parity_sum % 2 != even_parity) return false;

for(int8_t i = 0; i < 12; i++) {
if(((fc_and_card >> i) & 1) == 1) {
odd_parity_sum++;
}
}
if(odd_parity_sum % 2 != odd_parity) return false;
break;
case 36:
for(int8_t i = 17; i < 34; i++) {
if(((fc_and_card >> i) & 1) == 1) {
even_parity_sum++;
}
}
if(even_parity_sum % 2 != even_parity) return false;

for(int8_t i = 0; i < 17; i++) {
if(((fc_and_card >> i) & 1) == 1) {
odd_parity_sum++;
}
}
if(odd_parity_sum % 2 != odd_parity) return false;
break;
default:
furi_crash();
}
return true;
}

void protocol_gproxii_decoder_start(ProtocolGProxII* protocol) {
Expand Down Expand Up @@ -74,13 +114,13 @@ static bool protocol_gproxii_can_be_decoded(ProtocolGProxII* protocol) {
// XORVALUE LLLLLL DD PPPPPPPPPPPPPPPP E FFFFFFFF CCCCCCCCCCCCCCCC O UUUUUUUUUUUUUU
// 10010000 011010 11 0000000100000000 0 00000000 0000000000000001 0 00000000000000 - Profile: 256 FC: 0 Card: 1

// 72 Bit Guardall/Verex/Chubb GProx II 36 bit key with 26 bit profile
// 0 10 20 30 40 50 60 70
// | | | | | | | |
// 01234567 890123 45 67890123456789012345678901 2 34567890 1234567890123456 7 8901
// 72 Bit Guardall/Verex/Chubb GProx II 36 bit key with 16 bit profile
// 0 10 20 30 40 50 60 70
// | | | | | | | |
// 01234567 890123 45 67890123 45678901 2 34567890123456 78901234567890123456 7 8901
// --------------------------------------------------------------------------------
// XORVALUE LLLLLL DD PPPPPPPPPPPPPPPPPPPPPPPPPP E FFFFFFFF CCCCCCCCCCCCCCCC O UUUU
// 10111000 100100 10 00000001000000000000000000 1 01000000 1000100010111000 1 0000 - Profile: 262144 FC: 64 Card: 35000
// XORVALUE LLLLLL DD PPPPPPPP PPPPPPPP E UUUUUUFFFFFFFF UUUUCCCCCCCCCCCCCCCC O UUUU
// 10111000 100100 10 00000001 00000000 0 00000000010100 00001000100010111000 1 0000 - Profile: 256 FC: 20 Card: 35000

// X = XOR Key, L = Message length, D = 2 bit check digits, P = Profile, E = Wiegand leading even parity
// F = Faclity code, C = Card number, O = Wiegand trailing odd parity, U = Unused bits
Expand Down Expand Up @@ -111,11 +151,23 @@ static bool protocol_gproxii_can_be_decoded(ProtocolGProxII* protocol) {

// Check card length is either 26 or 36
int card_len = bit_lib_get_bits(protocol->decoded_data, 8, 6);
if(card_len == 26 || card_len == 36) {
return true;

// wiegand parity
if(card_len == 26) {
uint64_t fc_and_card = bit_lib_get_bits_64(protocol->decoded_data, 33, 24);
bool even_parity = bit_lib_get_bits(protocol->decoded_data, 32, 1);
bool odd_parity = bit_lib_get_bits(protocol->decoded_data, 57, 1);
if(!wiegand_check(fc_and_card, even_parity, odd_parity, card_len)) return false;
} else if(card_len == 36) {
uint64_t fc_and_card = bit_lib_get_bits_64(protocol->decoded_data, 33, 34);
uint8_t even_parity = bit_lib_get_bits(protocol->decoded_data, 32, 1);
uint8_t odd_parity = bit_lib_get_bits(protocol->decoded_data, 67, 1);
if(!wiegand_check(fc_and_card, even_parity, odd_parity, card_len)) return false;
} else {
return false; // If we don't get a 26 or 36 it's not a known card type
}

return true;
}

bool protocol_gproxii_decoder_feed(ProtocolGProxII* protocol, bool level, uint32_t duration) {
Expand Down Expand Up @@ -191,7 +243,7 @@ void protocol_gproxii_render_data(ProtocolGProxII* protocol, FuriString* result)
// Print FC, Card and Length
furi_string_cat_printf(
result,
"FC: %hhu Card: %hu LEN: %hhu\n",
"FC: %u Card: %u LEN: %hhu\n",
bit_lib_get_bits(protocol->decoded_data, 33, 8),
bit_lib_get_bits_16(protocol->decoded_data, 41, 16),
card_len);
Expand All @@ -206,17 +258,17 @@ void protocol_gproxii_render_data(ProtocolGProxII* protocol, FuriString* result)
// Print FC, Card and Length
furi_string_cat_printf(
result,
"FC: %hhu Card: %hu LEN: %hhu\n",
bit_lib_get_bits(protocol->decoded_data, 43, 8),
"FC: %u Card: %u LEN: %hhu\n",
bit_lib_get_bits_16(protocol->decoded_data, 33, 14),
bit_lib_get_bits_16(protocol->decoded_data, 51, 16),
card_len);
// XOR Key, CRC and Profile
furi_string_cat_printf(
result,
"XOR: %hhu CRC: %hhu P: %06lX",
"XOR: %hhu CRC: %hhu P: %04hX",
xor_code,
crc_code,
bit_lib_get_bits_32(protocol->decoded_data, 16, 26));
bit_lib_get_bits_16(protocol->decoded_data, 16, 16));
} else {
furi_string_cat_printf(result, "Read Error\n");
}
Expand Down

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