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Parsing function readability refactor
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@zacharyweiss
zacharyweiss committed Apr 8, 2024
1 parent 3af66c7 commit 3ea6d46
Showing 1 changed file with 120 additions and 117 deletions.
237 changes: 120 additions & 117 deletions applications/main/nfc/plugins/supported_cards/charliecard.c
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Original file line number Diff line number Diff line change
Expand Up @@ -23,8 +23,6 @@
* — Reverse engineer passes (sectors 4 & 5?), impl.
* — Infer transaction flag meanings
* — Infer remaining unknown bytes in the balance sectors (2 & 3)
* – ASCII art &/or unified read function for the balance sectors,
* to improve readability / interpretability by others?
* — Improve string output formatting, esp. of transaction log
* — Mapping of buses to garages, and subsequently, route subsets via
* http://roster.transithistory.org/ data
Expand Down Expand Up @@ -99,11 +97,6 @@
#define CHARLIE_N_TRIP_HISTORY 10
#define CHARLIE_N_PASSES 4

enum CharlieActiveSector {
CHARLIE_ACTIVE_SECTOR_2,
CHARLIE_ACTIVE_SECTOR_3,
};

typedef struct {
uint64_t a;
uint64_t b;
Expand Down Expand Up @@ -163,6 +156,18 @@ typedef struct {
DateTime end;
} Pass;

typedef struct {
uint16_t n_uses;
uint8_t active_balance_sector;
} CounterSector;

typedef struct {
Money balance;
uint16_t type;
DateTime issued;
DateTime end_validity;
} BalanceSector;

// IdMapping approach borrowed from Jeremy Cooper's 'clipper.c'
typedef struct {
uint16_t id;
Expand Down Expand Up @@ -656,7 +661,7 @@ static bool is_debug() {
}

// **********************************************************
// ********************* DATA PARSING ***********************
// ******************** FIELD PARSING ***********************
// **********************************************************

static Money money_parse(
Expand All @@ -677,46 +682,6 @@ static DateTime
return dt_delta(CHARLIE_EPOCH, ts_charlie * CHARLIE_TIME_DELTA_SECS);
}

static uint16_t n_uses(const MfClassicData* data, const enum CharlieActiveSector active_sector) {
/* First two bytes of applicable block (sector 1, block 1 or 2 depending on active_sector)
The *lower* of the two values *minus one* is the true use count,
per DEFCON31 researcher's findings
*/
return pos_to_num(data, 1, 1 + active_sector, 0, 2) - 1;
}

static enum CharlieActiveSector get_active_sector(const MfClassicData* data) {
/* Card has two transaction sectors (2 & 3) containing balance data, with two
corresponding trip counters in 0x50:0x51 & 0x60:0x61 (sector 1, byte 0:1 of blocks 1 & 2).
The *lower* count variable corresponds to the active sector
(0x5_ lower -> 2 active, 0x6_ lower -> 3 active)
Sectors 2 & 3 are (largely) identical, save for trip data.
Card seems to alternate between the two, with active sector storing
the current balance & recent trip/transaction, & the inactive sector storing
the N-1 trip/transaction version of the same data.
Here I check both the trip count and the stored transaction date,
for my own sanity, to confirm the active sector.
*/

// active sector based on trip counters
const bool active_trip = n_uses(data, CHARLIE_ACTIVE_SECTOR_2) <=
n_uses(data, CHARLIE_ACTIVE_SECTOR_3);

// active sector based on transaction date
DateTime ds2 = date_parse(data, 2, 0, 1);
DateTime ds3 = date_parse(data, 3, 0, 1);
const bool active_date = datetime_datetime_to_timestamp(&ds2) >=
datetime_datetime_to_timestamp(&ds3);

// with all tested cards so far, this has been true
furi_assert(active_trip == active_date);

return active_trip ? CHARLIE_ACTIVE_SECTOR_2 : CHARLIE_ACTIVE_SECTOR_3;
}

static uint16_t type_parse(const MfClassicData* data) {
/* Card type data stored in the first 10bits of block 1 of sectors 2 & 3 (Block 9 & Block 13, from card start)
To my knowledge, card type should never change, so we can check either
Expand Down Expand Up @@ -745,12 +710,6 @@ static DateTime end_validity_parse(
return dt_delta(CHARLIE_EPOCH, ts_charlie_ev * CHARLIE_END_VALID_DELTA_SECS);
}

static DateTime
main_end_validity_parse(const MfClassicData* data, enum CharlieActiveSector active_sec) {
// primary card type end validity; checked in active sector (probably the same across both 2 & 3)
return end_validity_parse(data, (active_sec == CHARLIE_ACTIVE_SECTOR_2) ? 2 : 3, 1, 1);
}

static Pass
pass_parse(const MfClassicData* data, uint8_t sector_num, uint8_t block_num, uint8_t byte_num) {
// WIP; testing only. Speculating it may be structured as follows
Expand Down Expand Up @@ -814,53 +773,100 @@ static Trip
return (Trip){date, gate, g_flag, fare, f_flag};
}

// Manufacturer data (Sector 0)
//
// 0 1 2 3 4 5 6 7 8 9 A B C D E F
// +----.----.----.----+----+----.----.----.----+----+----.----.----.----.----+----+
// 0x000 | UID |LRC | 88 04 00 C8 |unkn| 00 20 00 00 00 |unkn|
// +----.----.----.----+----+----.----.----.----+----+----.----.----.----.----+----+
// 0x010 | 4E 0F 04 10 04 10 04 10 04 10 04 10 04 10 04 10 |
// +----.----.----.----.----.----.----.----.----.----.----.----.----.----.----.----+
// 0x020 | ... 00 00 ... |
// +----.----.----.----.----.----.----.----.----.----.----.----.----.----.----.----+

// Trip/transaction counters (Sector 1)
//
// 0 1 2 3 4 5 6 7 8 9 A B C D E F
// +----.----.----.----.----.----.----.----.----.----.----.----.----.----.----+----+
// 0x040 | 04 10 23 45 66 77 ... 00 00 ... |
// +----.----+----+----.----.----.----.----.----.----.----.----.----.----.----+----+
// 0x050 | uses1 |unkn| ... 00 00 ... |
// +----.----+----+----.----.----.----.----.----.----.----.----.----.----.----.----+
// 0x060 | uses2 |unkn| ... 00 00 ... |
// +----.----+----+----.----.----.----.----.----.----.----.----.----.----.----.----+

// Balance / type / last transaction (Sector 2 & 3)
//
// 0 1 2 3 4 5 6 7 8 9 A B C D E F
// +----+----.----.----+----.----+----.----.----+----.----+----.----+----+----.----+
// 0x080 | 11 | date last | loc last| date issued | 65 00 | unknown | 00 | crc |
// +----+----.----.----+----+----+----+----+----+----.----+----.----+----+----.----+
// 0x090 | type |end validity|unkn| balance | 00 | unknown | crc |
// +----.----.----.----+----+----.----+----+----.----.----.----.----.----+----.----+
// 0x0A0 | 20 ... 00 00 ... 04 | crc |
// +----.----.----.----.----.----.----.----.----.----.----.----.----.----+----.----+
// **********************************************************
// ******************* SECTOR PARSING ***********************
// **********************************************************

static uint32_t mfg_sector_parse(const MfClassicData* data) {
// Manufacturer data (Sector 0)
//
// 0 1 2 3 4 5 6 7 8 9 A B C D E F
// +----.----.----.----+----+----.----.----.----+----+----.----.----.----.----+----+
// 0x000 | UID |LRC | 88 04 00 C8 |unkn| 00 20 00 00 00 |unkn|
// +----.----.----.----+----+----.----.----.----+----+----.----.----.----.----+----+
// 0x010 | 4E 0F 04 10 04 10 04 10 04 10 04 10 04 10 04 10 |
// +----.----.----.----.----.----.----.----.----.----.----.----.----.----.----.----+
// 0x020 | ... 00 00 ... |
// +----.----.----.----.----.----.----.----.----.----.----.----.----.----.----.----+

size_t uid_len = 0;
const uint8_t* uid = mf_classic_get_uid(data, &uid_len);
const uint32_t card_number = bit_lib_bytes_to_num_be(uid, 4);

return card_number;
}

static CounterSector counter_sector_parse(const MfClassicData* data) {
// Trip/transaction counters (Sector 1)
//
// 0 1 2 3 4 5 6 7 8 9 A B C D E F
// +----.----.----.----.----.----.----.----.----.----.----.----.----.----.----+----+
// 0x040 | 04 10 23 45 66 77 ... 00 00 ... |
// +----.----+----+----.----.----.----.----.----.----.----.----.----.----.----+----+
// 0x050 | uses1 |unkn| ... 00 00 ... |
// +----.----+----+----.----.----.----.----.----.----.----.----.----.----.----.----+
// 0x060 | uses2 |unkn| ... 00 00 ... |
// +----.----+----+----.----.----.----.----.----.----.----.----.----.----.----.----+

// Card has two transaction sectors (2 & 3) containing balance data, with two
// corresponding trip counters in 0x50:0x51 & 0x60:0x61 (sector 1, byte 0:1 of blocks 1 & 2).

// The *lower* of the two values *minus one* is the true use count,
// and corresponds to the active balance sector,
// (0x50 counter lower -> sector 2 active, 0x60 counter lower -> 3 active)
// per DEFCON31 researcher's findings

const uint16_t n_uses1 = pos_to_num(data, 1, 1, 0, 2);
const uint16_t n_uses2 = pos_to_num(data, 1, 2, 0, 2);

const bool is_sec2_active = n_uses1 <= n_uses2;
const uint8_t active_sector = is_sec2_active ? 2 : 3;
const uint16_t n_uses = (is_sec2_active ? n_uses1 : n_uses2) - 1;

return (CounterSector){n_uses, active_sector};
}

static BalanceSector balance_sector_parse(const MfClassicData* data, uint8_t active_sector) {
// Balance / type / last transaction (Sector 2 or 3)
//
// 0 1 2 3 4 5 6 7 8 9 A B C D E F
// +----+----.----.----+----.----+----.----.----+----.----+----.----+----+----.----+
// 0x080 | 11 | date last | loc last| date issued | 65 00 | unknown | 00 | crc | 0x0C0
// +----+----.----.----+----+----+----+----+----+----.----+----.----+----+----.----+
// 0x090 | type |end validity|unkn| balance | 00 | unknown | crc | 0x0D0
// +----.----.----.----+----+----.----+----+----.----.----.----.----.----+----.----+
// 0x0A0 | 20 ... 00 00 ... 04 | crc | 0x0E0
// +----.----.----.----.----.----.----.----.----.----.----.----.----.----+----.----+
//
// "Active" balance sector alternates between 2 and 3
// Last trip/transaction info in balance sector (date last & loc last)
// also included in transaction log, hence don't bother to read here
//
// Inactive balance sector represent the transaction N-1 balance data
// (where active sector represents data from transaction N).

const DateTime issued = date_parse(data, active_sector, 0, 6);
const DateTime end_validity = end_validity_parse(data, active_sector, 1, 1);
const uint16_t type = type_parse(data);
const Money bal = money_parse(data, active_sector, 1, 5);

return (BalanceSector){bal, type, issued, end_validity};
}

static Pass* passes_parse(const MfClassicData* data) {
// WIP. Read in all speculative passes into array
// Sectors 4 & 5 speculated to contain pass data,
// 4 separate fields? active vs inactive sector for 2 passes?
// Sector 4 visualized below; sector 5 layout the same.
// Passes, speculative (Sectors 4 &/or 5)
//
// 0 1 2 3 4 5 6 7 8 9 A B C D E F
// +----.----.----.----.----.-+--.----+----.----.----.----.----.-+--.----+----.----+
// 0x100 | pass0? |0 00 | pass1? |0 00 | crc |
// 0x100 | pass0? |0 00 | pass1? |0 00 | crc | 0x140
// +----.----.----.----.----.-+--.----+----.----.----.----.----.-+--.----+----.----+
// 0x110 | ... 00 00 ... | crc |
// 0x110 | ... 00 00 ... | crc | 0x150
// +----.----.----.----.----.----.----.----.----.----.----.----.----.----+----.----+
// 0x120 | ... 00 ... 05 | crc |
// 0x120 | ... 00 ... 05 | crc | 0x160
// +----.----.----.----.----.----.----.----.----.----.----.----.----.----+----.----+
//
// WIP. Read in all speculative passes into array
// 4 separate fields? active vs inactive sector for 2 passes?

Pass* passes = malloc(sizeof(Pass) * CHARLIE_N_PASSES);

Expand All @@ -872,7 +878,7 @@ static Pass* passes_parse(const MfClassicData* data) {
}

static Trip* trips_parse(const MfClassicData* data) {
// Sectors 6 & 7 store the last 10 trips. Overall layout as follows:
// Transaction history (Sectors 6–7)
//
// 0 1 2 3 4 5 6 7 8 9 A B C D E F
// +----.----.----.----.----.----.----+----.----.----.----.----.----.----+----.----+
Expand All @@ -885,7 +891,8 @@ static Trip* trips_parse(const MfClassicData* data) {
// 0x1E0 | ... 00 00 ... | crc |
// +----.----.----.----.----.----.----.----.----.----.----.----.----.----+----.----+
//
//Trips are not sorted, rather, appear to get overwritten sequentially. (eg, sorted modulo array rotation)
// Transactions are not sorted, rather, appear to get overwritten
// sequentially. (eg, sorted modulo array rotation)

Trip* trips = malloc(sizeof(Trip) * CHARLIE_N_TRIP_HISTORY);

Expand Down Expand Up @@ -958,7 +965,7 @@ static DateTime expiry(DateTime iss) {
}
return exp;
}*/
}
static bool expired(DateTime expiry, DateTime last_trip) {
// if a card has sat unused for >2 years, expired (verify this claim?)
Expand All @@ -970,6 +977,7 @@ static bool expired(DateTime expiry, DateTime last_trip) {
return (ts_exp <= ts_now) | ((ts_now - ts_last) >= (2 * 365 * 24 * 60 * 60));
}
*/

// **********************************************************
// ****************** STRING FORMATTING *********************
Expand Down Expand Up @@ -1011,7 +1019,7 @@ void pass_format_cat(FuriString* out, Pass pass) {

void passes_format_cat(FuriString* out, Pass* passes) {
if(is_debug()) {
furi_string_cat_printf(out, "\nPasses (DEBUG & WIP):");
furi_string_cat_printf(out, "\nPasses (DEBUG / WIP):");
for(size_t i = 0; i < CHARLIE_N_PASSES; i++) {
if(passes[i].valid) {
furi_string_cat_printf(out, "\nPass %u", i + 1);
Expand Down Expand Up @@ -1091,43 +1099,38 @@ static bool charliecard_parse(const NfcDevice* device, FuriString* parsed_data)

// TODO: Verify add'l?

const enum CharlieActiveSector active_sec_enum = get_active_sector(data);
const uint8_t active_sector = (active_sec_enum == CHARLIE_ACTIVE_SECTOR_2) ? 2 : 3;
// parse card data
const uint32_t card_number = mfg_sector_parse(data);
const CounterSector counter_sector = counter_sector_parse(data);
const BalanceSector balance_sector =
balance_sector_parse(data, counter_sector.active_balance_sector);
Pass* passes = passes_parse(data);
Trip* trips = trips_parse(data);

// print/append card data
furi_string_cat_printf(parsed_data, "\e#CharlieCard");

size_t uid_len = 0;
const uint8_t* uid = mf_classic_get_uid(data, &uid_len);
uint32_t card_number = bit_lib_bytes_to_num_be(uid, 4);
furi_string_cat_printf(parsed_data, "\nSerial: 5-%lu", card_number);

Money bal = money_parse(data, active_sector, 1, 5);
furi_string_cat_printf(parsed_data, "\nBal: ");
money_format_cat(parsed_data, bal);
money_format_cat(parsed_data, balance_sector.balance);

const uint16_t type = type_parse(data);
furi_string_cat_printf(parsed_data, "\nType: ");
type_format_cat(parsed_data, type);
type_format_cat(parsed_data, balance_sector.type);

Pass* passes = passes_parse(data);
passes_format_cat(parsed_data, passes);
free(passes);

const uint16_t n_trips = n_uses(data, active_sec_enum);
furi_string_cat_printf(parsed_data, "\nTrip Count: %u", n_trips);
furi_string_cat_printf(parsed_data, "\nTrip Count: %u", counter_sector.n_uses);

const DateTime iss = date_parse(data, active_sector, 0, 6);
furi_string_cat_printf(parsed_data, "\nIssued: ");
locale_format_dt_cat(parsed_data, &iss);
locale_format_dt_cat(parsed_data, &balance_sector.issued);

const DateTime e_v = main_end_validity_parse(data, active_sec_enum);
furi_string_cat_printf(parsed_data, "\nExpiry: ");
locale_format_dt_cat(parsed_data, &e_v);
locale_format_dt_cat(parsed_data, &balance_sector.end_validity);

DateTime last = date_parse(data, active_sector, 0, 1);
furi_string_cat_printf(parsed_data, "\nExpired: %s", expired(e_v, last) ? "Yes" : "No");
// const DateTime last = date_parse(data, active_sector, 0, 1);
// furi_string_cat_printf(parsed_data, "\nExpired: %s", expired(e_v, last) ? "Yes" : "No");

Trip* trips = trips_parse(data);
trips_format_cat(parsed_data, trips);
free(trips);

Expand Down

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