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Stringify Card Status Update (CSU) field
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This field does not have a tag identifier and instead occurs inside
other fields such as the Issuer Authentication Data (field 91).
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@leonlynch
leonlynch committed Apr 27, 2024
1 parent 54c0e6e commit 2924b63
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Showing 3 changed files with 115 additions and 8 deletions.
28 changes: 28 additions & 0 deletions src/emv_fields.h
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Original file line number Diff line number Diff line change
Expand Up @@ -759,6 +759,34 @@ enum emv_iad_format_t {
#define AMEX_ENH_CL_READER_CAPS_KERNEL_VERSION_24_26 (0x02) ///< Enhanced Contactless Reader Capabilities: C-4 kernel version 2.4 - 2.6
#define AMEX_ENH_CL_READER_CAPS_KERNEL_VERSION_27 (0x03) ///< Enhanced Contactless Reader Capabilities: C-4 kernel version 2.7

// Card Status Update (CSU) byte 1
// See EMV 4.4 Book 3, Annex C10
#define EMV_CSU_BYTE1_PROPRIETARY_AUTHENTICATION_DATA_INCLUDED (0x80) ///< Card Status Update (CSU): Proprietary Authentication Data Included
#define EMV_CSU_BYTE1_RFU (0x70) ///< Card Status Update (CSU): RFU
#define EMV_CSU_BYTE1_PIN_TRY_COUNTER_MASK (0x0F) ///< Card Status Update (CSU) mask for PIN Try Counter

// Card Status Update (CSU) byte 2
// See EMV 4.4 Book 3, Annex C10
#define EMV_CSU_BYTE2_ISSUER_APPROVES_ONLINE_TRANSACTION (0x80) ///< Card Status Update (CSU): Issuer Approves Online Transaction
#define EMV_CSU_BYTE2_CARD_BLOCK (0x40) ///< Card Status Update (CSU): Card Block
#define EMV_CSU_BYTE2_APPLICATION_BLOCK (0x20) ///< Card Status Update (CSU): Application Block
#define EMV_CSU_BYTE2_UPDATE_PIN_TRY_COUNTER (0x10) ///< Card Status Update (CSU): Update PIN Try Counter
#define EMV_CSU_BYTE2_GO_ONLINE_ON_NEXT_TXN (0x08) ///< Card Status Update (CSU): Set Go Online on Next Transaction
#define EMV_CSU_BYTE2_CREATED_BY_PROXY_FOR_ISSUER (0x04) ///< Card Status Update (CSU): CSU Created by Proxy for the Issuer
#define EMV_CSU_BYTE2_UPDATE_COUNTERS_MASK (0x03) ///< Card Status Update (CSU) mask for Update Counters
#define EMV_CSU_BYTE2_UPDATE_COUNTERS_DO_NOT_UPDATE (0x00) ///< Card Status Update (CSU): Do Not Update Offline Counters
#define EMV_CSU_BYTE2_UPDATE_COUNTERS_UPPER_OFFLINE_LIMIT (0x01) ///< Card Status Update (CSU): Set Offline Counters to Upper Offline Limits
#define EMV_CSU_BYTE2_UPDATE_COUNTERS_RESET (0x02) ///< Card Status Update (CSU): Reset Offline Counters to Zero
#define EMV_CSU_BYTE2_UPDATE_COUNTERS_ADD_TO_OFFLINE (0x03) ///< Card Status Update (CSU): Add Transaction to Offline Counter

// Card Status Update (CSU) byte 3
// See EMV 4.4 Book 3, Annex C10
#define EMV_CSU_BYTE3_RFU (0xFF) ///< Card Status Update (CSU): RFU

// Card Status Update (CSU) byte 4
// See EMV 4.4 Book 3, Annex C10
#define EMV_CSU_BYTE4_ISSUER_DISCRETIONARY (0xFF) ///< Card Status Update (CSU): Issuer Discretionary

/// EMV card schemes
enum emv_card_scheme_t {
EMV_CARD_SCHEME_UNKNOWN = 0, ///< Unknown card scheme
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92 changes: 85 additions & 7 deletions src/emv_strings.c
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Original file line number Diff line number Diff line change
Expand Up @@ -67,6 +67,7 @@ static int emv_iad_vsdc_0_1_3_append_string_list(const uint8_t* iad, size_t iad_
static int emv_iad_vsdc_2_4_append_string_list(const uint8_t* iad, size_t iad_len, struct str_itr_t* itr);
static const char* emv_mastercard_device_type_get_string(const char* device_type);
static const char* emv_arc_get_desc(const char* arc);
static int emv_csu_append_string_list(const uint8_t* csu, size_t csu_len, struct str_itr_t* itr);
static int emv_capdu_get_data_get_string(const uint8_t* c_apdu, size_t c_apdu_len, char* str, size_t str_len);

int emv_strings_init(const char* isocodes_path, const char* mcc_path)
Expand Down Expand Up @@ -5775,6 +5776,79 @@ int emv_auth_response_code_get_string(
return 0;
}

static int emv_csu_append_string_list(
const uint8_t* csu,
size_t csu_len,
struct str_itr_t* itr
)
{
if (!csu) {
return -1;
}
if (csu_len != 4) {
// See EMV 4.4 Book 3, Annex C10
return -2;
}

// Card Status Update (CSU) byte 1
// See EMV 4.4 Book 3, Annex C10
if (csu[0] & EMV_CSU_BYTE1_PROPRIETARY_AUTHENTICATION_DATA_INCLUDED) {
emv_str_list_add(itr, "Card Status Update (CSU): Proprietary Authentication Data Included");
}
if (csu[0] & EMV_CSU_BYTE1_PIN_TRY_COUNTER_MASK) {
emv_str_list_add(itr, "Card Status Update (CSU): PIN Try Counter = %u", csu[0] & EMV_CSU_BYTE1_PIN_TRY_COUNTER_MASK);
}

// Card Status Update (CSU) byte 2
// See EMV 4.4 Book 3, Annex C10
if (csu[1] & EMV_CSU_BYTE2_ISSUER_APPROVES_ONLINE_TRANSACTION) {
emv_str_list_add(itr, "Card Status Update (CSU): Issuer Approves Online Transaction");
}
if (csu[1] & EMV_CSU_BYTE2_CARD_BLOCK) {
emv_str_list_add(itr, "Card Status Update (CSU): Card Block");
}
if (csu[1] & EMV_CSU_BYTE2_APPLICATION_BLOCK) {
emv_str_list_add(itr, "Card Status Update (CSU): Application Block");
}
if (csu[1] & EMV_CSU_BYTE2_UPDATE_PIN_TRY_COUNTER) {
emv_str_list_add(itr, "Card Status Update (CSU): Update PIN Try Counter");
}
if (csu[1] & EMV_CSU_BYTE2_GO_ONLINE_ON_NEXT_TXN) {
emv_str_list_add(itr, "Card Status Update (CSU): Set Go Online on Next Transaction");
}
if (csu[1] & EMV_CSU_BYTE2_CREATED_BY_PROXY_FOR_ISSUER) {
emv_str_list_add(itr, "Card Status Update (CSU): CSU Created by Proxy for the Issuer");
}
if ((csu[1] & EMV_CSU_BYTE2_UPDATE_COUNTERS_MASK) == EMV_CSU_BYTE2_UPDATE_COUNTERS_DO_NOT_UPDATE) {
emv_str_list_add(itr, "Card Status Update (CSU): Do Not Update Offline Counters");
}
if ((csu[1] & EMV_CSU_BYTE2_UPDATE_COUNTERS_MASK) == EMV_CSU_BYTE2_UPDATE_COUNTERS_UPPER_OFFLINE_LIMIT) {
emv_str_list_add(itr, "ard Status Update (CSU): Set Offline Counters to Upper Offline Limits");
}
if ((csu[1] & EMV_CSU_BYTE2_UPDATE_COUNTERS_MASK) == EMV_CSU_BYTE2_UPDATE_COUNTERS_RESET) {
emv_str_list_add(itr, "Card Status Update (CSU): Reset Offline Counters to Zero");
}
if ((csu[1] & EMV_CSU_BYTE2_UPDATE_COUNTERS_MASK) == EMV_CSU_BYTE2_UPDATE_COUNTERS_ADD_TO_OFFLINE) {
emv_str_list_add(itr, "Card Status Update (CSU): Add Transaction to Offline Counter");
}

// Card Status Update (CSU) byte 4
// See EMV 4.4 Book 3, Annex C10
if (csu[3] & EMV_CSU_BYTE4_ISSUER_DISCRETIONARY) {
emv_str_list_add(itr, "Card Status Update (CSU): Issuer Discretionary 0x%02X", csu[3]);
}

// Card Status Update (CSU) RFU bits
// See EMV 4.4 Book 3, Annex C10
if (csu[0] & EMV_CSU_BYTE1_RFU ||
csu[2] & EMV_CSU_BYTE3_RFU
) {
emv_str_list_add(itr, "Card Status Update (CSU): RFU");
}

return 0;
}

int emv_issuer_auth_data_get_string_list(
const uint8_t* iad,
size_t iad_len,
Expand Down Expand Up @@ -5830,18 +5904,22 @@ int emv_issuer_auth_data_get_string_list(
return 0;
}
}
if ((iad[4] & 0x70) == 0 && iad[6] == 0) { // Check for Visa CSU RFU bits
// Likely Visa CVN18 or Visa CVN'22'
// 4-byte ARPC followed by CSU and optional Proprietary Authentication Data
// Check for Card Status Update (CSU) RFU bits
if ((iad[4] & EMV_CSU_BYTE1_RFU) == 0 &&
(iad[6] & EMV_CSU_BYTE3_RFU) == 0
) {
// Likely CCD, Visa CVN18 or Visa CVN'22'
// 4-byte ARPC followed by 4-byte CSU and optional Proprietary Authentication Data
// See EMV 4.4 Book 2, 8.2.2
// See EMV 4.4 Book 3, Annex C10
// See Visa Contactless Payment Specification (VCPS) Supplemental Requirements, version 2.2, January 2016, Annex D
emv_str_list_add(&itr, "Authorisation Response Cryptogram (ARPC): %02X%02X%02X%02X",
iad[0], iad[1], iad[2], iad[3]
);
emv_str_list_add(&itr, "Card Status Update (CSU): %02X%02X%02X%02X",
iad[4], iad[5], iad[6], iad[7]
);
emv_csu_append_string_list(iad + 4, 4, &itr);

if (iad_len > 8) { // If extra data after CSU
if ((iad[4] & 0x80) == 0x80) { // CSU indicates Proprietary Authentication Data
if ((iad[4] & EMV_CSU_BYTE1_PROPRIETARY_AUTHENTICATION_DATA_INCLUDED)) { // CSU indicates Proprietary Authentication Data
emv_str_list_add(&itr, "Proprietary Authentication Data: %zu bytes", iad_len - 8);
} else if (iad_len == 10) {
// Two extra bytes but not Proprietary Authentication Data
Expand Down
3 changes: 2 additions & 1 deletion tools/CMakeLists.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -642,7 +642,8 @@ if(TARGET emv-decode AND BUILD_TESTING)
"8A \\| Authorisation Response Code : \\[2\\] 30 30 \"00 - Approved or completed successfully\"[\r\n]"
"91 \\| Issuer Authentication Data : \\[8\\] A5 84 F9 49 00 82 00 00[\r\n]"
" - Authorisation Response Cryptogram \\(ARPC\\): A584F949[\r\n]"
" - Card Status Update \\(CSU\\): 00820000[\r\n]"
" - Card Status Update \\(CSU\\): Issuer Approves Online Transaction[\r\n]"
" - Card Status Update \\(CSU\\): Reset Offline Counters to Zero[\r\n]"
)
set_tests_properties(emv_decode_issuer_response_test2
PROPERTIES
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