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nfc-mfclassic: Add option to specify key
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The nfc-mfclassic utility will pick a seemingly random (the libnfc
default which seems to be the lowest UID). With the new (u|U) options
it is now possible to force a UID and thus write a specific tag, which
can be very useful if there are more then one tag visible.

Signed-off-by: Olliver Schinagl <[email protected]>
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@oliv3r
oliv3r committed May 11, 2016
1 parent 898f3a4 commit e1a25a8
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Showing 2 changed files with 69 additions and 25 deletions.
17 changes: 17 additions & 0 deletions utils/nfc-mfclassic.1
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@ nfc-mfclassic \- MIFARE Classic command line tool
.B nfc-mfclassic
.RI \fR\fBf\fR|\fR\fBr\fR|\fR\fBR\fR|\fBw\fR\fR|\fBW\fR
.RI \fR\fBa\fR|\fR\fBA\fR|\fBb\fR\fR|\fBB\fR
.RI \fR\fBu\fR\fR|\fBU\fR<\fBuid\fR>\fR
.IR DUMP
.RI [
.IR KEYS
Expand Down Expand Up @@ -56,6 +57,15 @@ or
.B B
).

When using multiple tags infront of a reader, the
.B U
option can be used to supply the UID of tag to be read or written. Append the
hexadecimal UID to the U option. For example U01ab23cd for the 4 byte UID
0x01 0xab 0x23 0xcd. Using the
.B u
parameter instead will use whatever libnfc decides which generally is the lowest
UID.

*** Note that
.B W
and
Expand Down Expand Up @@ -90,6 +100,13 @@ Halt on errors (
B
).
.TP
.BR u " | " U
Use the default UID (
.B u
) or supply a valid 4 byte UID (
.B U<uid>
).
.TP
.IR DUMP
MiFare Dump (MFD) used to write (card to MFD) or (MFD to card)
.TP
Expand Down
77 changes: 52 additions & 25 deletions utils/nfc-mfclassic.c
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Original file line number Diff line number Diff line change
Expand Up @@ -491,33 +491,39 @@ static void
print_usage(const char *pcProgramName)
{
printf("Usage: ");
printf("%s f|r|R|w|W a|b <dump.mfd> [<keys.mfd> [f]]\n", pcProgramName);
printf("%s f|r|R|w|W a|b u|U<01ab23cd> <dump.mfd> [<keys.mfd> [f]]\n", pcProgramName);
printf(" f|r|R|w|W - Perform format (f) or read from (r) or unlocked read from (R) or write to (w) or unlocked write to (W) card\n");
printf(" *** format will reset all keys to FFFFFFFFFFFF and all data to 00 and all ACLs to default\n");
printf(" *** unlocked read does not require authentication and will reveal A and B keys\n");
printf(" *** note that unlocked write will attempt to overwrite block 0 including UID\n");
printf(" *** unlocking only works with special Mifare 1K cards (Chinese clones)\n");
printf(" a|A|b|B - Use A or B keys for action; Halt on errors (a|b) or tolerate errors (A|B)\n");
printf(" u|U - Use any (u) uid or supply a uid specifically as U01ab23cd.\n");
printf(" <dump.mfd> - MiFare Dump (MFD) used to write (card to MFD) or (MFD to card)\n");
printf(" <keys.mfd> - MiFare Dump (MFD) that contain the keys (optional)\n");
printf(" f - Force using the keyfile even if UID does not match (optional)\n");
printf("Examples: \n\n");
printf(" Read card to file, using key A:\n\n");
printf(" %s r a mycard.mfd\n\n", pcProgramName);
printf(" %s r a u mycard.mfd\n\n", pcProgramName);
printf(" Write file to blank card, using key A:\n\n");
printf(" %s w a mycard.mfd\n\n", pcProgramName);
printf(" %s w a u mycard.mfd\n\n", pcProgramName);
printf(" Write new data and/or keys to previously written card, using key A:\n\n");
printf(" %s w a newdata.mfd mycard.mfd\n\n", pcProgramName);
printf(" %s w a u newdata.mfd mycard.mfd\n\n", pcProgramName);
printf(" Format/wipe card (note two passes required to ensure writes for all ACL cases):\n\n");
printf(" %s f A dummy.mfd keyfile.mfd f\n", pcProgramName);
printf(" %s f B dummy.mfd keyfile.mfd f\n\n", pcProgramName);
printf(" %s f A u dummy.mfd keyfile.mfd f\n", pcProgramName);
printf(" %s f B u dummy.mfd keyfile.mfd f\n\n", pcProgramName);
printf(" Read card to file, using key A and uid 0x01 0xab 0x23 0xcd:\n\n");
printf(" %s r a U01ab23cd mycard.mfd\n\n", pcProgramName);
}

int
main(int argc, const char *argv[])
{
action_t atAction = ACTION_USAGE;
uint8_t *pbtUID;
uint8_t _tag_uid[4];
uint8_t *tag_uid = _tag_uid;

int unlock = 0;

if (argc < 2) {
Expand All @@ -526,7 +532,7 @@ main(int argc, const char *argv[])
}
const char *command = argv[1];

if (argc < 4) {
if (argc < 5) {
print_usage(argv[0]);
exit(EXIT_FAILURE);
}
Expand All @@ -536,17 +542,35 @@ main(int argc, const char *argv[])
unlock = 1;
bUseKeyA = tolower((int)((unsigned char) * (argv[2]))) == 'a';
bTolerateFailures = tolower((int)((unsigned char) * (argv[2]))) != (int)((unsigned char) * (argv[2]));
bUseKeyFile = (argc > 4);
bForceKeyFile = ((argc > 5) && (strcmp((char *)argv[5], "f") == 0));
bUseKeyFile = (argc > 5);
bForceKeyFile = ((argc > 6) && (strcmp((char *)argv[6], "f") == 0));
} else if (strcmp(command, "w") == 0 || strcmp(command, "W") == 0 || strcmp(command, "f") == 0) {
atAction = ACTION_WRITE;
if (strcmp(command, "W") == 0)
unlock = 1;
bFormatCard = (strcmp(command, "f") == 0);
bUseKeyA = tolower((int)((unsigned char) * (argv[2]))) == 'a';
bTolerateFailures = tolower((int)((unsigned char) * (argv[2]))) != (int)((unsigned char) * (argv[2]));
bUseKeyFile = (argc > 4);
bForceKeyFile = ((argc > 5) && (strcmp((char *)argv[5], "f") == 0));
bUseKeyFile = (argc > 5);
bForceKeyFile = ((argc > 6) && (strcmp((char *)argv[6], "f") == 0));
}
if (argv[3][0] == 'U') {
unsigned long int _uid;

if (strlen(argv[3]) != 9) {
printf("Error, illegal tag specification, use U01ab23cd for example.\n");
print_usage(argv[0]);
exit(EXIT_FAILURE);
}
_uid = strtoul(argv[3] + 1, NULL, 16);
tag_uid[0] = (_uid & 0xff000000UL) >> 24;
tag_uid[1] = (_uid & 0x00ff0000UL) >> 16;
tag_uid[2] = (_uid & 0x0000ff00UL) >> 8;
tag_uid[3] = (_uid & 0x000000ffUL);
printf("Attempting to use specific UID: 0x%2x 0x%2x 0x%2x 0x%2x\n",
tag_uid[0], tag_uid[1], tag_uid[2], tag_uid[3]);
} else {
tag_uid = NULL;
}

if (atAction == ACTION_USAGE) {
Expand All @@ -555,13 +579,13 @@ main(int argc, const char *argv[])
}
// We don't know yet the card size so let's read only the UID from the keyfile for the moment
if (bUseKeyFile) {
FILE *pfKeys = fopen(argv[4], "rb");
FILE *pfKeys = fopen(argv[5], "rb");
if (pfKeys == NULL) {
printf("Could not open keys file: %s\n", argv[4]);
printf("Could not open keys file: %s\n", argv[5]);
exit(EXIT_FAILURE);
}
if (fread(&mtKeys, 1, 4, pfKeys) != 4) {
printf("Could not read UID from key file: %s\n", argv[4]);
printf("Could not read UID from key file: %s\n", argv[5]);
fclose(pfKeys);
exit(EXIT_FAILURE);
}
Expand Down Expand Up @@ -606,7 +630,10 @@ main(int argc, const char *argv[])
printf("NFC reader: %s opened\n", nfc_device_get_name(pnd));

// Try to find a MIFARE Classic tag
if (nfc_initiator_select_passive_target(pnd, nmMifare, NULL, 0, &nt) <= 0) {
int tags;

tags = nfc_initiator_select_passive_target(pnd, nmMifare, tag_uid, tag_uid == NULL ? 0 : 4, &nt);
if (tags <= 0) {
printf("Error: no tag was found\n");
nfc_close(pnd);
nfc_exit(context);
Expand Down Expand Up @@ -668,13 +695,13 @@ main(int argc, const char *argv[])
printf("Guessing size: seems to be a %i-byte card\n", (uiBlocks + 1) * 16);

if (bUseKeyFile) {
FILE *pfKeys = fopen(argv[4], "rb");
FILE *pfKeys = fopen(argv[5], "rb");
if (pfKeys == NULL) {
printf("Could not open keys file: %s\n", argv[4]);
printf("Could not open keys file: %s\n", argv[5]);
exit(EXIT_FAILURE);
}
if (fread(&mtKeys, 1, (uiBlocks + 1) * sizeof(mifare_classic_block), pfKeys) != (uiBlocks + 1) * sizeof(mifare_classic_block)) {
printf("Could not read keys file: %s\n", argv[4]);
printf("Could not read keys file: %s\n", argv[5]);
fclose(pfKeys);
exit(EXIT_FAILURE);
}
Expand All @@ -684,16 +711,16 @@ main(int argc, const char *argv[])
if (atAction == ACTION_READ) {
memset(&mtDump, 0x00, sizeof(mtDump));
} else {
FILE *pfDump = fopen(argv[3], "rb");
FILE *pfDump = fopen(argv[4], "rb");

if (pfDump == NULL) {
printf("Could not open dump file: %s\n", argv[3]);
printf("Could not open dump file: %s\n", argv[4]);
exit(EXIT_FAILURE);

}

if (fread(&mtDump, 1, (uiBlocks + 1) * sizeof(mifare_classic_block), pfDump) != (uiBlocks + 1) * sizeof(mifare_classic_block)) {
printf("Could not read dump file: %s\n", argv[3]);
printf("Could not read dump file: %s\n", argv[4]);
fclose(pfDump);
exit(EXIT_FAILURE);
}
Expand All @@ -703,17 +730,17 @@ main(int argc, const char *argv[])

if (atAction == ACTION_READ) {
if (read_card(unlock)) {
printf("Writing data to file: %s ...", argv[3]);
printf("Writing data to file: %s ...", argv[4]);
fflush(stdout);
FILE *pfDump = fopen(argv[3], "wb");
FILE *pfDump = fopen(argv[4], "wb");
if (pfDump == NULL) {
printf("Could not open dump file: %s\n", argv[3]);
printf("Could not open dump file: %s\n", argv[4]);
nfc_close(pnd);
nfc_exit(context);
exit(EXIT_FAILURE);
}
if (fwrite(&mtDump, 1, (uiBlocks + 1) * sizeof(mifare_classic_block), pfDump) != ((uiBlocks + 1) * sizeof(mifare_classic_block))) {
printf("\nCould not write to file: %s\n", argv[3]);
printf("\nCould not write to file: %s\n", argv[4]);
fclose(pfDump);
nfc_close(pnd);
nfc_exit(context);
Expand Down

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