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emrtd: Improve emrtd_lds_get_data_by_tag to account for variable data sizes

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Ave 2020-12-17 22:22:26 +03:00
commit a9f28adabf
1 changed files with 9 additions and 4 deletions
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13
client/src/cmdhfemrtd.c
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@ -569,9 +569,11 @@ static int emrtd_read_file(uint8_t *dataout, int *dataoutlen, uint8_t *kenc, uin
} }
static bool emrtd_lds_get_data_by_tag(uint8_t *datain, int *datainlen, uint8_t *dataout, int *dataoutlen, int tag1, int tag2, bool twobytetag) { static bool emrtd_lds_get_data_by_tag(uint8_t *datain, int *datainlen, uint8_t *dataout, int *dataoutlen, int tag1, int tag2, bool twobytetag) {
int offset = 2; int offset = 1;
offset += emrtd_get_asn1_field_length(datain, *datainlen, offset);
int elementidlen = 0; int elementidlen = 0;
int elementlen = 0; int elementlen = 0;
int elementlenlen = 0;
while (offset < *datainlen) { while (offset < *datainlen) {
PrintAndLogEx(DEBUG, "emrtd_lds_get_data_by_tag, offset: %i, data: %X", offset, *(datain + offset)); PrintAndLogEx(DEBUG, "emrtd_lds_get_data_by_tag, offset: %i, data: %X", offset, *(datain + offset));
// Determine element ID length to set as offset on asn1datalength // Determine element ID length to set as offset on asn1datalength
@ -584,13 +586,16 @@ static bool emrtd_lds_get_data_by_tag(uint8_t *datain, int *datainlen, uint8_t *
// Get the length of the element // Get the length of the element
elementlen = emrtd_get_asn1_data_length(datain + offset, *datainlen - offset, elementidlen); elementlen = emrtd_get_asn1_data_length(datain + offset, *datainlen - offset, elementidlen);
// Get the length of the element's length
elementlenlen = emrtd_get_asn1_field_length(datain + offset, *datainlen - offset, elementidlen);
// If the element is what we're looking for, get the data and return true // If the element is what we're looking for, get the data and return true
if (*(datain + offset) == tag1 && (!twobytetag || *(datain + offset + 1) == tag2)) { if (*(datain + offset) == tag1 && (!twobytetag || *(datain + offset + 1) == tag2)) {
*dataoutlen = elementlen; *dataoutlen = elementlen;
memcpy(dataout, datain + offset + elementidlen + 1, elementlen); memcpy(dataout, datain + offset + elementidlen + elementlenlen, elementlen);
return true; return true;
} }
offset += elementidlen + elementlen + 1; offset += elementidlen + elementlen + elementlenlen;
} }
// Return false if we can't find the relevant element // Return false if we can't find the relevant element
return false; return false;
@ -894,7 +899,7 @@ static bool emrtd_do_auth(char *documentnumber, char *dob, char *expiry, bool BA
// If BAC isn't available, exit out and warn user. // If BAC isn't available, exit out and warn user.
if (!BAC_available) { if (!BAC_available) {
PrintAndLogEx(ERR, "This eMRTD enforces Basic Access Control, but you didn't supply MRZ data. Cannot proceed."); PrintAndLogEx(ERR, "This eMRTD enforces Basic Access Control, but you didn't supply MRZ data. Cannot proceed.");
PrintAndLogEx(HINT, "Check out hf emrtd dump --help, supply data with -n -d and -e."); PrintAndLogEx(HINT, "Check out hf emrtd info/dump --help, supply data with -n -d and -e.");
return false; return false;
} }