Implement cardholder application selection loop

This loop reuses the existing application selection test code but will
be refactored once the high level EMV library interface provides an
application selection function.

Author: leonlynch

Diff for: src/emv_app.c

@@ -408,6 +408,41 @@ struct emv_app_t* emv_app_list_pop(struct emv_app_list_t* list)
 	return app;
 }
 
+struct emv_app_t* emv_app_list_remove_index(
+	struct emv_app_list_t* list,
+	unsigned int index
+)
+{
+	struct emv_app_t* prev = NULL;
+
+	if (!emv_app_list_is_valid(list)) {
+		return NULL;
+	}
+
+	for (struct emv_app_t* app = list->front; app != NULL; app = app->next) {
+		if (index == 0) {
+			if (!prev) {
+				// Remove app from front of list
+				return emv_app_list_pop(list);
+			}
+
+			prev->next = app->next;
+			if (!app->next) {
+				// App at back of list
+				list->back = prev;
+			}
+			app->next = NULL;
+			return app;
+		}
+
+		// Advance and remember previous app
+		--index;
+		prev = app;
+	}
+
+	return NULL;
+}
+
 static int emv_app_list_insert(
 	struct emv_app_list_t* list,
 	struct emv_app_t* pos,

Diff for: src/emv_app.h

@@ -167,6 +167,17 @@ int emv_app_list_push(struct emv_app_list_t* list, struct emv_app_t* app);
  */
 struct emv_app_t* emv_app_list_pop(struct emv_app_list_t* list);
 
+/**
+ * Remove EMV application from EMV application list by index
+ * @param list EMV application list
+ * @param index Index (starting from zero) of EMV application to remove
+ * @return EMV application. Use @ref emv_tlv_free() to free memory.
+ */
+struct emv_app_t* emv_app_list_remove_index(
+	struct emv_app_list_t* list,
+	unsigned int index
+);
+
 /**
  * Sort EMV application list according to the priority field
  * @param list EMV application list

Diff for: tools/emv-tool.c

@@ -137,6 +137,9 @@ struct emv_txn_t {
 
 	// ICC data
 	struct emv_tlv_list_t icc;
+
+	// Cardholder application selection required?
+	bool application_selection_required;
 };
 static struct emv_txn_t emv_txn;
 
@@ -388,6 +391,7 @@ int main(int argc, char** argv)
 	size_t reader_idx;
 	uint8_t atr[PCSC_MAX_ATR_SIZE];
 	size_t atr_len = 0;
+	bool first_application_selection_prompt = true;
 
 	if (argc == 1) {
 		// No command line arguments
@@ -539,71 +543,127 @@ int main(int argc, char** argv)
 		goto emv_exit;
 	}
 
-	if (emv_app_list_is_empty(&app_list)) {
-		printf("No supported applications\n");
-		goto emv_exit;
-	}
-
 	printf("Candidate applications:\n");
 	for (struct emv_app_t* app = app_list.front; app != NULL; app = app->next) {
 		print_emv_app(app);
 	}
 
-	if (emv_app_list_selection_is_required(&app_list)) {
+	emv_txn.application_selection_required = emv_app_list_selection_is_required(&app_list);
+	if (emv_txn.application_selection_required) {
 		printf("Cardholder selection is required\n");
 	}
 
-	// HACK: test application selection
-	{
-		char str[1024];
+	do {
+		struct emv_app_t* current_app;
 
-		// Use first application
-		struct emv_app_t* current_app = emv_app_list_pop(&app_list);
-		if (!current_app) {
-			printf("No supported applications\n");
+		// All application selection failures return to the start of the loop
+		// If no applications remain, terminate session
+		// See EMV 4.4 Book 1, 12.4
+		// See EMV 4.4 Book 4, 11.3
+		if (emv_app_list_is_empty(&app_list)) {
+			emv_debug_info("Candidate list empty");
+			printf("OUTCOME: %s\n", emv_outcome_get_string(EMV_OUTCOME_NOT_ACCEPTED));
 			goto emv_exit;
 		}
-		emv_app_list_clear(&app_list);
-
-		uint8_t current_aid[16];
-		size_t current_aid_len = current_app->aid->length;
-		memcpy(current_aid, current_app->aid->value, current_app->aid->length);
-		emv_app_free(current_app);
-		current_app = NULL;
-
-		// Select application
-		print_buf("\nSELECT application", current_aid, current_aid_len);
-		uint8_t fci[EMV_RAPDU_DATA_MAX];
-		size_t fci_len = sizeof(fci);
-		uint16_t sw1sw2;
-		r = emv_ttl_select_by_df_name(&emv_txn.ttl, current_aid, current_aid_len, fci, &fci_len, &sw1sw2);
-		if (r) {
-			printf("Failed to select application; r=%d\n", r);
-			goto emv_exit;
-		}
-		print_buf("FCI", fci, fci_len);
-		print_emv_buf(fci, fci_len, "  ", 0);
-		printf("SW1SW2 = %04hX (%s)\n", sw1sw2, iso7816_sw1sw2_get_string(sw1sw2 >> 8, sw1sw2 & 0xff, str, sizeof(str)));
 
-		if (sw1sw2 != 0x9000) {
-			goto emv_exit;
+		if (emv_txn.application_selection_required) {
+			unsigned int app_count = 0;
+			int r;
+			char s[4]; // two digits, newline and null
+			unsigned int input = 0;
+
+			if (first_application_selection_prompt) {
+				printf("\nSelect application:\n");
+				first_application_selection_prompt = false;
+			} else {
+				// See EMV 4.4 Book 4, 11.3
+				printf("\nTry again:\n");
+			}
+			for (struct emv_app_t* app = app_list.front; app != NULL; app = app->next) {
+				++app_count;
+				printf("%u - %s\n", app_count, app->display_name);
+			}
+			printf("Enter number: ");
+			if (!fgets(s, sizeof(s), stdin)) {
+				printf("Invalid input. Try again.\n");
+				continue;
+			}
+			r = sscanf(s, "%u", &input);
+			if (r != 1) {
+				printf("Invalid input. Try again.\n");
+				continue;
+			}
+			if (!input || input > app_count) {
+				printf("Invalid input. Try again.\n");
+				continue;
+			}
+
+			current_app = emv_app_list_remove_index(&app_list, input - 1);
+
+		} else {
+			// Use first application
+			current_app = emv_app_list_pop(&app_list);
 		}
 
-		// Create EMV application object
-		struct emv_app_t* app;
-		app = emv_app_create_from_fci(fci, fci_len);
-		if (r) {
-			printf("emv_app_populate_from_fci() failed; r=%d\n", r);
-			goto emv_exit;
+		// HACK: test application selection
+		{
+			char str[1024];
+
+			uint8_t current_aid[16];
+			size_t current_aid_len = current_app->aid->length;
+			memcpy(current_aid, current_app->aid->value, current_app->aid->length);
+			emv_app_free(current_app);
+			current_app = NULL;
+
+			// Select application
+			print_buf("\nSELECT application", current_aid, current_aid_len);
+			uint8_t fci[EMV_RAPDU_DATA_MAX];
+			size_t fci_len = sizeof(fci);
+			uint16_t sw1sw2;
+			r = emv_ttl_select_by_df_name(&emv_txn.ttl, current_aid, current_aid_len, fci, &fci_len, &sw1sw2);
+			if (r) {
+				fprintf(stderr, "emv_ttl_select_by_df_name() failed; r=%d\n", r);
+				continue;
+			}
+			print_buf("FCI", fci, fci_len);
+			print_emv_buf(fci, fci_len, "  ", 0);
+			printf("SW1SW2 = %04hX (%s)\n", sw1sw2, iso7816_sw1sw2_get_string(sw1sw2 >> 8, sw1sw2 & 0xff, str, sizeof(str)));
+
+			if (sw1sw2 != 0x9000) {
+				continue;
+			}
+
+			// Create EMV application object
+			struct emv_app_t* app;
+			app = emv_app_create_from_fci(fci, fci_len);
+			if (r) {
+				fprintf(stderr, "emv_app_populate_from_fci() failed; r=%d\n", r);
+				continue;
+			}
+			printf("\n");
+			print_emv_app(app);
+			print_emv_tlv_list(&app->tlv_list);
+
+			// TODO: EMV 4.4 Book 1, 12.4, ensure that 84 matches SELECT command
+
+			// Capture ICC data
+			emv_txn.icc = app->tlv_list;
+			app->tlv_list = EMV_TLV_LIST_INIT;
+			emv_app_free(app);
+
+			// Application selection was successful
+			// TODO: EMV 4.4 Book 1, 12.4, create 9F06 from 84
+			break;
 		}
-		printf("\n");
-		print_emv_app(app);
-		print_emv_tlv_list(&app->tlv_list);
+	} while (true);
 
-		// Capture ICC data
-		emv_txn.icc = app->tlv_list;
-		app->tlv_list = EMV_TLV_LIST_INIT;
-		emv_app_free(app);
+	// Application selection has been successful and the application list
+	// is no longer needed.
+	emv_app_list_clear(&app_list);
+
+	// HACK: test GPO and Read Application Data
+	{
+		char str[1024];
 
 		// Process PDOL
 		struct emv_tlv_t* pdol;
@@ -660,6 +720,7 @@ int main(int argc, char** argv)
 		printf("\nGET PROCESSING OPTIONS\n");
 		uint8_t gpo_response[EMV_RAPDU_DATA_MAX];
 		size_t gpo_response_len = sizeof(gpo_response);
+		uint16_t sw1sw2;
 		r = emv_ttl_get_processing_options(&emv_txn.ttl, gpo_data, gpo_data_len, gpo_response, &gpo_response_len, &sw1sw2);
 		if (r) {
 			printf("Failed to get processign options; r=%d\n", r);