From eb75ad4efa36703ed5dc7aaed1779e97497febb1 Mon Sep 17 00:00:00 2001
From: Pol Henarejos <pol.henarejos@cttc.es>
Date: Sun, 25 May 2025 19:07:20 +0200
Subject: [PATCH] Add app_exists() to check if an AID is loaded.

---
 src/apdu.h |  1 +
 src/main.c | 15 +++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/src/apdu.h b/src/apdu.h
index b0d7f70..a486bd3 100644
--- a/src/apdu.h
+++ b/src/apdu.h
@@ -33,6 +33,7 @@ typedef struct app {
     int (*unload)();
 } app_t;
 
+extern bool app_exists(const uint8_t *aid, size_t aid_len);
 extern int register_app(int (*)(app_t *, uint8_t), const uint8_t *);
 extern int select_app(const uint8_t *aid, size_t aid_len);
 
diff --git a/src/main.c b/src/main.c
index 4df4647..1d866ae 100644
--- a/src/main.c
+++ b/src/main.c
@@ -54,7 +54,22 @@ app_t *current_app = NULL;
 
 const uint8_t *ccid_atr = NULL;
 
+bool app_exists(const uint8_t *aid, size_t aid_len) {
+    if (current_app && current_app->aid && (current_app->aid + 1 == aid || !memcmp(current_app->aid + 1, aid, aid_len))) {
+        return true;
+    }
+    for (int a = 0; a < num_apps; a++) {
+        if (!memcmp(apps[a].aid + 1, aid, MIN(aid_len, apps[a].aid[0]))) {
+            return true;
+        }
+    }
+    return false;
+}
+
 int register_app(int (*select_aid)(app_t *, uint8_t), const uint8_t *aid) {
+    if (app_exists(aid + 1, aid[0])) {
+        return 1;
+    }
     if (num_apps < sizeof(apps) / sizeof(app_t)) {
         apps[num_apps].select_aid = select_aid;
         apps[num_apps].aid = aid;