initial commit: WIP debugging PAM module

tests/app/pam_test_app.cpp

@@ -0,0 +1,95 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright 2026 Suyono
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+#include <security/pam_appl.h>
+#include <security/pam_misc.h>
+
+#include <cstdlib>
+#include <cstring>
+#include <iostream>
+#include <string>
+
+namespace {
+
+struct AppData {
+    const char* password;
+};
+
+int conversation(int num_msg, const struct pam_message** msg, struct pam_response** resp, void* appdata_ptr) {
+    if (num_msg <= 0 || msg == nullptr || resp == nullptr) {
+        return PAM_CONV_ERR;
+    }
+
+    auto* app_data = static_cast<AppData*>(appdata_ptr);
+    auto* replies = static_cast<pam_response*>(calloc(static_cast<size_t>(num_msg), sizeof(pam_response)));
+    if (replies == nullptr) {
+        return PAM_BUF_ERR;
+    }
+
+    for (int i = 0; i < num_msg; ++i) {
+        replies[i].resp_retcode = 0;
+        replies[i].resp = nullptr;
+
+        switch (msg[i]->msg_style) {
+            case PAM_PROMPT_ECHO_OFF:
+            case PAM_PROMPT_ECHO_ON:
+                if (app_data != nullptr && app_data->password != nullptr) {
+                    replies[i].resp = strdup(app_data->password);
+                    if (replies[i].resp == nullptr) {
+                        free(replies);
+                        return PAM_BUF_ERR;
+                    }
+                }
+                break;
+            case PAM_ERROR_MSG:
+            case PAM_TEXT_INFO:
+                break;
+            default:
+                free(replies);
+                return PAM_CONV_ERR;
+        }
+    }
+
+    *resp = replies;
+    return PAM_SUCCESS;
+}
+
+}  // namespace
+
+int main(int argc, char** argv) {
+    if (argc < 3) {
+        std::cerr << "Usage: " << argv[0] << " <service> <user> [password]" << std::endl;
+        return 2;
+    }
+
+    const std::string service = argv[1];
+    const std::string user = argv[2];
+    const char* password = (argc >= 4) ? argv[3] : "";
+
+    AppData app_data{password};
+    pam_conv conv{conversation, &app_data};
+    pam_handle_t* pamh = nullptr;
+
+    int rc = pam_start(service.c_str(), user.c_str(), &conv, &pamh);
+    if (rc != PAM_SUCCESS) {
+        std::cerr << "pam_start failed: " << pam_strerror(pamh, rc) << std::endl;
+        return 1;
+    }
+
+    rc = pam_authenticate(pamh, 0);
+    if (rc == PAM_SUCCESS) {
+        std::cout << "Authentication succeeded" << std::endl;
+    } else {
+        std::cout << "Authentication failed: " << pam_strerror(pamh, rc) << std::endl;
+    }
+
+    const int end_rc = pam_end(pamh, rc);
+    if (end_rc != PAM_SUCCESS) {
+        std::cerr << "pam_end failed: " << pam_strerror(pamh, end_rc) << std::endl;
+    }
+
+    return (rc == PAM_SUCCESS) ? 0 : 1;
+}