From 01629ac7358ef026127ebe707c4d13e143aa6e31 Mon Sep 17 00:00:00 2001
From: Johannes Findeisen <you@hanez.org>
Date: Sat, 10 Aug 2024 06:11:11 +0200
Subject: [PATCH] Added an interactive program too. Wann make this a feature
 using -i in the main program.

---
 checkpw_interactive.c | 86 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)
 create mode 100644 checkpw_interactive.c

diff --git a/checkpw_interactive.c b/checkpw_interactive.c
new file mode 100644
index 0000000..ea5eee1
--- /dev/null
+++ b/checkpw_interactive.c
@@ -0,0 +1,86 @@
+#include <security/pam_appl.h>
+#include <security/pam_misc.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+// Custom data structure to hold user-entered password
+struct pam_credentials {
+    const char *password;
+};
+
+// PAM conversation function to supply the password
+int pam_conversation(int num_msg, const struct pam_message **msg,
+                     struct pam_response **resp, void *appdata_ptr) {
+    struct pam_response *response = NULL;
+    struct pam_credentials *credentials = (struct pam_credentials *)appdata_ptr;
+    int i;
+
+    response = (struct pam_response *)malloc(sizeof(struct pam_response) * num_msg);
+    if (response == NULL) {
+        return PAM_CONV_ERR;
+    }
+
+    for (i = 0; i < num_msg; i++) {
+        if (msg[i]->msg_style == PAM_PROMPT_ECHO_OFF || msg[i]->msg_style == PAM_PROMPT_ECHO_ON) {
+            response[i].resp = strdup(credentials->password);
+            response[i].resp_retcode = 0;
+        }
+    }
+
+    *resp = response;
+    return PAM_SUCCESS;
+}
+
+int authenticate(const char *username, const char *password) {
+    pam_handle_t *pamh = NULL;
+    int retval;
+    struct pam_credentials credentials = { password };
+    struct pam_conv conv = { pam_conversation, &credentials };
+
+    retval = pam_start("login", username, &conv, &pamh);
+
+    if (retval == PAM_SUCCESS) {
+        retval = pam_authenticate(pamh, 0); // Attempt to authenticate
+    }
+
+    if (retval == PAM_SUCCESS) {
+        retval = pam_acct_mgmt(pamh, 0); // Check account validity
+    }
+
+    if (pam_end(pamh, retval) != PAM_SUCCESS) {
+        pamh = NULL;
+        fprintf(stderr, "Failed to release PAM authenticator\n");
+        exit(1);
+    }
+
+    return (retval == PAM_SUCCESS ? 0 : 1); // 0 for success, 1 for failure
+}
+
+int main() {
+    char username[256];
+    char *password;
+
+    // Prompt user for a username
+    printf("Username: ");
+    if (fgets(username, sizeof(username), stdin) == NULL) {
+        fprintf(stderr, "Failed to read username\n");
+        exit(1);
+    }
+
+    // Remove the trailing newline character if it exists
+    username[strcspn(username, "\n")] = '\0';
+
+    // Prompt user for a password
+    password = getpass("Password: ");
+
+    // Authenticate the user
+    if (authenticate(username, password) == 0) {
+        printf("Authenticated successfully.\n");
+        return 0;
+    } else {
+        printf("Authentication failed.\n");
+        return 1;
+    }
+}
+