1 files changed, 130 insertions, 0 deletions
diff --git a/src/auth.c b/src/auth.c
new file mode 100644
index 0000000..97e934f
--- /dev/null
+++ b/src/auth.c
@@ -0,0 +1,130 @@
+/*
+ * auth.c
+ *
+ * Created by buzzert <buzzert@buzzert.net> 2019-01-19
+ */
+
+#include "auth.h"
+
+#include <pthread.h>
+#include <pwd.h>
+#include <security/pam_appl.h>
+#include <semaphore.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+struct auth_handle_t {
+    void             *context;
+    auth_callbacks_t  callbacks;
+
+    sem_t                   prompt_semaphore;
+    auth_prompt_response_t *prompt_response;
+};
+
+int process_message(const struct pam_message *msg, struct pam_response *resp, struct auth_handle_t *handle)
+{
+    switch (msg->msg_style) {
+        case PAM_PROMPT_ECHO_ON:
+        case PAM_PROMPT_ECHO_OFF: {
+            handle->callbacks.prompt_handler(msg->msg, handle->context);
+
+            sem_wait(&handle->prompt_semaphore);
+
+            auth_prompt_response_t *response = handle->prompt_response;
+            resp->resp = response->response_buffer;
+            resp->resp_retcode = response->response_code;
+            break;
+        }
+        case PAM_ERROR_MSG:
+            handle->callbacks.error_handler(msg->msg, handle->context);
+            break;
+        case PAM_TEXT_INFO:
+            handle->callbacks.info_handler(msg->msg, handle->context);
+            break;
+    }
+
+    return PAM_SUCCESS;
+}
+
+int perform_conversation(int num_msg, const struct pam_message **msg, struct pam_response **resp, void *data)
+{
+	*resp = calloc(num_msg, sizeof(struct pam_response));
+
+    struct auth_handle_t *handle = (struct auth_handle_t *)data;
+    for (unsigned i = 0; i < num_msg; ++i) {
+        process_message(msg[i], resp[i], handle);
+    }
+
+    return PAM_SUCCESS;
+}
+
+static void* auth_thread_main(void *arg)
+{
+    struct pam_conv conv;
+    conv.conv = perform_conversation;
+    conv.appdata_ptr = arg;
+
+    // Get current username
+    struct passwd *pwd = getpwuid(getuid());
+    const char *username = pwd->pw_name;
+    if (username == NULL || strlen(username) == 0) {
+        fprintf(stderr, "Couldn't get name for the current user\n");
+        // todo: report to callback
+    }
+
+    // Start PAM authentication
+    pam_handle_t *pam = NULL;
+    pam_start(
+        "login",
+        username,
+        &conv,
+        &pam
+    );
+
+    bool authenticating = true;
+    struct auth_handle_t *handle = (struct auth_handle_t *)arg;
+    while (authenticating) {
+        int status = pam_authenticate(pam, 0);
+        handle->callbacks.result_handler(status, handle->context);
+
+        if (status == PAM_SUCCESS) {
+            authenticating = false;
+        }
+    }
+
+    pam_end(pam, 0);
+
+    return NULL;
+}
+
+struct auth_handle_t* auth_begin_authentication(auth_callbacks_t callbacks, void *context)
+{
+    struct auth_handle_t *handle = malloc(sizeof(struct auth_handle_t));
+    handle->callbacks = callbacks;
+    handle->context = context;
+    handle->prompt_response = NULL;
+    sem_init(&handle->prompt_semaphore, 0, 0);
+
+    pthread_t auth_thread;
+    if (pthread_create(&auth_thread, NULL, auth_thread_main, handle)) {
+        fprintf(stderr, "Error creating auth thread\n");
+    }
+
+    return handle;
+}
+
+
+void auth_attempt_authentication(struct auth_handle_t *handle, auth_prompt_response_t response)
+{
+    if (handle->prompt_response == NULL) {
+        handle->prompt_response = malloc(sizeof(auth_prompt_response_t));
+    }
+    handle->prompt_response = memcpy(handle->prompt_response, &response, sizeof(auth_prompt_response_t));
+
+    sem_post(&handle->prompt_semaphore);
+}
+
+