From 709db95bff5d88ed2d9d5911e8050cacb4f46921 Mon Sep 17 00:00:00 2001
From: panchenbo <panchenbo@uniontech.com>
Date: Sun, 25 Apr 2021 18:28:22 +0800
Subject: [PATCH] multi-pipe mode

---
 liblightdm-gobject/greeter.c |   5 +-
 src/greeter.c                |   9 ++--
 src/session-child.c          | 100 ++++++++++++++++++++++++++++++-----
 src/session.c                | 100 +++++++++++++++++++++++++++++++++--
 src/session.h                |   7 +++
 5 files changed, 200 insertions(+), 21 deletions(-)

diff --git a/liblightdm-gobject/greeter.c b/liblightdm-gobject/greeter.c
index fd1763c..78c3981 100644
--- a/liblightdm-gobject/greeter.c
+++ b/liblightdm-gobject/greeter.c
@@ -652,7 +652,6 @@ handle_prompt_authentication (LightDMGreeter *greeter, guint8 *message, gsize me
 
     g_list_free_full (priv->responses_received, g_free);
     priv->responses_received = NULL;
-    priv->n_responses_waiting = 0;
 
     guint32 n_messages = read_int (message, message_length, offset);
     g_debug ("Prompt user with %d message(s)", n_messages);
@@ -713,6 +712,8 @@ handle_end_authentication (LightDMGreeter *greeter, guint8 *message, gsize messa
     priv->is_authenticated = (return_code == 0);
 
     priv->in_authentication = FALSE;
+    // reset
+    priv->n_responses_waiting = 0;
     g_signal_emit (G_OBJECT (greeter), signals[AUTHENTICATION_COMPLETE], 0);
 }
 
@@ -1330,6 +1331,8 @@ lightdm_greeter_authenticate (LightDMGreeter *greeter, const gchar *username, GE
     priv->cancelling_authentication = FALSE;
     priv->authenticate_sequence_number++;
     priv->in_authentication = TRUE;
+    // reset
+    priv->n_responses_waiting = 0;
     priv->is_authenticated = FALSE;
     if (username != priv->authentication_user)
     {
diff --git a/src/greeter.c b/src/greeter.c
index 383e1f8..fc4850d 100644
--- a/src/greeter.c
+++ b/src/greeter.c
@@ -394,6 +394,7 @@ pam_messages_cb (Session *session, Greeter *greeter)
     }
     write_message (greeter, message, offset);
 
+    g_debug ("Prompt greeter with %d n_prompts", n_prompts);
     /* Continue immediately if nothing to respond with */
     // FIXME: Should probably give the greeter a chance to ack the message
     if (n_prompts == 0)
@@ -645,8 +646,8 @@ handle_continue_authentication (Greeter *greeter, gchar **secrets)
     if (priv->authentication_session == NULL)
         return;
 
-    int messages_length = session_get_messages_length (priv->authentication_session);
-    const struct pam_message *messages = session_get_messages (priv->authentication_session);
+    int messages_length = session_get_prompt_messages_length (priv->authentication_session);
+    const struct pam_message *messages = session_get_prompt_messages (priv->authentication_session);
 
     /* Check correct number of responses */
     int n_prompts = 0;
@@ -658,7 +659,7 @@ handle_continue_authentication (Greeter *greeter, gchar **secrets)
     }
     if (g_strv_length (secrets) != n_prompts)
     {
-        session_respond_error (priv->authentication_session, PAM_CONV_ERR);
+        session_prompt_respond_error (priv->authentication_session, PAM_CONV_ERR);
         return;
     }
 
@@ -678,7 +679,7 @@ handle_continue_authentication (Greeter *greeter, gchar **secrets)
         }
     }
 
-    session_respond (priv->authentication_session, response);
+    session_prompt_respond (priv->authentication_session, response);
 
     for (int i = 0; i < messages_length; i++)
         secure_free (greeter, response[i].resp);
diff --git a/src/session-child.c b/src/session-child.c
index eef51e4..64716b2 100644
--- a/src/session-child.c
+++ b/src/session-child.c
@@ -16,6 +16,7 @@
 #include <utmp.h>
 #include <utmpx.h>
 #include <sys/mman.h>
+#include <pthread.h>
 
 #if HAVE_LIBAUDIT
 #include <libaudit.h>
@@ -37,6 +38,8 @@ static GPid child_pid = 0;
 /* Pipe to communicate with daemon */
 static int from_daemon_output = 0;
 static int to_daemon_input = 0;
+/* Pipe to prompt with daemon */
+static int from_daemon_output_prompt = 0;
 
 static gboolean is_interactive;
 static gboolean do_authenticate;
@@ -72,6 +75,16 @@ read_data (void *buf, size_t count)
     return n_read;
 }
 
+static ssize_t
+read_prompt_data (void *buf, size_t count)
+{
+    ssize_t n_read = read (from_daemon_output_prompt, buf, count);
+    if (n_read < 0)
+        g_printerr ("Error reading prompt from daemon: %s\n", strerror (errno));
+
+    return n_read;
+}
+
 static gchar *
 read_string_full (void* (*alloc_fn)(size_t n))
 {
@@ -93,12 +106,34 @@ read_string_full (void* (*alloc_fn)(size_t n))
     return value;
 }
 
+static gchar *
+read_prompt_string_full (void* (*alloc_fn)(size_t n))
+{
+    int length;
+    if (read_prompt_data (&length, sizeof (length)) <= 0)
+        return NULL;
+    if (length < 0)
+        return NULL;
+    if (length > MAX_STRING_LENGTH)
+    {
+        g_printerr ("Invalid string length %d from daemon\n", length);
+        return NULL;
+    }
+
+    gchar *value = (*alloc_fn) (sizeof (gchar) * (length + 1));
+    read_prompt_data (value, length);
+    value[length] = '\0';
+
+    return value;
+}
+
 static gchar *
 read_string (void)
 {
     return read_string_full (g_malloc);
 }
 
+pthread_mutex_t mutex_msg;
 static int
 pam_conv_cb (int msg_length, const struct pam_message **msg, struct pam_response **resp, void *app_data)
 {
@@ -106,18 +141,26 @@ pam_conv_cb (int msg_length, const struct pam_message **msg, struct pam_response
     if (authentication_complete)
         return PAM_SUCCESS;
 
-    /* Cancel authentication if requiring input */
-    if (!is_interactive)
+    // 将普通消息和PAM_PROMPT_ECHO_X的消息分开，从lightdm中读取回复内容时使用不同的管道
+    // 因为在lightdm的实现中处理PAM_PROMPT_ECHO_X时会一直等待greeter的消息，而其他消息则会立即给出响应结果
+    int n_prompts = 0;
+
+    for (int i = 0; i < msg_length; i++)
     {
-        for (int i = 0; i < msg_length; i++)
+        if (msg[i]->msg_style == PAM_PROMPT_ECHO_ON || msg[i]->msg_style == PAM_PROMPT_ECHO_OFF)   
         {
-            if (msg[i]->msg_style == PAM_PROMPT_ECHO_ON || msg[i]->msg_style == PAM_PROMPT_ECHO_OFF)
+            /* Cancel authentication if requiring input */
+            if (!is_interactive)
             {
                 g_printerr ("Stopping PAM conversation, interaction requested but not supported\n");
                 return PAM_CONV_ERR;
             }
-        }
 
+            ++n_prompts;
+        }
+    }
+    if (!is_interactive)
+    {
         /* Ignore informational messages */
         return PAM_SUCCESS;
     }
@@ -125,6 +168,10 @@ pam_conv_cb (int msg_length, const struct pam_message **msg, struct pam_response
     /* Check if we changed user */
     gchar *username = NULL;
     pam_get_item (pam_handle, PAM_USER, (const void **) &username);
+    
+    // lock for pam
+    // 在pam模块中可能使用多线程调用此函数，加锁是为了保证消息在管道中的相对顺序
+    pthread_mutex_lock(&mutex_msg);
 
     /* Notify the daemon */
     write_string (username);
@@ -140,17 +187,39 @@ pam_conv_cb (int msg_length, const struct pam_message **msg, struct pam_response
 
     /* Get response */
     int error;
-    read_data (&error, sizeof (error));
-    if (error != PAM_SUCCESS)
+    if (n_prompts) {
+        // 只为普通消息加锁，如果 PAM_PROMPT_ECHO_X 类型的消息也从多个线程发送则可能存在风险
+        // unlock for read message
+        pthread_mutex_unlock(&mutex_msg);
+        read_prompt_data (&error, sizeof (error));
+    } else {
+        read_data (&error, sizeof (error));
+    }
+    if (error != PAM_SUCCESS) {
+        if (!n_prompts) {
+            // unlock for read message
+            pthread_mutex_unlock(&mutex_msg);
+        }
         return error;
+    }
     struct pam_response *response = calloc (msg_length, sizeof (struct pam_response));
     for (int i = 0; i < msg_length; i++)
     {
         struct pam_response *r = &response[i];
         // callers of this function inside pam will expect to be able to call
         // free() on the strings we give back.  So alloc with malloc.
-        r->resp = read_string_full (malloc);
-        read_data (&r->resp_retcode, sizeof (r->resp_retcode));
+    if (n_prompts) {
+            r->resp = read_prompt_string_full (malloc);
+            read_prompt_data (&r->resp_retcode, sizeof (r->resp_retcode));
+	} else {
+            r->resp = read_string_full (malloc);
+            read_data (&r->resp_retcode, sizeof (r->resp_retcode));
+	}
+    }
+
+    if (!n_prompts) {
+        // unlock for read message
+        pthread_mutex_unlock(&mutex_msg);
     }
 
     *resp = response;
@@ -262,22 +331,24 @@ session_child_run (int argc, char **argv)
     close (fd);
 
     /* Get the pipe from the daemon */
-    if (argc != 4)
+    if (argc != 5)
     {
-        g_printerr ("Usage: lightdm --session-child INPUTFD OUTPUTFD\n");
+        g_printerr ("Usage: lightdm --session-child INPUTFD OUTPUTFD INPUTFD_PROMPT\n");
         return EXIT_FAILURE;
     }
     from_daemon_output = atoi (argv[2]);
     to_daemon_input = atoi (argv[3]);
-    if (from_daemon_output == 0 || to_daemon_input == 0)
+    from_daemon_output_prompt = atoi (argv[4]);
+    if (from_daemon_output == 0 || to_daemon_input == 0 || from_daemon_output_prompt == 0)
     {
-        g_printerr ("Invalid file descriptors %s %s\n", argv[2], argv[3]);
+        g_printerr ("Invalid file descriptors %s %s %s\n", argv[2], argv[3], argv[4]);
         return EXIT_FAILURE;
     }
 
     /* Don't let these pipes leak to the command we will run */
     fcntl (from_daemon_output, F_SETFD, FD_CLOEXEC);
     fcntl (to_daemon_input, F_SETFD, FD_CLOEXEC);
+    fcntl (from_daemon_output_prompt, F_SETFD, FD_CLOEXEC);
 
     /* Read a version number so we can handle upgrades (i.e. a newer version of session child is run for an old daemon */
     int version;
@@ -330,7 +401,10 @@ session_child_run (int argc, char **argv)
     {
         const gchar *new_username;
 
+	// init mutex for pam_conv_cb
+        pthread_mutex_init(&mutex_msg, 0);
         authentication_result = pam_authenticate (pam_handle, 0);
+        pthread_mutex_destroy(&mutex_msg);
 
         /* See what user we ended up as */
         if (pam_get_item (pam_handle, PAM_USER, (const void **) &new_username) != PAM_SUCCESS)
diff --git a/src/session.c b/src/session.c
index 2ea9352..12ae60a 100644
--- a/src/session.c
+++ b/src/session.c
@@ -52,6 +52,7 @@ typedef struct
     /* Pipes to talk to child */
     int to_child_input;
     int from_child_output;
+    int to_child_prompt_input;
     GIOChannel *from_child_channel;
     guint from_child_watch;
     guint child_watch;
@@ -77,6 +78,9 @@ typedef struct
     /* Messages being requested by PAM */
     int messages_length;
     struct pam_message *messages;
+    /* Prompt Messages being requested by PAM */
+    int prompt_messages_length;
+    struct pam_message *prompt_messages;
 
     /* Authentication result from PAM */
     gboolean authentication_started;
@@ -382,6 +386,14 @@ write_data (Session *session, const void *buf, size_t count)
         l_warning (session, "Error writing to session: %s", strerror (errno));
 }
 
+static void
+write_prompt_data (Session *session, const void *buf, size_t count)
+{
+    SessionPrivate *priv = session_get_instance_private (session);
+    if (write (priv->to_child_prompt_input, buf, count) != count)
+        l_warning (session, "Error writing prompt to session: %s", strerror (errno));
+}
+
 static void
 write_string (Session *session, const char *value)
 {
@@ -391,6 +403,15 @@ write_string (Session *session, const char *value)
         write_data (session, value, sizeof (char) * length);
 }
 
+static void
+write_prompt_string (Session *session, const char *value)
+{
+    int length = value ? strlen (value) : -1;
+    write_prompt_data (session, &length, sizeof (length));
+    if (value)
+        write_prompt_data (session, value, sizeof (char) * length);
+}
+
 static void
 write_xauth (Session *session, XAuthority *x_authority)
 {
@@ -534,6 +555,8 @@ from_child_cb (GIOChannel *source, GIOCondition condition, gpointer data)
     }
     else
     {
+        gboolean n_prompts = 0;
+
         priv->messages_length = 0;
         read_from_child (session, &priv->messages_length, sizeof (priv->messages_length));
         priv->messages = calloc (priv->messages_length, sizeof (struct pam_message));
@@ -542,6 +565,13 @@ from_child_cb (GIOChannel *source, GIOCondition condition, gpointer data)
             struct pam_message *m = &priv->messages[i];
             read_from_child (session, &m->msg_style, sizeof (m->msg_style));
             m->msg = read_string_from_child (session);
+	    if (m->msg_style == PAM_PROMPT_ECHO_OFF || m->msg_style == PAM_PROMPT_ECHO_ON)
+                ++n_prompts;
+        }
+        // for prompt message
+        if (n_prompts) {
+            priv->prompt_messages_length = priv->messages_length;
+            priv->prompt_messages = priv->messages;
         }
 
         l_debug (session, "Got %d message(s) from PAM", priv->messages_length);
@@ -585,15 +615,17 @@ session_real_start (Session *session)
         display_server_connect_session (priv->display_server, session);
 
     /* Create pipes to talk to the child */
-    int to_child_pipe[2], from_child_pipe[2];
-    if (pipe (to_child_pipe) < 0 || pipe (from_child_pipe) < 0)
+    int to_child_pipe[2], from_child_pipe[2], to_child_prompt_pipe[2];
+    if (pipe (to_child_pipe) < 0 || pipe (from_child_pipe) < 0 || pipe (to_child_prompt_pipe) < 0)
     {
         g_warning ("Failed to create pipe to communicate with session process: %s", strerror (errno));
         return FALSE;
     }
     int to_child_output = to_child_pipe[0];
+    int to_child_prompt_output = to_child_prompt_pipe[0];
     priv->to_child_input = to_child_pipe[1];
     priv->from_child_output = from_child_pipe[0];
+    priv->to_child_prompt_input = to_child_prompt_pipe[1];
     int from_child_input = from_child_pipe[1];
     priv->from_child_channel = g_io_channel_unix_new (priv->from_child_output);
     priv->from_child_watch = g_io_add_watch (priv->from_child_channel, G_IO_IN | G_IO_HUP, from_child_cb, session);
@@ -601,6 +633,7 @@ session_real_start (Session *session)
     /* Don't allow the daemon end of the pipes to be accessed in child processes */
     fcntl (priv->to_child_input, F_SETFD, FD_CLOEXEC);
     fcntl (priv->from_child_output, F_SETFD, FD_CLOEXEC);
+    fcntl (priv->to_child_prompt_input, F_SETFD, FD_CLOEXEC);
 
     /* Create the guest account if it is one */
     if (priv->is_guest && priv->username == NULL)
@@ -613,6 +646,7 @@ session_real_start (Session *session)
     /* Run the child */
     g_autofree gchar *arg0 = g_strdup_printf ("%d", to_child_output);
     g_autofree gchar *arg1 = g_strdup_printf ("%d", from_child_input);
+    g_autofree gchar *arg2 = g_strdup_printf ("%d", to_child_prompt_output);
     priv->pid = fork ();
     if (priv->pid == 0)
     {
@@ -620,7 +654,7 @@ session_real_start (Session *session)
         execlp ("lightdm",
                 "lightdm",
                 "--session-child",
-                arg0, arg1, NULL);
+                arg0, arg1, arg2, NULL);
         _exit (EXIT_FAILURE);
     }
 
@@ -642,6 +676,7 @@ session_real_start (Session *session)
     /* Close the ends of the pipes we don't need */
     close (to_child_output);
     close (from_child_input);
+    close (to_child_prompt_output);
 
     /* Indicate what version of the protocol we are using */
     int version = 3;
@@ -702,6 +737,11 @@ session_respond (Session *session, struct pam_response *response)
         write_data (session, &response[i].resp_retcode, sizeof (response[i].resp_retcode));
     }
 
+    if (priv->messages == priv->prompt_messages) {
+        l_warning (session, "%s", "Current message is prompt message");
+        return;
+    }
+
     /* Delete the old messages */
     for (int i = 0; i < priv->messages_length; i++)
         g_free ((char *) priv->messages[i].msg);
@@ -710,6 +750,35 @@ session_respond (Session *session, struct pam_response *response)
     priv->messages_length = 0;
 }
 
+void
+session_prompt_respond (Session *session, struct pam_response *response)
+{
+    SessionPrivate *priv = session_get_instance_private (session);
+
+    g_return_if_fail (session != NULL);
+
+    int error = PAM_SUCCESS;
+    write_prompt_data (session, &error, sizeof (error));
+    for (int i = 0; i < priv->prompt_messages_length; i++)
+    {
+        write_prompt_string (session, response[i].resp);
+        write_prompt_data (session, &response[i].resp_retcode, sizeof (response[i].resp_retcode));
+    }
+
+    // clear
+    if (priv->messages == priv->prompt_messages) {
+        priv->messages = NULL;
+        priv->messages_length = 0;
+    }
+
+    /* Delete the old messages */
+    for (int i = 0; i < priv->prompt_messages_length; i++)
+        g_free ((char *) priv->prompt_messages[i].msg);
+    g_free (priv->prompt_messages);
+    priv->prompt_messages = NULL;
+    priv->prompt_messages_length = 0;
+}
+
 void
 session_respond_error (Session *session, int error)
 {
@@ -719,6 +788,15 @@ session_respond_error (Session *session, int error)
     write_data (session, &error, sizeof (error));
 }
 
+void
+session_prompt_respond_error (Session *session, int error)
+{
+    g_return_if_fail (session != NULL);
+    g_return_if_fail (error != PAM_SUCCESS);
+
+    write_prompt_data (session, &error, sizeof (error));
+}
+
 int
 session_get_messages_length (Session *session)
 {
@@ -727,6 +805,22 @@ session_get_messages_length (Session *session)
     return priv->messages_length;
 }
 
+int
+session_get_prompt_messages_length(Session *session)
+{
+    SessionPrivate *priv = session_get_instance_private (session);
+    g_return_val_if_fail (session != NULL, 0);
+    return priv->prompt_messages_length;
+}
+
+const struct pam_message *
+session_get_prompt_messages(Session *session)
+{
+    SessionPrivate *priv = session_get_instance_private (session);
+    g_return_val_if_fail (session != NULL, NULL);
+    return priv->prompt_messages;
+}
+
 const struct pam_message *
 session_get_messages (Session *session)
 {
diff --git a/src/session.h b/src/session.h
index 350cf3b..de15ae4 100644
--- a/src/session.h
+++ b/src/session.h
@@ -124,12 +124,19 @@ const gchar *session_get_console_kit_cookie (Session *session);
 
 void session_respond (Session *session, struct pam_response *response);
 
+void session_prompt_respond (Session *session, struct pam_response *response);
+
 void session_respond_error (Session *session, int error);
 
+void session_prompt_respond_error (Session *session, int error);
+
 int session_get_messages_length (Session *session);
 
 const struct pam_message *session_get_messages (Session *session);
 
+int session_get_prompt_messages_length (Session *session);
+const struct pam_message *session_get_prompt_messages (Session *session);
+
 gboolean session_get_is_authenticated (Session *session);
 
 int session_get_authentication_result (Session *session);
-- 
2.20.1