CVE-2017-14604 (published 2017-09-20T08:29Z)

GNOME Nautilus before 3.23.90 allows attackers to spoof a file type by using the .desktop file extension, as demonstrated by an attack in which a .desktop file\'s Name field ends in .pdf but this file\'s Exec field launches a malicious "sh -c" command. In other words, Nautilus provides no UI indication that a file actually has the potentially unsafe .desktop extension; instead, the UI only shows the .pdf extension. One (slightly) mitigating factor is that an attack requires the .desktop file to have execute permission. The solution is to ask the user to confirm that the file is supposed to be treated as a .desktop file, and then remember the user\'s answer in the metadata::trusted field.

Severity: MEDIUM
CVSS v2 base score: 4.0 (AV:N/AC:L/Au:S/C:N/I:P/A:N)
CVSS v3 base score: 6.5, MEDIUM (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N)

Weakness information:
cwe_id: CWE-20
cwe_name: Improper Input Validation
description: The product receives input or data, but it does
        not validate or incorrectly validates that the input has the
        properties that are required to process the data safely and
        correctly.
extended_description: 
	   Input validation is a frequently-used technique
	   for checking potentially dangerous inputs in order to
	   ensure that the inputs are safe for processing within the
	   code, or when communicating with other components.  When
	   software does not validate input properly, an attacker is
	   able to craft the input in a form that is not expected by
	   the rest of the application. This will lead to parts of the
	   system receiving unintended input, which may result in
	   altered control flow, arbitrary control of a resource, or
	   arbitrary code execution.
	   Input validation is not the only technique for
	   processing input, however.  Other techniques attempt to
	   transform potentially-dangerous input into something safe, such
	   as filtering (CWE-790) - which attempts to remove dangerous
	   inputs - or encoding/escaping (CWE-116), which attempts to
	   ensure that the input is not misinterpreted when it is included
	   in output to another component. Other techniques exist as well
	   (see CWE-138 for more examples.)
	   Input validation can be applied to:
	   
	     raw data - strings, numbers, parameters, file contents, etc.
	     metadata - information about the raw data, such as headers or size
	   
	   Data can be simple or structured.  Structured data
	   can be composed of many nested layers, composed of
	   combinations of metadata and raw data, with other simple or
	   structured data.
	   Many properties of raw data or metadata may need
	   to be validated upon entry into the code, such
	   as:
	   
	     specified quantities such as size, length, frequency, price, rate, number of operations, time, etc.
	     implied or derived quantities, such as the actual size of a file instead of a specified size
	     indexes, offsets, or positions into more complex data structures
	     symbolic keys or other elements into hash tables, associative arrays, etc.
	     well-formedness, i.e. syntactic correctness - compliance with expected syntax 
	     lexical token correctness - compliance with rules for what is treated as a token
	     specified or derived type - the actual type of the input (or what the input appears to be)
	     consistency - between individual data elements, between raw data and metadata, between references, etc.
	     conformance to domain-specific rules, e.g. business logic 
	     equivalence - ensuring that equivalent inputs are treated the same
	     authenticity, ownership, or other attestations about the input, e.g. a cryptographic signature to prove the source of the data
	   
	   Implied or derived properties of data must often
	   be calculated or inferred by the code itself.  Errors in
	   deriving properties may be considered a contributing factor
	   to improper input validation.
	   
	   Note that "input validation" has very different
	   meanings to different people, or within different
	   classification schemes.  Caution must be used when
	   referencing this CWE entry or mapping to it.  For example,
	   some weaknesses might involve inadvertently giving control
	   to an attacker over an input when they should not be able
	   to provide an input at all, but sometimes this is referred
	   to as input validation.
	   Finally, it is important to emphasize that the
	   distinctions between input validation and output escaping
	   are often blurred, and developers must be careful to
	   understand the difference, including how input validation
	   is not always sufficient to prevent vulnerabilities,
	   especially when less stringent data types must be
	   supported, such as free-form text. Consider a SQL injection
	   scenario in which a person's last name is inserted into a
	   query. The name "O'Reilly" would likely pass the validation
	   step since it is a common last name in the English
	   language. However, this valid name cannot be directly
	   inserted into the database because it contains the "'"
	   apostrophe character, which would need to be escaped or
	   otherwise transformed. In this case, removing the
	   apostrophe might reduce the risk of SQL injection, but it
	   would produce incorrect behavior because the wrong name
	   would be recorded.
       
         

Fix information:
repo_url: https://github.com/GNOME/nautilus
commit_details: repo_url: https://github.com/GNOME/nautilus
author: Carlos Soriano
author_date: 2017-02-06 18:47:54+01:00
msg: mime-actions: use file metadata for trusting desktop files

Currently we only trust desktop files that have the executable bit
set, and don't replace the displayed icon or the displayed name until
it's trusted, which prevents for running random programs by a malicious
desktop file.

However, the executable permission is preserved if the desktop file
comes from a compressed file.

To prevent this, add a metadata::trusted metadata to the file once the
user acknowledges the file as trusted. This adds metadata to the file,
which cannot be added unless it has access to the computer.

Also remove the SHEBANG "trusted" content we were putting inside the
desktop file, since that doesn't add more security since it can come
with the file itself.

https://bugzilla.gnome.org/show_bug.cgi?id=777991
repository: repo_url: https://github.com/GNOME/nautilus
repo_name: GNOME/nautilus
description: Read-only mirror of https://gitlab.gnome.org/GNOME/nautilus
repo_language: C
owner: GNOME
file_changes: filename: nautilus-directory-async.c
change_type: ModificationType.MODIFY
diff: @@ -30,6 +30,7 @@
 #include "nautilus-global-preferences.h"
 #include "nautilus-link.h"
 #include "nautilus-profile.h"
+#include "nautilus-metadata.h"
 #include <eel/eel-glib-extensions.h>
 #include <gtk/gtk.h>
 #include <libxml/parser.h>
@@ -3580,13 +3581,17 @@ is_link_trusted (NautilusFile *file,
 {
     GFile *location;
     gboolean res;
+    g_autofree gchar* trusted = NULL;
 
     if (!is_launcher)
     {
         return TRUE;
     }
 
-    if (nautilus_file_can_execute (file))
+    trusted = nautilus_file_get_metadata (file,
+                                          NAUTILUS_METADATA_KEY_DESKTOP_FILE_TRUSTED,
+                                          NULL);
+    if (nautilus_file_can_execute (file) && trusted != NULL)
     {
         return TRUE;
     }

programming_language: C
filename: nautilus-file-operations.c
change_type: ModificationType.MODIFY
diff: @@ -235,10 +235,10 @@ typedef struct
 #define COPY_FORCE _("Copy _Anyway")
 
 static void
-mark_desktop_file_trusted (CommonJob    *common,
-                           GCancellable *cancellable,
-                           GFile        *file,
-                           gboolean      interactive);
+mark_desktop_file_executable (CommonJob    *common,
+                              GCancellable *cancellable,
+                              GFile        *file,
+                              gboolean      interactive);
 
 static gboolean
 is_all_button_text (const char *button_text)
@@ -5290,10 +5290,10 @@ retry:
             g_file_equal (copy_job->desktop_location, dest_dir) &&
             is_trusted_desktop_file (src, job->cancellable))
         {
-            mark_desktop_file_trusted (job,
-                                       job->cancellable,
-                                       dest,
-                                       FALSE);
+            mark_desktop_file_executable (job,
+                                          job->cancellable,
+                                          dest,
+                                          FALSE);
         }
 
         if (job->undo_info != NULL)
@@ -7887,9 +7887,9 @@ nautilus_file_operations_empty_trash (GtkWidget *parent_view)
 }
 
 static void
-mark_trusted_task_done (GObject      *source_object,
-                        GAsyncResult *res,
-                        gpointer      user_data)
+mark_desktop_file_executable_task_done (GObject      *source_object,
+                                        GAsyncResult *res,
+                                        gpointer      user_data)
 {
     MarkTrustedJob *job = user_data;
 
@@ -7907,110 +7907,19 @@ mark_trusted_task_done (GObject      *source_object,
 #define TRUSTED_SHEBANG "#!/usr/bin/env xdg-open\n"
 
 static void
-mark_desktop_file_trusted (CommonJob    *common,
-                           GCancellable *cancellable,
-                           GFile        *file,
-                           gboolean      interactive)
+mark_desktop_file_executable (CommonJob    *common,
+                              GCancellable *cancellable,
+                              GFile        *file,
+                              gboolean      interactive)
 {
-    char *contents, *new_contents;
-    gsize length, new_length;
     GError *error;
     guint32 current_perms, new_perms;
     int response;
     GFileInfo *info;
 
 retry:
-    error = NULL;
-    if (!g_file_load_contents (file,
-                               cancellable,
-                               &contents, &length,
-                               NULL, &error))
-    {
-        if (interactive)
-        {
-            response = run_error (common,
-                                  g_strdup (_("Unable to mark launcher trusted (executable)")),
-                                  error->message,
-                                  NULL,
-                                  FALSE,
-                                  CANCEL, RETRY,
-                                  NULL);
-        }
-        else
-        {
-            response = 0;
-        }
-
-
-        if (response == 0 || response == GTK_RESPONSE_DELETE_EVENT)
-        {
-            abort_job (common);
-        }
-        else if (response == 1)
-        {
-            goto retry;
-        }
-        else
-        {
-            g_assert_not_reached ();
-        }
-
-        goto out;
-    }
-
-    if (!g_str_has_prefix (contents, "#!"))
-    {
-        new_length = length + strlen (TRUSTED_SHEBANG);
-        new_contents = g_malloc (new_length);
-
-        strcpy (new_contents, TRUSTED_SHEBANG);
-        memcpy (new_contents + strlen (TRUSTED_SHEBANG),
-                contents, length);
-
-        if (!g_file_replace_contents (file,
-                                      new_contents,
-                                      new_length,
-                                      NULL,
-                                      FALSE, 0,
-                                      NULL, cancellable, &error))
-        {
-            g_free (contents);
-            g_free (new_contents);
-
-            if (interactive)
-            {
-                response = run_error (common,
-                                      g_strdup (_("Unable to mark launcher trusted (executable)")),
-                                      error->message,
-                                      NULL,
-                                      FALSE,
-                                      CANCEL, RETRY,
-                                      NULL);
-            }
-            else
-            {
-                response = 0;
-            }
-
-            if (response == 0 || response == GTK_RESPONSE_DELETE_EVENT)
-            {
-                abort_job (common);
-            }
-            else if (response == 1)
-            {
-                goto retry;
-            }
-            else
-            {
-                g_assert_not_reached ();
-            }
-
-            goto out;
-        }
-        g_free (new_contents);
-    }
-    g_free (contents);
 
+    error = NULL;
     info = g_file_query_info (file,
                               G_FILE_ATTRIBUTE_STANDARD_TYPE ","
                               G_FILE_ATTRIBUTE_UNIX_MODE,
@@ -8101,10 +8010,10 @@ out:
 }
 
 static void
-mark_trusted_task_thread_func (GTask        *task,
-                               gpointer      source_object,
-                               gpointer      task_data,
-                               GCancellable *cancellable)
+mark_desktop_file_executable_task_thread_func (GTask        *task,
+                                               gpointer      source_object,
+                                               gpointer      task_data,
+                                               GCancellable *cancellable)
 {
     MarkTrustedJob *job = task_data;
     CommonJob *common;
@@ -8113,18 +8022,18 @@ mark_trusted_task_thread_func (GTask        *task,
 
     nautilus_progress_info_start (job->common.progress);
 
-    mark_desktop_file_trusted (common,
-                               cancellable,
-                               job->file,
-                               job->interactive);
+    mark_desktop_file_executable (common,
+                                  cancellable,
+                                  job->file,
+                                  job->interactive);
 }
 
 void
-nautilus_file_mark_desktop_file_trusted (GFile              *file,
-                                         GtkWindow          *parent_window,
-                                         gboolean            interactive,
-                                         NautilusOpCallback  done_callback,
-                                         gpointer            done_callback_data)
+nautilus_file_mark_desktop_file_executable (GFile              *file,
+                                            GtkWindow          *parent_window,
+                                            gboolean            interactive,
+                                            NautilusOpCallback  done_callback,
+                                            gpointer            done_callback_data)
 {
     GTask *task;
     MarkTrustedJob *job;
@@ -8135,9 +8044,9 @@ nautilus_file_mark_desktop_file_trusted (GFile              *file,
     job->done_callback = done_callback;
     job->done_callback_data = done_callback_data;
 
-    task = g_task_new (NULL, NULL, mark_trusted_task_done, job);
+    task = g_task_new (NULL, NULL, mark_desktop_file_executable_task_done, job);
     g_task_set_task_data (task, job, NULL);
-    g_task_run_in_thread (task, mark_trusted_task_thread_func);
+    g_task_run_in_thread (task, mark_desktop_file_executable_task_thread_func);
     g_object_unref (task);
 }
 

programming_language: C
filename: nautilus-file-operations.h
change_type: ModificationType.MODIFY
diff: @@ -146,11 +146,11 @@ void nautilus_file_operations_link      (GList                *files,
 					 GtkWindow            *parent_window,
 					 NautilusCopyCallback  done_callback,
 					 gpointer              done_callback_data);
-void nautilus_file_mark_desktop_file_trusted (GFile           *file,
-					      GtkWindow        *parent_window,
-					      gboolean          interactive,
-					      NautilusOpCallback done_callback,
-					      gpointer          done_callback_data);
+void nautilus_file_mark_desktop_file_executable (GFile           *file,
+                                                 GtkWindow        *parent_window,
+                                                 gboolean          interactive,
+                                                 NautilusOpCallback done_callback,
+                                                 gpointer          done_callback_data);
 void nautilus_file_operations_extract_files (GList                   *files,
                                              GFile                   *destination_directory,
                                              GtkWindow               *parent_window,

programming_language: C
filename: nautilus-metadata.c
change_type: ModificationType.MODIFY
diff: @@ -51,6 +51,7 @@ static char *used_metadata_names[] =
     NAUTILUS_METADATA_KEY_CUSTOM_ICON_NAME,
     NAUTILUS_METADATA_KEY_SCREEN,
     NAUTILUS_METADATA_KEY_EMBLEMS,
+    NAUTILUS_METADATA_KEY_DESKTOP_FILE_TRUSTED,
     NULL
 };
 

programming_language: C
filename: nautilus-metadata.h
change_type: ModificationType.MODIFY
diff: @@ -67,6 +67,8 @@
 #define NAUTILUS_METADATA_KEY_SCREEN				"screen"
 #define NAUTILUS_METADATA_KEY_EMBLEMS				"emblems"
 
+#define NAUTILUS_METADATA_KEY_DESKTOP_FILE_TRUSTED				"trusted"
+
 guint nautilus_metadata_get_id (const char *metadata);
 
 #endif /* NAUTILUS_METADATA_H */

programming_language: Shell
filename: nautilus-mime-actions.c
change_type: ModificationType.MODIFY
diff: @@ -42,6 +42,7 @@
 #include "nautilus-program-choosing.h"
 #include "nautilus-global-preferences.h"
 #include "nautilus-signaller.h"
+#include "nautilus-metadata.h"
 
 #define DEBUG_FLAG NAUTILUS_DEBUG_MIME
 #include "nautilus-debug.h"
@@ -221,7 +222,6 @@ struct
 #define RESPONSE_RUN 1000
 #define RESPONSE_DISPLAY 1001
 #define RESPONSE_RUN_IN_TERMINAL 1002
-#define RESPONSE_MARK_TRUSTED 1003
 
 #define SILENT_WINDOW_OPEN_LIMIT 5
 #define SILENT_OPEN_LIMIT 5
@@ -1517,24 +1517,35 @@ untrusted_launcher_response_callback (GtkDialog                 *dialog,
 
     switch (response_id)
     {
-        case RESPONSE_RUN:
+        case GTK_RESPONSE_OK:
         {
+            file = nautilus_file_get_location (parameters->file);
+
+            /* We need to do this in order to prevent malicious desktop files
+             * with the executable bit already set.
+             * See https://bugzilla.gnome.org/show_bug.cgi?id=777991
+             */
+            nautilus_file_set_metadata (parameters->file, NAUTILUS_METADATA_KEY_DESKTOP_FILE_TRUSTED,
+                                        NULL,
+                                        "yes");
+
+            nautilus_file_mark_desktop_file_executable (file,
+                                                        parameters->parent_window,
+                                                        TRUE,
+                                                        NULL, NULL);
+
+            /* Need to force a reload of the attributes so is_trusted is marked
+             * correctly. Not sure why the general monitor doesn't fire in this
+             * case when setting the metadata
+             */
+            nautilus_file_invalidate_all_attributes (parameters->file);
+
             screen = gtk_widget_get_screen (GTK_WIDGET (parameters->parent_window));
             uri = nautilus_file_get_uri (parameters->file);
             DEBUG ("Launching untrusted launcher %s", uri);
             nautilus_launch_desktop_file (screen, uri, NULL,
                                           parameters->parent_window);
             g_free (uri);
-        }
-        break;
-
-        case RESPONSE_MARK_TRUSTED:
-        {
-            file = nautilus_file_get_location (parameters->file);
-            nautilus_file_mark_desktop_file_trusted (file,
-                                                     parameters->parent_window,
-                                                     TRUE,
-                                                     NULL, NULL);
             g_object_unref (file);
         }
         break;
@@ -1590,17 +1601,16 @@ activate_desktop_file (ActivateParameters *parameters,
                       "text", primary,
                       "secondary-text", secondary,
                       NULL);
+
         gtk_dialog_add_button (GTK_DIALOG (dialog),
-                               _("_Launch Anyway"), RESPONSE_RUN);
+                               _("_Cancel"), GTK_RESPONSE_CANCEL);
+
+        gtk_dialog_set_default_response (GTK_DIALOG (dialog), GTK_RESPONSE_CANCEL);
         if (nautilus_file_can_set_permissions (file))
         {
             gtk_dialog_add_button (GTK_DIALOG (dialog),
-                                   _("Mark as _Trusted"), RESPONSE_MARK_TRUSTED);
+                                   _("Trust and _Launch"), GTK_RESPONSE_OK);
         }
-        gtk_dialog_add_button (GTK_DIALOG (dialog),
-                               _("_Cancel"), GTK_RESPONSE_CANCEL);
-        gtk_dialog_set_default_response (GTK_DIALOG (dialog), GTK_RESPONSE_CANCEL);
-
         g_signal_connect (dialog, "response",
                           G_CALLBACK (untrusted_launcher_response_callback),
                           parameters_desktop);

programming_language: C++