From 7814554e0827ece778ca88fd90832bd4d05520b1 Mon Sep 17 00:00:00 2001

From: Jakub Filak <jfilak@redhat.com>

Date: Fri, 24 Apr 2015 13:48:32 +0200

Subject: [ABRT PATCH] dbus: avoid race-conditions in tests for dum dir

 availability

Florian Weimer <fweimer@redhat.com>

    dump_dir_accessible_by_uid() is fundamentally insecure because it

    opens up a classic time-of-check-time-of-use race between this

    function and and dd_opendir().

Related: #1214745

Signed-off-by: Jakub Filak <jfilak@redhat.com>

---

 src/dbus/abrt-dbus.c  | 66 ++++++++++++++++++++++++++++++++++++++++++++-------

 src/lib/problem_api.c | 15 ++++++++++--

 2 files changed, 71 insertions(+), 10 deletions(-)

diff --git a/src/dbus/abrt-dbus.c b/src/dbus/abrt-dbus.c

index 7400dff..9e1844a 100644

--- a/src/dbus/abrt-dbus.c

+++ b/src/dbus/abrt-dbus.c

@@ -245,7 +245,15 @@ static struct dump_dir *open_directory_for_modification_of_element(

         }

     }

-    if (!dump_dir_accessible_by_uid(problem_id, caller_uid))

+    int dir_fd = dd_openfd(problem_id);

+    if (dir_fd < 0)

+    {

+        perror_msg("can't open problem directory '%s'", problem_id);

+        return_InvalidProblemDir_error(invocation, problem_id);

+        return NULL;

+    }

+

+    if (!fdump_dir_accessible_by_uid(dir_fd, caller_uid))

     {

         if (errno == ENOTDIR)

         {

@@ -260,10 +268,11 @@ static struct dump_dir *open_directory_for_modification_of_element(

                                 _("Not Authorized"));

         }

+        close(dir_fd);

         return NULL;

     }

-    struct dump_dir *dd = dd_opendir(problem_id, /* flags : */ 0);

+    struct dump_dir *dd = dd_fdopendir(dir_fd, problem_id, /* flags : */ 0);

     if (!dd)

     {   /* This should not happen because of the access check above */

         log_notice("Can't access the problem '%s' for modification", problem_id);

@@ -429,7 +438,15 @@ static void handle_method_call(GDBusConnection *connection,

             return;

         }

-        int ddstat = dump_dir_stat_for_uid(problem_dir, caller_uid);

+        int dir_fd = dd_openfd(problem_dir);

+        if (dir_fd < 0)

+        {

+            perror_msg("can't open problem directory '%s'", problem_dir);

+            return_InvalidProblemDir_error(invocation, problem_dir);

+            return;

+        }

+

+        int ddstat = fdump_dir_stat_for_uid(dir_fd, caller_uid);

         if (ddstat < 0)

         {

             if (errno == ENOTDIR)

@@ -443,6 +460,7 @@ static void handle_method_call(GDBusConnection *connection,

             return_InvalidProblemDir_error(invocation, problem_dir);

+            close(dir_fd);

             return;

         }

@@ -450,6 +468,7 @@ static void handle_method_call(GDBusConnection *connection,

         {   //caller seems to be in group with access to this dir, so no action needed

             log_notice("caller has access to the requested directory %s", problem_dir);

             g_dbus_method_invocation_return_value(invocation, NULL);

+            close(dir_fd);

             return;

         }

@@ -460,10 +479,11 @@ static void handle_method_call(GDBusConnection *connection,

             g_dbus_method_invocation_return_dbus_error(invocation,

                                               "org.freedesktop.problems.AuthFailure",

                                               _("Not Authorized"));

+            close(dir_fd);

             return;

         }

-        struct dump_dir *dd = dd_opendir(problem_dir, DD_OPEN_READONLY | DD_FAIL_QUIETLY_EACCES);

+        struct dump_dir *dd = dd_fdopendir(dir_fd, problem_dir, DD_OPEN_READONLY | DD_FAIL_QUIETLY_EACCES);

         if (!dd)

         {

             return_InvalidProblemDir_error(invocation, problem_dir);

@@ -497,12 +517,21 @@ static void handle_method_call(GDBusConnection *connection,

             return;

         }

-        if (!dump_dir_accessible_by_uid(problem_dir, caller_uid))

+        int dir_fd = dd_openfd(problem_dir);

+        if (dir_fd < 0)

+        {

+            perror_msg("can't open problem directory '%s'", problem_dir);

+            return_InvalidProblemDir_error(invocation, problem_dir);

+            return;

+        }

+

+        if (!fdump_dir_accessible_by_uid(dir_fd, caller_uid))

         {

             if (errno == ENOTDIR)

             {

                 log_notice("Requested directory does not exist '%s'", problem_dir);

                 return_InvalidProblemDir_error(invocation, problem_dir);

+                close(dir_fd);

                 return;

             }

@@ -512,11 +541,12 @@ static void handle_method_call(GDBusConnection *connection,

                 g_dbus_method_invocation_return_dbus_error(invocation,

                                                   "org.freedesktop.problems.AuthFailure",

                                                   _("Not Authorized"));

+                close(dir_fd);

                 return;

             }

         }

-        struct dump_dir *dd = dd_opendir(problem_dir, DD_OPEN_READONLY | DD_FAIL_QUIETLY_EACCES);

+        struct dump_dir *dd = dd_fdopendir(dir_fd, problem_dir, DD_OPEN_READONLY | DD_FAIL_QUIETLY_EACCES);

         if (!dd)

         {

             return_InvalidProblemDir_error(invocation, problem_dir);

@@ -677,20 +707,40 @@ static void handle_method_call(GDBusConnection *connection,

         for (GList *l = problem_dirs; l; l = l->next)

         {

             const char *dir_name = (const char*)l->data;

-            if (!dump_dir_accessible_by_uid(dir_name, caller_uid))

+

+            int dir_fd = dd_openfd(dir_name);

+            if (dir_fd < 0)

+            {

+                perror_msg("can't open problem directory '%s'", dir_name);

+                return_InvalidProblemDir_error(invocation, dir_name);

+                return;

+            }

+

+            if (!fdump_dir_accessible_by_uid(dir_fd, caller_uid))

             {

                 if (errno == ENOTDIR)

                 {

                     log_notice("Requested directory does not exist '%s'", dir_name);

+                    close(dir_fd);

                     continue;

                 }

                 if (polkit_check_authorization_dname(caller, "org.freedesktop.problems.getall") != PolkitYes)

                 { // if user didn't provide correct credentials, just move to the next dir

+                    close(dir_fd);

                     continue;

                 }

             }

-            delete_dump_dir(dir_name);

+

+            struct dump_dir *dd = dd_fdopendir(dir_fd, dir_name, /*flags:*/ 0);

+            if (dd)

+            {

+                if (dd_delete(dd) != 0)

+                {

+                    error_msg("Failed to delete problem directory '%s'", dir_name);

+                    dd_close(dd);

+                }

+            }

         }

         g_dbus_method_invocation_return_value(invocation, NULL);

diff --git a/src/lib/problem_api.c b/src/lib/problem_api.c

index c2b4b1c..b343882 100644

--- a/src/lib/problem_api.c

+++ b/src/lib/problem_api.c

@@ -46,7 +46,15 @@ int for_each_problem_in_dir(const char *path,

             continue; /* skip "." and ".." */

         char *full_name = concat_path_file(path, dent->d_name);

-        if (caller_uid == -1 || dump_dir_accessible_by_uid(full_name, caller_uid))

+

+        int dir_fd = dd_openfd(full_name);

+        if (dir_fd < 0)

+        {

+            VERB2 perror_msg("can't open problem directory '%s'", full_name);

+            continue;

+        }

+

+        if (caller_uid == -1 || fdump_dir_accessible_by_uid(dir_fd, caller_uid))

         {

             /* Silently ignore *any* errors, not only EACCES.

              * We saw "lock file is locked by process PID" error

@@ -54,7 +62,7 @@ int for_each_problem_in_dir(const char *path,

              */

             int sv_logmode = logmode;

             logmode = 0;

-            struct dump_dir *dd = dd_opendir(full_name, DD_OPEN_READONLY | DD_FAIL_QUIETLY_EACCES | DD_DONT_WAIT_FOR_LOCK);

+            struct dump_dir *dd = dd_fdopendir(dir_fd, full_name, DD_OPEN_READONLY | DD_FAIL_QUIETLY_EACCES | DD_DONT_WAIT_FOR_LOCK);

             logmode = sv_logmode;

             if (dd)

             {

@@ -62,6 +70,9 @@ int for_each_problem_in_dir(const char *path,

                 dd_close(dd);

             }

         }

+        else

+            close(dir_fd);

+

         free(full_name);

         if (brk)

             break;

-- 

1.8.3.1