CVE 2010-4352: Reject deeply nested variants

Add DBUS_INVALID_NESTED_TOO_DEEPLY validity problem and a test that
should generate it.

Previously, we rejected deep nesting in the signature, but
variants allow dynamic message nesting, conditional only
on the depth of the message body.

The nesting limit is 64, which was also the limit in static
signatures.  Empirically, dynamic nesting depth observed on my
Fedora 14 system doesn't exceed 2; 64 is really a huge limit.

https://bugs.freedesktop.org/show_bug.cgi?id=32321

Signed-Off-By: Colin Walters <walters@verbum.org>
Signed-off-by: Will Thompson <will.thompson@collabora.co.uk>

diff --git a/dbus/dbus-marshal-validate.c b/dbus/dbus-marshal-validate.c
index aa470fc899cbf813ac0698ddcd67c227d749e60e..b4579978da08539bc48bcc7bb5be4369d2036f4d 100644 (file)
--- a/dbus/dbus-marshal-validate.c
+++ b/dbus/dbus-marshal-validate.c
@@ -291,16 +291,30 @@ out:
   return result;
 }
 
+/* note: this function is also used to validate the header's values,
+ * since the header is a valid body with a particular signature.
+ */
 static DBusValidity
 validate_body_helper (DBusTypeReader       *reader,
                       int                   byte_order,
                       dbus_bool_t           walk_reader_to_end,
+                      int                   total_depth,
                       const unsigned char  *p,
                       const unsigned char  *end,
                       const unsigned char **new_p)
 {
   int current_type;
 
+  /* The spec allows arrays and structs to each nest 32, for total
+   * nesting of 2*32. We want to impose the same limit on "dynamic"
+   * value nesting (not visible in the signature) which is introduced
+   * by DBUS_TYPE_VARIANT.
+   */
+  if (total_depth > (DBUS_MAXIMUM_TYPE_RECURSION_DEPTH * 2))
+    {
+      return DBUS_INVALID_NESTED_TOO_DEEPLY;
+    }
+
   while ((current_type = _dbus_type_reader_get_current_type (reader)) != DBUS_TYPE_INVALID)
     {
       const unsigned char *a;
@@ -477,7 +491,9 @@ validate_body_helper (DBusTypeReader       *reader,
                   {
                     while (p < array_end)
                       {
-                        validity = validate_body_helper (&sub, byte_order, FALSE, p, end, &p);
+                        validity = validate_body_helper (&sub, byte_order, FALSE,
+                                                         total_depth + 1,
+                                                         p, end, &p);
                         if (validity != DBUS_VALID)
                           return validity;
                       }
@@ -594,7 +610,9 @@ validate_body_helper (DBusTypeReader       *reader,
 
             _dbus_assert (_dbus_type_reader_get_current_type (&sub) != DBUS_TYPE_INVALID);
 
-            validity = validate_body_helper (&sub, byte_order, FALSE, p, end, &p);
+            validity = validate_body_helper (&sub, byte_order, FALSE,
+                                             total_depth + 1,
+                                             p, end, &p);
             if (validity != DBUS_VALID)
               return validity;
 
@@ -623,7 +641,9 @@ validate_body_helper (DBusTypeReader       *reader,
 
             _dbus_type_reader_recurse (reader, &sub);
 
-            validity = validate_body_helper (&sub, byte_order, TRUE, p, end, &p);
+            validity = validate_body_helper (&sub, byte_order, TRUE,
+                                             total_depth + 1,
+                                             p, end, &p);
             if (validity != DBUS_VALID)
               return validity;
           }
@@ -708,7 +728,7 @@ _dbus_validate_body_with_reason (const DBusString *expected_signature,
   p = _dbus_string_get_const_data_len (value_str, value_pos, len);
   end = p + len;
 
-  validity = validate_body_helper (&reader, byte_order, TRUE, p, end, &p);
+  validity = validate_body_helper (&reader, byte_order, TRUE, 0, p, end, &p);
   if (validity != DBUS_VALID)
     return validity;
   
@@ -878,7 +898,7 @@ _dbus_validity_to_error_message (DBusValidity validity)
     case DBUS_INVALID_DICT_ENTRY_HAS_TOO_MANY_FIELDS:              return "Dict entry has too many fields";
     case DBUS_INVALID_DICT_ENTRY_NOT_INSIDE_ARRAY:                 return "Dict entry not inside array";
     case DBUS_INVALID_DICT_KEY_MUST_BE_BASIC_TYPE:                 return "Dict key must be basic type";
-
+    case DBUS_INVALID_NESTED_TOO_DEEPLY:                           return "Variants cannot be used to create a hugely recursive tree of values";
     default:
       return "Invalid";
     }

diff --git a/dbus/dbus-marshal-validate.h b/dbus/dbus-marshal-validate.h
index 5817de32334169f6501e5a52de040dd99c80203b..8947a2afe38a104db39a05f72986c670eefa29d1 100644 (file)
--- a/dbus/dbus-marshal-validate.h
+++ b/dbus/dbus-marshal-validate.h
@@ -112,6 +112,7 @@ typedef enum
   DBUS_INVALID_DICT_ENTRY_NOT_INSIDE_ARRAY = 54,
   DBUS_INVALID_DICT_KEY_MUST_BE_BASIC_TYPE = 55,
   DBUS_INVALID_MISSING_UNIX_FDS = 56,
+  DBUS_INVALID_NESTED_TOO_DEEPLY = 57,
   DBUS_VALIDITY_LAST
 } DBusValidity;
 

diff --git a/dbus/dbus-message-factory.c b/dbus/dbus-message-factory.c
index 7432cf2748e9af55652da7b9b1c5b2612fb28755..7ecf82700cd2bc84586a13d26d8d5699177891cd 100644 (file)
--- a/dbus/dbus-message-factory.c
+++ b/dbus/dbus-message-factory.c
@@ -333,6 +333,53 @@ simple_error (void)
   return message;
 }
 
+static DBusMessage*
+message_with_nesting_levels (int levels)
+{
+  DBusMessage *message;
+  dbus_int32_t v_INT32;
+  DBusMessageIter *parents;
+  DBusMessageIter *children;
+  int i;
+
+  /* If levels is higher it breaks sig_refcount in DBusMessageRealIter
+   * in dbus-message.c, this assert is just to help you know you need
+   * to fix that if you hit it
+   */
+  _dbus_assert (levels < 256);
+
+  parents = dbus_new(DBusMessageIter, levels + 1);
+  children = dbus_new(DBusMessageIter, levels + 1);
+
+  v_INT32 = 42;
+  message = simple_method_call ();
+
+  i = 0;
+  dbus_message_iter_init_append (message, &parents[i]);
+  while (i < levels)
+    {
+      dbus_message_iter_open_container (&parents[i], DBUS_TYPE_VARIANT,
+                                        i == (levels - 1) ?
+                                        DBUS_TYPE_INT32_AS_STRING :
+                                        DBUS_TYPE_VARIANT_AS_STRING,
+                                        &children[i]);
+      ++i;
+      parents[i] = children[i-1];
+    }
+  --i;
+  dbus_message_iter_append_basic (&children[i], DBUS_TYPE_INT32, &v_INT32);
+  while (i >= 0)
+    {
+      dbus_message_iter_close_container (&parents[i], &children[i]);
+      --i;
+    }
+
+  dbus_free(parents);
+  dbus_free(children);
+
+  return message;
+}
+
 static dbus_bool_t
 generate_special (DBusMessageDataIter   *iter,
                   DBusString            *data,
@@ -735,6 +782,24 @@ generate_special (DBusMessageDataIter   *iter,
       
       *expected_validity = DBUS_INVALID_DICT_ENTRY_HAS_NO_FIELDS;
     }
+  else if (item_seq == 20)
+    {
+      /* 64 levels of nesting is OK */
+      message = message_with_nesting_levels(64);
+
+      generate_from_message (data, expected_validity, message);
+
+      *expected_validity = DBUS_VALID;
+    }
+  else if (item_seq == 21)
+    {
+      /* 65 levels of nesting is not OK */
+      message = message_with_nesting_levels(65);
+
+      generate_from_message (data, expected_validity, message);
+
+      *expected_validity = DBUS_INVALID_NESTED_TOO_DEEPLY;
+    }
   else
     {
       return FALSE;

diff --git a/doc/dbus-specification.xml b/doc/dbus-specification.xml
index 9a5d70ca29f8213a28d0428691b3fabd551d627c..ee5aac5869cd3944ed5f8cdffdc82a8486d82a6a 100644 (file)
--- a/doc/dbus-specification.xml
+++ b/doc/dbus-specification.xml
@@ -620,12 +620,14 @@
              </row><row>
                 <entry><literal>VARIANT</literal></entry>
                 <entry>
-                  A variant type has a marshaled <literal>SIGNATURE</literal>
-                  followed by a marshaled value with the type
-                  given in the signature.
-                  Unlike a message signature, the variant signature 
-                  can contain only a single complete type.
-                  So "i", "ai" or "(ii)" is OK, but "ii" is not.
+                  A variant type has a marshaled
+                  <literal>SIGNATURE</literal> followed by a marshaled
+                  value with the type given in the signature.  Unlike
+                  a message signature, the variant signature can
+                  contain only a single complete type.  So "i", "ai"
+                  or "(ii)" is OK, but "ii" is not.  Use of variants may not
+                  cause a total message depth to be larger than 64, including
+                 other container types such as structures.
                 </entry>
                 <entry>
                   1 (alignment of the signature)