CVE-2020-15206 (published 2020-09-25T19:15Z)

In Tensorflow before versions 1.15.4, 2.0.3, 2.1.2, 2.2.1 and 2.3.1, changing the TensorFlow's `SavedModel` protocol buffer and altering the name of required keys results in segfaults and data corruption while loading the model. This can cause a denial of service in products using `tensorflow-serving` or other inference-as-a-service installments. Fixed were added in commits f760f88b4267d981e13f4b302c437ae800445968 and fcfef195637c6e365577829c4d67681695956e7d (both going into TensorFlow 2.2.0 and 2.3.0 but not yet backported to earlier versions). However, this was not enough, as #41097 reports a different failure mode. The issue is patched in commit adf095206f25471e864a8e63a0f1caef53a0e3a6, and is released in TensorFlow versions 1.15.4, 2.0.3, 2.1.2, 2.2.1, or 2.3.1.

Severity: MEDIUM
CVSS v2 base score: 5.0 (AV:N/AC:L/Au:N/C:N/I:N/A:P)
CVSS v3 base score: 7.5, HIGH (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)

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/tensorflow/tensorflow
commit_details: repo_url: https://github.com/tensorflow/tensorflow
author: Mihai Maruseac
author_date: 2020-09-18 15:10:57-07:00
msg: Validate `NodeDef`s from `FunctionDefLibrary` of a `GraphDef`.

We already validated `NodeDef`s from a `GraphDef` but missed validating those from the `FunctionDefLibrary`. Thus, some maliciously crafted models could evade detection and cause denial of service due to a `CHECK`-fail.

PiperOrigin-RevId: 332536309
Change-Id: I052efe919ff1fe2f90815e286a1aa4c54c7b94ff
repository: repo_url: https://github.com/tensorflow/tensorflow
repo_name: tensorflow/tensorflow
description: An Open Source Machine Learning Framework for Everyone
repo_language: C++
owner: tensorflow
file_changes: filename: loader.cc
change_type: ModificationType.MODIFY
diff: @@ -21,6 +21,7 @@ limitations under the License.
 #include "tensorflow/cc/saved_model/loader_util.h"
 #include "tensorflow/cc/saved_model/reader.h"
 #include "tensorflow/core/framework/attr_value.pb.h"
+#include "tensorflow/core/framework/function.pb.h"
 #include "tensorflow/core/framework/node_def.pb.h"
 #include "tensorflow/core/framework/tensor.pb.h"
 #include "tensorflow/core/lib/io/path.h"
@@ -73,26 +74,41 @@ uint64 GetLatencyMicroseconds(const uint64 start_microseconds) {
 // Ensure that constant tensors loaded from the saved model have valid shape.
 // Also ensure that constant nodes have a value assigned to them.
 // TODO(b/154763635): this is temporary and will be replaced with a better audit
+static Status ValidateNode(const NodeDef& node) {
+  const auto node_iterator = node.attr().find("value");
+  if (node_iterator != node.attr().end()) {
+    AttrValue node_value = node_iterator->second;
+    if (node_value.has_tensor()) {
+      const PartialTensorShape node_shape(node_value.tensor().tensor_shape());
+      if (node_shape.num_elements() < 0) {
+        return errors::FailedPrecondition(
+            "Saved model contains node \"", node.name(), "\" (op \"", node.op(),
+            "\") which initializes from a tensor with ",
+            node_shape.num_elements(), " elements");
+      }
+    }
+  } else if (node.op() == "Const") {
+    return errors::FailedPrecondition(
+        "Saved model contains node \"", node.name(),
+        "\" which is a constant tensor but no value has been provided");
+  }
+  return Status::OK();
+}
+
 static Status ValidateSavedTensors(const GraphDef& graph_def) {
   for (const auto& node : graph_def.node()) {
-    const auto node_iterator = node.attr().find("value");
-    if (node_iterator != node.attr().end()) {
-      AttrValue node_value = node_iterator->second;
-      if (node_value.has_tensor()) {
-        const PartialTensorShape node_shape(node_value.tensor().tensor_shape());
-        if (node_shape.num_elements() < 0) {
-          return errors::FailedPrecondition(
-              "Saved model contains node \"", node.name(), "\" (op \"",
-              node.op(), "\") which initializes from a tensor with ",
-              node_shape.num_elements(), " elements");
-        }
+    TF_RETURN_IF_ERROR(ValidateNode(node));
+  }
+
+  if (graph_def.has_library()) {
+    const FunctionDefLibrary& library = graph_def.library();
+    for (const auto& function : library.function()) {
+      for (const auto& node : function.node_def()) {
+        TF_RETURN_IF_ERROR(ValidateNode(node));
       }
-    } else if (node.op() == "Const") {
-      return errors::FailedPrecondition(
-          "Saved model contains node \"", node.name(),
-          "\" which is a constant tensor but no value has been provided");
     }
   }
+
   return Status::OK();
 }
 

programming_language: C++
filename: saved_model_bundle_test.cc
change_type: ModificationType.MODIFY
diff: @@ -45,6 +45,8 @@ constexpr char kTestFuzzGeneratedNegativeShape[] =
     "cc/saved_model/testdata/fuzz_generated/negative_shape";
 constexpr char kTestFuzzGeneratedConstWithNoValue[] =
     "cc/saved_model/testdata/fuzz_generated/const_with_no_value";
+constexpr char kTestFuzzGeneratedBadNodeAttr[] =
+    "cc/saved_model/testdata/fuzz_generated/bad_node_attr";
 
 class LoaderTest : public ::testing::Test {
  protected:
@@ -328,5 +330,20 @@ TEST_F(LoaderTest, ConstNoValue) {
       std::string::npos);
 }
 
+TEST_F(LoaderTest, BadNodeAttr) {
+  SavedModelBundle bundle;
+  RunOptions run_options;
+  SessionOptions session_options;
+
+  const string export_dir =
+      io::JoinPath(testing::TensorFlowSrcRoot(), kTestFuzzGeneratedBadNodeAttr);
+  Status st = LoadSavedModel(session_options, run_options, export_dir,
+                             {kSavedModelTagServe}, &bundle);
+  EXPECT_FALSE(st.ok());
+  EXPECT_NE(
+      st.error_message().find("constant tensor but no value has been provided"),
+      std::string::npos);
+}
+
 }  // namespace
 }  // namespace tensorflow

programming_language: C++