Internet-Draft ACVP SHA October 2021
Celi Expires 24 April 2022 [Page]
Workgroup:
Network Working Group
Internet-Draft:
draft-ietf-acvp-sub-sha-01
:
Published:
Intended Status:
Informational
Expires:
Author:
C. Celi, Ed.

ACVP Secure Hash Algorithm (SHA) JSON Specification

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

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This Internet-Draft will expire on 24 April 2022.

Table of Contents

1. Acknowledgements

There are no acknowledgements.

2. Abstract

This document defines the JSON schema for testing Secure Hash Algorithm (SHA) implementations with the ACVP specification.

3. Introduction

The Automated Crypto Validation Protocol (ACVP) defines a mechanism to automatically verify the cryptographic implementation of a software or hardware crypto module. The ACVP specification defines how a crypto module communicates with an ACVP server, including crypto capabilities negotiation, session management, authentication, vector processing and more. The ACVP specification does not define algorithm specific JSON constructs for performing the crypto validation. A series of ACVP sub-specifications define the constructs for testing individual crypto algorithms. Each sub-specification addresses a specific class of crypto algorithms. This sub-specification defines the JSON constructs for testing Secure Hash Algorithm (SHA) implementations using ACVP.

4. Conventions

4.1. Notation conventions

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 of [RFC2119] and [RFC8174] when, and only when, they appear in all capitals, as shown here.

4.2. Terms and Definitions

4.2.1. Prompt

JSON sent from the server to the client describing the tests the client performs

4.2.2. Registration

The initial request from the client to the server describing the capabilities of one or several algorithm, mode and revision combinations

4.2.3. Response

JSON sent from the client to the server in response to the prompt

4.2.4. Test Case

An individual unit of work within a prompt or response

4.2.5. Test Group

A collection of test cases that share similar properties within a prompt or response

4.2.6. Test Vector Set

A collection of test groups under a specific algorithm, mode, and revision

4.2.7. Validation

JSON sent from the server to the client that specifies the correctness of the response

5. Supported Hash Algorithms

The following hash algorithms MAY be advertised by the ACVP compliant cryptographic module:

6. Test Types and Test Coverage

This section describes the design of the tests used to validate implementations of SHA-1 and SHA-2.

6.1. Test Types

There are two types of tests for SHA-1 and SHA-2: functional tests and Monte Carlo tests. Each has a specific value to be used in the testType field. The testType field definitions are:

  • "AFT" - Algorithm Functional Test. These tests can be processed by the client using a normal 'hash' operation. AFTs cause the implementation under test to exercise normal operations on a single block, multiple blocks, or partial blocks. In all cases, random data is used. The functional tests are designed to verify that the logical components of the hash function (block chunking, block padding etc.) are operating correctly.

  • "MCT" - Monte Carlo Test. These tests exercise the implementation under test under stenuous circumstances. The implementation under test must process the test vectors according to the correct algorithm and mode in this document. MCTs can help detect potential memory leaks over time, and problems in allocation of resources, addressing variables, error handling, and generally improper behavior in response to random inputs. Each MCT processes 100 pseudorandom tests. Each algorithm and mode SHOULD have at least one MCT group. See Section 6.2 for implementation details.

  • "LDT" - Large Data Test. This test performs the hash function on a message that is multiple gigabytes in length. This pushes the bounds of 32-bit data types to ensure an implementation can handle all types of data. See [LDT] for more information motivating the LDT. As a multiple gigabyte message cannot be communicated naturally via ACVP, a specific structure is outlined in Section 6.3.

6.2. Monte Carlo tests for SHA-1 and SHA-2

The MCTs start with an initial condition (SEED which is a single message) and perform a series of chained computations. The algorithm is shown below.

For j = 0 to 99
MD[0] = MD[1] = MD[2] = SEED
        For i = 3 to 1003
                MSG[i] = MD[i-3] || MD[i-2] || MD[i-1]
                MD[i] = SHA(MSG[i])
        Output MD[1002]
    SEED = MD[1002]

6.3. Large Data tests for SHA-1 and SHA-2

The large data tests are intended to test the ability of a module to hash multiple gigabytes of data at once. This much information cannot be communicated via the JSON files as a normal message property. Instead a new type is defined as a large data type. It is an object that contains a small content hex string, a content length in bits, a full length in bits and an expansion technique string. The following is an example of this structure.

"largeMsg": {
    "content": "DE26",
    "contentLength": 16,
    "fullLength": 42949672960,
    "expansionTechnique": "repeating"
}

The 'contentLength' property describes the number of bits in the 'content' property. The 'content' property is the hex string that can be expanded to the full large message. The 'expansionTechnique' describes the process used to obtain the full large message. The 'fullLength' is the final length of the full large message.

There may be multiple 'expansionTechnique' types defined. Here are the types defined for SHA-1 and SHA-2 testing.

  • "repeating" - Append the number of content bits specified in 'contentLength' to itself as many times as needed until a hex string of exactly 'fullLength' bits is acquired. In the example shown, the final large message would have the form "DE26DE26DE26...​DE26".

There are multiple ways hash functions can be implemented in an IUT. The most common are via a single Hash() call on the message or via a series of Init(), any number of Update(), Final() calls. As noted in [LDT], the difference between these hashing techniques can have consequences in the cryptographic module. If both interfaces are offered and accessible for testing, the IUT MUST only utilize a single Update() call for the large message.

6.4. Test Coverage

The tests described in this document have the intention of ensuring an implementation is conformant to [FIPS180-4].

6.4.1. SHA Requirements Covered

Section 1 in [FIPS180-4] outlines the maximum message sizes for each hash function. Due to the large size (either 2^64 or 2^128 bits) of these maximums, they are tested by special request in this specification. These tests are performed by the optional LDTs.

Sections 3 and 4 in [FIPS180-4] outline the core functions used within the hash algorithms. Normal AFTs test these operations.

Section 5 outlines the hash function preprocessing. It is worth noting that not all test cases will cover the message padding process, but through the entire vector set, this operation will be fully tested.

6.4.2. SHA Requirements Not Covered

Section 7 outlines digest truncation for applications where a shortened digest is needed. These operations are not tested via this specification.

7. Capabilities Registration

ACVP requires crypto modules to register their capabilities. This allows the crypto module to advertise support for specific algorithms, notifying the ACVP server which algorithms need test vectors generated for the validation process. This section describes the constructs for advertising support of SHA algorithms to the ACVP server.

The algorithm capabilities MUST be advertised as JSON objects within the 'algorithms' value of the ACVP registration message. The 'algorithms' value is an array, where each array element is an individual JSON object defined in this section. The 'algorithms' value is part of the 'capability_exchange' element of the ACVP JSON registration message. See the ACVP specification [ACVP] for more details on the registration message.

7.1. Prerequisites

Each algorithm implementation MAY rely on other cryptographic primitives. For example, RSA Signature algorithms depend on an underlying hash function. Each of these underlying algorithm primitives must be validated, either separately or as part of the same submission. ACVP provides a mechanism for specifying the required prerequisites:

Prerequisites, if applicable, MUST be submitted in the registration as the prereqVals JSON property array inside each element of the algorithms array. Each element in the prereqVals array MUST contain the following properties

Table 1: Prerequisite Properties
JSON Property Description JSON Type
algorithm a prerequisite algorithm string
valValue algorithm validation number string

A "valValue" of "same" SHALL be used to indicate that the prerequisite is being met by a different algorithm in the capability exchange in the same registration.

An example description of prerequisites within a single algorithm capability exchange looks like this

"prereqVals":
[
  {
    "algorithm": "Alg1",
    "valValue": "Val-1234"
  },
  {
    "algorithm": "Alg2",
    "valValue": "same"
  }
]

7.2. HASH Algorithm Capabilities Registration

This section describes the constructs for advertising support of hash algorithms to the ACVP server.

Table 2: Hash Algorithm Capabilities JSON Values
JSON Value Description JSON type
algorithm The hash algorithm and mode to be validated. string
revision The algorithm testing revision to use. string
messageLength The message lengths in bits supported by the IUT. Minimum allowed is 0, maximum allowed is 65535. domain
performLargeDataTest Determines if the server should include the large data test group defined in Section 6.3. This property is OPTIONAL, and shall include the lengths in GiB being tested. Valid options are {1, 2, 4, 8}. integer array

The value of the algorithm property MUST be one of the elements from the list in Section 5.

The following is a example JSON object advertising support for SHA-256.

{
    "algorithm": "SHA2-256",
    "revision": "1.0",
    "messageLength": [{"min": 0, "max": 65535, "increment": 1}],
    "performLargeDataTest": [1, 2]
}

8. Test Vectors

The ACVP server provides test vectors to the ACVP client, which are then processed and returned to the ACVP server for validation. A typical ACVP validation test session would require multiple test vector sets to be downloaded and processed by the ACVP client. Each test vector set represents an individual algorithm defined during the capability exchange. This section describes the JSON schema for a test vector set used with Secure Hash Algorithm (SHA) algorithms.

The test vector set JSON schema is a multi-level hierarchy that contains meta data for the entire vector set as well as individual test vectors to be processed by the ACVP client. The following table describes the JSON elements at the top level of the hierarchy.

Table 3: Top Level Test Vector JSON Elements
JSON Values Description JSON Type
acvVersion Protocol version identifier string
vsId Unique numeric vector set identifier integer
algorithm Algorithm defined in the capability exchange string
mode Mode defined in the capability exchange string
revision Protocol test revision selected string
testGroups Array of test groups containing test data, see Section 8.1 array

An example of this would look like this

{
  "acvVersion": "version",
  "vsId": 1,
  "algorithm": "Alg1",
  "mode": "Mode1",
  "revision": "Revision1.0",
  "testGroups": [ ... ]
}

8.1. Test Groups

Test vector sets MUST contain one or many test groups, each sharing similar properties. For instance, all test vectors that use the same testType would be grouped together. The testGroups element at the top level of the test vector JSON object SHALL be the array of test groups. The Test Group JSON object MUST contain meta-data that applies to all test cases within the group. The following table describes the JSON elements that MAY appear from the server in the Test Group JSON object:

Table 4: Test Group JSON Object
JSON Value Description JSON type
tgId Numeric identifier for the test group, unique across the entire vector set integer
testType Test category type (AFT, MCT or LDT). See Section 6 for more information string
tests Array of individual test case JSON objects, which are defined in Section 8.2 array of testCase objects

All properties described in the previous table MUST appear in the prompt file from the server for every testGroup object.

8.2. Test Case

Each test group SHALL contain an array of one or more test cases. Each test case is a JSON object that represents a single case to be processed by the ACVP client. The following table describes the JSON elements for each test case.

Table 5: Test Case JSON Object
JSON Value Description JSON type
tcId Numeric identifier for the test case, unique across the entire vector set integer
len Length of the message or MCT seed integer
msg Value of the message or MCT seed in big-endian hex integer
largeMsg Object describing the message for an LDT group large data object, see Section 6.3 for more information

All properties described in the previous table MUST appear in the prompt file from the server for every testCase object.

The following is an example JSON object for secure hash test vectors sent from the ACVP server to the crypto module. Note the single bit message is represented as "80". This complies with SHA1 and SHA2 being big-endian by nature. All hex strings associated with SHA1 and SHA2 SHALL be big-endian.

[
    { "acvVersion": <acvp-version> },
    {
        "vsId": 1564,
        "algorithm": "SHA2-512/224",
        "revision": "1.0",
        "testGroups": [
            {
                "tgId": 1,
                "testType": "AFT",
                "tests": [
                    {
                        "tcId": 0,
                        "len": 0,
                        "msg": "00"
                    },
                    {
                        "tcId": 1,
                        "len": 1,
                        "msg": "80"
                    }
                ]
            },
            {
                "tgId": 2,
                "testType": "MCT",
                "tests": [
                    {
                        "tcId": 2175,
                        "len": 20,
                        "msg": "331b04d56f6e3ed5af349bf1fd9f9591b6ec886e",
                    }
                ]
            },
            {
                "tgId": 3,
                "testType": "LDT",
                "tests": [
                    {
                        "tcId": 1029,
                        "largeMsg": {
                            "content": "DE26",
                            "contentLength": 16,
                            "fullLength": 42949672960,
                            "expansionTechnique": "repeating"
                        }
                    }
                ]
            }
        ]
    }
]

8.3. Test Vector Responses

After the ACVP client downloads and processes a vector set, it SHALL send the response vectors back to the ACVP server within the alloted timeframe. The following table describes the JSON object that represents a vector set response.

Table 6: Vector Set Response JSON Object
JSON Value Description JSON type
acvVersion Protocol version identifier string
vsId Unique numeric identifier for the vector set integer
testGroups Array of JSON objects that represent each test vector result, which uses the same JSON schema as defined in Section 8.2 array of testGroup objects

The testGroup Response section is used to organize the ACVP client response in a similar manner to how it receives vectors. Several algorithms SHALL require the client to send back group level properties in its response. This structure helps accommodate that.

Table 7: Vector Set Group Response JSON Object
JSON Value Description JSON type
tgId The test group identifier integer
tests The tests associated to the group specified in tgId array of testCase objects

Each test case is a JSON object that represents a single test object to be processed by the ACVP client.

The following table describes the JSON elements for each test case object.

Table 8: Test Case Results JSON Object
JSON Value Description JSON type
tcId Numeric identifier for the test case, unique across the entire vector set. integer
md The IUT's message digest response to an AFT or LDT test string (hex)
resultsArray Array of JSON objects that represent each iteration of an MCT. Each iteration will contain the msg and md array of objects containing the md

Note: The tcId MUST be included in every test case object sent between the client and the server.

The following is a example JSON object for secure hash test results sent from the crypto module to the ACVP server. The group identified by tgId 1 is a group of AFTs. The group identified by tgId 2 is a group of MCTs. The group identified by tgId 3 is a group of LDTs.

{
    "vsId": 0,
    "algorithm": "SHA2-224",
    "revision": "1.0",
    "testGroups": [
        {
            "tgId": 1,
            "tests": [
                {
                    "tcId": 1,
                    "md": "D14A028C2A3A2BC9476102BB288234C415A2B01F828EA62AC5B3E42F"
                },
                {
                    "tcId": 2,
                    "md": "D14A028C2A3A2BC9476102BB288234C415A2B01F828EA62AC5B3E42F"
                }
            ]
        },
        {
            "tgId": 2,
            "tests": [
                {
                    "tcId": 1028,
                    "resultsArray": [
                        {
                            "md": "E82B1FA3D510C2E423D03CEDF01F66C995CDD573EB63D5A33FDAE640"
                        },
                        {
                            "md": "00179AE4CE57DCBD156B981A414370B5089FA8E1098A05443DF3CD62"
                        },
                        {
                            "md": "8F6C7F546940352613E8389D4F4B87473A57CACD7E289A27E4F51965"
                        }
                    ]
                }
            ]
        },
        {
            "tgId": 3,
            "tests": [
                {
                    "tcId": 1029,
                    "md": "E4F8B44B32F5A25D1F4784601BF095CF5F7C6F4E9EAA1005AD19F09A"
                }
            ]
        }
    ]
}

9. Security Considerations

There are no additional security considerations outside of those outlined in the ACVP document.

10. IANA Considerations

This document does not require any action by IANA.

11. Normative References

[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, IETF RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/info/rfc2119>.
[RFC7991]
Hoffman, P., "The "xml2rfc" Version 3 Vocabulary", RFC 7991, IETF RFC 7991, DOI 10.17487/RFC7991, , <https://www.rfc-editor.org/info/rfc7991>.
[RFC8174]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", RFC 8174, IETF RFC 8174, DOI 10.17487/RFC8174, , <https://www.rfc-editor.org/info/rfc8174>.
[FIPS180-4]
National Institute of Standards and Technology, "Secure Hash Standard (SHS)", NIST FIPS 180-4, .
[ACVP]
Fussell, B., Vassilev, A., and H. Booth, "Automatic Cryptographic Validation Protocol", ACVP, .
[SHAVS]
"The Secure Hash Algorithm Validation System (SHAVS)", NIST SHAVS.
[LDT]
"Extending NIST's CAVP Testing of Cryptographic Hash Function Implementations", LDT.

Author's Address

Christopher Celi (editor)