Internet-Draft Privacy Pass Issuance April 2022
Celi, et al. Expires 7 October 2022 [Page]
Workgroup:
Network Working Group
Internet-Draft:
draft-ietf-privacypass-protocol-04
Published:
Intended Status:
Informational
Expires:
Authors:
S. Celi
Cloudflare
A. Davidson
Brave Software
A. Faz-Hernandez
Cloudflare
S. Valdez
Google LLC
C. A. Wood
Cloudflare

Privacy Pass Issuance Protocol

Abstract

This document specifies two variants of the the two-message issuance protocol for Privacy Pass tokens: one that produces tokens that are privately verifiable, and another that produces tokens that are publicly verifiable. The privately verifiable issuance protocol optionally supports public metadata during the issuance flow.

Status of This Memo

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

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."

This Internet-Draft will expire on 7 October 2022.

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Table of Contents

1. Introduction

The Privacy Pass protocol provides a privacy-preserving authorization mechanism. In essence, the protocol allows clients to provide cryptographic tokens that prove nothing other than that they have been created by a given server in the past [I-D.ietf-privacypass-architecture].

This document describes the issuance protocol for Privacy Pass. It specifies two variants: one that is privately verifiable based on the oblivious pseudorandom function from [OPRF], and one that is publicly verifiable based on the blind RSA signature scheme [BLINDRSA].

This document DOES NOT cover the architectural framework required for running and maintaining the Privacy Pass protocol in the Internet setting. In addition, it DOES NOT cover the choices that are necessary for ensuring that client privacy leaks do not occur. Both of these considerations are covered in [I-D.ietf-privacypass-architecture].

2. Terminology

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 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

The following terms are used throughout this document.

We assume that all protocol messages are encoded into raw byte format before being sent across the wire.

3. Configuration

Issuers MUST provide one parameter for configuration:

  1. Issuer Request URI: a token request URL for generating access tokens. For example, an Issuer URL might be https://issuer.example.net/example-token-request. This parameter uses resource media type "text/plain".

The Issuer parameters can be obtained from an Issuer via a directory object, which is a JSON object whose field names and values are raw values and URLs for the parameters.

Table 1
Field Name Value
issuer-request-uri Issuer Request URI resource URL as a JSON string

As an example, the Issuer's JSON directory could look like:

 {
    "issuer-request-uri": "https://issuer.example.net/example-token-request"
 }

Issuer directory resources have the media type "application/json" and are located at the well-known location /.well-known/token-issuer-directory.

4. Token Challenge Requirements

Clients receive challenges for tokens, as described in [AUTHSCHEME]. The basic token issuance protocols described in this document can be interactive or non-interactive, and per-origin or cross-origin.

5. Issuance Protocol for Privately Verifiable Tokens with Public Metadata

The Privacy Pass issuance protocol is a two message protocol that takes as input a challenge from the redemption protocol and produces a token, as shown in the figure below.

   Origin          Client                   Issuer
                    (pkI)                 (skI, pkI)
                  +------------------------------------\
  Challenge   ----> TokenRequest ------------->        |
                  |                       (evaluate)   |
    Token    <----+     <--------------- TokenResponse |
                  \------------------------------------/

Issuers provide a Private and Public Key, denoted skI and pkI, respectively, used to produce tokens as input to the protocol. See Section 5.4 for how this key pair is generated.

Clients provide the following as input to the issuance protocol:

Given this configuration and these inputs, the two messages exchanged in this protocol are described below. This section uses notation described in [OPRF], Section 4, including SerializeElement and DeserializeElement, SerializeScalar and DeserializeScalar, and DeriveKeyPair.

5.1. Client-to-Issuer Request

The Client first creates a context as follows:

client_context = SetupVOPRFClient(0x0004, pkI)

Here, 0x0004 is the two-octet identifier corresponding to the OPRF(P-384, SHA-384) ciphersuite in [OPRF]. SetupVOPRFClient is defined in [OPRF], Section 3.2.

The Client then creates an issuance request message for a random value nonce using the input challenge and Issuer key identifier as follows:

nonce = random(32)
context = SHA256(challenge)
token_input = concat(0x0001, nonce, context, key_id)
blind, blinded_element = client_context.Blind(token_input)

The Blind function is defined in [OPRF], Section 3.3.2. If the Blind function fails, the Client aborts the protocol. Otherwise, the Client then creates a TokenRequest structured as follows:

struct {
   uint16_t token_type = 0x0001;
   uint8_t token_key_id;
   uint8_t blinded_msg[Ne];
} TokenRequest;

The structure fields are defined as follows:

  • "token_type" is a 2-octet integer, which matches the type in the challenge.
  • "token_key_id" is the least significant byte of the key_id.
  • "blinded_msg" is the Ne-octet blinded message defined above, computed as SerializeElement(blinded_element). Ne is as defined in [OPRF], Section 4.

The values token_input and blinded_element are stored locally and used later as described in Section 5.3. The Client then generates an HTTP POST request to send to the Issuer, with the TokenRequest as the body. The media type for this request is "message/token-request". An example request is shown below.

:method = POST
:scheme = https
:authority = issuer.example.net
:path = /example-token-request
accept = message/token-response
cache-control = no-cache, no-store
content-type = message/token-request
content-length = <Length of TokenRequest>

<Bytes containing the TokenRequest>

Upon receipt of the request, the Issuer validates the following conditions:

  • The TokenRequest contains a supported token_type.
  • The TokenRequest.token_key_id corresponds to a key ID of a Public Key owned by the issuer.
  • The TokenRequest.blinded_request is of the correct size.

If any of these conditions is not met, the Issuer MUST return an HTTP 400 error to the client.

5.2. Issuer-to-Client Response

Upon receipt of a TokenRequest, the Issuer tries to deseralize TokenRequest.blinded_msg using DeserializeElement from Section 2.1 of [OPRF], yielding blinded_element. If this fails, the Issuer MUST return an HTTP 400 error to the client. Otherwise, if the Issuer is willing to produce a token token to the Client, the Issuer completes the issuance flow by computing a blinded response as follows:

server_context = SetupVOPRFServer(0x0004, skI, pkI)
evaluate_element, proof = server_context.Evaluate(skI, blinded_element)

SetupVOPRFServer is in [OPRF], Section 3.2 and Evaluate is defined in [OPRF], Section 3.3.2. The Issuer then creates a TokenResponse structured as follows:

struct {
   uint8_t evaluate_msg[Nk];
   uint8_t evaluate_proof[Ns+Ns];
} TokenResponse;

The structure fields are defined as follows:

  • "evaluate_msg" is the Ne-octet evaluated messaged, computed as SerializeElement(evaluate_element).
  • "evaluate_proof" is the (Ns+Ns)-octet serialized proof, which is a pair of Scalar values, computed as concat(SerializeScalar(proof[0]), SerializeScalar(proof[1])), where Ns is as defined in [OPRF], Section 4.

The Issuer generates an HTTP response with status code 200 whose body consists of TokenResponse, with the content type set as "message/token-response".

:status = 200
content-type = message/token-response
content-length = <Length of TokenResponse>

<Bytes containing the TokenResponse>

5.3. Finalization

Upon receipt, the Client handles the response and, if successful, deserializes the body values TokenResponse.evaluate_response and TokenResponse.evaluate_proof, yielding evaluated_element and proof. If deserialization of either value fails, the Client aborts the protocol. Otherwise, the Client processes the response as follows:

authenticator = client_context.Finalize(token_input, blind, evaluated_element, blinded_element, proof)

The Finalize function is defined in [OPRF], Section 3.3.2. If this succeeds, the Client then constructs a Token as follows:

struct {
    uint16_t token_type = 0x0001
    uint8_t nonce[32];
    uint8_t challenge_digest[32];
    uint8_t token_key_id[32];
    uint8_t authenticator[Nk];
} Token;

Otherwise, the Client aborts the protocol.

5.4. Issuer Configuration

Issuers are configured with Private and Public Key pairs, each denoted skI and pkI, respectively, used to produce tokens. Each key pair MUST be generated as follows:

seed = random(Ns)
(skI, pkI) = DeriveKeyPair(seed, "PrivacyPass")

The key identifier for this specific key pair, denoted key_id, is computed as follows:

key_id = SHA256(0x0001 || SerializeElement(pkI))

6. Issuance Protocol for Publicly Verifiable Tokens

This section describes a variant of the issuance protocol in Section 5 for producing publicly verifiable tokens. It differs from the previous variant in two important ways:

  1. The output tokens are publicly verifiable by anyone with the Issuer public key; and
  2. The issuance protocol does not admit public or private metadata to bind additional context to tokens.

Otherwise, this variant is nearly identical. In particular, Issuers provide a Private and Public Key, denoted skI and pkI, respectively, used to produce tokens as input to the protocol. See Section 6.4 for how this key pair is generated.

Clients provide the following as input to the issuance protocol:

Given this configuration and these inputs, the two messages exchanged in this protocol are described below.

6.1. Client-to-Issuer Request

The Client first creates an issuance request message for a random value nonce using the input challenge and Issuer key identifier as follows:

nonce = random(32)
context = SHA256(challenge)
token_input = concat(0x0002, nonce, context, key_id)
blinded_msg, blind_inv = rsabssa_blind(pkI, token_input)

The rsabssa_blind function is defined in [BLINDRSA], Section 5.1.1.. The Client then creates a TokenRequest structured as follows:

struct {
   uint16_t token_type = 0x0002
   uint8_t token_key_id;
   uint8_t blinded_msg[Nk];
} TokenRequest;

The structure fields are defined as follows:

  • "token_type" is a 2-octet integer, which matches the type in the challenge.
  • "token_key_id" is the least significant byte of the key_id.
  • "blinded_msg" is the Nk-octet request defined above.

The Client then generates an HTTP POST request to send to the Issuer, with the TokenRequest as the body. The media type for this request is "message/token-request". An example request is shown below, where Nk = 512.

:method = POST
:scheme = https
:authority = issuer.example.net
:path = /example-token-request
accept = message/token-response
cache-control = no-cache, no-store
content-type = message/token-request
content-length = <Length of TokenRequest>

<Bytes containing the TokenRequest>

Upon receipt of the request, the Issuer validates the following conditions:

  • The TokenRequest contains a supported token_type.
  • The TokenRequest.token_key_id corresponds to a key ID of a Public Key owned by the issuer.
  • The TokenRequest.blinded_msg is of the correct size.

If any of these conditions is not met, the Issuer MUST return an HTTP 400 error to the Client, which will forward the error to the client.

6.2. Issuer-to-Client Response

If the Issuer is willing to produce a token token to the Client, the Issuer completes the issuance flow by computing a blinded response as follows:

blind_sig = rsabssa_blind_sign(skI, TokenRequest.blinded_rmsg)

This is encoded and transmitted to the client in the following TokenResponse structure:

struct {
   uint8_t blind_sig[Nk];
} TokenResponse;

The rsabssa_blind_sign function is defined in [BLINDRSA], Section 5.1.2.. The Issuer generates an HTTP response with status code 200 whose body consists of TokenResponse, with the content type set as "message/token-response".

:status = 200
content-type = message/token-response
content-length = <Length of TokenResponse>

<Bytes containing the TokenResponse>

6.3. Finalization

Upon receipt, the Client handles the response and, if successful, processes the body as follows:

authenticator = rsabssa_finalize(pkI, nonce, blind_sig, blind_inv)

The rsabssa_finalize function is defined in [BLINDRSA], Section 5.1.3.. If this succeeds, the Client then constructs a Token as described in [HTTP-Authentication] as follows:

struct {
    uint16_t token_type = 0x0002
    uint8_t nonce[32];
    uint8_t challenge_digest[32];
    uint8_t token_key_id[32];
    uint8_t authenticator[Nk];
} Token;

Otherwise, the Client aborts the protocol.

6.4. Issuer Configuration

Issuers are configured with Private and Public Key pairs, each denoted skI and pkI, respectively, used to produce tokens. Each key pair MUST be generated as as a valid 4096-bit RSA private key according to [TODO]. The key identifier for a keypair (skI, pkI), denoted key_id, is computed as SHA256(encoded_key), where encoded_key is a DER-encoded SubjectPublicKeyInfo object carrying pkI.

7. Security considerations

This document outlines how to instantiate the Issuance protocol based on the VOPRF defined in [OPRF] and blind RSA protocol defnied in [BLINDRSA]. All security considerations described in the VOPRF document also apply in the Privacy Pass use-case. Considerations related to broader privacy and security concerns in a multi-Client and multi-Issuer setting are deferred to the Architecture document [I-D.ietf-privacypass-architecture].

8. IANA considerations

8.1. Token Type

This document updates the "Token Type" Registry with the following values.

Table 2: Token Types
Value Name Publicly Verifiable Public Metadata Private Metadata Nk Reference
0x0001 VOPRF(P-384, SHA-384) N N N 48 Section 5
0x0002 Blind RSA, 4096 Y N N 512 Section 6

8.2. Media Types

This specification defines the following protocol messages, along with their corresponding media types:

  • TokenRequest: "message/token-request"
  • TokenResponse: "message/token-response"

The definition for each media type is in the following subsections.

8.2.1. "message/token-request" media type

Type name:

message

Subtype name:

token-request

Required parameters:

N/A

Optional parameters:

None

Encoding considerations:

only "8bit" or "binary" is permitted

Security considerations:

see Section 7

Interoperability considerations:

N/A

Published specification:

this specification

Applications that use this media type:

N/A

Fragment identifier considerations:

N/A

Additional information:
Magic number(s):
N/A
Deprecated alias names for this type:
N/A
File extension(s):
N/A
Macintosh file type code(s):
N/A
Person and email address to contact for further information:

see Authors' Addresses section

Intended usage:

COMMON

Restrictions on usage:

N/A

Author:

see Authors' Addresses section

Change controller:

IESG

8.2.2. "message/token-response" media type

Type name:

message

Subtype name:

access-token-response

Required parameters:

N/A

Optional parameters:

None

Encoding considerations:

only "8bit" or "binary" is permitted

Security considerations:

see Section 7

Interoperability considerations:

N/A

Published specification:

this specification

Applications that use this media type:

N/A

Fragment identifier considerations:

N/A

Additional information:
Magic number(s):
N/A
Deprecated alias names for this type:
N/A
File extension(s):
N/A
Macintosh file type code(s):
N/A
Person and email address to contact for further information:

see Authors' Addresses section

Intended usage:

COMMON

Restrictions on usage:

N/A

Author:

see Authors' Addresses section

Change controller:

IESG

9. Normative References

[AUTHSCHEME]
Pauly, T., Valdez, S., and C. A. Wood, "The Privacy Pass HTTP Authentication Scheme", Work in Progress, Internet-Draft, draft-pauly-privacypass-auth-scheme-00, , <https://datatracker.ietf.org/doc/html/draft-pauly-privacypass-auth-scheme-00>.
[BLINDRSA]
Denis, F., Jacobs, F., and C. A. Wood, "RSA Blind Signatures", Work in Progress, Internet-Draft, draft-irtf-cfrg-rsa-blind-signatures-03, , <https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-rsa-blind-signatures-03>.
[HTTP-Authentication]
"The Privacy Pass HTTP Authentication Scheme", n.d., <https://datatracker.ietf.org/doc/html/draft-pauly-privacypass-auth-scheme-00>.
[I-D.ietf-privacypass-architecture]
Davidson, A., Iyengar, J., and C. A. Wood, "Privacy Pass Architectural Framework", Work in Progress, Internet-Draft, draft-ietf-privacypass-architecture-03, , <https://datatracker.ietf.org/doc/html/draft-ietf-privacypass-architecture-03>.
[OPRF]
Davidson, A., Faz-Hernandez, A., Sullivan, N., and C. A. Wood, "Oblivious Pseudorandom Functions (OPRFs) using Prime-Order Groups", Work in Progress, Internet-Draft, draft-irtf-cfrg-voprf-09, , <https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-voprf-09>.
[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/rfc/rfc2119>.
[RFC8174]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <https://www.rfc-editor.org/rfc/rfc8174>.

Appendix A. Acknowledgements

The authors of this document would like to acknowledge the helpful feedback and discussions from Benjamin Schwartz, Joseph Salowey, Sofia Celi, and Tara Whalen.

Appendix B. Test Vectors

This section includes test vectors for the two basic issuance protocols specified in this document. Appendix B.1 contains test vectors for token issuance protocol 1 (0x0001), and Appendix B.2 contains test vectors for token issuance protocol 2 (0x0002).

B.1. Issuance Protocol 1 - VOPRF(P-384, SHA-384)

The test vector below lists the following values:

  • skS: The encoded OPRF private key, serialized using SerializeScalar from Section 2.1 of [OPRF] and represented as a hexadecimal string.
  • pkS: The encoded OPRF public key, serialized using SerializeElement from Section 2.1 of [OPRF] and represented as a hexadecimal string.
  • challenge: A random challenge, represented as a hexadecimal string.
  • nonce: The 32-byte client nonce generated according to Section 5.1, represented as a hexadecimal string.
  • blind: The blind used when computing the OPRF blinded message, serialized using SerializeScalar from Section 2.1 of [OPRF] and represented as a hexadecimal string.
  • token_request: The TokenRequest message constructed according to Section 5.1, represented as a hexadecimal string.
  • token_request: The TokenResponse message constructed according to Section 5.2, represented as a hexadecimal string.
  • token: The output Token from the protocol, represented as a hexadecimal string. 
skS: 0177781aeced893dccdf80713d318a801e2a0498240fdcf650304bbbfd0f8d3b5c0
cf6cfee457aaa983ec02ff283b7a9
pkS: 022c63f79ac59c0ba3d204245f676a2133bd6120c90d67afa05cd6f8614294b7366
c252c6458300551b79a4911c2590a36
challenge:
a5d46383359ef34e3c4a7b8d1b3165778bffc9b70c9e6a60dd14143e4c9c9fbd
nonce: 5d4799f8338ddc50a6685f83b8ecd264b2f157015229d12b3384c0f199efe7b8
blind: 0322fec505230992256296063d989b59cc03e83184eb6187076d264137622d202
48e4e525bdc007b80d1560e0a6f49d9
token_request: 00011a02861fd50d14be873611cff0131d2c872c79d0260c6763498a2
a3f14ca926009c0f247653406e1d52b68d61b7ed2bac9ea
token_response: 038e3625b6a769668a99680e46cf9479f5dc1e86d57164ab3b4a569d
dfc486bf1485d4916a5194fdc0518d3e8444968421ba36e8144aa7902705ff0f3cf40586
3d69451a2a7ba210cc45760c2f1a6045134d877b39e8bcbbf920e5de4a3372557debf211
765cd969976860bc039f9082d6a3e03f8e891246240173d2cf3d69a4613b0f8415979029
22e74c7a1f2e4639e4
token: 00015d4799f8338ddc50a6685f83b8ecd264b2f157015229d12b3384c0f199efe
7b8742cdfb0ed756ea680868ef109a280a393e001d2fa56b1be46ecb31fa25e76731a5b1
d698ea7ab843b8e8a71ed9b2fffa70457a43a8fc687939424b29a7554b40fde130ab7a82
2715909cb73f99a45b640ca1c85180ba9ca1a40bab8b664406a34bcbc63b5e2e5c455cea
00001a968f7

B.2. Issuance Protocol 2 - Blind RSA, 4096

The test vector below lists the following values:

  • skS: The PEM-encoded PKCS#8 RSA private key used for signing tokens, represented as a hexadecimal string.
  • pkS: The DER-encoded SubjectPublicKeyInfo object carrying the public key corresponding to skS, as described in Section 6.4, represented as a hexadecimal string.
  • challenge: A random challenge, represented as a hexadecimal string.
  • nonce: The 32-byte client nonce generated according to Section 6.1, represented as a hexadecimal string.
  • blind: The blind used when computing the blind RSA blinded message, represented as a hexadecimal string.
  • salt: The randomly generated 48-byte salt used when encoding the blinded token request message, represented as a hexadecimal string.
  • token_request: The TokenRequest message constructed according to Section 6.1, represented as a hexadecimal string.
  • token_request: The TokenResponse message constructed according to Section 6.2, represented as a hexadecimal string.
  • token: The output Token from the protocol, represented as a hexadecimal string. 
skS: 2d2d2d2d2d424547494e2050524956415445204b45592d2d2d2d2d0a4d49494a517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pkS: 30820252303d06092a864886f70d01010a3030a00d300b060960864801650304020
2a11a301806092a864886f70d010108300b0609608648016503040202a20302013003820
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challenge:
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nonce: 7e0da97bfdc4365a5f40e69262f78b81bcd2f92daf885358d9831874e3dd9d22
blind: cd6d03e332386d0166eb76b8e78522510e5cbdcf49aaac83191ea948a7719e914
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salt: d13a47fa6466a37203e51ac34f7319831b3f04202ff74c98ab18e78088b7ac3014
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token_request: 0002013a370077e8259098e741dcaac8184838b7c995cd82966419064
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token_response: 061780e09bc9b851fe81e7022ee2d55b043198bcb1aa33f761d213a9
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token: 00027e0da97bfdc4365a5f40e69262f78b81bcd2f92daf885358d9831874e3dd9
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68b

Authors' Addresses

Sofía Celi
Cloudflare
Lisbon
Portugal
Alex Davidson
Brave Software
Lisbon
Portugal
Armando Faz-Hernandez
Cloudflare
101 Townsend St
San Francisco,
United States of America
Steven Valdez
Google LLC
Christopher A. Wood
Cloudflare
101 Townsend St
San Francisco,
United States of America

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