| Internet-Draft | tigress-sample-implementation | November 2022 |
| Vinokurov, et al. | Expires 13 May 2023 | [Page] |
This document describes a sample implementation of Tigress internet draft [Tigress-00] and a threat model of this implementation.¶
This note is to be removed before publishing as an RFC.¶
The latest revision of this draft can be found at https://github.com/dimmyvi/tigress-sample-implementation. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-tigress-sample-implementation/.¶
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This document provides a sample implementation and threat model for Tigress draft [Tigress-00].¶
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.¶
<html prefix="og: https://ogp.me/ns#"> <head> <title>Shared Key</title> <meta content="Shared Key" property="og:title"/> <meta content="You've been invited to add a shared digital car key to your device." property="og:description"/> <meta content="https://example.com/displayInfo/general.png" property="og:url"/> <meta content="https://example.com/displayInfo/general.png" property="og:image"/> <meta content="200" property="og:image:width"/> <meta content="100" property="og:image:height"/> </head> </html>
Threat model for the sample implementation is provided at the following URL: [threat_model]: https://github.com/dimmyvi/tigress-sample-implementation/blob/main/threat_model.png "Threat model for Tigress sample implementation"¶
| Item | Asset | Threat | Impact | Mitigation | Comment |
|---|---|---|---|---|---|
| 1 | Owner's DCK | Kicking-off arbitrary key sharing by spoofing user identity | DCK becomes shared with arbitrary user/adversary allowing them access to the Owner's car | 1) User auth (face/touch ID), 2) Secure Intent | |
| 2 | Content on Intermediary server | Content recovery by brute forcing secret | Exposure of encrypted content and key redemption | 1) Strong source of randomness for salt, 2) At least 128 bit key length, 3) Limitted TTL of the mailbox | |
| 3 | Content on Intermediary server | Content recovery by intercepting secret | Ability to decrypt content on Intermediary server | 1) Physical separation between content and secret, e.g. secret sent as URI fragment to recipient, 2) Optional second factor(e.g. Device PIN, Activation Options - please refer to CCC Technical Specification) can be proposed to the user via user notification based on security options of selected primary sharing channel (used to share URL with secret) | |
| 4 | Content on Intermediary server | Access to content by multiple arbitrary users/devices | 1) Adversary can go to partner and redeem the shared key, 2) Adversary can send push notifications | 1) Mailboxes identified by version 4 UUID defined in [RFC4122](hard to guess/bruteforce), 2) Mailboxes 'tied' to sender and recipient (trust on first use via deviceClaim), 3) TTL limit for mailboxes, 4) Mailboxes deleted after pass redemption | |
| 5 | Content on Intermediary server | Compromised Intermediary server | 1) Adversary can redeem the sharedKey, 2) Adversary can send push notifications | 1) Separation between content and secret, e.g. secret sent as URI fragment to recipient, 2) TTL limit for mailboxes | |
| 6 | Content on Intermediary server and Push Tokens | Unauthenticated access to mailbox on Intermediary server | 1) Adversary can redeem the sharedKey, 2) Adversary can send push notifications | 1) Mailboxes identified by version 4 UUID defined in [RFC4122](hard to guess/bruteforce), 2) Mailboxes 'tied' to sender and recipient (trust on first use via deviceClaim), 3) TTL limit for mailboxes, 4) Mailboxes deleted after pass redemption | |
| 7 | Content on Intermediary server | User stores non-credential information in mailbox (e.g. "cat pictures") | Service abuse, Adversary can use Intermediary server as cloud storage | 1) Mailboxes have size limit, 2) Mailboxes have TTL | |
| 8 | Device PIN | Receiver device compromised (redemption before friend) | Device PIN can exposure and forwarding to an advarsary | Activation Options as defined in [CCC-Digital-Key-30], Section 11.2 Sharing Principles, subsection 11.2.1.3. Activation Options | |
| 9 | Device PIN | Weak PIN can be easily guessed | Anyone with share URL in their possession can guess the PIN and redeem the key | 1) Use of strong RNG as a source to generate Device PIN, 2) Long enough PIN (e.g. 6 digits) as per [NIST-800-63B] recommendations, 3) Limit the number of retries (e.g. Device PIN retry counter + limit) as per [NIST-800-63B] recommendations | [NIST-800-63B], section 5.1.1.1 Memorized Secret Authenticators |
| 10 | Device PIN | Eavesdropping on weak msg channels/app | PIN exposure would allow one with possession of share URL and Secret to redeem key | In person, out of band PIN transfer, e.g. voice channel | |
| 11 | Device PIN | PIN recovery via timing attack | Adversary with shared URL in possession can recover PIN based on the response delay, in the case where the PIN verification is not invariant | 1) Time invariant compare, 2) PIN retry counter/limit | |
| 12 | Device PIN retry counter/limit | Device PIN brute force | Device PIN successful guess | 1) Use of strong RNG as a source to generate Device PIN, 2) Long enough PIN (e.g. 6 digits) as per [NIST-800-63B] recommendations, 3) Limit the number of retries (e.g. Device PIN retry counter + limit) as per [NIST-800-63B] recommendations | [NIST-800-63B], section 5.1.1.1 Memorized Secret Authenticators |
| 13 | Sharing Invitation | Messaging channel eavesdropping | Share invitation forwarding and DCK redemtion by malicious party | 1) Send invitation and Device PIN via different channels, e.g. Device PIN can be shared out of band (over voice), 2) Use of E2E encrypted msg apps/chhannel | |
| 14 | Sharing Invitation | Voluntary/Involuntary forwarding by Friend | DCK redemption before Friend | Use of messaging apps with anti-forwarding mechanisms(e.g. hide link, copy/past prevention) | |
| 15 | Sharing Invitation | Friend device compromise allow malware to forward invitation to an adversary | Share invitation forwarding and key redemption by malicious party | Activation Options as defined in [CCC-Digital-Key-30], Section 11.2 Sharing Principles, subsection 11.2.1.3. Activation Options | |
| 16 | Sharing Invitation | User mistakenly shares with the wrong person | DCK redemption by adversary/not intended user | 1) Send invitation and Device PIN via different channels, e.g. Device PIN can be shared out of band (over voice), 2) DCK revocation | |
| 17 | Sharing Invitation | Owner device compromise allow malware to forward invitation to an adversary | Share invitation forwarding and key redemption by malicious party | Activation Options as defined in [CCC-Digital-Key-30], Section 11.2 Sharing Principles, subsection 11.2.1.3. Activation Options | |
| 18 | Sharing Invitation | Friend device OEM account take over | DCK provisioning on adversary's device | 1) Binding to deviceClaim, 2) Device PIN shared out of band, 3) Activation Options as defined in [CCC-Digital-Key-30], Section 11.2 Sharing Principles, subsection 11.2.1.3. Activation Options | |
| 19 | User's credentials, payment card details, etc | Phishing attacks leveraging malicious Java Script in preview page | 1) Preview page URL fragement contains encryption key - meaning malicious JS could use key to decrypt contents, 2) Malicious Java Script can phish for user credentials, payment card information, or other sensitive data | 1) Properly vet Java Script that is embedded in the preview page, 2) Define strong content security policy |
TODO Security¶
This document has no IANA actions.¶
TODO acknowledge.¶