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Checking references for intended status: Informational ---------------------------------------------------------------------------- == Outdated reference: A later version (-19) exists of draft-ietf-taps-arch-11 == Outdated reference: A later version (-26) exists of draft-ietf-taps-interface-13 Summary: 0 errors (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 taps M. Duke 3 Internet-Draft F5 Networks, Inc. 4 Intended status: Informational 5 October 2021 5 Expires: 8 April 2022 7 TAPS Transport Discovery 8 draft-duke-taps-transport-discovery-01 10 Abstract 12 The Transport Services architecture decouples applications from the 13 protocol implementations that transport their data. While it is 14 often straightforward to connect applications with transports that 15 are present in the host operating system, providing a means of 16 discovering user-installed implementations dramatically enlarges the 17 use cases. This document discusses considerations for the design of 18 a discovery mechanism and an example of such a design. 20 Discussion of this work is encouraged to happen on the TAPS IETF 21 mailing list taps@ietf.org or on the GitHub repository which contains 22 the draft: https://github.com/martinduke/draft-duke-taps-transport- 23 discovery. 25 Discussion Venues 27 This note is to be removed before publishing as an RFC. 29 Discussion of this document takes place on the mailing list 30 (taps@ietf.org), which is archived at 31 https://mailarchive.ietf.org/arch/browse/taps/. 33 Source for this draft and an issue tracker can be found at 34 https://github.com/martinduke/draft-duke-taps-transport-discovery. 36 Status of This Memo 38 This Internet-Draft is submitted in full conformance with the 39 provisions of BCP 78 and BCP 79. 41 Internet-Drafts are working documents of the Internet Engineering 42 Task Force (IETF). Note that other groups may also distribute 43 working documents as Internet-Drafts. The list of current Internet- 44 Drafts is at https://datatracker.ietf.org/drafts/current/. 46 Internet-Drafts are draft documents valid for a maximum of six months 47 and may be updated, replaced, or obsoleted by other documents at any 48 time. It is inappropriate to use Internet-Drafts as reference 49 material or to cite them other than as "work in progress." 51 This Internet-Draft will expire on 8 April 2022. 53 Copyright Notice 55 Copyright (c) 2021 IETF Trust and the persons identified as the 56 document authors. All rights reserved. 58 This document is subject to BCP 78 and the IETF Trust's Legal 59 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 60 license-info) in effect on the date of publication of this document. 61 Please review these documents carefully, as they describe your rights 62 and restrictions with respect to this document. Code Components 63 extracted from this document must include Simplified BSD License text 64 as described in Section 4.e of the Trust Legal Provisions and are 65 provided without warranty as described in the Simplified BSD License. 67 Table of Contents 69 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 70 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3 71 3. Entities . . . . . . . . . . . . . . . . . . . . . . . . . . 4 72 4. Protocol Implementation . . . . . . . . . . . . . . . . . . . 4 73 5. Protocol Installer . . . . . . . . . . . . . . . . . . . . . 5 74 6. TAPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 75 7. Security Considerations . . . . . . . . . . . . . . . . . . . 5 76 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 77 9. Informative References . . . . . . . . . . . . . . . . . . . 6 78 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 7 79 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7 81 1. Introduction 83 The Transport Services architecture [I-D.ietf-taps-arch] enables 84 applications to be protocol-agnostic by presenting an interface where 85 applications can specify their required properties, and the service 86 will select whichever protocol implementation available in the system 87 best meets those requirements. This increases application 88 portability and eases the introduction of new transport innovations 89 by not requiring changes to applications. 91 It is sometimes straightforward for a Transport Services interface to 92 identify the transports available in the host operating system. 93 However, including transports installed by the user greatly expands 94 use cases for the architecture. This document presents 95 considerations for the secure design of a system for discovery of new 96 protocol implementations. 98 Protocol Discovery would ideally have several desirable properties. 100 * The transport services API should not have to recompile when 101 installing new implementations. This would not only disrupt 102 ongoing connections, but also involve ordinary users in the 103 complex business of downloading and building source code. 105 * It should support user-space implementations. Most protocol 106 innovation begins with user space implementations, and many 107 transports (e.g. TLS, HTTP, QUIC) are usually implemented outside 108 the kernel long after reaching maturity. 110 * Protocol Discovery should not subject ordinary users to security 111 vulnerabilities. A new protocol installation is an opportunity to 112 hijack a user's networking stack, and Protocol Discovery requires 113 strong protections against arbitrary code performing operations 114 other than advertised on application data. 116 * Conversely, sophisticated users need a means of discovering 117 implementations that are too new to have fully developed internet 118 trust mechanisms. This is the only means of initially deploying 119 new protocols for existing apps, and is the most plausible model 120 to deploy transport services API shims for existing protocol 121 libraries (e.g., the common TLS implementations) before their 122 proponents deploy native support. 124 * Applications should not have to bring their own implementations. 125 The Transport Services API has the concept of "framers" (see Sec. 126 7.1 of [I-D.ietf-taps-interface]) that provide some ability for 127 applications to provide additional protocol encapsulation around 128 their messages. However, one important advantage of Transport 129 Services is that applications do not have to rely on a third-party 130 implementation that might not offer long term support, or add to 131 their footprint where a functionally equivalent protocol 132 implementation is already present on the system. 134 This document attempts to resolve the tension between some of these 135 properties. 137 2. Conventions 139 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 140 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 141 document are to be interpreted as described in RFC 2119 [RFC2119]. 143 "TAPS" is an abbreviation for the transport services API. 145 For brevity, this document will use "app" as a shorthand for 146 "application." 148 As in other TAPS documents, the concept of a "transport protocol" is 149 expanded beyond the traditional "transport layer" to include other 150 protocols that encapsulate application data, such as TLS, HTTP, and 151 Websockets. 153 3. Entities 155 The Transport Services API (TAPS) is responsible for matching 156 protocol capabilities with application requirements, and mediating 157 further app communication with the selected protocol implementation. 158 In this document, it actively discovers what implementations are 159 available in the system. 161 The protocol implementation instantiates the transport. In this 162 document, it offers a dynamically linked library that conforms to 163 standard interfaces so that TAPS can interchangeability interact with 164 it. In practice, this may be a shim layer if the underlying 165 implementation does not support TAPS. 167 The protocol installer, aside from installing the implementation 168 library and/or a TAPS shim layer, also is responsible for notifying 169 TAPS that the implementation is present, and what its capabilities 170 are. 172 Finally, the application leverages TAPS to initiate, manage, and 173 terminate communications with other endpoints. This document does 174 not require any changes to application behavior beyond those in the 175 core TAPS design. 177 More detailed requirements for each of these entities is below. 179 4. Protocol Implementation 181 The protocol implementation must offer a dynamically linked library 182 that offers certain APIs. 184 These APIs are TBD. 186 5. Protocol Installer 188 The installer might use the operating system's package manager or 189 "app store", or be a simple script. Besides installing the 190 implementation, the installer also writes data to a registry that 191 TAPS will access to discover the implementation. 193 This data will include: 195 * the name of the supported protocol(s); 197 * optionally, the versions of those protocols; 199 * the path to the implementations TAPS-compliant library; 201 * the properties that the protocol implementation supports, as 202 described in Section 4.2 of [I-D.ietf-taps-interface]; and 204 * information to authenticate the entry (see Section 7). 206 Of course, a de-installer should remove the appropriate registry 207 entry. 209 6. TAPS 211 TAPS creates a registry for protocol implementations, which might be 212 a database or a directory. To prevent inadvertent security 213 vulnerabilities, the host system SHOULD, at minimum, require 214 administrative privileges to write to the registry. 216 No later than upon receipt of request for a Preconnection, TAPS MUST 217 access the registry to determine the available protocols and their 218 properties. It is perfectly valid for there to be multiple 219 implementations of a protocol. 221 TAPS SHOULD validate entries in the registry using the provided 222 authentication data. 224 7. Security Considerations 226 User-space installation of protocols provides enormous opportunities 227 for attackers to hijack a network stack. While this has always been 228 possible with arbitrary protocol implementations, with TAPS 229 applications completely unaware of the installation can be victims of 230 such an attack. 232 An implementation might advertise properties it does not actually 233 provide to attract more traffic. For example, a "TLS" implementation 234 might not encrypt anything at all. 236 Moreover, in principle an implementation could deliver application 237 data anywhere it wanted with little visibility to the application, 238 much less the user. 240 The origin of the protocol installer is important to the trust model. 241 Obviously, transports in the kernel do not introduce vulnerabilities 242 specific to TAPS. A trusted package manager (e.g. the Apple App 243 Store or yum) may imply a minimal level of veracity of the available 244 packages. Protocol implementations directly downloaded from the 245 internet without mediation through these mechanisms require the 246 greatest care. 248 Ongoing work on this document will largely focus on building 249 mechanisms to mitigate this weakness. Some promising approaches 250 include: 252 * administrative privileges to alter the TAPS registry; 254 * a special certificate authority that provides an authentication of 255 the implementation's explicit and implicit claims, as well as the 256 integrity of the installed binary; 258 * each installer generates a private key and provides the 259 corresponding public key, so that only possessors of the private 260 key can modify or delete the registry entry; 262 * confirmation by a human, prominently warned of potential 263 consequences, if the installation is not mediated through a 264 trusted authority. 266 8. IANA Considerations 268 This document has no IANA requirements. 270 9. Informative References 272 [I-D.ietf-taps-arch] 273 Pauly, T., Trammell, B., Brunstrom, A., Fairhurst, G., 274 Perkins, C., Tiesel, P. S., and C. A. Wood, "An 275 Architecture for Transport Services", Work in Progress, 276 Internet-Draft, draft-ietf-taps-arch-11, 12 July 2021, 277 . 280 [I-D.ietf-taps-interface] 281 Trammell, B., Welzl, M., Enghardt, T., Fairhurst, G., 282 Kuehlewind, M., Perkins, C., Tiesel, P. S., Wood, C. A., 283 Pauly, T., and K. Rose, "An Abstract Application Layer 284 Interface to Transport Services", Work in Progress, 285 Internet-Draft, draft-ietf-taps-interface-13, 12 July 286 2021, . 289 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 290 Requirement Levels", BCP 14, RFC 2119, 291 DOI 10.17487/RFC2119, March 1997, 292 . 294 Appendix A. Acknowledgments 296 Tim Worsley contributed important ideas to this document. 298 Author's Address 300 Martin Duke 301 F5 Networks, Inc. 303 Email: martin.h.duke@gmail.com