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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-16) exists of draft-ietf-sacm-terminology-13 ** Downref: Normative reference to an Informational draft: draft-ietf-sacm-terminology (ref. 'I-D.ietf-sacm-terminology') -- Possible downref: Non-RFC (?) normative reference: ref. 'XEP-0030' -- Possible downref: Non-RFC (?) normative reference: ref. 'XEP-0060' -- Obsolete informational reference (is this intentional?): RFC 5246 (Obsoleted by RFC 8446) Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 MILE N. Cam-Winget, Ed. 3 Internet-Draft S. Appala 4 Intended status: Standards Track S. Pope 5 Expires: May 3, 2018 Cisco Systems 6 P. Saint-Andre 7 Jabber.org 8 October 30, 2017 10 Using XMPP for Security Information Exchange 11 draft-ietf-mile-xmpp-grid-04 13 Abstract 15 This document describes how to use the Extensible Messaging and 16 Presence Protocol (XMPP) as a transport for collecting and 17 distributing security-relevant information between network-connected 18 devices. To illustrate the principles involved, this document 19 describes such a usage for the Incident Object Description Exchange 20 Format (IODEF). 22 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on May 3, 2018. 39 Copyright Notice 41 Copyright (c) 2017 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 58 3. Architecture . . . . . . . . . . . . . . . . . . . . . . . . 4 59 4. Workflow . . . . . . . . . . . . . . . . . . . . . . . . . . 6 60 5. Service Discovery . . . . . . . . . . . . . . . . . . . . . . 6 61 6. IODEF Example . . . . . . . . . . . . . . . . . . . . . . . . 7 62 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 63 8. Security Considerations . . . . . . . . . . . . . . . . . . . 9 64 8.1. Trust Model . . . . . . . . . . . . . . . . . . . . . . . 9 65 8.1.1. Network . . . . . . . . . . . . . . . . . . . . . . . 10 66 8.1.2. XMPP-Grid Platforms . . . . . . . . . . . . . . . . . 10 67 8.1.3. XMPP-Grid Controller . . . . . . . . . . . . . . . . 10 68 8.1.4. Certification Authority . . . . . . . . . . . . . . . 10 69 8.2. Threat Model . . . . . . . . . . . . . . . . . . . . . . 11 70 8.2.1. Network Attacks . . . . . . . . . . . . . . . . . . . 11 71 8.2.2. XMPP-Grid Platforms . . . . . . . . . . . . . . . . . 12 72 8.2.3. XMPP-Grid Controllers . . . . . . . . . . . . . . . . 13 73 8.2.4. Certification Authority . . . . . . . . . . . . . . . 14 74 8.3. Countermeasures . . . . . . . . . . . . . . . . . . . . . 15 75 8.3.1. Securing the XMPP-Grid Transport Protocol . . . . . . 15 76 8.3.2. Securing XMPP-Grid Platforms . . . . . . . . . . . . 16 77 8.3.3. Securing XMPP-Grid Controllers . . . . . . . . . . . 16 78 8.3.4. Limit on search result size . . . . . . . . . . . . . 17 79 8.3.5. Cryptographically random session-id and 80 authentication checks for ARC . . . . . . . . . . . . 17 81 8.3.6. Securing the Certification Authority . . . . . . . . 18 82 8.4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 18 83 9. Privacy Considerations . . . . . . . . . . . . . . . . . . . 19 84 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19 85 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 86 11.1. Normative References . . . . . . . . . . . . . . . . . . 19 87 11.2. Informative References . . . . . . . . . . . . . . . . . 20 88 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 90 1. Introduction 92 This document describes "XMPP-Grid": a method for using the 93 Extensible Messaging and Presence Protocol (XMPP) [RFC6120] as a 94 transport for collecting and distributing security-relevant 95 information among network platforms, endpoints, and any other 96 network-connected device. Among other services, XMPP provides a 97 publish-subscribe service that acts as a broker, providing control- 98 plane functions by which entities can discover available information 99 to be published or consumed. Although such information can take the 100 form of any structured data (XML, JSON, etc.), this document uses the 101 Incident Object Description Exchange Format (IODEF) [RFC7970] to 102 illustrate the principles of XMPP-Grid. 104 2. Terminology 106 This document uses XMPP terminology defined in [RFC6120] and 107 [XEP-0060] as well as Security Automation and Continuous Monitoring 108 (SACM) terminology defined in [I-D.ietf-sacm-terminology]. Because 109 the intended audience for this document consists of those who 110 implement and deploy security reporting systems, in general the SACM 111 terms are used here (however, mappings are provided for the benefit 112 of XMPP developers and operators). 114 Broker: As defined in [I-D.ietf-sacm-terminology], a Broker is a 115 specific type of controller containing control plane functions; as 116 used here, the term refers to an XMPP publish-subscribe service. 118 Broker Flow: A method by which security-related information is 119 published and consumed in a mediated fashion through a Broker. In 120 this flow, the Broker handles authorization of Subscribers and 121 Publishers to Topics, receives messages from Publishers, and 122 delivers published messages to Subscribers. 124 Consumer: As defined in [I-D.ietf-sacm-terminology], a Consumer is a 125 component that contains functions to receive information from 126 other components; as used here, the term refers to an XMPP 127 publish-subscribe Subscriber. 129 Controller: As defined in [I-D.ietf-sacm-terminology], a controller 130 is a "component containing control plane functions that manage and 131 facilitate information sharing or execute on security functions"; 132 as used here, the term refers to either an XMPP server, which 133 provides both core message delivery [RFC6120] used by publish- 134 subscribe entities. 136 Node: The term used in the XMPP publish-subscribe specification 137 [XEP-0060] for a Topic. 139 Platform: Any entity that implements connects to the XMPP-Grid in 140 order to publisher or consume security-related data. 142 Provider: As defined in [I-D.ietf-sacm-terminology], a Provider is a 143 component that contains functions to provide information to other 144 components; as used here, the term refers to an XMPP publish- 145 subscribe Publisher. 147 Publisher: The term used in the XMPP publish-subscribe specification 148 [XEP-0060] for a Provider. 150 Publish-Subscribe Service: A Broker that implements the XMPP 151 publish-subscribe extension [XEP-0060]. 153 Subscriber: The term used in the XMPP publish-subscribe 154 specification [XEP-0060] for a Consumer. 156 Topic: A contextual information channel created on a Broker at which 157 messages generated by a Publisher will be propagated by XMPP in 158 real time to one or more Subscribers. Each Topic is limited to a 159 type and format of security data (e.g., IODEF) that a platform 160 wants to share with other platform(s) and a specified interface by 161 which the data can be obtained. 163 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 164 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 165 document are to be interpreted as described in [RFC2119]. 167 3. Architecture 169 The following figure illustrates the architecture of XMPP-Grid. 171 +--------------------------------------+ 172 | +--------------------------------------+ 173 | | +--------------------------------------+ 174 | | | | 175 +-| | Platforms | 176 +-| | 177 +--------------------------------------+ 178 / \ / \ / \ 179 / C \ / \ / \ 180 - o - - d - - - 181 ||n||A | a |B | |C 182 ||t|| | t | | | 183 - r - - a - | | 184 \ o / \ / | | 185 \ l / \ / | | 186 /|---------------------|\ | | 187 /|----/ \--------| d |--|\ 188 / / Controller \ ctrl | a | \ 189 \ \ & Broker / plane | t | / 190 \|----\ /--------| a |--|/ 191 \|---------------------|/ | | 192 / \ / \ | | 193 / C \ / \ | | 194 - o - - d - | | 195 ||n||A | a |B | |C 196 ||t|| | t | | | 197 - r - - a - - - 198 \ o / \ / \ / 199 \ l / \ / \ / 200 +------------------------------------+ 201 | |-+ 202 | Platforms | | 203 | | |-+ 204 +------------------------------------+ | | 205 +------------------------------------+ | 206 +------------------------------------+ 208 Figure 1: XMPP-Grid Architecture 210 Platforms connect to the Controller (XMPP server) to authenticate and 211 and then establish appropriate authorizations and relationships 212 (e.g., Publisher or Subscriber) at the Broker (XMPP publish-subscribe 213 service). The control plane messaging is established through XMPP 214 and shown as "A" (control plane interface) in Figure 1. Authorized 215 nodes may then share data either thru the Broker (shown as "B" in 216 Figure 1) or in some cases directly (shown as "C" in Figure 1). This 217 document focuses primarily on the Broker Flow for information sharing 218 (although "direct flow" interactions can be used for specialized 219 purposes such as bulk data transfer, methods for doing so are outside 220 the scope of this document). 222 4. Workflow 224 A typical XMPP-Grid workflow is as follows: 226 a. A Platform with a source of security data requests connection to 227 the XMPP-Grid via a Controller (XMPP server). 229 b. The Controller authenticates the Platform. 231 c. The Platform establishes authorized privileges (e.g. privilege to 232 publish and/or subscribe to security data Topics) with a Broker. 234 d. The Platform may publish security-related data to a Topic, 235 subscribe to a Topic, query a Topic, or any combination of these 236 operations. 238 e. A Publisher unicasts its Topic updates to the Grid in real time 239 through a Broker. The Broker handles replication and 240 distribution of the Topic to Subscribers. A Publisher may 241 publish the same or different data to multiple Topics. 243 f. Any Platform on the Grid may subscribe to any Topics published to 244 the Grid (as permitted by authorization policy), and (as 245 Subscribers) will then receive a continuous, real-time stream of 246 updates from the Topics to which they are subscribed. 248 5. Service Discovery 250 Using the XMPP service discovery extension [XEP-0030], a Controller 251 enables Platforms to discover what information may be consumed 252 through the Broker (publish-subscribe service). For instance, the 253 Controller might provide a Broker at 'broker.security-grid.example', 254 where 'security-grid.example' is the Controller host. Below is an 255 example for how a Platform can query for available information from 256 the XMPP-Controller: 258 262 263 265 The XMPP-Controller responds with the different types of information 266 it can publish: 268 272 274 277 280 281 283 6. IODEF Example 285 A Platform follows the standard XMPP workflow for connecting to the 286 Controller as well as using the XMPP discovery mechanisms to discover 287 the availability to consume IODEF information. The general workflow 288 is summarized in the figure below: 290 +----------------+ +----------------+ +----------------+ 291 | IODEF Client | | XMPP Server | | IODEF Service | 292 | (Subscriber) | | (Controller) | | (Publisher) | 293 +----------------+ +----------------+ +----------------+ 294 | | | 295 | IODEF Client | | 296 | Authentication | | 297 |<------------------------>| | 298 | | IODEF Service | 299 | | Authentication | 300 | |<----------------------->| 301 | | Create IODEF as a Topic | 302 | | (XEP-0060) | 303 | |<------------------------| 304 | | Topic Creation Success | 305 | |------------------------>| 306 | Topic Discovery | | 307 | (XEP-0030) | | 308 |------------------------->| | 309 | Discovery Response | | 310 | with Topics | | 311 |<-------------------------| | 312 | | | 313 | Subscribe to IODEF Topic | | 314 | (XEP-0060) | | 315 |------------------------->| | 316 | Subscription Success | | 317 |<-------------------------| | 318 | | IODEF Incident Publish | 319 | IODEF Incident Publish |<------------------------| 320 |<-------------------------| | 321 | | | 323 Figure 2: IODEF Example Workflow 325 An example XMPP discovery request for an IODEF 1.0 topic is shown 326 below: 328 332 333 335 An example XMPP discovery response for an IODEF 1.0 topic is shown 336 below: 338 342 343 346 347 349 7. IANA Considerations 351 This document has no actions for IANA. 353 8. Security Considerations 355 An XMPP-Grid Controller serves as an controlling broker for XMPP-Grid 356 Platforms such as Enforcement Points, Policy Servers, CMDBs, and 357 Sensors, using a publish-subscribe-search model of information 358 exchange and lookup. By increasing the ability of XMPP-Grid 359 Platforms to learn about and respond to security-relevant events and 360 data, XMPP-Grid can improve the timeliness and utility of the 361 security system. However, this integrated security system can also 362 be exploited by attackers if they can compromise it. Therefore, 363 strong security protections for XMPP-Grid are essential. 365 This section provides a security analysis of the XMPP-Grid transport 366 protocol and the architectural elements that employ it, specifically 367 with respect to their use of this protocol. Three subsections define 368 the trust model (which elements are trusted to do what), the threat 369 model (attacks that may be mounted on the system), and the 370 countermeasures (ways to address or mitigate the threats previously 371 identified). 373 8.1. Trust Model 375 The first step in analyzing the security of the XMPP-Grid transport 376 protocol is to describe the trust model, listing what each 377 architectural element is trusted to do. The items listed here are 378 assumptions, but provisions are made in the Threat Model and 379 Countermeasures sections for elements that fail to perform as they 380 were trusted to do. 382 8.1.1. Network 384 The network used to carry XMPP-Grid messages is trusted to: 386 o Perform best effort delivery of network traffic 388 The network used to carry XMPP-Grid messages is not expected 389 (trusted) to: 391 o Provide confidentiality or integrity protection for messages sent 392 over it 394 o Provide timely or reliable service 396 8.1.2. XMPP-Grid Platforms 398 Authorized XMPP-Grid Platforms are trusted to: 400 o Preserve the confidentiality of sensitive data retrieved via the 401 XMPP-Grid Controller 403 8.1.3. XMPP-Grid Controller 405 The XMPP-Grid Controller is trusted to: 407 o Broker requests for data and enforce authorization of access to 408 this data throughout its lifecycle 410 o Perform service requests in a timely and accurate manner 412 o Create and maintain accurate operational attributes 414 o Only reveal data to and accept service requests from authorized 415 parties 417 The XMPP-Grid Controller is not expected (trusted) to: 419 o Verify the truth (correctness) of data 421 8.1.4. Certification Authority 423 The Certification Authority (CA) that issues certificates for the 424 XMPP-Grid Controller and/or XMPP-Grid Platforms (or each CA, if there 425 are several) is trusted to: 427 o Ensure that only proper certificates are issued and that all 428 certificates are issued in accordance with the CA's policies 430 o Revoke certificates previously issued when necessary 432 o Regularly and securely distribute certificate revocation 433 information 435 o Promptly detect and report any violations of this trust so that 436 they can be handled 438 The CA is not expected (trusted) to: 440 o Issue certificates that go beyond the XMPP-Grid needs or other 441 constraints imposed by a relying party. 443 8.2. Threat Model 445 To secure the XMPP-Grid transport protocol and the architectural 446 elements that implement it, this section identifies the attacks that 447 can be mounted against the protocol and elements. 449 8.2.1. Network Attacks 451 A variety of attacks can be mounted using the network. For the 452 purposes of this subsection the phrase "network traffic" should be 453 taken to mean messages and/or parts of messages. Any of these 454 attacks may be mounted by network elements, by parties who control 455 network elements, and (in many cases) by parties who control network- 456 attached devices. 458 o Network traffic may be passively monitored to glean information 459 from any unencrypted traffic 461 o Even if all traffic is encrypted, valuable information can be 462 gained by traffic analysis (volume, timing, source and destination 463 addresses, etc.) 465 o Network traffic may be modified in transit 467 o Previously transmitted network traffic may be replayed 469 o New network traffic may be added 471 o Network traffic may be blocked, perhaps selectively 473 o A "Man In The Middle" (MITM) attack may be mounted where an 474 attacker interposes itself between two communicating parties and 475 poses as the other end to either party or impersonates the other 476 end to either or both parties 478 o Resist attacks (including denial of service and other attacks from 479 XMPP-Grid Platforms) 481 o Undesired network traffic may be sent in an effort to overload an 482 architectural component, thus mounting a denial of service attack 484 8.2.2. XMPP-Grid Platforms 486 An unauthorized XMPP-Grid Platforms (one which is not recognized by 487 the XMPP-Grid Controller or is recognized but not authorized to 488 perform any actions) cannot mount any attacks other than those listed 489 in the Network Attacks section above. 491 An authorized XMPP-Grid Platform, on the other hand, can mount many 492 attacks. These attacks might occur because the XMPP-Grid Platform is 493 controlled by a malicious, careless, or incompetent party (whether 494 because its owner is malicious, careless, or incompetent or because 495 the XMPP-Grid Platform has been compromised and is now controlled by 496 a party other than its owner). They might also occur because the 497 XMPP-Grid Platform is running malicious software; because the XMPP- 498 Grid Platform is running buggy software (which may fail in a state 499 that floods the network with traffic); or because the XMPP-Grid 500 Platform has been configured improperly. From a security standpoint, 501 it generally makes no difference why an attack is initiated. The 502 same countermeasures can be employed in any case. 504 Here is a list of attacks that may be mounted by an authorized XMPP- 505 Grid Platform: 507 o Cause many false alarms or otherwise overload the XMPP-Grid 508 Controller or other elements in the network security system 509 (including human administrators) leading to a denial of service or 510 disabling parts of the network security system 512 o Omit important actions (such as posting incriminating data), 513 resulting in incorrect access 515 o Use confidential information obtained from the XMPP-Grid 516 Controller to enable further attacks (such as using endpoint 517 health check results to exploit vulnerable endpoints) 519 o Advertise data crafted to exploit vulnerabilities in the XMPP-Grid 520 Controller or in other XMPP-Grid Platforms, with a goal of 521 compromising those systems 523 o Issue a search request or set up a subscription that matches an 524 enormous result, leading to resource exhaustion on the XMPP-Grid 525 Controller, the publishing XMPP-Grid Platform, and/or the network 527 o Establish a communication channel using another XMPP-Grid 528 Platform's session-id 530 Dependencies of or vulnerabilities of authorized XMPP-Grid Platforms 531 may be exploited to effect these attacks. Another way to effect 532 these attacks is to gain the ability to impersonate an XMPP-Grid 533 Platform (through theft of the XMPP-Grid Platform's identity 534 credentials or through other means). Even a clock skew between the 535 XMPP-Grid Platform and XMPP-Grid Controller can cause problems if the 536 XMPP-Grid Platform assumes that old XMPP-Grid Platform data should be 537 ignored. 539 8.2.3. XMPP-Grid Controllers 541 An unauthorized XMPP-Grid Controller (one which is not trusted by 542 XMPP-Grid Platforms) cannot mount any attacks other than those listed 543 in the Network Attacks section above. 545 An authorized XMPP-Grid Controller can mount many attacks. Similar 546 to the XMPP-Grid Platform case described above, these attacks might 547 occur because the XMPP-Grid Controller is controlled by a malicious, 548 careless, or incompetent party (either an XMPP-Grid Controller 549 administrator or an attacker who has seized control of the XMPP-Grid 550 Controller). They might also occur because the XMPP-Grid Controller 551 is running malicious software, because the XMPP-Grid Controller is 552 running buggy software (which may fail in a state that corrupts data 553 or floods the network with traffic), or because the XMPP-Grid 554 Controller has been configured improperly. 556 All of the attacks listed for XMPP-Grid Platform above can be mounted 557 by the XMPP-Grid Controller. Detection of these attacks will be more 558 difficult since the XMPP-Grid Controller can create false operational 559 attributes and/or logs that imply some other party created any bad 560 data. 562 Additional XMPP-Grid Controller attacks may include: 564 o Expose different data to different XMPP-Grid Platforms to mislead 565 investigators or cause inconsistent behavior 567 o Mount an even more effective denial of service attack than a 568 single XMPP-Grid Platform could 570 o Obtain and cache XMPP-Grid Platform credentials so they can be 571 used to impersonate XMPP-Grid Platforms even after a breach of the 572 XMPP-Grid Controller is repaired 574 o Obtain and cache XMPP-Grid Controller administrator credentials so 575 they can be used to regain control of the XMPP-Grid Controller 576 after the breach of the XMPP-Grid Controller is repaired 578 Dependencies of or vulnerabilities of the XMPP-Grid Controller may be 579 exploited to obtain control of the XMPP-Grid Controller and effect 580 these attacks. 582 8.2.4. Certification Authority 584 A Certification Authority trusted to issue certificates for the XMPP- 585 Grid Controller and/or XMPP-Grid Platforms can mount several attacks: 587 o Issue certificates for unauthorized parties, enabling them to 588 impersonate authorized parties such as the XMPP-Grid Controller or 589 an XMPP-Grid Platform. This can lead to all the threats that can 590 be mounted by the certificate's subject. 592 o Issue certificates without following all of the CA's policies. 593 Because this can result in issuing certificates that may be used 594 to impersonate authorized parties, this can lead to all the 595 threats that can be mounted by the certificate's subject. 597 o Fail to revoke previously issued certificates that need to be 598 revoked. This can lead to undetected impersonation of the 599 certificate's subject or failure to revoke authorization of the 600 subject, and therefore can lead to all of the threats that can be 601 mounted by that subject. 603 o Fail to regularly and securely distribute certificate revocation 604 information. This may cause a relying party to accept a revoked 605 certificate, leading to undetected impersonation of the 606 certificate's subject or failure to revoke authorization of the 607 subject, and therefore can lead to all of the threats that can be 608 mounted by that subject. It can also cause a relying party to 609 refuse to proceed with a transaction because timely revocation 610 information is not available, even though the transaction should 611 be permitted to proceed. 613 o Allow the CA's private key to be revealed to an unauthorized 614 party. This can lead to all the threats above. Even worse, the 615 actions taken with the private key will not be known to the CA. 617 o Fail to promptly detect and report errors and violations of trust 618 so that relying parties can be promptly notified. This can cause 619 the threats listed earlier in this section to persist longer than 620 necessary, leading to many knock-on effects. 622 8.3. Countermeasures 624 Below are countermeasures for specific attack scenarios to the XMPP- 625 Grid infrastructure. 627 8.3.1. Securing the XMPP-Grid Transport Protocol 629 To address network attacks, the XMPP-Grid transport protocol 630 described in this document requires that the XMPP-Grid messages MUST 631 be carried over TLS (minimally TLS 1.2 [RFC5246]) as described in 632 [RFC6120] and updated by [RFC7590]. The XMPP-Grid Platform MUST 633 verify the XMPP-Grid Controller's certificate and determine whether 634 the XMPP-Grid Controller is trusted by this XMPP-Grid Platform before 635 completing the TLS handshake. The XMPP-Grid Controller MUST 636 authenticate the XMPP-Grid Platform either using mutual certificate- 637 based authentication in the TLS handshake or using Basic 638 Authentication as described in IETF RFC 2617. XMPP-Grid Controller 639 MUST use Simple Authentication and Security Layer (SASL), described 640 in [RFC4422], to support the aforesaid authentication mechanisms. 641 SASL offers authentication mechanism negotiations between the XMPP- 642 Grid Controller and XMPP-Grid node during the connection 643 establishment phase. XMPP-Grid Platforms and XMPP-Grid Controllers 644 using mutual certificate-based authentication SHOULD each verify the 645 revocation status of the other party's certificate. All XMPP-Grid 646 Controllers and XMPP-Grid Platforms MUST implement both mutual 647 certificate-based authentication and Basic Authentication. The 648 selection of which XMPP-Grid Platform authentication technique to use 649 in any particular deployment is left to the administrator. 651 An XMPP-Grid Controller MAY also support a local, configurable set of 652 Basic Authentication userid-password pairs. If so, it is 653 implementation dependent whether an XMPP-Grid Controller ends a 654 session when an administrator changes the configured password. Since 655 Basic Authentication has many security disadvantages (especially the 656 transmission of reusable XMPP-Grid Platform passwords to the XMPP- 657 Grid Controller), it SHOULD only be used when absolutely necessary. 658 Per the HTTP specification, when basic authentication is in use, an 659 XMPP-Grid Controller MAY respond to any request that lacks 660 credentials with an error code similar to HTTP code 401. An XMPP- 661 Grid Platform SHOULD avoid this code by submitting basic auth 662 credentials with every request when basic authentication is in use. 663 If it does not do so, an XMPP-Grid Platform MUST respond to this code 664 by resubmitting the same request with credentials (unless the XMPP- 665 Grid Platform is shutting down). 667 Best practices for the use of TLS in XMPP are defined in [RFC7590]. 669 These protocol security measures provide protection against all the 670 network attacks listed in the above document section except denial of 671 service attacks. If protection against these denial of service 672 attacks is desired, ingress filtering, rate limiting per source IP 673 address, and other denial of service mitigation measures may be 674 employed. In addition, an XMPP-Grid Controller MAY automatically 675 disable a misbehaving XMPP-Grid Platform. 677 8.3.2. Securing XMPP-Grid Platforms 679 XMPP-Grid Platforms may be deployed in locations that are susceptible 680 to physical attacks. Physical security measures may be taken to 681 avoid compromise of XMPP-Grid Platforms, but these may not always be 682 practical or completely effective. An alternative measure is to 683 configure the XMPP-Grid Controller to provide read-only access for 684 such systems. The XMPP-Grid Controller SHOULD also include a full 685 authorization model so that individual XMPP-Grid Platforms may be 686 configured to have only the privileges that they need. The XMPP-Grid 687 Controller MAY provide functional templates so that the administrator 688 can configure a specific XMPP-Grid Platform as a DHCP server and 689 authorize only the operations and metadata types needed by a DHCP 690 server to be permitted for that XMPP-Grid Platform. These techniques 691 can reduce the negative impacts of a compromised XMPP-Grid Platform 692 without diminishing the utility of the overall system. 694 To handle attacks within the bounds of this authorization model, the 695 XMPP-Grid Controller MAY also include rate limits and alerts for 696 unusual XMPP-Grid Platform behavior. XMPP-Grid Controllers SHOULD 697 make it easy to revoke an XMPP-Grid Platform's authorization when 698 necessary. Another way to detect attacks from XMPP-Grid Platforms is 699 to create fake entries in the available data (honeytokens) which 700 normal XMPP-Grid Platforms will not attempt to access. The XMPP-Grid 701 Controller SHOULD include auditable logs of XMPP-Grid Platform 702 activities. 704 To avoid compromise of XMPP-Grid Platform, XMPP-Grid Platform SHOULD 705 be hardened against attack and minimized to reduce their attack 706 surface. They should be well managed to minimize vulnerabilities in 707 the underlying platform and in systems upon which the XMPP-Grid 708 Platform depends. Personnel with administrative access should be 709 carefully screened and monitored to detect problems as soon as 710 possible. 712 8.3.3. Securing XMPP-Grid Controllers 714 Because of the serious consequences of XMPP-Grid Controller 715 compromise, XMPP-Grid Controllers SHOULD be especially well hardened 716 against attack and minimized to reduce their attack surface. They 717 should be well managed to minimize vulnerabilities in the underlying 718 platform and in systems upon which the XMPP-Grid Controller depends. 719 Network security measures such as firewalls or intrusion detection 720 systems may be used to monitor and limit traffic to and from the 721 XMPP-Grid Controller. Personnel with administrative access should be 722 carefully screened and monitored to detect problems as soon as 723 possible. Administrators should not use password-based 724 authentication but should instead use non-reusable credentials and 725 multi-factor authentication (where available). Physical security 726 measures SHOULD be employed to prevent physical attacks on XMPP-Grid 727 Controllers. 729 To ease detection of XMPP-Grid Controller compromise should it occur, 730 XMPP-Grid Controller behavior should be monitored to detect unusual 731 behavior (such as a reboot, a large increase in traffic, or different 732 views of an information repository for similar XMPP-Grid Platforms). 733 XMPP-Grid Platforms should log and/or notify administrators when 734 peculiar XMPP-Grid Controller behavior is detected. To aid forensic 735 investigation, permanent read-only audit logs of security-relevant 736 information (especially administrative actions) should be maintained. 737 If XMPP-Grid Controller compromise is detected, a careful analysis 738 should be performed of the impact of this compromise. Any reusable 739 credentials that may have been compromised should be reissued. 741 8.3.4. Limit on search result size 743 While XMPP-Grid is designed for high scalability to 100,000s of 744 Platforms, an XMPP-Grid Controller MAY establish a limit to the 745 amount of data it is willing to return in search or subscription 746 results. This mitigates the threat of an XMPP-Grid Platform causing 747 resource exhaustion by issuing a search or subscription that leads to 748 an enormous result. 750 8.3.5. Cryptographically random session-id and authentication checks 751 for ARC 753 An XMPP-Grid Controller SHOULD ensure that the XMPP-Grid Platform 754 establishing an Authenticated Results Chain (ARC) is the same XMPP- 755 Grid Platform as the XMPP-Grid Platform that established the 756 corresponding Synchronization Source Identifier (SSRC). The XMPP- 757 Grid Controller SHOULD employ both of the following strategies: 759 o session-ids SHOULD be cryptographically random 761 o The HTTPS transport for the SSRC and the ARC SHOULD be 762 authenticated using the same credentials. SSL session resumption 763 MAY be used to establish the ARC based on the SSRC SSL session. 765 8.3.6. Securing the Certification Authority 767 As noted above, compromise of a Certification Authority (CA) trusted 768 to issue certificates for the XMPP-Grid Controller and/or XMPP-Grid 769 Platforms is a major security breach. Many guidelines for proper CA 770 security have been developed: the CA/Browser Forum's Baseline 771 Requirements, the AICPA/CICA Trust Service Principles, etc. The CA 772 operator and relying parties should agree on an appropriately 773 rigorous security practices to be used. 775 Even with the most rigorous security practices, a CA may be 776 compromised. If this compromise is detected quickly, relying parties 777 can remove the CA from their list of trusted CAs, and other CAs can 778 revoke any certificates issued to the CA. However, CA compromise may 779 go undetected for some time, and there's always the possibility that 780 a CA is being operated improperly or in a manner that is not in the 781 interests of the relying parties. For this reason, relying parties 782 may wish to "pin" a small number of particularly critical 783 certificates (such as the certificate for the XMPP-Grid Controller). 784 Once a certificate has been pinned, the relying party will not accept 785 another certificate in its place unless the Administrator explicitly 786 commands it to do so. This does not mean that the relying party will 787 not check the revocation status of pinned certificates. However, the 788 Administrator may still be consulted if a pinned certificate is 789 revoked, since the CA and revocation process are not completely 790 trusted. 792 8.4. Summary 794 XMPP-Grid's considerable value as a broker for security-sensitive 795 data exchange distribution also makes the protocol and the network 796 security elements that implement it a target for attack. Therefore, 797 strong security has been included as a basic design principle within 798 the XMPP-Grid design process. 800 The XMPP-Grid transport protocol provides strong protection against a 801 variety of different attacks. In the event that an XMPP-Grid 802 Platform or XMPP-Grid Controller is compromised, the effects of this 803 compromise have been reduced and limited with the recommended role- 804 based authorization model and other provisions, and best practices 805 for managing and protecting XMPP-Grid systems have been described. 806 Taken together, these measures should provide protection commensurate 807 with the threat to XMPP-Grid systems, thus ensuring that they fulfill 808 their promise as a network security clearing-house. 810 9. Privacy Considerations 812 XMPP-Grid Platforms may publish information about endpoint health, 813 network access, events (which may include information about what 814 services an endpoint is accessing), roles and capabilities, and the 815 identity of the end user operating the endpoint. Any of this 816 published information may be queried by other XMPP-Grid Platforms and 817 could potentially be used to correlate network activity to a 818 particular end user. 820 Dynamic and static information brokered by an XMPP-Grid Controller, 821 ostensibly for purposes of correlation by XMPP-Grid Platforms for 822 intrusion detection, could be misused by a broader set of XMPP-Grid 823 Platforms which hitherto have been performing specific roles with 824 strict well-defined separation of duties. 826 Care should be taken by deployers of XMPP-Grid to ensure that the 827 information published by XMPP-Grid Platforms does not violate 828 agreements with end users or local and regional laws and regulations. 829 This can be accomplished either by configuring XMPP-Grid Platforms to 830 not publish certain information or by restricting access to sensitive 831 data to trusted XMPP-Grid Platforms. That is, the easiest means to 832 ensure privacy or protect sensitive data, is to omit or not share it 833 at all. 835 Another consideration for deployers is to enable end-to-end 836 encryption to ensure the data is protected from the data layer to 837 data layer and thus protect it from the transport layer. 839 10. Acknowledgements 841 The authors would like to acknowledge the contributions, authoring 842 and/or editing of the following people: Joseph Salowey, Lisa 843 Lorenzin, Clifford Kahn, Henk Birkholz, Jessica Fitzgerald-McKay, 844 Steve Hanna, and Steve Venema. In addition, we want to thank Takeshi 845 Takahashi, Panos Kampanakis, Adam Montville, Chris Inacio, and Dave 846 Cridland for reviewing and providing valuable comments. 848 11. References 850 11.1. Normative References 852 [I-D.ietf-sacm-terminology] 853 Birkholz, H., Lu, J., Strassner, J., and N. Cam-Winget, 854 "Secure Automation and Continuous Monitoring (SACM) 855 Terminology", draft-ietf-sacm-terminology-13 (work in 856 progress), July 2017. 858 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 859 Requirement Levels", BCP 14, RFC 2119, 860 DOI 10.17487/RFC2119, March 1997, . 863 [RFC4422] Melnikov, A., Ed. and K. Zeilenga, Ed., "Simple 864 Authentication and Security Layer (SASL)", RFC 4422, 865 DOI 10.17487/RFC4422, June 2006, . 868 [RFC6120] Saint-Andre, P., "Extensible Messaging and Presence 869 Protocol (XMPP): Core", RFC 6120, DOI 10.17487/RFC6120, 870 March 2011, . 872 [RFC7590] Saint-Andre, P. and T. Alkemade, "Use of Transport Layer 873 Security (TLS) in the Extensible Messaging and Presence 874 Protocol (XMPP)", RFC 7590, DOI 10.17487/RFC7590, June 875 2015, . 877 [XEP-0030] 878 Hildebrand, J., Millard, P., Eatmon, R., and P. Saint- 879 Andre, "Service Discovery", XSF XEP 0030, July 2010. 881 [XEP-0060] 882 Millard, P. and P. Saint-Andre, "Publish-Subscribe", 883 XSF XEP 0060, December 2016. 885 11.2. Informative References 887 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 888 (TLS) Protocol Version 1.2", RFC 5246, 889 DOI 10.17487/RFC5246, August 2008, . 892 [RFC7970] Danyliw, R., "The Incident Object Description Exchange 893 Format Version 2", RFC 7970, DOI 10.17487/RFC7970, 894 November 2016, . 896 Authors' Addresses 898 Nancy Cam-Winget (editor) 899 Cisco Systems 900 3550 Cisco Way 901 San Jose, CA 95134 902 USA 904 Email: ncamwing@cisco.com 905 Syam Appala 906 Cisco Systems 907 3550 Cisco Way 908 San Jose, CA 95134 909 USA 911 Email: syam1@cisco.com 913 Scott Pope 914 Cisco Systems 915 5400 Meadows Road 916 Suite 300 917 Lake Oswego, OR 97035 918 USA 920 Email: scottp@cisco.com 922 Peter Saint-Andre 923 Jabber.org 924 P.O. Box 787 925 Parker, CO 80134 926 USA 928 Email: stpeter@jabber.org