idnits 2.17.1 draft-ietf-sieve-external-lists-10.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (June 9, 2011) is 4698 days in the past. Is this intentional? -- Found something which looks like a code comment -- if you have code sections in the document, please surround them with '' and '' lines. Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Downref: Normative reference to an Informational RFC: RFC 4151 ** Obsolete normative reference: RFC 5226 (Obsoleted by RFC 8126) Summary: 2 errors (**), 0 flaws (~~), 1 warning (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Sieve Working Group A. Melnikov 3 Internet-Draft Isode Limited 4 Intended status: Standards Track B. Leiba 5 Expires: December 11, 2011 Huawei Technologies 6 June 9, 2011 8 Sieve Extension: Externally Stored Lists 9 draft-ietf-sieve-external-lists-10 11 Abstract 13 The Sieve email filtering language can be used to implement email 14 whitelisting, blacklisting, personal distribution lists, and other 15 sorts of list matching. Currently, this requires that all members of 16 such lists be hardcoded in the script itself. Whenever a member of a 17 list is added or deleted, the script needs to be updated and possibly 18 uploaded to a mail server. 20 This document defines a Sieve extension for accessing externally 21 stored lists -- lists whose members are stored externally to the 22 script, such as using LDAP (RFC 4510), ACAP (RFC 2244), CardDAV (work 23 in progress), or relational databases. 25 Status of this Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at http://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on December 11, 2011. 42 Copyright Notice 44 Copyright (c) 2011 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (http://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 3 60 1.1. Conventions Used In This Document . . . . . . . . . . . . 3 62 2. Extlists Extension . . . . . . . . . . . . . . . . . . . . 3 63 2.1. Capability Identifier . . . . . . . . . . . . . . . . . . 3 64 2.2. :list Match Type for Supported Tests . . . . . . . . . . . 3 65 2.3. :list Tagged Argument to the "redirect" Action . . . . . . 4 66 2.4. Other Uses for External Lists . . . . . . . . . . . . . . 5 67 2.5. Syntax of an Externally Stored List Name . . . . . . . . . 5 68 2.6. Definition of "addrbook" URN Parameter . . . . . . . . . . 7 69 2.7. Test valid_ext_list . . . . . . . . . . . . . . . . . . . 9 70 2.8. Interaction with ManageSieve . . . . . . . . . . . . . . . 9 71 2.9. Examples . . . . . . . . . . . . . . . . . . . . . . . . . 9 72 2.9.1. Example 1 . . . . . . . . . . . . . . . . . . . . . . . . 9 73 2.9.2. Example 2 . . . . . . . . . . . . . . . . . . . . . . . . 10 74 2.9.3. Example 3 . . . . . . . . . . . . . . . . . . . . . . . . 10 75 2.9.4. Example 4 . . . . . . . . . . . . . . . . . . . . . . . . 11 76 2.9.5. Example 5 . . . . . . . . . . . . . . . . . . . . . . . . 11 78 3. Security Considerations . . . . . . . . . . . . . . . . . 12 80 4. IANA Considerations . . . . . . . . . . . . . . . . . . . 14 81 4.1. Registration of Sieve Extension . . . . . . . . . . . . . 14 82 4.2. Registration of ManageSieve Capability . . . . . . . . . . 14 83 4.3. Creation of Sieve URN Parameters registry . . . . . . . . 15 84 4.4. Registration of the "addrbook" URN parameter . . . . . . . 16 85 4.5. Registration of "sieve" URN sub-namespace . . . . . . . . 16 87 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . 16 89 6. References . . . . . . . . . . . . . . . . . . . . . . . . 16 90 6.1. Normative References . . . . . . . . . . . . . . . . . . . 16 91 6.2. Informative References . . . . . . . . . . . . . . . . . . 17 93 Authors' Addresses . . . . . . . . . . . . . . . . . . . . 18 95 1. Introduction 97 This document specifies an extension to the Sieve language [RFC5228] 98 for checking membership in an external list or for redirecting 99 messages to an external list of recipients. An "external list" is a 100 list whose members are stored externally to the Sieve script, such as 101 using LDAP [RFC4510], ACAP [RFC2244], CardDAV 102 [I-D.ietf-vcarddav-carddav], or relational databases. 104 This extension adds a new match type to apply to supported tests, and 105 a new tagged argument to the "redirect" action. 107 1.1. Conventions Used In This Document 109 Conventions for notations are as in [RFC5228] section 1.1, including 110 the use of ABNF [RFC5234]. 112 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 113 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 114 document are to be interpreted as described in [RFC2119]. 116 2. Extlists Extension 118 2.1. Capability Identifier 120 The capability string associated with the extension defined in this 121 document is "extlists". 123 2.2. :list Match Type for Supported Tests 125 ABNF: 127 MATCH-TYPE =/ ":list" 128 ; only valid for supported tests 130 The new ":list" match type changes the interpretation of the "key- 131 list" parameter (the second parameter) in supported tests. When the 132 match type is ":list", the key-list becomes a list of names of 133 externally stored lists. The external lists are queried, perhaps 134 through a list-specific mechanism, and the test evaluates to "true" 135 if any of the specified values matches any member of one or more of 136 the lists. 138 Comparators are not allowed together with the ":list" match type, so 139 if both are specified in a test, that MUST result in an error. 140 Queries done through list-specific mechanisms might have the effect 141 of built-in comparators; for example, queries to certain lists might 142 be case-sensitive, while queries to other lists might be done without 143 regard to case. 145 Implementations MUST support the use of ":list" in "address", 146 "envelope" and "header" tests. Implementations that include the 147 Variables extension [RFC5229] MUST also support its use in "string" 148 tests. 150 Implementations MAY support other tests than the ones in this 151 document. Implementations MUST report an error when a script uses 152 ":list" with a test that does not support ":list". This error SHOULD 153 be reported at compile-time, but MAY be reported at run-time. To 154 maintain interoperability, other tests that can be used with ":list" 155 SHOULD be documented in a specification that defines a capability 156 string that can be tested (in a "require" statement or using ihave 157 [RFC5463]). 159 For example, testing 'header ["to", "cc"]' against a list would cause 160 each "to" and "cc" value, ignoring leading and trailing whitespace, 161 to be queried. If any value is found to belong to the list, the test 162 returns "true". If no value belongs to the list, the test returns 163 "false". Once a value is found in the list, there is no need for the 164 query mechanism to look further. 166 For some lists, the Sieve engine might directly retrieve the list and 167 make its own comparison. Other lists might not work that way -- they 168 might provide a way to ask if a value is in the list, but not permit 169 retrieval of the list itself. It is up to the Sieve implementation 170 to understand how to interact with any supported list. If the Sieve 171 engine is permanently unable to query the list (perhaps because the 172 list doesn't support the required operation), the test MUST result in 173 a runtime error in the Sieve script. 175 See Section 2.5 for the detailed description of syntax used for 176 naming externally stored lists. 178 The ":list" match type uses the concept of "match variables" as 179 defined in Section 3.2 of the Variables extension [RFC5229]. 180 Implementations that also support that extension MUST set the ${0} 181 match variable to the value in the list that matched the query. 182 Other numbered match variables (${1}, ${2}, and so on) MAY be set 183 with list-specific information that might be of use to the script. 185 2.3. :list Tagged Argument to the "redirect" Action 186 Usage: redirect :list 188 The "redirect" action with the ":list" argument is used to send the 189 message to the set of email addresses in the externally stored list 190 named by the ext-list-name string. This variant of the redirect 191 command can be used to implement a personal distribution list. 193 For this feature to work, one of the following conditions has to be 194 true: 196 1. The list resolves to a list of email addresses, and the Sieve 197 engine is able to enumerate those addresses. 199 2. The list handler is able to take care of the redirection on 200 behalf of the Sieve engine. 202 In cases where, for example, a list contains hashed email address 203 values or an email address pattern ("sz*@example.com", 204 "*+ietf@example.net"), the Sieve engine will not be able to redirect 205 to that list, and responsibility must pass to the list handler. 207 If neither the Sieve engine nor the list handler can enumerate (or 208 iterate) the list, or the list does not resolve to email addresses, 209 the situation MUST result in a runtime error in the Sieve script. 211 See Section 2.5 for the detailed description of syntax used for 212 naming externally stored lists. 214 2.4. Other Uses for External Lists 216 The uses for external lists specified here represent the useful cases 217 and situations at the time of this writing. Other uses for external 218 lists, using other Sieve features, might be devised in the future, 219 and such uses can be described in extensions to this document. 221 2.5. Syntax of an Externally Stored List Name 223 A name of an externally stored list is always an absolute URI 224 [RFC3986]. Implementations might find URIs such as LDAP [RFC4510], 225 CardDAV [I-D.ietf-vcarddav-carddav], or Tag [RFC4151] to be useful 226 for naming external lists. 228 The "tag" URI scheme [RFC4151] can be used to represent opaque, but 229 user friendlier identifiers. Resolution of such identifiers is going 230 to be implementation specific and it can help in hiding the 231 complexity of an implementation from end users. For example, an 232 implementation can provide a web interface for managing lists of 233 users stored in LDAP. Requiring users to know generic LDAP URI 234 syntax might not be very practical, due to its complexity. An 235 implementation can instead use a fixed tag URI prefix such as "tag: 236 example.com,:" (where can be, for example, a date 237 generated once on installation of the web interface and left 238 untouched upon upgrades) and the prefix doesn't even need to be shown 239 to end users. 241 The "addrbook" URNs defined in Section 2.6 (in particular, the 242 reserved URI "urn:ietf:params:sieve:addrbook:default") MUST be 243 supported. To make it easier to use registered Sieve URN parameters, 244 we define a shorthand way to specify them in a Sieve script: a list 245 name that begins with ":" is taken as referencing a Sieve URN 246 parameter, with the initial ":" expanding to 247 "urn:ietf:params:sieve:". So we have the following equivalences: 249 :addrbook:default == urn:ietf:params:sieve:addrbook:default 251 :addrbook:personal == urn:ietf:params:sieve:addrbook:personal 253 ...and so on. 255 The mandatory-to-implement URI 257 urn:ietf:params:sieve:addrbook:default 259 gives access to the user's default address book (usually the user's 260 personal address book). Note that these are URIs, subject to normal 261 URI encoding rules, including percent-encoding. The reserved name 262 "default" MUST be considered case-insensitive after decoding. That 263 means that the following URIs are all equivalent: 265 :addrbook:default 267 :ADDRBOOK:DEFAULT 269 :aDdRbOOk:DeFauLt 271 :AddrBook:%44%65%66ault 273 Address book names other than "default" MAY be case-sensitive, 274 depending upon the implementation, so their case (after URI decoding) 275 MUST be maintained. 277 It's possible that a server will have no access to anything 278 resembling an address book (perhaps in an implementation where 279 address books are only client-side things), but the server can still 280 provide access to other sorts of lists -- consider the list of dates 281 in Example 2 (Section 2.9.2), or lists of important keywords and the 282 like. It might sometimes make sense to map ":addrbook:default" into 283 some available list, but that might not always be reasonable. If 284 there really is no concept of an address book in a particular server 285 implementation, the server MAY support ":addrbook:default" by having 286 all matches to it fail. Such an implementation SHOULD NOT be done 287 except as a last resort. 289 Queries against address books SHOULD be done without regard to case. 291 2.6. Definition of "addrbook" URN Parameter 293 This section gives the details of the "addrbook" Sieve URN parameter 294 that's registered in Section 4.4. URIs that use this parameter begin 295 with "urn:ietf:params:sieve:addrbook:". 297 URN parameter name: addrbook 299 URN parameter syntax: The "addrbook" parameter is defined by the 300 rule, defined using ABNF [RFC5234]: 302 addrbook-urn = "addrbook:" addrbook [ "?" extensions ] 303 addrbook = segment 304 ; defined in [RFC3986] 305 extensions = query 306 ; defined in [RFC3986] 308 Intended usage: "addrbook" URNs are used for designating references 309 to address books. An address book is a concept used by different 310 applications (such as Sieve interpreters) for describing a list 311 of named entries, and may be translated into other types of 312 address books, such as LDAP Groups. Address books may be private 313 or shared; they may be personal, organizational, or perhaps even 314 "crowdsourced". 316 The address book name (the "addrbook" element in the ABNF above) 317 refers to a specifically named address book, as defined by the 318 implementation. A user might, for example, have access to a 319 number of different address books, such as a personal one, a 320 family one, a company one, and one for the town where the user 321 lives. 323 The extension information (the "extensions" element in the ABNF 324 above) is available for use in future extensions. It might allow 325 for things such as dynamic subsets of an address book -- for 326 example, something such as this might be defined in the future: 328 urn:ietf:params:sieve:addrbook:personal?name.contains=fred 330 There are no extensions defined at this time. 332 An "addrbook" URN is designed to be used by applications for 333 referencing address books. Each URN is intended to represent a 334 grouping of addresses that can be logically thought of as one 335 "book". Any given address can belong to more than one book -- 336 that is, can be referred to by more than one URN. 338 The URI "urn:ietf:params:sieve:addrbook" has no meaning in 339 itself. It MUST be used with sub-parameters representing the 340 address book name and extension information, as shown in the ABNF 341 above. 343 The sub-parameter "default" (creating the URN 344 "urn:ietf:params:sieve:addrbook:default") is a reserved (case- 345 insensitive) name that MUST be implemented, representing a 346 default grouping (book) of addresses. Other names, representing 347 the same or other groupings MAY be implemented. For example, an 348 implementation might use the following sub-parameters: 350 * personal -- a book representing the user's personal address 351 book. 353 * friends -- a subset of 354 urn:ietf:params:sieve:addrbook:personal, defined by the user. 356 * family -- a subset of 357 urn:ietf:params:sieve:addrbook:personal, defined by the user. 359 * company -- a book representing user's company's address book. 361 * department -- a subset of 362 urn:ietf:params:sieve:addrbook:company, defined by the 363 company. 365 * co-workers -- a subset of 366 urn:ietf:params:sieve:addrbook:company, defined by the user. 368 * default -- the default address book, a reference to 369 urn:ietf:params:sieve:addrbook:personal. 371 Interoperability considerations: Applications are only REQUIRED to 372 support "addrbook:default", where all cases and encodings of 373 "default" are considered equivalent. Address book names other 374 than "default" MAY be case-sensitive, depending upon the 375 implementation, so their case (after URI decoding) MUST be 376 maintained. 378 Security considerations: Applications SHOULD ensure appropriate 379 restrictions are in place to protect sensitive information that 380 might be revealed by "addrbook" URNs from access or modification 381 by untrusted sources. 383 Contact: Sieve mailing list 385 2.7. Test valid_ext_list 387 Usage: valid_ext_list 389 The "valid_ext_list" test is true if all of the external list names 390 in the ext-list-names argument are supported, and they are valid both 391 syntactically (including URI parameters) and semantically (including 392 implementation-specific semantic restrictions). Otherwise the test 393 returns false. 395 This test MUST perform exactly the same validation of an external 396 list name as would be performed by the "header :list" test. 398 2.8. Interaction with ManageSieve 400 This extension defines the following new capability for ManageSieve 401 (see [RFC5804] section 1.7): 403 EXTLISTS - A space-separated list of URI schema parts [RFC3986] for 404 supported externally stored list types. This capability MUST be 405 returned if the corresponding Sieve implementation supports the 406 "extlists" extension defined in this document. 408 This also extends the ManageSieve ABNF as follows: 410 single-capability =/ DQUOTE "EXTLISTS" DQUOTE SP ext-list-types CRLF 411 ; single-capability is defined in [RFC5804] 413 ext-list-types = string 414 ; space separated list of URI schema parts 415 ; for supported externally stored list types. 416 ; MUST NOT be empty. 418 2.9. Examples 420 2.9.1. Example 1 422 This example uses a personal address book, along with the Spamtest 423 [RFC5235] and Relational [RFC5231] extensions to give a different 424 level of spam tolerance to known senders. 426 require ["envelope", "extlists", "fileinto", "spamtest", 427 "relational", "comparator-i;ascii-numeric"]; 428 if envelope :list "from" ":addrbook:default" 429 { /* Known: allow high spam score */ 430 if spamtest :value "ge" :comparator "i;ascii-numeric" "8" 431 { 432 fileinto "spam"; 433 } 434 } 435 elsif spamtest :value "ge" :comparator "i;ascii-numeric" "3" 436 { /* Unknown: less tolerance in spam score */ 437 fileinto "spam"; 438 } 440 The same example can also be written another way, if the Variables 441 extension [RFC5229] is also supported: 443 require ["envelope", "extlists", "fileinto", "spamtest", 444 "variables", "relational", "comparator-i;ascii-numeric"]; 445 if envelope :list "from" ":addrbook:default" { 446 set "lim" "8"; /* Known: allow high spam score */ 447 } else { 448 set "lim" "3"; /* Unknown: less tolerance in spam score */ 449 } 450 if spamtest :value "ge" :comparator "i;ascii-numeric" "${lim}" { 451 fileinto "spam"; 452 } 454 2.9.2. Example 2 456 This example uses the "currentdate" test [RFC5260] and a list 457 containing the dates of local holidays. If today is a holiday, the 458 script will notify [RFC5435] the user via XMPP [RFC5437] about the 459 message. 461 require ["extlists", "date", "enotify"]; 462 if currentdate :list "date" 463 "tag:example.com,2011-01-01:localHolidays" { 464 notify "xmpp:romeo@im.example.com"; 465 } 467 2.9.3. Example 3 469 This example also uses the "envelope" option [RFC5228] and the 470 Subaddress extension [RFC5233]. If mail is sent with the list name 471 as a subaddress of the recipient (to, say, "alexey+mylist"), and the 472 message comes from a member of the list, it will be redirected to all 473 members of the list. Variants of this technique might be useful for 474 creating private mailing lists. 476 require ["extlists", "envelope", "subaddress"]; 478 # Submission from list members is sent to all members 479 if allof (envelope :detail "to" "mylist", 480 header :list "from" 481 "tag:example.com,2010-05-28:mylist") { 482 redirect :list "tag:example.com,2010-05-28:mylist"; 483 } 485 2.9.4. Example 4 487 This example uses variable matching [RFC5229] to extract the IP 488 address from the last "Received" header field. It then checks that 489 against a "block list" of undesirable IP addresses, and rejects the 490 message if there's a match. 492 require ["variables", "extlists", "index", "reject"]; 493 if header :index 1 :matches "received" "*(* [*.*.*.*])*" { 494 set "ip" "${3}.${4}.${5}.${6}"; 495 if string :list "${ip}" 496 "tag:example.com,2011-04-10:DisallowedIPs" { 497 reject "Message not allowed from this IP address"; 498 } 499 } 501 2.9.5. Example 5 503 This example uses several features of the MIME parts extension 504 [RFC5703] to scan for unsafe attachment types. To make it easily 505 extensible, the unsafe types are kept in an external list, which 506 would be shared among all users and all scripts, avoiding the need to 507 change scripts when the list changes. 509 [Note that this is an illustrative example, and more rigorous malware 510 filtering is advisable. It is insufficient to base email security on 511 checks of filenames alone.] 512 require [ "extlists", "foreverypart", "mime", "enclose" ]; 514 foreverypart 515 { 516 if header :mime :param "filename" 517 :list ["Content-Type", "Content-Disposition"] 518 "tag:example.com,2011-04-10:BadFileNameExts" 519 { 520 # these attachment types are executable 521 enclose :subject "Warning" :text 522 WARNING! The enclosed message attachments that might be unsafe. 523 These attachment types may contain a computer virus program 524 that can infect your computer and potentially damage your data. 526 Before clicking on these message attachments, you should verify 527 with the sender that this message was sent intentionally, and 528 that the attachments are safe to open. 529 . 530 ; 531 break; 532 } 533 } 535 3. Security Considerations 537 Security considerations related to the "address"/"envelope"/"header" 538 tests and "redirect" action discussed in Sieve [RFC5228] also apply 539 to this document. 541 External list memberships ought to be treated as if they are an 542 integral part of the script, so a temporary failure to access an 543 external list SHOULD be handled in the same way as a temporary 544 failure to retrieve the Sieve script itself. 546 For example, if the Sieve script is stored in the Lightweight 547 Directory Access Protocol [RFC4510] and the script can't be retrieved 548 when a message is processed (perhaps the LDAP server is unavailable), 549 then the Sieve engine might delay message delivery until the script 550 can be retrieved successfully. Similarly, if an external list is 551 stored in LDAP and that LDAP server is unavailable, the Sieve engine 552 would take the same action -- delay message delivery and try again 553 later. 555 Protocols/APIs used to retrieve/verify external list membership MUST 556 provide an appropriate level of confidentiality and authentication. 557 Usually, that will be at least the same level of confidentiality as 558 protocols/APIs used to retrieve Sieve scripts, but only the 559 implementation (or deployment) will know what is appropriate. 560 There's a difference, for example, between making an LDAP request on 561 a closed LAN that's only used for trusted servers (it may be that 562 neither encryption nor authentication is needed), on a firewalled LAN 563 internal to a company (it might be OK to skip encryption, depending 564 upon policy), and on the open Internet (encryption and authentication 565 are probably both required). It also matters whether the list being 566 accessed is private or public (no encryption or authentication may be 567 needed for public data, even on the Internet). 569 Having the processing and outcome of a Sieve script depend on the 570 contents of external data can allow someone with control of the 571 external data to have unusual, and perhaps unauthorized, control of 572 the script -- and, consequently, of the disposition of the user's 573 email. A user using such a list for spam control, for example, might 574 find important mail being discarded because of tampering with the 575 list. Someone using redirect to an external list could have her 576 email redirected to the wrong eyes because of such tampering. 577 Security and integrity protection of external lists is as important 578 as protection of the Sieve script itself. 580 Implementations of this extension should keep in mind that matching 581 values against an externally stored list can be IO and/or CPU 582 intensive. This can be used to deny service to the mailserver and/or 583 to servers providing access to externally stored mailing lists. A 584 naive implementation, such as the one that tries to retrieve content 585 of the whole list to perform matching can make this worse. 587 But note that many protocols that can be used for accessing 588 externally stored lists support flexible searching features that can 589 be used to minimize network traffic and load on the directory 590 service. For example, LDAP allows for search filters. 591 Implementations SHOULD use such features whenever they can. 593 Many organizations support external lists with thousands of 594 recipients. In order to avoid mailbombs when redirecting a message 595 to an externally stored list, implementations SHOULD enforce limits 596 on the number of recipients and/or on domains to which such 597 recipients belong. 599 Note in particular that it can be too easy for a script to use 600 redirect :list ":addrbook:default"; 601 to send messages to "everyone in your address book", and one can 602 easily imagine both intentional and accidental abuse. The situation 603 can be even worse for, say, ":addrbook:corporate". Warnings, as well 604 as enforced limits, are appropriate here. 606 Applications SHOULD ensure appropriate restrictions are in place to 607 protect sensitive information that might be revealed by "addrbook" 608 URNs from access or modification by untrusted sources. 610 4. IANA Considerations 612 4.1. Registration of Sieve Extension 614 The following template specifies the IANA registration of the Sieve 615 extension specified in this document. This information should be 616 added to the list of sieve extensions given on 617 http://www.iana.org/assignments/sieve-extensions. 619 To: iana@iana.org 621 Subject: Registration of new Sieve extension 623 Capability name: extlists 625 Description: Adds the ":list" match type to certain Sieve tests, and 626 the ":list" argument to the "redirect" action. The ":list" match 627 type changes tests to match values against values stored in one 628 or more externally stored lists. The ":list" argument to the 629 redirect action changes the redirect action to forward the 630 message to email addresses stored in the externally stored list. 632 RFC number: [[this RFC]] 634 Contact address: Sieve mailing list 636 4.2. Registration of ManageSieve Capability 638 The following requests IANA to register a new ManageSieve Capability 639 according to the IANA registration template specified in [RFC5804]: 641 To: iana@iana.org 643 Subject: ManageSieve Capability Registration 645 Capability name: extlists 647 Description: This capability is returned if the server supports the 648 "extlists" [[this RFC]] Sieve extension. 650 Relevant publications: [[this RFC]], Section 2.8 651 Person & email address to contact for further information: Sieve 652 mailing list 654 Author/Change controller: IESG 656 4.3. Creation of Sieve URN Parameters registry 658 The following requests IANA to create a new registry under "Sieve 659 Extensions" for Sieve URN Parameters. Registration into this 660 registry is according to the "Specification Required" policy 661 [RFC5226]. 663 The registry will contain the following two items: 665 URN parameter name: The name of the URN parameter. If the name is 666 "paramname", the resulting top-level URN will be 667 "urn:ietf:params:sieve:paramname". 669 Reference: The document and section where the definition of the 670 parameter can be found. Be sure to include the section number as 671 well as the document reference, so the documentation is easy to 672 find. 674 The documentation -- which will be in the referenced document and 675 section, and will not be included in the registry -- MUST include the 676 following information (see Section 2.6 for an example): 678 URN parameter name: The name of the URN parameter. 680 URN parameter syntax: The syntax of the parameter and any sub- 681 parameters, which SHOULD be specified using ABNF [RFC5234]. 683 Intended usage: A detailed description of how the parameter and 684 any sub-parameters are expected to be used. This is the place 685 to define static sub-parameters, registries for sub- 686 parameters, options, registries for options, and so on. 688 Interoperability considerations: Any notes specific to 689 interoperability issues. This is where to put mandatory-to- 690 implement sub-parameters and the like. 692 Security considerations: Any notes specific to security and 693 privacy issues. 695 Contact: Contact information, in case there are questions. 697 4.4. Registration of the "addrbook" URN parameter 699 The following requests IANA to register a new Sieve URN parameter in 700 the registry defined in Section 4.3. 702 URN parameter name: addrbook 704 Reference: [[this RFC]], Section 2.6 706 4.5. Registration of "sieve" URN sub-namespace 708 The following requests IANA to register a new URN sub-namespace 709 within the IETF URN Sub-namespace for Registered Protocol Parameter 710 Identifiers defined in [RFC3553]. 712 Registry name: sieve 714 Specification: [[this RFC]] 716 Repository: [[the registry created in Section 4.3]] 718 Index value: Sub-parameters MUST be specified in UTF-8, using 719 standard URI encoding where necessary. 721 5. Acknowledgements 723 Thanks to Alexandros Vellis, Nigel Swinson, Ned Freed, Kjetil Torgrim 724 Homme, Dave Cridland, Cyrus Daboo, Pete Resnick, and Robert Burrell 725 Donkin for ideas, comments and suggestions. Kristin Hubner also 726 helped greatly with the examples. 728 6. References 730 6.1. Normative References 732 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 733 Requirement Levels", BCP 14, RFC 2119, March 1997. 735 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 736 Resource Identifier (URI): Generic Syntax", STD 66, 737 RFC 3986, January 2005. 739 [RFC4151] Kindberg, T. and S. Hawke, "The 'tag' URI Scheme", 740 RFC 4151, October 2005. 742 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 743 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 744 May 2008. 746 [RFC5228] Guenther, P. and T. Showalter, "Sieve: An Email Filtering 747 Language", RFC 5228, January 2008. 749 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 750 Specifications: ABNF", STD 68, RFC 5234, January 2008. 752 [RFC5804] Melnikov, A. and T. Martin, "A Protocol for Remotely 753 Managing Sieve Scripts", RFC 5804, July 2010. 755 6.2. Informative References 757 [I-D.ietf-vcarddav-carddav] 758 Daboo, C., "vCard Extensions to WebDAV (CardDAV)", 759 draft-ietf-vcarddav-carddav-10 (work in progress), 760 November 2009. 762 [RFC2244] Newman, C. and J. Myers, "ACAP -- Application 763 Configuration Access Protocol", RFC 2244, November 1997. 765 [RFC3553] Mealling, M., Masinter, L., Hardie, T., and G. Klyne, "An 766 IETF URN Sub-namespace for Registered Protocol 767 Parameters", BCP 73, RFC 3553, June 2003. 769 [RFC4510] Zeilenga, K., "Lightweight Directory Access Protocol 770 (LDAP): Technical Specification Road Map", RFC 4510, 771 June 2006. 773 [RFC5229] Homme, K., "Sieve Email Filtering: Variables Extension", 774 RFC 5229, January 2008. 776 [RFC5231] Segmuller, W. and B. Leiba, "Sieve Email Filtering: 777 Relational Extension", RFC 5231, January 2008. 779 [RFC5233] Murchison, K., "Sieve Email Filtering: Subaddress 780 Extension", RFC 5233, January 2008. 782 [RFC5235] Daboo, C., "Sieve Email Filtering: Spamtest and Virustest 783 Extensions", RFC 5235, January 2008. 785 [RFC5260] Freed, N., "Sieve Email Filtering: Date and Index 786 Extensions", RFC 5260, July 2008. 788 [RFC5435] Melnikov, A., Leiba, B., Segmuller, W., and T. Martin, 789 "Sieve Email Filtering: Extension for Notifications", 790 RFC 5435, January 2009. 792 [RFC5437] Saint-Andre, P. and A. Melnikov, "Sieve Notification 793 Mechanism: Extensible Messaging and Presence Protocol 794 (XMPP)", RFC 5437, January 2009. 796 [RFC5463] Freed, N., "Sieve Email Filtering: Ihave Extension", 797 RFC 5463, March 2009. 799 [RFC5703] Hansen, T. and C. Daboo, "Sieve Email Filtering: MIME Part 800 Tests, Iteration, Extraction, Replacement, and Enclosure", 801 RFC 5703, October 2009. 803 Authors' Addresses 805 Alexey Melnikov 806 Isode Limited 807 5 Castle Business Village 808 36 Station Road 809 Hampton, Middlesex TW12 2BX 810 UK 812 Email: Alexey.Melnikov@isode.com 814 Barry Leiba 815 Huawei Technologies 817 Phone: +1 646 827 0648 818 Email: barryleiba@computer.org 819 URI: http://internetmessagingtechnology.org/