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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group M. Blanchet 3 Internet-Draft Viagenie 4 Intended status: Informational A. Sullivan 5 Expires: January 12, 2012 July 11, 2011 7 Stringprep Revision Problem Statement 8 draft-ietf-precis-problem-statement-03.txt 10 Abstract 12 Using Unicode codepoints in protocol strings that expect comparison 13 with other strings requires preparation of the string that contains 14 the Unicode codepoints. Internationalizing Domain Names in 15 Applications (IDNA2003) defined and used Stringprep and Nameprep. 16 Other protocols subsequently defined Stringprep profiles. A new 17 approach different from Stringprep and Nameprep is used for a 18 revision of IDNA2003 (called IDNA2008). Other Stringprep profiles 19 need to be similarly updated or a replacement of Stringprep needs to 20 be designed. This document outlines the issues to be faced by those 21 designing a Stringprep replacement. 23 Status of this Memo 25 This Internet-Draft is submitted in full conformance with the 26 provisions of BCP 78 and BCP 79. 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF). Note that other groups may also distribute 30 working documents as Internet-Drafts. The list of current Internet- 31 Drafts is at http://datatracker.ietf.org/drafts/current/. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 This Internet-Draft will expire on January 12, 2012. 40 Copyright Notice 42 Copyright (c) 2011 IETF Trust and the persons identified as the 43 document authors. All rights reserved. 45 This document is subject to BCP 78 and the IETF Trust's Legal 46 Provisions Relating to IETF Documents 47 (http://trustee.ietf.org/license-info) in effect on the date of 48 publication of this document. Please review these documents 49 carefully, as they describe your rights and restrictions with respect 50 to this document. Code Components extracted from this document must 51 include Simplified BSD License text as described in Section 4.e of 52 the Trust Legal Provisions and are provided without warranty as 53 described in the Simplified BSD License. 55 This document may contain material from IETF Documents or IETF 56 Contributions published or made publicly available before November 57 10, 2008. The person(s) controlling the copyright in some of this 58 material may not have granted the IETF Trust the right to allow 59 modifications of such material outside the IETF Standards Process. 60 Without obtaining an adequate license from the person(s) controlling 61 the copyright in such materials, this document may not be modified 62 outside the IETF Standards Process, and derivative works of it may 63 not be created outside the IETF Standards Process, except to format 64 it for publication as an RFC or to translate it into languages other 65 than English. 67 Table of Contents 69 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 70 2. Issues raised during newprep BOF . . . . . . . . . . . . . . . 5 71 3. Major Topics for Consideration . . . . . . . . . . . . . . . . 6 72 3.1. Comparison . . . . . . . . . . . . . . . . . . . . . . . . 6 73 3.1.1. Types of Identifiers . . . . . . . . . . . . . . . . . 6 74 3.1.2. Effect of comparison . . . . . . . . . . . . . . . . . 7 75 3.2. Dealing with characters . . . . . . . . . . . . . . . . . 7 76 3.2.1. Case folding, case sensitivity, and case 77 preservation . . . . . . . . . . . . . . . . . . . . . 7 78 3.2.2. Stringprep and NFKC . . . . . . . . . . . . . . . . . 7 79 3.2.3. Character mapping . . . . . . . . . . . . . . . . . . 8 80 3.2.4. Prohibited characters . . . . . . . . . . . . . . . . 8 81 3.2.5. Internal structure, delimiters, and special 82 characters . . . . . . . . . . . . . . . . . . . . . . 9 83 3.3. Where the data comes from and where it goes . . . . . . . 9 84 3.3.1. User input and the source of protocol elements . . . . 9 85 3.3.2. User output . . . . . . . . . . . . . . . . . . . . . 10 86 3.3.3. Operations . . . . . . . . . . . . . . . . . . . . . . 10 87 3.3.4. Some useful classes of strings . . . . . . . . . . . . 11 88 4. Considerations for Stringprep replacement . . . . . . . . . . 12 89 5. Security Considerations . . . . . . . . . . . . . . . . . . . 12 90 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 91 7. Discussion home for this draft . . . . . . . . . . . . . . . . 12 92 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 93 9. Informative References . . . . . . . . . . . . . . . . . . . . 13 94 Appendix A. Protocols known to be using Stringprep . . . . . . . 16 95 Appendix B. Detailed discussion of protocols under 96 consideration . . . . . . . . . . . . . . . . . . . . 17 97 Appendix C. Changes between versions . . . . . . . . . . . . . . 17 98 C.1. 00 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 99 C.2. 01 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 100 C.3. 02 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 101 C.4. 03 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 102 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18 104 1. Introduction 106 Internationalizing Domain Names in Applications (IDNA2003) [RFC3490], 107 [RFC3491], [RFC3492], [RFC3454] described a mechanism for encoding 108 Unicode labels making up Internationalized Domain Names (IDNs) as 109 standard DNS labels. The labels were processed using a method called 110 Nameprep [RFC3491] and Punycode [RFC3492]. That method was specific 111 to IDNA2003, but is generalized as Stringprep [RFC3454]. The general 112 mechanism can be used to help other protocols with similar needs, but 113 with different constraints than IDNA2003. 115 Stringprep defines a framework within which protocols define their 116 Stringprep profiles. Known IETF specifications using Stringprep are 117 listed below: 118 o The Nameprep profile [RFC3490] for use in Internationalized Domain 119 Names (IDNs); 120 o NFSv4 [RFC3530] and NFSv4.1 [RFC5661]; 121 o The iSCSI profile [RFC3722] for use in Internet Small Computer 122 Systems Interface (iSCSI) Names; 123 o EAP [RFC3748]; 124 o The Nodeprep and Resourceprep profiles [RFC3920] for use in the 125 Extensible Messaging and Presence Protocol (XMPP), and the XMPP to 126 CPIM mapping [RFC3922] (the latter of these relies on the former); 127 o The Policy MIB profile [RFC4011] for use in the Simple Network 128 Management Protocol (SNMP); 129 o The SASLprep profile [RFC4013] for use in the Simple 130 Authentication and Security Layer (SASL), and SASL itself 131 [RFC4422]; 132 o TLS [RFC4279]; 133 o IMAP4 using SASLprep [RFC4314]; 134 o The trace profile [RFC4505] for use with the SASL ANONYMOUS 135 mechanism; 136 o The LDAP profile [RFC4518] for use with LDAP [RFC4511] and its 137 authentication methods [RFC4513]; 138 o Plain SASL using SASLprep [RFC4616]; 139 o NNTP using SASLprep [RFC4643]; 140 o PKIX subject identification using LDAPprep [RFC4683]; 141 o Internet Application Protocol Collation Registry [RFC4790]; 142 o SMTP Auth using SASLprep [RFC4954]; 143 o POP3 Auth using SASLprep [RFC5034]; 144 o TLS SRP using SASLprep [RFC5054]; 145 o IRI and URI in XMPP [RFC5122]; 146 o PKIX CRL using LDAPprep [RFC5280]; 147 o IAX using Nameprep [RFC5456]; 148 o SASL SCRAM using SASLprep [RFC5802]; 149 o Remote management of Sieve using SASLprep [RFC5804]; 150 o The i;unicode-casemap Unicode Collation [RFC5051]. 152 There turned out to be some difficulties with IDNA2003, documented in 153 [RFC4690]. These difficulties led to a new IDN specification, called 154 IDNA2008 [RFC5890], [RFC5891], [RFC5892], [RFC5893]. Additional 155 background and explanations of the decisions embodied in IDNA2008 is 156 presented in [RFC5894]. One of the effects of IDNA2008 is that 157 Nameprep and Stringprep are not used at all. Instead, an algorithm 158 based on Unicode properties of codepoints is defined. That algorithm 159 generates a stable and complete table of the supported Unicode 160 codepoints. This algorithm is based on an inclusion-based approach, 161 instead of the exclusion-based approach of Stringprep/Nameprep. 163 This document lists the shortcomings and issues found by protocols 164 listed above that defined Stringprep profiles. It also lists some 165 early conclusions and requirements for a potential replacement of 166 Stringprep. 168 2. Issues raised during newprep BOF 170 During IETF 77, a BOF discussed the current state of the protocols 171 that have defined Stringprep profiles [NEWPREP]. The main 172 conclusions from that discussion were as follows: 173 o Stringprep is bound to a specific version of Unicode: 3.2. 174 Stringprep has not been updated to new versions of Unicode. 175 Therefore, the protocols using Stringprep are stuck to Unicode 176 3.2. 177 o The protocols need to be updated to support new versions of 178 Unicode. The protocols would like to not be bound to a specific 179 version of Unicode, but rather have better Unicode agility in the 180 way of IDNA2008. This is important partly because it is usually 181 impossible for an application to require Unicode 3.2; the 182 application gets whatever version of Unicode is available on the 183 host. 184 o The protocols require better bidirectional support (bidi) than 185 currently offered by Stringprep. 186 o If the protocols are updated to use a new version of Stringprep or 187 another framework, then backward compatibility is an important 188 requirement. For example, Stringprep is based on and may use NFKC 189 [UAX15], while IDNA2008 mostly uses NFC [UAX15]. 190 o Protocols use each other; for example, a protocol can use user 191 identifiers that are later passed to SASL, LDAP or another 192 authentication mechanism. Therefore, common set of rules or 193 classes of strings are preferred over specific rules for each 194 protocol. 196 Protocols that use Stringprep profiles use strings for different 197 purposes: 198 o XMPP uses a different Stringprep profile for each part of the XMPP 199 address (JID): a localpart which is similar to a username and used 200 for authentication, a domainpart which is a domain name and a 201 resource part which is less restrictive than the localpart. 202 o iSCSI uses a Stringprep profile for the IQN, which is very similar 203 to (often is) a DNS domain name. 204 o SASL and LDAP uses a Stringprep profile for usernames. 205 o LDAP uses a set of Stringprep profiles. 207 During the newprep BOF, it was the consensus of the attendees that it 208 would be highly desirable to have a replacement of Stringprep, with 209 similar characteristics to IDNA2008. That replacement should be 210 defined so that the protocols could use internationalized strings 211 without a lot of specialized internationalization work, since 212 internationalization expertise is not available in the respective 213 protocols or working groups. 215 3. Major Topics for Consideration 217 This section provides an overview of major topics that a Stringprep 218 replacement needs to address. The headings correspond roughly with 219 categories under which known Stringprep-using protocol RFCs have been 220 evaluated. For the details of those evaluations, see Appendix A. 222 3.1. Comparison 224 3.1.1. Types of Identifiers 226 Following [I-D.iab-identifier-comparison], we can organize 227 identifiers into three classes in respect of how they may be compared 228 with one another: 230 Absolute Identifiers Identifiers that can be compared byte-by-byte 231 for equality. 232 Definite Identifiers Identifiers that have a well-defined comparison 233 algorithm on which all parties agree. 234 Indefinite Identifiers Identifiers that have no single comparison 235 algorithm on which all parties agree. 237 Definite Identifiers include cases like the comparison of Unicode 238 code points in different encodings: they do not match byte for byte, 239 but can all be converted to a single encoding which then does match 240 byte for byte. Indefinite Identifiers are sometimes algorithmically 241 comparable by well-specified subsets of parties. For more discussion 242 of these categories, see [I-D.iab-identifier-comparison]. 244 The section on treating the existing known cases, Appendix A uses 245 these categories. 247 3.1.2. Effect of comparison 249 The three classes of comparison style outlined in Section 3.1.1 may 250 have different effects when applied. It is necessary to evaluate the 251 effects if a comparison results in a false positive, and what the 252 effects are if a comparison results in a false negative, especially 253 in terms of the consequences to security and usability. 255 3.2. Dealing with characters 257 This section outlines a range of issues having to do with characters 258 in the target protocols, and spends some effort to outline the ways 259 in which IDNA2008 might be a good analogy to other protocols, and 260 ways in which it might be a poor one. 262 3.2.1. Case folding, case sensitivity, and case preservation 264 In IDNA2003, labels are always mapped to lower case before the 265 Punycode transformation. In IDNA2008, there is no mapping at all: 266 input is either a valid U-label or it is not. At the same time, 267 upper-case characters are by definition not valid U-labels, because 268 they fall into the Unstable category (category B) of [RFC5892]. 270 If there are protocols that require upper and lower cases be 271 preserved, then the analogy with IDNA2008 will break down. 272 Accordingly, existing protocols are to be evaluated according to the 273 following criteria: 275 1. Does the protocol use case folding? For all blocks of code 276 points, or just for certain subsets? 277 2. Is the system or protocol case sensitive? 278 3. Does the system or protocol preserve case? 280 3.2.2. Stringprep and NFKC 282 Stringprep profiles may use normalization. If they do, they use NFKC 283 [UAX15]. It is not clear that NFKC is the right normalization to use 284 in all cases. In [UAX15], there is the following observation 285 regarding Normalization Forms KC and KD: "It is best to think of 286 these Normalization Forms as being like uppercase or lowercase 287 mappings: useful in certain contexts for identifying core meanings, 288 but also performing modifications to the text that may not always be 289 appropriate." For things like the spelling of users' names, then, 290 NFKC may not be the best form to use. At the same time, one of the 291 nice things about NFKC is that it deals with the width of characters 292 that are otherwise similar, by canonicalizing half-width to full- 293 width. This mapping step can be crucial in practice. The WG will 294 need to analyze the different use profiles and consider whether NFKC 295 or NFC is a better normalization for each profile. 297 For the purposes of evaluating an existing example of Stringprep use, 298 it is helpful to know whether it uses no normalization, NFKC, or NFC. 300 3.2.3. Character mapping 302 Along with the case mapping issues raised in Section 3.2.1, there is 303 the question of whether some characters are mapped either to other 304 characters or to nothing during Stringprep. [RFC3454], Section 3, 305 outlines a number of characters that are mapped to nothing, and also 306 permits Stringprep profiles to define their own mappings. 308 3.2.4. Prohibited characters 310 Along with case folding and other character mappings, many protocols 311 have characters that are simply disallowed. For example, control 312 characters and special characters such as "@" or "/" may be 313 prohibited in a protocol. 315 One of the primary changes of IDNA2008 is in the way it approaches 316 Unicode code points. IDNA2003 created an explicit list of excluded 317 or mapped-away characters; anything in Unicode 3.2 that was not so 318 listed could be assumed to be allowed under the protocol. IDNA2008 319 begins instead from the assumption that code points are disallowed, 320 and then relies on Unicode properties to derive whether a given code 321 point actually is allowed in the protocol. 323 Moreover, there is more than one class of "allowed in the protocol". 324 While some code points are disallowed outright, some are allowed only 325 in certain contexts. The reasons for the context-dependent rules 326 have to do with the way some characters are used. For instance, the 327 ZERO WIDTH JOINER and ZERO WIDTH NON-JOINER (ZWJ, U+200D and ZWNJ, 328 U+200C) are allowed with contextual rules because they are required 329 in some circumstances, yet are considered punctuation by Unicode and 330 would therefore be DISALLOWED under the usual IDNA2008 derivation 331 rules. The goal is to provide the widest possible repertoire of code 332 points possible and consistent with the traditional DNS, trusting to 333 the operators of individual zones to make sensible (and usually more 334 restrictive) policies for their zones. 336 IDNA2008 may be a poor model for what other protocols ought to do in 337 this case, because it is designed to support an old protocol that is 338 designed to operate on the scale of the entire Internet. Moreover, 339 IDNA2008 is intended to be deployed without any change to the base 340 DNS protocol. Other protocols may aim at deployment in more local 341 environments, or may have protocol version negotiation built in. 343 3.2.5. Internal structure, delimiters, and special characters 345 IDNA2008 has a special problem with delimiters, because the delimiter 346 "character" in the DNS wire format is not really part of the data. 347 In DNS, labels are not separated exactly; instead, a label carries 348 with it an indicator that says how long the label is. When the label 349 is presented in presentation format as part of a fully qualified 350 domain name, the label separator FULL STOP, U+002E (.) is used to 351 break up the labels. But because that label separator does not 352 travel with the wire format of the domain name, there is no way to 353 encode a different, "internationalized" separator in IDNA2008. 355 Other protocols may include characters with similar special meaning 356 within the protocol. Common characters for these purposes include 357 FULL STOP, U+002E (.); COMMERCIAL AT, U+0040 (@); HYPHEN-MINUS, 358 U+002D (-); SOLIDUS, U+002F (/); and LOW LINE, U+005F (_). The mere 359 inclusion of such a character in the protocol is not enough for it to 360 be considered similar to another protocol using the same character; 361 instead, handling of the character must be taken into consideration 362 as well. 364 An important issue to tackle here is whether it is valuable to map to 365 or from these special characters as part of the Stringprep 366 replacement. In some locales, the analogue to FULL STOP, U+002E is 367 some other character, and users may expect to be able to substitute 368 their normal stop for FULL STOP, U+002E. At the same time, there are 369 predictability arguments in favour of treating names with FULL STOP, 370 U+002E in them just the way they are treated under IDNA2008. 372 3.3. Where the data comes from and where it goes 374 3.3.1. User input and the source of protocol elements 376 Some protocol elements are provided by users, and others are not. 377 Those that are not may presumably be subject to greater restrictions, 378 whereas those that users provide likely need to permit the broadest 379 range of code points. The following questions are helpful: 381 1. Do users input the strings directly? 382 2. If so, how? (keyboard, stylus, voice, copy-paste, etc.) 383 3. Where do we place the dividing line between user interface and 384 protocol? (see [RFC5895]) 386 3.3.2. User output 388 Just as only some protocol elements are expected to be entered 389 directly by users, only some protocol elements are intended to be 390 consumed directly by users. It is important to know how users are 391 expected to be able to consume the protocol elements, because 392 different environments present different challenges. An element that 393 is only ever delivered as part of a vCard remains in machine-readable 394 format, so the problem of visual confusion is not a great one. Is 395 the protocol element published as part of a vCard, a web directory, 396 on a business card, or on "the side of a bus"? Do users use the 397 protocol element as an identifier (which means that they might enter 398 it again in some other context)? 400 3.3.3. Operations 402 Some strings are useful as part of the protocol but are not used as 403 input to other operations (for instance, purely informative or 404 descriptive text). Other strings are used directly as input to other 405 operations (such as cryptographic hash functions), or are used 406 together with other strings to (such as concatenating a string with 407 some others to form a unique identifier). 409 3.3.3.1. String classes 411 Strings often have a similar function in different protocols. For 412 instance, many different protocols contain user identifiers or 413 passwords. A single profile for all such uses might be desirable. 415 Often, a string in a protocol is effectively a protocol element from 416 another protocol. For instance, different systems might use the same 417 credentials database for authentication. 419 3.3.3.2. Community considerations 421 A Stringprep replacement that does anything more than just update 422 Stringprep to the latest version of Unicode will probably entail some 423 changes. It is important to identify the willingness of the 424 protocol-using community to accept backwards-incompatible changes. 425 By the same token, it is important to evaluate the desire of the 426 community for features not available under Stringprep. 428 3.3.3.3. What to do about Unicode changes 430 IDNA2008 uses an algorithm to derive the validity of a Unicode code 431 point for use under IDNA2008. It does this by using the properties 432 of each code point to test its validity. 434 This approach depends crucially on the idea that code points, once 435 valid for a protocol profile, will not later be made invalid. That 436 is not a guarantee currently provided by Unicode. Properties of code 437 points may change between versions of Unicode. Rarely, such a change 438 could cause a given code point to become invalid under a protocol 439 profile, even though the code point would be valid with an earlier 440 version of Unicode. This is not merely a theoretical possibility, 441 because it has occurred ([I-D.faltstrom-5892bis]). 443 Accordingly, a Stringprep replacement that intends to be Unicode 444 version agnostic will need to work out a mechanism to address cases 445 where incompatible changes occur because of new Unicode versions. 447 3.3.4. Some useful classes of strings 449 With the above considerations in hand, we can usefully classify 450 strings into the following categories, inspired by those outlined in 451 [I-D.saintandre-xmpp-i18n]: 453 Domainy strings Strings that are intended for use in a domain name 454 slot, as defined in [RFC5890]. Note that domainy strings could be 455 used outside a domain name slot: the question here is what the 456 eventual intended use for the string is, and not whether the 457 string is actually functioning as a domain name at any moment. 458 Namey strings Strings that are intended for use as identifiers but 459 that are not domainy strings. Namey strings are normally public 460 data within the protocol where they are used: these are intended 461 as identifiers that can be passed around to identify something. 462 Secretish strings Strings that are intended for use as passwords or 463 passphrases or other such type of token. Secretish strings are 464 normally not public data within the protocol where they are used: 465 they function as a token for authorization, and normally should 466 not be shared publicly. 467 Protocolish strings Strings that are intended to be used by the 468 protocol as free-form strings, but that have some significant 469 handling within the protocol. For instance, a protocol slot that 470 allows free-form text where case is not preserved would need to 471 have case mapping rules applied; in this case, the string would be 472 a protocolish string. 473 String blobs Elements of the protocol that look like strings to 474 users, but that are passed around in the protocol unchanged and 475 that cannot be used for comparison or other purposes. In effect, 476 these are strings that are part of a protocol payload, and are not 477 themselves part of the protocol at all. 479 4. Considerations for Stringprep replacement 481 The above suggests the following direction for the working group: 482 o A stringprep replacement should be defined. 483 o The replacement should take an approach similar to IDNA2008, in 484 that it enables Unicode agility. 485 o Protocols share similar characteristics of strings. Therefore, 486 defining i18n preparation algorithms for a (small) set of string 487 classes may be sufficient for most cases and provides the 488 coherence among a set of protocol friends. 489 o The sets of string classes need to be evaluated according to the 490 considerations that make up the headings in Section 3 491 o It is reasonable to limit scope to Unicode code points, and rule 492 the mapping of data from other character encodings outside the 493 scope of this effort. 494 o Recommendations for handling protocol incompatibilities resulting 495 from changes to Unicode are required. 497 Existing deployments already depend on Stringprep profiles. 498 Therefore, the working group will need to consider the effects of any 499 new strategy on existing deployments. By way of comparison, it is 500 worth noting that some characters were acceptable in IDNA labels 501 under IDNA2003, but are not protocol-valid under IDNA2008 (and 502 conversely). Different implementers may make different decisions 503 about what to do in such cases; this could have interoperability 504 effects. The working group will need to trade better support for 505 different linguistic environments against the potential side effects 506 of backward incompatibility. 508 5. Security Considerations 510 This document merely states what problems are to be solved, and does 511 not define a protocol. There are undoubtedly security implications 512 of the particular results that will come from the work to be 513 completed. 515 6. IANA Considerations 517 This document has no actions for IANA. 519 7. Discussion home for this draft 521 This document is intended to define the problem space discussed on 522 the precis@ietf.org mailing list. 524 8. Acknowledgements 526 This document is the product of the PRECIS IETF Working Group, and 527 participants in that Working Group were helpful in addressing issues 528 with the text. 530 Specific contributions came from David Black, Alan DeKok, Bill 531 McQuillan, Alexey Melnikov, Peter Saint-Andre, Dave Thaler, and 532 Yoshiro Yoneya. 534 Dave Thaler provided the "buckets" insight in Section 3.1.1, central 535 to the organization of the problem. 537 9. Informative References 539 [I-D.faltstrom-5892bis] 540 Faltstrom, P. and P. Hoffman, "The Unicode code points and 541 IDNA - Unicode 6.0", draft-faltstrom-5892bis-05 (work in 542 progress), June 2011. 544 [I-D.iab-identifier-comparison] 545 Thaler, D., "Issues in Identifier Comparison for Security 546 Purposes", draft-iab-identifier-comparison-00 (work in 547 progress), July 2011. 549 [I-D.saintandre-xmpp-i18n] 550 Saint-Andre, P., "Internationalized Addresses in XMPP", 551 draft-saintandre-xmpp-i18n-03 (work in progress), 552 March 2011. 554 [NEWPREP] "Newprep BoF Meeting Minutes", March 2010. 556 [RFC3454] Hoffman, P. and M. Blanchet, "Preparation of 557 Internationalized Strings ("stringprep")", RFC 3454, 558 December 2002. 560 [RFC3490] Faltstrom, P., Hoffman, P., and A. Costello, 561 "Internationalizing Domain Names in Applications (IDNA)", 562 RFC 3490, March 2003. 564 [RFC3491] Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep 565 Profile for Internationalized Domain Names (IDN)", 566 RFC 3491, March 2003. 568 [RFC3492] Costello, A., "Punycode: A Bootstring encoding of Unicode 569 for Internationalized Domain Names in Applications 570 (IDNA)", RFC 3492, March 2003. 572 [RFC3530] Shepler, S., Callaghan, B., Robinson, D., Thurlow, R., 573 Beame, C., Eisler, M., and D. Noveck, "Network File System 574 (NFS) version 4 Protocol", RFC 3530, April 2003. 576 [RFC3722] Bakke, M., "String Profile for Internet Small Computer 577 Systems Interface (iSCSI) Names", RFC 3722, April 2004. 579 [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. 580 Levkowetz, "Extensible Authentication Protocol (EAP)", 581 RFC 3748, June 2004. 583 [RFC3920] Saint-Andre, P., Ed., "Extensible Messaging and Presence 584 Protocol (XMPP): Core", RFC 3920, October 2004. 586 [RFC3922] Saint-Andre, P., "Mapping the Extensible Messaging and 587 Presence Protocol (XMPP) to Common Presence and Instant 588 Messaging (CPIM)", RFC 3922, October 2004. 590 [RFC4011] Waldbusser, S., Saperia, J., and T. Hongal, "Policy Based 591 Management MIB", RFC 4011, March 2005. 593 [RFC4013] Zeilenga, K., "SASLprep: Stringprep Profile for User Names 594 and Passwords", RFC 4013, February 2005. 596 [RFC4279] Eronen, P. and H. Tschofenig, "Pre-Shared Key Ciphersuites 597 for Transport Layer Security (TLS)", RFC 4279, 598 December 2005. 600 [RFC4314] Melnikov, A., "IMAP4 Access Control List (ACL) Extension", 601 RFC 4314, December 2005. 603 [RFC4422] Melnikov, A. and K. Zeilenga, "Simple Authentication and 604 Security Layer (SASL)", RFC 4422, June 2006. 606 [RFC4505] Zeilenga, K., "Anonymous Simple Authentication and 607 Security Layer (SASL) Mechanism", RFC 4505, June 2006. 609 [RFC4511] Sermersheim, J., "Lightweight Directory Access Protocol 610 (LDAP): The Protocol", RFC 4511, June 2006. 612 [RFC4513] Harrison, R., "Lightweight Directory Access Protocol 613 (LDAP): Authentication Methods and Security Mechanisms", 614 RFC 4513, June 2006. 616 [RFC4518] Zeilenga, K., "Lightweight Directory Access Protocol 617 (LDAP): Internationalized String Preparation", RFC 4518, 618 June 2006. 620 [RFC4616] Zeilenga, K., "The PLAIN Simple Authentication and 621 Security Layer (SASL) Mechanism", RFC 4616, August 2006. 623 [RFC4643] Vinocur, J. and K. Murchison, "Network News Transfer 624 Protocol (NNTP) Extension for Authentication", RFC 4643, 625 October 2006. 627 [RFC4683] Park, J., Lee, J., Lee, H., Park, S., and T. Polk, 628 "Internet X.509 Public Key Infrastructure Subject 629 Identification Method (SIM)", RFC 4683, October 2006. 631 [RFC4690] Klensin, J., Faltstrom, P., Karp, C., and IAB, "Review and 632 Recommendations for Internationalized Domain Names 633 (IDNs)", RFC 4690, September 2006. 635 [RFC4790] Newman, C., Duerst, M., and A. Gulbrandsen, "Internet 636 Application Protocol Collation Registry", RFC 4790, 637 March 2007. 639 [RFC4954] Siemborski, R. and A. Melnikov, "SMTP Service Extension 640 for Authentication", RFC 4954, July 2007. 642 [RFC5034] Siemborski, R. and A. Menon-Sen, "The Post Office Protocol 643 (POP3) Simple Authentication and Security Layer (SASL) 644 Authentication Mechanism", RFC 5034, July 2007. 646 [RFC5051] Crispin, M., "i;unicode-casemap - Simple Unicode Collation 647 Algorithm", RFC 5051, October 2007. 649 [RFC5054] Taylor, D., Wu, T., Mavrogiannopoulos, N., and T. Perrin, 650 "Using the Secure Remote Password (SRP) Protocol for TLS 651 Authentication", RFC 5054, November 2007. 653 [RFC5122] Saint-Andre, P., "Internationalized Resource Identifiers 654 (IRIs) and Uniform Resource Identifiers (URIs) for the 655 Extensible Messaging and Presence Protocol (XMPP)", 656 RFC 5122, February 2008. 658 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 659 Housley, R., and W. Polk, "Internet X.509 Public Key 660 Infrastructure Certificate and Certificate Revocation List 661 (CRL) Profile", RFC 5280, May 2008. 663 [RFC5456] Spencer, M., Capouch, B., Guy, E., Miller, F., and K. 664 Shumard, "IAX: Inter-Asterisk eXchange Version 2", 665 RFC 5456, February 2010. 667 [RFC5661] Shepler, S., Eisler, M., and D. Noveck, "Network File 668 System (NFS) Version 4 Minor Version 1 Protocol", 669 RFC 5661, January 2010. 671 [RFC5802] Newman, C., Menon-Sen, A., Melnikov, A., and N. Williams, 672 "Salted Challenge Response Authentication Mechanism 673 (SCRAM) SASL and GSS-API Mechanisms", RFC 5802, July 2010. 675 [RFC5804] Melnikov, A. and T. Martin, "A Protocol for Remotely 676 Managing Sieve Scripts", RFC 5804, July 2010. 678 [RFC5890] Klensin, J., "Internationalized Domain Names for 679 Applications (IDNA): Definitions and Document Framework", 680 RFC 5890, August 2010. 682 [RFC5891] Klensin, J., "Internationalized Domain Names in 683 Applications (IDNA): Protocol", RFC 5891, August 2010. 685 [RFC5892] Faltstrom, P., "The Unicode Code Points and 686 Internationalized Domain Names for Applications (IDNA)", 687 RFC 5892, August 2010. 689 [RFC5893] Alvestrand, H. and C. Karp, "Right-to-Left Scripts for 690 Internationalized Domain Names for Applications (IDNA)", 691 RFC 5893, August 2010. 693 [RFC5894] Klensin, J., "Internationalized Domain Names for 694 Applications (IDNA): Background, Explanation, and 695 Rationale", RFC 5894, August 2010. 697 [RFC5895] Resnick, P. and P. Hoffman, "Mapping Characters for 698 Internationalized Domain Names in Applications (IDNA) 699 2008", RFC 5895, September 2010. 701 [UAX15] "Unicode Standard Annex #15: Unicode Normalization Forms", 702 UAX 15, September 2009. 704 Appendix A. Protocols known to be using Stringprep 706 The known cases are here described in two ways. The types of 707 identifiers the protocol uses is first called out in the ID type 708 column (from Section 3.1.1), using the short forms "a" for Absolute, 709 "d" for Definite, and "i" for Indefinite. Next, there is a column 710 that contains an "i" if the protocol string comes from user input, an 711 "o" if the protocol string becomes user-facing output, "b" if both 712 are true, and "n" if neither is true. The remaining columns have an 713 "x" if and only if the protocol uses that class, as described in 714 Section 3.3.4. Values marked "-" indicate that an answer is not 715 useful; in this case, see detailed discussion in Appendix B. 717 +------+--------+-------+-------+-------+---------+---------+------+ 718 | RFC | IDtype | User? | Dom'y | Nam'y | Sec'ish | Pro'ish | Blob | 719 +------+--------+-------+-------+-------+---------+---------+------+ 720 | 3722 | a | o | | x | x | x | | 721 | 3748 | - | - | - | x | - | - | - | 722 | 3920 | a,d | b | | x | | x | | 723 | 4314 | a,d | b | | x | x | x | | 724 +------+--------+-------+-------+-------+---------+---------+------+ 726 Table 1 728 [[anchor21: The table still needs to be filled in, I am aware. 729 --ajs@anvilwalrusden.com]] 731 Appendix B. Detailed discussion of protocols under consideration 733 Below are detailed reviews of the protocols under consideration 734 (where such reviews are available). [[anchor22: These are to be cut 735 and pasted from the wiki. --ajs@anvilwalrusden.com]] 737 Appendix C. Changes between versions 739 Note to RFC Editor: This section should be removed prior to 740 publication. 742 C.1. 00 744 First WG version. Based on 745 draft-blanchet-precis-problem-statement-00. 747 C.2. 01 749 o Made clear that the document is talking only about Unicode code 750 points, and not any particular encoding. 751 o Substantially reorganized the document along the lines of the 752 review template at . 754 o Included specific questions for each topic for consideration. 755 o Moved spot for individual protocol review to appendix. Not 756 populated yet. 758 C.3. 02 760 o Cleared up details of comparison classes 761 o Added a section on changes in Unicode 763 C.4. 03 765 o Aligned comparison discussion with identifier discussion from 766 draft-iab-identifier-comparison-00 767 o Added section on classes of strings ("Namey" and so on) 769 Authors' Addresses 771 Marc Blanchet 772 Viagenie 773 2600 boul. Laurier, suite 625 774 Quebec, QC G1V 4W1 775 Canada 777 Email: Marc.Blanchet@viagenie.ca 778 URI: http://viagenie.ca 780 Andrew Sullivan 781 519 Maitland St. 782 London, ON N6B 2Z5 783 Canada 785 Email: ajs@anvilwalrusden.com