7Internet Engineering Task Force (IETF) P. Saint-Andre
8Request for Comments: 8265 Jabber.org
9Obsoletes: 7613 A. Melnikov
10Category: Standards Track Isode Ltd
11ISSN: 2070-1721 October 2017
14 Preparation, Enforcement, and Comparison of Internationalized Strings
15 Representing Usernames and Passwords
19 This document describes updated methods for handling Unicode strings
20 representing usernames and passwords. The previous approach was
21 known as SASLprep (RFC 4013) and was based on Stringprep (RFC 3454).
22 The methods specified in this document provide a more sustainable
23 approach to the handling of internationalized usernames and
24 passwords. This document obsoletes RFC 7613.
28 This is an Internet Standards Track document.
30 This document is a product of the Internet Engineering Task Force
31 (IETF). It represents the consensus of the IETF community. It has
32 received public review and has been approved for publication by the
33 Internet Engineering Steering Group (IESG). Further information on
34 Internet Standards is available in Section 2 of RFC 7841.
36 Information about the current status of this document, any errata,
37 and how to provide feedback on it may be obtained at
38 https://www.rfc-editor.org/info/rfc8265.
42 Copyright (c) 2017 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 (https://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.
58Saint-Andre & Melnikov Standards Track [Page 1]
60RFC 8265 PRECIS: Usernames and Passwords October 2017
65 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
66 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
67 3. Usernames . . . . . . . . . . . . . . . . . . . . . . . . . . 5
68 3.1. Definition . . . . . . . . . . . . . . . . . . . . . . . 5
69 3.2. Case Mapping vs. Case Preservation . . . . . . . . . . . 6
70 3.3. UsernameCaseMapped Profile . . . . . . . . . . . . . . . 7
71 3.3.1. Rules . . . . . . . . . . . . . . . . . . . . . . . . 7
72 3.3.2. Preparation . . . . . . . . . . . . . . . . . . . . . 8
73 3.3.3. Enforcement . . . . . . . . . . . . . . . . . . . . . 8
74 3.3.4. Comparison . . . . . . . . . . . . . . . . . . . . . 9
75 3.4. UsernameCasePreserved Profile . . . . . . . . . . . . . . 9
76 3.4.1. Rules . . . . . . . . . . . . . . . . . . . . . . . . 9
77 3.4.2. Preparation . . . . . . . . . . . . . . . . . . . . . 9
78 3.4.3. Enforcement . . . . . . . . . . . . . . . . . . . . . 10
79 3.4.4. Comparison . . . . . . . . . . . . . . . . . . . . . 10
80 3.5. Application-Layer Constructs . . . . . . . . . . . . . . 11
81 3.6. Examples . . . . . . . . . . . . . . . . . . . . . . . . 11
82 4. Passwords . . . . . . . . . . . . . . . . . . . . . . . . . . 13
83 4.1. Definition . . . . . . . . . . . . . . . . . . . . . . . 13
84 4.2. OpaqueString Profile . . . . . . . . . . . . . . . . . . 14
85 4.2.1. Preparation . . . . . . . . . . . . . . . . . . . . . 14
86 4.2.2. Enforcement . . . . . . . . . . . . . . . . . . . . . 14
87 4.2.3. Comparison . . . . . . . . . . . . . . . . . . . . . 15
88 4.3. Examples . . . . . . . . . . . . . . . . . . . . . . . . 15
89 5. Use in Application Protocols . . . . . . . . . . . . . . . . 16
90 6. Migration . . . . . . . . . . . . . . . . . . . . . . . . . . 17
91 6.1. Usernames . . . . . . . . . . . . . . . . . . . . . . . . 17
92 6.2. Passwords . . . . . . . . . . . . . . . . . . . . . . . . 19
93 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
94 7.1. UsernameCaseMapped Profile . . . . . . . . . . . . . . . 20
95 7.2. UsernameCasePreserved Profile . . . . . . . . . . . . . . 20
96 7.3. OpaqueString Profile . . . . . . . . . . . . . . . . . . 21
97 7.4. Stringprep Profile . . . . . . . . . . . . . . . . . . . 22
98 8. Security Considerations . . . . . . . . . . . . . . . . . . . 22
99 8.1. Password/Passphrase Strength . . . . . . . . . . . . . . 22
100 8.2. Password/Passphrase Comparison . . . . . . . . . . . . . 22
101 8.3. Identifier Comparison . . . . . . . . . . . . . . . . . . 22
102 8.4. Reuse of PRECIS . . . . . . . . . . . . . . . . . . . . . 22
103 8.5. Reuse of Unicode . . . . . . . . . . . . . . . . . . . . 22
104 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 23
105 9.1. Normative References . . . . . . . . . . . . . . . . . . 23
106 9.2. Informative References . . . . . . . . . . . . . . . . . 24
107 Appendix A. Changes from RFC 7613 . . . . . . . . . . . . . . . 25
108 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 26
109 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26
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116RFC 8265 PRECIS: Usernames and Passwords October 2017
121 Usernames and passwords are widely used for authentication and
122 authorization on the Internet, either directly when provided in
123 plaintext (as in the PLAIN Simple Authentication and Security Layer
124 (SASL) mechanism [RFC4616] and the HTTP Basic scheme [RFC7617]) or
125 indirectly when provided as the input to a cryptographic algorithm
126 such as a hash function (as in the Salted Challenge Response
127 Authentication Mechanism (SCRAM) SASL mechanism [RFC5802] and the
128 HTTP Digest scheme [RFC7616]).
130 To increase the likelihood that the input and comparison of usernames
131 and passwords will work in ways that make sense for typical users
132 throughout the world, this document defines rules for handling
133 internationalized strings that represent usernames and passwords.
134 Such strings consist of code points from the Unicode coded character
135 set [Unicode], with special attention to code points outside the
136 ASCII range [RFC20]. The rules for handling such strings are
137 specified through profiles of the string classes defined in the
138 preparation, enforcement, and comparison of internationalized strings
139 (PRECIS) framework specification [RFC8264].
141 Profiles of the PRECIS framework enable software to handle Unicode
142 code points outside the ASCII range in an automated way, so that such
143 code points are treated carefully and consistently in application
144 protocols. In large measure, these profiles are designed to protect
145 application developers from the potentially negative consequences of
146 supporting the full range of Unicode code points. For instance, in
147 almost all application protocols it would be dangerous to treat the
148 Unicode code point "¹" (SUPERSCRIPT ONE, U+00B9) as equivalent to "1"
149 (DIGIT ONE, U+0031), because that would result in false accepts
150 during comparison, authentication, and authorization (e.g., an
151 attacker could easily spoof an account "user1@example.com").
153 Whereas a naive use of Unicode would make such attacks trivially
154 easy, the PRECIS profile defined here for usernames generally
155 protects applications from inadvertently causing such problems.
156 (Similar considerations apply to passwords, although here it is
157 desirable to support a wider range of characters so as to maximize
158 entropy for purposes of authentication.)
160 The methods defined here might be applicable wherever usernames or
161 passwords are used. However, the methods are not intended for use in
162 preparing strings that are not usernames (e.g., Lightweight Directory
163 Access Protocol (LDAP) distinguished names), nor in cases where
164 identifiers or secrets are not strings (e.g., keys and certificates)
165 or require specialized handling.
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172RFC 8265 PRECIS: Usernames and Passwords October 2017
175 Although the historical predecessor of this document was the SASLprep
176 profile of Stringprep [RFC3454]), the approach defined here can be
177 used by technologies other than SASL [RFC4422], such as HTTP
178 authentication as specified in [RFC7617] and [RFC7616].
180 This document does not modify the handling of internationalized
181 strings in usernames and passwords as prescribed by existing
182 application protocols that use SASLprep. If the community that uses
183 such an application protocol wishes to modernize its handling of
184 internationalized strings to use PRECIS instead of Stringprep, it
185 needs to explicitly update the existing application protocol
186 definition (one example is [RFC7622]). Non-coordinated updates to
187 protocol implementations are discouraged because they can have a
188 negative impact on interoperability and security.
192 A "username" or "user identifier" is a string of characters
193 designating an account on a computing device or system, often but not
194 necessarily for use by a person. Although some devices and systems
195 might allow a username to be part or all of a person's name and a
196 person might want their account designator to be part or all of their
197 name, because of the complexities involved, that outcome is not
198 guaranteed for all human names on all computing devices or systems
199 that follow the rules defined in this specification. Protocol
200 designers and application developers who wish to allow a wider range
201 of characters are encouraged to consider a separation between more
202 restrictive account identifiers and more expressive display names or
203 nicknames (see [RFC8266]).
205 A "password" is a string of characters that allows access to a
206 computing device or system, often associated with a particular
207 username. A password is not literally limited to a word, because a
208 password could be a passphrase consisting of more than one word,
209 perhaps separated by spaces, punctuation, or other non-alphanumeric
212 Some SASL mechanisms (e.g., CRAM-MD5, DIGEST-MD5, and SCRAM) specify
213 that the authentication identity used in the context of such
214 mechanisms is a "simple username" (see Section 2 of [RFC4422] as well
215 as [RFC4013]). Various application technologies also assume that the
216 identity of a user or account takes the form of a username (e.g.,
217 authentication for the Hypertext Transfer Protocol as specified in
218 [RFC7617] and [RFC7616]), whether or not they use SASL. Note well
219 that the exact form of a username in any particular SASL mechanism or
220 application technology is a matter for implementation and deployment;
221 note also that a username does not necessarily map to any particular
222 application identifier.
226Saint-Andre & Melnikov Standards Track [Page 4]
228RFC 8265 PRECIS: Usernames and Passwords October 2017
231 Many important terms used in this document are defined in [RFC5890],
232 [RFC6365], [RFC8264], and [Unicode]. The term "non-ASCII space"
233 refers to any Unicode code point having a Unicode general category of
234 "Zs", naturally with the exception of SPACE (U+0020).
236 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
237 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
238 "OPTIONAL" in this document are to be interpreted as described in
239 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
240 capitals, as shown here.
246 This document specifies that a username is a string of Unicode code
247 points [Unicode] that is structured as an ordered sequence of
248 "userparts" and expressed in a standard Unicode Encoding Form (such
249 as UTF-8 [RFC3629]). A userpart is allowed to contain only code
250 points that are allowed by the PRECIS IdentifierClass defined in
251 Section 4.2 of [RFC8264] and thus consists almost exclusively of
252 letters and digits. A username can consist of a single userpart or a
253 space-separated sequence of userparts.
255 The syntax for a username is defined as follows, using the Augmented
256 Backus-Naur Form (ABNF) [RFC5234].
258 username = userpart *(1*SP userpart)
259 userpart = 1*(idpoint)
261 ; an "idpoint" is a Unicode code point that
262 ; can be contained in a string conforming to
263 ; the PRECIS IdentifierClass
266 All code points and blocks not explicitly allowed in the PRECIS
267 IdentifierClass are disallowed; this includes private-use code
268 points, surrogate code points, and the other code points and blocks
269 that were defined as "Prohibited Output" in Section 2.3 of [RFC4013]
270 (when corrected per [Err1812]). In addition, common constructions
271 such as "user@example.com" (e.g., the Network Access Identifier from
272 [RFC7542]) are allowed as usernames under this specification, as they
273 were under [RFC4013].
275 Implementation Note: The username construct defined in this
276 document does not necessarily match what all deployed applications
277 might refer to as a "username" or "userid" but instead provides a
278 relatively safe subset of Unicode code points that can be used in
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284RFC 8265 PRECIS: Usernames and Passwords October 2017
287 existing SASL mechanisms and in application protocols that use
288 SASL, and even in most application protocols that do not currently
291 A username MUST NOT be zero bytes in length. This rule is to be
292 enforced after any normalization and mapping of code points.
294 This specification defines two profiles for usernames: the
295 UsernameCaseMapped profile performs case mapping, and the
296 UsernameCasePreserved performs case preservation (see further
297 discussion under Section 3.2).
299 In protocols that provide usernames as input to a cryptographic
300 algorithm such as a hash function, the client will need to perform
301 enforcement of the rules for the UsernameCaseMapped or
302 UsernameCasePreserved profile before applying the algorithm.
3043.2. Case Mapping vs. Case Preservation
306 In order to accommodate the widest range of username constructs in
307 applications, this document defines two username profiles:
308 UsernameCaseMapped and UsernameCasePreserved. These two profiles
309 differ only in their use (or not) of the Case Mapping Rule and are
312 Case mapping is a matter for the application protocol, protocol
313 implementation, or end deployment. In general, this document
314 suggests that it is preferable to apply the UsernameCaseMapped
315 profile and therefore perform case mapping, because not doing so can
316 lead to false accepts during authentication and authorization (as
317 described in [RFC6943]) and can result in confusion among end users,
318 given the prevalence of case mapping in many existing protocols and
319 applications. However, there can be good reasons to apply the
320 UsernameCasePreserved profile and thus not perform case mapping, such
321 as backward compatibility with deployed infrastructure.
325 o SASL mechanisms that follow the recommendations in this document
326 MUST specify whether and when case mapping is to be applied to
327 authentication identifiers. Because case mapping results in
328 information loss, in order to retain that information for as long
329 as possible during processing, implementations SHOULD delay any
330 case mapping to the last possible moment, such as when doing a
331 lookup by username, performing username comparisons, or generating
332 a cryptographic salt from a username (if the last possible moment
333 happens on a server, then decisions about case mapping can be a
334 matter of service deployment policy). In keeping with [RFC4422],
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340RFC 8265 PRECIS: Usernames and Passwords October 2017
343 SASL mechanisms are not to apply this or any other profile to
344 authorization identifiers, only to authentication identifiers.
346 o Application protocols that use SASL (such as IMAP [RFC3501] and
347 the Extensible Messaging and Presence Protocol (XMPP) [RFC6120])
348 and that directly reuse this profile MUST specify whether or not
349 case mapping is to be applied to authorization identifiers. Such
350 "SASL application protocols" SHOULD delay any case mapping of
351 authorization identifiers to the last possible moment, which
352 happens to necessarily be on the server side (this enables
353 decisions about case mapping to be a matter of service deployment
354 policy). In keeping with [RFC4422], SASL application protocols
355 are not to apply this or any other profile to authentication
356 identifiers, only to authorization identifiers.
358 o Application protocols that do not use SASL (such as HTTP
359 authentication with the HTTP Basic and Digest schemes as specified
360 in [RFC7617] and [RFC7616]) but that directly reuse this profile
361 MUST specify whether and when case mapping is to be applied to
362 authentication identifiers or authorization identifiers, or both.
363 Such "non-SASL application protocols" SHOULD delay any case
364 mapping to the last possible moment, such as when doing a lookup
365 by username, performing username comparisons, or generating a
366 cryptographic salt from a username (if the last possible moment
367 happens on the server, then decisions about case mapping can be a
368 matter of service deployment policy).
370 If the specification for a SASL mechanism, SASL application protocol,
371 or non-SASL application protocol uses the UsernameCaseMapped profile,
372 it MUST clearly describe whether case mapping is to be applied at the
373 level of the protocol itself, implementations thereof, or service
374 deployments (each of these approaches can be legitimate, depending on
375 the application in question).
3773.3. UsernameCaseMapped Profile
381 The following rules are defined for use within the UsernameCaseMapped
382 profile of the PRECIS IdentifierClass.
384 1. Width Mapping Rule: Map fullwidth and halfwidth code points to
385 their decomposition mappings (see Unicode Standard Annex #11
388 2. Additional Mapping Rule: There is no additional mapping rule.
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396RFC 8265 PRECIS: Usernames and Passwords October 2017
399 3. Case Mapping Rule: Map uppercase and titlecase code points to
400 their lowercase equivalents, preferably using the Unicode
401 toLowerCase() operation as defined in the Unicode Standard
402 [Unicode]; see further discussion in Section 3.2.
404 4. Normalization Rule: Apply Unicode Normalization Form C (NFC) to
407 5. Directionality Rule: Apply the "Bidi Rule" defined in [RFC5893]
408 to strings that contain right-to-left code points (i.e., each of
409 the six conditions of the Bidi Rule must be satisfied); for
410 strings that do not contain right-to-left code points, there is
411 no special processing for directionality.
415 An entity that prepares an input string for subsequent enforcement
416 according to this profile MUST proceed as follows (applying the steps
419 1. Apply the width mapping rule specified in Section 3.3.1. It is
420 necessary to apply the rule at this point because otherwise the
421 PRECIS "HasCompat" category specified in Section 9.17 of
422 [RFC8264] would forbid fullwidth and halfwidth code points.
424 2. Ensure that the string consists only of Unicode code points that
425 are explicitly allowed by the PRECIS IdentifierClass defined in
426 Section 4.2 of [RFC8264].
430 An entity that performs enforcement according to this profile MUST
431 prepare an input string as described in Section 3.3.2 and MUST also
432 apply the following rules specified in Section 3.3.1 in the order
437 2. Normalization Rule
439 3. Directionality Rule
441 After all of the foregoing rules have been enforced, the entity MUST
442 ensure that the username is not zero bytes in length (this is done
443 after enforcing the rules to prevent applications from mistakenly
444 omitting a username entirely, because when internationalized strings
445 are accepted, a non-empty sequence of characters can result in a
446 zero-length username after canonicalization).
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452RFC 8265 PRECIS: Usernames and Passwords October 2017
455 The result of the foregoing operations is an output string that
456 conforms to the UsernameCaseMapped profile. Until an implementation
457 produces such an output string, it MUST NOT treat the string as
458 conforming (in particular, it MUST NOT assume that an input string is
459 conforming before the enforcement operation has been completed).
463 An entity that performs comparison of two strings according to this
464 profile MUST prepare each string as specified in Section 3.3.2 and
465 then MUST enforce the rules specified in Section 3.3.3. The two
466 strings are to be considered equivalent if and only if they are an
467 exact octet-for-octet match (sometimes called "bit-string identity").
469 Until an implementation determines whether two strings are to be
470 considered equivalent, it MUST NOT treat them as equivalent (in
471 particular, it MUST NOT assume that two input strings are equivalent
472 before the comparison operation has been completed).
4743.4. UsernameCasePreserved Profile
478 The following rules are defined for use within the
479 UsernameCasePreserved profile of the PRECIS IdentifierClass.
481 1. Width Mapping Rule: Map fullwidth and halfwidth code points to
482 their decomposition mappings (see Unicode Standard Annex #11
485 2. Additional Mapping Rule: There is no additional mapping rule.
487 3. Case Mapping Rule: There is no case mapping rule.
489 4. Normalization Rule: Apply Unicode Normalization Form C (NFC) to
492 5. Directionality Rule: Apply the "Bidi Rule" defined in [RFC5893]
493 to strings that contain right-to-left code points (i.e., each of
494 the six conditions of the Bidi Rule must be satisfied); for
495 strings that do not contain right-to-left code points, there is
496 no special processing for directionality.
500 An entity that prepares a string for subsequent enforcement according
501 to this profile MUST proceed as follows (applying the steps in the
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508RFC 8265 PRECIS: Usernames and Passwords October 2017
511 1. Apply the width mapping rule specified in Section 3.4.1. It is
512 necessary to apply the rule at this point because otherwise the
513 PRECIS "HasCompat" category specified in Section 9.17 of
514 [RFC8264] would forbid fullwidth and halfwidth code points.
516 2. Ensure that the string consists only of Unicode code points that
517 are explicitly allowed by the PRECIS IdentifierClass defined in
518 Section 4.2 of [RFC8264].
522 An entity that performs enforcement according to this profile MUST
523 prepare a string as described in Section 3.4.2 and MUST also apply
524 the following rules specified in Section 3.4.1 in the order shown:
526 1. Normalization Rule
528 2. Directionality Rule
530 After all of the foregoing rules have been enforced, the entity MUST
531 ensure that the username is not zero bytes in length (this is done
532 after enforcing the rules to prevent applications from mistakenly
533 omitting a username entirely, because when internationalized strings
534 are accepted, a non-empty sequence of characters can result in a
535 zero-length username after canonicalization).
537 The result of the foregoing operations is an output string that
538 conforms to the UsernameCasePreserved profile. Until an
539 implementation produces such an output string, it MUST NOT treat the
540 string as conforming (in particular, it MUST NOT assume that an input
541 string is conforming before the enforcement operation has been
546 An entity that performs comparison of two strings according to this
547 profile MUST prepare each string as specified in Section 3.4.2 and
548 then MUST enforce the rules specified in Section 3.4.3. The two
549 strings are to be considered equivalent if and only if they are an
550 exact octet-for-octet match (sometimes called "bit-string identity").
552 Until an implementation determines whether two strings are to be
553 considered equivalent, it MUST NOT treat them as equivalent (in
554 particular, it MUST NOT assume that two input strings are equivalent
555 before the comparison operation has been completed).
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564RFC 8265 PRECIS: Usernames and Passwords October 2017
5673.5. Application-Layer Constructs
569 Both the UsernameCaseMapped and UsernameCasePreserved profiles enable
570 an application protocol, implementation, or deployment to create
571 application-layer constructs such as a username that is a space-
572 separated set of userparts like "Firstname Middlename Lastname".
573 Such a construct is not a profile of the PRECIS IdentifierClass,
574 because SPACE (U+0020) is not allowed in the IdentifierClass;
575 however, it can be created at the application layer because SPACE
576 (U+0020) can be used as a separator between instances of the PRECIS
577 IdentifierClass (e.g., userparts as defined in this specification).
581 The following examples illustrate a small number of userparts (not
582 usernames) that are consistent with the format defined above (note
583 that the characters "<" and ">" are used here to delineate the actual
584 userparts and are not part of the userpart strings).
586 +--------------------------+---------------------------------+
587 | # | Userpart | Notes |
588 +--------------------------+---------------------------------+
589 | 1 | <juliet@example.com> | The "at" sign ("@") is allowed |
590 | | | in the PRECIS IdentifierClass |
591 +--------------------------+---------------------------------+
593 +--------------------------+---------------------------------+
594 | 3 | <fußball> | The third character is LATIN |
595 | | | SMALL LETTER SHARP S (U+00DF) |
596 +--------------------------+---------------------------------+
597 | 4 | <π> | A userpart of GREEK SMALL |
598 | | | LETTER PI (U+03C0) |
599 +--------------------------+---------------------------------+
600 | 5 | <Σ> | A userpart of GREEK CAPITAL |
601 | | | LETTER SIGMA (U+03A3) |
602 +--------------------------+---------------------------------+
603 | 6 | <σ> | A userpart of GREEK SMALL |
604 | | | LETTER SIGMA (U+03C3) |
605 +--------------------------+---------------------------------+
606 | 7 | <ς> | A userpart of GREEK SMALL |
607 | | | LETTER FINAL SIGMA (U+03C2) |
608 +--------------------------+---------------------------------+
610 Table 1: A Sample of Legal Userparts
612 Regarding examples 2 and 3: although in German writing the character
613 eszett "ß" (LATIN SMALL LETTER SHARP S, U+00DF) can mostly be used
614 interchangeably with the two characters "ss", the userparts in these
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620RFC 8265 PRECIS: Usernames and Passwords October 2017
623 examples are different and (if desired) a server would need to
624 enforce a registration policy that disallows one of them if the other
627 Regarding examples 5, 6, and 7: optional case mapping of "Σ" (GREEK
628 CAPITAL LETTER SIGMA, U+03A3) to the lowercase character "σ" (GREEK
629 SMALL LETTER SIGMA, U+03C3) during comparison would result in
630 matching the userparts in examples 5 and 6; however, because the
631 PRECIS mapping rules do not account for the special status of the
632 character "ς" (GREEK SMALL LETTER FINAL SIGMA, U+03C2), the userparts
633 in examples 5 and 7 or examples 6 and 7 would not be matched during
636 The following examples illustrate strings that are not valid
637 userparts (not usernames) because they violate the format defined
640 +--------------------------+---------------------------------+
641 | # | Non-Userpart String | Notes |
642 +--------------------------+---------------------------------+
643 | 8 | <foo bar> | SPACE (U+0020) is disallowed in |
645 +--------------------------+---------------------------------+
646 | 9 | <> | Zero-length userpart |
647 +--------------------------+---------------------------------+
648 | 10| <henryⅣ> | The sixth character is ROMAN |
649 | | | NUMERAL FOUR (U+2163) |
650 +--------------------------+---------------------------------+
651 | 11| <∞> | A userpart of INFINITY (U+221E) |
652 +--------------------------+---------------------------------+
654 Table 2: A Sample of Strings That Violate the Userpart Rules
656 Regarding example 8: although this is not a valid userpart, it is a
657 valid username because it is a space-separated sequence of userparts.
659 Regarding example 10: the character "Ⅳ" (ROMAN NUMERAL FOUR, U+2163)
660 has a compatibility equivalent of the characters "I" (LATIN CAPITAL
661 LETTER I, U+0049) and "V" (LATIN CAPITAL LETTER V, U+0056), but code
662 points with compatibility equivalents are not allowed in the PRECIS
665 Regarding example 11: symbol characters such as "∞" (INFINITY,
666 U+221E) are not allowed in the PRECIS IdentifierClass.
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676RFC 8265 PRECIS: Usernames and Passwords October 2017
683 This document specifies that a password is a string of Unicode code
684 points [Unicode] that is conformant to the OpaqueString profile
685 (specified below) of the PRECIS FreeformClass defined in Section 4.3
686 of [RFC8264] and expressed in a standard Unicode Encoding Form (such
689 The syntax for a password is defined as follows, using the Augmented
690 Backus-Naur Form (ABNF) [RFC5234].
692 password = 1*(freepoint)
694 ; a "freepoint" is a Unicode code point that
695 ; can be contained in a string conforming to
696 ; the PRECIS FreeformClass
699 All code points and blocks not explicitly allowed in the PRECIS
700 FreeformClass are disallowed; this includes private-use code points,
701 surrogate code points, and the other code points and blocks defined
702 as "Prohibited Output" in Section 2.3 of [RFC4013] (when corrected
705 A password MUST NOT be zero bytes in length. This rule is to be
706 enforced after any normalization and mapping of code points.
708 Note: Some existing systems allow an empty string in places where
709 a password would be expected (e.g., command-line tools that might
710 be called from an automated script, or servers that might need to
711 be restarted without human intervention). From the perspective of
712 this document (and RFC 4013 before it), these empty strings are
713 not passwords but are workarounds for the practical difficulty of
714 using passwords in certain scenarios.
716 Note: The prohibition of zero-length passwords is not a
717 recommendation regarding password strength (because a password of
718 only one byte is highly insecure) but is meant to prevent
719 applications from mistakenly omitting a password entirely; such an
720 outcome is possible when internationalized strings are accepted,
721 because a non-empty sequence of characters can result in a zero-
722 length password after canonicalization.
724 In protocols that provide passwords as input to a cryptographic
725 algorithm such as a hash function, the client will need to perform
726 enforcement of the rules for the OpaqueString profile before applying
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732RFC 8265 PRECIS: Usernames and Passwords October 2017
735 the algorithm, because the password is not available to the server in
7384.2. OpaqueString Profile
740 The definition of the OpaqueString profile is provided in the
741 following sections, including detailed information about preparation,
742 enforcement, and comparison (for details on the distinction between
743 these actions, refer to [RFC8264]).
747 An entity that prepares a string according to this profile MUST
748 ensure that the string consists only of Unicode code points that are
749 explicitly allowed by the FreeformClass string class defined in
754 An entity that performs enforcement according to this profile MUST
755 prepare a string as described in Section 4.2.1 and MUST also apply
756 the rules specified below for the OpaqueString profile (these rules
757 MUST be applied in the order shown):
759 1. Width Mapping Rule: Fullwidth and halfwidth code points MUST NOT
760 be mapped to their decomposition mappings (see Unicode Standard
763 2. Additional Mapping Rule: Any instances of non-ASCII space MUST be
764 mapped to SPACE (U+0020); a non-ASCII space is any Unicode code
765 point having a Unicode general category of "Zs", with the
766 exception of SPACE (U+0020). As was the case in RFC 4013, the
767 inclusion of only SPACE (U+0020) prevents confusion with various
768 non-ASCII space code points, many of which are difficult to
769 reproduce across different input methods.
771 3. Case Mapping Rule: There is no case mapping rule (because mapping
772 uppercase and titlecase code points to their lowercase
773 equivalents would lead to false accepts and thus to reduced
776 4. Normalization Rule: Unicode Normalization Form C (NFC) MUST be
777 applied to all strings.
779 5. Directionality Rule: There is no directionality rule. The "Bidi
780 Rule" (defined in [RFC5893]) and similar rules are unnecessary
781 and inapplicable to passwords, because they can reduce the
782 repertoire of characters that are allowed in a string and
786Saint-Andre & Melnikov Standards Track [Page 14]
788RFC 8265 PRECIS: Usernames and Passwords October 2017
791 therefore reduce the amount of entropy that is possible in a
792 password. Such rules are intended to minimize the possibility
793 that the same string will be displayed differently on a layout
794 system set for right-to-left display and a layout system set for
795 left-to-right display; however, passwords are typically not
796 displayed at all and are rarely meant to be interoperable across
797 different layout systems in the way that non-secret strings like
798 domain names and usernames are. Furthermore, it is perfectly
799 acceptable for opaque strings other than passwords to be
800 presented differently in different layout systems, as long as the
801 presentation is consistent in any given layout system.
803 The result of the foregoing operations is an output string that
804 conforms to the OpaqueString profile. Until an implementation
805 produces such an output string, it MUST NOT treat the string as
806 conforming (in particular, it MUST NOT assume that an input string is
807 conforming before the enforcement operation has been completed).
811 An entity that performs comparison of two strings according to this
812 profile MUST prepare each string as specified in Section 4.2.1 and
813 then MUST enforce the rules specified in Section 4.2.2. The two
814 strings are to be considered equivalent if and only if they are an
815 exact octet-for-octet match (sometimes called "bit-string identity").
817 Until an implementation determines whether two strings are to be
818 considered equivalent, it MUST NOT treat them as equivalent (in
819 particular, it MUST NOT assume that two input strings are equivalent
820 before the comparison operation has been completed).
822 See Section 8.2 regarding comparison of passwords and passphrases.
826 The following examples illustrate a small number of passwords that
827 are consistent with the format defined above (note that the
828 characters "<" and ">" are used here to delineate the actual
829 passwords and are not part of the password strings).
842Saint-Andre & Melnikov Standards Track [Page 15]
844RFC 8265 PRECIS: Usernames and Passwords October 2017
847 +------------------------------------+------------------------------+
848 | # | Password | Notes |
849 +------------------------------------+------------------------------+
850 | 12| <correct horse battery staple> | SPACE (U+0020) is allowed |
851 +------------------------------------+------------------------------+
852 | 13| <Correct Horse Battery Staple> | Differs by case from |
854 +------------------------------------+------------------------------+
855 | 14| <πßå> | Non-ASCII letters are OK |
856 | | | (e.g., GREEK SMALL LETTER |
858 +------------------------------------+------------------------------+
859 | 15| <Jack of ♦s> | Symbols are OK (e.g., BLACK |
860 | | | DIAMOND SUIT (U+2666)) |
861 +------------------------------------+------------------------------+
862 | 16| <foo bar> | OGHAM SPACE MARK (U+1680) is |
863 | | | mapped to SPACE (U+0020); |
864 | | | thus, the full string is |
865 | | | mapped to <foo bar> |
866 +------------------------------------+------------------------------+
868 Table 3: A Sample of Legal Passwords
870 The following examples illustrate strings that are not valid
871 passwords because they violate the format defined above.
873 +------------------------------------+------------------------------+
874 | # | Password | Notes |
875 +------------------------------------+------------------------------+
876 | 17| <> | Zero-length passwords are |
878 +------------------------------------+------------------------------+
879 | 18| <my cat is a 	by> | Control characters like TAB |
880 | | | (U+0009) are disallowed |
881 +------------------------------------+------------------------------+
883 Table 4: A Sample of Strings That Violate the Password Rules
885 Note: Following the "XML Notation" used in [RFC3987], the character
886 TAB (U+0009) in example 18 is represented as 	 because otherwise
887 it could not be shown in running text.
8895. Use in Application Protocols
891 This specification defines only the PRECIS-based rules for the
892 handling of strings conforming to the UsernameCaseMapped and
893 UsernameCasePreserved profiles of the PRECIS IdentifierClass, and
894 strings conforming to the OpaqueString profile of the PRECIS
898Saint-Andre & Melnikov Standards Track [Page 16]
900RFC 8265 PRECIS: Usernames and Passwords October 2017
903 FreeformClass. It is the responsibility of an application protocol
904 to specify the protocol slots in which such strings can appear, the
905 entities that are expected to enforce the rules governing such
906 strings, and at what points during protocol processing or interface
907 handling the rules need to be enforced. See Section 6 of [RFC8264]
908 for guidelines on using PRECIS profiles in applications.
910 Above and beyond the PRECIS-based rules specified here, application
911 protocols can also define application-specific rules governing such
912 strings (rules regarding minimum or maximum length, further
913 restrictions on allowable code points or character ranges, safeguards
914 to mitigate the effects of visually similar characters, etc.),
915 application-layer constructs (see Section 3.5), and related matters.
917 Some PRECIS profile definitions encourage entities that enforce the
918 rules to be liberal in what they accept. However, for usernames and
919 passwords such a policy can be problematic, because it can lead to
920 false accepts. An in-depth discussion can be found in [RFC6943].
922 Applying the rules for any given PRECIS profile is not necessarily an
923 idempotent procedure for all code points. Therefore, an
924 implementation SHOULD apply the rules repeatedly until the output
925 string is stable; if the output string does not stabilize after
926 reapplying the rules three (3) additional times after the first
927 application, the implementation SHOULD terminate application of the
928 rules and reject the input string as invalid.
932 The rules defined in this specification differ slightly from those
933 defined by the SASLprep specification [RFC4013] (but not from
934 [RFC7613]). In order to smooth the process of migrating from
935 SASLprep to the approach defined herein, the following sections
936 describe these differences, along with their implications for
937 migration, in more detail.
941 Deployments that currently use SASLprep for handling usernames might
942 need to scrub existing data when they migrate to the rules defined in
943 this specification. In particular:
945 o SASLprep specified the use of Unicode Normalization Form KC
946 (NFKC), whereas the UsernameCaseMapped and UsernameCasePreserved
947 profiles employ Unicode Normalization Form C (NFC). In practice,
948 this change is unlikely to cause significant problems, because
949 NFKC provides methods for mapping Unicode code points with
950 compatibility equivalents to those equivalents, whereas the PRECIS
954Saint-Andre & Melnikov Standards Track [Page 17]
956RFC 8265 PRECIS: Usernames and Passwords October 2017
959 IdentifierClass entirely disallows Unicode code points with
960 compatibility equivalents (i.e., during comparison, NFKC is more
961 "aggressive" about finding matches than NFC). A few examples
962 might suffice to indicate the nature of the problem:
964 1. "ſ" (LATIN SMALL LETTER LONG S, U+017F) is compatibility
965 equivalent to "s" (LATIN SMALL LETTER S, U+0073).
967 2. "Ⅳ" (ROMAN NUMERAL FOUR, U+2163) is compatibility equivalent
968 to "I" (LATIN CAPITAL LETTER I, U+0049) and "V" (LATIN CAPITAL
971 3. "fi" (LATIN SMALL LIGATURE FI, U+FB01) is compatibility
972 equivalent to "f" (LATIN SMALL LETTER F, U+0066) and "i"
973 (LATIN SMALL LETTER I, U+0069).
975 Under SASLprep, the use of NFKC also handled the mapping of
976 fullwidth and halfwidth code points to their decomposition
979 For migration purposes, operators might want to search their
980 database of usernames for names containing Unicode code points
981 with compatibility equivalents and, where there is no conflict,
982 map those code points to their equivalents. Naturally, it is
983 possible that during this process the operator will discover
984 conflicting usernames; for instance, "HENRYIV" with the last two
985 code points being LATIN CAPITAL LETTER I (U+0049) and LATIN
986 CAPITAL LETTER V (U+0056) as opposed to "HENRYⅣ" with the last
987 character being "Ⅳ" (ROMAN NUMERAL FOUR, U+2163), which is
988 compatibility equivalent to U+0049 and U+0056). In these cases,
989 the operator will need to determine how to proceed, for instance,
990 by disabling the account whose name contains a Unicode code point
991 with a compatibility equivalent. Such cases are probably rare,
992 but it is important for operators to be aware of them.
994 o SASLprep mapped the "characters commonly mapped to nothing" (from
995 Appendix B.1 of [RFC3454]) to nothing, whereas the PRECIS
996 IdentifierClass entirely disallows most of these code points,
997 which correspond to the code points from the PRECIS "M" category
998 defined under Section 9.13 of [RFC8264]. For migration purposes,
999 the operator might want to remove from usernames any code points
1000 contained in the PRECIS "M" category (e.g., SOFT HYPHEN (U+00AD)).
1001 Because these code points would have been "mapped to nothing" in
1002 Stringprep, in practice a user would not notice the difference if,
1003 upon migration to PRECIS, the code points are removed.
1005 o SASLprep allowed uppercase and titlecase code points, whereas the
1006 UsernameCaseMapped profile maps uppercase and titlecase code
1010Saint-Andre & Melnikov Standards Track [Page 18]
1012RFC 8265 PRECIS: Usernames and Passwords October 2017
1015 points to their lowercase equivalents (by contrast, the
1016 UsernameCasePreserved profile matches SASLprep in this regard).
1017 For migration purposes, the operator can use either the
1018 UsernameCaseMapped profile (thus losing the case information) or
1019 the UsernameCasePreserved profile (thus ignoring case difference
1020 when comparing usernames).
1024 Depending on local service policy, migration from SASLprep to this
1025 specification might not involve any scrubbing of data (because
1026 passwords might not be stored in the clear anyway); however, service
1027 providers need to be aware of possible issues that might arise during
1028 migration. In particular:
1030 o SASLprep specified the use of Unicode Normalization Form KC
1031 (NFKC), whereas the OpaqueString profile employs Unicode
1032 Normalization Form C (NFC). Because NFKC is more aggressive about
1033 finding matches than NFC, in practice this change is unlikely to
1034 cause significant problems and indeed has the security benefit of
1035 probably resulting in fewer false accepts when comparing
1036 passwords. A few examples might suffice to indicate the nature of
1039 1. "ſ" (LATIN SMALL LETTER LONG S, U+017F) is compatibility
1040 equivalent to "s" (LATIN SMALL LETTER S, U+0073).
1042 2. "Ⅳ" (ROMAN NUMERAL FOUR, U+2163) is compatibility equivalent
1043 to "I" (LATIN CAPITAL LETTER I, U+0049) and "V" (LATIN CAPITAL
1046 3. "fi" (LATIN SMALL LIGATURE FI, U+FB01) is compatibility
1047 equivalent to "f" (LATIN SMALL LETTER F, U+0066) and "i"
1048 (LATIN SMALL LETTER I, U+0069).
1050 Under SASLprep, the use of NFKC also handled the mapping of
1051 fullwidth and halfwidth code points to their decomposition
1052 mappings. Although it is expected that code points with
1053 compatibility equivalents are rare in existing passwords, some
1054 passwords that matched when SASLprep was used might no longer work
1055 when the rules in this specification are applied.
1057 o SASLprep mapped the "characters commonly mapped to nothing" (from
1058 Appendix B.1 of [RFC3454]) to nothing, whereas the PRECIS
1059 FreeformClass entirely disallows such code points, which
1060 correspond to the code points from the PRECIS "M" category defined
1061 under Section 9.13 of [RFC8264]. In practice, this change will
1062 probably have no effect on comparison, but user-oriented software
1066Saint-Andre & Melnikov Standards Track [Page 19]
1068RFC 8265 PRECIS: Usernames and Passwords October 2017
1071 might reject such code points instead of ignoring them during
1072 password preparation.
10747. IANA Considerations
1076 IANA has made the updates described below.
10787.1. UsernameCaseMapped Profile
1080 IANA has added the following entry to the "PRECIS Profiles" registry.
1082 Name: UsernameCaseMapped.
1084 Base Class: IdentifierClass.
1086 Applicability: Usernames in security and application protocols.
1088 Replaces: The SASLprep profile of Stringprep.
1090 Width Mapping Rule: Map fullwidth and halfwidth code points to their
1091 decomposition mappings.
1093 Additional Mapping Rule: None.
1095 Case Mapping Rule: Map uppercase and titlecase code points to
1098 Normalization Rule: NFC.
1100 Directionality Rule: The "Bidi Rule" defined in RFC 5893 applies.
1102 Enforcement: To be defined by security or application protocols that
1105 Specification: Section 3.3 of RFC 8265.
11077.2. UsernameCasePreserved Profile
1109 IANA has added the following entry to the "PRECIS Profiles" registry.
1111 Name: UsernameCasePreserved.
1113 Base Class: IdentifierClass.
1115 Applicability: Usernames in security and application protocols.
1117 Replaces: The SASLprep profile of Stringprep.
1122Saint-Andre & Melnikov Standards Track [Page 20]
1124RFC 8265 PRECIS: Usernames and Passwords October 2017
1127 Width Mapping Rule: Map fullwidth and halfwidth code points to their
1128 decomposition mappings.
1130 Additional Mapping Rule: None.
1132 Case Mapping Rule: None.
1134 Normalization Rule: NFC.
1136 Directionality Rule: The "Bidi Rule" defined in RFC 5893 applies.
1138 Enforcement: To be defined by security or application protocols that
1141 Specification: Section 3.4 of RFC 8265.
11437.3. OpaqueString Profile
1145 IANA has added the following entry to the "PRECIS Profiles" registry.
1149 Base Class: FreeformClass.
1151 Applicability: Passwords and other opaque strings in security and
1152 application protocols.
1154 Replaces: The SASLprep profile of Stringprep.
1156 Width Mapping Rule: None.
1158 Additional Mapping Rule: Map non-ASCII space code points to SPACE
1161 Case Mapping Rule: None.
1163 Normalization Rule: NFC.
1165 Directionality Rule: None.
1167 Enforcement: To be defined by security or application protocols that
1170 Specification: Section 4.2 of RFC 8265.
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1180RFC 8265 PRECIS: Usernames and Passwords October 2017
11837.4. Stringprep Profile
1185 The Stringprep specification [RFC3454] did not provide for entries in
1186 the "Stringprep Profiles" registry to have any state except "Current"
1187 or "Not Current". Because RFC 7613 obsoleted RFC 4013, which
1188 registered the SASLprep profile of Stringprep, IANA previously marked
1189 that profile as "Not Current" and cited RFC 7613 as an additional
1190 reference. IANA has modified the profile so that the current
1191 document is now cited as the additional reference.
11938. Security Considerations
11958.1. Password/Passphrase Strength
1197 The ability to include a wide range of characters in passwords and
1198 passphrases can increase the potential for creating a strong password
1199 with high entropy. However, in practice, the ability to include such
1200 characters ought to be weighed against the possible need to reproduce
1201 them on various devices using various input methods.
12038.2. Password/Passphrase Comparison
1205 In systems that conform to modern best practices for security,
1206 verification of passwords during authentication will not use the
1207 comparison defined in Section 4.2.3. Instead, because the system
1208 performs cryptographic calculations to verify the password, it will
1209 prepare the password as defined in Section 4.2.1 and enforce the
1210 rules as defined in Section 4.2.2 before performing the relevant
12138.3. Identifier Comparison
1215 The process of comparing identifiers (such as SASL simple usernames,
1216 authentication identifiers, and authorization identifiers) can lead
1217 to either false rejects or false accepts, both of which have security
1218 implications. A more detailed discussion can be found in [RFC6943].
1222 The security considerations described in [RFC8264] apply to the
1223 IdentifierClass and FreeformClass string classes used in this
1224 document for usernames and passwords, respectively.
12268.5. Reuse of Unicode
1228 The security considerations described in [UTS39] apply to the use of
1229 Unicode code points in usernames and passwords.
1234Saint-Andre & Melnikov Standards Track [Page 22]
1236RFC 8265 PRECIS: Usernames and Passwords October 2017
12419.1. Normative References
1243 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
1244 Requirement Levels", BCP 14, RFC 2119,
1245 DOI 10.17487/RFC2119, March 1997,
1246 <https://www.rfc-editor.org/info/rfc2119>.
1248 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
1249 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
1250 2003, <https://www.rfc-editor.org/info/rfc3629>.
1252 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
1253 Specifications: ABNF", STD 68, RFC 5234,
1254 DOI 10.17487/RFC5234, January 2008,
1255 <https://www.rfc-editor.org/info/rfc5234>.
1257 [RFC5890] Klensin, J., "Internationalized Domain Names for
1258 Applications (IDNA): Definitions and Document Framework",
1259 RFC 5890, DOI 10.17487/RFC5890, August 2010,
1260 <https://www.rfc-editor.org/info/rfc5890>.
1262 [RFC6365] Hoffman, P. and J. Klensin, "Terminology Used in
1263 Internationalization in the IETF", BCP 166, RFC 6365,
1264 DOI 10.17487/RFC6365, September 2011,
1265 <https://www.rfc-editor.org/info/rfc6365>.
1267 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
1268 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
1269 May 2017, <https://www.rfc-editor.org/info/rfc8174>.
1271 [RFC8264] Saint-Andre, P. and M. Blanchet, "PRECIS Framework:
1272 Preparation, Enforcement, and Comparison of
1273 Internationalized Strings in Application Protocols",
1274 RFC 8264, DOI 10.17487/RFC8264, October 2017,
1275 <https://www.rfc-editor.org/info/rfc8264>.
1277 [UAX11] Unicode Standard Annex #11, "East Asian Width", edited by
1278 Ken Lunde. An integral part of The Unicode Standard,
1279 <http://unicode.org/reports/tr11/>.
1281 [Unicode] The Unicode Consortium, "The Unicode Standard",
1282 <http://www.unicode.org/versions/latest/>.
1290Saint-Andre & Melnikov Standards Track [Page 23]
1292RFC 8265 PRECIS: Usernames and Passwords October 2017
12959.2. Informative References
1297 [Err1812] RFC Errata, Erratum ID 1812, RFC 4013,
1298 <https://www.rfc-editor.org/errata/eid1812>.
1300 [RFC20] Cerf, V., "ASCII format for network interchange", STD 80,
1301 RFC 20, DOI 10.17487/RFC0020, October 1969,
1302 <https://www.rfc-editor.org/info/rfc20>.
1304 [RFC3454] Hoffman, P. and M. Blanchet, "Preparation of
1305 Internationalized Strings ("stringprep")", RFC 3454,
1306 DOI 10.17487/RFC3454, December 2002,
1307 <https://www.rfc-editor.org/info/rfc3454>.
1309 [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
1310 4rev1", RFC 3501, DOI 10.17487/RFC3501, March 2003,
1311 <https://www.rfc-editor.org/info/rfc3501>.
1313 [RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource
1314 Identifiers (IRIs)", RFC 3987, DOI 10.17487/RFC3987,
1315 January 2005, <https://www.rfc-editor.org/info/rfc3987>.
1317 [RFC4013] Zeilenga, K., "SASLprep: Stringprep Profile for User Names
1318 and Passwords", RFC 4013, DOI 10.17487/RFC4013, February
1319 2005, <https://www.rfc-editor.org/info/rfc4013>.
1321 [RFC4422] Melnikov, A., Ed. and K. Zeilenga, Ed., "Simple
1322 Authentication and Security Layer (SASL)", RFC 4422,
1323 DOI 10.17487/RFC4422, June 2006,
1324 <https://www.rfc-editor.org/info/rfc4422>.
1326 [RFC4616] Zeilenga, K., Ed., "The PLAIN Simple Authentication and
1327 Security Layer (SASL) Mechanism", RFC 4616,
1328 DOI 10.17487/RFC4616, August 2006,
1329 <https://www.rfc-editor.org/info/rfc4616>.
1331 [RFC5802] Newman, C., Menon-Sen, A., Melnikov, A., and N. Williams,
1332 "Salted Challenge Response Authentication Mechanism
1333 (SCRAM) SASL and GSS-API Mechanisms", RFC 5802,
1334 DOI 10.17487/RFC5802, July 2010,
1335 <https://www.rfc-editor.org/info/rfc5802>.
1337 [RFC5893] Alvestrand, H., Ed. and C. Karp, "Right-to-Left Scripts
1338 for Internationalized Domain Names for Applications
1339 (IDNA)", RFC 5893, DOI 10.17487/RFC5893, August 2010,
1340 <https://www.rfc-editor.org/info/rfc5893>.
1346Saint-Andre & Melnikov Standards Track [Page 24]
1348RFC 8265 PRECIS: Usernames and Passwords October 2017
1351 [RFC6120] Saint-Andre, P., "Extensible Messaging and Presence
1352 Protocol (XMPP): Core", RFC 6120, DOI 10.17487/RFC6120,
1353 March 2011, <https://www.rfc-editor.org/info/rfc6120>.
1355 [RFC6943] Thaler, D., Ed., "Issues in Identifier Comparison for
1356 Security Purposes", RFC 6943, DOI 10.17487/RFC6943, May
1357 2013, <https://www.rfc-editor.org/info/rfc6943>.
1359 [RFC7542] DeKok, A., "The Network Access Identifier", RFC 7542,
1360 DOI 10.17487/RFC7542, May 2015,
1361 <https://www.rfc-editor.org/info/rfc7542>.
1363 [RFC7613] Saint-Andre, P. and A. Melnikov, "Preparation,
1364 Enforcement, and Comparison of Internationalized Strings
1365 Representing Usernames and Passwords", RFC 7613,
1366 DOI 10.17487/RFC7613, August 2015,
1367 <https://www.rfc-editor.org/info/rfc7613>.
1369 [RFC7616] Shekh-Yusef, R., Ed., Ahrens, D., and S. Bremer, "HTTP
1370 Digest Access Authentication", RFC 7616,
1371 DOI 10.17487/RFC7616, September 2015,
1372 <https://www.rfc-editor.org/info/rfc7616>.
1374 [RFC7617] Reschke, J., "The 'Basic' HTTP Authentication Scheme",
1375 RFC 7617, DOI 10.17487/RFC7617, September 2015,
1376 <https://www.rfc-editor.org/info/rfc7617>.
1378 [RFC7622] Saint-Andre, P., "Extensible Messaging and Presence
1379 Protocol (XMPP): Address Format", RFC 7622,
1380 DOI 10.17487/RFC7622, September 2015,
1381 <https://www.rfc-editor.org/info/rfc7622>.
1383 [RFC8266] Saint-Andre, P., "Preparation, Enforcement, and Comparison
1384 of Internationalized Strings Representing Nicknames",
1385 RFC 8266, DOI 10.17487/RFC8266, October 2017,
1386 <https://www.rfc-editor.org/info/rfc8266>.
1388 [UTS39] Unicode Technical Standard #39, "Unicode Security
1389 Mechanisms", edited by Mark Davis and Michel Suignard,
1390 <http://unicode.org/reports/tr39/>.
1392Appendix A. Changes from RFC 7613
1394 The following changes were made from [RFC7613].
1396 o Corrected the order of operations for the UsernameCaseMapped
1397 profile to ensure consistency with [RFC8264].
1402Saint-Andre & Melnikov Standards Track [Page 25]
1404RFC 8265 PRECIS: Usernames and Passwords October 2017
1407 o In accordance with working group discussions and updates to
1408 [RFC8264], removed the use of the Unicode toCaseFold() operation
1409 in favor of the Unicode toLowerCase() operation.
1411 o Modified the presentation (but not the content) of the rules.
1413 o Removed UTF-8 as a mandatory encoding, because that is a matter
1414 for the application.
1416 o Clarified several editorial matters.
1418 o Updated references.
1420 See [RFC7613] for a description of the differences from [RFC4013].
1424 Thanks to Christian Schudt and Sam Whited for their bug reports and
1427 See [RFC7613] for acknowledgements related to the specification that
1428 this document supersedes.
1436 United States of America
1438 Phone: +1 720 256 6756
1439 Email: stpeter@jabber.org
1440 URI: https://www.jabber.org/
1445 5 Castle Business Village
1447 Hampton, Middlesex TW12 2BX
1450 Email: Alexey.Melnikov@isode.com
1458Saint-Andre & Melnikov Standards Track [Page 26]