]> Viagenie

246 Aberdeen Quebec QC G1R 2E1 Canada Marc.Blanchet@viagenie.ca http://viagenie.ca

Dyn, Inc.

150 Dow St Manchester NH 03101 U.S.A. asullivan@dyn.com

example If a protocol expects to compare two strings and is prepared only for those strings to be ASCII, then using Unicode code points in those strings requires they be prepared somehow. Internationalizing Domain Names in Applications (here called IDNA2003) defined and used Stringprep and Nameprep. Other protocols subsequently defined Stringprep profiles. A new approach different from Stringprep and Nameprep is used for a revision of IDNA2003 (called IDNA2008). Other Stringprep profiles need to be similarly updated, or a replacement of Stringprep needs to be designed. This document outlines the issues to be faced by those designing a Stringprep replacement.

Internationalizing Domain Names in Applications (here called IDNA2003) and describes a mechanism for encoding Unicode labels that make up the Internationalized Domain Names (IDNs) as standard DNS labels. The labels were processed using a method called Nameprep and Punycode . That method was specific to IDNA2003 but is generalized as Stringprep . The general mechanism is used by other protocols with similar needs but with different constraints than IDNA2003. Stringprep defines a framework within which protocols define their Stringprep profiles. Some known IETF specifications using Stringprep are listed below: The Nameprep profile for use in Internationalized Domain Names (IDNs); The Inter-Asterisk eXchange (IAX) using Nameprep ; NFSv4 and NFSv4.1 ; The Internet Small Computer System Interface (iSCSI) profile for use in iSCSI names; The Extensible Authentication Protocol (EAP) ; The Nodeprep and Resourceprep profiles (which was obsoleted by ) for use in the Extensible Messaging and Presence Protocol (XMPP), and the XMPP to Common Presence and Instant Messaging (CPIM) mapping (the latter of these relies on the former); The Internationalized Resource Identifier (IRI) and URI in XMPP ; The Policy MIB profile for use in the Simple Network Management Protocol (SNMP); Transport Layer Security (TLS) ; The Lightweight Directory Access Protocol (LDAP) profile for use with LDAP and its authentication methods ; PKIX subject identification using LDAPprep ; PKIX Certificate Revocation List (CRL) using LDAPprep ; The Simple Authentication and Security Layer (SASL) and SASLprep profile for use in SASL; Plain SASL using SASLprep ; SMTP Auth using SASLprep ; The Post Office Protocol (POP3) Auth using SASLprep ; TLS Secure Remote Password (SRP) using SASLprep ; SASL Salted Challenge Response Authentication Mechanism (SCRAM) using SASLprep ; Remote management of Sieve using SASLprep ; The Network News Transfer Protocol (NNTP) using SASLprep ; IMAP4 using SASLprep ; The trace profile for use with the SASL ANONYMOUS mechanism; Internet Application Protocol Collation Registry ; The unicode-casemap Unicode Collation . However, a review (see ) of these protocol specifications found that they are very similar and can be grouped into a short number of classes. Moreover, many reuse the same Stringprep profile, such as the SASL one. IDNA2003 was replaced because of some limitations described in . The new IDN specification, called IDNA2008 , , , was designed based on the considerations found in . One of the effects of IDNA2008 is that Nameprep and Stringprep are not used at all. Instead, an algorithm based on Unicode properties of code points is defined. That algorithm generates a stable and complete table of the supported Unicode code points for each Unicode version. This algorithm uses an inclusion-based approach, instead of the exclusion-based approach of Stringprep/Nameprep. That is, IDNA2003 created an explicit list of excluded or mapped-away characters; anything in Unicode 3.2 that was not so listed could be assumed to be allowed under the protocol. IDNA2008 begins instead from the assumption that code points are disallowed and then relies on Unicode properties to derive whether a given code point actually is allowed in the protocol. This document lists the shortcomings and issues found by protocols listed above that defined Stringprep profiles. It also lists the requirements for any potential replacement of Stringprep.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in . This document uses various internationalization terms, which are defined and discussed in . Additionally, this document defines the following keyword: PRECIS: Preparation and Comparison of Internationalized Strings

A single Unicode code point in this memo is denoted by "U+" followed by four to six hexadecimal digits, as used in , Appendix A.

During IETF 77 (March 2010), a BOF discussed the current state of the protocols that have defined Stringprep profiles . The main conclusions from that discussion were as follows: Stringprep is bound to Version 3.2 of Unicode. Stringprep has not been updated to new versions of Unicode. Therefore, the protocols using Stringprep are stuck at Unicode 3.2, and their specifications need to be updated to support new versions of Unicode. The protocols would like to not be bound to a specific version of Unicode, but rather have better Unicode version agility in the way of IDNA2008. This is important partly because it is usually impossible for an application to require Unicode 3.2; the application gets whatever version of Unicode is available on the host. The protocols require better bidirectional support (bidi) than currently offered by Stringprep. If the protocols are updated to use a new version of Stringprep or another framework, then backward compatibility is an important requirement. For example, Stringprep normalization is based on and profiles may use Unicode Normalization Form KC (NFKC) , while IDNA2008 mostly uses Unicode Normalization Form C (NFC) . Identifiers are passed between protocols. For example, the same username string of code points may be passed between SASL, XMPP, LDAP, and EAP. Therefore, a common set of rules or classes of strings are preferred over specific rules for each protocol. Without real planning in advance, many Stringprep profiles reuse other profiles, so this goal was accomplished by accident with Stringprep. Protocols that use Stringprep profiles use strings for different purposes: XMPP uses a different Stringprep profile for each part of the XMPP address Jabber Identifier (JID): a localpart, which is similar to a username and used for authentication; a domainpart, which is a domain name; and a resourcepart, which is less restrictive than the localpart. iSCSI uses a Stringprep profile for the names of protocol participants (called initiators and targets). The iSCSI Qualified Name (IQN) format of iSCSI names contains a reversed DNS domain name. SASL and LDAP use a Stringprep profile for usernames. LDAP uses a set of Stringprep profiles. The apparent judgement of the BOF attendees was that it would be highly desirable to have a replacement of Stringprep, with similar characteristics to IDNA2008. That replacement should be defined so that the protocols could use internationalized strings without a lot of specialized internationalization work, since internationalization expertise is not available in the respective protocols or working groups. Accordingly, the IESG formed the PRECIS working group to undertake the task. Notwithstanding the desire evident in and the chartering of a working group, IDNA2008 may be a poor model for what other protocols ought to do, because it is designed to support an old protocol that is designed to operate on the scale of the entire Internet. Moreover, IDNA2008 is intended to be deployed without any change to the base DNS protocol. Other protocols may aim at deployment in more local environments, or may have protocol version negotiation built in.

This section provides an overview of major topics that a Stringprep replacement needs to address. The headings correspond roughly with categories under which known Stringprep-using protocol RFCs have been evaluated. For the details of those evaluations, see .

Following , it is possible to organize identifiers into three classes in respect of how they may be compared with one another: Identifiers that can be compared byte-by-byte for equality. Identifiers that have a well-defined comparison algorithm on which all parties agree. Identifiers that have no single comparison algorithm on which all parties agree. Definite Identifiers include cases like the comparison of Unicode code points in different encodings: they do not match byte for byte but can all be converted to a single encoding which then does match byte for byte. Indefinite Identifiers are sometimes algorithmically comparable by well-specified subsets of parties. For more discussion of these categories, see . The section on treating the existing known cases, , uses the categories above.

The three classes of comparison style outlined in may have different effects when applied. It is necessary to evaluate the effects if a comparison results in a false positive or a false negative, especially in terms of the consequences to security and usability.

This section outlines a range of issues having to do with characters in the target protocols, the ways in which IDNA2008 might be a good analogy to other protocols, and ways in which it might be a poor one.

In IDNA2003, labels are always mapped to lowercase before the Punycode transformation. In IDNA2008, there is no mapping at all: input is either a valid U-label or it is not. At the same time, uppercase characters are by definition not valid U-labels, because they fall into the Unstable category (category B) of . If there are protocols that require case be preserved, then the analogy with IDNA2008 will break down. Accordingly, existing protocols are to be evaluated according to the following criteria: Does the protocol use case folding? For all blocks of code points or just for certain subsets? Is the system or protocol case-sensitive? Does the system or protocol preserve case?

Stringprep profiles may use normalization. If they do, they use NFKC (most profiles do). It is not clear that NFKC is the right normalization to use in all cases. In , there is the following observation regarding Normalization Forms KC and KD: "It is best to think of these Normalization Forms as being like uppercase or lowercase mappings: useful in certain contexts for identifying core meanings, but also performing modifications to the text that may not always be appropriate." In general, it can be said that NFKC is more aggressive about finding matches between code points than NFC. For things like the spelling of users' names, NFKC may not be the best form to use. At the same time, one of the nice things about NFKC is that it deals with the width of characters that are otherwise similar, by canonicalizing half-width to full-width. This mapping step can be crucial in practice. A replacement for Stringprep depends on analyzing the different use profiles and considering whether NFKC or NFC is a better normalization for each profile. For the purposes of evaluating an existing example of Stringprep use, it is helpful to know whether it uses no normalization, NFKC, or NFC.

Along with the case mapping issues raised in , there is the question of whether some characters are mapped either to other characters or to nothing during Stringprep. , Section 3, outlines a number of characters that are mapped to nothing, and also permits Stringprep profiles to define their own mappings.

Along with case folding and other character mappings, many protocols have characters that are simply disallowed. For example, control characters and special characters such as "@" or "/" may be prohibited in a protocol. One of the primary changes of IDNA2008 is in the way it approaches Unicode code points, using the new inclusion-based approach (see ). Because of the default assumption in IDNA2008 that a code point is not allowed by the protocol, it has more than one class of "allowed by the protocol"; this is unlike IDNA2003. While some code points are disallowed outright, some are allowed only in certain contexts. The reasons for the context-dependent rules have to do with the way some characters are used. For instance, the ZERO WIDTH JOINER and ZERO WIDTH NON-JOINER (ZWJ, U+200D and ZWNJ, U+200C) are allowed with contextual rules because they are required in some circumstances, yet are considered punctuation by Unicode and would therefore be DISALLOWED under the usual IDNA2008 derivation rules. The goal of IDNA2008 is to provide the widest repertoire of code points possible and consistent with the traditional DNS "LDH" (letters, digits, hyphen) rule (see ), trusting to the operators of individual zones to make sensible (and usually more restrictive) policies for their zones.

IDNA2008 has a special problem with delimiters, because the delimiter "character" in the DNS wire format is not really part of the data. In DNS, labels are not separated exactly; instead, a label carries with it an indicator that says how long the label is. When the label is displayed in presentation format as part of a fully qualified domain name, the label separator FULL STOP, U+002E (.) is used to break up the labels. But because that label separator does not travel with the wire format of the domain name, there is no way to encode a different, "internationalized" separator in IDNA2008. Other protocols may include characters with similar special meaning within the protocol. Common characters for these purposes include FULL STOP, U+002E (.); COMMERCIAL AT, U+0040 (@); HYPHEN-MINUS, U+002D (-); SOLIDUS, U+002F (/); and LOW LINE, U+005F (_). The mere inclusion of such a character in the protocol is not enough for it to be considered similar to another protocol using the same character; instead, handling of the character must be taken into consideration as well. An important issue to tackle here is whether it is valuable to map to or from these special characters as part of the Stringprep replacement. In some locales, the analogue to FULL STOP, U+002E is some other character, and users may expect to be able to substitute their normal stop for FULL STOP, U+002E. At the same time, there are predictability arguments in favor of treating identifiers with FULL STOP, U+002E in them just the way they are treated under IDNA2008.

Homoglyphs are similarly (or identically) rendered glyphs of different code points. For DNS names, homoglyphs may enable phishing. If a protocol requires some visual comparison by end-users, then the issue of homoglyphs is to be considered. In the DNS context, these issues are documented in and . However, IDNA2008 does not have a mechanism to deal with them, trusting DNS zone operators to enact sensible policies for the subset of Unicode they wish to support, given their user community. A similar policy/protocol split may not be desirable in every protocol.

Some protocol elements are provided by users, and others are not. Those that are not may presumably be subject to greater restrictions, whereas those that users provide likely need to permit the broadest range of code points. The following questions are helpful: Do users input the strings directly? If so, how? (keyboard, stylus, voice, copy-paste, etc.) Where do we place the dividing line between user interface and protocol? (see )

Just as only some protocol elements are expected to be entered directly by users, only some protocol elements are intended to be consumed directly by users. It is important to know how users are expected to be able to consume the protocol elements, because different environments present different challenges. An element that is only ever delivered as part of a vCard remains in machine-readable format, so the problem of visual confusion is not a great one. Is the protocol element published as part of a vCard, a web directory, on a business card, or on "the side of a bus"? Do users use the protocol element as an identifier (which means that they might enter it again in some other context)? (See also .)

Some strings are useful as part of the protocol but are not used as input to other operations (for instance, purely informative or descriptive text). Other strings are used directly as input to other operations (such as cryptographic hash functions), or are used together with other strings to (such as concatenating a string with some others to form a unique identifier).

Strings often have a similar function in different protocols. For instance, many different protocols contain user identifiers or passwords. A single profile for all such uses might be desirable. Often, a string in a protocol is effectively a protocol element from another protocol. For instance, different systems might use the same credentials database for authentication.

A Stringprep replacement that does anything more than just update Stringprep to the latest version of Unicode will probably entail some changes. It is important to identify the willingness of the protocol-using community to accept backwards-incompatible changes. By the same token, it is important to evaluate the desire of the community for features not available under Stringprep.

IDNA2008 uses an algorithm to derive the validity of a Unicode code point for use under IDNA2008. It does this by using the properties of each code point to test its validity. This approach depends crucially on the idea that code points, once valid for a protocol profile, will not later be made invalid. That is not a guarantee currently provided by Unicode. Properties of code points may change between versions of Unicode. Rarely, such a change could cause a given code point to become invalid under a protocol profile, even though the code point would be valid with an earlier version of Unicode. This is not merely a theoretical possibility, because it has occurred . Accordingly, as in IDNA2008, a Stringprep replacement that intends to be Unicode version agnostic will need to work out a mechanism to address cases where incompatible changes occur because of new Unicode versions.

The above suggests the following guidance: A Stringprep replacement should be defined. The replacement should take an approach similar to IDNA2008 (e.g., by using properties of code points instead of whitelisting of code points), in that it enables better Unicode agility. Protocols share similar characteristics of strings. Therefore, defining internationalization preparation algorithms for the smallest set of string classes may be sufficient for most cases, providing coherence among a set of related protocols or protocols where identifiers are exchanged. The sets of string classes need to be evaluated according to the considerations that make up the headings in It is reasonable to limit scope to Unicode code points and rule the mapping of data from other character encodings outside the scope of this effort. The replacement ought to at least provide guidance to applications using the replacement on how to handle protocol incompatibilities resulting from changes to Unicode. In an ideal world, the Stringprep replacement would handle the changes automatically, but it appears that such automatic handling would require magic and cannot be expected. Compatibility within each protocol between a technique that is Stringprep-based and the technique's replacement has to be considered very carefully. Existing deployments already depend on Stringprep profiles. Therefore, a replacement must consider the effects of any new strategy on existing deployments. By way of comparison, it is worth noting that some characters were acceptable in IDNA labels under IDNA2003, but are not protocol-valid under IDNA2008 (and conversely); disagreement about what to do during the transition has resulted in different approaches to mapping. Different implementers may make different decisions about what to do in such cases; this could have interoperability effects. It is necessary to trade better support for different linguistic environments against the potential side effects of backward incompatibility.

This document merely states what problems are to be solved and does not define a protocol. There are undoubtedly security implications of the particular results that will come from the work to be completed. Moreover, the Stringprep Security Considerations Section applies. See also the analysis in the subsections of , below.

This document is the product of the PRECIS IETF Working Group, and participants in that working group were helpful in addressing issues with the text. Specific contributions came from David Black, Alan DeKok, Simon Josefsson, Bill McQuillan, Alexey Melnikov, Peter Saint-Andre, Dave Thaler, and Yoshiro Yoneya. Dave Thaler provided the "buckets" insight in , central to the organization of the problem. Evaluations of Stringprep profiles that are included in were done by David Black, Alexey Melnikov, Peter Saint-Andre, and Dave Thaler.

&rfc2119; &rfc6120; Identifiers such as hostnames, URIs, and email addresses are often used in security contexts to identify security principals and resources. In such contexts, an identifier supplied via some protocol is often compared against some policy to make security decisions such as whether the principal may access the resource, what level of authentication or encryption is required, etc. If the parties involved in a security decision use different algorithms to compare identifiers, then failure scenarios ranging from denial of service to elevation of privilege can result. This document describes a framework for preparing Unicode text strings in order to increase the likelihood that string input and string comparison work in ways that make sense for typical users throughout the world. The stringprep protocol is useful for protocol identifier values, company and personal names, internationalized domain names, and other text strings. This document does not specify how protocols should prepare text strings. Protocols must create profiles of stringprep in order to fully specify the processing options. [STANDARDS-TRACK] Until now, there has been no standard method for domain names to use characters outside the ASCII repertoire. This document defines internationalized domain names (IDNs) and a mechanism called Internationalizing Domain Names in Applications (IDNA) for handling them in a standard fashion. IDNs use characters drawn from a large repertoire (Unicode), but IDNA allows the non-ASCII characters to be represented using only the ASCII characters already allowed in so-called host names today. This backward-compatible representation is required in existing protocols like DNS, so that IDNs can be introduced with no changes to the existing infrastructure. IDNA is only meant for processing domain names, not free text. [STANDARDS-TRACK] This document describes how to prepare internationalized domain name (IDN) labels in order to increase the likelihood that name input and name comparison work in ways that make sense for typical users throughout the world. This profile of the stringprep protocol is used as part of a suite of on-the-wire protocols for internationalizing the Domain Name System (DNS). [STANDARDS-TRACK] Punycode is a simple and efficient transfer encoding syntax designed for use with Internationalized Domain Names in Applications (IDNA). It uniquely and reversibly transforms a Unicode string into an ASCII string. ASCII characters in the Unicode string are represented literally, and non-ASCII characters are represented by ASCII characters that are allowed in host name labels (letters, digits, and hyphens). This document defines a general algorithm called Bootstring that allows a string of basic code points to uniquely represent any string of code points drawn from a larger set. Punycode is an instance of Bootstring that uses particular parameter values specified by this document, appropriate for IDNA. [STANDARDS-TRACK] The Network File System (NFS) version 4 is a distributed filesystem protocol which owes heritage to NFS protocol version 2, RFC 1094, and version 3, RFC 1813. Unlike earlier versions, the NFS version 4 protocol supports traditional file access while integrating support for file locking and the mount protocol. In addition, support for strong security (and its negotiation), compound operations, client caching, and internationalization have been added. Of course, attention has been applied to making NFS version 4 operate well in an Internet environment. This document replaces RFC 3010 as the definition of the NFS version 4 protocol. [STANDARDS-TRACK] This document describes how to prepare internationalized iSCSI names to increase the likelihood that name input and comparison work in ways that make sense for typical users throughout the world. The Internet Small Computer Systems Interface (iSCSI) protocol provides a way for hosts to access SCSI devices over an IP network. The iSCSI end-points, called initiators and targets, each have a globally-unique name that must be transcribable, as well as easily compared. [STANDARDS-TRACK] This document defines the Extensible Authentication Protocol (EAP), an authentication framework which supports multiple authentication methods. EAP typically runs directly over data link layers such as Point-to-Point Protocol (PPP) or IEEE 802, without requiring IP. EAP provides its own support for duplicate elimination and retransmission, but is reliant on lower layer ordering guarantees. Fragmentation is not supported within EAP itself; however, individual EAP methods may support this. This document obsoletes RFC 2284. A summary of the changes between this document and RFC 2284 is available in Appendix A. [STANDARDS-TRACK] Jabber Software Foundation

stpeter@jabber.org

Applications XMPP Working Group RFC Request for Comments I-D Internet-Draft XMPP Extensible Messaging and Presence Protocol Jabber IM Instant Messaging Presence XML Extensible Markup Language This memo defines the core features of the Extensible Messaging and Presence Protocol (XMPP), a protocol for streaming Extensible Markup Language (XML) elements in order to exchange structured information in close to real time between any two network endpoints. While XMPP provides a generalized, extensible framework for exchanging XML data, it is used mainly for the purpose of building instant messaging and presence applications that meet the requirements of RFC 2779. Jabber Software Foundation

stpeter@jabber.org

Applications XMPP Working Group RFC Request for Comments I-D Internet-Draft XMPP Extensible Messaging and Presence Protocol Jabber IM Instant Messaging Presence CPIM Common Presence and Instant Messaging XML Extensible Markup Language This memo describes a mapping between the Extensible Messaging and Presence Protocol (XMPP) and the Common Presence and Instant Messaging (CPIM) specifications. This memo defines a portion of the Management Information Base (MIB) for use with network management protocols in TCP/IP-based internets. In particular, this MIB defines objects that enable policy-based monitoring and management of Simple Network Management Protocol (SNMP) infrastructures, a scripting language, and a script execution environment. [STANDARDS-TRACK] This document describes how to prepare Unicode strings representing user names and passwords for comparison. The document defines the "SASLprep" profile of the "stringprep" algorithm to be used for both user names and passwords. This profile is intended to be used by Simple Authentication and Security Layer (SASL) mechanisms (such as PLAIN, CRAM-MD5, and DIGEST-MD5), as well as other protocols exchanging simple user names and/or passwords. [STANDARDS-TRACK] This document specifies three sets of new ciphersuites for the Transport Layer Security (TLS) protocol to support authentication based on pre-shared keys (PSKs). These pre-shared keys are symmetric keys, shared in advance among the communicating parties. The first set of ciphersuites uses only symmetric key operations for authentication. The second set uses a Diffie-Hellman exchange authenticated with a pre-shared key, and the third set combines public key authentication of the server with pre-shared key authentication of the client. [STANDARDS-TRACK] The Access Control List (ACL) extension (RFC 2086) of the Internet Message Access Protocol (IMAP) permits mailbox access control lists to be retrieved and manipulated through the IMAP protocol.</t><t> This document is a revision of RFC 2086. It defines several new access control rights and clarifies which rights are required for different IMAP commands. [STANDARDS-TRACK] The Simple Authentication and Security Layer (SASL) is a framework for providing authentication and data security services in connection-oriented protocols via replaceable mechanisms. It provides a structured interface between protocols and mechanisms. The resulting framework allows new protocols to reuse existing mechanisms and allows old protocols to make use of new mechanisms. The framework also provides a protocol for securing subsequent protocol exchanges within a data security layer.</t><t> This document describes how a SASL mechanism is structured, describes how protocols include support for SASL, and defines the protocol for carrying a data security layer over a connection. In addition, this document defines one SASL mechanism, the EXTERNAL mechanism.</t><t> This document obsoletes RFC 2222. [STANDARDS-TRACK] On the Internet, it is common practice to permit anonymous access to various services. Traditionally, this has been done with a plain-text password mechanism using "anonymous" as the user name and using optional trace information, such as an email address, as the password. As plain-text login commands are not permitted in new IETF protocols, a new way to provide anonymous login is needed within the context of the Simple Authentication and Security Layer (SASL) framework. [STANDARDS-TRACK] This document describes the protocol elements, along with their semantics and encodings, of the Lightweight Directory Access Protocol (LDAP). LDAP provides access to distributed directory services that act in accordance with X.500 data and service models. These protocol elements are based on those described in the X.500 Directory Access Protocol (DAP). [STANDARDS-TRACK] This document describes authentication methods and security mechanisms of the Lightweight Directory Access Protocol (LDAP). This document details establishment of Transport Layer Security (TLS) using the StartTLS operation.</t><t> This document details the simple Bind authentication method including anonymous, unauthenticated, and name/password mechanisms and the Simple Authentication and Security Layer (SASL) Bind authentication method including the EXTERNAL mechanism.</t><t> This document discusses various authentication and authorization states through which a session to an LDAP server may pass and the actions that trigger these state changes.</t><t> This document, together with other documents in the LDAP Technical Specification (see Section 1 of the specification's road map), obsoletes RFC 2251, RFC 2829, and RFC 2830. [STANDARDS-TRACK] The previous Lightweight Directory Access Protocol (LDAP) technical specifications did not precisely define how character string matching is to be performed. This led to a number of usability and interoperability problems. This document defines string preparation algorithms for character-based matching rules defined for use in LDAP. [STANDARDS-TRACK] This document defines a simple clear-text user/password Simple Authentication and Security Layer (SASL) mechanism called the PLAIN mechanism. The PLAIN mechanism is intended to be used, in combination with data confidentiality services provided by a lower layer, in protocols that lack a simple password authentication command. [STANDARDS-TRACK] This document defines an extension to the Network News Transfer Protocol (NNTP) that allows a client to indicate an authentication mechanism to the server, to perform an authentication protocol exchange, and optionally to negotiate a security layer for subsequent protocol interactions during the remainder of an NNTP session.</t><t> This document updates and formalizes the AUTHINFO USER/PASS authentication method specified in RFC 2980 and deprecates the AUTHINFO SIMPLE and AUTHINFO GENERIC authentication methods. Additionally, this document defines a profile of the Simple Authentication and Security Layer (SASL) for NNTP. [STANDARDS-TRACK] This document defines the Subject Identification Method (SIM) for including a privacy-sensitive identifier in the subjectAltName extension of a certificate.</t><t> The SIM is an optional feature that may be used by relying parties to determine whether the subject of a particular certificate is also the person corresponding to a particular sensitive identifier. [STANDARDS-TRACK] IAB This note describes issues raised by the deployment and use of Internationalized Domain Names. It describes problems both at the time of registration and for use of those names in the DNS. It recommends that IETF should update the RFCs relating to IDNs and a framework to be followed in doing so, as well as summarizing and identifying some work that is required outside the IETF. In particular, it proposes that some changes be investigated for the Internationalizing Domain Names in Applications (IDNA) standard and its supporting tables, based on experience gained since those standards were completed. This memo provides information for the Internet community. Many Internet application protocols include string-based lookup, searching, or sorting operations. However, the problem space for searching and sorting international strings is large, not fully explored, and is outside the area of expertise for the Internet Engineering Task Force (IETF). Rather than attempt to solve such a large problem, this specification creates an abstraction framework so that application protocols can precisely identify a comparison function, and the repertoire of comparison functions can be extended in the future. [STANDARDS-TRACK] This document defines a Simple Mail Transport Protocol (SMTP) extension whereby an SMTP client may indicate an authentication mechanism to the server, perform an authentication protocol exchange, and optionally negotiate a security layer for subsequent protocol interactions during this session. This extension includes a profile of the Simple Authentication and Security Layer (SASL) for SMTP.</t><t> This document obsoletes RFC 2554. [STANDARDS-TRACK] This document defines a profile of the Simple Authentication and Security Layer (SASL) for the Post Office Protocol (POP3). This extension allows a POP3 client to indicate an authentication mechanism to the server, perform an authentication protocol exchange, and optionally negotiate a security layer for subsequent protocol interactions during this session.</t><t> This document seeks to consolidate the information related to POP3 AUTH into a single document. To this end, this document obsoletes and replaces RFC 1734, and updates the information contained in Section 6.3 of RFC 2449. [STANDARDS-TRACK] This document describes "i;unicode-casemap", a simple case-insensitive collation for Unicode strings. It provides equality, substring, and ordering operations. [STANDARDS-TRACK] This memo presents a technique for using the Secure Remote Password protocol as an authentication method for the Transport Layer Security protocol. This memo provides information for the Internet community. This document defines the use of Internationalized Resource Identifiers (IRIs) and Uniform Resource Identifiers (URIs) in identifying or interacting with entities that can communicate via the Extensible Messaging and Presence Protocol (XMPP). [STANDARDS-TRACK] This memo profiles the X.509 v3 certificate and X.509 v2 certificate revocation list (CRL) for use in the Internet. An overview of this approach and model is provided as an introduction. The X.509 v3 certificate format is described in detail, with additional information regarding the format and semantics of Internet name forms. Standard certificate extensions are described and two Internet-specific extensions are defined. A set of required certificate extensions is specified. The X.509 v2 CRL format is described in detail along with standard and Internet-specific extensions. An algorithm for X.509 certification path validation is described. An ASN.1 module and examples are provided in the appendices. [STANDARDS-TRACK] This document describes IAX, the Inter-Asterisk eXchange protocol, an application-layer control and media protocol for creating, modifying, and terminating multimedia sessions over Internet Protocol (IP) networks. IAX was developed by the open source community for the Asterisk Private Branch Exchange (PBX) and is targeted primarily at Voice over Internet Protocol (VoIP) call control, but it can be used with streaming video or any other type of multimedia.</t><t> IAX is an "all in one" protocol for handling multimedia in IP networks. It combines both control and media services in the same protocol. In addition, IAX uses a single UDP data stream on a static port greatly simplifying Network Address Translation (NAT) gateway traversal, eliminating the need for other protocols to work around NAT, and simplifying network and firewall management. IAX employs a compact encoding that decreases bandwidth usage and is well suited for Internet telephony service. In addition, its open nature permits new payload type additions needed to support additional services. This document is not an Internet Standards Track specification; it is published for informational purposes. This document describes the Network File System (NFS) version 4 minor version 1, including features retained from the base protocol (NFS version 4 minor version 0, which is specified in RFC 3530) and protocol extensions made subsequently. Major extensions introduced in NFS version 4 minor version 1 include Sessions, Directory Delegations, and parallel NFS (pNFS). NFS version 4 minor version 1 has no dependencies on NFS version 4 minor version 0, and it is considered a separate protocol. Thus, this document neither updates nor obsoletes RFC 3530. NFS minor version 1 is deemed superior to NFS minor version 0 with no loss of functionality, and its use is preferred over version 0. Both NFS minor versions 0 and 1 can be used simultaneously on the same network, between the same client and server. [STANDARDS-TRACK] The secure authentication mechanism most widely deployed and used by Internet application protocols is the transmission of clear-text passwords over a channel protected by Transport Layer Security (TLS). There are some significant security concerns with that mechanism, which could be addressed by the use of a challenge response authentication mechanism protected by TLS. Unfortunately, the challenge response mechanisms presently on the standards track all fail to meet requirements necessary for widespread deployment, and have had success only in limited use.</t><t> This specification describes a family of Simple Authentication and Security Layer (SASL; RFC 4422) authentication mechanisms called the Salted Challenge Response Authentication Mechanism (SCRAM), which addresses the security concerns and meets the deployability requirements. When used in combination with TLS or an equivalent security layer, a mechanism from this family could improve the status quo for application protocol authentication and provide a suitable choice for a mandatory-to-implement mechanism for future application protocol standards. [STANDARDS-TRACK] Sieve scripts allow users to filter incoming email. Message stores are commonly sealed servers so users cannot log into them, yet users must be able to update their scripts on them. This document describes a protocol "ManageSieve" for securely managing Sieve scripts on a remote server. This protocol allows a user to have multiple scripts, and also alerts a user to syntactically flawed scripts. [STANDARDS TRACK] This document is one of a collection that, together, describe the protocol and usage context for a revision of Internationalized Domain Names for Applications (IDNA), superseding the earlier version. It describes the document collection and provides definitions and other material that are common to the set. [STANDARDS-TRACK] This document is the revised protocol definition for Internationalized Domain Names (IDNs). The rationale for changes, the relationship to the older specification, and important terminology are provided in other documents. This document specifies the protocol mechanism, called Internationalized Domain Names in Applications (IDNA), for registering and looking up IDNs in a way that does not require changes to the DNS itself. IDNA is only meant for processing domain names, not free text. [STANDARDS-TRACK] This document specifies rules for deciding whether a code point, considered in isolation or in context, is a candidate for inclusion in an Internationalized Domain Name (IDN).</t><t> It is part of the specification of Internationalizing Domain Names in Applications 2008 (IDNA2008). [STANDARDS-TRACK] The use of right-to-left scripts in Internationalized Domain Names (IDNs) has presented several challenges. This memo provides a new Bidi rule for Internationalized Domain Names for Applications (IDNA) labels, based on the encountered problems with some scripts and some shortcomings in the 2003 IDNA Bidi criterion. [STANDARDS-TRACK] Several years have passed since the original protocol for Internationalized Domain Names (IDNs) was completed and deployed. During that time, a number of issues have arisen, including the need to update the system to deal with newer versions of Unicode. Some of these issues require tuning of the existing protocols and the tables on which they depend. This document provides an overview of a revised system and provides explanatory material for its components. This document is not an Internet Standards Track specification; it is published for informational purposes. In the original version of the Internationalized Domain Names in Applications (IDNA) protocol, any Unicode code points taken from user input were mapped into a set of Unicode code points that "made sense", and then encoded and passed to the domain name system (DNS). The IDNA2008 protocol (described in RFCs 5890, 5891, 5892, and 5893) presumes that the input to the protocol comes from a set of "permitted" code points, which it then encodes and passes to the DNS, but does not specify what to do with the result of user input. This document describes the actions that can be taken by an implementation between receiving user input and passing permitted code points to the new IDNA protocol. This document is not an Internet Standards Track specification; it is published for informational purposes. This document provides a list of terms used in the IETF when discussing internationalization. The purpose is to help frame discussions of internationalization in the various areas of the IETF and to help introduce the main concepts to IETF participants. This memo documents an Internet Best Current Practice. This memo documents IETF consensus for Internationalized Domain Names for Applications (IDNA) derived character properties related to the three code points, existing in Unicode 5.2, that changed property values when version 6.0 was released. The consensus is that no update is needed to RFC 5892 based on the changes made in Unicode 6.0. [STANDARDS-TRACK] The Unicode Consortium. The Unicode Standard, Version 6.1, defined by:

SRI International SRI International SRI International

A number of the known cases of Stringprep use were evaluated during the preparation of this document. The known cases are here described in two ways. The types of identifiers the protocol uses is first called out in the ID type column (from ) using the short forms "a" for Absolute, "d" for Definite, and "i" for Indefinite. Next, there is a column that contains an "i" if the protocol string comes from user input, an "o" if the protocol string becomes user-facing output, "b" if both are true, and "n" if neither is true. RFC IDtype User? 3722 a b 3748 - - 3920 a,d b 4505 a i 4314 a,d b 4954 a,d b 5034 a,d b 5804 a,d b

This section is a summary of evaluation of Stringprep profiles that was done to get a good understanding of the usage of Stringprep. This summary is by no means normative nor the actual evaluations themselves. A template was used for reviewers to get a coherent view of all evaluations.

An iSCSI session consists of an initiator (i.e., host or server that uses storage) communicating with a target (i.e., a storage array or other system that provides storage). Both the iSCSI initiator and target are named by iSCSI names. The iSCSI Stringprep profile is used for iSCSI names. iSCSI initiators and targets (see above). They can also be used to identify SCSI ports (these are software entities in the iSCSI protocol, not hardware ports) and iSCSI logical units (storage volumes), although both are unusual in practice. Generally, a human user (1) configures an automated system (2) that generates the names. Advance configuration of the system is required due to the embedded use of external unique identifier (from the DNS or IEEE). Keyboard and copy-paste are common. Copy-paste is common because iSCSI names are long enough to be problematic for humans to remember, causing use of email, sneaker-net, text files, etc., to avoid mistype mistakes. The iSCSI protocol requires that all internationalization string preparation occur in the user interface. The iSCSI protocol treats iSCSI names as opaque identifiers that are compared byte-by-byte for equality. iSCSI names are generally not checked for correct formatting by the protocol. There are no iSCSI-specific enforcement entities, although the use of unique identifier information in the names relies on DNS registrars and the IEEE Registration Authority. Byte-by-byte. Case folding is required for the code blocks specified in RFC 3454, Table B.2. The overall iSCSI naming system (UI + protocol) is case-insensitive. Potential access to the wrong storage. If the initiator has no access to the wrong storage, an authentication failure is the probable result. If the initiator has access to the wrong storage, the resulting misidentification could result in use of the wrong data and possible corruption of stored data. Denial of authorized storage access. iSCSI names may be used as the authentication identities for storage systems. Comparison problems could result in authentication problems, although note that authentication failure ameliorates some of the false positive cases. NFKC, as specified by RFC 3454. Yes, as specified by Table B.1 in RFC 3454. Only the following characters are allowed: ASCII dash, dot, colon ASCII lowercase letters and digits Unicode lowercase characters as specified by RFC 3454. All other characters are disallowed. None -- iSCSI names are unique to iSCSI. No. Yes. ASCII dot, dash, and colon are used for internal name structure. These are not reserved characters, in that they can occur in the name in locations other than those used for structuring purposes (e.g., only the first occurrence of a colon character is structural, others are not). iSCSI names appear in server and storage system configuration interfaces. They also appear in system logs. Effectively, no. The rarely used port and logical unit names involve concatenation, which effectively extends a unique iSCSI name for a target to uniquely identify something within that target. Good tolerance; the community would prefer that internationalization experts solve internationalization problems. Unicode agility is desired, in principle, as long as nothing significant breaks.

Authorization identity (user identifier) exchanged during SASL authentication: AUTH (SMTP/POP3) or AUTHENTICATE (ManageSieve) command. Used for proxy authorization, e.g., to [lawfully] impersonate a particular user after a privileged authentication. Typically generated by email system administrators using some tools/conventions, sometimes from some backend database. In some setups, human users can register their own usernames (e.g., webmail self-registration). typing or selecting from a list copy and paste voice input in configuration files or on the command line Rules enforced by server / add-on service (e.g., gateway service) on registration of account. "Type 1" (byte-for-byte) or "Type 2" (compare by a common algorithm that everyone agrees on (e.g., normalize and then compare the result byte-by-byte). Most likely case-sensitive. Exact requirements on case-sensitivity/case-preservation depend on a specific implementation, e.g., an implementation might treat all user identifiers as case-insensitive (or case-insensitive for US-ASCII subset only). False positives: an unauthorized user is allowed email service access (login). False negatives: an authorized user is denied email service access. NFKC (as per RFC 4013). (see Section 2 of RFC 4013 for the full list) Non-ASCII spaces are mapped to space, etc. (see Section 2 of RFC 4013 for the full list) Unicode Control characters, etc. Simple username. See Section 2 of RFC 4013 for details on restrictions. Note that some implementations allow spaces in these. While implementations are not required to use a specific format, an authorization identity frequently has the same format as an email address (and Email Address Internationalization (EAI) email address in the future), or as a left hand side of an email address. Note: whatever is recommended for SMTP/POP/ManageSieve authorization identity should also be used for IMAP authorization identities, as IMAP/POP3/SMTP/ManageSieve are frequently implemented together. None Unlikely, but possible. For example, if it is the same as an email address. Sometimes concatenated with other data and then used as input to a cryptographic hash function. Not sure. In RFC 5034, when describing the POP3 AUTH command: The authorization identity generated by the SASL exchange is a simple username, and SHOULD use the SASLprep profile (see [RFC4013]) of the StringPrep algorithm (see [RFC3454]) to prepare these names for matching. If preparation of the authorization identity fails or results in an empty string (unless it was transmitted as the empty string), the server MUST fail the authentication. In RFC 4954, when describing the SMTP AUTH command: The authorization identity generated by this [SASL] exchange is a "simple username" (in the sense defined in [SASLprep]), and both client and server SHOULD (*) use the [SASLprep] profile of the [StringPrep] algorithm to prepare these names for transmission or comparison. If preparation of the authorization identity fails or results in an empty string (unless it was transmitted as the empty string), the server MUST fail the authentication. (*) Note: Future revision of this specification may change this requirement to MUST. Currently, the SHOULD is used in order to avoid breaking the majority of existing implementations. In RFC 5804, when describing the ManageSieve AUTHENTICATE command: The authorization identity generated by this [SASL] exchange is a "simple username" (in the sense defined in [SASLprep]), and both client and server MUST use the [SASLprep] profile of the [StringPrep] algorithm to prepare these names for transmission or comparison. If preparation of the authorization identity fails or results in an empty string (unless it was transmitted as the empty string), the server MUST fail the authentication.

These documents have 2 types of strings (usernames and passwords), so there are two separate templates. "username" parameter to the IMAP LOGIN command, identifiers in IMAP Access Control List (ACL) commands. Note that any valid username is also an IMAP ACL identifier, but IMAP ACL identifiers can include other things like the name of a group of users. Used for authentication (Usernames), or in IMAP Access Control Lists (Usernames or Group names). Typically generated by email system administrators using some tools/conventions, sometimes from some backend database. In some setups, human users can register own usernames (e.g., webmail self-registration). typing or selecting from a list copy and paste voice input in configuration files or on the command line Rules enforced by server / add-on service (e.g., gateway service) on registration of account. "Type 1" (byte-for-byte) or "Type 2" (compare by a common algorithm that everyone agrees on (e.g., normalize and then compare the result byte-by-byte). Most likely case-sensitive. Exact requirements on case-sensitivity/case-preservation depend on a specific implementation, e.g., an implementation might treat all user identifiers as case-insensitive (or case-insensitive for US-ASCII subset only). False positives: an unauthorized user is allowed IMAP access (login), privileges improperly granted (e.g., access to a specific mailbox, ability to manage ACLs for a mailbox). False negatives: an authorized user is denied IMAP access, unable to use granted privileges (e.g., access to a specific mailbox, ability to manage ACLs for a mailbox). NFKC (as per RFC 4013) (see Section 2 of RFC 4013 for the full list) Non-ASCII spaces are mapped to space. (see Section 2 of RFC 4013 for the full list) Unicode Control characters, etc. Simple username. See Section 2 of RFC 4013 for details on restrictions. Note that some implementations allow spaces in these. While IMAP implementations are not required to use a specific format, an IMAP username frequently has the same format as an email address (and EAI email address in the future), or as a left hand side of an email address. Note: whatever is recommended for the IMAP username should also be used for ManageSieve, POP3 and SMTP authorization identities, as IMAP/POP3/SMTP/ManageSieve are frequently implemented together. None. Unlikely, but possible. For example, if it is the same as an email address, access control lists (e.g. in IMAP ACL extension), both when managing membership and listing membership of existing access control lists. Often shows up as mailbox names (under Other Users IMAP namespace). Sometimes concatenated with other data and then used as input to a cryptographic hash function. Not sure. Non-ASCII IMAP usernames are currently prohibited by IMAP (RFC 3501). However, they are allowed when used in IMAP ACL extension.

"Password" parameter to the IMAP LOGIN command. Used for authentication (Passwords). Either generated by email system administrators using some tools/conventions, or specified by the human user. typing or selecting from a list copy and paste voice input in configuration files or on the command line Rules enforced by server / add-on service (e.g., gateway service or backend database) on registration of account. "Type 1" (byte-for-byte). Most likely case-sensitive. False positives: an unauthorized user is allowed IMAP access (login). False negatives: an authorized user is denied IMAP access. NFKC (as per RFC 4013). (see Section 2 of RFC 4013 for the full list) Non-ASCII spaces are mapped to space. (see Section 2 of RFC 4013 for the full list) Unicode Control characters, etc. Currently defined as "simple username" (see Section 2 of RFC 4013 for details on restrictions); however, this is likely to be a different class from usernames. Note that some implementations allow spaces in these. Password in all email related protocols should be treated in the same way. Same passwords are frequently shared with web, IM, and etc. applications. None. Text of email messages (e.g. in "you forgot your password" email messages), web page / directory, side of the bus / in ads -- possible. Sometimes concatenated with other data and then used as input to a cryptographic hash function. Frequently stored as is, or hashed. Not sure. Non-ASCII IMAP passwords are currently prohibited by IMAP (RFC 3501); however, they are likely to be in widespread use. RFC 5738, Section 5 ("UTF8=USER Capability"): If the "UTF8=USER" capability is advertised, that indicates the server accepts UTF-8 user names and passwords and applies SASLprep [RFC4013] to both arguments of the LOGIN command. The server MUST reject UTF-8 that fails to comply with the formal syntax in RFC 3629 [RFC3629] or if it encounters Unicode characters listed in Section 2.3 of SASLprep RFC 4013 [RFC4013]. RFC 4314, Section 3 ("Access control management commands and responses"): Servers, when processing a command that has an identifier as a parameter (i.e., any of SETACL, DELETEACL, and LISTRIGHTS commands), SHOULD first prepare the received identifier using "SASLprep" profile [SASLprep] of the "stringprep" algorithm [Stringprep]. If the preparation of the identifier fails or results in an empty string, the server MUST refuse to perform the command with a BAD response. Note that Section 6 recommends additional identifier's verification steps. RFC 4314, Section 6 ("Security Considerations"): This document relies on [SASLprep] to describe steps required to perform identifier canonicalization (preparation). The preparation algorithm in SASLprep was specifically designed such that its output is canonical, and it is well-formed. However, due to an anomaly [PR29] in the specification of Unicode normalization, canonical equivalence is not guaranteed for a select few character sequences. Identifiers prepared with SASLprep can be stored and returned by an ACL server. The anomaly affects ACL manipulation and evaluation of identifiers containing the selected character sequences. These sequences, however, do not appear in well-formed text. In order to address this problem, an ACL server MAY reject identifiers containing sequences described in [PR29] by sending the tagged BAD response. This is in addition to the requirement to reject identifiers that fail SASLprep preparation as described in Section 3.

RFC 4505 defines a "trace" field: this field is not intended for comparison (only used for logging) No case folding/case-sensitive Yes. Possibly entered in configuration UIs, or on a command line. Can also be stored in configuration files. The value can also be automatically generated by clients (e.g., a fixed string is used, or a user's email address). Keyboard/voice, stylus (pick from a list). Copy-paste - possibly. None. Control characters are disallowed. (See Section 3 of RFC 4505). RFC 4505 says that the trace "should take one of two forms: an Internet email address, or an opaque string that does not contain the '@' (U+0040) character and that can be interpreted by the system administrator of the client's domain". In practice, this is a free-form text, so it belongs to a different class from "email address" or "username". Yes: see above. However, there is no strong need to keep them consistent in the future. No. However, the value can be seen in server logs. False positive: a user can be confused with another user. False negative: two distinct users are treated as the same user. But note that the trace field is not authenticated, so it can be easily falsified. The community would be flexible. No internal structure, but see comments above about frequent use of email addresses. RFC 4505, Section 2 ("The Anonymous Mechanism"): The mechanism consists of a single message from the client to the server. The client may include in this message trace information in the form of a string of [UTF-8]-encoded [Unicode] characters prepared in accordance with [StringPrep] and the "trace" stringprep profile defined in Section 3 of this document. The trace information, which has no semantical value, should take one of two forms: an Internet email address, or an opaque string that does not contain the '@' (U+0040) character and that can be interpreted by the system administrator of the client's domain. For privacy reasons, an Internet email address or other information identifying the user should only be used with permission from the user. RFC 4505, Section 3 ('The "trace" Profile of "Stringprep"'): This section defines the "trace" profile of [StringPrep]. This profile is designed for use with the SASL ANONYMOUS Mechanism. Specifically, the client is to prepare the <message> production in accordance with this profile. The character repertoire of this profile is Unicode 3.2 [Unicode]. No mapping is required by this profile. No Unicode normalization is required by this profile. The list of unassigned code points for this profile is that provided in Appendix A of [StringPrep]. Unassigned code points are not prohibited. Characters from the following tables of [StringPrep] are prohibited:

- C.2.1 (ASCII control characters) - C.2.2 (Non-ASCII control characters) - C.3 (Private use characters) - C.4 (Non-character code points) - C.5 (Surrogate codes) - C.6 (Inappropriate for plain text) - C.8 (Change display properties are deprecated) - C.9 (Tagging characters)

No additional characters are prohibited. This profile requires bidirectional character checking per Section 6 of [StringPrep].

Localpart of JabberID ("JID"), as in: localpart@domainpart/resourcepart Usernames (e.g., stpeter@jabber.org) Chatroom names (e.g., precis@jabber.ietf.org) Publish-subscribe nodes Bot names Typically, end users via an XMPP client Sometimes created in an automated fashion typing copy and paste voice input clicking a URI/IRI Rules enforced by server / add-on service (e.g., chatroom service) on registration of account, creation of room, etc. "Type 2" (common algorithm) Strings are always folded to lowercase Case is not preserved False positives: unable to authenticate at server (or authenticate to wrong account) add wrong person to buddy list join the wrong chatroom improperly grant privileges (e.g., chatroom admin) subscribe to wrong pubsub node interact with wrong bot allow communication with blocked entity False negatives: unable to authenticate unable to add someone to buddy list unable to join desired chatroom unable to use granted privileges (e.g., chatroom admin) unable to subscribe to desired pubsub node unable to interact with desired bot disallow communication with unblocked entity NFKC Spaces are mapped to nothing ",&,',/,:,<,>,@ Often similar to generic username Often similar to localpart of email address Sometimes same as localpart of email address None vCard email signature web page / directory text of message (e.g., in a chatroom) Sometimes concatenated with other data and then used as input to a cryptographic hash function

Resourcepart of JabberID ("JID"), as in: localpart@domainpart/resourcepart Typically free-form text Device / session names (e.g., stpeter@jabber.org/Home) Nicknames (e.g., precis@jabber.ietf.org/StPeter) Often human users via an XMPP client Often generated in an automated fashion by client or server typing copy and paste voice input clicking a URI/IRI Rules enforced by server / add-on service (e.g., chatroom service) on account login, joining a chatroom, etc. "Type 2" (byte-for-byte) Strings are never folded Case is preserved False positives: interact with wrong device (e.g., for file transfer or voice call) interact with wrong chatroom participant improperly grant privileges (e.g., chatroom moderator) allow communication with blocked entity False negatives: unable to choose desired chatroom nickname unable to use granted privileges (e.g., chatroom moderator) disallow communication with unblocked entity NFKC Spaces are mapped to nothing None Basically a free-form identifier None text of message (e.g., in a chatroom) device names often not exposed to human users Sometimes concatenated with other data and then used as input to a cryptographic hash function

RFC 3748, Section 5, references Stringprep, but the WG did not agree with the text (was added by IESG) and there are no known implementations that use Stringprep. The main problem with that text is that the use of strings is a per-method concept, not a generic EAP concept and so RFC 3748 itself does not really use Stringprep, but individual EAP methods could. As such, the answers to the template questions are mostly not applicable, but a few answers are universal across methods. The list of IANA registered EAP methods is at <http://www.iana.org/assignments/eap-numbers/eap-numbers.xml>. n/a (per-method) n/a (per-method) A false positive results in unauthorized network access (and possibly theft of service if some else is billed). A false negative results in lack of authorized network access (no connectivity). n/a (per-method) n/a (per-method) n/a (per-method) n/a (per-method) Although some EAP methods may use a syntax similar to other types of identifiers, EAP mandates that the actual values must not be assumed to be identifiers usable with anything else. n/a (per-method) Identifiers are never human displayed except perhaps as they're typed by a human. n/a (per-method) There is no resistance to change for the base EAP protocol (as noted, the WG didn't want the existing text). However, actual use of Stringprep, if any, within specific EAP methods may have resistance. It is currently unknown whether any EAP methods use Stringprep.