--- 1/draft-ietf-sipping-config-framework-14.txt 2008-02-13 18:12:15.000000000 +0100 +++ 2/draft-ietf-sipping-config-framework-15.txt 2008-02-13 18:12:15.000000000 +0100 @@ -1,19 +1,19 @@ SIPPING D. Petrie Internet-Draft SIPez LLC. Intended status: Standards Track S. Channabasappa, Ed. -Expires: May 21, 2008 CableLabs - November 18, 2007 +Expires: August 16, 2008 CableLabs + February 13, 2008 A Framework for Session Initiation Protocol User Agent Profile Delivery - draft-ietf-sipping-config-framework-14 + draft-ietf-sipping-config-framework-15 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that @@ -24,25 +24,25 @@ and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. - This Internet-Draft will expire on May 21, 2008. + This Internet-Draft will expire on August 16, 2008. Copyright Notice - Copyright (C) The IETF Trust (2007). + Copyright (C) The IETF Trust (2008). Abstract This document specifies a framework to enable configuration of Session Initiation Protocol (SIP) User Agents in SIP deployments. The framework provides a means to deliver profile data that User Agents need to be functional, automatically and with minimal or no User and Administrative intervention. The framework describes how SIP User Agents can discover sources, request profiles and receive notifications related to profile modifications. As part of this @@ -66,58 +66,58 @@ Service Providers . . . . . . . . . . . . . . . . . . . . 12 5. Profile Delivery Framework . . . . . . . . . . . . . . . . . . 14 5.1. Profile delivery stages . . . . . . . . . . . . . . . . . 14 5.1.1. Profile Enrollment . . . . . . . . . . . . . . . . . . 15 5.1.2. Content Retrieval . . . . . . . . . . . . . . . . . . 17 5.1.3. Change Notification . . . . . . . . . . . . . . . . . 17 5.1.4. Enrollment Data and Caching . . . . . . . . . . . . . 18 5.2. Securing Profile Delivery . . . . . . . . . . . . . . . . 21 5.2.1. Securing Profile Enrollment . . . . . . . . . . . . . 22 5.2.2. Securing Content Retrieval . . . . . . . . . . . . . . 23 - 5.2.3. Securing Change Notification . . . . . . . . . . . . . 23 + 5.2.3. Securing Change Notification . . . . . . . . . . . . . 24 5.3. Additional Considerations . . . . . . . . . . . . . . . . 24 - 5.3.1. Identities and Credentials . . . . . . . . . . . . . . 24 - 5.3.2. Profile Enrollment Request Attempt . . . . . . . . . . 25 - 5.3.3. Device Types . . . . . . . . . . . . . . . . . . . . . 29 - 5.3.4. Profile Data . . . . . . . . . . . . . . . . . . . . . 29 - 5.3.5. Profile Data Frameworks . . . . . . . . . . . . . . . 30 - 5.3.6. Additional Profile Types . . . . . . . . . . . . . . . 31 - 5.3.7. Deployment considerations . . . . . . . . . . . . . . 31 - 5.4. Support for NATs . . . . . . . . . . . . . . . . . . . . . 31 - 6. Event Package Definition . . . . . . . . . . . . . . . . . . . 32 - 6.1. Event Package Name . . . . . . . . . . . . . . . . . . . . 32 - 6.2. Event Package Parameters . . . . . . . . . . . . . . . . . 32 - 6.3. SUBSCRIBE Bodies . . . . . . . . . . . . . . . . . . . . . 35 - 6.4. Subscription Duration . . . . . . . . . . . . . . . . . . 35 - 6.5. NOTIFY Bodies . . . . . . . . . . . . . . . . . . . . . . 36 - 6.6. Notifier Processing of SUBSCRIBE Requests . . . . . . . . 36 - 6.7. Notifier Generation of NOTIFY Requests . . . . . . . . . . 36 - 6.8. Subscriber Processing of NOTIFY Requests . . . . . . . . . 37 - 6.9. Handling of Forked Requests . . . . . . . . . . . . . . . 37 - 6.10. Rate of Notifications . . . . . . . . . . . . . . . . . . 38 - 6.11. State Agents . . . . . . . . . . . . . . . . . . . . . . . 38 - 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 - 7.1. Example 1: Device requesting profile . . . . . . . . . . . 38 - 7.2. Example 2: Device obtaining change notification . . . . . 41 - 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 45 - 8.1. SIP Event Package . . . . . . . . . . . . . . . . . . . . 45 - 8.2. Registry of SIP configuration profile types . . . . . . . 45 - 9. Security Considerations . . . . . . . . . . . . . . . . . . . 46 - 9.1. Local-network profile . . . . . . . . . . . . . . . . . . 47 - 9.2. Device profile . . . . . . . . . . . . . . . . . . . . . . 48 - 9.3. User profile . . . . . . . . . . . . . . . . . . . . . . . 50 - 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 50 - 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 51 - 11.1. Normative References . . . . . . . . . . . . . . . . . . . 51 - 11.2. Informative References . . . . . . . . . . . . . . . . . . 52 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 52 - Intellectual Property and Copyright Statements . . . . . . . . . . 54 + 5.3.1. Bootstrapping Identities and Credentials . . . . . . . 24 + 5.3.2. Profile Enrollment Request Attempt . . . . . . . . . . 26 + 5.3.3. Device Types . . . . . . . . . . . . . . . . . . . . . 30 + 5.3.4. Profile Data . . . . . . . . . . . . . . . . . . . . . 30 + 5.3.5. Profile Data Frameworks . . . . . . . . . . . . . . . 31 + 5.3.6. Additional Profile Types . . . . . . . . . . . . . . . 32 + 5.3.7. Deployment considerations . . . . . . . . . . . . . . 32 + 5.4. Support for NATs . . . . . . . . . . . . . . . . . . . . . 33 + 6. Event Package Definition . . . . . . . . . . . . . . . . . . . 33 + 6.1. Event Package Name . . . . . . . . . . . . . . . . . . . . 33 + 6.2. Event Package Parameters . . . . . . . . . . . . . . . . . 33 + 6.3. SUBSCRIBE Bodies . . . . . . . . . . . . . . . . . . . . . 36 + 6.4. Subscription Duration . . . . . . . . . . . . . . . . . . 37 + 6.5. NOTIFY Bodies . . . . . . . . . . . . . . . . . . . . . . 37 + 6.6. Notifier Processing of SUBSCRIBE Requests . . . . . . . . 37 + 6.7. Notifier Generation of NOTIFY Requests . . . . . . . . . . 38 + 6.8. Subscriber Processing of NOTIFY Requests . . . . . . . . . 38 + 6.9. Handling of Forked Requests . . . . . . . . . . . . . . . 39 + 6.10. Rate of Notifications . . . . . . . . . . . . . . . . . . 39 + 6.11. State Agents . . . . . . . . . . . . . . . . . . . . . . . 39 + 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 + 7.1. Example 1: Device requesting profile . . . . . . . . . . . 39 + 7.2. Example 2: Device obtaining change notification . . . . . 42 + 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 46 + 8.1. SIP Event Package . . . . . . . . . . . . . . . . . . . . 46 + 8.2. Registry of SIP configuration profile types . . . . . . . 46 + 9. Security Considerations . . . . . . . . . . . . . . . . . . . 47 + 9.1. Local-network profile . . . . . . . . . . . . . . . . . . 48 + 9.2. Device profile . . . . . . . . . . . . . . . . . . . . . . 49 + 9.3. User profile . . . . . . . . . . . . . . . . . . . . . . . 51 + 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 51 + 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 52 + 11.1. Normative References . . . . . . . . . . . . . . . . . . . 52 + 11.2. Informative References . . . . . . . . . . . . . . . . . . 53 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 54 + Intellectual Property and Copyright Statements . . . . . . . . . . 55 1. Introduction SIP User Agents require configuration data to function properly. Examples include local network, device and user specific information. A configuration data set specific to an entity is termed a profile. For example, device profile contains the configuration data related to a device. The process of providing devices with one or more profiles is termed profile delivery. Ideally, this profile delivery process should be automatic and require minimal or no user @@ -366,28 +366,31 @@ Device Profile: contains configuration data related to a specific device, provided by the Device Provider. User Profile: contains configuration data related to a specific User, as required to reflect that user's preferences and the particular services subscribed to. It is provided by the SIP Service Provider. Additional profile types may also be specified. + PDSs and devices will implement all the three profile types. A device that has not been configured otherwise will try to obtain all - the three profile types, in the order specified by this framework. - The device can be configuration with a different behavior via profile - data previously obtained by the device, other means such as pre- - configuration or manual configuration. The data models associated - with each profile type are out of scope for this document. Follow-on - standardization activities are expected to specify such data models. + the three profile types, in the order specified by this framework. A + device being bootstrapped SHOULD request the device profile type (see + Section 5.3.1 for more information). The device can be configured + with a different behavior via profile data previously obtained by the + device, or by using other means such as pre-configuration or manual + configuration. The data models associated with each profile type are + out of scope for this document. Follow-on standardization activities + are expected to specify such data models. 3.4. Profile delivery stages The framework specified in this document requires a device to explicitly request profiles. It also requires one or more PDSs which provide the profile data. The processes that lead a device to obtain profile data, and any subsequent changes, can be explained in three stages, termed the profile delivery stages. Profile Enrollment: the process by which a device requests, and if @@ -535,21 +536,21 @@ parameters using DHCP. This also provides the local domain information to help with local-network profile enrollment. (B) The device requests profile enrollment for the local network profile. It receives an enrollment notification containing content indirection information from Provider A's PDS. The device retrieves the profile (this contains useful information such as firewall port restrictions and available bandwidth). (C) The device then requests profile enrollment for the device profile. It receives an enrollment notification resulting in device profile content retrieval. The device initializes the - User interface for services. + user interface for services. (D) User A with a pre-existing service relationship with Provider A attempts communication via the user Interface. The device uses the user supplied information (including any credential information) and requests profile enrollment for user A's profile. Successful enrollment and profile content retrieval results in services for user A. (E) At a different point in time, user B with a service relationship with Provider B attempts communication via the user Interface. It enrolls and retrieves user B's profile and this results in services for user B. @@ -600,22 +601,22 @@ Section 5.3.1). The data can also be "discovered" using the procedures specified by this framework. The "discovered" data can be retained across device resets (but not across factory resets) and such data is referred to as "cached". Thus, data can be configured, discovered or cached. The following requirements apply. * If the device is configured with a specific domain name (for the local network provider or device provider), it MUST NOT attempt "discovery" of the domain name. This is the case when - the device is pre-configured (e.g., via a UI) to be managed by - specific entities. + the device is pre-configured (e.g., via a user interface) to be + managed by specific entities. * The device MUST only use data associated with the provider's domain in an enrollment request. As an example, when the device is requesting a local-network profile in the domain 'example.net', it cannot present a user AoR associated with the local domain 'example.com'. * The device SHOULD adhere to the following order of data usage: configured, cached and discovered. An exception is when the device is explicitly configured to use a different order. Upon failure to obtain the profile using any methods specified in @@ -640,43 +641,46 @@ in the Request-URI (the same way it would handle any other SUBSCRIBE message). The authoritative proxy is required to examine the request (e.g., event package) and transmit it to a PDS capable of addressing the profile enrollment request. A PDS receiving the enrollment request SHOULD respond to the request, or proxy it to a PDS that can respond. An exception is when a policy prevents a response (e.g., recognition of a DoS attack, an invalid device, etc.). The PDS then verifies the identity presented in the request and performs any necessary - authentication. Once authentication is successful, the PDS MAY - admit or reject the enrollment request, based on applicable + authentication. Once authentication is successful, the PDS MUST + either admit or reject the enrollment request, based on applicable authorization policies. A PDS admitting the enrollment request indicates it via a 2xx-class response, as specified in [RFC3265]. Refer to Section 6.6 and Section 5.2 for more information on subscription request handling and security requirements, respectively. Enrollment request acceptance A PDS that admits the enrollment request verifies applicable policies, identifies the requested profile data and prepares a SIP NOTIFY message to the device. Such a notification can either contain the profile data or contain content indirection information that results in the device performing profile content retrieval. The PDS then transmits the prepared SIP notification. When the device successfully receives and accepts the SIP notification, profile enrollment is complete. When it receives the SIP NOTIFY message, indicating successful - profile enrollment, the device MUST make the new profile effective - within the specified timeframe, as described in Section 6.2. + profile enrollment, the device SHOULD make the new profile + effective within the specified time frame, as described in + Section 6.2. The exception is when the profile data is delivered + via content indirection, and the device cannot obtain the profile + data within the specified time frame. Once profile enrollment is successful, the PDS MUST consider the device enrolled for the specific profile, for the duration of the subscription. 5.1.2. Content Retrieval A successful profile enrollment leads to an initial SIP notification, and may result in subsequent change notifications. Each of these notifications can either contain profile data, or content indirection @@ -839,25 +843,26 @@ specified in [RFC4122]. The following requirements apply: o When the device has a non-alterable MAC address it SHOULD use version 1 UUID representation with the timestamp and clock sequence bits set to a value of '0'. This will allow for easy recognition, and uniqueness of MAC address based UUIDs. An exception is the case where the device supports independent device configuration for more than one SIP UA. An example would be multiple SIP UAs on the same platform. o If the device cannot use a non-alterable device identifier, it SHOULD use an alternative non-alterable device identifier. For - example, the International Manufacturer's Equipment Identifier - (IMEI) for mobile devices. + example, the International Mobile Equipment Identity (IMEI) for + mobile devices. o If the device cannot use a non-alterable MAC Address, it MUST be use the same approach as defining a user agent Instance ID in [I-D.ietf-sip-outbound]. + o Note: when the URN is used as the user part of the Request URI, it MUST be URL escaped since the colon (":") is not a legal character in the user part of an addr-spec ([RFC4122]), and must be escaped. For example, the instance ID: urn:uuid:f81d4fae-7ced-11d0-a765-00a0c91e6bf6@example.com would be escaped to look as follows in a URI: sip:urn%3auuid%3af81d4fae-7ced-11d0-a765-00a0c91e6bf6@ @@ -888,97 +893,96 @@ Profile data can contain sensitive information that needs to be secured, such as identities and credentials. Security involves authentication, message integrity and privacy. Authentication is the process by which you verify that an entity is who it claims to be, such as a user AoR presented during profile enrollment. Message integrity provides the assurance that the message contents transmitted between two entities, such as between the PDS and the device, has not been modified during transit. Privacy ensures that the message contents have not been subjected to monitoring by - unwanted elements during transit. For profile data that contains - sensitive information, authentication and message integrity are - required to ensure that the profile contents were received by a valid - entity, from a valid source, and without any modifications during - transit. For profiles that contain sensitive data, privacy is also - required. + unwanted elements during transit. Authentication and message + integrity are required to ensure that the profile contents were + received by a valid entity, from a valid source, and without any + modifications during transit. For profiles that contain sensitive + data, privacy is also required. For an overview of potential security threats, refer to Section 9. For information on how the device can be configured with identities and credentials, refer to Section 5.3.1. The following subsections provide the security requirements associated with each profile delivery stage, and applies to each of profile types specified by this framework. 5.2.1. Securing Profile Enrollment Profile enrollment may result in sensitive profile data. In such cases, the PDS MUST authenticate the device, except during the bootstrapping scenario when the device does not have existing - credentials. Additionally, the device MUST authenticate the PDS to - ensure that it is obtaining sensitive profile data from a valid PDS, - except in the bootstrapping scenario. + credentials (see Section 5.3.1 for more information on + bootstrapping). Additionally, the device MUST authenticate the PDS + to ensure that it is obtaining sensitive profile data from a valid + PDS, except in the bootstrapping scenario. To authenticate a device that has been configured with identities and credentials as specified in Section 5.3.1 and support profiles containing sensitive profile data (refer to Section 5.3.4), devices and PDSs MUST support Digest Authentication as specified in [RFC3261]. Future enhancements may provide other authentication methods such as authentication using X.509 certificates. For the device to authenticate the PDS, the device MUST mutually authenticate - with the PDS during digest authentication (device challenges the - client that responds with the Authorization header). Transmission of + with the PDS during digest authentication (device challenges the PDS, + which responds with the Authorization header). Transmission of sensitive profile data also requires message integrity. This can be - provided by configuring the device with a SIPS URI resulting in TLS - establishment ([RFC4346]). TLS also prevents offline dictionary - attacks when digest authentication is used. Thus, in the absence of - TLS, the device MUST NOT respond to any authentication challenges. - It is to be noted that the digest credentials used for obtaining - profile data via this framework may, or may not, be the same as that - used for SIP registration (see Section 5.3.1). + accomplished by configuring the device with, or by ensuring that the + discovery process during profile enrollment provides, a SIPS URI + resulting in TLS establishment ([RFC4346]). TLS also prevents + offline dictionary attacks when digest authentication is used. Thus, + in the absence of TLS, the device MUST NOT respond to any + authentication challenges. It is to be noted that the digest + credentials used for obtaining profile data via this framework may, + or may not, be the same as that used for SIP registration (see + Section 5.3.1). When the PDS challenges a profile enrollment request, and it fails, the PDS MAY refuse enrollment or provide profile data without the - user-specific information (e.g., to bootstrap a device that may have - misplaced credentials). If the device challenges, but fails to + user-specific information (e.g., to bootstrap a device as indicated + in Section 5.3.1). If the device challenges, but fails to authenticate the PDS, it MUST reject the initial notification and retry the profile enrollment process. If the device is configured - with a SIPS URI and TLS establishment fails because the next-hop SIP - entity does not support TLS, the device SHOULD attempt other resolved - next-hop SIP entities. When the device establishes TLS with the - next-hop entity, the device MUST use the procedures specified in - [RFC2818], Section 3.1, for authentication, unless it does not have - any configured information to verify the same (e.g., prior to - bootstrapping). The 'Server Identity' in this case is always the - domain of the next-hop SIP entity. If the device attempts - validation, and it fails, it MUST reject the intial notification and - retry profile enrollment. In the absence of TLS and a mechanism for - mutual authentication, the PDS MUST NOT present any sensitive profile - data in the initial notification, except when the device is being - boostrapped. It MAY still use content indirection to transmit - sensitive profile data. + with, or discovers, a SIPS URI but TLS establishment fails because + the next-hop SIP entity does not support TLS, the device SHOULD + attempt other resolved next-hop SIP entities. When the device + establishes TLS with the next-hop entity, the device MUST use the + procedures specified in [RFC2818], Section 3.1, for authentication, + unless it does not have any configured information (e.g., CA + certificate) to perform authentication (like prior to bootstrapping). + The 'Server Identity' for authentication is always the domain of the + next-hop SIP entity. If the device attempts validation, and it + fails, it MUST reject the initial notification and retry profile + enrollment. In the absence of a SIPS URI for the device and a + mechanism for mutual authentication, the PDS MUST NOT present any + sensitive profile data in the initial notification, except when the + device is being bootstrapped. It MAY still use content indirection + to transmit sensitive profile data. When a device is being provided with bootstrapping profile data - containing sensitive information, the PDS SHOULD use the SIP Identity - header as specified in [RFC4474] within the notification. This helps - with devices that MAY be pre-configured with certificates to validate - bootstrapping sources (e.g., list of allowed domain certificates, or - a list of root CA certificates using PKI). Further, the profile data - may contain the domain certificate used for creating the SIP Identity - header, for devices that are not pre-configured with any information, - and can be used to guarantee header and body integrity. It can also - allow the device to present the identity of the PDS to a user for - verification (if such an interface exists). When the SIP Identity - header is used, the PDS MUST set the host portion of the AoR in the - 'From' header to the Provider's domain (the user portion is a entity- - specific identifier). If the device is capable of validating the SIP - Identity, and it fails, it MUST reject bootstrapping profile data. + within the notification, and it contains sensitive information, the + SIP Identity header SHOULD be used as specified in [RFC4474]. This + helps with devices that MAY be pre-configured with certificates to + validate bootstrapping sources (e.g., list of allowed domain + certificates, or a list of root CA certificates using PKI). When the + SIP Identity header is used, the PDS MUST set the host portion of the + AoR in the 'From' header to the Provider's domain (the user portion + is a entity-specific identifier). If the device is capable of + validating the SIP Identity, and it fails, it MUST reject + bootstrapping profile data. 5.2.2. Securing Content Retrieval Initial or change notifications following a successful enrollment can provide a device with the requested profile data, or use content indirection to direct it to a PCC that can provide the profile data. This document specifies HTTP and HTTPS as content retrieval protocols. If the profile is provided via content indirection and contains @@ -996,89 +1000,98 @@ 5.2.3. Securing Change Notification If the device requested enrollment via a SIP subscription with a non- zero 'Expires' parameter, it can also result in change notifications for the duration of the subscription. For change notifications containing sensitive profile data, this framework RECOMMENDS the use of the SIP Identity header as specified in [RFC4474]. When the SIP Identity header is used, the PDS MUST set the host portion of the AoR in the 'From' header to the Provider's domain (the user portion is a entity-specific identifier). This provides header and body integrity - as well. However, for sensitive profile data that needs privacy and - is not being transmitted over a channel such as TLS, the PDS MUST use - content indirection. Additionally, the PDS MUST also use content - indirection for notifications containing sensitive profile data, when - the profile enrollment was not authenticated. + as well. However, for sensitive profile data requiring privacy, if + the contact URI to which the NOTIFY request is to be sent is not + SIPS, the PDS MUST use content indirection. Additionally, the PDS + MUST also use content indirection for notifications containing + sensitive profile data, when the profile enrollment was not + authenticated. 5.3. Additional Considerations This section provides additional considerations such as details on how a device obtains identities and credentials, backoff and retry methods, guidelines on profile data and additional profile types. -5.3.1. Identities and Credentials +5.3.1. Bootstrapping Identities and Credentials - When requesting a profile the device can provide an identity such as - a user AoR. To do so, the device needs to be configured. This can - be accomplished in one of the following ways: + When requesting a profile the device can provide an identity (i.e., a + user AoR), and contain associated credentials for authentication. To + do so, the device needs to obtain this information via bootstrapping. + This can be accomplished in one of the following ways: Pre-configuration The device may be pre-configured with identities and associated credentials, such as a user AoR and digest password. Out-of-band methods A device or Provider may provide hardware- or software-based - credentials such as SIM cards or USB drives. + credentials such as SIM cards or Universal Serial Bus (USB) + drives. End-user interface The end-user may be provided with the necessary identities and credentials. The end-user can then configure the device (using a user interface), or present when required (e.g., IM login screen). Using this framework When a device is initialized, even if it has no pre-configured information, it can request the local-network and device profiles. - In such a case the device profile can provide one of the following - to bootstap the device: - - * Profile data that allows the end-user to communicate by non-SIP - means with the device provider or SIP service provider. The - provider can then use any applicable method (e.g., web portal) - to provide the user AoR. + For purposes of bootstrapping, this framework recommends that the + device profile provide one of the following to bootstrap the + device: + * Profile data that allows the end-user to communicate with the + device provider or SIP service provider using non-SIP methods. + For example, the profile data can direct the end-user to a web + portal to obtain a subscription. Upon obtaining a successful + subscription, the end-user or the device can be provided with + the necessary identities and credentials. * Content indirection information to a PCC that can provide identities and credentials. As an example, consider a device that has a X.509 certificate that can be authenticated by the PCC. In such a case, the PCC can use HTTPS to provide identities and associated credentials. * Profile data containing identities and credentials that can be - used to bootstrap the device. This can be used in cases where - the device is initialized for the first time, or after a - factory reset. This can be considered only in cases where the - device is initialized in the Provider's network, for obvious - security reasons. + used to bootstrap the device (see Section 5.3.4 for profile + data recommendations). This can be used in cases where the + device is initialized for the first time, or after a factory + reset. This can be considered only in cases where the device + is initialized in the Provider's network, for obvious security + reasons. Additionally, AoRs are typically known by PDSs that serve the domain indicated by the AoR. Thus, devices can only present the configured AoRs in the respective domains. An exception is the use of federated identities. This allows a device to use a user's AoR in multiple domains. Further even within the same domain, the device's domain proxy and the PDS may be in two different realms, and as such may be associated with different credentials for digest authentication. In such cases, multiple credentials may be configured, and associated with the realms in which they are to be used. This framework - specifies only digest authentication and the device is not expected - to contain any other credentials. Future enhancements can specify - additional identities and credentials such as X.509 certificates. + specifies only digest authentication for profile enrollment and the + device is not expected to contain any other credentials. For profile + retrieval using content indirection, the device will need to support + additional credentials such as X.509 certificates (for TLS). Future + enhancements can specify additional credential types for profile + enrollment and retrieval. 5.3.2. Profile Enrollment Request Attempt A state diagram representing a device requesting any specific profile defined by this framework is shown in Figure 6. +------------+ | Initialize | +-----+------+ | @@ -1228,23 +1241,34 @@ network infrastructure elements e.g., SIP servers). 5.3.4. Profile Data This framework does not specify the contents for any profile type. Follow-on standardization activities are expected to address profile contents. However, the framework provides the following requirements and recommendations for profile data definitions: o The device profile type SHOULD specify parameters to configure the - identities and credentials. These parameters may be optional or - mandatory and will be used for dynamically configuring devices - that initialize in a network without any pre-configuration. + identities and credentials for use in scenarios such as + bootstrapping (see Section 5.3.1) and run-time modifications to + identities and credentials. This framework recommends the device + profile to provide the identities and credentials due to a couple + of reasons. The local-network profile may not always be + available, and even if present, may not be controlled by the + device provider who controls device configuration to provide + services. Further, the device may not have any users configured + prior to being bootstrapped, resulting in an absence of user + profile requests. However, this framework does not prevent other + profile types from providing identities and credentials to meet + deployment needs. For example, the user profile can contain + identities and credentials for communicating with specific + applications. o Each profile MUST clearly identify if it may contain any sensitive data. Such profiles MUST also identify the data elements that are considered sensitive, i.e., data that cannot be compromised. As an example, a device profile definition may identify itself as containing sensitive data and indicate data such as device credentials to be sensitive. o When the device receives multiple profiles, the contents of each profile type SHOULD only contain data relevant to the entity it represents. As an example, consider a device that obtains all the defined profiles. Information pertaining to the local network is @@ -1540,21 +1564,22 @@ Notifier is configured to accept such requests. The Notifier MAY also authenticate SUBSCRIBE messages even if the NOTIFY is expected to only contain a pointer to profile data. Securing data sent via Content Indirection is covered in Section 9. If the profile type indicated in the "profile-type" Event header parameter is unavailable or the Notifier is configured not to provide it, the Notifier SHOULD return a 404 response to the SUBSCRIBE request. If the specific user or device is unknown, the Notifier MAY - either accept or reject the subscription with a 403 response. + accept the subscription, or else it may reject the subscription (with + a 403 response). 6.7. Notifier Generation of NOTIFY Requests As specified in [RFC3265], the Notifier MUST always send a NOTIFY request upon accepting a subscription. If the device or user is unknown and the Notifier chooses to accept the subscription, the Notifier MAY either respond with profile data (e.g., default profile data) or provide no profile information (i.e., empty NOTIFY). If the identity indicated in the SUBSCRIBE request (From header) is a @@ -1759,26 +1783,26 @@ (XRes) the HTTP server responds to the request via a HTTP response containing the profile contents 7.2. Example 2: Device obtaining change notification The following example illustrates the case where a user (X) is simultaneously accessing services via two different devices (e.g., Multimedia entities on a PC and PDA) and has access to a user - Interface (UI) that allows for changes to the user profile. + interface that allows for changes to the user profile. The following are assumed for this example: o The devices (A & B) obtain the necessary profiles from the same SIP Service Provider. - o The SIP Service Provider also provides a user Interface (UI) that + o The SIP Service Provider also provides a user interface that allows the user to change preferences that impact the user profile. The flow diagram and an explanation of the messages follow. o Note: The example only shows retrieval of user X's profile, but it may request and retrieve other profiles (e.g., local-network, Device). ----- ----- |User |_________| UI* | * = User Interface @@ -1834,21 +1858,21 @@ | | | | (B-RX)|<= Retrieves User X's profile=>| | | | (A-EX) Device A discovers, enrolls and obtains notification related to user X's profile. (A-RX) Device A retrieves user X's profile. (B-EX) Device B discovers, enrolls and obtains notification related to user X's profile. (B-RX) Device B retrieves user X's profile. - (HPut) Changes affected by the user via the user Interface (UI) are + (HPut) Changes affected by the user via the user interface are uploaded to the HTTP Server. * Note: The UI itself can act as a device and subscribe to user X's profile. This is not the case in the example shown. (HRes) Changes are accepted by the HTTP server. (A-NT) PDS transmits a NOTIFY message to device A indicating the changed profile. A sample message is shown below: Note: Some of the fields (e.g., Via) are continued on a separate line due to format constraints of this document. NOTIFY sip:userX@192.0.2.44 SIP/2.0 @@ -1981,157 +2005,164 @@ the Request-URI and event header contents to route it to a PDS (via other SIP proxies, if required). When a PDS receives the enrollment request, it can either challenge any contained identity or admit the enrollment. Authorization rules then decide if the enrollment gets accepted. If accepted, the PDS sends an initial notification that contains either the profile data, or content indirection information. The profile data can contain generic profile data (common across multiple devices) or information specific to an entity (such as the device or a user). If specific to - an entity, it and may contain sensitive information such as - credentials. Compromise of sensitive data can lead to threats such - as impersonation attacks (establishing rogue sessions), theft of - service (if services are obtainable), and zombie attacks. Even if - the profile data is provided using content indirection, PCC - information within the notification can lead to threats such as - denial of service attacks (rogue devices bombard the PCC with - requests for a specific profile) and attempts to modify erroneous - data onto the PCC (since the location and format may be known). It - is also important for the device to ensure the authenticity of the - PNC since impersonation of the SIP service provider can lead to - Denial of Service and Man-in-the-Middle attacks. + an entity, it may contain sensitive information such as credentials. + Compromise of sensitive data can lead to threats such as + impersonation attacks (establishing rogue sessions), theft of service + (if services are obtainable), and zombie attacks. It is important + for the device to ensure the authenticity of the PNC and the PCC + since impersonation of the SIP service provider can lead to Denial of + Service and Man-in-the-Middle attacks. Profile content retrieval allows a device to retrieve profile data via content indirection from a PCC. This communication is accomplished using one of many profile delivery protocols or frameworks, such as HTTP or HTTPS as specified in this document. However, since the profile data returned is subject to the same considerations as that sent via profile notification, similar threats - exist. Thus, for the delivery of any sensitive profile data, + exist. For example, denial of service attacks (rogue devices bombard + the PCC with requests for a specific profile) and attempts to modify + erroneous data onto the PCC (since the location and format may be + known). Thus, for the delivery of any sensitive profile data, authentication of the entity requesting profile data is required. It - is also important for the requesting entity to authenticate the PDS - and ensure that the sensitive profile data is protected via message - integrity. For sensitive data that should not be subject to - snooping, privacy is also required. + is also important for the requesting entity to authenticate the + profile source via content indirection, and ensure that the sensitive + profile data is protected via message integrity. For sensitive data + that should not be subject to snooping, privacy is also required. The following sub-sections highlight the security considerations that are specific to each profile type. 9.1. Local-network profile A local network may or may not (e.g., home router) support local- network profiles as specified in this framework. Even if supported, the PDS may only be configured with a generic local-network profile that is provided to every device that requests the local-network profile. Such a PDS may not implement any authentication requirements or TLS. Alternatively, certain deployments may require the entities - device - and the PDS - to authenticate each other prior to succesful profile + and the PDS - to authenticate each other prior to successful profile enrollment. Such networks may pre-configure user identities to the devices and allow user-specific local-network profiles. In such networks the PDS will support digest, and the devices are configured with user identities and credentials as specified in Section 5.3.1. If sensitive profile data is being transmitted, the user identity is a SIPS URI that results in TLS with the next-hop (which is authenticated), and digest authentication is used by the PDS and the device. This framework supports both use cases and any variations in-between. However, devices obtaining local-network profiles from an - unauthenticated PDS are cautioned against potential MiM or PDS - impersonation attacks. This framework requires that a device reject - sensitive data, such as credentials, from unauthenticated local- - network sources. It also prohibits devices from responding to - authentication challenges in the absence of TLS. Responding to - unauthenticated challenges allows for dictionary attacks that can - reveal weak passwords. + unauthenticated PDS are cautioned against potential Man-in-the-Middle + or PDS impersonation attacks. This framework requires that a device + reject sensitive data, such as credentials, from unauthenticated + local-network sources. It also prohibits devices from responding to + authentication challenges in the absence TLS on all hops as a result + of using a SIPS URI. Responding to unauthenticated challenges allows + for dictionary attacks that can reveal weak passwords. The only + exception to accepting such sensitive data without authentication of + the PDS is in the case of bootstrapping (see Section 5.3.1). In the + case of bootstrapping, the methods employed need to be aware of + potential security threats such as impersonation. The use of SIP Identity is useful for the device to validate - notifications in the absence of a secure channel such as TLS. In - such cases the device can validate the SIP Identity header to verify - the source of the local-network profile. However, the presence of - the header does not guarantee the validity of the data. It verifies - the source and confirms data integrity, but the data obtained from an - undesired source may still be invalid, e.g., invalid outbound proxy - information, resulting in Denial of Service. Thus, devices - requesting the local-network profile from unknown networks need to be - prepared to discard information that prevent retrieval of other, - required, profiles. + notifications in the absence of a secure channel such as TLS when a + SIPS URI is used. In such cases the device can validate the SIP + Identity header to verify the source of the profile notification, and + the source of the profile data when content indirection is not used. + However, the presence of the header does not guarantee the validity + of the data. It verifies the source and confirms data integrity, but + the data obtained from an undesired source may still be invalid, + e.g., invalid outbound proxy information, resulting in Denial of + Service. Thus, devices requesting the local-network profile from + unknown networks need to be prepared to discard information that + prevent retrieval of other, required, profiles. 9.2. Device profile Device profiles deal with device-specific configuration. They may be provided to unknown devices that are attempting to obtaining profiles for purposes such as trials, self-subscription (not to be confused with [RFC3265]) and emergency services ([I-D.ietf-ecrit-phonebcp]). This framework allows for the device profile to be used for - bootstrapping a device. Such boostrapping profile data may contain + bootstrapping a device. Such bootstrapping profile data may contain enough information to connect to a Provider. For example, it may enable the device to communicate with a device provider, allowing for trial or self-subscription services via visual or audio interfaces (e.g., interactive voice response), or customer service representatives. The profile data may also allow the device a choice of device providers and allow the end-user to choose one. The profile data may also contain identities and credentials (temporary or long-term) that can be used to obtain further profile data from - the network. If it contains such sensitive data, the framework - recommends the use of the SIP Identity header by the PDS. However, - to be able to validate the header, the device needs to be pre- - configured with the knowledge of allowable domains or certificates - for validation (e.g., using PKI). If not, the device can still - guarantee header and body integrity if the profile data contains the - domain certificate (but the data can still be invalid or malicious). - In such cases, devices supporting user interfaces may obtain - confirmation from the user trying to boostrap the device (confirming - header and body integrity). However, when the SIP Identity header is - not present, or the device is not capable of validating it, the - bootstrapping data is unauthenticated and obtained without any - integrity protection. Such bootstrapping data, however, may contain - only temporary credentials (SIPS URI and digest credentials) that can - be used to reconnect to the network to ensure message integrity and - privacy prior to obtaining long-term credentials. It is to be noted - that such devices are at the mercy of the network they request the - device profile from. If they are initialized in a rogue network, or - get hijacked by a rogue PDS, the end-user may be left without desired - device operation or, worse, unwanted operation. To mitigate such - factors the device provider may communicate temporary credentials - (PINs that can be entered via an interface) or permanent credentials - (e.g., a USB device) to the end-user for connectivity. If such - methods are used then large-entropy credentials MUST be used, or - quickly replaced with such, to minimize the impact of dictionary - attacks. Future enhancements to this framework may specify device - capabilities that allow for authentication without any pre- - configuration (e.g., X.509 certificates using PKI). Alternatively, a - PDS can use secure content indirection mechanisms such as HTTPS to - provide the bootstrapping data. + the network. This framework recommends the use of the SIP Identity + header by the PDS. However, to be able to validate the SIP Identity + header, the device needs to be pre-configured with the knowledge of + allowable domains or certificates for validation (e.g., using PKI). + If not, the device can still guarantee header and body integrity if + the profile data contains the domain certificate (but the data can + still be invalid or malicious). In such cases, devices supporting + user interfaces may obtain confirmation from the user trying to + bootstrap the device (confirming header and body integrity). + However, when the SIP Identity header is not present, or the device + is not capable of validating it, the bootstrapping data is + unauthenticated and obtained without any integrity protection. Such + bootstrapping data, however, may contain only temporary credentials + (SIPS URI and digest credentials) that can be used to reconnect to + the network to ensure message integrity and privacy prior to + obtaining long-term credentials. It is to be noted that such devices + are at the mercy of the network they request the device profile from. + If they are initialized in a rogue network, or get hijacked by a + rogue PDS, the end-user may be left without desired device operation + or, worse, unwanted operation. To mitigate such factors the device + provider may communicate temporary credentials (e.g., passwords that + can be entered via an interface) or permanent credentials (e.g., a + USB device) to the end-user for connectivity. If such methods are + used, those credentials MUST be quickly replaced by large-entropy + credentials, to minimize the impact of dictionary attacks. Future + enhancements to this framework may specify device capabilities that + allow for authentication without any provider specific configuration + (e.g., X.509 certificates using PKI can allow for authentication by + any provider with access to the CA certificate). Alternatively, the + device may be pre-configured with with credentials for use with + content indirection mechanisms. In such circumstances a PDS can use + secure content indirection mechanism, such as HTTPS, to provide the + bootstrapping data. Once a device is associated with a device provider the device profile is vital to device operation. This is because the device profile can contain important operational information such as users that are to be allowed access (white-list or black-list), user credentials (if required) and other sensitive information. Thus, it is necessary to ensure that any device profile containing sensitive information is obtained via an authenticated source, with integrity protection, and delivered to an authenticated device. For sensitive information such as credentials, privacy is also required. The framework requires that devices obtain sensitive information only from authenticated entities except while it is being bootstrapped. In cases where privacy needs to be mandated for notifications, the device provider can configure the device with a SIPS URI, to be used as the subscription URI, during profile enrollment. The framework also - requires that a PDS presenting sensitive profile data to use digest + requires a PDS presenting sensitive profile data to use digest authentication. This ensures that the data is delivered to an authenticated entity. Authentication of profile retrieval via - content indirection for sensitive profiles is via HTTPS. + content indirection for sensitive profiles is via HTTPS utilizing + HTTP digest. 9.3. User profile Devices can only request user profiles for users that are known by a SIP service provider. PDSs are required to reject user profile enrollment requests for any users that are unknown in the network. For known user AoRs that are allowed to retrieve profiles, the security considerations are similar to that of the device profile (except for bootstrapping). @@ -2162,21 +2193,22 @@ from Counterpath, Alvin Jiang of Engin and Francois Audet from Nortel. The following SIPPING WG members are thanked for numerous reviews, comments and recommendations: John Elwell from Siemens, Donald Lukacs from Telcordia, Roni Even from Polycom, David Robbins from Verizon, Shida Schubert from NTT Advanced Technology Corporation, and Eugene Nechamkin from Broadcom. The editor would also like to extend a special thanks to the comments and recommendations provided by the SIPPING WG, specifically Keith Drage from Lucent (restructuring - proposal) and John Elwell from Siemens. + proposal) and John Elwell from Siemens (numerous reviews and + recommendations). Additionally, appreciation is also due to Peter Koch for expert DNS advice. And finally, sincere appreciation is extended to the chairs (Mary Barnes from Nortel and Gonzalo Camarillo from Ericsson) and the Area Directors (Cullen Jennings from Cisco and Jon Peterson from Neustar) for facilitating discussions, reviews and contributions. 11. References @@ -2244,21 +2276,22 @@ [I-D.ietf-ecrit-phonebcp] Rosen, B. and J. Polk, "Best Current Practice for Communications Services in support of Emergency Calling", draft-ietf-ecrit-phonebcp-02 (work in progress), September 2007. [I-D.ietf-sip-outbound] Jennings, C. and R. Mahy, "Managing Client Initiated Connections in the Session Initiation Protocol (SIP)", - draft-ietf-sip-outbound-10 (work in progress), July 2007. + draft-ietf-sip-outbound-11 (work in progress), + November 2007. [RFC0959] Postel, J. and J. Reynolds, "File Transfer Protocol", STD 9, RFC 959, October 1985. [RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor Extensions", RFC 2132, March 1997. [RFC4510] Zeilenga, K., "Lightweight Directory Access Protocol (LDAP): Technical Specification Road Map", RFC 4510, June 2006. @@ -2281,21 +2314,21 @@ CableLabs 858 Coal Creek Circle Louisville, Co 80027 USA Email: sumanth@cablelabs.com URI: http://www.cablelabs.com/ Full Copyright Statement - Copyright (C) The IETF Trust (2007). + Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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