One document matched: draft-livingood-dns-malwareprotect-02.xml
<?xml version="1.0" encoding="US-ASCII"?>
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<rfc ipr='pre5378Trust200902' docName='draft-livingood-dns-malwareprotect-02' category='info'>
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<!-- FRONT SECTION -->
<front>
<title abbrev='DNS Redirect for Protection from Malware'>
DNS Redirect for Protection from Malware
</title>
<!-- add role='editor' attribute to author tag below for the editors if appropriate -->
<author initials='T.' surname='Creighton' fullname='Tom Creighton'>
<organization abbrev='Comcast'>
Comcast Cable Communications
</organization>
<address>
<postal>
<street>One Comcast Center</street>
<street>1701 John F. Kennedy Boulevard</street>
<city>Philadelphia</city>
<region>PA</region>
<code>19103</code>
<country>US</country>
</postal>
<email>tom_creighton@cable.comcast.com</email>
<uri>http://www.comcast.com</uri>
</address>
<!-- author role='editor' is an optional value here -->
</author>
<author initials='C.' surname='Griffiths' fullname='Chris Griffiths'>
<organization abbrev='Comcast'>
Comcast Cable Communications
</organization>
<address>
<postal>
<street>One Comcast Center</street>
<street>1701 John F. Kennedy Boulevard</street>
<city>Philadelphia</city>
<region>PA</region>
<code>19103</code>
<country>US</country>
</postal>
<email>chris_griffiths@cable.comcast.com</email>
<uri>http://www.comcast.com</uri>
</address>
<!-- author role='editor' is an optional value here -->
</author>
<author initials='J.' surname='Livingood' fullname='Jason Livingood' role='editor'>
<organization abbrev='Comcast'>
Comcast Cable Communications
</organization>
<address>
<postal>
<street>One Comcast Center</street>
<street>1701 John F. Kennedy Boulevard</street>
<city>Philadelphia</city>
<region>PA</region>
<code>19103</code>
<country>US</country>
</postal>
<email>jason_livingood@cable.comcast.com</email>
<uri>http://www.comcast.com</uri>
</address>
<!-- author role='editor' is an optional value here -->
</author>
<author initials='R.' surname='Weber' fullname='Ralf Weber'>
<organization abbrev='Unaffiliated'>
Unaffiliated
</organization>
<address>
<postal>
<street>Bleichgarten 1</street>
<region>Hohenahr-Hohensolms</region>
<code>35644 </code>
<country>Germany</country>
</postal>
<email>rw@hohensolms.de</email>
</address>
<!-- author role='editor' is an optional value here -->
</author>
<date day='22' month='October' year='2010'/>
<!-- META-DATA DECLARATIONS -->
<area></area>
<!-- WG name at the upperleft corner of the doc; 'Internet Engineering Task Force' is fine for individual submissions. -->
<workgroup>Internet Engineering Task Force</workgroup>
<abstract>
<t>The objective of this document is to describe the design of so-called DNS-based malware protection services deployed by Internet Service Providers (ISPs), DNS Application Service Providers (ASPs), and other organizations. These organizations provide so-called DNS-based malware protection services via their recursive DNS servers. This document specifically and narrowly addresses those cases where these DNS servers are being utilized to provide a service for end users which blocks domains hosting malicious software, and makes recommendations concerning operation of such a service.</t>
</abstract>
<!-- END META-DATA DECLARATIONS -->
</front>
<!-- END FRONT SECTION -->
<!-- MIDDLE SECTION -->
<middle>
<section anchor='ReqLang' title='Requirements Language' toc='include'>
<t>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 <xref target="RFC2119"/>.</t>
</section>
<section anchor='intro' title='Introduction' toc='include'>
<t>Internet users typically are provided with several IP addresses for recursive DNS servers, as described in Section 2.3 of <xref target="RFC1591"/>, by their respective ISPs, typically in an automated fashion via DHCP <xref target="RFC2131"/>. Some other users and organizations choose to use a different set of IP address for their DNS servers, which are hosted and managed by another organization, such as a DNS ASP. It is also the case that a number of users and organizations choose to operate their own DNS servers, though those use cases are outside of the scope of this document.</t>
<t>ISPs and DNS ASPs have discovered over time that their users would like " enhanced " DNS services which can protect those users from reaching domains or fully qualified domain names (FQDNs, Section 5.1 of <xref target="RFC1035"/>) that would cause a user to inadvertently access malicious software, otherwise known simply as malware.</t>
<t>This document describes the design and function of a DNS-based malware protection service which only provides protection from domains hosting malware, as well as recommended practices and practices to avoid.</t>
</section>
<section title='Document Scope' toc='include'>
<t>This document focuses on the systems and practices of ISPs and DNS ASPs. All other use cases, such as when an Internet user or organization chooses to operate their own DNS servers is outside of the scope of this document.</t>
<t>There are several ways that such entities can provide users with these enhanced DNS services. In addition to methods which rely primarily upon a recursive DNS server, alternate methods include (a) interception and replacement of a malware-hosting domain or FQDN by web browser client software, (b) interception and replacement of a malware-hosting domain or FQDN by a tool bar, plug-in, personal firewall security software or other web browser client add-on. These alternate methods, which rely upon various types of client software, are also outside of the scope of this document.</t>
<t>It is important to note that while these alternate methods are considered out of scope for this document, this should not be interpreted as a negative judgment of their suitability or applicability to the relevant problem space. Instead, these should simply be considered as alternate methods since, as with most any technical problem, there are a variety of valid methods for solving a problem.</t>
<t>While <xref target='options'/> indicates that users must be able to opt into or out of DNS-based malware protection services, the reasons for why an ISP or DNS ASP may choose one or the other as the default are out of scope.</t>
<t>Lastly, in <xref target='malware'/> of this document, the method by which FQDNs, domains, and/or sites are added or removed from malware lists is outside the scope of this document. [EDITORIAL NOTE: THIS MAY CHANGE IN A FUTURE VERSION OF THE DOCUMENT]</t>
</section>
<section title='Terminology' toc='include'>
<t>While these terms are generally well known, it is important to define them in the context of this document.</t>
<section title='Internet Service Provider (ISP)' toc='exclude'>
<t>An Internet Service Provider, which provides Internet services, including basic network connectivity. It is not germane to this document what the method of connection is, such as wired or wireless, what the speed of such a connection is, or what other services are included or available to users. It is, however, assumed that the ISP is providing recursive DNS services to their users and is in some manner providing users with the IP addresses of these DNS servers, whether via DHCP, static assignment by users, or some other method.</t>
</section>
<section title='DNS Application Service Provider (ASP)' toc='exclude'>
<t>A DNS Application Service Provider, which provides managed and/or hosted recursive DNS services (and possibly other DNS services) to their users. In the case of managed services, the DNS ASP may remotely manage the recursive DNS servers in a user's network. For a hosted recursive DNS service, these servers are typically located outside of the user's network and these hosted resources are shared across multiple users. In most instances, these are hosted services and users are manually configuring either their DHCP server or their individual computing devices with the IP addresses of the recursive DNS servers operated by their ASP.</t>
</section>
<section title='Internet User' toc='exclude'>
<t>An Internet user, which is generally a person using a computing device to connect to and make use of the Internet. Such users are typically connected at the edge of the network, though the method by which they connect to the Internet is not particularly relevant to this document.</t>
</section>
<section title='DNS Recursive Resolver' toc='exclude'>
<t>A DNS recursive resolver processes fully qualified domain name queries (FQDN, Section 5.1 of <xref target="RFC1035"/>) into IP addresses by finding the resource records in the authoritative DNS servers for the domain associated with the FQDN. The resource records are then cached on the recursive server for future requests until an expiration timer expires called time to live (TTL), as described in Section 5.2 of <xref target="RFC2181"/>. These servers are in most cases provided by ISPs for name resolution.</t>
</section>
<section title='Web Browser' toc='exclude'>
<t>Client software operated by the user locally on their computing device, such as Microsoft Internet Explorer, Mozilla Firefox, Apple Safari, Google Chrome, etc.</t>
</section>
<section title='Malicious Domain Web Error Landing Server' toc='exclude'>
<t>The web server that a user's web browser is directed to when the DNS Recursive Server matches a DNS query to a malicious domain or FQDN. The contents of the web page that the web server sends the user varies widely across different ISPs and DNS ASPs. In most cases it simply explains that the attempted URL contains malware and that access has been prevented, though there are many other possibilities.</t>
</section>
<section title='User Options Web Server' toc='exclude'>
<t>The web server that a user is directed to via a link on a page served by the Web Error Landing Server, the Malicious Domain Web Error Landing Server, from another system such as an account management system, or via direct access, which enables a user to control whether or not they are opted into or opted out of DNS-based malware protection services. This is described in additional detail in the <xref target='options'/> section.</t>
</section>
</section>
<section title='Malicious Site Protection' toc='include' anchor='malware'>
<t>Malware websites have proliferated recently, making malware and bot networks a major problem for users. In many cases, the initial contact with a virus or malware occurs when an unsuspecting user visits a particular website. This has even been observed to occur when a user visits an otherwise legitimate website, which contains external references that happen to contain malware, for example (such as advertisements served by a third party). Many organizations maintain lists of domains and FQDNs which host malware.</t>
<section title='Malicious Site Protection Problem Statement' toc='include'>
<t>A user, malware agent, or bot requests a URL www.example.net or domain example.net. This site is associated with distributing malware or some other malicious activity that would not be desired by the user. The correct IP address is returned by the DNS and the user accesses the malware site or domain and their computer is infected with a bot.</t>
</section>
<section title='Malicious Site Protection Solution Description' toc='include'>
<t>By using Malicious Site Protection, a user may have their DNS response redirected from the IP address for the malicious URL www.example.net or domain example.net to a safe website that explains why the user was redirected. Importantly, the application attempting to access a malicious resource may or may not be a web browser and, further, may be operating without the user's knowledge and/or permission. This page on the aforementioned safe website that the user is directed to may also provide the user with a link to a method of opting out in the future. See <xref target='Malicious Domain Request and Response'/> and <xref target='Malicious Site Redirect and HTTP Flow'/> for examples below. There may also be limited cases where it could be harmful to the objective of Malicious Site Protection to redirect the user to a safe website, in which case the user may not be directed to any resource, and a NXDOMAIN response be provided.</t>
</section>
<section title='Malicious Site Protection Solution Considerations' toc='include'>
<t>It is important to note that this technology can directly impact non-web clients such as instant messaging, VPNs, FTP, email filters-related DNS queries. Thus, special exclusions may need to be made in order to prevent unintentional side effects. Design considerations for the Web Error Search and Malicious Site Protection services should include properly and promptly terminating non-HTTP connection requests. A range of resource records may be redirected, such as A, AAAA, MX, SRV, and NAPTR records, in order to fulfill the objective of preventing access to certain network elements containing malicious content or which and in some way used to transmit, relay, or otherwise transfer malicious content. All other resource record types must be answered as if there was no redirection.</t>
<t>Malicious domain protection is also only effective if a user is actually using the DNS IP addresses that have this functionality. Thus, should a user's computer become compromised with some type of bot or virus that changes their DNS IP addresses (typically without their knowledge), the malicious domain protection would have no effect since the user is now pointed to DNS servers which are presumably in the control of a third party with malicious intentions.</t>
</section>
</section>
<section title='Opt-In or Opt-Out Mechanisms' toc='include' anchor='options'>
<t>ISPs and DNS ASPs MUST provide their users with a method to opt into (opt-in) or out (opt-out) of some or all DNS-based malware protection services. Opt-out and opt-in methods should be reliable and should take into consideration the <xref target='Practices to Avoid'/> section below. Whether such services are offered on an opt-in or opt-out basis depends on a range of factors which are outside of the scope of this document. The two different methods, opt-out and opt-in, are described below.</t>
<section title='Opt-Out' toc='include'>
<t>Opt-Out is used when the users are by default offered all or some DNS-based malware protection services. As a result, the user must take an action to disable some or all such services. This is typically performed via a User Options Web Server. Users that have chosen to opt-out should receive DNS responses which are indistinguishable from those responses provided by a DNS server with no DNS Redirect functionality. In addition, opt-out should be persistent in nature, which means that opt-out should be tied to a fixed credential or attribute of some type, such as an account identifier, billing identifier, or equipment identifier, which is not typically subject to change on a regular basis.</t>
</section>
<section title='Opt-In' toc='include'>
<t>Opt-In is used when the users are by default not offered any DNS-based malware protection services. As a result, the user must take an action to enable some or all such services. This is typically performed via a User Options Web Server.</t>
</section>
<section title='Automated Mechanisms and Reasonable Processing Times' toc='include'>
<t>Once a user has selected to opt-in or opt-out of DNS-based malware protection services, such changes should occur automatically, when this is technically possible, without requiring the user to manually change any settings on their computing device. Such changes should also occur within a reasonable period of time. In some cases, however, a user may be offered the ability to speed the period of time for these changes to take effect, such as by restarting the computing device or a piece of network equipment which connects them to their ISP's network, for example.</t>
<t>While an automated mechanism may be the easiest for users, since it requires no manual reconfiguration of their network settings, the authors also recognize that there may be extenuating circumstances where this is not achievable. In such cases, which may for example be due to the particular attributes of one or another ISP's network design, a fully automated mechanism may not be possible. Another example is where a user is switching from their ISP's DNS server IP addresses to those of a DNS ASP. As a result, a user in all of these cases, as well as other possible cases, must manually reconfigure their network with different DNS IP addresses.</t>
</section>
<section title='Type of Opt-Out Method' toc='include'>
<t>There are several workable methods that can be employed to effect the actual opt-out for a given user. These include setting a local user application attribute, such as via a cookie in a web browser, as well as setting a network attribute, via a DHCP change or manually configuring the DNS IP addresses (in the operating system, modem, home gateway device, or router) in order to change the DNS IP addresses for a particular user.</t>
<t>While all of these methods are workable and can be made reliable, the best current method is via a network-based change of some sort. In this way, all Internet-connected computing devices within a given household are included in the opt-out (these devices are generally connected in some manner to the LAN side of some type of customer premise device, such as a cable modem or DSL modem). This is in contrast to a method which uses a local user application attribute, such as a cookie in a web browser, where deletion of cookies, upgrade to a new operating system, upgrade to a new web browser, use of a different web browser, or countless other factors on that device could cause the user to be opted back into a DNS-based malware protection service. Thus, a network-based approach which sets opt-out-related attributes at the device, or household level, is the most inclusive and persistent method for providing a reliable opt-out method, and is the recommended practice.</t>
</section>
</section>
<section title='Practices to Avoid' toc='include' anchor='Practices to Avoid'>
<t>This document primarily focuses on the recommended practices for an ISP or ASP to provide users with DNS-based malware protection services. However, it is important to note that some entities may not operate in accordance with such practices. As such, some of these are catalogued below in order to contrast them with recommended practices and provide information which may be of interest and use to the community.</t>
<section title='Improper Redirect of Valid Non-Malware Responses' anchor='Improper Redirect of Valid Non-Malware Responses' toc='include'>
<t>DNS-based malware protection services SHOULD NOT be utilized when there is a valid DNS resource record returned, which is not associated with malware, in response to a DNS recursive query. If this recommendation is not followed, then the effect is to redirect users to a server not maintained by the intended destination, such as a web site that looks like the intended web site but is not actually the intended site and is instead controlled by the service provider. For example a DNS query for www.example.com results in a valid A record response, but this valid response is instead replaced with an A record controlled by the service provider. In this case the intended server identified with the valid A record contained valid, lawful, non-malicious content, and there would otherwise appear to be no valid justification for a redirect to occur. See <xref target='Improper Redirect of Valid Non-Malware Response and HTTP Flow'/> for an example below.</t>
<t>If there is a valid and reasonable justification for such a redirect to occur, examples of which are not currently known by the authors of this document, then the resulting connection to the server that the user has been redirected to should clearly and prominently disclose that this is not the intended site. For example, in the case of an attempt by a user to connect to a web site, the site may contain a banner or frame which indicates that this is not the intended site or that the site is in some manner controlled by the service provider. In addition, such a notice should also offer a clear method to opt-out of this redirect function.</t>
<t>Thus, to summarize, redirection of valid responses not associated with malware SHOULD NOT be performed.</t>
</section>
<section title='Routinely Broken, Purposefully Broken, and Otherwise Unreliable Opt-Out Mechanisms' toc='include'>
<t>There are several well known and dependable methods of opt-out mechanisms that ISPs and DNS ASPs can deploy for users to opt-out of their DNS-based malware protection services. These methods can rather easily be employed and are highly recommended, as noted in <xref target='options'/>. However, some ISPs and DNS ASPs may instead choose to employ a less dependable mechanism, which routinely fails to work as expected by users or is known not to function properly.</t>
<t>For example, one routinely unreliable method for opt-out is the cookie-based method. When a user opts out of a DNS-based malware protection service, a cookie is installed in their web browser. The problem with this method occurs when a user clears their cookies or the cookies are deleted for some reason. In some cases, users may configure their web browsers to clear all cookies every time the close their web browser. Thus, one possible effect upon the user in this case is that they are once again opted into the redirect service. Furthermore, a cookie-based method has the effect of only opting out browser-based protocols (generally HTTP and HTTPS), which means that the user may have non-web applications affected by DNS Redirect, even though they believe they have opted-out. As a result, there is no assured permanency with this opt-out method, nor does it work consistently across all applications and protocols, which can be aggravating to users who do not wish to utilize DNS-based malware protection services.</t>
<t>Another example of an unreliable method for opt-out is one where opt-out is tied to the IP address of the user, where that address may be subject to change on a regular basis, such as via an ISP-based DHCP lease. In such a case, if opt-out was tied to what can be considered a largely dynamic IP address, then the user would be opted-in every time they received a new IP address, forcing them to repeatedly opt-out.</t>
<t>Thus, to summarize, the opt-out mechanism provided to users SHOULD be reliable and SHOULD NOT be routinely broken, purposefully broken, or otherwise unreliable.</t>
</section>
<section title='Markedly Slower DNS Query Performance' toc='include'>
<t>An ISP or DNS ASP should also understand that DNS query latency, the time between when a user's stub resolver issues a DNS query and receives a DNS response, should be kept as low as is reasonably possible. High DNS query latency is often perceived by users, and can have an adverse effect on a variety of applications where low DNS query latency may be especially important. Any additional processing which must be performed in order to provide DNS-based malware protection services should be monitored closely, in order that DNS Redirect functionality does not markedly slow DNS query performance.</t>
<t>Thus, to summarize, when a DNS-based malware protection service is offered, DNS query performance SHOULD NOT suffer as a result, since this could provide an incrementally inferior user experience as compared to when DNS redirect is not performed.</t>
</section>
<section title='Override of a User's DNS Selection' toc='include'>
<t>Some users may decide to use the DNS server IP addresses of a DNS ASP or other non-ISP-provided DNS servers. Such selections should be preserved as the free choice of a user, particularly when DNS-based malware protection services are offered. Thus, an ISP SHOULD NOT redirect port 53 DNS traffic from servers intended by the user via their selection of non-ISP DNS servers to the DNS servers of the ISP, except in reasonable and justifiable cases where a user has been placed into a so-called "walled garden" for reasons of abuse, security compromise, account non-payment, new service activation, etc.</t>
<t>However, there MAY be at least one major exception to this recommendation. There may be cases of known bad DNS resolvers, generally called rogue DNS servers, which have been setup by distributors of malware. When malware is installed on a host, commands can be sent to modify that host's DNS server IP addresses, changing them to point to these rogue DNS servers. As a result, the party controlling the installed malware has the ability to control all DNS resolution for the host. In some cases, the IP addresses of these rogue DNS servers may be know by the ISP, in which case it may be a security best practice to block access to these rogue DNS servers.</t>
</section>
</section>
<section title='Functional Design' toc='include'>
<t>The functional design described in this section is intended to be generally representative of the many different ways that DNS-based malware protection services are deployed today. As such, they are necessarily high level and different implementations may vary somewhat, due to any number of factors.</t>
<section title='Web Browser Client'>
<t>The Web Browser Client, which is software running on a user's host, is redirected to a Malware Protection Web Landing Page instead of directing the user to a site which contains malware.</t>
<t>Examples of common Web Browser Clients include:
<list style='symbols'>
<t>Microsoft Internet Explorer</t>
<t>Mozilla Firefox</t>
<t>Apple Safari</t>
<t>Google Chrome</t>
<t>Opera</t>
</list>
</t>
</section>
<section title='Malicious Domain List' toc='include'>
<t>Using a Malicious Domain List, a DNS server can redirect DNS requests that were intended for malicious websites or domains to a web server landing page (see <xref target='Malicious Domain Request and Response'/>), the Malware Protection Web Landing Page. The Malicious Domain List can contain both domains, such as *.example.net, as well as specific FQDNs, such as www.example.net.</t>
</section>
<section title='End to End View of Malware Protection Service' toc='include'>
<t><xref target='Malicious Domain Request and Response'/> shows the host and relevant DNS servers, as well as a resulting redirection to protect a user from accessing malware.</t>
<figure anchor='Malicious Domain Request and Response' title='Malicious Domain Request and Response'>
<artwork><![CDATA[
Request Request
www.example.net www.example.net
+--------+ +--------+
++--++ ---------------> | | --------------->| |
|| || | | | |
+-++--++-+ | | | |
+--------+ <-------------- | | <------------- | |
Host Malware +--------+ Response +--------+
Computer Protection Recursive IP Address Authoritative
IP Address Server Server
|
| ___________________________________
| +--------+ | Web Response: |
| | | | "Malware software alert!" |
+-------> | | ------> |__________________________________|
| | | The site you attempted to access |
| | | is known to host malware that |
+--------+ | could damage your computer. |
Web Server |__________________________________|
Landing Page
]]></artwork></figure>
</section>
</section>
<section title='Example DNS and HTTP Flows' toc='include'>
<section title='Successful DNS Lookup and HTTP Flow' toc='exclude'>
<t>This example represents a successful lookup of a valid DNS RR, and the resulting HTTP transaction. In this case, the RR is not associated with malware.</t>
<figure anchor='Successful DNS Lookup and HTTP Flow' title='Successful DNS Lookup and HTTP Flow'>
<artwork><![CDATA[
Web DNS R DNS A DNS Web Server
Browser Client Server Server 10.1.10.10
| Request | A | | |
|www.example. |Record Query | A | |
| com |www.example. |Record Query | |
|------------>| com |www.example. | |
| |------------>| com | |
| | |------------>| |
| | | A Record | |
| | A Record | 10.1.10.10 | |
| DNS Response| 10.1.10.10 |<------------| |
| 10.1.10.10 |<------------| | |
|<------------| | | |
| HTTP GET | | | |
| 10.1.10.10 | | | |
|------------------------------------------------------>|
| | | | |
| | | | |
| | | | |
]]></artwork></figure>
</section>
<section title='Malicious Site Redirect and HTTP Flow' toc='exclude'>
<t>This example represents a lookup of a valid RR which hosts malware, and the HTTP transaction that results from a typical Malicious Site Protection service.</t>
<figure anchor='Malicious Site Redirect and HTTP Flow' title='Malicious Site Redirect and HTTP Flow'>
<artwork><![CDATA[
R DNS Malware Protection
Host R DNS Server Web Server
Computer Server Malware List 10.2.20.20
| A | Malware | |
|Record Query | List | |
|www.example. | Query | |
| net |www.example. | |
|------------>| net | |
| |------------>| |
| | Postivie | |
| A Record | Match | |
| 10.2.20.20 |<------------| |
|<------------| | |
| HTTP GET | | |
| 10.2.20.20 | | |
|---------------------------------------->|
| | | HTTP 200 OK |
|<----------------------------------------|
| | | |
]]></artwork></figure>
</section>
<section title='Improper Redirect of Valid Non-Malware Response and HTTP Flow' anchor='Improper Redirect Section' toc='exclude'>
<t>This example represents an improper redirect occurring when a valid DNS RR should have been returned in response to a DNS recursive query for an example website, the resulting HTTP transaction, and that no DNS query or HTTP traffic was sent to the valid authoritative DNS server and valid web server. <xref target='DNSSEC Considerations Section'/> shows one of the reasons why this practice is problematic. Another reason is that a user intends to visit a valid resource with lawful and legitimate content, such as a web site, and is instead sent to a different destination (which may even closely resemble the intended site, in the pattern used by phishing sites).</t>
<figure anchor='Improper Redirect of Valid Non-Malware Response and HTTP Flow' title='Improper Redirect of Valid Non-Malware Response and HTTP Flow'>
<artwork><![CDATA[
R DNS Improper Valid
Server Redirect Valid Web
Host R DNS Improper Web Server A DNS Server
Computer Server Reirect List 10.2.20.20 Server 10.1.10.10
| A | Improper | | | |
|Record Query |Redirect List| | | |
|www.example. | Query | | | |
| com |www.example. | | | |
|------------>| com | | | |
| |------------>| | | |
| | Postivie | | | |
| A Record | Match | | | |
| 10.2.20.20 |<------------| | | |
|<------------| | | | |
| HTTP GET | | | | |
| 10.2.20.20 | | | | |
|-------------------------------------->| | |
| | |HTTP 200 OK| | |
|<--------------------------------------| | |
| | | | | |
]]></artwork></figure>
</section>
</section>
<section title='DNSSEC Considerations and Implications' anchor='DNSSEC Considerations Section' toc='include'>
<t>DNS security extensions defined in <xref target='RFC4033'/>, <xref target='RFC4034'/>, and <xref target='RFC4035'/> use cryptographic digital signatures to provide origin authentication and integrity assurance for DNS data. This is done by creating signatures for DNS data on a DNS Security-Aware Authoritative Name Server that can be used by DNS Security-Aware Resolvers to verify the answers.</t>
<t>DNSSEC is now in the process of being deployed on authoritative servers, now that the DNS root has been signed and several key Top Level Domains (TLDs) have been signed. DNSSEC is also starting to be adopted by service providers, which are now in the process of adding DNSSEC validation in DNS recursive resolvers.</t>
<t>It is critically important that service providers understand that adoption of DNSSEC is technically incompatible with DNS redirect. As such, in order to properly implement DNSSEC and maintain a valid chain of trust, DNS redirect MUST NOT be used any longer. Thus, once DNSSEC is in widespread use, this document should be considered historical. That being said, sections of this document concerning opt-in and opt-out practices may be useful for future reference in other, unrelated documents.</t>
<t><xref target='Improper Redirect of Valid Non-Malware Responses'/> and <xref target='Improper Redirect Section'/> describe how a more generalized DNS redirect SHOULD NOT be used with a malware protection service and, in addition, such a generalized DNS redirect services is in any case incompatible with DNSSEC.</t>
</section>
<section title='Security Considerations' toc='include'>
<t>Security best practices should be followed regarding access to the opt-in and opt-out functions, in order that someone other than the user is able to change the user's DNS Redirect settings. For example, the User Options Web Server must not permit someone to modify a page URI to access and change another user's options. Thus, if the URI is "http://www.example.net/redirect-options.php?account=1234", someone must not be able to modify the account to be "=1235" and then be able to change the options for a different user with some other additional validation being performed. While web site security practices are outside the scope of this document, the authors believe it is important to identify such problematic use cases to any ISPs and DNS ASPs offering and/or implementing DNS Redirect functionality.</t>
</section>
<section title='IANA Considerations' toc='include'>
<t>There are no IANA considerations in this document.</t>
</section>
<section title='Contributors' toc='include'>
<t>The following people made significant textual contributions to this document and played an important role in the development and evolution of this document:</t>
<t>Don Bowman, Sandvine (don@sandvine.com)</t>
<t>Rick Hiester, Verizon (richard.hiester@verizon.com)</t>
<t>Chris Roosenraad, Time Warner Cable (chris.roosenraad@twcable.com)</t>
<t>David Ulevitch, OpenDNS (david@opendns.com)</t>
</section>
<section title='Acknowledgements' toc='include'>
<t>The authors and contributors also wish to acknowledge the assistance of the following individuals in helping us to develop and/or review this document: </t>
<t>John Barnitz, Comcast Cable Communications (john_barnitz@cable.comcast.com)</t>
<t>Mike Burns, Cablevision (mburns@cablevision.com)</t>
<t>Phil Marcella, Comcast Interactive Media (phillip_marcella@cable.comcast.com)</t>
<t>Luis Uribarri, Comcast Cable Communications (luis_uribarri@cable.comcast.com)</t>
<t>Sandy Wilbourn, Nominum (sandy.wilbourn@nominum.com)</t>
<t>Matt Williams, Cox Cable (matt.williams@cox.com)</t>
<t>The authors and contributors also wish to thank ICANN's Security and Stability Advisory Committee (SSAC) for their review and debate of this document, as well as for raising important questions concerning DNSSEC compatibility.</t>
</section>
<!-- appendix -->
</middle>
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<back>
<references title='Normative References'>
&RFC2119;
&RFC1034;
&RFC1035;
&RFC1536;
&RFC1591;
&RFC2131;
&RFC2136;
&RFC2181;
&RFC2308;
&RFC4033;
&RFC4034;
&RFC4035;
</references>
<section title='Document Change Log'>
<t>[RFC Editor: This section is to be removed before publication]</t>
<t>02: Made minor adjustments to mirror changes made in another draft updated today. Closed open issue to remove references to RFC 2535, which is obsolete.</t>
<t>01: Removed old legacy content from the more generalized draft that preceded this one</t>
<t>00: First version published</t>
</section>
<section title='Open Issues'>
<t>[RFC Editor: This section is to be removed before publication]</t>
<t>
<list style='numbers'>
<t>CRITICAL: THIS DOCUMENT HAS BEEN SPLIT OFF FROM A GENERAL DNS REDIRECT DOCUMENT. THIS VERSION IS A SIMPLE REPURPOSING OF THE CONTENT FROM THE OLD DOCUMENT. EXISTING AUTHORS NOW NEED TO PERFORM A FULL DOCUMENT REVIEW TO ENSURE THAT THE NEW CONTENT HAS CARRIED OVER CORRECTLY AND THAT IT MAKES SENSE AND THAT THEY STILL SUPPORT THE DOCUMENT AND CAN CONTRIBUTE TO IT.</t>
<t>RW: Consider whether it is a good idea to add to section 4.9 (NXDOMAIN RESPONSE) a reference to Authenticated Denial of Existence described in RFC4035 section 5.4 as these should be also redirected.</t>
<t>MB: Consider addressing how opt-out works when a user roams across a shared WiFi AP.</t>
<t>JL: Consider capitalizing RFC 2119 language used.</t>
<t>JL: What sort of DNSSEC section is needed?</t>
</list>
</t>
</section>
</back>
<!-- END BACK SECTION -->
</rfc>
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