Misplaced Pages

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97-723: DDDS defines a mechanism for using the Domain Name System (DNS) as the database for arbitrary identifier schemes. The primary logical DNS container used to hold DDDS information is the NAPTR record . DDDS is defined in RFC   3401 , 3402 , 3403 , 3404 and 3405 . RFC 3401 expresses the system as follows: The Dynamic Delegation Discovery System is used to implement lazy binding of strings to data, in order to support dynamically configured delegation systems. The DDDS functions by mapping some unique string to data stored within

194-446: A label and zero or more resource records (RR), which hold information associated with the domain name. The domain name itself consists of the label, concatenated with the name of its parent node on the right, separated by a dot. The tree sub-divides into zones beginning at the root zone . A DNS zone may consist of as many domains and subdomains as the zone manager chooses. DNS can also be partitioned according to class where

291-559: A man in the middle attack is going on, stripping the DNSSEC information and modifying the A records. Or, it could be a broken security-oblivious name server along the way that stripped the DO flag bit from the query or the RRSIG record from the answer. Or, it could be a configuration error. Next, it may be that there is not a domain name named "www.example.com", in which case instead of returning

388-483: A "com" server, and finally an "example.com" server. Name servers in delegations are identified by name, rather than by IP address. This means that a resolving name server must issue another DNS request to find out the IP address of the server to which it has been referred. If the name given in the delegation is a subdomain of the domain for which the delegation is being provided, there is a circular dependency . In this case,

485-535: A DDDS Database by iteratively applying string transformation rules until a terminal condition is reached. Telephone Number Mapping (ENUM), specified in RFC 6116, is defined as a DDDS application to resolve telephone numbers into DNS data. This computer networking article is a stub . You can help Misplaced Pages by expanding it . Domain Name System Early research and development: Merging

582-521: A RRSIG record in the answer, there will be either an NSEC record or an NSEC3 record. These are "next secure" records that allow the resolver to prove that a domain name does not exist. The NSEC/NSEC3 records have RRSIG records, which can be verified as above. Finally, it may be that the "example.com" zone implements DNSSEC, but either the "com" zone or the root zone do not, creating an "island of security" which needs to be validated in some other way. As of 15 July 2010 , deployment of DNSSEC to root

679-408: A cache of data. An authoritative name server can either be a primary server or a secondary server. Historically the terms master/slave and primary/secondary were sometimes used interchangeably but the current practice is to use the latter form. A primary server is a server that stores the original copies of all zone records. A secondary server uses a special automatic updating mechanism in

776-416: A combination of these methods. In a non-recursive query , a DNS resolver queries a DNS server that provides a record either for which the server is authoritative, or it provides a partial result without querying other servers. In case of a caching DNS resolver , the non-recursive query of its local DNS cache delivers a result and reduces the load on upstream DNS servers by caching DNS resource records for

873-478: A complete authentication chain, an answer to a DNS lookup cannot be securely authenticated. To limit replay attacks, there are not only the normal DNS TTL values for caching purposes, but additional timestamps in RRSIG records to limit the validity of a signature. Unlike TTL values which are relative to when the records were sent, the timestamps are absolute. This means that all security-aware DNS resolvers must have clocks that are fairly closely in sync, say to within

970-472: A complex six-message protocol and a lot of data transfers to perform key changes for a child (DNS child zones had to send all of their data up to the parent, have the parent sign each record, and then send those signatures back to the child for the child to store in a SIG record). Also, public key changes could have absurd effects; for example, if the ".com" zone changed its public key, it would have to send 22 million records (because it would need to update all of

1067-706: A compromise between five competing proposals of solutions to Paul Mockapetris . Mockapetris instead created the Domain Name System in 1983 while at the University of Southern California . The Internet Engineering Task Force published the original specifications in RFC 882 and RFC 883 in November 1983. These were updated in RFC 973 in January 1986. In 1984, four UC Berkeley students, Douglas Terry, Mark Painter, David Riggle, and Songnian Zhou, wrote

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1164-399: A dataset from a reliable source. Assuming the resolver has no cached records to accelerate the process, the resolution process starts with a query to one of the root servers. In typical operation, the root servers do not answer directly, but respond with a referral to more authoritative servers, e.g., a query for "www.wikipedia.org" is referred to the org servers. The resolver now queries

1261-521: A few minutes. These timestamps imply that a zone must regularly be re-signed and re-distributed to secondary servers, or the signatures will be rejected by validating resolvers. DNSSEC involves many different keys, stored both in DNSKEY records, and from other sources to form trust anchors . In order to allow for replacement keys, a key rollover scheme is required. Typically, this involves first rolling out new keys in new DNSKEY records, in addition to

1358-599: A general purpose database, the DNS has also been used in combating unsolicited email (spam) by storing a real-time blackhole list (RBL). The DNS database is traditionally stored in a structured text file, the zone file , but other database systems are common. The Domain Name System originally used the User Datagram Protocol (UDP) as transport over IP. Reliability, security, and privacy concerns spawned

1455-450: A parent and child zone. In the new approach, when a child's master public key changes, instead of having six messages for every record in the child, there is one simple message: the child sends the new public key to its parent (signed, of course). Parents simply store one master public key for each child; this is much more practical. This means that a little data is pushed to the parent, instead of massive amounts of data being exchanged between

1552-407: A period of time after an initial response from upstream DNS servers. In a recursive query , a DNS resolver queries a single DNS server, which may in turn query other DNS servers on behalf of the requester. For example, a simple stub resolver running on a home router typically makes a recursive query to the DNS server run by the user's ISP . A recursive query is one for which the DNS server answers

1649-564: A result, ZSKs can be much shorter than KSKs and still offer the same level of protection while reducing the size of the RRSIG/DNSKEY records. When a new KSK is created, the DS record must be transferred to the parent zone and published there. The DS records use a message digest of the KSK instead of the complete key in order to keep the size of the records small. This is helpful for zones such as

1746-469: A service's location on the network to change without affecting the end users, who continue to use the same hostname. Users take advantage of this when they use meaningful Uniform Resource Locators ( URLs ) and e-mail addresses without having to know how the computer actually locates the services. An important and ubiquitous function of the DNS is its central role in distributed Internet services such as cloud services and content delivery networks . When

1843-550: A set of verified public keys for the DNS root zone which is the trusted third party . Domain owners generate their own keys, and upload them using their DNS control panel at their domain-name registrar, which in turn pushes the keys via secDNS to the zone operator (e.g., Verisign for .com) who signs and publishes them in DNS. DNS is implemented by the use of several resource records. To implement DNSSEC, several new DNS record types were created or adapted to use with DNSSEC: When DNSSEC

1940-422: A stub resolver, and Windows Server 2008 R2 and Windows 7 in particular use a non-validating but DNSSEC-aware stub resolver. Using the chain of trust model, a Delegation Signer (DS) record in a parent domain ( DNS zone ) can be used to verify a DNSKEY record in a subdomain , which can then contain other DS records to verify further subdomains. Say that a recursive resolver such as an ISP name server wants to get

2037-630: A time to live (TTL), which indicates how long the information remains valid before it needs to be discarded or refreshed. This TTL is determined by the administrator of the authoritative DNS server and can range from a few seconds to several days or even weeks. DNSSEC The Domain Name System Security Extensions ( DNSSEC ) is a suite of extension specifications by the Internet Engineering Task Force (IETF) for securing data exchanged in

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2134-477: A type of error called a "lame delegation" or "lame response". Domain name resolvers determine the domain name servers responsible for the domain name in question by a sequence of queries starting with the right-most (top-level) domain label. For proper operation of its domain name resolver, a network host is configured with an initial cache ( hints ) of the known addresses of the root name servers. The hints are updated periodically by an administrator by retrieving

2231-458: A user accesses a distributed Internet service using a URL, the domain name of the URL is translated to the IP address of a server that is proximal to the user. The key functionality of the DNS exploited here is that different users can simultaneously receive different translations for the same domain name, a key point of divergence from a traditional phone-book view of the DNS. This process of using

2328-546: A zone before many others will want to adopt it. DNS servers must be updated with software that supports DNSSEC, and DNSSEC data must be created and added to the DNS zone data. A TCP/IP-using client must have their DNS resolver (client) updated before it can use DNSSEC's capabilities. What is more, any resolver must have, or have a way to acquire, at least one public key that it can trust before it can start using DNSSEC. DNSSEC implementation can add significant load to some DNS servers. Common DNSSEC-signed responses are far larger than

2425-537: Is a critical and fundamental Internet service, yet in 1990 Steve Bellovin discovered serious security flaws in it. Research into securing it began, and progressed dramatically when his paper was made public in 1995. The initial RFC 2065 was published by the IETF in 1997, and initial attempts to implement that specification led to a revised (and believed fully workable) specification in 1999 as IETF RFC 2535. Plans were made to deploy DNSSEC based on RFC 2535. Unfortunately,

2522-474: Is also BCP 237. It is widely believed that securing the DNS is critically important for securing the Internet as a whole, but deployment of DNSSEC specifically has been hampered (As of 22 January 2010 ) by several difficulties: DNSSEC works by digitally signing records for DNS lookup using public-key cryptography . The correct DNSKEY record is authenticated via a chain of trust , starting with

2619-446: Is also challenging. Ozment and Schechter observe that DNSSEC (and other technologies) has a "bootstrap problem": users typically only deploy a technology if they receive an immediate benefit, but if a minimal level of deployment is required before any users receive a benefit greater than their costs (as is true for DNSSEC), it is difficult to deploy. DNSSEC can be deployed at any level of a DNS hierarchy, but it must be widely available in

2716-473: Is completed. The .com domain was signed with valid security keys and the secure delegation was added to the root zone on 1 April 2011. Stub resolvers are "minimal DNS resolvers that use recursive query mode to offload most of the work of DNS resolution to a recursive name server." A stub resolver will simply forward a request to a recursive name server, and use the Authenticated Data (AD) bit in

2813-492: Is known as the LDH rule (letters, digits, hyphen). Domain names are interpreted in a case-independent manner. Labels may not start or end with a hyphen. An additional rule requires that top-level domain names should not be all-numeric. The limited set of ASCII characters permitted in the DNS prevented the representation of names and words of many languages in their native alphabets or scripts. To make this possible, ICANN approved

2910-426: Is not a problem for online signing servers, which keep their keys available online. However, DNSSEC was designed around using offline computers to sign records so that zone-signing-keys could be kept in cold storage. This represents a problem when trying to authenticate responses to queries for non-existent domains since it is impossible to pre-generate a response to every possible hostname query. The initial solution

3007-403: Is ongoing to deploy DNSSEC, because the Internet is so vital to so many organizations. Early adopters include Brazil ( .br ), Bulgaria ( .bg ), Czech Republic ( .cz ), Namibia ( .na ) Puerto Rico ( .pr ) and Sweden ( .se ), who use DNSSEC for their country code top-level domains ; RIPE NCC , who have signed all the reverse lookup records (in-addr.arpa) that are delegated to it from

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3104-488: Is only achieved with at least 6 labels (counting the last null label). Although no technical limitation exists to prevent domain name labels from using any character that is representable by an octet, hostnames use a preferred format and character set. The characters allowed in labels are a subset of the ASCII character set, consisting of characters a through z , A through Z , digits 0 through 9 , and hyphen. This rule

3201-472: Is published in RFC4033-4035. In January 2024, a "KeyTrap" denial-of-service attack was announced for all specification-respecting DNSSEC resolvers. The DNSSEC specification (RFC4033-4035) specifies that a resolver, when receiving a signed packet from the upstream, should try all keys with the correct "tag" on all signatures until one of the combinations successfully verifies. By putting many keys with

3298-399: Is served by the root name servers , the servers to query when looking up ( resolving ) a TLD . An authoritative name server is a name server that only gives answers to DNS queries from data that have been configured by an original source, for example, the domain administrator or by dynamic DNS methods, in contrast to answers obtained via a query to another name server that only maintains

3395-455: Is used in the authentication of DNSKEYs in the lookup procedure using the chain of trust. NSEC and NSEC3 records are used for robust resistance against spoofing. DNSSEC was designed to be extensible so that as attacks are discovered against existing algorithms, new ones can be introduced in a backward-compatible fashion as described in RFC   8624 . The following table defines, as of June 2019,

3492-428: Is used, each answer to a DNS lookup contains an RRSIG DNS record, in addition to the record type that was requested. The RRSIG record is a digital signature of the answer DNS resource record set. The digital signature is verified by locating the correct public key found in a DNSKEY record. The NSEC and NSEC3 records are used to provide cryptographic evidence of the non-existence of any Resource Record (RR). The DS record

3589-628: The .com domain, which are very large. The procedure to update DS keys in the parent zone is also simpler than earlier DNSSEC versions that required DNSKEY records to be in the parent zone. A closely related principle is that of Algorithm rollover , this involves migrating a zone from one signing Algorithm to another. A good example of this would be migrating from Algorithm 8 (RSA/SHA-256) to Algorithm 13 (ECDSA/SHA-256). Several ccTLD's have already migrated including .at , .br , .cz , .ch , .fr , .ie , .nl and .ph . Verisign migrated .com, .net and .edu to Algorithm 13 in late 2023. The migration of

3686-616: The Domain Name System ( DNS ) in Internet Protocol ( IP ) networks . The protocol provides cryptographic authentication of data, authenticated denial of existence, and data integrity , but not availability or confidentiality . The original design of the Domain Name System did not include any security features. It was conceived only as a scalable distributed system. The Domain Name System Security Extensions (DNSSEC) attempt to add security, while maintaining backward compatibility . RFC   3833 of 2004 documents some of

3783-551: The Internationalizing Domain Names in Applications (IDNA) system, by which user applications, such as web browsers, map Unicode strings into the valid DNS character set using Punycode . In 2009, ICANN approved the installation of internationalized domain name country code top-level domains ( ccTLD s) . In addition, many registries of the existing top-level domain names ( TLD s ) have adopted

3880-514: The Internet Assigned Numbers Authority (IANA). ARIN is also signing their reverse zones. In February 2007, TDC became the first Swedish ISP to start offering this feature to its customers. IANA publicly tested a sample signed root since June 2007. During this period prior to the production signing of the root, there were also several alternative trust anchors. The IKS Jena introduced one on January 19, 2006,

3977-530: The Internet Systems Consortium introduced another on March 27 of the same year, while ICANN themselves announced a third on February 17, 2009. On June 2, 2009, Afilias , the registry service provider for Public Interest Registry 's .org zone signed the .org TLD. Afilias and PIR also detailed on September 26, 2008, that the first phase, involving large registrars it has a strong working relationship with ("friends and family") would be

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4074-415: The operating system or via some other trusted source. When DNSSEC was originally designed, it was thought that the only trust anchor that would be needed was for the DNS root . The root anchors were first published on 15 July 2010. An authentication chain is a series of linked DS and DNSKEY records, starting with a trust anchor to the authoritative name server for the domain in question. Without

4171-478: The top-level domain ; for example, the domain name www.example.com belongs to the top-level domain com . The hierarchy of domains descends from right to left; each label to the left specifies a subdivision, or subdomain of the domain to the right. For example, the label example specifies a subdomain of the com domain, and www is a subdomain of example.com. This tree of subdivisions may have up to 127 levels. A label may contain zero to 63 characters, because

4268-404: The " Authoritative Answer " ( AA ) bit in its responses. This flag is usually reproduced prominently in the output of DNS administration query tools, such as dig , to indicate that the responding name server is an authority for the domain name in question. When a name server is designated as the authoritative server for a domain name for which it does not have authoritative data, it presents

4365-475: The (fictitious) domains j.example.com and l.example.com . This is also possible with NSEC3 records. CloudFlare pioneered a pair of alternative approaches, which manage to achieve the same result in one third of the response size. The first is a variation on the "white lies" approach, called "black lies", which exploits common DNS client behavior to state the nonexistence more compactly. The second approach instead chooses to prove that "the record exists but

4462-540: The ARPANET. Elizabeth Feinler developed and maintained the first ARPANET directory. Maintenance of numerical addresses, called the Assigned Numbers List, was handled by Jon Postel at the University of Southern California 's Information Sciences Institute (ISI), whose team worked closely with SRI. Addresses were assigned manually. Computers, including their hostnames and addresses, were added to

4559-560: The Checking Disabled (CD) bit in its query messages. A validating stub resolver uses the CD bit to perform its own recursive authentication. Using such a validating stub resolver gives the client end-to-end DNS security for domains implementing DNSSEC, even if the Internet service provider or the connection to them is not trusted. Non-validating stub resolvers must rely on external DNSSEC validation services, such as those controlled by

4656-462: The DNS database are for start of authority ( SOA ), IP addresses ( A and AAAA ), SMTP mail exchangers (MX), name servers (NS), pointers for reverse DNS lookups (PTR), and domain name aliases (CNAME). Although not intended to be a general purpose database, DNS has been expanded over time to store records for other types of data for either automatic lookups, such as DNSSEC records, or for human queries such as responsible person (RP) records. As

4753-401: The DNS protocol in communication with its primary to maintain an identical copy of the primary records. Every DNS zone must be assigned a set of authoritative name servers. This set of servers is stored in the parent domain zone with name server (NS) records. An authoritative server indicates its status of supplying definitive answers, deemed authoritative , by setting a protocol flag, called

4850-417: The DNS to assign proximal servers to users is key to providing faster and more reliable responses on the Internet and is widely used by most major Internet services. The DNS reflects the structure of administrative responsibility on the Internet. Each subdomain is a zone of administrative autonomy delegated to a manager. For zones operated by a registry , administrative information is often complemented by

4947-460: The IDNA system, guided by RFC 5890, RFC 5891, RFC 5892, RFC 5893. The Domain Name System is maintained by a distributed database system, which uses the client–server model . The nodes of this database are the name servers . Each domain has at least one authoritative DNS server that publishes information about that domain and the name servers of any domains subordinate to it. The top of the hierarchy

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5044-482: The IETF RFC 2535 specification had very significant problems scaling up to the full Internet; by 2001 it became clear that this specification was unusable for large networks. In normal operation DNS servers often get out of sync with their parents. This isn't usually a problem, but when DNSSEC is enabled, this out-of-sync data could have the effect of a serious self-created denial of service. The original DNSSEC required

5141-430: The IP address spaces . The Domain Name System maintains the domain name hierarchy and provides translation services between it and the address spaces. Internet name servers and a communication protocol implement the Domain Name System. A DNS name server is a server that stores the DNS records for a domain; a DNS name server responds with answers to queries against its database. The most common types of records stored in

5238-412: The IP addresses ( A record and/or AAAA records ) of the domain "www. example.com ". There are several exceptions to the above example. First, if "example.com" does not support DNSSEC, there will be no RRSIG record in the answer and there will not be a DS record for "example.com" in the "com" zone. If there is a DS record for "example.com", but no RRSIG record in the reply, something is wrong and maybe

5335-402: The Internet, and increase performance in end-user applications, the Domain Name System supports DNS cache servers which store DNS query results for a period of time determined in the configuration ( time-to-live ) of the domain name record in question. Typically, such caching DNS servers also implement the recursive algorithm necessary to resolve a given name starting with the DNS root through to

5432-496: The ability to more easily enumerate a zone. Due to the messy evolution of the protocol and a desire to preserve backwards compatibility, online DNSSEC signing servers return a "white lie" instead of authenticating a denial of existence directly. The technique outlined in RFC 4470 returns a NSEC record in which the pairs of domains lexically surrounding the requested domain. For example, request for k.example.com would thus result in an NSEC record proving that nothing exists between

5529-704: The associated entities. Most prominently, it translates readily memorized domain names to the numerical IP addresses needed for locating and identifying computer services and devices with the underlying network protocols . The Domain Name System has been an essential component of the functionality of the Internet since 1985. The Domain Name System delegates the responsibility of assigning domain names and mapping those names to Internet resources by designating authoritative name servers for each domain. Network administrators may delegate authority over subdomains of their allocated name space to other name servers. This mechanism provides distributed and fault-tolerant service and

5626-543: The authoritative name servers of the queried domain. With this function implemented in the name server, user applications gain efficiency in design and operation. The combination of DNS caching and recursive functions in a name server is not mandatory; the functions can be implemented independently in servers for special purposes. Internet service providers typically provide recursive and caching name servers for their customers. In addition, many home networking routers implement DNS caches and recursion to improve efficiency in

5723-475: The computer. Computers at educational institutions would have the domain edu , for example. She and her team managed the Host Naming Registry from 1972 to 1989. By the early 1980s, maintaining a single, centralized host table had become slow and unwieldy and the emerging network required an automated naming system to address technical and personnel issues. Postel directed the task of forging

5820-438: The data is truly from or not available from the domain owner. The DNSSEC specifications (called DNSSEC-bis ) describe the current DNSSEC protocol in great detail. See RFC   4033 , RFC   4034 , and RFC   4035 . With the publication of these new RFCs (March 2005), an earlier RFC, RFC   2535 has become obsolete. The full set of RFCs that specify DNSSEC are collected in RFC   9364 , which

5917-573: The default UDP size of 512 bytes. In theory, this can be handled through multiple IP fragments, but many "middleboxes" in the field do not handle these correctly. This leads to the use of TCP instead. Yet many current TCP implementations store a great deal of data for each TCP connection; heavily loaded servers can run out of resources simply trying to respond to a larger number of (possibly bogus) DNSSEC requests. Some protocol extensions, such as TCP Cookie Transactions , have been developed to reduce this loading. To address these challenges, significant effort

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6014-438: The delegation for example.org. The glue records are address records that provide IP addresses for ns1.example.org. The resolver uses one or more of these IP addresses to query one of the domain's authoritative servers, which allows it to complete the DNS query. A common approach to reduce the burden on DNS servers is to cache the results of name resolution locally or on intermediary resolver hosts. Each DNS query result comes with

6111-408: The deployment of DNSSEC resolvers, since the root trust anchor can be used to validate any DNSSEC zone that has a complete chain of trust from the root. Since the chain of trust must be traced back to a trusted root without interruption in order to validate, trust anchors must still be configured for secure zones if any of the zones above them are not secure. For example, if the zone "signed.example.org"

6208-435: The existing old keys. Then, when it is safe to assume that the time to live values have caused the caching of old keys to have passed, these new keys can be used. Finally, when it is safe to assume that the caching of records using the old keys have expired, the old DNSKEY records can be deleted. This process is more complicated for things such as the keys to trust anchors, such as at the root, which may require an update of

6305-754: The first Unix name server implementation for the Berkeley Internet Name Domain, commonly referred to as BIND . In 1985, Kevin Dunlap of DEC substantially revised the DNS implementation. Mike Karels , Phil Almquist, and Paul Vixie then took over BIND maintenance. Internet Systems Consortium was founded in 1994 by Rick Adams , Paul Vixie , and Carl Malamud , expressly to provide a home for BIND development and maintenance. BIND versions from 4.9.3 onward were developed and maintained by ISC, with support provided by ISC's sponsors. As co-architects/programmers, Bob Halley and Paul Vixie released

6402-456: The first production-ready version of BIND version 8 in May 1997. Since 2000, over 43 different core developers have worked on BIND. In November 1987, RFC 1034 and RFC 1035 superseded the 1983 DNS specifications. Several additional Request for Comments have proposed extensions to the core DNS protocols. The domain name space consists of a tree data structure . Each node or leaf in the tree has

6499-447: The first to be able to sign their domains, beginning "early 2009". On June 23, 2010, 13 registrars were listed as offering DNSSEC records for .ORG domains. VeriSign ran a pilot project to allow .com and .net domains to register themselves for the purpose of NSEC3 experimentation. On February 24, 2009, they announced that they would deploy DNSSEC across all their top-level domains (.com, .net, etc.) within 24 months, and on November 16 of

6596-940: The information published by the zone owner and served on an authoritative DNS server. While protecting IP addresses is the immediate concern for many users, DNSSEC can protect any data published in the DNS, including text records (TXT) and mail exchange records (MX), and can be used to bootstrap other security systems that publish references to cryptographic certificates stored in the DNS such as Certificate Records ( CERT records , RFC   4398 ), SSH fingerprints ( SSHFP , RFC   4255 ), IPSec public keys (IPSECKEY, RFC   4025 ), TLS Trust Anchors ( TLSA , RFC   6698 ), or Encrypted Client Hello (SVCB/HTTPS records for ECH ). DNSSEC does not provide confidentiality of data; in particular, all DNSSEC responses are authenticated but not encrypted. DNSSEC does not protect against DoS attacks directly, though it indirectly provides some benefit (because signature checking allows

6693-408: The known threats to the DNS, and their solutions in DNSSEC. DNSSEC was designed to protect applications using DNS from accepting forged or manipulated DNS data, such as that created by DNS cache poisoning . All answers from DNSSEC protected zones are digitally signed . By checking the digital signature, a DNS resolver is able to check if the information is identical (i.e. unmodified and complete) to

6790-433: The length is only allowed to take 6 bits. The null label of length zero is reserved for the root zone. The full domain name may not exceed the length of 253 characters in its textual representation (or 254 with the trailing dot). In the internal binary representation of the DNS this maximum length of 253 requires 255 octets of storage, as it also stores the length of the first of many labels and adds last null byte. 255 length

6887-422: The local network. The client side of the DNS is called a DNS resolver. A resolver is responsible for initiating and sequencing the queries that ultimately lead to a full resolution (translation) of the resource sought, e.g., translation of a domain name into an IP address. DNS resolvers are classified by a variety of query methods, such as recursive , non-recursive , and iterative . A resolution process may use

6984-406: The name instead of listing them directly. Over time, advancements in hashing using GPUs and dedicated hardware meant that NSEC3 responses could be cheaply brute forced using offline dictionary attacks. NSEC5 has been proposed to allow authoritative servers to sign NSEC responses without having to keep a private key that can be used to modify the zone. Thus stealing an NSEC5KEY would only result in

7081-408: The name server and IP address. For example, if the authoritative name server for example.org is ns1.example.org, a computer trying to resolve www.example.org first resolves ns1.example.org. As ns1 is contained in example.org, this requires resolving example.org first, which presents a circular dependency. To break the dependency, the name server for the top level domain org includes glue along with

7178-409: The name server providing the delegation must also provide one or more IP addresses for the authoritative name server mentioned in the delegation. This information is called glue . The delegating name server provides this glue in the form of records in the additional section of the DNS response, and provides the delegation in the authority section of the response. A glue record is a combination of

7275-570: The networks and creating the Internet: Commercialization, privatization, broader access leads to the modern Internet: Examples of Internet services: The Domain Name System ( DNS ) is a hierarchical and distributed name service that provides a naming system for computers , services, and other resources on the Internet or other Internet Protocol (IP) networks. It associates various information with domain names ( identification strings ) assigned to each of

7372-489: The operating system. Keys in DNSKEY records can be used for two different things and typically different DNSKEY records are used for each. First, there are key signing keys (KSK) which are used to sign other DNSKEY records containing zone signing keys (ZSK), which are used to sign other records. Since the ZSKs are under complete control and use by one particular DNS zone , they can be switched more easily and more often. As

7469-432: The parent and children. This does mean that clients have to do a little more work when verifying keys. More specifically, verifying a DNS zone's KEY RRset requires two signature verification operations instead of the one required by RFC 2535 (there is no impact on the number of signatures verified for other types of RRsets). Most view this as a small price to pay, since it makes DNSSEC deployment more practical. The new version

7566-547: The primary file by contacting the SRI Network Information Center (NIC), directed by Feinler, via telephone during business hours. Later, Feinler set up a WHOIS directory on a server in the NIC for retrieval of information about resources, contacts, and entities. She and her team developed the concept of domains. Feinler suggested that domains should be based on the location of the physical address of

7663-402: The query completely by querying other name servers as needed. In typical operation, a client issues a recursive query to a caching recursive DNS server, which subsequently issues non-recursive queries to determine the answer and send a single answer back to the client. The resolver, or another DNS server acting recursively on behalf of the resolver, negotiates use of recursive service using bits in

7760-404: The query headers. DNS servers are not required to support recursive queries. The iterative query procedure is a process in which a DNS resolver queries a chain of one or more DNS servers. Each server refers the client to the next server in the chain, until the current server can fully resolve the request. For example, a possible resolution of www.example.com would query a global root server, then

7857-477: The registry's RDAP and WHOIS services. That data can be used to gain insight on, and track responsibility for, a given host on the Internet. Using a simpler, more memorable name in place of a host's numerical address dates back to the ARPANET era. The Stanford Research Institute (now SRI International ) maintained a text file named HOSTS.TXT that mapped host names to the numerical addresses of computers on

7954-597: The requested record type does not", which they call "DNS shotgun". The Internet is critical infrastructure, yet its operation depends on the fundamentally insecure DNS. Thus, there is strong incentive to secure DNS, and deploying DNSSEC is generally considered to be a critical part of that effort. For example, the U.S. National Strategy to Secure Cyberspace specifically identified the need to secure DNS. Wide-scale deployment of DNSSEC could resolve many other security problems as well, such as secure key distribution for e-mail addresses. DNSSEC deployment in large-scale networks

8051-482: The response as a "hint to find out whether the recursive name server was able to validate signatures for all of the data in the Answer and Authority sections of the response." Microsoft Windows uses a stub resolver, and Windows Server 2008 R2 and Windows 7 in particular use a non-validating but AD-bit-aware stub resolver. A validating stub resolver can also potentially perform its own signature validation by setting

8148-444: The root domain from Algorithm 8 to Algorithm 13 is currently in planning as of early 2024. DNS-based Authentication of Named Entities (DANE) is an IETF working group with the goal of developing protocols and techniques that allow Internet applications to establish cryptographically secured communications with TLS , DTLS , SMTP , and S/MIME based on DNSSEC. The new protocols will enable additional assurances and constraints for

8245-516: The root servers, and as a result, root name servers actually are involved in only a relatively small fraction of all requests. In theory, authoritative name servers are sufficient for the operation of the Internet. However, with only authoritative name servers operating, every DNS query must start with recursive queries at the root zone of the Domain Name System and each user system would have to implement resolver software capable of recursive operation. To improve efficiency, reduce DNS traffic across

8342-399: The same "tag" and many signatures corresponding to that "tag" in a packet, the researchers can slow down a resolver by a factor of 2 million. In response, resolvers began to place limits on the amount of verification errors, key tag collisions, and hash calculations. Cryptographically proving the absence of a domain requires signing the response to every query for a non-existent domain. This

8439-427: The same year, they said the .com and .net domains would be signed by the first quarter of 2011, after delays caused by technical aspects of the implementation. This goal was achieved on-schedule and Verisign's DNSSEC VP, Matt Larson, won InfoWorld's Technology Leadership Award for 2011 for his role in advancing DNSSEC. DNSSEC was first deployed at the root level on July 15, 2010. This is expected to greatly simplify

8536-519: The security algorithms that are or were most often used: From the results of a DNS lookup, a security-aware DNS resolver can determine whether the authoritative name server for the domain being queried supports DNSSEC, whether the answer it receives is secure, and whether there is some sort of error. The lookup procedure is different for recursive name servers such as those of many ISPs , and for stub resolvers such as those included by default in mainstream operating systems. Microsoft Windows uses

8633-629: The separate classes can be thought of as an array of parallel namespace trees. Administrative responsibility for any zone may be divided by creating additional zones. Authority over the new zone is said to be delegated to a designated name server. The parent zone ceases to be authoritative for the new zone. The definitive descriptions of the rules for forming domain names appear in RFC 1035, RFC 1123, RFC 2181, and RFC 5892. A domain name consists of one or more parts, technically called labels , that are conventionally concatenated , and delimited by dots, such as example.com. The right-most label conveys

8730-423: The servers referred to, and iteratively repeats this process until it receives an authoritative answer. The diagram illustrates this process for the host that is named by the fully qualified domain name "www.wikipedia.org". This mechanism would place a large traffic burden on the root servers, if every resolution on the Internet required starting at the root. In practice caching is used in DNS servers to off-load

8827-403: The signatures in all of its children). Thus, DNSSEC as defined in RFC 2535 could not scale up to the Internet. The IETF fundamentally modified DNSSEC, which is called DNSSEC-bis when necessary to distinguish it from the original DNSSEC approach of RFC 2535. This new version uses "delegation signer (DS) resource records" to provide an additional level of indirection at delegation points between

8924-499: The traditional model based on public key infrastructure . They will also enable domain holders to assert certificates for themselves, without reference to third-party certificate authorities . Support for DNSSEC stapled certificates was enabled in Google Chrome 14, but was later removed. For Mozilla Firefox , support was provided by an add-on while native support is currently awaiting someone to start working on it. DNS

9021-434: The use of potentially untrustworthy parties). Other standards (not DNSSEC) are used to secure bulk data (such as a DNS zone transfer ) sent between DNS servers. As documented in RFC   4367 , some users and developers make false assumptions about DNS names, such as assuming that a company's common name plus ".com" is always its domain name. DNSSEC cannot protect against false assumptions; it can only authenticate that

9118-604: The use of the Transmission Control Protocol (TCP) as well as numerous other protocol developments. An often-used analogy to explain the DNS is that it serves as the phone book for the Internet by translating human-friendly computer hostnames into IP addresses. For example, the hostname www.example.com within the domain name example.com translates to the addresses 93.184.216.34 ( IPv4 ) and 2606:2800:220:1:248:1893:25c8:1946 ( IPv6 ). The DNS can be quickly and transparently updated, allowing

9215-418: The user's Internet service provider or a public recursive name server , and the communication channels between itself and those name servers, using methods such as DNS over TLS . To be able to prove that a DNS answer is correct, one needs to know at least one key or DS record that is correct from sources other than the DNS. These starting points are known as trust anchors and are typically obtained with

9312-467: Was designed to avoid a single large central database. In addition, the DNS specifies the technical functionality of the database service that is at its core. It defines the DNS protocol, a detailed specification of the data structures and data communication exchanges used in the DNS, as part of the Internet protocol suite . The Internet maintains two principal namespaces , the domain name hierarchy and

9409-490: Was to create NSEC records for every pair of domains in a zone. Thus if a client queried for a record at the non-existent k.example.com , the server would respond with an NSEC record stating that nothing exists between a.example.com and z.example.com . However, this leaks more information about the zone than traditional unauthenticated NXDOMAIN errors because it exposes the existence of real domains. The NSEC3 records (RFC 5155) were created as an alternative which hashes

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