example.com ) called mail.example.com . This server either has three interfaces, or there are three servers with (in this case) consecutive IP addresses. A mail client will query for the MX record, which returns the server FQDN mail.example.com . It then queries for the address record(s) for the FQDN returned in the MX response, which returns the three IPv4 addresses shown. Some problems with this approach are: If there are multiple answers of the same type in a DNS response, clients typically (but not always) choose the answer that comes first. If answers were always given in the same order this would place undue strain on that server, leaving the rest idle. However, most DNS software will return multiple answers in a random order ( BIND does this by default, though it can be changed in configuration), which will help with fairness of traffic distribution. Sometimes clients do

CVE:   CVE-2017-3141 Document version:  2.0 Posting date:  14 Jun 2017 Program impacted:   BIND Versions affected:  9.2.6-P2->9.2.9, 9.3.2-P1->9.3.6, 9.4.0->9.8.8, 9.9.0->9.9.10, 9.10.0->9.10.5, 9.11.0->9.11.1, 9.9.3-S1->9.9.10-S1, 9.10.5-S1 Severity:  Critical Exploitable:  Locally Description: The BIND installer on Windows uses an unquoted service path, which can enable a local user to achieve privilege escalation if the host file system permissions allow this. Impact: This vulnerability exists in the installer delivered with BIND for Windows and not within BIND itself. Non-Windows builds and installations are unaffected. A manual installation of BIND where the service path is quoted when added would not be at risk. CVSS Score: 7.2 CVSS Vector: CVSS

Buffer overflow in nslookupComplain function in BIND 4 allows remote attackers to gain root privileges CVE:  [CVE-2001-0011](http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2001-0011) CERT:  [VU#572183](http://www.kb.cert.org/vuls/id/572183) Posting date:  29 Jan 2001 Program Impacted:  [BIND](https://www.isc.org/software/bind) Versions affected:  4.9.3 - 4.9.7 Severity:  Serious Exploitable:  Remotely Description:  A buffer overflow exists in the nslookupComplain() routine. The vulnerable buffer is a locally defined character array used to build an error message intended for syslog. Attackers attempting to exploit this vulnerability could do so by sending a specially formatted DNS query to affected BIND servers. If properly constructed, this query could be used to disrupt the normal operation of the DNS server process, resulting in either denial of service or the execution of arbitrary code. If an attacker were able

Uma pergunta especialmente construida enviada ao BIND pode provocar uma terminação anómala (crash) CVE:   CVE-2013-4854 Versão do documento: 2.0 Data de publicação:  26 Julho 2013 Programa afetado:   BIND Versões afetadas:  Open source: 9.7.0->9.7.7, 9.8.0->9.8.5-P1, 9.9.0->9.9.3-P1, 9.8.6b1 and 9.9.4b1; Subscription: 9.9.3-S1 and 9.9.4-S1b1 Gravidade:  Critica Exploração:  Remotamente Descrição: Uma pergunta especialmente construída que inclui rdata inválida pode provocar uma terminação anómala (crash) do named com uma falha de asserção ao rejeitar a pergunta. O BIND 9.6-ESV não está afetado por este problema. As versões de BIND anteriores ao 9.6 pensa-se que não estão afetadas mas essas versões estão em "fim de vida" (EOL) e não são testadas e a ISC não gera soluções aos problemas de segurança

Is it possible to enable the audit logs on BIND so we can track changes performed at the DNS records level (Add/Delete/Modify A,MX,NS, records)? You can get that by default, depending on how the changes were performed. If you use nsupdate or some other dynamic DNS UPDATE client, named will log changes like this: 08-Jan-2019 11:55:09.826 update: info: client @0x55b747f47ec0 ::1#5685/key local-ddns: updating zone 'private.cam.ac.uk/IN': adding an RR at 'private.cam.ac.uk' SOA primary.dns.cam.ac.uk. hostmaster.cam.ac.uk. 1546948509 1800 900 604800 3600 08-Jan-2019 11:55:09.826 update: info: client @0x55b747f47ec0 ::1#5685/key local-ddns: updating zone 'private.cam.ac.uk/IN': adding an RR at 'QQQQ.lcil.private.cam.ac.uk' A 172.22.QQ.QQ The changes are also recorded in the zone

Like many basic Internet protocols, DHCP was not originally designed with a robust security model, but was designed for simplicity of implementation and ease of deployment. Care should be taken in networks that use DHCP to avoid common security pitfalls. Problem 1: Rogue DHCP Servers A substantial part of the appeal of DHCP is that clients joining a network require no a priori knowledge of the network. They advertise (via a DHCPDISCOVER packet) to find a DHCP server and, assuming all goes well, receive their configuration information from that server and join the network as fully functioning clients. While this is very desirable behavior as far as ease of deployment is concerned, from a security standpoint it is problematic that client machines, having no pre-existing knowledge of the network, cannot distinguish between a response from a server which is authorized by the network's administrator and another machine which

BIND 9の深刻な欠陥により、攻撃者が、named、およびlibdnsをリンクする他のプラグラムのメモリを過大に消費させることが可能となります。 CVE:  CVE-2013-2266 文書バージョン:               2.0 公開日付:  2013年3月26日 影響を受けるプログラム:  BIND 影響を受けるバージョン:  BIND 9.7.x, 9.8.0 から 9.8.5b1, 9.9.0 から 9.9.3b1(いずれも"Unix"版のみ。Windows版は影響を受けない。9.7.0より前のバージ

Title: Heavy DNSSEC Validation Load Can Cause a "Bad Cache" Assertion Failure in BIND 9 Summary: High numbers of queries with DNSSEC validation enabled can cause an assertion failure in named , caused by using a "bad cache" data structure before it has been initialized. CVE: CVE-2012-3817 Document version: 2.3 Posting date: 24 July, 2012 Program impacted: BIND 9 Versions affected: 9.6-ESV through 9.6-ESV-R7-P1; 9.7.1 through 9.7.6-P1; 9.8.0 through 9.8.3-P1; 9.9.0 through 9.9.1-P1. Severity:  Critical Exploitable:  Remotely Description: BIND 9 stores a cache of query names that are known to be failing due to misconfigured name servers or a broken chain of trust. Under high query loads when DNSSEC validation is active, it is possible for a condition to arise in which data from this cache of

the PARTNER-DOWN state. You can put the server into the PARTNER-DOWN state either by using the omshell (1) command or by stopping the server, editing the last failover state declaration in the lease file, and restarting the server. If you use this last method, change the "my state" line to: failover peer name state { my state partner-down;. peer state state at date ; } It is only required to change "my state" as shown above. When the other server comes back online, it should automatically detect that it has been offline and request a complete update from the server that was running in the PARTNER-DOWN state, and then both servers will resume processing together. It is possible to get into a dangerous situation: if you put one server into the PARTNER-DOWN state, and then *that* server goes down, and the other server comes back up, the other

The way that clients (receiving their IPs via DHCP) or DHCP servers (handing out IP addresses) know which server to send DDNS updates to is by querying DNS for the SOA record of the domain to which the dynamic update should be made. By default, dynamic updates are sent to the primary server in the mname field of the SOA record for the zone. If using nsupdate manually or using scripting techniques, you can specify the server to which dynamic updates should be sent. Most DHCP servers (including ISC DHCP) also have configuration options for this. If a secondary for a zone receives a DDNS update for a zone for which it is authoritative, it will not update its zone data directly. It will either discard it, or it will forward it to the primary. To make the secondary forward the DDNS update, you need to configure allow-update-forwarding

BIND 9.10 is EOL This article provides information about a branch of BIND which has reached End of Life (EOL), i.e. for which support and development efforts are no longer provided by ISC. Response-rate limiting (DNS RRL) is now available by default ISC introduced the Response Rate Limiter into earlier versions of BIND as a configurable option. It was not automatically available. RRL has proven to be so valuable and effective that it is now included in the default software-build configuration, which means that you can use RRL without having to configure and create a custom version of BIND. Instructions for using RRL are in Using the Response Rate Limiting Feature  and (in somewhat more detail) in the BIND 9.10 ARM. New format option "map" for zone files stored on disk, allowing substantially faster zone loading DNS zones are stored in the host server's

Security Vulnerability Disclosure Policy . This Knowledgebase article is the complete and official security advisory document. Legal Disclaimer: Internet Systems Consortium (ISC) is providing this notice on an "AS IS" basis. No warranty or guarantee of any kind is expressed in this notice and none should be implied. ISC expressly excludes and disclaims any warranties regarding this notice or materials referred to in this notice, including, without limitation, any implied warranty of merchantability, fitness for a particular purpose, absence of hidden defects, or of non-infringement. Your use or reliance on this notice or materials referred to in this notice is at your own risk. ISC may change this notice at any time.  A stand-alone copy or paraphrase of the text of this document that omits the document URL is an uncontrolled copy. Uncontrolled copies may lack important information, be out of date, or contain factual errors.

特別に細工されたクエリによってBINDネームサーバがクラッシュ（異常終了）する CVE: CVE-2013-4854 文書バージョン: 2.0 公開日付: 2013年7月26日 影響を受けるプログラム: BIND 影響を受けるバージョン: オープンソース版: 9.7.0から9.7.7, 9.8.0から9.8.5-P1, 9.9.0から9.9.3-P1, 9.8.6b1 および 9.9.4b1。サブスクリプション版: 9.9.3-S1 および 9.9.4-S1b1。 深刻度: 重大(Critical

What is classification anyway? Client classification helps with differentiating between clients. It can be used to change the behavior of many parts of the DHCP message processing: subnet selection pool selection lease limiting rate limiting DDNS tuning dropping queries definition of DHCPv4 private (codes 224-254) and code 43 options assignment of different options for DHCPv4 cable modems, the setting of specific options for use with the TFTP server address and the boot file field What are template classes? Template classes are a special type of classes that can spawn an indefinite number of regular classes using a single class definition. That makes it an efficient way of configuring multiple classes. The spawned classes need to be mentioned in other parts of the configuration in order to make effective use of them. Template classes don't make it easier for the spawned classes to be referenced. That part of the

print-severity yes; severity info; }; # This channel is dynamic so that when the debug level is increased using # rndc while the server is running, extra information will be logged about # failing queries. Other debug information for other categories will be # sent to the channel default_debug (which is also dynamic), but without # affecting the regular logging. channel query-errors_log { file "/var/named/log/query-errors" versions 5 size 20m; print-time yes; print-category yes; print-severity yes; severity dynamic; }; # This is the default syslog channel, defined here for clarity. You don’t # have to use it if you prefer to log to your own channels. # It sends to syslog’s daemon facility, and sends only logged messages # of priority info and higher. # (The options to print time, category and severity are non-default.) channel default_syslog { print-time yes; print-category yes; print-severity yes; syslog daemon

network failure that breaks the connection will not result in the servers being out of communication for a long time, but large enough that the server isn’t constantly making and breaking connections. This parameter must be specified. The max-unacked-updates statement max-unacked-updates count ; The max-unacked-updates statement tells the remote DHCP server how many BNDUPD messages it can send before it receives a BNDACK from the local system. We don’t have enough operational experience to say what a good value for this is, but 10 seems to work. This parameter must be specified. The mclt statement mclt seconds ; The mclt statement defines the Maximum Client Lead Time. It must be specified on the primary, and may not be specified on the secondary. This is the length of time for which a lease may be renewed by either failover peer without contacting the other

to be placed in the netadmins group as well. This may change in a future release of Stork. User Access Optionally, you can limit Stork logins to a particular LDAP group. STORK_SERVER_HOOK_LDAP_GROUP_ALLOW If defined, Stork login will be allowed only for members of the specified LDAP group. You must provide the Common Name of the group (without CN= prefix). Use this if not all LDAP users should be permitted login to Stork. For example, if you have an LDAP group netadmins , you might specify that here, and then only your network admins will be able to login to Stork. This is independent of the group mapping feature ( MAP_GROUPS ). You can restrict Stork login without mapping Stork roles. You can map Stork roles without restricting Stork login. However, it often makes the most sense to use both features together. Group Mapping Optionally, you can

Title:  Memory Leaks Found In ISC DHCP Summary: Two memory leaks have been found and fixed in ISC DHCP. Both are reproducible when running in DHCPv6 mode (with the -6 command-line argument.) The first leak is confirmed to only affect servers operating in DHCPv6 mode, but based on initial code analysis the second may theoretically affect DHCPv4 servers (though this has not been demonstrated.) CVE:   CVE-2012-3954 Document Version:  2.1 Posting date:  24 July 2012 Program Impacted:   ISC DHCP 4 Versions affected:  4.1.x, 4.2.x Severity:  Medium Exploitable:  From networks permitted to send requests to the DHCP server. Description: ISC has discovered and fixed two memory leaks in the DHCP code. One of the leaks only affects servers running in DHCPv6 mode. The other is known to affect a server running in DHCPv6 mode but could potentially occur on servers running in DHCPv4 mode

'secret' value must not be base64 encoded, which is different from how the value appears in the dhcpd.conf file. dhcpctl_new_object() creates a local handle for an object on the server. The “object_type” parameter is the ascii name of the type of object being accessed. e.g. "lease". This function only sets up local data struc‐ tures, it does not queue any messages to be sent to the remote side, dhcpctl_open_object() does that. dhcpctl_open_object() builds and queues the request to the remote side. This function is used with handle created via dhcpctl_new_object() . The flags argument is a bit mask with the following values available for set‐ ting: DHCPCTL_CREATE if the object does not exist then the remote will create it DHCPCTL_UPDATE update the object on the remote side using the attributes already set in the handle. DHCPCTL_EXCL

If you are having issues with performance on BIND 9.10.0 to 9.10.3, please see the article  prefetch performance in BIND 9.10 A DNS resolver (recursive server) looks up information for its clients. When it finds an answer, it keeps a copy cached locally in addition to returning the answer to the requesting client. This ensures that if another request for the same information arrives, the resolver can just send another copy of the reply. Every DNS record specifies a TTL, or Time-To-Live value. It is specified in seconds, and if that many seconds have elapsed after the record was sent from its authoritative server, clients and resolvers must delete their saved copy. If you monitor DNS traffic at a busy site, you will see TTL values ranging from a few seconds to a few days. The most common TTL values that we see