iquery
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As specified in RFC 1035std13 (section 6.4), the IQUERY operation for DNS
queries is used to look up the name(s) which are associated with the
given value. The value being sought is provided in the query ...
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Response packets from these megaservers could be exceptionally large,
and easily run into megabyte sizes. For example, using IQUERY to
find every domain that is delegated to one of the nameservers ...
... denial of service
attacks.
Operators of servers that do support IQUERY in some form (such as
very old BIND 4 servers) generally opt to disable it. This is
largely due to bugs in insufficiently-exercised code, or concerns
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... queries.
IQUERY is also somewhat inherently crippled by being unable to tell a
requester where it needs to go to get the information that was
requested. The answer is very specific to the single server ...
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No known clients use IQUERY to provide any meaningful service. The
only common reverse mapping support on the Internet ...
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Based on all of these factors, this document recommends that the
IQUERY operation for DNS servers be officially obsoleted.
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... 1035std13 is now considered obsolete. The
following is an applicability statement regarding the IQUERY opcode:
Inverse queries ...
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Inverse queries using the IQUERY opcode were originally described as
the ability to look up the names that are associated with a
particular Resource Record ...
... Resource Record (RR). Their implementation was optional
and never achieved widespread use. Therefore IQUERY is now obsolete,
and name servers SHOULD return a "Not Implemented" error when an
IQUERY ...
... IQUERY is now obsolete,
and name servers SHOULD return a "Not Implemented" error when an
IQUERY request is received.
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... authorization, it is highly unlikely
that removing support for IQUERY will open any new security holes.
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... security holes.
Note that if IQUERY is not obsoleted, securing the responses with DNS
Security (DNSSEC) is extremely difficult without out-on-the-fly
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The IQUERY opcode of 1 should be permanently retired, not to be
assigned to any future opcode.
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