408 lines
17 KiB
Common Lisp
408 lines
17 KiB
Common Lisp
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(in-package :dns)
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;; 3.3. Standard RRs
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;; The following RR definitions are expected to occur, at least
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;; potentially, in all classes. In particular, NS, SOA, CNAME, and PTR
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;; will be used in all classes, and have the same format in all classes.
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;; Because their RDATA format is known, all domain names in the RDATA
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;; section of these RRs may be compressed.
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;; <domain-name> is a domain name represented as a series of labels, and
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;; terminated by a label with zero length. <character-string> is a single
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;; length octet followed by that number of characters. <character-string>
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;; is treated as binary information, and can be up to 256 characters in
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;; length (including the length octet).
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;; 3.3.11. NS RDATA format
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;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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;; / NSDNAME /
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;; / /
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;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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;; where:
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;; NSDNAME A <domain-name> which specifies a host which should be
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;; authoritative for the specified class and domain.
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;; NS records cause both the usual additional section processing to locate
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;; a type A record, and, when used in a referral, a special search of the
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;; zone in which they reside for glue information.
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;; The NS RR states that the named host should be expected to have a zone
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;; starting at owner name of the specified class. Note that the class may
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;; not indicate the protocol family which should be used to communicate
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;; with the host, although it is typically a strong hint. For example,
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;; hosts which are name servers for either Internet (IN) or Hesiod (HS)
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;; class information are normally queried using IN class protocols.
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;; 3.3.12. PTR RDATA format
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;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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;; / PTRDNAME /
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;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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;; where:
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;; PTRDNAME A <domain-name> which points to some location in the
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;; domain name space.
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;; PTR records cause no additional section processing. These RRs are used
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;; in special domains to point to some other location in the domain space.
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;; These records are simple data, and don't imply any special processing
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;; similar to that performed by CNAME, which identifies aliases. See the
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;; description of the IN-ADDR.ARPA domain for an example.
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;; 3.3.13. SOA RDATA format
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;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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;; / MNAME /
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;; / /
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;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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;; / RNAME /
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;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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;; | SERIAL |
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;; | |
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;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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;; | REFRESH |
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;; | |
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;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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;; | RETRY |
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;; | |
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;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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;; | EXPIRE |
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;; | |
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;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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;; | MINIMUM |
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;; | |
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;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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;; where:
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;; MNAME The <domain-name> of the name server that was the
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;; original or primary source of data for this zone.
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;; RNAME A <domain-name> which specifies the mailbox of the
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;; person responsible for this zone.
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;; SERIAL The unsigned 32 bit version number of the original copy
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;; of the zone. Zone transfers preserve this value. This
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;; value wraps and should be compared using sequence space
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;; arithmetic.
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;; REFRESH A 32 bit time interval before the zone should be
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;; refreshed.
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;; RETRY A 32 bit time interval that should elapse before a
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;; failed refresh should be retried.
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;; EXPIRE A 32 bit time value that specifies the upper limit on
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;; the time interval that can elapse before the zone is no
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;; longer authoritative.
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;; MINIMUM The unsigned 32 bit minimum TTL field that should be
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;; exported with any RR from this zone.
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;; SOA records cause no additional section processing.
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;; All times are in units of seconds.
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;; Most of these fields are pertinent only for name server maintenance
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;; operations. However, MINIMUM is used in all query operations that
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;; retrieve RRs from a zone. Whenever a RR is sent in a response to a
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;; query, the TTL field is set to the maximum of the TTL field from the RR
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;; and the MINIMUM field in the appropriate SOA. Thus MINIMUM is a lower
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;; bound on the TTL field for all RRs in a zone. Note that this use of
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;; MINIMUM should occur when the RRs are copied into the response and not
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;; when the zone is loaded from a master file or via a zone transfer. The
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;; reason for this provison is to allow future dynamic update facilities to
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;; change the SOA RR with known semantics.
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;; 3.3.14. TXT RDATA format
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;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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;; / TXT-DATA /
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;; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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;; where:
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;; TXT-DATA
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;; TXT RRs are used to hold descriptive text. The semantics of the text
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;; depends on the domain where it is found.
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(defbinary dns-header (:byte-order :big-endian)
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;; A 16 bit identifier assigned by the program that
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;; generates any kind of query. This identifier is copied
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;; the corresponding reply and can be used by the requester
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;; to match up replies to outstanding queries.
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(id 0 :type 16)
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;; A one bit field that specifies whether this message is a
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;; query (0), or a response (1).
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(qr 0 :type 1)
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;; A four bit field that specifies kind of query in this
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;; message. This value is set by the originator of a query
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;; and copied into the response. The values are:
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;;
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;; 0 a standard query (QUERY)
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;; 1 an inverse query (IQUERY)
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;; 2 a server status request (STATUS)
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;; 3-15 reserved for future use
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(opcode 0 :type 4)
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;; Authoritative Answer - this bit is valid in responses,
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;; and specifies that the responding name server is an
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;; authority for the domain name in question section.
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(aa nil :type 1)
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;; TrunCation - specifies that this message was truncated
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;; due to length greater than that permitted on the
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;; transmission channel.
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(tc nil :type 1)
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;; Recursion Desired - this bit may be set in a query and
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;; is copied into the response. If RD is set, it directs
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;; the name server to pursue the query recursively.
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;; Recursive query support is optional.
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(rd nil :type 1)
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;; Recursion Available - this be is set or cleared in a
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;; response, and denotes whether recursive query support is
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;; available in the name server.
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(ra nil :type 1)
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;; Reserved for future use. Must be zero in all queries and
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;; responses.
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(z 0 :type 3)
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;; Response code - this 4 bit field is set as part of
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;; responses. The values have the following
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;; interpretation:
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;; 0 No error condition
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;; 1 Format error - The name server was
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;; unable to interpret the query.
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;; 2 Server failure - The name server was
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;; unable to process this query due to a
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;; problem with the name server.
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;; 3 Name Error - Meaningful only for
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;; responses from an authoritative name
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;; server, this code signifies that the
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;; domain name referenced in the query does
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;; not exist.
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;; 4 Not Implemented - The name server does
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;; not support the requested kind of query.
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;; 5 Refused - The name server refuses to
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;; perform the specified operation for
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;; policy reasons. For example, a name
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;; server may not wish to provide the
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;; information to the particular requester,
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;; or a name server may not wish to perform
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;; a particular operation (e.g., zone
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;; transfer) for particular data.
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;; 6-15 Reserved for future use.
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(rcode 0 :type 4)
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;; an unsigned 16 bit integer specifying the number of
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;; entries in the question section.
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(qdcount 0 :type 16)
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;; an unsigned 16 bit integer specifying the number of
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;; resource records in the answer section.
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(ancount 0 :type 16)
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;; an unsigned 16 bit integer specifying the number of name
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;; server resource records in the authority records
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;; section.
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(nscount 0 :type 16)
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;; an unsigned 16 bit integer specifying the number of
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;; resource records in the additional records section.
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(arcount 0 :type 16))
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;; Representation of DNS QNAMEs.
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;;
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;; A QNAME can be either made up entirely of labels, which is
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;; basically a list of strings, or be terminated with a pointer to an
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;; offset within the original message.
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(deftype qname-field ()
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'(or
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;; pointer
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(unsigned-byte 14)
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;; label
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string))
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(defstruct qname
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(start-at 0 :type (unsigned-byte 14))
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(names #() :type (vector qname-field)))
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;; Domain names in questions and resource records are represented as a
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;; sequence of labels, where each label consists of a length octet
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;; followed by that number of octets.
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;;
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;; The domain name terminates with the zero length octet for the null
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;; label of the root. Note that this field may be an odd number of
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;; octets; no padding is used.
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(declaim (ftype (function (stream) (values qname integer)) read-qname))
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(defun read-qname (stream)
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"Reads a DNS QNAME from STREAM."
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(let ((start-at (file-position stream)))
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(iter (for byte next (read-byte stream))
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;; Each fragment is collected into this byte vector pre-allocated
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;; with the correct size.
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(for fragment = (make-array byte :element-type '(unsigned-byte 8)
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:fill-pointer 0))
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;; If the bit sequence (1 1) is encountered at the beginning of
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;; the fragment, a qname pointer is being read.
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(let ((byte-copy byte))
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(when (equal #b11 (lisp-binary/integer:pop-bits 2 8 byte-copy))
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(let ((next (read-byte stream)))
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(lisp-binary/integer:push-bits byte-copy 8 next)
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(collect next into fragments result-type vector)
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(sum 2 into size)
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(finish))))
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;; Total size is needed, count for each iteration byte, plus its
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;; own value.
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(sum (+ 1 byte) into size)
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(until (equal byte 0))
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;; On each iteration, this will interpret the current byte as an
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;; unsigned integer and read from STREAM an equivalent amount of
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;; times to assemble the current fragment.
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;;
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;; Advancing the stream like this also ensures that the next
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;; iteration occurs on a new fragment or the final terminating
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;; byte.
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(dotimes (_ byte (collect (babel:octets-to-string fragment)
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into fragments result-type vector))
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(vector-push (read-byte stream) fragment))
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(finally (return (values (make-qname :start-at start-at
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:names fragments)
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size))))))
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(declaim (ftype (function (stream qname)) write-qname))
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(defun write-qname (stream qname)
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"Write a DNS qname to STREAM."
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;; Write each fragment starting with its (byte-) length, followed by
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;; the bytes.
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(iter (for fragment in-vector (qname-names qname))
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(for bytes = (babel:string-to-octets fragment))
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(write-byte (length bytes) stream)
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(iter (for byte in-vector bytes)
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(write-byte byte stream)))
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;; Always finish off the serialisation with a null-byte!
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(write-byte 0 stream))
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(define-enum dns-type 2
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(:byte-order :big-endian)
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;; http://www.iana.org/assignments/dns-parameters/dns-parameters.xhtml
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(A 1)
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(NS 2)
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(CNAME 5)
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(SOA 6)
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(PTR 12)
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(MX 15)
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(TXT 16)
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(SRV 33)
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(AAAA 28)
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;; ANY typically wants SOA, MX, NS and MX
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(ANY 255))
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(defbinary dns-question (:byte-order :big-endian :export t)
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;; a domain name represented
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(qname "" :type (custom :lisp-type qname
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:reader #'read-qname
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:writer #'write-qname))
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;; a two octet code which specifies the type of the query.
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(qtype 0 :type dns-type)
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;; a two octet code that specifies the class of the query. For
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;; example, the QCLASS field is IN for the Internet.
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(qclass 0 :type 16))
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(defbinary dns-rr (:byte-order :big-endian :export t)
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(name nil :type (custom :lisp-type qname
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:reader #'read-qname
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:writer #'write-qname))
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;; two octets containing one of the RR type codes. This field
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;; specifies the meaning of the data in the RDATA field.
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(type 0 :type dns-type)
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;; two octets which specify the class of the data in the RDATA
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;; field.
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(class 0 :type 16)
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;; a 32 bit unsigned integer that specifies the time interval (in
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;; seconds) that the resource record may be cached before it should
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;; be discarded. Zero values are interpreted to mean that the RR
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;; can only be used for the transaction in progress, and should not
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;; be cached.
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(ttl 0 :type 32)
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;; an unsigned 16 bit integer that specifies the length in octets
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;; of the RDATA field.
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(rdlength 0 :type 16)
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;; a variable length string of octets that describes the resource.
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||
|
|
;; The format of this information varies according to the TYPE and
|
||
|
|
;; CLASS of the resource record. For example, the if the TYPE is A
|
||
|
|
;; and the CLASS is IN, the RDATA field is a 4 octet ARPA Internet
|
||
|
|
;; address.
|
||
|
|
(rdata #() :type (eval (case type
|
||
|
|
;; A 32-bit internet address in its
|
||
|
|
;; canonical representation of 4 integers.
|
||
|
|
((A) '(simple-array (unsigned-byte 8) (4)))
|
||
|
|
|
||
|
|
;; TODO(tazjin): Deal with multiple strings in single RRDATA
|
||
|
|
;; One or more <character-string>s.
|
||
|
|
((TXT) '(counted-string 1))
|
||
|
|
|
||
|
|
;; A <domain-name> which specifies the
|
||
|
|
;; canonical or primary name for the
|
||
|
|
;; owner. The owner name is an alias.
|
||
|
|
((CNAME) '(custom
|
||
|
|
:lisp-type qname
|
||
|
|
:reader #'read-qname
|
||
|
|
:writer #'write-qname))
|
||
|
|
|
||
|
|
;; A <domain-name> which specifies a host
|
||
|
|
;; which should be authoritative for the
|
||
|
|
;; specified class and domain.
|
||
|
|
((NS) '(custom
|
||
|
|
:lisp-type qname
|
||
|
|
:reader #'read-qname
|
||
|
|
:writer #'write-qname))
|
||
|
|
(otherwise `(simple-array (unsigned-byte 8) (,rdlength)))))))
|
||
|
|
|
||
|
|
(defbinary dns-message (:byte-order :big-endian :export t)
|
||
|
|
(header nil :type dns-header)
|
||
|
|
|
||
|
|
;; the question for the name server
|
||
|
|
(question #() :type (simple-array dns-question ((dns-header-qdcount header))))
|
||
|
|
|
||
|
|
;; ;; RRs answering the question
|
||
|
|
;; (answer #() :type (simple-array (unsigned-byte 8) (16)))
|
||
|
|
(answer #() :type (simple-array dns-rr ((dns-header-ancount header))))
|
||
|
|
|
||
|
|
;; ;; ;; RRs pointing toward an authority
|
||
|
|
(authority #() :type (simple-array dns-rr ((dns-header-nscount header))))
|
||
|
|
|
||
|
|
;; ;; RRs holding additional information
|
||
|
|
(additional #() :type (simple-array dns-rr ((dns-header-arcount header)))))
|