9d2301cae2
This diff has been extracted from c2f7ccab0e
See https://github.com/ooni/probe/issues/2096
While there, export DecodeReply to decode a raw reply without
interpreting the Rcode or parsing the results, which seems a
nice extra feature to have to more flexibly parse DNS replies
in other parts of the codebase.
51 lines
1.6 KiB
Go
51 lines
1.6 KiB
Go
package netxlite
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import (
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"github.com/miekg/dns"
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"github.com/ooni/probe-cli/v3/internal/model"
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)
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// DNSEncoderMiekg uses github.com/miekg/dns to implement the Encoder.
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type DNSEncoderMiekg struct{}
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const (
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// dnsPaddingDesiredBlockSize is the size that the padded query should be multiple of
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dnsPaddingDesiredBlockSize = 128
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// dnsEDNS0MaxResponseSize is the maximum response size for EDNS0
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dnsEDNS0MaxResponseSize = 4096
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// dnsDNSSECEnabled turns on support for DNSSEC when using EDNS0
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dnsDNSSECEnabled = true
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)
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func (e *DNSEncoderMiekg) Encode(domain string, qtype uint16, padding bool) ([]byte, uint16, error) {
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question := dns.Question{
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Name: dns.Fqdn(domain),
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Qtype: qtype,
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Qclass: dns.ClassINET,
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}
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query := new(dns.Msg)
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query.Id = dns.Id()
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query.RecursionDesired = true
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query.Question = make([]dns.Question, 1)
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query.Question[0] = question
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if padding {
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query.SetEdns0(dnsEDNS0MaxResponseSize, dnsDNSSECEnabled)
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// Clients SHOULD pad queries to the closest multiple of
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// 128 octets RFC8467#section-4.1. We inflate the query
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// length by the size of the option (i.e. 4 octets). The
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// cast to uint is necessary to make the modulus operation
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// work as intended when the desiredBlockSize is smaller
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// than (query.Len()+4) ¯\_(ツ)_/¯.
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remainder := (dnsPaddingDesiredBlockSize - uint(query.Len()+4)) % dnsPaddingDesiredBlockSize
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opt := new(dns.EDNS0_PADDING)
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opt.Padding = make([]byte, remainder)
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query.IsEdns0().Option = append(query.IsEdns0().Option, opt)
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}
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data, err := query.Pack()
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return data, query.Id, err
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}
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var _ model.DNSEncoder = &DNSEncoderMiekg{}
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