84 lines
2.2 KiB
Go
84 lines
2.2 KiB
Go
package resolvers
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import (
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"time"
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"github.com/ameshkov/dnscrypt/v2"
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"github.com/miekg/dns"
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"github.com/sirupsen/logrus"
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)
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// DNSCryptResolver represents the config options for setting up a Resolver.
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type DNSCryptResolver struct {
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client *dnscrypt.Client
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server string
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resolverInfo *dnscrypt.ResolverInfo
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resolverOptions Options
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}
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// DNSCryptResolverOpts holds options for setting up a DNSCrypt resolver.
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type DNSCryptResolverOpts struct {
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UseTCP bool
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}
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// NewDNSCryptResolver accepts a list of nameservers and configures a DNS resolver.
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func NewDNSCryptResolver(server string, dnscryptOpts DNSCryptResolverOpts, resolverOpts Options) (Resolver, error) {
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net := "udp"
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if dnscryptOpts.UseTCP {
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net = "tcp"
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}
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client := &dnscrypt.Client{Net: net, Timeout: resolverOpts.Timeout, UDPSize: 4096}
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resolverInfo, err := client.Dial(server)
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if err != nil {
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return nil, err
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}
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return &DNSCryptResolver{
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client: client,
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resolverInfo: resolverInfo,
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server: resolverInfo.ServerAddress,
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resolverOptions: resolverOpts,
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}, nil
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}
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// Lookup takes a dns.Question and sends them to DNS Server.
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// It parses the Response from the server in a custom output format.
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func (r *DNSCryptResolver) Lookup(question dns.Question) (Response, error) {
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var (
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rsp Response
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messages = prepareMessages(question, r.resolverOptions.Ndots, r.resolverOptions.SearchList)
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)
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for _, msg := range messages {
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r.resolverOptions.Logger.WithFields(logrus.Fields{
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"domain": msg.Question[0].Name,
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"ndots": r.resolverOptions.Ndots,
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"nameserver": r.server,
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}).Debug("Attempting to resolve")
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now := time.Now()
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in, err := r.client.Exchange(&msg, r.resolverInfo)
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if err != nil {
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return rsp, err
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}
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rtt := time.Since(now)
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// pack questions in output.
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for _, q := range msg.Question {
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ques := Question{
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Name: q.Name,
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Class: dns.ClassToString[q.Qclass],
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Type: dns.TypeToString[q.Qtype],
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}
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rsp.Questions = append(rsp.Questions, ques)
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}
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// get the authorities and answers.
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output := parseMessage(in, rtt, r.server)
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rsp.Authorities = output.Authorities
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rsp.Answers = output.Answers
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if len(output.Answers) > 0 {
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// stop iterating the searchlist.
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break
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}
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}
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return rsp, nil
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}
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