mirror of
https://github.com/StackExchange/dnscontrol.git
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Initial DNS Resolvers and SPF scaffolding (#123)
* Implemented Live and Preloaded resolvers * Integrated Craig's parser.
This commit is contained in:
Tom Limoncelli
GitHub
parent
20253130cf
commit
01a242480c
7 changed files with 398 additions and 0 deletions
64
cmd/spftest/main.go
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64
cmd/spftest/main.go
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@ -0,0 +1,64 @@
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package main
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import (
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"fmt"
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"strings"
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"github.com/StackExchange/dnscontrol/dnsresolver"
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"github.com/StackExchange/dnscontrol/spflib"
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)
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func main() {
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h := dnsresolver.NewResolverLive("spf-store.json")
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fmt.Println(h.GetTxt("_spf.google.com"))
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fmt.Println(h.GetTxt("spf-basic.fogcreek.com"))
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h.Close()
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i, err := dnsresolver.NewResolverPreloaded("spf-store.json")
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if err != nil {
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panic(err)
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}
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fmt.Println(i.GetTxt("_spf.google.com"))
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fmt.Println(i.GetTxt("spf-basic.fogcreek.com"))
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fmt.Println(i.GetTxt("wontbefound"))
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fmt.Println()
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fmt.Println("---------------------")
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fmt.Println()
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res := dnsresolver.NewResolverLive("preload-dns.json")
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//res := dnsresolver.NewResolverPreloaded("preload-dns.json")
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rec, err := spflib.Parse(strings.Join([]string{"v=spf1",
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"ip4:198.252.206.0/24",
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"ip4:192.111.0.0/24",
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"include:_spf.google.com",
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"include:mailgun.org",
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"include:spf-basic.fogcreek.com",
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"include:mail.zendesk.com",
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"include:servers.mcsv.net",
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"include:sendgrid.net",
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"include:spf.mtasv.net",
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"~all"}, " "), res)
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if err != nil {
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panic(err)
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}
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spflib.DumpSPF(rec, "")
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fmt.Println()
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fmt.Println("---------------------")
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fmt.Println()
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var spfs []string
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spfs, err = spflib.Lookup("stackex.com", res)
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if err != nil {
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panic(err)
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}
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rec, err = spflib.Parse(strings.Join(spfs, " "), res)
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if err != nil {
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panic(err)
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}
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spflib.DumpSPF(rec, "")
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}
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28
dnsresolver/dnscache.go
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28
dnsresolver/dnscache.go
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@ -0,0 +1,28 @@
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package dnsresolver
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// dnsCache implements a very simple DNS cache.
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// It caches the entire answer (i.e. all TXT records), filtering
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// out the non-SPF answers is done at a higher layer.
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// At this time the only rtype is "TXT". Eventually we'll need
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// to cache A/AAAA/CNAME records to to CNAME flattening.
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type dnsCache map[string]map[string][]string // map[fqdn]map[rtype] -> answers
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func (c dnsCache) get(label, rtype string) ([]string, bool) {
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v1, ok := c[label]
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if !ok {
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return nil, false
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}
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v2, ok := v1[rtype]
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if !ok {
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return nil, false
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}
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return v2, true
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}
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func (c dnsCache) put(label, rtype string, answers []string) {
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_, ok := c[label]
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if !ok {
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c[label] = make(map[string][]string)
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}
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c[label][rtype] = answers
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}
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31
dnsresolver/dnscache_test.go
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31
dnsresolver/dnscache_test.go
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package dnsresolver
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import "testing"
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func TestDnsCache(t *testing.T) {
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cache := &dnsCache{}
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cache.put("one", "txt", []string{"a", "b", "c"})
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cache.put("two", "txt", []string{"d", "e", "f"})
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a, b := cache.get("one", "txt")
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if !(b == true && len(a) == 3 && a[0] == "a" && a[1] == "b" && a[2] == "c") {
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t.Errorf("one-txt didn't work")
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}
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a, b = cache.get("two", "txt")
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if !(b == true && len(a) == 3 && a[0] == "d" && a[1] == "e" && a[2] == "f") {
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t.Errorf("one-txt didn't work")
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}
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a, b = cache.get("three", "txt")
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if !(b == false) {
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t.Errorf("three-txt didn't work")
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}
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a, b = cache.get("two", "not")
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if !(b == false) {
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t.Errorf("two-not didn't work")
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}
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}
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83
dnsresolver/resolver.go
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83
dnsresolver/resolver.go
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@ -0,0 +1,83 @@
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package dnsresolver
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import (
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"encoding/json"
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"io/ioutil"
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"net"
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"github.com/pkg/errors"
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)
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// This file includes all the DNS Resolvers used by package spf.
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// DnsResolver looks up txt strings associated with a FQDN.
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type DnsResolver interface {
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GetTxt(string) ([]string, error) // Given a DNS label, return the TXT values records.
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}
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// The "Live DNS" Resolver:
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type dnsLive struct {
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filename string
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cache dnsCache
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}
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func NewResolverLive(filename string) *dnsLive {
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// Does live DNS lookups. Records them. Writes file on Close.
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c := &dnsLive{filename: filename}
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c.cache = dnsCache{}
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return c
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}
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func (c *dnsLive) GetTxt(label string) ([]string, error) {
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// Try the cache.
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txts, ok := c.cache.get(label, "txt")
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if ok {
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return txts, nil
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}
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// Populate the cache:
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t, err := net.LookupTXT(label)
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if err == nil {
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c.cache.put(label, "txt", t)
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}
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return t, err
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}
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func (c *dnsLive) Close() {
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// Write out and close the file.
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m, _ := json.MarshalIndent(c.cache, "", " ")
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m = append(m, "\n"...)
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ioutil.WriteFile(c.filename, m, 0666)
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}
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// The "Pre-Cached DNS" Resolver:
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type dnsPreloaded struct {
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cache dnsCache
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}
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func NewResolverPreloaded(filename string) (*dnsPreloaded, error) {
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c := &dnsPreloaded{}
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c.cache = dnsCache{}
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j, err := ioutil.ReadFile(filename)
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if err != nil {
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return nil, err
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}
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err = json.Unmarshal(j, &(*c).cache)
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return c, err
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}
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func (c *dnsPreloaded) DumpCache() dnsCache {
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return c.cache
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}
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func (c *dnsPreloaded) GetTxt(label string) ([]string, error) {
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// Try the cache.
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txts, ok := c.cache.get(label, "txt")
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if ok {
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return txts, nil
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}
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return nil, errors.Errorf("No preloaded DNS entry for: %#v", label)
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}
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98
spflib/parse.go
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98
spflib/parse.go
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package spflib
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import (
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"fmt"
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"strings"
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"github.com/StackExchange/dnscontrol/dnsresolver"
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)
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type SPFRecord struct {
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Lookups int
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Parts []*SPFPart
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}
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type SPFPart struct {
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Text string
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Lookups int
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IncludeRecord *SPFRecord
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}
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func Lookup(target string, dnsres dnsresolver.DnsResolver) ([]string, error) {
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txts, err := dnsres.GetTxt(target)
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if err != nil {
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return nil, err
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}
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var result []string
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for _, txt := range txts {
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if strings.HasPrefix(txt, "v=spf1 ") {
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result = append(result, txt)
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}
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}
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return result, nil
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}
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func Parse(text string, dnsres dnsresolver.DnsResolver) (*SPFRecord, error) {
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if !strings.HasPrefix(text, "v=spf1 ") {
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return nil, fmt.Errorf("Not an spf record")
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}
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parts := strings.Split(text, " ")
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rec := &SPFRecord{}
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for _, part := range parts[1:] {
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p := &SPFPart{Text: part}
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rec.Parts = append(rec.Parts, p)
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if part == "~all" || part == "-all" || part == "?all" {
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//all. nothing else matters.
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break
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} else if strings.HasPrefix(part, "ip4:") || strings.HasPrefix(part, "ip6:") {
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//ip address, 0 lookups
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continue
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} else if strings.HasPrefix(part, "include:") {
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rec.Lookups++
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includeTarget := strings.TrimPrefix(part, "include:")
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subRecord, err := resolveSPF(includeTarget, dnsres)
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if err != nil {
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return nil, err
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}
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p.IncludeRecord, err = Parse(subRecord, dnsres)
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if err != nil {
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return nil, fmt.Errorf("In included spf: %s", err)
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}
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rec.Lookups += p.IncludeRecord.Lookups
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} else {
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return nil, fmt.Errorf("Unsupported spf part %s", part)
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}
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}
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return rec, nil
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}
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// DumpSPF outputs an SPFRecord and related data for debugging purposes.
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func DumpSPF(rec *SPFRecord, indent string) {
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fmt.Printf("%sTotal Lookups: %d\n", indent, rec.Lookups)
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fmt.Print(indent + "v=spf1")
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for _, p := range rec.Parts {
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fmt.Print(" " + p.Text)
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}
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fmt.Println()
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indent += "\t"
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for _, p := range rec.Parts {
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if p.IncludeRecord != nil {
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fmt.Println(indent + p.Text)
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DumpSPF(p.IncludeRecord, indent+"\t")
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}
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}
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}
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func resolveSPF(target string, dnsres dnsresolver.DnsResolver) (string, error) {
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recs, err := dnsres.GetTxt(target)
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if err != nil {
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return "", err
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}
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for _, r := range recs {
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if strings.HasPrefix(r, "v=spf1 ") {
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return r, nil
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}
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}
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return "", fmt.Errorf("No SPF records found for %s", target)
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}
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30
spflib/parse_test.go
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30
spflib/parse_test.go
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package spflib
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import (
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"strings"
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"testing"
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"github.com/StackExchange/dnscontrol/dnsresolver"
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)
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func TestParse(t *testing.T) {
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dnsres, err := dnsresolver.NewResolverPreloaded("testdata-dns1.json")
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if err != nil {
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t.Fatal(err)
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}
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rec, err := Parse(strings.Join([]string{"v=spf1",
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"ip4:198.252.206.0/24",
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"ip4:192.111.0.0/24",
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"include:_spf.google.com",
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"include:mailgun.org",
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"include:spf-basic.fogcreek.com",
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"include:mail.zendesk.com",
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"include:servers.mcsv.net",
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"include:sendgrid.net",
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"include:spf.mtasv.net",
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"~all"}, " "), dnsres)
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if err != nil {
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t.Fatal(err)
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}
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DumpSPF(rec, "")
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}
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64
spflib/testdata-dns1.json
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64
spflib/testdata-dns1.json
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{
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"_netblocks.google.com": {
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"txt": [
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"v=spf1 ip4:64.18.0.0/20 ip4:64.233.160.0/19 ip4:66.102.0.0/20 ip4:66.249.80.0/20 ip4:72.14.192.0/18 ip4:74.125.0.0/16 ip4:108.177.8.0/21 ip4:173.194.0.0/16 ip4:207.126.144.0/20 ip4:209.85.128.0/17 ip4:216.58.192.0/19 ip4:216.239.32.0/19 ~all"
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]
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},
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"_netblocks2.google.com": {
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"txt": [
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"v=spf1 ip6:2001:4860:4000::/36 ip6:2404:6800:4000::/36 ip6:2607:f8b0:4000::/36 ip6:2800:3f0:4000::/36 ip6:2a00:1450:4000::/36 ip6:2c0f:fb50:4000::/36 ~all"
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]
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},
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"_netblocks3.google.com": {
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"txt": [
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"v=spf1 ip4:172.217.0.0/19 ip4:108.177.96.0/19 ~all"
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]
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},
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"_spf.google.com": {
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"txt": [
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"v=spf1 include:_netblocks.google.com include:_netblocks2.google.com include:_netblocks3.google.com ~all"
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]
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},
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"mail.zendesk.com": {
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"txt": [
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"v=spf1 ip4:192.161.144.0/20 ip4:185.12.80.0/22 ip4:96.46.150.192/27 ip4:174.137.46.0/24 ip4:188.172.128.0/20 ip4:216.198.0.0/18 ~all"
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]
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},
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"mailgun.org": {
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"txt": [
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"google-site-verification=FIGVOKZm6lQFDBJaiC2DdwvBy8TInunoGCt-1gnL4PA",
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"v=spf1 include:spf1.mailgun.org include:spf2.mailgun.org ~all"
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]
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},
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"sendgrid.net": {
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"txt": [
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"google-site-verification=NxyooVvVaIgddVa23KTlOEuVPuhffcDqJFV8RzWrAys",
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"v=spf1 ip4:167.89.0.0/17 ip4:208.117.48.0/20 ip4:50.31.32.0/19 ip4:198.37.144.0/20 ip4:198.21.0.0/21 ip4:192.254.112.0/20 ip4:168.245.0.0/17 ~all"
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]
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},
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"servers.mcsv.net": {
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"txt": [
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"v=spf1 ip4:205.201.128.0/20 ip4:198.2.128.0/18 ip4:148.105.8.0/21 ?all"
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]
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},
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"spf-basic.fogcreek.com": {
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"txt": [
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"v=spf1 ip4:64.34.80.172 -all"
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]
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},
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"spf.mtasv.net": {
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"txt": [
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"v=spf1 ip4:50.31.156.96/27 ip4:104.245.209.192/26 ~all"
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]
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},
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"spf1.mailgun.org": {
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"txt": [
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"v=spf1 ip4:173.193.210.32/27 ip4:50.23.218.192/27 ip4:174.37.226.64/27 ip4:208.43.239.136/30 ip4:184.173.105.0/24 ip4:184.173.153.0/24 ip4:104.130.122.0/23 ip4:146.20.112.0/26 ~all"
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]
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},
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"spf2.mailgun.org": {
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"txt": [
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"v=spf1 ip4:209.61.151.0/24 ip4:166.78.68.0/22 ip4:198.61.254.0/23 ip4:192.237.158.0/23 ip4:23.253.182.0/23 ip4:104.130.96.0/28 ip4:146.20.113.0/24 ip4:146.20.191.0/24 ~all"
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]
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}
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}
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