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spf: Support the "ptr" mechanism

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The "ptr" mechanism should not be used, but unfortunately many domains
still do.

This patch extends our SPF implementation to support checking it.

https://tools.ietf.org/html/rfc7208#section-5.5
This commit is contained in:
Alberto Bertogli
2016-10-22 00:07:07 +01:00
parent c00648b4ae
commit 38b4e76090
2 changed files with 94 additions and 8 deletions
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49
internal/spf/spf.go
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@@ -11,7 +11,6 @@
//
// Not supported (return Neutral if used):
// - "exists".
// - "ptr".
// - "exp".
// - Macros.
//
@@ -30,9 +29,10 @@ import (
// Functions that we can override for testing purposes.
var (
lookupTXT = net.LookupTXT
lookupMX = net.LookupMX
lookupIP = net.LookupIP
lookupTXT = net.LookupTXT
lookupMX = net.LookupMX
lookupIP = net.LookupIP
lookupAddr = net.LookupAddr
)
// Results and Errors. Note the values have meaning, we use them in headers.
@@ -81,13 +81,16 @@ var QualToResult = map[byte]Result{
// with a given identity.
// Reference: https://tools.ietf.org/html/rfc7208#section-4
func CheckHost(ip net.IP, domain string) (Result, error) {
r := &resolution{ip, 0}
r := &resolution{ip, 0, nil}
return r.Check(domain)
}
type resolution struct {
ip net.IP
count uint
// Result of doing a reverse lookup for ip (so we only do it once).
ipNames []string
}
func (r *resolution) Check(domain string) (Result, error) {
@@ -167,10 +170,12 @@ func (r *resolution) Check(domain string) (Result, error) {
if ok, res, err := r.ipField(result, field); ok {
return res, err
}
} else if strings.HasPrefix(field, "ptr") {
if ok, res, err := r.ptrField(result, field, domain); ok {
return res, err
}
} else if strings.HasPrefix(field, "exists") {
return Neutral, fmt.Errorf("'exists' not supported")
} else if strings.HasPrefix(field, "ptr") {
return Neutral, fmt.Errorf("'ptr' not supported")
} else if strings.HasPrefix(field, "exp=") {
return Neutral, fmt.Errorf("'exp' not supported")
} else if strings.HasPrefix(field, "redirect=") {
@@ -246,6 +251,36 @@ func (r *resolution) ipField(res Result, field string) (bool, Result, error) {
return false, "", nil
}
// ptrField processes a "ptr" field.
func (r *resolution) ptrField(res Result, field, domain string) (bool, Result, error) {
// Extract the domain if the field is in the form "ptr:domain"
if len(field) >= 4 {
domain = field[4:]
}
if r.ipNames == nil {
r.count++
n, err := lookupAddr(r.ip.String())
if err != nil {
// https://tools.ietf.org/html/rfc7208#section-5
if isTemporary(err) {
return true, TempError, err
}
return false, "", err
}
r.ipNames = n
}
for _, n := range r.ipNames {
if strings.HasSuffix(n, domain+".") {
return true, res, fmt.Errorf("matched ptr:%s", domain)
}
}
return false, "", nil
}
// includeField processes an "include" field.
func (r *resolution) includeField(res Result, field string) (bool, Result, error) {
// https://tools.ietf.org/html/rfc7208#section-5.2