mox!

dmarc/txt.go

@@ -0,0 +1,127 @@
+package dmarc
+
+import (
+	"fmt"
+	"strings"
+)
+
+// todo: DMARCPolicy should be named just Policy, but this is causing conflicting types in sherpadoc output. should somehow get the dmarc-prefix only in the sherpadoc.
+
+// Policy as used in DMARC DNS record for "p=" or "sp=".
+type DMARCPolicy string
+
+// ../rfc/7489:1157
+
+const (
+	PolicyEmpty      DMARCPolicy = "" // Only for the optional Record.SubdomainPolicy.
+	PolicyNone       DMARCPolicy = "none"
+	PolicyQuarantine DMARCPolicy = "quarantine"
+	PolicyReject     DMARCPolicy = "reject"
+)
+
+// URI is a destination address for reporting.
+type URI struct {
+	Address string // Should start with "mailto:".
+	MaxSize uint64 // Optional maximum message size, subject to Unit.
+	Unit    string // "" (b), "k", "g", "t" (case insensitive), unit size, where k is 2^10 etc.
+}
+
+// String returns a string representation of the URI for inclusion in a DMARC
+// record.
+func (u URI) String() string {
+	s := u.Address
+	s = strings.ReplaceAll(s, ",", "%2C")
+	s = strings.ReplaceAll(s, "!", "%21")
+	if u.MaxSize > 0 {
+		s += fmt.Sprintf("%d", u.MaxSize)
+	}
+	s += u.Unit
+	return s
+}
+
+// ../rfc/7489:1127
+
+// Align specifies the required alignment of a domain name.
+type Align string
+
+const (
+	AlignStrict  Align = "s" // Strict requires an exact domain name match.
+	AlignRelaxed Align = "r" // Relaxed requires either an exact or subdomain name match.
+)
+
+// Record is a DNS policy or reporting record.
+//
+// Example:
+//
+//	v=DMARC1; p=reject; rua=mailto:postmaster@mox.example
+type Record struct {
+	Version                    string      // "v=DMARC1"
+	Policy                     DMARCPolicy // Required, for "p=".
+	SubdomainPolicy            DMARCPolicy // Like policy but for subdomains. Optional, for "sp=".
+	AggregateReportAddresses   []URI       // Optional, for "rua=".
+	FailureReportAddresses     []URI       // Optional, for "ruf="
+	ADKIM                      Align       // "r" (default) for relaxed or "s" for simple. For "adkim=".
+	ASPF                       Align       // "r" (default) for relaxed or "s" for simple. For "aspf=".
+	AggregateReportingInterval int         // Default 86400. For "ri="
+	FailureReportingOptions    []string    // "0" (default), "1", "d", "s". For "fo=".
+	ReportingFormat            []string    // "afrf" (default). Ffor "rf=".
+	Percentage                 int         // Between 0 and 100, default 100. For "pct=".
+}
+
+// DefaultRecord holds the defaults for a DMARC record.
+var DefaultRecord = Record{
+	Version:                    "DMARC1",
+	ADKIM:                      "r",
+	ASPF:                       "r",
+	AggregateReportingInterval: 86400,
+	FailureReportingOptions:    []string{"0"},
+	ReportingFormat:            []string{"afrf"},
+	Percentage:                 100,
+}
+
+// String returns the DMARC record for use as DNS TXT record.
+func (r Record) String() string {
+	b := &strings.Builder{}
+	b.WriteString("v=" + r.Version)
+
+	wrote := false
+	write := func(do bool, tag, value string) {
+		if do {
+			fmt.Fprintf(b, ";%s=%s", tag, value)
+			wrote = true
+		}
+	}
+	write(r.Policy != "", "p", string(r.Policy))
+	write(r.SubdomainPolicy != "", "sp", string(r.SubdomainPolicy))
+	if len(r.AggregateReportAddresses) > 0 {
+		l := make([]string, len(r.AggregateReportAddresses))
+		for i, a := range r.AggregateReportAddresses {
+			l[i] = a.String()
+		}
+		s := strings.Join(l, ",")
+		write(true, "rua", s)
+	}
+	if len(r.FailureReportAddresses) > 0 {
+		l := make([]string, len(r.FailureReportAddresses))
+		for i, a := range r.FailureReportAddresses {
+			l[i] = a.String()
+		}
+		s := strings.Join(l, ",")
+		write(true, "ruf", s)
+	}
+	write(r.ADKIM != "", "adkim", string(r.ADKIM))
+	write(r.ASPF != "", "aspf", string(r.ASPF))
+	write(r.AggregateReportingInterval != DefaultRecord.AggregateReportingInterval, "ri", fmt.Sprintf("%d", r.AggregateReportingInterval))
+	if len(r.FailureReportingOptions) > 1 || (len(r.FailureReportingOptions) == 1 && r.FailureReportingOptions[0] != "0") {
+		write(true, "fo", strings.Join(r.FailureReportingOptions, ":"))
+	}
+	if len(r.ReportingFormat) > 1 || (len(r.ReportingFormat) == 1 && strings.EqualFold(r.ReportingFormat[0], "afrf")) {
+		write(true, "rf", strings.Join(r.FailureReportingOptions, ":"))
+	}
+	write(r.Percentage != 100, "pct", fmt.Sprintf("%d", r.Percentage))
+
+	if !wrote {
+		b.WriteString(";")
+	}
+	return b.String()
+}