1package dmarc

2

3import (

4 "fmt"

5 "strings"

6)

7

8// 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.

9

10// Policy as used in DMARC DNS record for "p=" or "sp=".

11type DMARCPolicy string

12

13// ../rfc/7489:1157

14

15const (

16 PolicyEmpty DMARCPolicy = "" // Only for the optional Record.SubdomainPolicy.

17 PolicyNone DMARCPolicy = "none"

18 PolicyQuarantine DMARCPolicy = "quarantine"

19 PolicyReject DMARCPolicy = "reject"

20)

21

22// URI is a destination address for reporting.

23type URI struct {

24 Address string // Should start with "mailto:".

25 MaxSize uint64 // Optional maximum message size, subject to Unit.

26 Unit string // "" (b), "k", "m", "g", "t" (case insensitive), unit size, where k is 2^10 etc.

27}

28

29// String returns a string representation of the URI for inclusion in a DMARC

30// record.

31func (u URI) String() string {

32 s := u.Address

33 s = strings.ReplaceAll(s, ",", "%2C")

34 s = strings.ReplaceAll(s, "!", "%21")

35 if u.MaxSize > 0 {

36 s += fmt.Sprintf("!%d", u.MaxSize)

37 }

38 s += u.Unit

39 return s

40}

41

42// ../rfc/7489:1127

43

44// Align specifies the required alignment of a domain name.

45type Align string

46

47const (

48 AlignStrict Align = "s" // Strict requires an exact domain name match.

49 AlignRelaxed Align = "r" // Relaxed requires either an exact or subdomain name match.

50)

51

52// Record is a DNS policy or reporting record.

53//

54// Example:

55//

56// v=DMARC1; p=reject; rua=mailto:postmaster@mox.example

57type Record struct {

58 Version string // "v=DMARC1", fixed.

59 Policy DMARCPolicy // Required, for "p=".

60 SubdomainPolicy DMARCPolicy // Like policy but for subdomains. Optional, for "sp=".

61 AggregateReportAddresses []URI // Optional, for "rua=". Destination addresses for aggregate reports.

62 FailureReportAddresses []URI // Optional, for "ruf=". Destination addresses for failure reports.

63 ADKIM Align // Alignment: "r" (default) for relaxed or "s" for simple. For "adkim=".

64 ASPF Align // Alignment: "r" (default) for relaxed or "s" for simple. For "aspf=".

65 AggregateReportingInterval int // In seconds, default 86400. For "ri="

66 FailureReportingOptions []string // "0" (default), "1", "d", "s". For "fo=".

67 ReportingFormat []string // "afrf" (default). For "rf=".

68 Percentage int // Between 0 and 100, default 100. For "pct=". Policy applies randomly to this percentage of messages.

69}

70

71// DefaultRecord holds the defaults for a DMARC record.

72var DefaultRecord = Record{

73 Version: "DMARC1",

74 ADKIM: "r",

75 ASPF: "r",

76 AggregateReportingInterval: 86400,

77 FailureReportingOptions: []string{"0"},

78 ReportingFormat: []string{"afrf"},

79 Percentage: 100,

80}

81

82// String returns the DMARC record for use as DNS TXT record.

83func (r Record) String() string {

84 b := &strings.Builder{}

85 b.WriteString("v=" + r.Version)

86

87 wrote := false

88 write := func(do bool, tag, value string) {

89 if do {

90 fmt.Fprintf(b, ";%s=%s", tag, value)

91 wrote = true

92 }

93 }

94 write(r.Policy != "", "p", string(r.Policy))

95 write(r.SubdomainPolicy != "", "sp", string(r.SubdomainPolicy))

96 if len(r.AggregateReportAddresses) > 0 {

97 l := make([]string, len(r.AggregateReportAddresses))

98 for i, a := range r.AggregateReportAddresses {

99 l[i] = a.String()

100 }

101 s := strings.Join(l, ",")

102 write(true, "rua", s)

103 }

104 if len(r.FailureReportAddresses) > 0 {

105 l := make([]string, len(r.FailureReportAddresses))

106 for i, a := range r.FailureReportAddresses {

107 l[i] = a.String()

108 }

109 s := strings.Join(l, ",")

110 write(true, "ruf", s)

111 }

112 write(r.ADKIM != "" && r.ADKIM != "r", "adkim", string(r.ADKIM))

113 write(r.ASPF != "" && r.ASPF != "r", "aspf", string(r.ASPF))

114 write(r.AggregateReportingInterval != DefaultRecord.AggregateReportingInterval, "ri", fmt.Sprintf("%d", r.AggregateReportingInterval))

115 if len(r.FailureReportingOptions) > 1 || len(r.FailureReportingOptions) == 1 && r.FailureReportingOptions[0] != "0" {

116 write(true, "fo", strings.Join(r.FailureReportingOptions, ":"))

117 }

118 if len(r.ReportingFormat) > 1 || len(r.ReportingFormat) == 1 && !strings.EqualFold(r.ReportingFormat[0], "afrf") {

119 write(true, "rf", strings.Join(r.FailureReportingOptions, ":"))

120 }

121 write(r.Percentage != 100, "pct", fmt.Sprintf("%d", r.Percentage))

122

123 if !wrote {

124 b.WriteString(";")

125 }

126 return b.String()

127}

128