mirror of
https://blitiri.com.ar/repos/chasquid
synced 2026-10-29 15:02:30 +00:00
Alberto Bertogli
5c4193a8b6
Today, we treat l=0 to mean the whole body is signed. However, RFC 6376 is clear that means _none_ of the body is signed. This patch fixes that behaviour to match the RFC. Cross-checking other implementations for potential compatibility issues, OpenDKIM and Exim both treat l=0 the same way this patch does. In practice, l=0 is extremely rare, and that's why this incorrect behaviour persisted unnoticed for so long. Note this incorrect behaviour would cause valid signatures to fail to verify, but never allow invalid signatures to pass.
475 lines
14 KiB
Go
475 lines
14 KiB
Go
package dkim
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import (
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"context"
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"crypto"
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"encoding/base64"
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"errors"
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"net"
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"strings"
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"testing"
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"github.com/google/go-cmp/cmp"
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)
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func toCRLF(s string) string {
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return strings.ReplaceAll(s, "\n", "\r\n")
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}
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func makeLookupTXT(results map[string][]string) lookupTXTFunc {
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return func(ctx context.Context, domain string) ([]string, error) {
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return results[domain], nil
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}
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}
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func TestVerifyRF6376CExample(t *testing.T) {
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ctx := t.Context()
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ctx = WithTraceFunc(ctx, t.Logf)
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// Use the public key from the example in RFC 6376 appendix C.
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// https://datatracker.ietf.org/doc/html/rfc6376#appendix-C
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ctx = WithLookupTXTFunc(ctx, makeLookupTXT(map[string][]string{
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"brisbane._domainkey.example.com": {
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"v=DKIM1; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQ" +
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"KBgQDwIRP/UC3SBsEmGqZ9ZJW3/DkMoGeLnQg1fWn7/zYt" +
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"IxN2SnFCjxOCKG9v3b4jYfcTNh5ijSsq631uBItLa7od+v" +
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"/RtdC2UzJ1lWT947qR+Rcac2gbto/NMqJ0fzfVjH4OuKhi" +
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"tdY9tf6mcwGjaNBcWToIMmPSPDdQPNUYckcQ2QIDAQAB",
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},
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}))
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// Note that the examples in the RFC text have multiple issues:
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// - The double space in "game. Are" should be a single
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// space. Otherwise, the body hash does not match.
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// https://www.rfc-editor.org/errata/eid3192
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// - The header indentation is incorrect. This causes
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// signature validation failure (because the example uses simple
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// canonicalization, which leaves the indentation untouched).
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// https://www.rfc-editor.org/errata/eid4926
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message := toCRLF(
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`DKIM-Signature: v=1; a=rsa-sha256; s=brisbane; d=example.com;
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c=simple/simple; q=dns/txt; i=joe@football.example.com;
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h=Received : From : To : Subject : Date : Message-ID;
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bh=2jUSOH9NhtVGCQWNr9BrIAPreKQjO6Sn7XIkfJVOzv8=;
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b=AuUoFEfDxTDkHlLXSZEpZj79LICEps6eda7W3deTVFOk4yAUoqOB
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4nujc7YopdG5dWLSdNg6xNAZpOPr+kHxt1IrE+NahM6L/LbvaHut
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KVdkLLkpVaVVQPzeRDI009SO2Il5Lu7rDNH6mZckBdrIx0orEtZV
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4bmp/YzhwvcubU4=;
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Received: from client1.football.example.com [192.0.2.1]
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by submitserver.example.com with SUBMISSION;
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Fri, 11 Jul 2003 21:01:54 -0700 (PDT)
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From: Joe SixPack <joe@football.example.com>
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To: Suzie Q <suzie@shopping.example.net>
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Subject: Is dinner ready?
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Date: Fri, 11 Jul 2003 21:00:37 -0700 (PDT)
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Message-ID: <20030712040037.46341.5F8J@football.example.com>
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Hi.
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We lost the game. Are you hungry yet?
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Joe.
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`)
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res, err := VerifyMessage(ctx, message)
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if res.Valid != 1 || err != nil {
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t.Errorf("VerifyMessage: wanted 1 valid / nil; got %v / %v", res, err)
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}
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// Extend the message, check it does not pass validation.
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res, err = VerifyMessage(ctx, message+"Extra line.\r\n")
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if res.Valid != 0 || err != nil {
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t.Errorf("VerifyMessage: wanted 0 valid / nil; got %v / %v", res, err)
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}
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// Alter a header, check it does not pass validation.
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res, err = VerifyMessage(ctx,
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strings.Replace(message, "Subject", "X-Subject", 1))
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if res.Valid != 0 || err != nil {
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t.Errorf("VerifyMessage: wanted 0 valid / nil; got %v / %v", res, err)
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}
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}
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func TestVerifyRFC8463Example(t *testing.T) {
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ctx := t.Context()
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ctx = WithTraceFunc(ctx, t.Logf)
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// Use the public keys from the example in RFC 8463 appendix A.2.
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// https://datatracker.ietf.org/doc/html/rfc6376#appendix-C
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ctx = WithLookupTXTFunc(ctx, makeLookupTXT(map[string][]string{
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"brisbane._domainkey.football.example.com": {
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"v=DKIM1; k=ed25519; " +
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"p=11qYAYKxCrfVS/7TyWQHOg7hcvPapiMlrwIaaPcHURo="},
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"test._domainkey.football.example.com": {
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"v=DKIM1; k=rsa; " +
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"p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDkHlOQoBTzWR" +
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"iGs5V6NpP3idY6Wk08a5qhdR6wy5bdOKb2jLQiY/J16JYi0Qvx/b" +
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"yYzCNb3W91y3FutACDfzwQ/BC/e/8uBsCR+yz1Lxj+PL6lHvqMKr" +
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"M3rG4hstT5QjvHO9PzoxZyVYLzBfO2EeC3Ip3G+2kryOTIKT+l/K" +
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"4w3QIDAQAB"},
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}))
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message := toCRLF(
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`DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed;
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d=football.example.com; i=@football.example.com;
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q=dns/txt; s=brisbane; t=1528637909; h=from : to :
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subject : date : message-id : from : subject : date;
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bh=2jUSOH9NhtVGCQWNr9BrIAPreKQjO6Sn7XIkfJVOzv8=;
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b=/gCrinpcQOoIfuHNQIbq4pgh9kyIK3AQUdt9OdqQehSwhEIug4D11Bus
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Fa3bT3FY5OsU7ZbnKELq+eXdp1Q1Dw==
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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
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d=football.example.com; i=@football.example.com;
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q=dns/txt; s=test; t=1528637909; h=from : to : subject :
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date : message-id : from : subject : date;
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bh=2jUSOH9NhtVGCQWNr9BrIAPreKQjO6Sn7XIkfJVOzv8=;
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b=F45dVWDfMbQDGHJFlXUNB2HKfbCeLRyhDXgFpEL8GwpsRe0IeIixNTe3
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DhCVlUrSjV4BwcVcOF6+FF3Zo9Rpo1tFOeS9mPYQTnGdaSGsgeefOsk2Jz
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dA+L10TeYt9BgDfQNZtKdN1WO//KgIqXP7OdEFE4LjFYNcUxZQ4FADY+8=
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From: Joe SixPack <joe@football.example.com>
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To: Suzie Q <suzie@shopping.example.net>
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Subject: Is dinner ready?
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Date: Fri, 11 Jul 2003 21:00:37 -0700 (PDT)
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Message-ID: <20030712040037.46341.5F8J@football.example.com>
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Hi.
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We lost the game. Are you hungry yet?
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Joe.
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`)
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expected := &VerifyResult{
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Found: 2,
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Valid: 2,
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Results: []*OneResult{
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{
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SignatureHeader: toCRLF(
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` v=1; a=ed25519-sha256; c=relaxed/relaxed;
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d=football.example.com; i=@football.example.com;
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q=dns/txt; s=brisbane; t=1528637909; h=from : to :
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subject : date : message-id : from : subject : date;
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bh=2jUSOH9NhtVGCQWNr9BrIAPreKQjO6Sn7XIkfJVOzv8=;
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b=/gCrinpcQOoIfuHNQIbq4pgh9kyIK3AQUdt9OdqQehSwhEIug4D11Bus
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Fa3bT3FY5OsU7ZbnKELq+eXdp1Q1Dw==`),
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Domain: "football.example.com",
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Selector: "brisbane",
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B: "/gCrinpcQOoIfuHNQIbq4pgh9kyIK3AQUdt9OdqQehSwhEIug4D11" +
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"BusFa3bT3FY5OsU7ZbnKELq+eXdp1Q1Dw==",
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State: SUCCESS,
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Error: nil,
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},
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{
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SignatureHeader: toCRLF(
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` v=1; a=rsa-sha256; c=relaxed/relaxed;
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d=football.example.com; i=@football.example.com;
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q=dns/txt; s=test; t=1528637909; h=from : to : subject :
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date : message-id : from : subject : date;
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bh=2jUSOH9NhtVGCQWNr9BrIAPreKQjO6Sn7XIkfJVOzv8=;
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b=F45dVWDfMbQDGHJFlXUNB2HKfbCeLRyhDXgFpEL8GwpsRe0IeIixNTe3
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DhCVlUrSjV4BwcVcOF6+FF3Zo9Rpo1tFOeS9mPYQTnGdaSGsgeefOsk2Jz
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dA+L10TeYt9BgDfQNZtKdN1WO//KgIqXP7OdEFE4LjFYNcUxZQ4FADY+8=`),
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Domain: "football.example.com",
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Selector: "test",
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B: "F45dVWDfMbQDGHJFlXUNB2HKfbCeLRyhDXgFpEL8GwpsRe0IeIixNTe" +
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"3DhCVlUrSjV4BwcVcOF6+FF3Zo9Rpo1tFOeS9mPYQTnGdaSGsgeefO" +
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"sk2JzdA+L10TeYt9BgDfQNZtKdN1WO//KgIqXP7OdEFE4LjFYNcUxZ" +
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"Q4FADY+8=",
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State: SUCCESS,
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Error: nil,
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},
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},
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}
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res, err := VerifyMessage(ctx, message)
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if err != nil {
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t.Fatalf("VerifyMessage returned error: %v", err)
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}
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if diff := cmp.Diff(expected, res); diff != "" {
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t.Errorf("VerifyMessage diff (-want +got):\n%s", diff)
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}
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// Extend the message, check it does not pass validation.
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res, err = VerifyMessage(ctx, message+"Extra line.\r\n")
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if res.Found != 2 || res.Valid != 0 || err != nil {
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t.Errorf("VerifyMessage: wanted 2 found, 0 valid / nil; got %v / %v",
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res, err)
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}
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// Alter a header, check it does not pass validation.
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res, err = VerifyMessage(ctx,
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strings.Replace(message, "Subject", "X-Subject", 1))
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if res.Found != 2 || res.Valid != 0 || err != nil {
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t.Errorf("VerifyMessage: wanted 2 found, 0 valid / nil; got %v / %v",
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res, err)
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}
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}
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func TestVerifyBodyLength(t *testing.T) {
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ctx := t.Context()
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ctx = WithTraceFunc(ctx, t.Logf)
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// Any valid key works, since none of the signatures here are valid. We
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// use the one from the example in RFC 8463 appendix A.2.
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ctx = WithLookupTXTFunc(ctx, makeLookupTXT(map[string][]string{
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"brisbane._domainkey.example.com": {
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"v=DKIM1; k=ed25519; " +
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"p=11qYAYKxCrfVS/7TyWQHOg7hcvPapiMlrwIaaPcHURo="},
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}))
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// Use a valid body hash (of the "signed" part of the body), so we can
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// tell the l= cases apart: when l= covers exactly the signed part, the
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// body hash matches and we fail later on (because b= is bogus).
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body := "Hi.\r\n"
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cases := []struct {
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l string
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signed string
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want error
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}{
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{"0", "", ErrVerificationFailed},
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{"0", body, ErrBodyHashMismatch},
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{"4", body, ErrBodyHashMismatch},
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{"5", body, ErrVerificationFailed},
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{"6", body, errInvalidTag},
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{"18446744073709551615", body, errInvalidTag},
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}
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for _, c := range cases {
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bh := base64.StdEncoding.EncodeToString(
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hashWith(crypto.SHA256, []byte(c.signed)))
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message := toCRLF(
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"DKIM-Signature: v=1; a=ed25519-sha256; c=simple/simple;\n"+
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" d=example.com; s=brisbane; h=from; l="+c.l+";\n"+
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" bh="+bh+"; b=AAAA\n"+
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"From: Joe SixPack <joe@example.com>\n"+
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"\n") + body
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res, err := VerifyMessage(ctx, message)
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if err != nil {
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t.Fatalf("l=%s signed=%q: VerifyMessage returned error: %v",
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c.l, c.signed, err)
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}
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if res.Found != 1 || res.Valid != 0 {
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t.Fatalf("l=%s signed=%q: wanted 1 found, 0 valid; got %v",
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c.l, c.signed, res)
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}
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r := res.Results[0]
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if r.State != PERMFAIL || !errors.Is(r.Error, c.want) {
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t.Errorf("l=%s signed=%q: wanted PERMFAIL / %v; got %v / %v",
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c.l, c.signed, c.want, r.State, r.Error)
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}
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}
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}
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func TestHeadersToInclude(t *testing.T) {
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// Test that headersToInclude returns the expected headers.
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cases := []struct {
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sigH header
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hTag []string
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headers headers
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want []header
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}{
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// Check that if a header appears more than once, we pick the latest
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// first.
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{
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sigH: header{
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Name: "DKIM-Signature",
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Value: "v=1; a=rsa-sha256; s=brisbane; d=example.com;",
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},
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hTag: []string{"From", "To", "Subject"},
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headers: headers{
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{Name: "From", Value: "from1"},
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{Name: "To", Value: "to1"},
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{Name: "Subject", Value: "subject1"},
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{Name: "From", Value: "from2"},
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},
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want: []header{
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{Name: "From", Value: "from2"},
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{Name: "To", Value: "to1"},
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{Name: "Subject", Value: "subject1"},
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},
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},
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// Check that if a header is requested twice but only appears once, we
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// only return it once.
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// This is a common technique suggested by the RFC to make signatures
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// fail if a header is added.
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{
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sigH: header{
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Name: "DKIM-Signature",
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Value: "v=1; a=rsa-sha256; s=brisbane; d=example.com;",
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},
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hTag: []string{"From", "From", "To", "Subject"},
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headers: headers{
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{Name: "From", Value: "from1"},
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{Name: "To", Value: "to1"},
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{Name: "Subject", Value: "subject1"},
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},
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want: []header{
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{Name: "From", Value: "from1"},
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{Name: "To", Value: "to1"},
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{Name: "Subject", Value: "subject1"},
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},
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},
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// Check that if DKIM-Signature is included, we do *not* include the
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// one we're currently verifying in the headers to include.
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// https://datatracker.ietf.org/doc/html/rfc6376#section-3.7
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{
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sigH: header{
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Name: "DKIM-Signature",
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Value: "v=1; a=rsa-sha256; s=brisbane; d=example.com;",
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},
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hTag: []string{"From", "From", "DKIM-Signature", "DKIM-Signature"},
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headers: headers{
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{Name: "From", Value: "from1"},
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{Name: "To", Value: "to1"},
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{
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Name: "DKIM-Signature",
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Value: "v=1; a=rsa-sha256; s=sidney; d=example.com;",
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},
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{
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Name: "DKIM-Signature",
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Value: "v=1; a=rsa-sha256; s=brisbane; d=example.com;",
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},
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},
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want: []header{
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{Name: "From", Value: "from1"},
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{
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Name: "DKIM-Signature",
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Value: "v=1; a=rsa-sha256; s=sidney; d=example.com;",
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},
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},
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},
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}
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for _, c := range cases {
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got := headersToInclude(c.sigH, c.hTag, c.headers)
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if diff := cmp.Diff(c.want, got); diff != "" {
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t.Errorf("headersToInclude(%q, %v, %v) diff (-want +got):\n%s",
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c.sigH, c.hTag, c.headers, diff)
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}
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}
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}
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func TestAuthenticationResults(t *testing.T) {
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resBrisbane := &OneResult{
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Domain: "football.example.com",
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Selector: "brisbane",
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B: "/gCrinpcQOoIfuHNQIbq4pgh9kyIK3AQUdt9OdqQehSwhEIug4D11" +
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"BusFa3bT3FY5OsU7ZbnKELq+eXdp1Q1Dw==",
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State: SUCCESS,
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Error: nil,
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}
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resTest := &OneResult{
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Domain: "football.example.com",
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Selector: "test",
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B: "F45dVWDfMbQDGHJFlXUNB2HKfbCeLRyhDXgFpEL8GwpsRe0IeIixNTe" +
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"3DhCVlUrSjV4BwcVcOF6+FF3Zo9Rpo1tFOeS9mPYQTnGdaSGsgeefO" +
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"sk2JzdA+L10TeYt9BgDfQNZtKdN1WO//KgIqXP7OdEFE4LjFYNcUxZ" +
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"Q4FADY+8=",
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State: SUCCESS,
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Error: nil,
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}
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resFail := &OneResult{
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Domain: "football.example.com",
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Selector: "paris",
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B: "slfkdMSDFeslif39seFfjl93sljisdsdlif923l",
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State: PERMFAIL,
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Error: ErrVerificationFailed,
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}
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resPermFail := &OneResult{
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Domain: "football.example.com",
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Selector: "paris",
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// No B tag on purpose.
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State: PERMFAIL,
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Error: errMissingRequiredTag,
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}
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resTempFail := &OneResult{
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Domain: "football.example.com",
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Selector: "paris",
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B: "shorty", // Less than 12 characters to check we include it well.
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State: TEMPFAIL,
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Error: &net.DNSError{
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Err: "dns temp error (for testing)",
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IsTemporary: true,
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},
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}
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cases := []struct {
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results *VerifyResult
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want string
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}{
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{
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results: &VerifyResult{},
|
|
want: ";dkim=none\r\n",
|
|
},
|
|
{
|
|
results: &VerifyResult{
|
|
Found: 1,
|
|
Valid: 1,
|
|
Results: []*OneResult{resBrisbane},
|
|
},
|
|
want: ";dkim=pass" +
|
|
" header.b=/gCrinpcQOoI header.d=football.example.com\r\n",
|
|
},
|
|
{
|
|
results: &VerifyResult{
|
|
Found: 2,
|
|
Valid: 2,
|
|
Results: []*OneResult{resBrisbane, resTest},
|
|
},
|
|
want: ";dkim=pass" +
|
|
" header.b=/gCrinpcQOoI header.d=football.example.com\r\n" +
|
|
";dkim=pass" +
|
|
" header.b=F45dVWDfMbQD header.d=football.example.com\r\n",
|
|
},
|
|
{
|
|
results: &VerifyResult{
|
|
Found: 2,
|
|
Valid: 2,
|
|
Results: []*OneResult{resBrisbane, resTest},
|
|
},
|
|
want: ";dkim=pass" +
|
|
" header.b=/gCrinpcQOoI header.d=football.example.com\r\n" +
|
|
";dkim=pass" +
|
|
" header.b=F45dVWDfMbQD header.d=football.example.com\r\n",
|
|
},
|
|
{
|
|
results: &VerifyResult{
|
|
Found: 2,
|
|
Valid: 1,
|
|
Results: []*OneResult{resFail, resTest},
|
|
},
|
|
want: ";dkim=fail reason=\"verification failed\"\r\n" +
|
|
" header.b=slfkdMSDFesl header.d=football.example.com\r\n" +
|
|
";dkim=pass" +
|
|
" header.b=F45dVWDfMbQD header.d=football.example.com\r\n",
|
|
},
|
|
{
|
|
results: &VerifyResult{
|
|
Found: 1,
|
|
Results: []*OneResult{resPermFail},
|
|
},
|
|
want: ";dkim=permerror reason=\"missing required tag\"\r\n" +
|
|
" header.d=football.example.com\r\n",
|
|
},
|
|
{
|
|
results: &VerifyResult{
|
|
Found: 1,
|
|
Results: []*OneResult{resTempFail},
|
|
},
|
|
want: ";dkim=temperror reason=\"lookup : dns temp error (for testing)\"\r\n" +
|
|
" header.b=shorty header.d=football.example.com\r\n",
|
|
},
|
|
}
|
|
|
|
for i, c := range cases {
|
|
got := c.results.AuthenticationResults()
|
|
if diff := cmp.Diff(c.want, got); diff != "" {
|
|
t.Errorf("case %d: AuthenticationResults() diff (-want +got):\n%s",
|
|
i, diff)
|
|
}
|
|
}
|
|
}
|