dkim: Implement internal dkim signing and verification

This patch implements internal DKIM signing and verification.

internal/dkim/message_test.go

@@ -0,0 +1,99 @@
+package dkim
+
+import (
+	"testing"
+
+	"blitiri.com.ar/go/chasquid/internal/normalize"
+	"github.com/google/go-cmp/cmp"
+	"github.com/google/go-cmp/cmp/cmpopts"
+)
+
+func TestParseMessage(t *testing.T) {
+	cases := []struct {
+		message string
+		headers headers
+		body    string
+	}{
+		{
+			message: normalize.StringToCRLF(`From: a@b
+To: c@d
+Subject: test
+Continues: This
+  continues.
+
+body`),
+			headers: headers{
+				header{Name: "From", Value: " a@b",
+					Source: "From: a@b"},
+				header{Name: "To", Value: " c@d",
+					Source: "To: c@d"},
+				header{Name: "Subject", Value: " test",
+					Source: "Subject: test"},
+				header{Name: "Continues", Value: " This\r\n  continues.",
+					Source: "Continues: This\r\n  continues."},
+			},
+			body: "body",
+		},
+	}
+
+	for i, c := range cases {
+		headers, body, err := parseMessage(c.message)
+		if diff := cmp.Diff(c.headers, headers); diff != "" {
+			t.Errorf("parseMessage([%d]) headers mismatch (-want +got):\n%s",
+				i, diff)
+		}
+		if diff := cmp.Diff(c.body, body); diff != "" {
+			t.Errorf("parseMessage([%d]) body mismatch (-want +got):\n%s",
+				i, diff)
+		}
+		if err != nil {
+			t.Errorf("parseMessage([%d]) error: %v", i, err)
+		}
+
+	}
+}
+
+func TestParseMessageWithErrors(t *testing.T) {
+	cases := []struct {
+		message string
+		err     error
+	}{
+		{
+			// Continuation without previous header.
+			message: " continuation.",
+			err:     errInvalidHeader,
+		},
+		{
+			// Header without ':'.
+			message: "No colon",
+			err:     errInvalidHeader,
+		},
+	}
+
+	for i, c := range cases {
+		_, _, err := parseMessage(c.message)
+		if diff := cmp.Diff(c.err, err, cmpopts.EquateErrors()); diff != "" {
+			t.Errorf("parseMessage([%d]) err mismatch (-want +got):\n%s",
+				i, diff)
+		}
+	}
+}
+
+func TestHeadersFindAll(t *testing.T) {
+	hs := headers{
+		{Name: "From", Value: "a@b", Source: "From: a@b"},
+		{Name: "To", Value: "c@d", Source: "To: c@d"},
+		{Name: "Subject", Value: "test", Source: "Subject: test"},
+		{Name: "fROm", Value: "z@y", Source: "fROm:  z@y"},
+	}
+
+	fromHs := hs.FindAll("froM")
+	expected := headers{
+		{Name: "From", Value: "a@b", Source: "From: a@b"},
+		{Name: "fROm", Value: "z@y", Source: "fROm:  z@y"},
+	}
+	if diff := cmp.Diff(expected, fromHs); diff != "" {
+		t.Errorf("headers.Find() mismatch (-want +got):\n%s", diff)
+	}
+
+}