feat(modify): new modifier add_header

.mkdocs.yml

@@ -53,6 +53,7 @@ nav:
       - SMTP modifiers:
           - reference/modifiers/dkim.md
           - reference/modifiers/envelope.md
+          - reference/modifiers/header.md
       - Lookup tables (string translation):
           - reference/table/static.md
           - reference/table/regexp.md

docs/reference/modifiers/header.md

@@ -0,0 +1,23 @@
+# Header Modifiers
+
+## Adding a new header
+
+`add_header` module modifies the message by adding an header.
+
+Note: the header must be present in the message prior to the execution of the modifier. 
+If the header already exist it will result in an error.
+
+
+Definition:
+
+```
+add_header <headerName> <headerValue>
+```
+
+Use examples:
+
+```
+modify {
+	add_header X-My-Header "header value"
+}
+```

internal/modify/add_header.go

@@ -0,0 +1,94 @@
+/*
+Maddy Mail Server - Composable all-in-one email server.
+Copyright © 2019-2020 Max Mazurov <[email protected]>, Maddy Mail Server contributors
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+package modify
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"github.com/emersion/go-message/textproto"
+	"github.com/foxcpp/maddy/framework/buffer"
+	"github.com/foxcpp/maddy/framework/config"
+	"github.com/foxcpp/maddy/framework/module"
+)
+
+// addHeader is a simple module that adds a header to the message
+type addHeader struct {
+	modName  string
+	instName string
+
+	headerName  string
+	headerValue string
+}
+
+func NewAddHeader(modName, instName string) (module.Module, error) {
+	r := addHeader{
+		modName:  modName,
+		instName: instName,
+	}
+
+	return &r, nil
+}
+
+func (m *addHeader) Configure(inlineArgs []string, cfg *config.Map) error {
+	if len(inlineArgs) != 2 {
+		return errors.New("modify.add_header: at least two arguments required")
+	}
+	m.headerName = inlineArgs[0]
+	m.headerValue = inlineArgs[1]
+	return nil
+}
+
+func (r addHeader) Name() string {
+	return r.modName
+}
+
+func (r addHeader) InstanceName() string {
+	return r.instName
+}
+
+func (r addHeader) ModStateForMsg(ctx context.Context, msgMeta *module.MsgMetadata) (module.ModifierState, error) {
+	return r, nil
+}
+
+func (r addHeader) RewriteSender(ctx context.Context, mailFrom string) (string, error) {
+	return mailFrom, nil
+}
+
+func (r addHeader) RewriteRcpt(ctx context.Context, rcptTo string) ([]string, error) {
+	return []string{rcptTo}, nil
+}
+
+func (r addHeader) RewriteBody(ctx context.Context, h *textproto.Header, body buffer.Buffer) error {
+	if h.Has(r.headerName) {
+		return fmt.Errorf("cannot add header `%s` as it is already present", r.headerName)
+	}
+
+	h.Set(r.headerName, r.headerValue)
+	return nil
+}
+
+func (r addHeader) Close() error {
+	return nil
+}
+
+func init() {
+	module.Register("modify.add_header", NewAddHeader)
+}

internal/modify/add_header_test.go

@@ -0,0 +1,90 @@
+/*
+Maddy Mail Server - Composable all-in-one email server.
+Copyright © 2019-2020 Max Mazurov <[email protected]>, Maddy Mail Server contributors
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+package modify
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"strings"
+	"testing"
+
+	"github.com/emersion/go-message/textproto"
+	"github.com/foxcpp/maddy/framework/buffer"
+	"github.com/foxcpp/maddy/framework/config"
+	"github.com/foxcpp/maddy/framework/module"
+)
+
+func TestAddHeader(t *testing.T) {
+	test := func(headerName string, headerValue string, duplicateHeader bool) {
+		t.Helper()
+
+		mod, err := NewAddHeader("modify.add_header", "")
+		if err != nil {
+			t.Fatal(err)
+		}
+		m := mod.(*addHeader)
+		if err := m.Configure([]string{headerName, headerValue}, config.NewMap(nil, config.Node{})); err != nil {
+			t.Fatal(err)
+		}
+
+		state, err := m.ModStateForMsg(context.Background(), &module.MsgMetadata{})
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		testHdr := textproto.Header{}
+		testHdr.Add("From", "<hello@hello>")
+		testHdr.Add("Subject", "heya")
+		testHdr.Add("To", "<heya@heya>")
+		body := []byte("hello there\r\n")
+
+		// modify.dkim expects RewriteSender to be called to get envelope sender
+		//  (see module.Modifier docs)
+
+		err = state.RewriteBody(context.Background(), &testHdr, buffer.MemoryBuffer{Slice: body})
+		if err != nil {
+			if duplicateHeader && strings.Contains(err.Error(), "already present") {
+				return
+			}
+			t.Fatal(err)
+		}
+		if duplicateHeader && err == nil {
+			t.Fatalf("expected error on duplicate header")
+		}
+
+		var fullBody bytes.Buffer
+		if err := textproto.WriteHeader(&fullBody, testHdr); err != nil {
+			t.Fatal(err)
+		}
+		if _, err := fullBody.Write(body); err != nil {
+			t.Fatal(err)
+		}
+
+		if !strings.Contains(fmt.Sprintf("%s", &fullBody), fmt.Sprintf("%s: %s", headerName, headerValue)) {
+			t.Fatalf("new header not found in message")
+		}
+	}
+
+	test("Something", "Somevalue", false)
+	test("X-Testing", "Somevalue", false)
+	// Test setting a header that is already present
+	test("To", "Somevalue", true)
+	test("To", "Somevalue", true)
+}