use gabriel-vasile/mimetype for the mail attachments

CHANGELOG.md

@@ -1,3 +1,8 @@
+## v0.27.0 (WIP)
+
+- Updated the mail attachments auto MIME type detection to use `gabriel-vasile/mimetype` for consistency and broader sniffing signatures support.
+
+
 ## v0.26.1
 
 - Removed the wrapping of `io.EOF` error when reading files since currently `io.ReadAll` doesn't check for wrapped errors ([#6600](https://github.com/pocketbase/pocketbase/issues/6600)).

tools/mailer/mailer.go

@@ -1,9 +1,11 @@
 package mailer
 
 import (
+	"bytes"
 	"io"
 	"net/mail"
 
+	"github.com/gabriel-vasile/mimetype"
 	"github.com/pocketbase/pocketbase/tools/hook"
 )
 
@@ -54,3 +56,17 @@ func addressesToStrings(addresses []mail.Address, withName bool) []string {
 
 	return result
 }
+
+// detectReaderMimeType reads the first couple bytes of the reader to detect its MIME type.
+//
+// Returns a new combined reader from the partial read + the remaining of the original reader.
+func detectReaderMimeType(r io.Reader) (io.Reader, string, error) {
+	readCopy := new(bytes.Buffer)
+
+	mime, err := mimetype.DetectReader(io.TeeReader(r, readCopy))
+	if err != nil {
+		return nil, "", err
+	}
+
+	return io.MultiReader(readCopy, r), mime.String(), nil
+}

tools/mailer/mailer_test.go

@@ -0,0 +1,77 @@
+package mailer
+
+import (
+	"fmt"
+	"io"
+	"net/mail"
+	"strings"
+	"testing"
+)
+
+func TestAddressesToStrings(t *testing.T) {
+	t.Parallel()
+
+	scenarios := []struct {
+		withName  bool
+		addresses []mail.Address
+		expected  []string
+	}{
+		{
+			true,
+			[]mail.Address{{Name: "John Doe", Address: "test1@example.com"}, {Name: "Jane Doe", Address: "test2@example.com"}},
+			[]string{`"John Doe" <test1@example.com>`, `"Jane Doe" <test2@example.com>`},
+		},
+		{
+			true,
+			[]mail.Address{{Name: "John Doe", Address: "test1@example.com"}, {Address: "test2@example.com"}},
+			[]string{`"John Doe" <test1@example.com>`, `test2@example.com`},
+		},
+		{
+			false,
+			[]mail.Address{{Name: "John Doe", Address: "test1@example.com"}, {Name: "Jane Doe", Address: "test2@example.com"}},
+			[]string{`test1@example.com`, `test2@example.com`},
+		},
+	}
+
+	for _, s := range scenarios {
+		t.Run(fmt.Sprintf("%v_%v", s.withName, s.addresses), func(t *testing.T) {
+			result := addressesToStrings(s.addresses, s.withName)
+
+			if len(s.expected) != len(result) {
+				t.Fatalf("Expected\n%v\ngot\n%v", s.expected, result)
+			}
+
+			for k, v := range s.expected {
+				if v != result[k] {
+					t.Fatalf("Expected %d address %q, got %q", k, v, result[k])
+				}
+			}
+		})
+	}
+}
+
+func TestDetectReaderMimeType(t *testing.T) {
+	t.Parallel()
+
+	str := "#!/bin/node\n" + strings.Repeat("a", 10000) // ensure that it is large enough to remain after the signature sniffing
+
+	r, mime, err := detectReaderMimeType(strings.NewReader(str))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	expectedMime := "text/javascript"
+	if mime != expectedMime {
+		t.Fatalf("Expected mime %q, got %q", expectedMime, mime)
+	}
+
+	raw, err := io.ReadAll(r)
+	if err != nil {
+		t.Fatal(err)
+	}
+	rawStr := string(raw)
+
+	if rawStr != str {
+		t.Fatalf("Expected content\n%s\ngot\n%s", str, rawStr)
+	}
+}

tools/mailer/smtp.go

@@ -116,12 +116,20 @@ func (c *SMTPClient) send(m *Message) error {
 
 	// add regular attachements (if any)
 	for name, data := range m.Attachments {
-		yak.Attach(name, data)
+		r, mime, err := detectReaderMimeType(data)
+		if err != nil {
+			return err
+		}
+		yak.AttachWithMimeType(name, r, mime)
 	}
 
 	// add inline attachments (if any)
 	for name, data := range m.InlineAttachments {
-		yak.AttachInline(name, data)
+		r, mime, err := detectReaderMimeType(data)
+		if err != nil {
+			return err
+		}
+		yak.AttachInlineWithMimeType(name, r, mime)
 	}
 
 	// add custom headers (if any)