fix(channels): cap email body part size to avoid unbounded io.ReadAll

- Add defaultBodyPartMaxBytes (1MB) and config body_part_max_bytes; 0 = use default
- Use io.LimitReader when reading text/plain and text/html parts; show placeholder when part exceeds limit
- Add BodyPartMaxBytes to EmailConfig (config.go)
- Add test "body part max bytes" for extractEmailBodyAndAttachments with limit

pkg/channels/email.go

@@ -38,6 +38,8 @@ const (
 	reconnectBackoffMax = 10 * time.Minute
 	// default attachment max bytes
 	defaultAttachmentMaxBytes = 25 * 1024 * 1024 // 25MB
+	// max bytes to read per body part (text/plain, text/html) to avoid unbounded io.ReadAll
+	defaultBodyPartMaxBytes = 1 * 1024 * 1024 // 1MB
 )
 
 type EmailChannel struct {
@@ -764,10 +766,19 @@ func (c *EmailChannel) extractEmailBodyAndAttachments(msg *imap.Message) (conten
 			continue
 		}
 
-		body, err := io.ReadAll(p.Body)
+		limit := int64(c.config.BodyPartMaxBytes)
+		if limit <= 0 {
+			limit = int64(defaultBodyPartMaxBytes)
+		}
+		limitedBody := io.LimitReader(p.Body, limit+1)
+		body, err := io.ReadAll(limitedBody)
 		if err != nil || len(body) == 0 {
 			continue
 		}
+		if len(body) > int(limit) {
+			textParts = append(textParts, fmt.Sprintf("[body part exceeds size limit (max %d bytes), you can check body_part_max_bytes in config]", limit))
+			continue
+		}
 		bodyStr := strings.TrimSpace(string(body))
 		if bodyStr == "" {
 			continue

pkg/channels/email_test.go

@@ -112,8 +112,7 @@ func TestEmailChannel_extractEmailBodyAndAttachments(t *testing.T) {
 		assert.Empty(t, paths)
 	})
 
-	t.Run("attachment and text body", func(t *testing.T) {
-		mimeBytes := []byte(
+	attachmentwithText := []byte(
 		"From: a@b.com\r\n" +
 			"To: c@d.com\r\n" +
 			"Subject: test-file-and-body\r\n" +
@@ -142,6 +141,8 @@ func TestEmailChannel_extractEmailBodyAndAttachments(t *testing.T) {
 			"\r\n" +
 			"VGVzdC0xMTEx\r\n" +
 			"--outer--\r\n")
+	t.Run("attachment and text body", func(t *testing.T) {
+		mimeBytes := attachmentwithText
 		section := &imap.BodySectionName{}
 		msg := &imap.Message{
 			Uid:      1,
@@ -155,6 +156,28 @@ func TestEmailChannel_extractEmailBodyAndAttachments(t *testing.T) {
 		assert.Contains(t, paths[0], filepath.Base(paths[0]))
 	})
 
+	newLimitClient := &EmailChannel{
+		config: config.EmailConfig{
+			BodyPartMaxBytes:   1,
+			AttachmentDir:      t.TempDir(),
+			AttachmentMaxBytes: 1024,
+		},
+	}
+	t.Run("body part max bytes", func(t *testing.T) {
+
+		mimeBytes := attachmentwithText
+		section := &imap.BodySectionName{}
+		msg := &imap.Message{
+			Uid:      1,
+			Envelope: &imap.Envelope{Subject: "Test"},
+			Body:     map[*imap.BodySectionName]imap.Literal{section: bytes.NewReader(mimeBytes)},
+		}
+		content, paths := newLimitClient.extractEmailBodyAndAttachments(msg)
+		assert.Contains(t, content, "[body part exceeds size limit (max 1 bytes), you can check body_part_max_bytes in config]")
+		assert.NotEmpty(t, paths)
+		assert.Equal(t, 1, len(paths))
+		assert.Contains(t, paths[0], filepath.Base(paths[0]))
+	})
 }
 
 func TestEmailChannel_extractTextFromHTML(t *testing.T) {

pkg/config/config.go

@@ -163,6 +163,7 @@ type EmailConfig struct {
 	AttachmentDir string              `json:"attachment_dir" env:"PICOCLAW_CHANNELS_EMAIL_ATTACHMENT_DIR"`
 	// max size per attachment (default 25*1024*1024(25MB)), 0 = use default
 	AttachmentMaxBytes int `json:"attachment_max_bytes" env:"PICOCLAW_CHANNELS_EMAIL_ATTACHMENT_MAX_BYTES"` // max size per attachment (default 25MB), 0 = use default
+	BodyPartMaxBytes   int `json:"body_part_max_bytes" env:"PICOCLAW_CHANNELS_EMAIL_BODY_PART_MAX_BYTES"`   // max size per body part (text/plain, text/html) to avoid unbounded io.ReadAll (default 1MB), 0 = use default
 	// SMTP send (optional, if not configured, Send is not available)
 	SMTPServer string `json:"smtp_server" env:"PICOCLAW_CHANNELS_EMAIL_SMTP_SERVER"`
 	SMTPPort   int    `json:"smtp_port" env:"PICOCLAW_CHANNELS_EMAIL_SMTP_PORT"`       // 465 或 587