feat(mail): support IMAP SOCKS5 proxy dialing

Use IMAP_PROXY_URL to route IMAP TLS connections through SOCKS5 when configured, while preserving direct dialing when unset.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

internal/mail/imap.go

@@ -2,9 +2,12 @@ package mail
 
 import (
 	"context"
+	"crypto/tls"
 	"fmt"
 	"io"
 	"log/slog"
+	"net"
+	"net/url"
 	"strings"
 	"time"
 
@@ -13,6 +16,7 @@ import (
 	"github.com/emersion/go-imap/v2"
 	"github.com/emersion/go-imap/v2/imapclient"
 	"github.com/google/uuid"
+	"golang.org/x/net/proxy"
 	"thuanle.me/claw-email-bridge/internal/config"
 	"thuanle.me/claw-email-bridge/internal/database"
 	"thuanle.me/claw-email-bridge/internal/logging"
@@ -25,6 +29,9 @@ type IMAPWatcher struct {
 	db     *gorm.DB
 	client *imapclient.Client
 
+	dialIMAP         func(addr string, options *imapclient.Options) (*imapclient.Client, error)
+	dialIMAPViaProxy func(addr, proxyURL string, options *imapclient.Options) (*imapclient.Client, error)
+
 	// onReceived is called after a task is saved as RECEIVED.
 	// This will be wired to the OpenClaw dispatch in a future step.
 	OnReceived func(task *database.Task)
@@ -32,7 +39,12 @@ type IMAPWatcher struct {
 
 // NewIMAPWatcher creates a new IMAP watcher.
 func NewIMAPWatcher(cfg *config.Config, db *gorm.DB) *IMAPWatcher {
-	return &IMAPWatcher{cfg: cfg, db: db}
+	return &IMAPWatcher{
+		cfg:              cfg,
+		db:               db,
+		dialIMAP:         imapclient.DialTLS,
+		dialIMAPViaProxy: dialTLSViaSOCKS5,
+	}
 }
 
 // Run connects to IMAP, selects INBOX, and enters the IDLE loop.
@@ -71,9 +83,15 @@ func (w *IMAPWatcher) connectAndWatch(ctx context.Context) error {
 	addr := fmt.Sprintf("%s:%s", w.cfg.IMAPHost, w.cfg.IMAPPort)
 	slog.Info("imap: connecting", "addr", addr)
 
-	c, err := imapclient.DialTLS(addr, options)
+	var c *imapclient.Client
+	var err error
+	if strings.TrimSpace(w.cfg.IMAPProxyURL) == "" {
+		c, err = w.dialIMAP(addr, options)
+	} else {
+		c, err = w.dialIMAPViaProxy(addr, w.cfg.IMAPProxyURL, options)
+	}
 	if err != nil {
-		return fmt.Errorf("dial TLS: %w", err)
+		return fmt.Errorf("dial IMAP: %w", err)
 	}
 	w.client = c
 	defer func() {
@@ -144,6 +162,44 @@ func (w *IMAPWatcher) connectAndWatch(ctx context.Context) error {
 	}
 }
 
+func dialTLSViaSOCKS5(addr, proxyURL string, options *imapclient.Options) (*imapclient.Client, error) {
+	u, err := url.Parse(proxyURL)
+	if err != nil {
+		return nil, fmt.Errorf("parse proxy url: %w", err)
+	}
+	if u.Scheme != "socks5" {
+		return nil, fmt.Errorf("unsupported proxy scheme: %s", u.Scheme)
+	}
+
+	var auth *proxy.Auth
+	if u.User != nil {
+		pw, _ := u.User.Password()
+		auth = &proxy.Auth{User: u.User.Username(), Password: pw}
+	}
+
+	dialer, err := proxy.SOCKS5("tcp", u.Host, auth, proxy.Direct)
+	if err != nil {
+		return nil, fmt.Errorf("create socks5 dialer: %w", err)
+	}
+
+	conn, err := dialer.Dial("tcp", addr)
+	if err != nil {
+		return nil, fmt.Errorf("proxy dial: %w", err)
+	}
+
+	host, _, splitErr := net.SplitHostPort(addr)
+	if splitErr != nil || host == "" {
+		host = addr
+	}
+	tlsConn := tls.Client(conn, &tls.Config{ServerName: host})
+	if err := tlsConn.Handshake(); err != nil {
+		_ = tlsConn.Close()
+		return nil, fmt.Errorf("tls handshake: %w", err)
+	}
+
+	return imapclient.New(tlsConn, options), nil
+}
+
 // fetchUnseen searches for UNSEEN messages and processes each one.
 func (w *IMAPWatcher) fetchUnseen(c *imapclient.Client) error {
 	criteria := &imap.SearchCriteria{