1 files changed, 69 insertions, 0 deletions
diff --git a/modules/hostmatcher/http.go b/modules/hostmatcher/http.go
new file mode 100644
index 00000000..c743f6ef
--- /dev/null
+++ b/modules/hostmatcher/http.go
@@ -0,0 +1,69 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package hostmatcher
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"net/url"
+	"syscall"
+	"time"
+)
+
+// NewDialContext returns a DialContext for Transport, the DialContext will do allow/block list check
+func NewDialContext(usage string, allowList, blockList *HostMatchList) func(ctx context.Context, network, addr string) (net.Conn, error) {
+	return NewDialContextWithProxy(usage, allowList, blockList, nil)
+}
+
+func NewDialContextWithProxy(usage string, allowList, blockList *HostMatchList, proxy *url.URL) func(ctx context.Context, network, addr string) (net.Conn, error) {
+	// How Go HTTP Client works with redirection:
+	//   transport.RoundTrip URL=http://domain.com, Host=domain.com
+	//   transport.DialContext addrOrHost=domain.com:80
+	//   dialer.Control tcp4:11.22.33.44:80
+	//   transport.RoundTrip URL=http://www.domain.com/, Host=(empty here, in the direction, HTTP client doesn't fill the Host field)
+	//   transport.DialContext addrOrHost=domain.com:80
+	//   dialer.Control tcp4:11.22.33.44:80
+	return func(ctx context.Context, network, addrOrHost string) (net.Conn, error) {
+		dialer := net.Dialer{
+			// default values comes from http.DefaultTransport
+			Timeout:   30 * time.Second,
+			KeepAlive: 30 * time.Second,
+
+			Control: func(network, ipAddr string, c syscall.RawConn) error {
+				host, port, err := net.SplitHostPort(addrOrHost)
+				if err != nil {
+					return err
+				}
+				if proxy != nil {
+					// Always allow the host of the proxy, but only on the specified port.
+					if host == proxy.Hostname() && port == proxy.Port() {
+						return nil
+					}
+				}
+
+				// in Control func, the addr was already resolved to IP:PORT format, there is no cost to do ResolveTCPAddr here
+				tcpAddr, err := net.ResolveTCPAddr(network, ipAddr)
+				if err != nil {
+					return fmt.Errorf("%s can only call HTTP servers via TCP, deny '%s(%s:%s)', err=%w", usage, host, network, ipAddr, err)
+				}
+
+				var blockedError error
+				if blockList.MatchHostOrIP(host, tcpAddr.IP) {
+					blockedError = fmt.Errorf("%s can not call blocked HTTP servers (check your %s setting), deny '%s(%s)'", usage, blockList.SettingKeyHint, host, ipAddr)
+				}
+
+				// if we have an allow-list, check the allow-list first
+				if !allowList.IsEmpty() {
+					if !allowList.MatchHostOrIP(host, tcpAddr.IP) {
+						return fmt.Errorf("%s can only call allowed HTTP servers (check your %s setting), deny '%s(%s)'", usage, allowList.SettingKeyHint, host, ipAddr)
+					}
+				}
+				// otherwise, we always follow the blocked list
+				return blockedError
+			},
+		}
+		return dialer.DialContext(ctx, network, addrOrHost)
+	}
+}