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proxy.go
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proxy.go
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// Licensed to Elasticsearch B.V. under one or more contributor
// license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright
// ownership. Elasticsearch B.V. licenses this file to you under
// the Apache License, Version 2.0 (the "License"); you may
// not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License.
package transport
import (
"context"
"net"
"net/url"
"golang.org/x/net/proxy"
"github.com/elastic/elastic-agent-libs/logp"
)
// ProxyConfig holds the configuration information required to proxy
// connections through a SOCKS5 proxy server.
type ProxyConfig struct {
// URL of the SOCKS proxy. Scheme must be socks5. Username and password can be
// embedded in the URL.
URL string `config:"proxy_url"`
// Resolve names locally instead of on the SOCKS server.
LocalResolve bool `config:"proxy_use_local_resolver"`
}
func (c *ProxyConfig) Validate() error {
if c.URL == "" {
return nil
}
url, err := url.Parse(c.URL)
if err != nil {
return err
}
if _, err := proxy.FromURL(url, nil); err != nil {
return err
}
return nil
}
func ProxyDialer(log *logp.Logger, config *ProxyConfig, forward Dialer) (Dialer, error) {
if config == nil || config.URL == "" {
return forward, nil
}
url, err := url.Parse(config.URL)
if err != nil {
return nil, err
}
if _, err := proxy.FromURL(url, nil); err != nil {
return nil, err
}
log.Infof("proxy host: '%s'", url.Host)
return DialerFunc(func(ctx context.Context, network, address string) (net.Conn, error) {
var err error
var addresses []string
host, port, err := net.SplitHostPort(address)
if err != nil {
return nil, err
}
if config.LocalResolve {
addresses, err = net.LookupHost(host)
if err != nil {
log.Warnf(`DNS lookup failure "%s": %+v`, host, err)
return nil, err
}
} else {
// Do not resolve the address locally. It will be resolved on the
// SOCKS server. The beat will have no control over the randomization
// of the IP used when multiple IPs are returned by DNS.
addresses = []string{host}
}
dialer, err := proxy.FromURL(url, forward)
if err != nil {
return nil, err
}
contextDialer, ok := dialer.(Dialer)
// This will never be executed because the proxy package always returns
// a ContextDialer but they didn't break the interface for backward compatibility.
// See golang/go#58376
if !ok {
contextDialer = DialerFunc(func(ctx context.Context, network, address string) (net.Conn, error) {
return dialer.Dial(network, address)
})
}
return DialWith(ctx, contextDialer, network, host, addresses, port)
}), nil
}