240 lines
7 KiB
Go
240 lines
7 KiB
Go
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// Copyright 2017 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package httpproxy provides support for HTTP proxy determination
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// based on environment variables, as provided by net/http's
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// ProxyFromEnvironment function.
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//
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// The API is not subject to the Go 1 compatibility promise and may change at
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// any time.
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package httpproxy
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import (
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"errors"
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"fmt"
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"net"
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"net/url"
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"os"
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"strings"
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"unicode/utf8"
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"golang.org/x/net/idna"
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)
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// Config holds configuration for HTTP proxy settings. See
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// FromEnvironment for details.
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type Config struct {
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// HTTPProxy represents the value of the HTTP_PROXY or
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// http_proxy environment variable. It will be used as the proxy
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// URL for HTTP requests and HTTPS requests unless overridden by
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// HTTPSProxy or NoProxy.
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HTTPProxy string
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// HTTPSProxy represents the HTTPS_PROXY or https_proxy
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// environment variable. It will be used as the proxy URL for
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// HTTPS requests unless overridden by NoProxy.
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HTTPSProxy string
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// NoProxy represents the NO_PROXY or no_proxy environment
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// variable. It specifies URLs that should be excluded from
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// proxying as a comma-separated list of domain names or a
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// single asterisk (*) to indicate that no proxying should be
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// done. A domain name matches that name and all subdomains. A
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// domain name with a leading "." matches subdomains only. For
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// example "foo.com" matches "foo.com" and "bar.foo.com";
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// ".y.com" matches "x.y.com" but not "y.com".
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NoProxy string
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// CGI holds whether the current process is running
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// as a CGI handler (FromEnvironment infers this from the
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// presence of a REQUEST_METHOD environment variable).
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// When this is set, ProxyForURL will return an error
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// when HTTPProxy applies, because a client could be
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// setting HTTP_PROXY maliciously. See https://golang.org/s/cgihttpproxy.
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CGI bool
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}
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// FromEnvironment returns a Config instance populated from the
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// environment variables HTTP_PROXY, HTTPS_PROXY and NO_PROXY (or the
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// lowercase versions thereof). HTTPS_PROXY takes precedence over
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// HTTP_PROXY for https requests.
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//
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// The environment values may be either a complete URL or a
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// "host[:port]", in which case the "http" scheme is assumed. An error
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// is returned if the value is a different form.
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func FromEnvironment() *Config {
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return &Config{
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HTTPProxy: getEnvAny("HTTP_PROXY", "http_proxy"),
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HTTPSProxy: getEnvAny("HTTPS_PROXY", "https_proxy"),
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NoProxy: getEnvAny("NO_PROXY", "no_proxy"),
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CGI: os.Getenv("REQUEST_METHOD") != "",
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}
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}
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func getEnvAny(names ...string) string {
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for _, n := range names {
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if val := os.Getenv(n); val != "" {
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return val
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}
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}
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return ""
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}
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// ProxyFunc returns a function that determines the proxy URL to use for
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// a given request URL. Changing the contents of cfg will not affect
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// proxy functions created earlier.
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//
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// A nil URL and nil error are returned if no proxy is defined in the
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// environment, or a proxy should not be used for the given request, as
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// defined by NO_PROXY.
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//
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// As a special case, if req.URL.Host is "localhost" (with or without a
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// port number), then a nil URL and nil error will be returned.
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func (cfg *Config) ProxyFunc() func(reqURL *url.URL) (*url.URL, error) {
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// Prevent Config changes from affecting the function calculation.
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// TODO Preprocess proxy settings for more efficient evaluation.
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cfg1 := *cfg
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return cfg1.proxyForURL
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}
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func (cfg *Config) proxyForURL(reqURL *url.URL) (*url.URL, error) {
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var proxy string
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if reqURL.Scheme == "https" {
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proxy = cfg.HTTPSProxy
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}
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if proxy == "" {
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proxy = cfg.HTTPProxy
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if proxy != "" && cfg.CGI {
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return nil, errors.New("refusing to use HTTP_PROXY value in CGI environment; see golang.org/s/cgihttpproxy")
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}
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}
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if proxy == "" {
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return nil, nil
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}
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if !cfg.useProxy(canonicalAddr(reqURL)) {
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return nil, nil
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}
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proxyURL, err := url.Parse(proxy)
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if err != nil ||
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(proxyURL.Scheme != "http" &&
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proxyURL.Scheme != "https" &&
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proxyURL.Scheme != "socks5") {
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// proxy was bogus. Try prepending "http://" to it and
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// see if that parses correctly. If not, we fall
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// through and complain about the original one.
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if proxyURL, err := url.Parse("http://" + proxy); err == nil {
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return proxyURL, nil
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}
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}
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if err != nil {
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return nil, fmt.Errorf("invalid proxy address %q: %v", proxy, err)
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}
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return proxyURL, nil
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}
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// useProxy reports whether requests to addr should use a proxy,
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// according to the NO_PROXY or no_proxy environment variable.
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// addr is always a canonicalAddr with a host and port.
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func (cfg *Config) useProxy(addr string) bool {
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if len(addr) == 0 {
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return true
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}
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host, _, err := net.SplitHostPort(addr)
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if err != nil {
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return false
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}
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if host == "localhost" {
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return false
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}
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if ip := net.ParseIP(host); ip != nil {
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if ip.IsLoopback() {
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return false
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}
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}
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noProxy := cfg.NoProxy
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if noProxy == "*" {
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return false
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}
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addr = strings.ToLower(strings.TrimSpace(addr))
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if hasPort(addr) {
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addr = addr[:strings.LastIndex(addr, ":")]
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}
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for _, p := range strings.Split(noProxy, ",") {
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p = strings.ToLower(strings.TrimSpace(p))
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if len(p) == 0 {
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continue
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}
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if hasPort(p) {
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p = p[:strings.LastIndex(p, ":")]
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}
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if addr == p {
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return false
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}
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if len(p) == 0 {
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// There is no host part, likely the entry is malformed; ignore.
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continue
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}
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if p[0] == '.' && (strings.HasSuffix(addr, p) || addr == p[1:]) {
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// no_proxy ".foo.com" matches "bar.foo.com" or "foo.com"
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return false
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}
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if p[0] != '.' && strings.HasSuffix(addr, p) && addr[len(addr)-len(p)-1] == '.' {
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// no_proxy "foo.com" matches "bar.foo.com"
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return false
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}
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}
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return true
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}
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var portMap = map[string]string{
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"http": "80",
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"https": "443",
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"socks5": "1080",
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}
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// canonicalAddr returns url.Host but always with a ":port" suffix
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func canonicalAddr(url *url.URL) string {
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addr := url.Hostname()
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if v, err := idnaASCII(addr); err == nil {
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addr = v
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}
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port := url.Port()
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if port == "" {
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port = portMap[url.Scheme]
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}
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return net.JoinHostPort(addr, port)
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}
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// Given a string of the form "host", "host:port", or "[ipv6::address]:port",
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// return true if the string includes a port.
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func hasPort(s string) bool { return strings.LastIndex(s, ":") > strings.LastIndex(s, "]") }
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func idnaASCII(v string) (string, error) {
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// TODO: Consider removing this check after verifying performance is okay.
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// Right now punycode verification, length checks, context checks, and the
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// permissible character tests are all omitted. It also prevents the ToASCII
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// call from salvaging an invalid IDN, when possible. As a result it may be
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// possible to have two IDNs that appear identical to the user where the
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// ASCII-only version causes an error downstream whereas the non-ASCII
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// version does not.
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// Note that for correct ASCII IDNs ToASCII will only do considerably more
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// work, but it will not cause an allocation.
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if isASCII(v) {
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return v, nil
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}
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return idna.Lookup.ToASCII(v)
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}
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func isASCII(s string) bool {
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for i := 0; i < len(s); i++ {
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if s[i] >= utf8.RuneSelf {
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return false
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}
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}
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return true
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}
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