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// Copyright 2017 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package httpproxy provides support for HTTP proxy determination
// based on environment variables, as provided by net/http's
// ProxyFromEnvironment function.
//
// The API is not subject to the Go 1 compatibility promise and may change at
// any time.
package httpproxy
import (
"errors"
"fmt"
"net"
"net/url"
"os"
"strings"
"unicode/utf8"
"golang.org/x/net/idna"
)
// Config holds configuration for HTTP proxy settings. See
// FromEnvironment for details.
type Config struct {
// HTTPProxy represents the value of the HTTP_PROXY or
// http_proxy environment variable. It will be used as the proxy
// URL for HTTP requests and HTTPS requests unless overridden by
// HTTPSProxy or NoProxy.
HTTPProxy string
// HTTPSProxy represents the HTTPS_PROXY or https_proxy
// environment variable. It will be used as the proxy URL for
// HTTPS requests unless overridden by NoProxy.
HTTPSProxy string
// NoProxy represents the NO_PROXY or no_proxy environment
// variable. It specifies a string that contains comma-separated values
// specifying hosts that should be excluded from proxying. Each value is
// represented by an IP address prefix (1.2.3.4), an IP address prefix in
// CIDR notation (1.2.3.4/8), a domain name, or a special DNS label (*).
// An IP address prefix and domain name can also include a literal port
// number (1.2.3.4:80).
// A domain name matches that name and all subdomains. A domain name with
// a leading "." matches subdomains only. For example "foo.com" matches
// "foo.com" and "bar.foo.com"; ".y.com" matches "x.y.com" but not "y.com".
// A single asterisk (*) indicates that no proxying should be done.
// A best effort is made to parse the string and errors are
// ignored.
NoProxy string
// CGI holds whether the current process is running
// as a CGI handler (FromEnvironment infers this from the
// presence of a REQUEST_METHOD environment variable).
// When this is set, ProxyForURL will return an error
// when HTTPProxy applies, because a client could be
// setting HTTP_PROXY maliciously. See https://golang.org/s/cgihttpproxy.
CGI bool
}
// config holds the parsed configuration for HTTP proxy settings.
type config struct {
// Config represents the original configuration as defined above.
Config
// httpsProxy is the parsed URL of the HTTPSProxy if defined.
httpsProxy *url.URL
// httpProxy is the parsed URL of the HTTPProxy if defined.
httpProxy *url.URL
// ipMatchers represent all values in the NoProxy that are IP address
// prefixes or an IP address in CIDR notation.
ipMatchers []matcher
// domainMatchers represent all values in the NoProxy that are a domain
// name or hostname & domain name
domainMatchers []matcher
}
// FromEnvironment returns a Config instance populated from the
// environment variables HTTP_PROXY, HTTPS_PROXY and NO_PROXY (or the
// lowercase versions thereof). HTTPS_PROXY takes precedence over
// HTTP_PROXY for https requests.
//
// The environment values may be either a complete URL or a
// "host[:port]", in which case the "http" scheme is assumed. An error
// is returned if the value is a different form.
func FromEnvironment() *Config {
return &Config{
HTTPProxy: getEnvAny("HTTP_PROXY", "http_proxy"),
HTTPSProxy: getEnvAny("HTTPS_PROXY", "https_proxy"),
NoProxy: getEnvAny("NO_PROXY", "no_proxy"),
CGI: os.Getenv("REQUEST_METHOD") != "",
}
}
func getEnvAny(names ...string) string {
for _, n := range names {
if val := os.Getenv(n); val != "" {
return val
}
}
return ""
}
// ProxyFunc returns a function that determines the proxy URL to use for
// a given request URL. Changing the contents of cfg will not affect
// proxy functions created earlier.
//
// A nil URL and nil error are returned if no proxy is defined in the
// environment, or a proxy should not be used for the given request, as
// defined by NO_PROXY.
//
// As a special case, if req.URL.Host is "localhost" (with or without a
// port number), then a nil URL and nil error will be returned.
func (cfg *Config) ProxyFunc() func(reqURL *url.URL) (*url.URL, error) {
// Preprocess the Config settings for more efficient evaluation.
cfg1 := &config{
Config: *cfg,
}
cfg1.init()
return cfg1.proxyForURL
}
func (cfg *config) proxyForURL(reqURL *url.URL) (*url.URL, error) {
var proxy *url.URL
if reqURL.Scheme == "https" {
proxy = cfg.httpsProxy
}
if proxy == nil {
proxy = cfg.httpProxy
if proxy != nil && cfg.CGI {
return nil, errors.New("refusing to use HTTP_PROXY value in CGI environment; see golang.org/s/cgihttpproxy")
}
}
if proxy == nil {
return nil, nil
}
if !cfg.useProxy(canonicalAddr(reqURL)) {
return nil, nil
}
return proxy, nil
}
func parseProxy(proxy string) (*url.URL, error) {
if proxy == "" {
return nil, nil
}
proxyURL, err := url.Parse(proxy)
if err != nil ||
(proxyURL.Scheme != "http" &&
proxyURL.Scheme != "https" &&
proxyURL.Scheme != "socks5") {
// proxy was bogus. Try prepending "http://" to it and
// see if that parses correctly. If not, we fall
// through and complain about the original one.
if proxyURL, err := url.Parse("http://" + proxy); err == nil {
return proxyURL, nil
}
}
if err != nil {
return nil, fmt.Errorf("invalid proxy address %q: %v", proxy, err)
}
return proxyURL, nil
}
// useProxy reports whether requests to addr should use a proxy,
// according to the NO_PROXY or no_proxy environment variable.
// addr is always a canonicalAddr with a host and port.
func (cfg *config) useProxy(addr string) bool {
if len(addr) == 0 {
return true
}
host, port, err := net.SplitHostPort(addr)
if err != nil {
return false
}
if host == "localhost" {
return false
}
ip := net.ParseIP(host)
if ip != nil {
if ip.IsLoopback() {
return false
}
}
addr = strings.ToLower(strings.TrimSpace(host))
if ip != nil {
for _, m := range cfg.ipMatchers {
if m.match(addr, port, ip) {
return false
}
}
}
for _, m := range cfg.domainMatchers {
if m.match(addr, port, ip) {
return false
}
}
return true
}
func (c *config) init() {
if parsed, err := parseProxy(c.HTTPProxy); err == nil {
c.httpProxy = parsed
}
if parsed, err := parseProxy(c.HTTPSProxy); err == nil {
c.httpsProxy = parsed
}
for _, p := range strings.Split(c.NoProxy, ",") {
p = strings.ToLower(strings.TrimSpace(p))
if len(p) == 0 {
continue
}
if p == "*" {
c.ipMatchers = []matcher{allMatch{}}
c.domainMatchers = []matcher{allMatch{}}
return
}
// IPv4/CIDR, IPv6/CIDR
if _, pnet, err := net.ParseCIDR(p); err == nil {
c.ipMatchers = append(c.ipMatchers, cidrMatch{cidr: pnet})
continue
}
// IPv4:port, [IPv6]:port
phost, pport, err := net.SplitHostPort(p)
if err == nil {
if len(phost) == 0 {
// There is no host part, likely the entry is malformed; ignore.
continue
}
if phost[0] == '[' && phost[len(phost)-1] == ']' {
phost = phost[1 : len(phost)-1]
}
} else {
phost = p
}
// IPv4, IPv6
if pip := net.ParseIP(phost); pip != nil {
c.ipMatchers = append(c.ipMatchers, ipMatch{ip: pip, port: pport})
continue
}
if len(phost) == 0 {
// There is no host part, likely the entry is malformed; ignore.
continue
}
// domain.com or domain.com:80
// foo.com matches bar.foo.com
// .domain.com or .domain.com:port
// *.domain.com or *.domain.com:port
if strings.HasPrefix(phost, "*.") {
phost = phost[1:]
}
matchHost := false
if phost[0] != '.' {
matchHost = true
phost = "." + phost
}
c.domainMatchers = append(c.domainMatchers, domainMatch{host: phost, port: pport, matchHost: matchHost})
}
}
var portMap = map[string]string{
"http": "80",
"https": "443",
"socks5": "1080",
}
// canonicalAddr returns url.Host but always with a ":port" suffix
func canonicalAddr(url *url.URL) string {
addr := url.Hostname()
if v, err := idnaASCII(addr); err == nil {
addr = v
}
port := url.Port()
if port == "" {
port = portMap[url.Scheme]
}
return net.JoinHostPort(addr, port)
}
// Given a string of the form "host", "host:port", or "[ipv6::address]:port",
// return true if the string includes a port.
func hasPort(s string) bool { return strings.LastIndex(s, ":") > strings.LastIndex(s, "]") }
func idnaASCII(v string) (string, error) {
// TODO: Consider removing this check after verifying performance is okay.
// Right now punycode verification, length checks, context checks, and the
// permissible character tests are all omitted. It also prevents the ToASCII
// call from salvaging an invalid IDN, when possible. As a result it may be
// possible to have two IDNs that appear identical to the user where the
// ASCII-only version causes an error downstream whereas the non-ASCII
// version does not.
// Note that for correct ASCII IDNs ToASCII will only do considerably more
// work, but it will not cause an allocation.
if isASCII(v) {
return v, nil
}
return idna.Lookup.ToASCII(v)
}
func isASCII(s string) bool {
for i := 0; i < len(s); i++ {
if s[i] >= utf8.RuneSelf {
return false
}
}
return true
}
// matcher represents the matching rule for a given value in the NO_PROXY list
type matcher interface {
// match returns true if the host and optional port or ip and optional port
// are allowed
match(host, port string, ip net.IP) bool
}
// allMatch matches on all possible inputs
type allMatch struct{}
func (a allMatch) match(host, port string, ip net.IP) bool {
return true
}
type cidrMatch struct {
cidr *net.IPNet
}
func (m cidrMatch) match(host, port string, ip net.IP) bool {
return m.cidr.Contains(ip)
}
type ipMatch struct {
ip net.IP
port string
}
func (m ipMatch) match(host, port string, ip net.IP) bool {
if m.ip.Equal(ip) {
return m.port == "" || m.port == port
}
return false
}
type domainMatch struct {
host string
port string
matchHost bool
}
func (m domainMatch) match(host, port string, ip net.IP) bool {
if strings.HasSuffix(host, m.host) || (m.matchHost && host == m.host[1:]) {
return m.port == "" || m.port == port
}
return false
}
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