// 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 unless overridden by 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" or a loopback address // (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 } else if reqURL.Scheme == "http" { 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 }