net/base/url_util.h

// Copyright 2013 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// This file contains a set of utility functions related to parsing,
// manipulating, and interacting with URLs and hostnames. These functions are
// intended to be of a text-processing nature, and should not attempt to use any
// networking or blocking services.

#ifndef NET_BASE_URL_UTIL_H_
#define NET_BASE_URL_UTIL_H_

#include <optional>
#include <string>
#include <string_view>

#include "base/memory/raw_ref.h"
#include "net/base/net_export.h"
#include "url/third_party/mozilla/url_parse.h"

class GURL;

namespace url {
struct CanonHostInfo;
class SchemeHostPort;
}  // namespace url

namespace net {

// Returns a new GURL by appending the given query parameter name and the
// value. Unsafe characters in the name and the value are escaped like
// %XX%XX. The original query component is preserved if it's present.
//
// Examples:
//
// AppendQueryParameter(GURL("http://example.com"), "name", "value").spec()
// => "http://example.com?name=value"
// AppendQueryParameter(GURL("http://example.com?x=y"), "name", "value").spec()
// => "http://example.com?x=y&name=value"
NET_EXPORT GURL AppendQueryParameter(const GURL& url,
                                     std::string_view name,
                                     std::string_view value);

// Returns a new GURL by appending or replacing the given query parameter name
// and the value. If `name` appears more than once, only the first name-value
// pair is replaced. Unsafe characters in the name and the value are escaped
// like %XX%XX. The original query component is preserved if it's present.
// Using `std::nullopt` for `value` will remove the `name` parameter.
//
// Examples:
//
// AppendOrReplaceQueryParameter(
//     GURL("http://example.com"), "name", "new").spec()
// => "http://example.com?name=value"
// AppendOrReplaceQueryParameter(
//     GURL("http://example.com?x=y&name=old"), "name", "new").spec()
// => "http://example.com?x=y&name=new"
// AppendOrReplaceQueryParameter(
//     GURL("http://example.com?x=y&name=old"), "name", std::nullopt).spec()
// => "http://example.com?x=y&"
NET_EXPORT GURL
AppendOrReplaceQueryParameter(const GURL& url,
                              std::string_view name,
                              std::optional<std::string_view> value);

// Returns a new GURL by appending the provided ref (also named fragment).
// Unsafe characters are escaped. The original fragment is replaced
// if it's present.
//
// Examples:
//
// AppendOrReplaceRef(
//     GURL("http://example.com"), "ref").spec()
// => "http://example.com#ref"
// AppendOrReplaceRef(
//     GURL("http://example.com#ref"), "ref2").spec()
// => "http://example.com#ref2"
NET_EXPORT GURL AppendOrReplaceRef(const GURL& url,
                                   const std::string_view& ref);

// Iterates over the key-value pairs in the query portion of |url|.
// NOTE: QueryIterator stores reference to |url| and creates std::string_view
// instances which refer to the data inside |url| query. Therefore |url| must
// outlive QueryIterator and all std::string_view objects returned from GetKey
// and GetValue methods.
class NET_EXPORT QueryIterator {
 public:
  explicit QueryIterator(const GURL& url);
  QueryIterator(const QueryIterator&) = delete;
  QueryIterator& operator=(const QueryIterator&) = delete;
  ~QueryIterator();

  std::string_view GetKey() const;
  std::string_view GetValue() const;
  const std::string& GetUnescapedValue();

  bool IsAtEnd() const;
  void Advance();

 private:
  const raw_ref<const GURL> url_;
  url::Component query_;
  bool at_end_;
  url::Component key_;
  url::Component value_;
  std::string unescaped_value_;
};

// Looks for |search_key| in the query portion of |url|. Returns true if the
// key is found and sets |out_value| to the unescaped value for the key.
// Returns false if the key is not found.
NET_EXPORT bool GetValueForKeyInQuery(const GURL& url,
                                      std::string_view search_key,
                                      std::string* out_value);

// Splits an input of the form <host>[":"<port>] into its consitituent parts.
// Saves the result into |*host| and |*port|. If the input did not have
// the optional port, sets |*port| to -1.
// Returns true if the parsing was successful, false otherwise.
// The returned host is NOT canonicalized, and may be invalid.
//
// IPv6 literals must be specified in a bracketed form, for instance:
//   [::1]:90 and [::1]
//
// The resultant |*host| in both cases will be "::1" (not bracketed).
NET_EXPORT bool ParseHostAndPort(std::string_view input,
                                 std::string* host,
                                 int* port);

// Returns a host:port string for the given URL.
NET_EXPORT std::string GetHostAndPort(const GURL& url);

// Returns a host[:port] string for the given URL, where the port is omitted
// if it is the default for the URL's scheme.
NET_EXPORT std::string GetHostAndOptionalPort(const GURL& url);

// Just like above, but takes a SchemeHostPort.
NET_EXPORT std::string GetHostAndOptionalPort(
    const url::SchemeHostPort& scheme_host_port);

// Returns the hostname by trimming the ending dot, if one exists.
NET_EXPORT std::string TrimEndingDot(std::string_view host);

// Returns either the host from |url|, or, if the host is empty, the full spec.
NET_EXPORT std::string GetHostOrSpecFromURL(const GURL& url);

// Returns the given domain minus its leftmost label, or the empty string if the
// given domain is just a single label. For normal domain names (not IP
// addresses), this represents the "superdomain" of the given domain.
// Note that this does not take into account anything like the Public Suffix
// List, so the superdomain may end up being a bare eTLD. The returned string is
// not guaranteed to be a valid or canonical hostname, or to make any sense at
// all.
//
// Examples:
//
// GetSuperdomain("assets.example.com") -> "example.com"
// GetSuperdomain("example.net") -> "net"
// GetSuperdomain("littlebox") -> ""
// GetSuperdomain("127.0.0.1") -> "0.0.1"
NET_EXPORT std::string GetSuperdomain(std::string_view domain);

// Returns whether |subdomain| is a subdomain of (or identical to)
// |superdomain|, if both are hostnames (not IP addresses -- for which this
// function is nonsensical). Does not consider the Public Suffix List.
// Returns true if both input strings are empty.
NET_EXPORT bool IsSubdomainOf(std::string_view subdomain,
                              std::string_view superdomain);

// Canonicalizes |host| and returns it.  Also fills |host_info| with
// IP address information.  |host_info| must not be NULL.
NET_EXPORT std::string CanonicalizeHost(std::string_view host,
                                        url::CanonHostInfo* host_info);

// Returns true if |host| is not an IP address and is compliant with a set of
// rules based on RFC 1738 and tweaked to be compatible with the real world.
// The rules are:
//   * One or more non-empty labels separated by '.', each no more than 63
//     characters.
//   * Each component contains only alphanumeric characters and '-' or '_'
//   * The last component begins with an alphanumeric character
//   * Optional trailing dot after last component (means "treat as FQDN")
//   * Total size (including optional trailing dot, whether or not actually
//     present in `host`) no more than 254 characters.
//
// NOTE: You should only pass in hosts that have been returned from
// CanonicalizeHost(), or you may not get accurate results.
NET_EXPORT bool IsCanonicalizedHostCompliant(std::string_view host);

// Returns true if |hostname| contains a non-registerable or non-assignable
// domain name (eg: a gTLD that has not been assigned by IANA) or an IP address
// that falls in an range reserved for non-publicly routable networks.
NET_EXPORT bool IsHostnameNonUnique(std::string_view hostname);

// Returns true if the host part of |url| is a local host name according to
// HostStringIsLocalhost.
NET_EXPORT bool IsLocalhost(const GURL& url);

// Returns true if |host| is one of the local hostnames
// (e.g. "localhost") or IP addresses (IPv4 127.0.0.0/8 or IPv6 ::1).
// "[::1]" is not detected as a local hostname. Do not use this method to check
// whether the host part of a URL is a local host name; use IsLocalhost instead.
//
// Note that this function does not check for IP addresses other than
// the above, although other IP addresses may point to the local
// machine.
NET_EXPORT bool HostStringIsLocalhost(std::string_view host);

// Strip the portions of |url| that aren't core to the network request.
//   - user name / password
//   - reference section
NET_EXPORT GURL SimplifyUrlForRequest(const GURL& url);

// Changes scheme "ws" to "http" and "wss" to "https". This is useful for origin
// checks and authentication, where WebSocket URLs are treated as if they were
// HTTP. It is an error to call this function with a url with a scheme other
// than "ws" or "wss".
NET_EXPORT GURL ChangeWebSocketSchemeToHttpScheme(const GURL& url);

// Returns whether the given url scheme is of a standard scheme type that can
// have hostnames representing domains (i.e. network hosts).
// See url::SchemeType.
NET_EXPORT bool IsStandardSchemeWithNetworkHost(std::string_view scheme);

// Extracts the unescaped username/password from |url|, saving the results
// into |*username| and |*password|.
NET_EXPORT_PRIVATE void GetIdentityFromURL(const GURL& url,
                                           std::u16string* username,
                                           std::u16string* password);

// Returns true if the url's host is a Google server. This should only be used
// for histograms and shouldn't be used to affect behavior.
NET_EXPORT_PRIVATE bool HasGoogleHost(const GURL& url);

// Returns true if |host| is the hostname of a Google server. This should only
// be used for histograms and shouldn't be used to affect behavior.
NET_EXPORT_PRIVATE bool IsGoogleHost(std::string_view host);

// Returns true if |host| is the hostname of a Google server and HTTPS DNS
// record of |host| is expected to indicate H3 support. This should only be used
// for histograms and shouldn't be used to affect behavior.
NET_EXPORT_PRIVATE bool IsGoogleHostWithAlpnH3(std::string_view host);

// This function tests |host| to see if it is of any local hostname form.
// |host| is normalized before being tested.
NET_EXPORT_PRIVATE bool IsLocalHostname(std::string_view host);

// The notion of unescaping used in the application/x-www-form-urlencoded
// parser. https://url.spec.whatwg.org/#concept-urlencoded-parser
NET_EXPORT_PRIVATE std::string UnescapePercentEncodedUrl(
    std::string_view input);

}  // namespace net

#endif  // NET_BASE_URL_UTIL_H_