1 // Copyright 2020 The Chromium Authors 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef BASE_STRINGS_ESCAPE_H_ 6 #define BASE_STRINGS_ESCAPE_H_ 7 8 #include <stdint.h> 9 10 #include <set> 11 #include <string> 12 13 #include "base/base_export.h" 14 #include "base/strings/string_piece.h" 15 #include "base/strings/utf_offset_string_conversions.h" 16 #include "build/build_config.h" 17 18 namespace base { 19 20 // Escaping -------------------------------------------------------------------- 21 22 // Escapes all characters except unreserved characters. Unreserved characters, 23 // as defined in RFC 3986, include alphanumerics and -._~ 24 BASE_EXPORT std::string EscapeAllExceptUnreserved(StringPiece text); 25 26 // Escapes characters in text suitable for use as a query parameter value. 27 // We %XX everything except alphanumerics and -_.!~*'() 28 // Spaces change to "+" unless you pass usePlus=false. 29 // This is basically the same as encodeURIComponent in javascript. 30 BASE_EXPORT std::string EscapeQueryParamValue(StringPiece text, bool use_plus); 31 32 // Escapes a partial or complete file/pathname. This includes: 33 // non-printable, non-7bit, and (including space) "#%:<>?[\]^`{|} 34 BASE_EXPORT std::string EscapePath(StringPiece path); 35 36 #if BUILDFLAG(IS_APPLE) 37 // Escapes characters as per expectations of NSURL. This includes: 38 // non-printable, non-7bit, and (including space) "#%<>[\]^`{|} 39 BASE_EXPORT std::string EscapeNSURLPrecursor(StringPiece precursor); 40 #endif // BUILDFLAG(IS_APPLE) 41 42 // Escapes application/x-www-form-urlencoded content. This includes: 43 // non-printable, non-7bit, and (including space) ?>=<;+'&%$#"![\]^`{|} 44 // Space is escaped as + (if use_plus is true) and other special characters 45 // as %XX (hex). 46 BASE_EXPORT std::string EscapeUrlEncodedData(StringPiece path, bool use_plus); 47 48 // Escapes all non-ASCII input, as well as escaping % to %25. 49 BASE_EXPORT std::string EscapeNonASCIIAndPercent(StringPiece input); 50 51 // Escapes all non-ASCII input. Note this function leaves % unescaped, which 52 // means the unescaping the resulting string will not give back the original 53 // input. 54 BASE_EXPORT std::string EscapeNonASCII(StringPiece input); 55 56 // Escapes characters in text suitable for use as an external protocol handler 57 // command. 58 // We %XX everything except alphanumerics and -_.!~*'() and the restricted 59 // characters (;/?:@&=+$,#[]) and a valid percent escape sequence (%XX). 60 BASE_EXPORT std::string EscapeExternalHandlerValue(StringPiece text); 61 62 // Appends the given character to the output string, escaping the character if 63 // the character would be interpreted as an HTML delimiter. 64 BASE_EXPORT void AppendEscapedCharForHTML(char c, std::string* output); 65 66 // Escapes chars that might cause this text to be interpreted as HTML tags. 67 BASE_EXPORT std::string EscapeForHTML(StringPiece text); 68 BASE_EXPORT std::u16string EscapeForHTML(StringPiece16 text); 69 70 // Unescaping ------------------------------------------------------------------ 71 72 class UnescapeRule { 73 public: 74 // A combination of the following flags that is passed to the unescaping 75 // functions. 76 typedef uint32_t Type; 77 78 // Don't unescape anything at all. 79 static constexpr Type NONE = 0; 80 81 // Don't unescape anything special, but all normal unescaping will happen. 82 // This is a placeholder and can't be combined with other flags (since it's 83 // just the absence of them). All other unescape rules imply "normal" in 84 // addition to their special meaning. Things like escaped letters, digits, 85 // and most symbols will get unescaped with this mode. 86 static constexpr Type NORMAL = 1 << 0; 87 88 // Convert %20 to spaces. In some places where we're showing URLs, we may 89 // want this. In places where the URL may be copied and pasted out, then 90 // you wouldn't want this since it might not be interpreted in one piece 91 // by other applications. Other UTF-8 spaces will not be unescaped. 92 static constexpr Type SPACES = 1 << 1; 93 94 // Unescapes '/' and '\\'. If these characters were unescaped, the resulting 95 // URL won't be the same as the source one. Moreover, they are dangerous to 96 // unescape in strings that will be used as file paths or names. This value 97 // should only be used when slashes don't have special meaning, like data 98 // URLs. 99 static constexpr Type PATH_SEPARATORS = 1 << 2; 100 101 // Unescapes various characters that will change the meaning of URLs, 102 // including '%', '+', '&', '#'. Does not unescape path separators. 103 // If these characters were unescaped, the resulting URL won't be the same 104 // as the source one. This flag is used when generating final output like 105 // filenames for URLs where we won't be interpreting as a URL and want to do 106 // as much unescaping as possible. 107 static constexpr Type URL_SPECIAL_CHARS_EXCEPT_PATH_SEPARATORS = 1 << 3; 108 109 // URL queries use "+" for space. This flag controls that replacement. 110 static constexpr Type REPLACE_PLUS_WITH_SPACE = 1 << 4; 111 }; 112 113 // Unescapes |escaped_text| and returns the result. 114 // Unescaping consists of looking for the exact pattern "%XX", where each X is 115 // a hex digit, and converting to the character with the numerical value of 116 // those digits. Thus "i%20=%203%3b" unescapes to "i = 3;", if the 117 // "UnescapeRule::SPACES" used. 118 // 119 // This method does not ensure that the output is a valid string using any 120 // character encoding. However, it does leave escaped certain byte sequences 121 // that would be dangerous to display to the user, because if interpreted as 122 // UTF-8, they could be used to mislead the user. Callers that want to 123 // unconditionally unescape everything for uses other than displaying data to 124 // the user should use UnescapeBinaryURLComponent(). 125 BASE_EXPORT std::string UnescapeURLComponent(StringPiece escaped_text, 126 UnescapeRule::Type rules); 127 128 // Unescapes the given substring as a URL, and then tries to interpret the 129 // result as being encoded as UTF-8. If the result is convertible into UTF-8, it 130 // will be returned as converted. If it is not, the original escaped string will 131 // be converted into a std::u16string and returned. |adjustments| provides 132 // information on how the original string was adjusted to get the string 133 // returned. 134 BASE_EXPORT std::u16string UnescapeAndDecodeUTF8URLComponentWithAdjustments( 135 StringPiece text, 136 UnescapeRule::Type rules, 137 OffsetAdjuster::Adjustments* adjustments); 138 139 // Unescapes a component of a URL for use as binary data. Unlike 140 // UnescapeURLComponent, leaves nothing unescaped, including nulls, invalid 141 // characters, characters that are unsafe to display, etc. This should *not* 142 // be used when displaying the decoded data to the user. 143 // 144 // Only the NORMAL and REPLACE_PLUS_WITH_SPACE rules are allowed. 145 BASE_EXPORT std::string UnescapeBinaryURLComponent( 146 StringPiece escaped_text, 147 UnescapeRule::Type rules = UnescapeRule::NORMAL); 148 149 // Variant of UnescapeBinaryURLComponent(). Writes output to |unescaped_text|. 150 // Returns true on success, returns false and clears |unescaped_text| on 151 // failure. Fails on characters escaped that are unsafe to unescape in some 152 // contexts, which are defined as characters "\0" through "\x1F" (Which includes 153 // CRLF but not space), and optionally path separators. Path separators include 154 // both forward and backward slashes on all platforms. Does not fail if any of 155 // those characters appear unescaped in the input string. 156 BASE_EXPORT bool UnescapeBinaryURLComponentSafe(StringPiece escaped_text, 157 bool fail_on_path_separators, 158 std::string* unescaped_text); 159 160 // Returns true if |escaped_text| contains any element of |bytes| in 161 // percent-encoded form. 162 // 163 // For example, if |bytes| is {'%', '/'}, returns true if |escaped_text| 164 // contains "%25" or "%2F", but not if it just contains bare '%' or '/' 165 // characters. 166 BASE_EXPORT bool ContainsEncodedBytes(StringPiece escaped_text, 167 const std::set<unsigned char>& bytes); 168 169 // Unescapes the following ampersand character codes from |text|: 170 // < > & " ' 171 BASE_EXPORT std::u16string UnescapeForHTML(StringPiece16 text); 172 173 } // namespace base 174 175 #endif // BASE_STRINGS_ESCAPE_H_ 176