java/15 : java.base/java/net/IDN.java

https://openjdk.java.net/
GPLv2 + Classpath Exception
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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package java.net;

import java.io.InputStream;
import java.io.IOException;
import java.security.AccessController;
import java.security.PrivilegedAction;

import jdk.internal.icu.impl.Punycode;
import jdk.internal.icu.text.StringPrep;
import jdk.internal.icu.text.UCharacterIterator;

Provides methods to convert internationalized domain names (IDNs) between
a normal Unicode representation and an ASCII Compatible Encoding (ACE) representation.
Internationalized domain names can use characters from the entire range of
Unicode, while traditional domain names are restricted to ASCII characters.
ACE is an encoding of Unicode strings that uses only ASCII characters and
can be used with software (such as the Domain Name System) that only
understands traditional domain names.
Internationalized domain names are defined in RFC 3490.
RFC 3490 defines two operations: ToASCII and ToUnicode. These 2 operations employ
Nameprep algorithm, which is a
profile of Stringprep, and
Punycode algorithm to convert
domain name string back and forth.
The behavior of aforementioned conversion process can be adjusted by various flags:
  

    If the ALLOW_UNASSIGNED flag is used, the domain name string to be converted
        can contain code points that are unassigned in Unicode 3.2, which is the
        Unicode version on which IDN conversion is based. If the flag is not used,
        the presence of such unassigned code points is treated as an error.
    
If the USE_STD3_ASCII_RULES flag is used, ASCII strings are checked against RFC 1122 and RFC 1123.
        It is an error if they don't meet the requirements.
  
These flags can be logically OR'ed together.
The security consideration is important with respect to internationalization
domain name support. For example, English domain names may be homographed
- maliciously misspelled by substitution of non-Latin letters.
Unicode Technical Report #36
discusses security issues of IDN support as well as possible solutions.
Applications are responsible for taking adequate security measures when using
international domain names.
Author: Edward Wang
Since: 1.6/**
 * Provides methods to convert internationalized domain names (IDNs) between
 * a normal Unicode representation and an ASCII Compatible Encoding (ACE) representation.
 * Internationalized domain names can use characters from the entire range of
 * Unicode, while traditional domain names are restricted to ASCII characters.
 * ACE is an encoding of Unicode strings that uses only ASCII characters and
 * can be used with software (such as the Domain Name System) that only
 * understands traditional domain names.
 *
 * <p>Internationalized domain names are defined in <a href="http://www.ietf.org/rfc/rfc3490.txt">RFC 3490</a>.
 * RFC 3490 defines two operations: ToASCII and ToUnicode. These 2 operations employ
 * <a href="http://www.ietf.org/rfc/rfc3491.txt">Nameprep</a> algorithm, which is a
 * profile of <a href="http://www.ietf.org/rfc/rfc3454.txt">Stringprep</a>, and
 * <a href="http://www.ietf.org/rfc/rfc3492.txt">Punycode</a> algorithm to convert
 * domain name string back and forth.
 *
 * <p>The behavior of aforementioned conversion process can be adjusted by various flags:
 *   <ul>
 *     <li>If the ALLOW_UNASSIGNED flag is used, the domain name string to be converted
 *         can contain code points that are unassigned in Unicode 3.2, which is the
 *         Unicode version on which IDN conversion is based. If the flag is not used,
 *         the presence of such unassigned code points is treated as an error.
 *     <li>If the USE_STD3_ASCII_RULES flag is used, ASCII strings are checked against <a href="http://www.ietf.org/rfc/rfc1122.txt">RFC 1122</a> and <a href="http://www.ietf.org/rfc/rfc1123.txt">RFC 1123</a>.
 *         It is an error if they don't meet the requirements.
 *   </ul>
 * These flags can be logically OR'ed together.
 *
 * <p>The security consideration is important with respect to internationalization
 * domain name support. For example, English domain names may be <i>homographed</i>
 * - maliciously misspelled by substitution of non-Latin letters.
 * <a href="http://www.unicode.org/reports/tr36/">Unicode Technical Report #36</a>
 * discusses security issues of IDN support as well as possible solutions.
 * Applications are responsible for taking adequate security measures when using
 * international domain names.
 *
 * @author Edward Wang
 * @since 1.6
 *
 */
public final class IDN {
    Flag to allow processing of unassigned code points
/**
     * Flag to allow processing of unassigned code points
     */
    public static final int ALLOW_UNASSIGNED = 0x01;

    Flag to turn on the check against STD-3 ASCII rules
/**
     * Flag to turn on the check against STD-3 ASCII rules
     */
    public static final int USE_STD3_ASCII_RULES = 0x02;


    Translates a string from Unicode to ASCII Compatible Encoding (ACE),
as defined by the ToASCII operation of RFC 3490.
ToASCII operation can fail. ToASCII fails if any step of it fails.
If ToASCII operation fails, an IllegalArgumentException will be thrown.
In this case, the input string should not be used in an internationalized domain name.
 A label is an individual part of a domain name. The original ToASCII operation,
as defined in RFC 3490, only operates on a single label. This method can handle
both label and entire domain name, by assuming that labels in a domain name are
always separated by dots. The following characters are recognized as dots:
\u002E (full stop), \u3002 (ideographic full stop), \uFF0E (fullwidth full stop),
and \uFF61 (halfwidth ideographic full stop). if dots are
used as label separators, this method also changes all of them to \u002E (full stop)
in output translated string.
Params: input –     the string to be processed
flag –      process flag; can be 0 or any logical OR of possible flags
Throws: IllegalArgumentException –   if the input string doesn't conform to RFC 3490 specification
Returns:  the translated String/**
     * Translates a string from Unicode to ASCII Compatible Encoding (ACE),
     * as defined by the ToASCII operation of <a href="http://www.ietf.org/rfc/rfc3490.txt">RFC 3490</a>.
     *
     * <p>ToASCII operation can fail. ToASCII fails if any step of it fails.
     * If ToASCII operation fails, an IllegalArgumentException will be thrown.
     * In this case, the input string should not be used in an internationalized domain name.
     *
     * <p> A label is an individual part of a domain name. The original ToASCII operation,
     * as defined in RFC 3490, only operates on a single label. This method can handle
     * both label and entire domain name, by assuming that labels in a domain name are
     * always separated by dots. The following characters are recognized as dots:
     * &#0092;u002E (full stop), &#0092;u3002 (ideographic full stop), &#0092;uFF0E (fullwidth full stop),
     * and &#0092;uFF61 (halfwidth ideographic full stop). if dots are
     * used as label separators, this method also changes all of them to &#0092;u002E (full stop)
     * in output translated string.
     *
     * @param input     the string to be processed
     * @param flag      process flag; can be 0 or any logical OR of possible flags
     *
     * @return          the translated {@code String}
     *
     * @throws IllegalArgumentException   if the input string doesn't conform to RFC 3490 specification
     */
    public static String toASCII(String input, int flag)
    {
        int p = 0, q = 0;
        StringBuilder out = new StringBuilder();

        if (isRootLabel(input)) {
            return ".";
        }

        while (p < input.length()) {
            q = searchDots(input, p);
            out.append(toASCIIInternal(input.substring(p, q),  flag));
            if (q != (input.length())) {
               // has more labels, or keep the trailing dot as at present
               out.append('.');
            }
            p = q + 1;
        }

        return out.toString();
    }


    Translates a string from Unicode to ASCII Compatible Encoding (ACE),
as defined by the ToASCII operation of RFC 3490.
 This convenience method works as if by invoking the
two-argument counterpart as follows:
 toASCII(input, 0); 
Params: input –     the string to be processed
Throws: IllegalArgumentException –   if the input string doesn't conform to RFC 3490 specification
Returns:  the translated String/**
     * Translates a string from Unicode to ASCII Compatible Encoding (ACE),
     * as defined by the ToASCII operation of <a href="http://www.ietf.org/rfc/rfc3490.txt">RFC 3490</a>.
     *
     * <p> This convenience method works as if by invoking the
     * two-argument counterpart as follows:
     * <blockquote>
     * {@link #toASCII(String, int) toASCII}(input,&nbsp;0);
     * </blockquote>
     *
     * @param input     the string to be processed
     *
     * @return          the translated {@code String}
     *
     * @throws IllegalArgumentException   if the input string doesn't conform to RFC 3490 specification
     */
    public static String toASCII(String input) {
        return toASCII(input, 0);
    }


    Translates a string from ASCII Compatible Encoding (ACE) to Unicode,
as defined by the ToUnicode operation of RFC 3490.
ToUnicode never fails. In case of any error, the input string is returned unmodified.
 A label is an individual part of a domain name. The original ToUnicode operation,
as defined in RFC 3490, only operates on a single label. This method can handle
both label and entire domain name, by assuming that labels in a domain name are
always separated by dots. The following characters are recognized as dots:
\u002E (full stop), \u3002 (ideographic full stop), \uFF0E (fullwidth full stop),
and \uFF61 (halfwidth ideographic full stop).
Params: input –     the string to be processed
flag –      process flag; can be 0 or any logical OR of possible flags
Returns:  the translated String/**
     * Translates a string from ASCII Compatible Encoding (ACE) to Unicode,
     * as defined by the ToUnicode operation of <a href="http://www.ietf.org/rfc/rfc3490.txt">RFC 3490</a>.
     *
     * <p>ToUnicode never fails. In case of any error, the input string is returned unmodified.
     *
     * <p> A label is an individual part of a domain name. The original ToUnicode operation,
     * as defined in RFC 3490, only operates on a single label. This method can handle
     * both label and entire domain name, by assuming that labels in a domain name are
     * always separated by dots. The following characters are recognized as dots:
     * &#0092;u002E (full stop), &#0092;u3002 (ideographic full stop), &#0092;uFF0E (fullwidth full stop),
     * and &#0092;uFF61 (halfwidth ideographic full stop).
     *
     * @param input     the string to be processed
     * @param flag      process flag; can be 0 or any logical OR of possible flags
     *
     * @return          the translated {@code String}
     */
    public static String toUnicode(String input, int flag) {
        int p = 0, q = 0;
        StringBuilder out = new StringBuilder();

        if (isRootLabel(input)) {
            return ".";
        }

        while (p < input.length()) {
            q = searchDots(input, p);
            out.append(toUnicodeInternal(input.substring(p, q),  flag));
            if (q != (input.length())) {
               // has more labels, or keep the trailing dot as at present
               out.append('.');
            }
            p = q + 1;
        }

        return out.toString();
    }


    Translates a string from ASCII Compatible Encoding (ACE) to Unicode,
as defined by the ToUnicode operation of RFC 3490.
 This convenience method works as if by invoking the
two-argument counterpart as follows:
 toUnicode(input, 0); 
Params: input –     the string to be processed
Returns:  the translated String/**
     * Translates a string from ASCII Compatible Encoding (ACE) to Unicode,
     * as defined by the ToUnicode operation of <a href="http://www.ietf.org/rfc/rfc3490.txt">RFC 3490</a>.
     *
     * <p> This convenience method works as if by invoking the
     * two-argument counterpart as follows:
     * <blockquote>
     * {@link #toUnicode(String, int) toUnicode}(input,&nbsp;0);
     * </blockquote>
     *
     * @param input     the string to be processed
     *
     * @return          the translated {@code String}
     */
    public static String toUnicode(String input) {
        return toUnicode(input, 0);
    }


    /* ---------------- Private members -------------- */

    // ACE Prefix is "xn--"
    private static final String ACE_PREFIX = "xn--";
    private static final int ACE_PREFIX_LENGTH = ACE_PREFIX.length();

    private static final int MAX_LABEL_LENGTH   = 63;

    // single instance of nameprep
    private static StringPrep namePrep = null;

    static {
        InputStream stream = null;

        try {
            final String IDN_PROFILE = "/sun/net/idn/uidna.spp";
            if (System.getSecurityManager() != null) {
                stream = AccessController.doPrivileged(new PrivilegedAction<>() {
                    public InputStream run() {
                        return StringPrep.class.getResourceAsStream(IDN_PROFILE);
                    }
                });
            } else {
                stream = StringPrep.class.getResourceAsStream(IDN_PROFILE);
            }

            namePrep = new StringPrep(stream);
            stream.close();
        } catch (IOException e) {
            // should never reach here
            assert false;
        }
    }


    /* ---------------- Private operations -------------- */


    //
    // to suppress the default zero-argument constructor
    //
    private IDN() {}

    //
    // toASCII operation; should only apply to a single label
    //
    private static String toASCIIInternal(String label, int flag)
    {
        // step 1
        // Check if the string contains code points outside the ASCII range 0..0x7c.
        boolean isASCII  = isAllASCII(label);
        StringBuffer dest;

        // step 2
        // perform the nameprep operation; flag ALLOW_UNASSIGNED is used here
        if (!isASCII) {
            UCharacterIterator iter = UCharacterIterator.getInstance(label);
            try {
                dest = namePrep.prepare(iter, flag);
            } catch (java.text.ParseException e) {
                throw new IllegalArgumentException(e);
            }
        } else {
            dest = new StringBuffer(label);
        }

        // step 8, move forward to check the smallest number of the code points
        // the length must be inside 1..63
        if (dest.length() == 0) {
            throw new IllegalArgumentException(
                        "Empty label is not a legal name");
        }

        // step 3
        // Verify the absence of non-LDH ASCII code points
        //   0..0x2c, 0x2e..0x2f, 0x3a..0x40, 0x5b..0x60, 0x7b..0x7f
        // Verify the absence of leading and trailing hyphen
        boolean useSTD3ASCIIRules = ((flag & USE_STD3_ASCII_RULES) != 0);
        if (useSTD3ASCIIRules) {
            for (int i = 0; i < dest.length(); i++) {
                int c = dest.charAt(i);
                if (isNonLDHAsciiCodePoint(c)) {
                    throw new IllegalArgumentException(
                        "Contains non-LDH ASCII characters");
                }
            }

            if (dest.charAt(0) == '-' ||
                dest.charAt(dest.length() - 1) == '-') {

                throw new IllegalArgumentException(
                        "Has leading or trailing hyphen");
            }
        }

        if (!isASCII) {
            // step 4
            // If all code points are inside 0..0x7f, skip to step 8
            if (!isAllASCII(dest.toString())) {
                // step 5
                // verify the sequence does not begin with ACE prefix
                if(!startsWithACEPrefix(dest)){

                    // step 6
                    // encode the sequence with punycode
                    try {
                        dest = Punycode.encode(dest, null);
                    } catch (java.text.ParseException e) {
                        throw new IllegalArgumentException(e);
                    }

                    dest = toASCIILower(dest);

                    // step 7
                    // prepend the ACE prefix
                    dest.insert(0, ACE_PREFIX);
                } else {
                    throw new IllegalArgumentException("The input starts with the ACE Prefix");
                }

            }
        }

        // step 8
        // the length must be inside 1..63
        if (dest.length() > MAX_LABEL_LENGTH) {
            throw new IllegalArgumentException("The label in the input is too long");
        }

        return dest.toString();
    }

    //
    // toUnicode operation; should only apply to a single label
    //
    private static String toUnicodeInternal(String label, int flag) {
        boolean[] caseFlags = null;
        StringBuffer dest;

        // step 1
        // find out if all the codepoints in input are ASCII
        boolean isASCII = isAllASCII(label);

        if(!isASCII){
            // step 2
            // perform the nameprep operation; flag ALLOW_UNASSIGNED is used here
            try {
                UCharacterIterator iter = UCharacterIterator.getInstance(label);
                dest = namePrep.prepare(iter, flag);
            } catch (Exception e) {
                // toUnicode never fails; if any step fails, return the input string
                return label;
            }
        } else {
            dest = new StringBuffer(label);
        }

        // step 3
        // verify ACE Prefix
        if(startsWithACEPrefix(dest)) {

            // step 4
            // Remove the ACE Prefix
            String temp = dest.substring(ACE_PREFIX_LENGTH, dest.length());

            try {
                // step 5
                // Decode using punycode
                StringBuffer decodeOut = Punycode.decode(new StringBuffer(temp), null);

                // step 6
                // Apply toASCII
                String toASCIIOut = toASCII(decodeOut.toString(), flag);

                // step 7
                // verify
                if (toASCIIOut.equalsIgnoreCase(dest.toString())) {
                    // step 8
                    // return output of step 5
                    return decodeOut.toString();
                }
            } catch (Exception ignored) {
                // no-op
            }
        }

        // just return the input
        return label;
    }


    //
    // LDH stands for "letter/digit/hyphen", with characters restricted to the
    // 26-letter Latin alphabet <A-Z a-z>, the digits <0-9>, and the hyphen
    // <->.
    // Non LDH refers to characters in the ASCII range, but which are not
    // letters, digits or the hyphen.
    //
    // non-LDH = 0..0x2C, 0x2E..0x2F, 0x3A..0x40, 0x5B..0x60, 0x7B..0x7F
    //
    private static boolean isNonLDHAsciiCodePoint(int ch){
        return (0x0000 <= ch && ch <= 0x002C) ||
               (0x002E <= ch && ch <= 0x002F) ||
               (0x003A <= ch && ch <= 0x0040) ||
               (0x005B <= ch && ch <= 0x0060) ||
               (0x007B <= ch && ch <= 0x007F);
    }

    //
    // search dots in a string and return the index of that character;
    // or if there is no dots, return the length of input string
    // dots might be: \u002E (full stop), \u3002 (ideographic full stop), \uFF0E (fullwidth full stop),
    // and \uFF61 (halfwidth ideographic full stop).
    //
    private static int searchDots(String s, int start) {
        int i;
        for (i = start; i < s.length(); i++) {
            if (isLabelSeparator(s.charAt(i))) {
                break;
            }
        }

        return i;
    }

    //
    // to check if a string is a root label, ".".
    //
    private static boolean isRootLabel(String s) {
        return (s.length() == 1 && isLabelSeparator(s.charAt(0)));
    }

    //
    // to check if a character is a label separator, i.e. a dot character.
    //
    private static boolean isLabelSeparator(char c) {
        return (c == '.' || c == '\u3002' || c == '\uFF0E' || c == '\uFF61');
    }

    //
    // to check if a string only contains US-ASCII code point
    //
    private static boolean isAllASCII(String input) {
        boolean isASCII = true;
        for (int i = 0; i < input.length(); i++) {
            int c = input.charAt(i);
            if (c > 0x7F) {
                isASCII = false;
                break;
            }
        }
        return isASCII;
    }

    //
    // to check if a string starts with ACE-prefix
    //
    private static boolean startsWithACEPrefix(StringBuffer input){
        boolean startsWithPrefix = true;

        if(input.length() < ACE_PREFIX_LENGTH){
            return false;
        }
        for(int i = 0; i < ACE_PREFIX_LENGTH; i++){
            if(toASCIILower(input.charAt(i)) != ACE_PREFIX.charAt(i)){
                startsWithPrefix = false;
            }
        }
        return startsWithPrefix;
    }

    private static char toASCIILower(char ch){
        if('A' <= ch && ch <= 'Z'){
            return (char)(ch + 'a' - 'A');
        }
        return ch;
    }

    private static StringBuffer toASCIILower(StringBuffer input){
        StringBuffer dest = new StringBuffer();
        for(int i = 0; i < input.length();i++){
            dest.append(toASCIILower(input.charAt(i)));
        }
        return dest;
    }
}
Params:	input – the string to be processed flag – process flag; can be 0 or any logical OR of possible flags
Throws:	IllegalArgumentException – if the input string doesn't conform to RFC 3490 specification
Returns:	the translated `String`
Params:	input – the string to be processed
Throws:	IllegalArgumentException – if the input string doesn't conform to RFC 3490 specification
Returns:	the translated `String`
/

java/ 15/ java.base/java/net/IDN.java
