src/jdk.httpserver/share/classes/sun/net/httpserver/Utils.java

/*
 * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package sun.net.httpserver;

/**
 * Provides utility methods for checking header field names and quoted strings.
 */
public class Utils {

    // ABNF primitives defined in RFC 7230
    private static final boolean[] TCHAR = new boolean[256];
    private static final boolean[] QDTEXT = new boolean[256];
    private static final boolean[] QUOTED_PAIR = new boolean[256];

    static {
        char[] allowedTokenChars =
                ("!#$%&'*+-.^_`|~0123456789" +
                        "abcdefghijklmnopqrstuvwxyz" +
                        "ABCDEFGHIJKLMNOPQRSTUVWXYZ").toCharArray();
        for (char c : allowedTokenChars) {
            TCHAR[c] = true;
        }
        for (char c = 0x20; c <= 0xFF; c++) {
            QDTEXT[c] = true;
        }
        QDTEXT[0x22] = false;  // (")   illegal
        QDTEXT[0x5c] = false;  // (\)   illegal
        QDTEXT[0x7F] = false;  // (DEL) illegal

        for (char c = 0x20; c <= 0xFF; c++) {
            QUOTED_PAIR[c] = true;
        }
        QUOTED_PAIR[0x09] = true;  // (\t)    legal
        QUOTED_PAIR[0x7F] = false; // (DEL) illegal
    }

    /*
     * Validates an RFC 7230 field-name.
     */
    public static boolean isValidName(String token) {
        for (int i = 0; i < token.length(); i++) {
            char c = token.charAt(i);
            if (c > 255 || !TCHAR[c]) {
                return false;
            }
        }
        return !token.isEmpty();
    }

    /*
     * Validates an RFC 7230 quoted-string.
     */
    public static boolean isQuotedStringContent(String token) {
        for (int i = 0; i < token.length(); i++) {
            char c = token.charAt(i);
            if (c > 255) {
                return false;
            } else if (c == 0x5c) {  // check if valid quoted-pair
                if (i == token.length() - 1 || !QUOTED_PAIR[token.charAt(i++)]) {
                    return false;
                }
            } else if (!QDTEXT[c]) {
                return false; // illegal char
            }
        }
        return true;
    }

    /* Throw IAE if illegal character found.  isValue is true if String is
     * a value. Otherwise it is header name
     */
    public static void checkHeader(String str, boolean isValue) {
        int len = str.length();
        for (int i=0; i<len; i++) {
            char c = str.charAt(i);
            if (c == '\r') {
                if (!isValue) {
                    throw new IllegalArgumentException("Illegal CR found in header");
                }
                // is allowed if it is followed by \n and a whitespace char
                if (i >= len - 2) {
                    throw new IllegalArgumentException("Illegal CR found in header");
                }
                char c1 = str.charAt(i+1);
                char c2 = str.charAt(i+2);
                if (c1 != '\n') {
                    throw new IllegalArgumentException("Illegal char found after CR in header");
                }
                if (c2 != ' ' && c2 != '\t') {
                    throw new IllegalArgumentException("No whitespace found after CRLF in header");
                }
                i+=2;
            } else if (c == '\n') {
                throw new IllegalArgumentException("Illegal LF found in header");
            } else if (c > 255) {
                throw new IllegalArgumentException("Illegal character found in header");
            }
        }
    }

}