001/*
002 * oauth2-oidc-sdk
003 *
004 * Copyright 2012-2016, Connect2id Ltd and contributors.
005 *
006 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use
007 * this file except in compliance with the License. You may obtain a copy of the
008 * License at
009 *
010 *    http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software distributed
013 * under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
014 * CONDITIONS OF ANY KIND, either express or implied. See the License for the
015 * specific language governing permissions and limitations under the License.
016 */
017
018package com.nimbusds.oauth2.sdk.pkce;
019
020
021import com.nimbusds.oauth2.sdk.auth.Secret;
022
023
024/**
025 * Authorisation code verifier.
026 *
027 * <p>Related specifications:
028 *
029 * <ul>
030 *     <li>Proof Key for Code Exchange by OAuth Public Clients (RFC 7636).
031 * </ul>
032 */
033public class CodeVerifier extends Secret {
034        
035        
036        private static final long serialVersionUID = 1L;
037        
038        
039        /**
040         * The minimum character length of a code verifier.
041         */
042        public static final int MIN_LENGTH = 43;
043        
044        
045        /**
046         * The maximum character length of a code verifier.
047         */
048        public static final int MAX_LENGTH = 128;
049        
050        
051        /**
052         * Creates a new code verifier with the specified value.
053         *
054         * @param value The code verifier value. Must not contain characters
055         *              other than [A-Z] / [a-z] / [0-9] / "-" / "." / "_" /
056         *              "~". The verifier length must be at least 43
057         *              characters but not more than 128 characters. Must not
058         *              be {@code null} or empty string.
059         */
060        public CodeVerifier(final String value) {
061                super(value);
062
063                if (value.length() < MIN_LENGTH) {
064                        throw new IllegalArgumentException("The code verifier must be at least " + MIN_LENGTH + " characters");
065                }
066
067                if (value.length() > MAX_LENGTH) {
068                        throw new IllegalArgumentException("The code verifier must not be longer than " + MAX_LENGTH + " characters");
069                }
070
071                if (! isLegal(value)) {
072                        throw new IllegalArgumentException("Illegal char(s) in code verifier, see RFC 7636, section 4.1");
073                }
074        }
075
076
077        /**
078         * Generates a new code verifier represented by a secure random 256-bit
079         * number that is Base64URL-encoded (as a 43 character string, which is
080         * the {@link #MIN_LENGTH minimum character length} of a code
081         * verifier).
082         */
083        public CodeVerifier() {
084                super(32);
085        }
086
087
088        @Override
089        public boolean equals(final Object object) {
090                return object instanceof CodeVerifier && super.equals(object);
091        }
092        
093        
094        /**
095         * Returns {@code true} if the specified string is legal for a code
096         * verifier.
097         *
098         * @param s The string, {@code null} if not specified.
099         *
100         * @return {@code true} if legal or {@code null}, {@code false} if
101         *         illegal.
102         */
103        static boolean isLegal(final String s) {
104
105                if (s == null) {
106                        return true;
107                }
108
109                for (char c : s.toCharArray()) {
110                        if (!isLegal(c)) {
111                                return false;
112                        }
113                }
114
115                return true;
116        }
117        
118        /**
119         * Returns {@code true} if the specified character is legal for a code
120         * verifier.
121         *
122         * @param c The character.
123         *
124         * @return {@code true} if legal, {@code false} if illegal.
125         */
126        static boolean isLegal(final char c) {
127
128                // https://tools.ietf.org/html/rfc7636#page-8
129                //
130                // ABNF for "code_verifier" is as follows.
131                //
132                // code-verifier = 43*128unreserved
133                // unreserved = ALPHA / DIGIT / "-" / "." / "_" / "~"
134                // ALPHA = %x41-5A / %x61-7A
135                // DIGIT = %x30-39
136
137                if (c > 0x7f) {
138                        // Not ASCII
139                        return false;
140                }
141
142                return c >= 0x41 && c <= 0x5a || c >= 0x61 && c <= 0x7a || c >= 0x30 && c <= 0x39 || c == '-' || c == '.' || c == '_' || c == '~';
143        }
144}