/*

 * 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.

 */

/*

 *

 *  (C) Copyright IBM Corp. 1999 All Rights Reserved.

 *  Copyright 1997 The Open Group Research Institute.  All rights reserved.

 */

package sun.security.krb5;

import sun.security.krb5.internal.Krb5;

import sun.security.util.*;

import java.io.IOException;

import java.util.*;

import sun.security.krb5.internal.util.KerberosString;

/**

 * Implements the ASN.1 Realm type.

 *

 * {@code Realm ::= GeneralString}

 *

 * This class is immutable.

 */

public class Realm implements Cloneable {

    private final String realm; // not null nor empty

    public Realm(String name) throws RealmException {

        realm = parseRealm(name);

    }

    public static Realm getDefault() throws RealmException {

        try {

            return new Realm(Config.getInstance().getDefaultRealm());

        } catch (RealmException re) {

            throw re;

        } catch (KrbException ke) {

            throw new RealmException(ke);

        }

    }

    // Immutable class, no need to clone

    public Object clone() {

        return this;

    }

    public boolean equals(Object obj) {

        if (this == obj) {

            return true;

        }

        if (!(obj instanceof Realm)) {

            return false;

        }

        Realm that = (Realm)obj;

        return this.realm.equals(that.realm);

    }

    public int hashCode() {

        return realm.hashCode();

    }

    /**

     * Constructs a Realm object.

     * @param encoding a Der-encoded data.

     * @exception Asn1Exception if an error occurs while decoding an ASN1 encoded data.

     * @exception IOException if an I/O error occurs while reading encoded data.

     * @exception RealmException if an error occurs while parsing a Realm object.

     */

    public Realm(DerValue encoding)

        throws Asn1Exception, RealmException, IOException {

        if (encoding == null) {

            throw new IllegalArgumentException("encoding can not be null");

        }

        realm = new KerberosString(encoding).toString();

        if (realm == null || realm.length() == 0)

            throw new RealmException(Krb5.REALM_NULL);

        if (!isValidRealmString(realm))

            throw new RealmException(Krb5.REALM_ILLCHAR);

    }

    public String toString() {

        return realm;

    }

    // Extract realm from a string like dummy@REALM

    public static String parseRealmAtSeparator(String name)

        throws RealmException {

        if (name == null) {

            throw new IllegalArgumentException

                ("null input name is not allowed");

        }

        String temp = new String(name);

        String result = null;

        int i = 0;

        while (i < temp.length()) {

            if (temp.charAt(i) == PrincipalName.NAME_REALM_SEPARATOR) {

                if (i == 0 || temp.charAt(i - 1) != '\\') {

                    if (i + 1 < temp.length()) {

                        result = temp.substring(i + 1, temp.length());

                    } else {

                        throw new IllegalArgumentException

                                ("empty realm part not allowed");

                    }

                    break;

                }

            }

            i++;

        }

        if (result != null) {

            if (result.length() == 0)

                throw new RealmException(Krb5.REALM_NULL);

            if (!isValidRealmString(result))

                throw new RealmException(Krb5.REALM_ILLCHAR);

        }

        return result;

    }

    public static String parseRealmComponent(String name) {

        if (name == null) {

            throw new IllegalArgumentException

                ("null input name is not allowed");

        }

        String temp = new String(name);

        String result = null;

        int i = 0;

        while (i < temp.length()) {

            if (temp.charAt(i) == PrincipalName.REALM_COMPONENT_SEPARATOR) {

                if (i == 0 || temp.charAt(i - 1) != '\\') {

                    if (i + 1 < temp.length())

                        result = temp.substring(i + 1, temp.length());

                    break;

                }

            }

            i++;

        }

        return result;

    }

    protected static String parseRealm(String name) throws RealmException {

        String result = parseRealmAtSeparator(name);

        if (result == null)

            result = name;

        if (result == null || result.length() == 0)

            throw new RealmException(Krb5.REALM_NULL);

        if (!isValidRealmString(result))

            throw new RealmException(Krb5.REALM_ILLCHAR);

        return result;

    }

    // This is protected because the definition of a realm

    // string is fixed

    protected static boolean isValidRealmString(String name) {

        if (name == null)

            return false;

        if (name.length() == 0)

            return false;

        for (int i = 0; i < name.length(); i++) {

            if (name.charAt(i) == '/' ||

                name.charAt(i) == ':' ||

                name.charAt(i) == '\0') {

                return false;

            }

        }

        return true;

    }

    /**

     * Encodes a Realm object.

     * @return the byte array of encoded KrbCredInfo object.

     * @exception Asn1Exception if an error occurs while decoding an ASN1 encoded data.

     * @exception IOException if an I/O error occurs while reading encoded data.

     *

     */

    public byte[] asn1Encode() throws Asn1Exception, IOException {

        DerOutputStream out = new DerOutputStream();

        out.putDerValue(new KerberosString(this.realm).toDerValue());

        return out.toByteArray();

    }

    /**

     * Parse (unmarshal) a realm from a DER input stream.  This form

     * parsing might be used when expanding a value which is part of

     * a constructed sequence and uses explicitly tagged type.

     *

     * @exception Asn1Exception on error.

     * @param data the Der input stream value, which contains one or more marshaled value.

     * @param explicitTag tag number.

     * @param optional indicate if this data field is optional

     * @return an instance of Realm.

     *

     */

    public static Realm parse(DerInputStream data, byte explicitTag, boolean optional)

            throws Asn1Exception, IOException, RealmException {

        if ((optional) && (((byte)data.peekByte() & (byte)0x1F) != explicitTag)) {

            return null;

        }

        DerValue der = data.getDerValue();

        if (explicitTag != (der.getTag() & (byte)0x1F))  {

            throw new Asn1Exception(Krb5.ASN1_BAD_ID);

        } else {

            DerValue subDer = der.getData().getDerValue();

            return new Realm(subDer);

        }

    }

    /**

     * Returns an array of realms that may be traversed to obtain

     * a TGT from the initiating realm cRealm to the target realm

     * sRealm.

     * <br>

     * This method would read [capaths] to create a path, or generate a

     * hierarchical path if [capaths] does not contain a sub-stanza for cRealm

     * or the sub-stanza does not contain a tag for sRealm.

     * <br>

     * The returned list would never be null, and it always contains

     * cRealm as the head entry. sRealm is not included as the tail.

     *

     * @param cRealm the initiating realm, not null

     * @param sRealm the target realm, not null, not equals to cRealm

     * @return array of realms including at least cRealm as the first

     *         element

     */

    public static String[] getRealmsList(String cRealm, String sRealm) {

        try {

            // Try [capaths]

            return parseCapaths(cRealm, sRealm);

        } catch (KrbException ke) {

            // Now assume the realms are organized hierarchically.

            return parseHierarchy(cRealm, sRealm);

        }

    }

    /**

     * Parses the [capaths] stanza of the configuration file for a

     * list of realms to traverse to obtain credentials from the

     * initiating realm cRealm to the target realm sRealm.

     *

     * For a given client realm C there is a tag C in [capaths] whose

     * subtag S has a value which is a (possibly partial) path from C

     * to S. When the path is partial, it contains only the tail of the

     * full path. Values of other subtags will be used to build the full

     * path. The value "." means a direct path from C to S. If realm S

     * does not appear as a subtag, there is no path defined here.

     *

     * The implementation ignores all values which equals to C or S, or

     * a "." in multiple values, or any duplicated realm names.

     *

     * When a path value has more than two realms, they can be specified

     * with multiple key-value pairs each having a single value, but the

     * order must not change.

     *

     * For example:

     *

     * [capaths]

     *    TIVOLI.COM = {

     *        IBM.COM = IBM_LDAPCENTRAL.COM MOONLITE.ORG

     *        IBM_LDAPCENTRAL.COM = LDAPCENTRAL.NET

     *        LDAPCENTRAL.NET = .

     *    }

     *

     * TIVOLI.COM has a direct path to LDAPCENTRAL.NET, which has a direct

     * path to IBM_LDAPCENTRAL.COM. It also has a partial path to IBM.COM

     * being "IBM_LDAPCENTRAL.COM MOONLITE.ORG". Merging these info together,

     * a full path from TIVOLI.COM to IBM.COM will be

     *

     *   TIVOLI.COM -> LDAPCENTRAL.NET -> IBM_LDAPCENTRAL.COM

     *              -> IBM_LDAPCENTRAL.COM -> MOONLITE.ORG

     *

     * Please note the sRealm IBM.COM does not appear in the path.

     *

     * @param cRealm the initiating realm

     * @param sRealm the target realm, not the same as cRealm

     * @return array of realms including at least cRealm as the first

     *          element

     * @throws KrbException if the config does not contain a sub-stanza

     *          for cRealm in [capaths] or the sub-stanza does not contain

     *          sRealm as a tag

     */

    private static String[] parseCapaths(String cRealm, String sRealm)

            throws KrbException {

        // This line could throw a KrbException

        Config cfg = Config.getInstance();

        if (!cfg.exists("capaths", cRealm, sRealm)) {

            throw new KrbException("No conf");

        }

        LinkedList<String> path = new LinkedList<>();

        String head = sRealm;

        while (true) {

            String value = cfg.getAll("capaths", cRealm, head);

            if (value == null) {

                break;

            }

            String[] more = value.split("\\s+");

            boolean changed = false;

            for (int i=more.length-1; i>=0; i--) {

                if (path.contains(more[i])

                        || more[i].equals(".")

                        || more[i].equals(cRealm)

                        || more[i].equals(sRealm)

                        || more[i].equals(head)) {

                    // Ignore invalid values

                    continue;

                }

                changed = true;

                path.addFirst(more[i]);

            }

            if (!changed) break;

            head = path.getFirst();

        }

        path.addFirst(cRealm);

        return path.toArray(new String[path.size()]);

   }

    /**

     * Build a list of realm that can be traversed

     * to obtain credentials from the initiating realm cRealm

     * for a service in the target realm sRealm.

     * @param cRealm the initiating realm

     * @param sRealm the target realm, not the same as cRealm

     * @return array of realms including cRealm as the first element

     */

    private static String[] parseHierarchy(String cRealm, String sRealm) {

        String[] cComponents = cRealm.split("\\.");

        String[] sComponents = sRealm.split("\\.");

        int cPos = cComponents.length;

        int sPos = sComponents.length;

        boolean hasCommon = false;

        for (sPos--, cPos--; sPos >=0 && cPos >= 0 &&

                sComponents[sPos].equals(cComponents[cPos]);

                sPos--, cPos--) {

            hasCommon = true;

        }

        // For those with common components:

        //                            length  pos

        // SITES1.SALES.EXAMPLE.COM   4       1

        //   EVERYWHERE.EXAMPLE.COM   3       0

        // For those without common components:

        //                     length  pos

        // DEVEL.EXAMPLE.COM   3       2

        // PROD.EXAMPLE.ORG    3       2

        LinkedList<String> path = new LinkedList<>();

        // Un-common ones for client side

        for (int i=0; i<=cPos; i++) {

            path.addLast(subStringFrom(cComponents, i));

        }

        // Common one

        if (hasCommon) {

            path.addLast(subStringFrom(cComponents, cPos+1));

        }

        // Un-common ones for server side

        for (int i=sPos; i>=0; i--) {

            path.addLast(subStringFrom(sComponents, i));

        }

        // Remove sRealm from path. Note that it might be added at last loop

        // or as a common component, if sRealm is a parent of cRealm

        path.removeLast();

        return path.toArray(new String[path.size()]);

    }

    /**

     * Creates a realm name using components from the given position.

     * For example, subStringFrom({"A", "B", "C"}, 1) is "B.C".

     */

    private static String subStringFrom(String[] components, int from) {

        StringBuilder sb = new StringBuilder();

        for (int i=from; i<components.length; i++) {

            if (sb.length() != 0) sb.append('.');

            sb.append(components[i]);

        }

        return sb.toString();

    }

}