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/*
 * Copyright 2017, OnGres.
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted provided that the
 * following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following
 * disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the
 * following disclaimer in the documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */


package com.impossibl.postgres.protocol.sasl.scram;


import com.impossibl.postgres.protocol.sasl.scram.exception.ScramParseException;
import com.impossibl.postgres.protocol.sasl.scram.util.CharAttribute;

import java.util.HashMap;
import java.util.Map;


/**
 * SCRAM Attributes as defined in Section 5.1 of the RFC.
 *
 * Not all the available attributes may be available in this implementation.
 */
public enum ScramAttributes implements CharAttribute {
  /**
   * This attribute specifies the name of the user whose password is used for authentication
   * (a.k.a. "authentication identity" [RFC4422]).
   * If the "a" attribute is not specified (which would normally be the case), this username is also the identity
   * that will be associated with the connection subsequent to authentication and authorization.
   *
   * The client SHOULD prepare the username using the "SASLprep" profile
   * [RFC4013] of the "stringprep" algorithm
   * [RFC3454] treating it as a query string
   * (i.e., unassigned Unicode code points are allowed).
   *
   * The characters ',' or '=' in usernames are sent as '=2C' and '=3D' respectively.
   */
  USERNAME('n'),

  /**
   * This is an optional attribute, and is part of the GS2 [RFC5801]
   * bridge between the GSS-API and SASL. This attribute specifies an authorization identity.
   * A client may include it in its first message to the server if it wants to authenticate as one user,
   * but subsequently act as a different user. This is typically used by an administrator to perform some management
   * task on behalf of another user, or by a proxy in some situations.
   *
   * If this attribute is omitted (as it normally would be), the authorization identity is assumed to be derived
   * from the username specified with the (required) "n" attribute.
   *
   * The server always authenticates the user specified by the "n" attribute.
   * If the "a" attribute specifies a different user, the server associates that identity with the connection after
   * successful authentication and authorization checks.
   *
   * The syntax of this field is the same as that of the "n" field with respect to quoting of '=' and ','.
   */
  AUTHZID('a'),

  /**
   * This attribute specifies a sequence of random printable ASCII characters excluding ','
   * (which forms the nonce used as input to the hash function). No quoting is applied to this string.
   */
  NONCE('r'),

  /**
   * This REQUIRED attribute specifies the base64-encoded GS2 header and channel binding data.
   * The attribute data consist of:
   * 
   *      
   *          the GS2 header from the client's first message
   *          (recall that the GS2 header contains a channel binding flag and an optional authzid).
   *          This header is going to include channel binding type prefix
   *          (see [RFC5056]),
   *          if and only if the client is using channel binding;
   *      
   *      
   *          followed by the external channel's channel binding data,
   *          if and only if the client is using channel binding.
   *      
   * 
   */
  CHANNEL_BINDING('c'),

  /**
   * This attribute specifies the base64-encoded salt used by the server for this user.
   */
  SALT('s'),

  /**
   * This attribute specifies an iteration count for the selected hash function and user.
   */
  ITERATION('i'),

  /**
   * This attribute specifies a base64-encoded ClientProof.
   */
  CLIENT_PROOF('p'),

  /**
   * This attribute specifies a base64-encoded ServerSignature.
   */
  SERVER_SIGNATURE('v'),

  /**
   * This attribute specifies an error that occurred during authentication exchange.
   * Can help diagnose the reason for the authentication exchange failure.
   */
  ERROR('e');

  private final char attributeChar;

  ScramAttributes(char attributeChar) {
    this.attributeChar = attributeChar;
  }

  @Override
  public char getChar() {
    return attributeChar;
  }

  private static final Map REVERSE_MAPPING = new HashMap<>();

  static {
    for (ScramAttributes scramAttribute : values()) {
      REVERSE_MAPPING.put(scramAttribute.getChar(), scramAttribute);
    }
  }

  /**
   * Find a SCRAMAttribute by its character.
   * @param c The character.
   * @return The SCRAMAttribute that has that character.
   * @throws ScramParseException If no SCRAMAttribute has this character.
   */
  public static ScramAttributes byChar(char c) throws ScramParseException {
    if (!REVERSE_MAPPING.containsKey(c)) {
      throw new ScramParseException("Attribute with char '" + c + "' does not exist");
    }

    return REVERSE_MAPPING.get(c);
  }
}