HarmonyOS鸿蒙Next中国密SM2算法如何得到ASN.1解码后裸密文数据

SM2_Ciphertext

i2d_SM2_Ciphertext

import { SM2_SEQUENCE } from '../crypto/SM2/sm2Sequence';
import { ASN1Util } from './asn1Util';
import hilog from '@ohos.hilog';

export class SM2_Ciphertext {

  /**
   用于将SM2裸密文数据序列化
   @param primal_data SM2裸密钥数据，长度为96+明文长度（字节），输入格式为C1C3C2的Hex字符串
   @returns 返回序列化后的标准密文数据，输出格式为Hex字符串
   */
  i2d_SM2_Ciphertext(primal_data: string): string {
    let standard_data: string = "";
    return standard_data;
  }

  /**
  用于将标准SM2密文数据解码
  @param standard_data 标准SM2密文数据，符合ASN.1编码标准，输入格式为Hex字符串
  @returns 返回ASN.1解码后的SM2密文数据
  */
  d2i_SM2_Ciphertext(standard_data: string): string {
    let message: string = standard_data;

    if (!message.startsWith(ASN1Util.SEQUENCE)) {
      this.ciphertextErr();
    }
    message = message.slice(ASN1Util.SEQUENCE.length, message.length);

    let sequence_lenHex: string = this.getLenHex(message);
    message = message.slice(sequence_lenHex.length, message.length);

    let sequence_len: number = this.lenHex2number(sequence_lenHex);
    if (sequence_len != message.length / 2) {
      this.ciphertextErr();
    }

    let sm2_sequence = new SM2_SEQUENCE();
    message = this.readC1(sm2_sequence, message);
    message = this.readC3(sm2_sequence, message);
    message = this.readC2(sm2_sequence, message);

    console.log(sm2_sequence.toString());
    let primal_data: string = sm2_sequence.C1x + sm2_sequence.C1y + sm2_sequence.C3 + sm2_sequence.C2;

    return primal_data;
  }

  // 提取表示长度的字符串
  getLenHex(data: string): string {
    let byte: number = Number.parseInt("0x" + data.slice(0, 2));
    let len_size: number = byte > 127 ? byte - 0x80 + 1 : 1;
    return data.slice(0, len_size * 2);
  }

  // 将表示长度的Hex字符串转为整型
  lenHex2number(lenHex: string): number {
    if (lenHex.length == 2) {
      return Number.parseInt("0x" + lenHex);
    }
    return Number.parseInt("0x" + lenHex.slice(2, lenHex.length));
  }

  ciphertextErr() {
    hilog.error(0, "d2i_SM2_Ciphertext", "密文格式错误");
    throw new Error("SM2 ciphertext error!")
  }

  readC1(sm2_sequence: SM2_SEQUENCE, data: string): string {
    let xy: string[] = [];
    for (let i = 0; i < 2; i++) {
      if (data.startsWith("0220")) {
        xy[i] = data.slice(4, 68);
        data = data.slice(68, data.length);
      } else if (data.startsWith("022100")) {
        xy[i] = data.slice(6, 70);
        data = data.slice(70, data.length);
      } else {
        this.ciphertextErr();
      }
    }
    sm2_sequence.C1x = xy[0];
    sm2_sequence.C1y = xy[1];
    return data;
  }

  readC2(sm2_sequence: SM2_SEQUENCE, data: string): string {
    if (data.startsWith(ASN1Util.OCTET_STRING)) {
      data = data.slice(ASN1Util.OCTET_STRING.length, data.length);
      let C2_lenHex = this.getLenHex(data);
      data = data.slice(C2_lenHex.length, data.length)
      if (this.lenHex2number(C2_lenHex) != data.length / 2) {
        this.ciphertextErr()
      }
      sm2_sequence.C2 = data;
    } else {
      this.ciphertextErr();
    }
    return data;
  }

  readC3(sm2_sequence: SM2_SEQUENCE, data: string): string {
    if (data.startsWith("0420")) {
      sm2_sequence.C3 = data.slice(4, 68);
      data = data.slice(68, data.length);
    } else {
      this.ciphertextErr();
    }
    return data;
  }
}

ASN1Util

export class ASN1Util {

  static BOOLEAN: string = "01";
  static INTEGER: string = "02";
  static BIT_STRING: string = "03";
  static OCTET_STRING: string = "04";
  static NULL: string = "05";
  static REAL: string = "09";
  static ENUMERATED: string = "0a";
  static SEQUENCE: string = "30";
  static SET: string = "31";

}

SM2_SEQUENCE

import { formToJSON } from '@ohos/axios';

export class SM2_SEQUENCE {

  private _C1x: string = "";
  private _C1y: string = "";
  private _C2: string = "";
  private _C3: string = "";

  public set C1x(value: string) {
    this._C1x = value;
  }

  public get C1x(): string {
    return this._C1x;
  }

  public set C1y(value: string) {
    this._C1y = value;
  }

  public get C1y(): string {
    return this._C1y;
  }

  public set C2(value: string) {
    this._C2 = value;
  }

  public get C2(): string {
    return this._C2;
  }

  public set C3(value: string) {
    this._C3 = value;
  }

  public get C3(): string {
    return this._C3;
  }

  public toString(): string {
    return JSON.stringify(this);
  }

}