# All files / src/crypt aes-decryptor.js

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     // PKCS7
    export function removePadding (buffer) {
      const outputBytes = buffer.byteLength;
      const paddingBytes = outputBytes && (new DataView(buffer)).getUint8(outputBytes - 1);
      if (paddingBytes) {
        return buffer.slice(0, outputBytes - paddingBytes);
      } else {
        return buffer;
      }
    }

    class AESDecryptor {
      constructor () {
        // Static after running initTable
        this.rcon = [0x0, 0x1, 0x2, 0x4, 0x8, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36];
        this.subMix = [new Uint32Array(256), new Uint32Array(256), new Uint32Array(256), new Uint32Array(256)];
        this.invSubMix = [new Uint32Array(256), new Uint32Array(256), new Uint32Array(256), new Uint32Array(256)];
        this.sBox = new Uint32Array(256);
        this.invSBox = new Uint32Array(256);

        // Changes during runtime
        this.key = new Uint32Array(0);

        this.initTable();
      }

      // Using view.getUint32() also swaps the byte order.
      uint8ArrayToUint32Array_ (arrayBuffer) {
        let view = new DataView(arrayBuffer);
        let newArray = new Uint32Array(4);
        for (let i = 0; i < 4; i++) {
          newArray[i] = view.getUint32(i * 4);
        }

        return newArray;
      }

      initTable () {
        let sBox = this.sBox;
        let invSBox = this.invSBox;
        let subMix = this.subMix;
        let subMix0 = subMix[0];
        let subMix1 = subMix[1];
        let subMix2 = subMix[2];
        let subMix3 = subMix[3];
        let invSubMix = this.invSubMix;
        let invSubMix0 = invSubMix[0];
        let invSubMix1 = invSubMix[1];
        let invSubMix2 = invSubMix[2];
        let invSubMix3 = invSubMix[3];

        let d = new Uint32Array(256);
        let x = 0;
        let xi = 0;
        let i = 0;
        for (i = 0; i < 256; i++) {
          if (i < 128) {
            d[i] = i << 1;
          } else {
            d[i] = (i << 1) ^ 0x11b;
          }
        }

        for (i = 0; i < 256; i++) {
          let sx = xi ^ (xi << 1) ^ (xi << 2) ^ (xi << 3) ^ (xi << 4);
          sx = (sx >>> 8) ^ (sx & 0xff) ^ 0x63;
          sBox[x] = sx;
          invSBox[sx] = x;

          // Compute multiplication
          let x2 = d[x];
          let x4 = d[x2];
          let x8 = d[x4];

          // Compute sub/invSub bytes, mix columns tables
          let t = (d[sx] * 0x101) ^ (sx * 0x1010100);
          subMix0[x] = (t << 24) | (t >>> 8);
          subMix1[x] = (t << 16) | (t >>> 16);
          subMix2[x] = (t << 8) | (t >>> 24);
          subMix3[x] = t;

          // Compute inv sub bytes, inv mix columns tables
          t = (x8 * 0x1010101) ^ (x4 * 0x10001) ^ (x2 * 0x101) ^ (x * 0x1010100);
          invSubMix0[sx] = (t << 24) | (t >>> 8);
          invSubMix1[sx] = (t << 16) | (t >>> 16);
          invSubMix2[sx] = (t << 8) | (t >>> 24);
          invSubMix3[sx] = t;

          // Compute next counter
          if (!x) {
            x = xi = 1;
          } else {
            x = x2 ^ d[d[d[x8 ^ x2]]];
            xi ^= d[d[xi]];
          }
        }
      }

      expandKey (keyBuffer) {
        // convert keyBuffer to Uint32Array
        let key = this.uint8ArrayToUint32Array_(keyBuffer);
        let sameKey = true;
        let offset = 0;

        while (offset < key.length && sameKey) {
          sameKey = (key[offset] === this.key[offset]);
          offset++;
        }

        if (sameKey) {
          return;
        }

        this.key = key;
        let keySize = this.keySize = key.length;

        if (keySize !== 4 && keySize !== 6 && keySize !== 8) {
          throw new Error('Invalid aes key size=' + keySize);
        }

        let ksRows = this.ksRows = (keySize + 6 + 1) * 4;
        let ksRow;
        let invKsRow;

        let keySchedule = this.keySchedule = new Uint32Array(ksRows);
        let invKeySchedule = this.invKeySchedule = new Uint32Array(ksRows);
        let sbox = this.sBox;
        let rcon = this.rcon;

        let invSubMix = this.invSubMix;
        let invSubMix0 = invSubMix[0];
        let invSubMix1 = invSubMix[1];
        let invSubMix2 = invSubMix[2];
        let invSubMix3 = invSubMix[3];

        let prev;
        let t;

        for (ksRow = 0; ksRow < ksRows; ksRow++) {
          if (ksRow < keySize) {
            prev = keySchedule[ksRow] = key[ksRow];
            continue;
          }
          t = prev;

          if (ksRow % keySize === 0) {
            // Rot word
            t = (t << 8) | (t >>> 24);

            // Sub word
            t = (sbox[t >>> 24] << 24) | (sbox[(t >>> 16) & 0xff] << 16) | (sbox[(t >>> 8) & 0xff] << 8) | sbox[t & 0xff];

            // Mix Rcon
            t ^= rcon[(ksRow / keySize) | 0] << 24;
          } else if (keySize > 6 && ksRow % keySize === 4) {
            // Sub word
            t = (sbox[t >>> 24] << 24) | (sbox[(t >>> 16) & 0xff] << 16) | (sbox[(t >>> 8) & 0xff] << 8) | sbox[t & 0xff];
          }

          keySchedule[ksRow] = prev = (keySchedule[ksRow - keySize] ^ t) >>> 0;
        }

        for (invKsRow = 0; invKsRow < ksRows; invKsRow++) {
          ksRow = ksRows - invKsRow;
          if (invKsRow & 3) {
            t = keySchedule[ksRow];
          } else {
            t = keySchedule[ksRow - 4];
          }

          if (invKsRow < 4 || ksRow <= 4) {
            invKeySchedule[invKsRow] = t;
          } else {
            invKeySchedule[invKsRow] = invSubMix0[sbox[t >>> 24]] ^ invSubMix1[sbox[(t >>> 16) & 0xff]] ^ invSubMix2[sbox[(t >>> 8) & 0xff]] ^ invSubMix3[sbox[t & 0xff]];
          }

          invKeySchedule[invKsRow] = invKeySchedule[invKsRow] >>> 0;
        }
      }

      // Adding this as a method greatly improves performance.
      networkToHostOrderSwap (word) {
        return (word << 24) | ((word & 0xff00) << 8) | ((word & 0xff0000) >> 8) | (word >>> 24);
      }

      decrypt (inputArrayBuffer, offset, aesIV, removePKCS7Padding) {
        let nRounds = this.keySize + 6;
        let invKeySchedule = this.invKeySchedule;
        let invSBOX = this.invSBox;

        let invSubMix = this.invSubMix;
        let invSubMix0 = invSubMix[0];
        let invSubMix1 = invSubMix[1];
        let invSubMix2 = invSubMix[2];
        let invSubMix3 = invSubMix[3];

        let initVector = this.uint8ArrayToUint32Array_(aesIV);
        let initVector0 = initVector[0];
        let initVector1 = initVector[1];
        let initVector2 = initVector[2];
        let initVector3 = initVector[3];

        let inputInt32 = new Int32Array(inputArrayBuffer);
        let outputInt32 = new Int32Array(inputInt32.length);

        let t0, t1, t2, t3;
        let s0, s1, s2, s3;
        let inputWords0, inputWords1, inputWords2, inputWords3;

        let ksRow, i;
        let swapWord = this.networkToHostOrderSwap;

        while (offset < inputInt32.length) {
          inputWords0 = swapWord(inputInt32[offset]);
          inputWords1 = swapWord(inputInt32[offset + 1]);
          inputWords2 = swapWord(inputInt32[offset + 2]);
          inputWords3 = swapWord(inputInt32[offset + 3]);

          s0 = inputWords0 ^ invKeySchedule[0];
          s1 = inputWords3 ^ invKeySchedule[1];
          s2 = inputWords2 ^ invKeySchedule[2];
          s3 = inputWords1 ^ invKeySchedule[3];

          ksRow = 4;

          // Iterate through the rounds of decryption
          for (i = 1; i < nRounds; i++) {
            t0 = invSubMix0[s0 >>> 24] ^ invSubMix1[(s1 >> 16) & 0xff] ^ invSubMix2[(s2 >> 8) & 0xff] ^ invSubMix3[s3 & 0xff] ^ invKeySchedule[ksRow];
            t1 = invSubMix0[s1 >>> 24] ^ invSubMix1[(s2 >> 16) & 0xff] ^ invSubMix2[(s3 >> 8) & 0xff] ^ invSubMix3[s0 & 0xff] ^ invKeySchedule[ksRow + 1];
            t2 = invSubMix0[s2 >>> 24] ^ invSubMix1[(s3 >> 16) & 0xff] ^ invSubMix2[(s0 >> 8) & 0xff] ^ invSubMix3[s1 & 0xff] ^ invKeySchedule[ksRow + 2];
            t3 = invSubMix0[s3 >>> 24] ^ invSubMix1[(s0 >> 16) & 0xff] ^ invSubMix2[(s1 >> 8) & 0xff] ^ invSubMix3[s2 & 0xff] ^ invKeySchedule[ksRow + 3];
            // Update state
            s0 = t0;
            s1 = t1;
            s2 = t2;
            s3 = t3;

            ksRow = ksRow + 4;
          }

          // Shift rows, sub bytes, add round key
          t0 = ((invSBOX[s0 >>> 24] << 24) ^ (invSBOX[(s1 >> 16) & 0xff] << 16) ^ (invSBOX[(s2 >> 8) & 0xff] << 8) ^ invSBOX[s3 & 0xff]) ^ invKeySchedule[ksRow];
          t1 = ((invSBOX[s1 >>> 24] << 24) ^ (invSBOX[(s2 >> 16) & 0xff] << 16) ^ (invSBOX[(s3 >> 8) & 0xff] << 8) ^ invSBOX[s0 & 0xff]) ^ invKeySchedule[ksRow + 1];
          t2 = ((invSBOX[s2 >>> 24] << 24) ^ (invSBOX[(s3 >> 16) & 0xff] << 16) ^ (invSBOX[(s0 >> 8) & 0xff] << 8) ^ invSBOX[s1 & 0xff]) ^ invKeySchedule[ksRow + 2];
          t3 = ((invSBOX[s3 >>> 24] << 24) ^ (invSBOX[(s0 >> 16) & 0xff] << 16) ^ (invSBOX[(s1 >> 8) & 0xff] << 8) ^ invSBOX[s2 & 0xff]) ^ invKeySchedule[ksRow + 3];
          ksRow = ksRow + 3;

          // Write
          outputInt32[offset] = swapWord(t0 ^ initVector0);
          outputInt32[offset + 1] = swapWord(t3 ^ initVector1);
          outputInt32[offset + 2] = swapWord(t2 ^ initVector2);
          outputInt32[offset + 3] = swapWord(t1 ^ initVector3);

          // reset initVector to last 4 unsigned int
          initVector0 = inputWords0;
          initVector1 = inputWords1;
          initVector2 = inputWords2;
          initVector3 = inputWords3;

          offset = offset + 4;
        }

        return removePKCS7Padding ? removePadding(outputInt32.buffer) : outputInt32.buffer;
      }

      destroy () {
        this.key = undefined;
        this.keySize = undefined;
        this.ksRows = undefined;

        this.sBox = undefined;
        this.invSBox = undefined;
        this.subMix = undefined;
        this.invSubMix = undefined;
        this.keySchedule = undefined;
        this.invKeySchedule = undefined;

        this.rcon = undefined;
      }
    }

    export default AESDecryptor;