code: function encrypt_aes_cbc_sha1_padding(blockSize, input, decrypt) {
    /* The encrypted data length (TLSCiphertext.length) is one more than the sum
     of SecurityParameters.block_length, TLSCompressed.length,
     SecurityParameters.mac_length, and padding_length.
  
     The padding may be any length up to 255 bytes long, as long as it results in
     the TLSCiphertext.length being an integral multiple of the block length.
     Lengths longer than necessary might be desirable to frustrate attacks on a
     protocol based on analysis of the lengths of exchanged messages. Each uint8
     in the padding data vector must be filled with the padding length value.
  
     The padding length should be such that the total size of the
     GenericBlockCipher structure is a multiple of the cipher's block length.
     Legal values range from zero to 255, inclusive. This length specifies the
     length of the padding field exclusive of the padding_length field itself.
  
     This is slightly different from PKCS#7 because the padding value is 1
     less than the actual number of padding bytes if you include the
     padding_length uint8 itself as a padding byte. */
    if(!decrypt) {
      // get the number of padding bytes required to reach the blockSize and
      // subtract 1 for the padding value (to make room for the padding_length
      // uint8)
      var padding = blockSize - (input.length() % blockSize);
      input.fillWithByte(padding - 1, padding);
    }
    return true;
  }
docs: Handles padding for aes_cbc_sha1 in encrypt mode.
  
  @param blockSize the block size.
  @param input the input buffer.
  @param decrypt true in decrypt mode, false in encrypt mode.
  
  @return true on success, false on failure.