Golang web assembly program that utilizes AES encryption.

Go WASM.go

package main

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"encoding/hex"
	"fmt"
	"io"
	random "math/rand"
	"syscall/js"

	"github.com/mergermarket/go-pkcs7"
)

func Encrypt(a js.Value, b []js.Value) interface{} {
	var i interface{}
	i = "Error"
	key_ := fmt.Sprintf("%v", b[0])
	unencrypted := fmt.Sprintf("%v", b[1])

	key := []byte(key_)
	plainText := []byte(unencrypted)
	plainText, err := pkcs7.Pad(plainText, aes.BlockSize)
	if err != nil {
		return i
	}
	if len(plainText)%aes.BlockSize != 0 {
		err := fmt.Errorf(`plainText: "%s" has the wrong block size`, plainText)
		i = "Error: " + err.Error()
		return i
	}

	block, err := aes.NewCipher(key)
	if err != nil {
		i = "Error: " + err.Error()
		return i
	}

	cipherText := make([]byte, aes.BlockSize+len(plainText))
	iv := cipherText[:aes.BlockSize]
	if _, err := io.ReadFull(rand.Reader, iv); err != nil {
		i = "Error: " + err.Error()
		return i
	}

	mode := cipher.NewCBCEncrypter(block, iv)
	mode.CryptBlocks(cipherText[aes.BlockSize:], plainText)

	i = fmt.Sprintf("%x", cipherText)
	return i
}

func Decrypt(a js.Value, b []js.Value) interface{} {
	var i interface{}
	i = "Error"

	key_ := fmt.Sprintf("%v", b[0])
	encrypted := fmt.Sprintf("%v", b[1])

	key := []byte(key_)
	cipherText, _ := hex.DecodeString(encrypted)

	block, err := aes.NewCipher(key)
	if err != nil {
		i = "Error: " + err.Error()
		return i
	}

	if len(cipherText) < aes.BlockSize {
		i = "Error: Ciphertext to short!"
		return i
	}
	iv := cipherText[:aes.BlockSize]
	cipherText = cipherText[aes.BlockSize:]
	if len(cipherText)%aes.BlockSize != 0 {
		i = "Error: cipherText is not a multiple of the block size"
		return i
	}

	mode := cipher.NewCBCDecrypter(block, iv)
	mode.CryptBlocks(cipherText, cipherText)

	cipherText, _ = pkcs7.Unpad(cipherText, aes.BlockSize)
	i = string(cipherText)
	return i
}

func generateKey(_ js.Value, _ []js.Value) interface{} {
	var letterRunes = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")

	b := make([]rune, 32)
	for i := range b {
		b[i] = letterRunes[random.Intn(len(letterRunes))]
	}
	var i interface{}
	i = string(b)
	return i
}

func main() {
	c := make(chan struct{}, 0)
	js.Global().Set("Encrypt", js.FuncOf(Encrypt))
	js.Global().Set("Decrypt", js.FuncOf(Decrypt))
	js.Global().Set("Generate", js.FuncOf(generateKey))
	<-c
}