example-gowasm-uselib

tinygo wasm use c library (AES¹ CBC² mode)

This project demonstrates the integration of a C library with Go-based WebAssembly and a Go HTTP server. The C library is used for AES¹ encryption, which is compiled to WebAssembly using Emscripten. The Go WebAssembly module interacts with this AES¹ library, and both are served over an HTTP server written in Go.

Structure

The project is divided into three main directories:

1. myaeslib: A C language-based AES¹ library. It is compiled using the Emscripten compiler and includes Makefile for building and installing the library.
2. mywasm: Contains Go code for the WebAssembly module that utilizes the myaeslib for encryption. It is compiled using the TinyGo compiler and includes Makefile for building and installing.
3. goserver: A simple HTTP server written in Go that serves the WebAssembly module and provides an interface to interact with the AES¹ encryption functionality.

Getting Started

Prerequisites

• Install Emscripten for compiling C code to WebAssembly.
• Install TinyGo for compiling Go code to WebAssembly.
• Install Go for running the HTTP server.

Building and Installing myaeslib

Navigate to the myaeslib directory:

cd myaeslib

Run Makefile commands to build and install the AES¹ library:

make
make install

install: copy libmyaes.a and myaes.hfrom output directory to mywasm/mycrypto

Building and Installing mywasm

Navigate to the mywasm directory:

cd mywasm

Run Makefile commands to build and install the WebAssembly module:

make
make install

install: copy mywasm.wasm and wasm_exec.jsfrom output directory to server/static

Running the HTTP Server

Navigate to the goserver directory:

cd goserver

Run the HTTP server:

go run main.go

The server will start, and you can access the WebAssembly module through the web browser at http://localhost:8080.

Usage Instructions

Starting the Server Once the server is running, navigate to http://localhost:8080 in your web browser. You should see an interface that allows you to interact with the AES¹ encryption functionality provided by the myaeslib library through WebAssembly.

Linking the Static Library The C library functions are defined in myaes.h as follows:

• int Encrypt(const uint8_t* sdkSecrty, const char* plaintext, char* out);: Encryption function
• int Decrypt(const uint8_t* sdkSecrty, const char* pOutB64, char* out);: Decryption function

To use these functions in Go code, prepare a Go package myaes.go to link the static library libmyaes.a.

Go Code Example

To call libmyaes.a using cgo, here's how you can link the static library and call the encryption and decryption functions in your Go code:

/*
#cgo LDFLAGS: -L. -lmyaes
#include "myaes.h"
*/
import "C"
import (
    "unsafe"
)

// Assume secrtyKey is a []byte slice containing the security key,
// plaintext is the string to encrypt, and ciphertext is the encrypted string.
// out is used to store the result of encryption or decryption.

// Encryption example
func Encrypt(secrtyKey []byte, plaintext string) string {
    var out [128]byte // Assume the output will not exceed 128 bytes
    C.Encrypt((*C.uint8_t)(&secrtyKey[0]), C.CString(plaintext), (*C.char)(unsafe.Pointer(&out[0])))
    return string(out[:])
}

// Decryption example
func Decrypt(secrtyKey []byte, ciphertext string) string {
    var out [128]byte // Assume the output will not exceed 128 bytes
    C.Decrypt((*C.uint8_t)(&secrtyKey[0]), C.CString(ciphertext), (*C.char)(unsafe.Pointer(&out[0])))
    return string(out[:])
}

Note: These examples assume the output will not exceed 128 bytes. In practice, depending on the size of your encrypted text, you might need to adjust the size of the out array.

Furthermore, the examples do not handle memory allocation and release for the strings returned from C.CString and C.Encrypt/C.Decrypt calls. In actual applications, ensure proper memory management to avoid memory leaks.

JavaScript Code Example

Load WebAssembly in index.html:

// Prepare a 32-byte secret key
let secret = new Uint8Array([31, 63, 210, 217, 114, 192, 171, 225, 29, 225, 12, 140, 3, 19, 110, 132, 188, 228, 132, 35, 144, 38, 168, 153, 210, 203, 150, 127, 141, 239, 8, 22]);
// Initialize AES
AesInit(secret);
// Encrypt
AesEncrypt("Advanced Encryption Standard $$$$$$$$$$$$$$$$$$$")
// Decrypt
AesDecrypt("Tkm0vfvenJfWwNEn/XwogrjOwN3p12U7HLcvtWgE/F4IxlbGGDIpx7KzgLES2fVB")

Contributing

Contributions are welcome! Please feel free to submit pull requests or open issues to improve the project.

License

This project is licensed under the MIT License - see the LICENSE file for details.

Footnotes

1. Advanced Encryption Standard ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷

2. Cipher Block Chaining ↩