====== 3.3 WASM Build for Blazor ======

This guide explains how to compile OpenSSL for Blazor WebAssembly.

----

===== What is WebAssembly? =====

**WebAssembly (WASM)** is a binary format that runs in the browser. It enables:
  * High-performance code in the browser
  * Using languages like C/C++ on the web
  * Blazor WebAssembly applications

<WRAP info>
**When do I need WASM?**

| Application Type | WASM needed? |
|------------------|--------------|
| Blazor WebAssembly | **Yes** |
| Blazor Server | No (uses Windows/Linux build) |
| ASP.NET Core API | No |
| Desktop App (.NET) | No |
</WRAP>

----

===== Prerequisites =====

In addition to standard tools you need:

  * ☑ [[.:..vorbereitung:wsl-einrichten|WSL2 with Ubuntu/Fedora]]
  * ☑ [[.:..vorbereitung:emscripten|Emscripten SDK]]

<WRAP important>
WASM builds are only possible under Linux/WSL, not directly under Windows!
</WRAP>

----

===== Build Overview =====

The WASM build creates:
  * ''openssl.js'' - JavaScript loader
  * ''openssl.wasm'' - WebAssembly module
  * C wrapper for Post-Quantum functions

----

===== Build Steps =====

==== Step 1: Open WSL ====

<code bash>
# Open WSL terminal
wsl
</code>

==== Step 2: Activate Emscripten ====

<code bash>
# Load Emscripten environment
source /opt/emsdk/emsdk_env.sh

# Verify
emcc --version
# Should show: emcc (Emscripten gcc/clang-like replacement) 3.x.x
</code>

==== Step 3: Prepare Build Directory ====

<code bash>
# Create directories
mkdir -p /mnt/d/Projects/openssl-3.6.0/wasm-build
mkdir -p /mnt/d/Projects/openssl-3.6.0/wasm-install

cd /mnt/d/Projects/openssl-3.6.0/wasm-build
</code>

==== Step 4: Configure OpenSSL for WASM ====

<code bash>
emconfigure /mnt/d/Projects/openssl-3.6.0/src/Configure \
    linux-generic32 \
    --prefix=/mnt/d/Projects/openssl-3.6.0/wasm-install \
    --openssldir=/mnt/d/Projects/openssl-3.6.0/wasm-install/ssl \
    no-asm \
    no-threads \
    no-shared \
    no-dso \
    no-engine \
    no-hw \
    no-async \
    no-sock \
    no-dgram \
    no-tests \
    no-apps \
    -DOPENSSL_NO_SECURE_MEMORY \
    CC=emcc \
    AR=emar \
    RANLIB=emranlib
</code>

**Explanation of options:**

| Option | Meaning |
|--------|---------|
| ''linux-generic32'' | Generic 32-bit platform |
| ''no-asm'' | No assembly (WASM can't use x86 assembly) |
| ''no-threads'' | No threads (Web Workers separate) |
| ''no-shared'' | Static library only |
| ''no-sock'' | No socket support |
| ''no-tests'' | Don't build tests |
| ''no-apps'' | No openssl CLI tool |

==== Step 5: Compile ====

<code bash>
emmake make -j$(nproc) build_libs
</code>

==== Step 6: Install ====

<code bash>
emmake make install_sw
</code>

----

===== Create JavaScript Wrapper =====

For integration into Blazor we need a wrapper:

==== wvds_crypto_wrapper.c ====

<code c>
// WvdS Crypto WASM Wrapper
#include <emscripten.h>
#include <openssl/evp.h>
#include <openssl/x509.h>
#include <openssl/err.h>
#include <string.h>
#include <stdlib.h>

// Initialization
EMSCRIPTEN_KEEPALIVE
int wvds_init(void) {
    OPENSSL_init_crypto(
        OPENSSL_INIT_LOAD_CRYPTO_STRINGS |
        OPENSSL_INIT_ADD_ALL_CIPHERS |
        OPENSSL_INIT_ADD_ALL_DIGESTS, NULL);
    return 1;
}

// OpenSSL Version
EMSCRIPTEN_KEEPALIVE
const char* wvds_get_version(void) {
    return OPENSSL_VERSION_TEXT;
}

// ML-DSA Key Generation
EMSCRIPTEN_KEEPALIVE
int wvds_mldsa_keygen(const char* algorithm,
                       unsigned char** pub_key, int* pub_len,
                       unsigned char** priv_key, int* priv_len) {
    EVP_PKEY_CTX *ctx = NULL;
    EVP_PKEY *pkey = NULL;
    int ret = 0;

    // Algorithm name for OpenSSL
    const char* ossl_alg = algorithm;
    if (strcmp(algorithm, "ML-DSA-44") == 0) ossl_alg = "mldsa44";
    else if (strcmp(algorithm, "ML-DSA-65") == 0) ossl_alg = "mldsa65";
    else if (strcmp(algorithm, "ML-DSA-87") == 0) ossl_alg = "mldsa87";

    ctx = EVP_PKEY_CTX_new_from_name(NULL, ossl_alg, NULL);
    if (!ctx) goto err;

    if (EVP_PKEY_keygen_init(ctx) <= 0) goto err;
    if (EVP_PKEY_keygen(ctx, &pkey) <= 0) goto err;

    // Export public key
    *pub_len = i2d_PUBKEY(pkey, NULL);
    *pub_key = malloc(*pub_len);
    unsigned char *p = *pub_key;
    i2d_PUBKEY(pkey, &p);

    // Export private key
    *priv_len = i2d_PrivateKey(pkey, NULL);
    *priv_key = malloc(*priv_len);
    p = *priv_key;
    i2d_PrivateKey(pkey, &p);

    ret = 1;

err:
    EVP_PKEY_free(pkey);
    EVP_PKEY_CTX_free(ctx);
    return ret;
}

// Free memory
EMSCRIPTEN_KEEPALIVE
void wvds_free(void* ptr) {
    free(ptr);
}
</code>

==== Compile Wrapper ====

<code bash>
INSTALL_DIR=/mnt/d/Projects/openssl-3.6.0/wasm-install
OUTPUT=/mnt/d/Projects/openssl-3.6.0/wasm-build

emcc $OUTPUT/wvds_crypto_wrapper.c \
    -I"$INSTALL_DIR/include" \
    -L"$INSTALL_DIR/lib" \
    -lcrypto \
    -Os \
    -s WASM=1 \
    -s MODULARIZE=1 \
    -s EXPORT_NAME="OpenSSLModule" \
    -s EXPORTED_FUNCTIONS='["_wvds_init","_wvds_get_version","_wvds_mldsa_keygen","_wvds_free","_malloc","_free"]' \
    -s EXPORTED_RUNTIME_METHODS='["ccall","cwrap","getValue","setValue","UTF8ToString"]' \
    -s ALLOW_MEMORY_GROWTH=1 \
    -o "$OUTPUT/openssl.js"
</code>

----

===== Result =====

After the build:

<code>
wasm-build/
├── openssl.js    # JavaScript Loader (~150 KB)
└── openssl.wasm  # WebAssembly Module (~2 MB)
</code>

----

===== Integrate into Blazor =====

==== 1. Copy Files ====

<code bash>
cp openssl.js openssl.wasm /mnt/d/MyProject/wwwroot/
</code>

==== 2. Load in index.html ====

<code html>
<script src="openssl.js"></script>
<script>
    var cryptoModule = null;

    OpenSSLModule().then(function(module) {
        cryptoModule = module;
        module._wvds_init();
        console.log("OpenSSL Version:", module.ccall('wvds_get_version', 'string', [], []));
    });
</script>
</code>

==== 3. Call from Blazor ====

<code csharp>
// In your Blazor component
@inject IJSRuntime JS

public async Task<string> GetOpenSslVersion()
{
    return await JS.InvokeAsync<string>("eval",
        "cryptoModule.ccall('wvds_get_version', 'string', [], [])");
}
</code>

----

===== Continue to =====

  * [[.:vorbereitung:emscripten|Install Emscripten SDK]]
  * [[.:integration:blazor-wasm|Blazor WASM Integration]]
  * [[.:build:start|Back to Build Overview]]

----
//Wolfgang van der Stille @ EMSR DATA d.o.o. - Post-Quantum Cryptography Professional//