Web assembly: Using crypto++ library with emscripten - c++

Question

I'm planning on using the crypto++ library for a web application and wasm seemed perfect for it.
My cpp code:
#include <string>
using std::string;
#include "cryptopp/cryptlib.h"
#include "cryptopp/rsa.h"
#include "cryptopp/files.h"
#include "cryptopp/osrng.h"
using CryptoPP::RSA;
using CryptoPP::InvertibleRSAFunction;
using CryptoPP::RSAES_OAEP_SHA_Encryptor;
using CryptoPP::RSAES_OAEP_SHA_Decryptor;
using CryptoPP::StringSink;
using CryptoPP::StringSource;
using CryptoPP::PK_EncryptorFilter;
using CryptoPP::PK_DecryptorFilter;
using CryptoPP::FileSink;
using CryptoPP::FileSource;
using CryptoPP::AutoSeededRandomPool;
using CryptoPP::DecodingResult;
using CryptoPP::SHA1;
using namespace CryptoPP;
extern "C" {
char* generateKeys() {
AutoSeededRandomPool rng;
InvertibleRSAFunction parameters;
parameters.GenerateRandomWithKeySize(rng, 1024);
RSA::PrivateKey privateKey(parameters);
RSA::PublicKey publicKey(parameters);
string pubKey;
publicKey.Save(StringSink(pubKey).Ref());
privateKey.Save(FileSink("privkey.der", true).Ref());
int n = pubKey.length();
char* char_array = new char[n + 1];
strcpy(char_array, pubKey.c_str());
return char_array;
}
}
extern "C" {
char* encrypt(string pubKey, string plain) {
AutoSeededRandomPool rng;
string cipher;
RSA::PublicKey publicKey;
publicKey.Load(StringSource(pubKey, true, NULL).Ref());
RSAES_OAEP_SHA_Encryptor e(publicKey);
StringSource(plain, true,
new PK_EncryptorFilter(rng, e,
new StringSink(cipher)
) // PK_EncryptorFilter
); // StringSource
int n = cipher.length();
char* char_array = new char[n + 1];
strcpy(char_array, cipher.c_str());
return char_array;
}
}
extern "C" {
char* decrypt(const char* filename, string cipher) {
AutoSeededRandomPool rng;
RSA::PrivateKey privateKey;
string recovered;
privateKey.Load(FileSource(filename, true).Ref());
RSAES_OAEP_SHA_Decryptor d(privateKey);
StringSource(cipher, true,
new PK_DecryptorFilter(rng, d,
new StringSink(recovered)
) // PK_EncryptorFilter
); // StringSource
int n = recovered.length();
char* char_array = new char[n + 1];
strcpy(char_array, recovered.c_str());
return char_array;
}
}
I referred emscripten documentation for using libraries in emscripten
I created cryptlib.a using the cryptlib.cpp file and compiled it using emcc like so
emcc -c -o cryptlib.o cryptlib.cpp
ar rcs cryptlib.a cryptlib.o
Finally I also created Source.o like so
emcc -c -o Source.o Source.cpp
I figured out that this would the command to get an html and js file
emcc Source.o cryptlib.a -o source.html -sEXPORTED_FUNCTIONS=_generateKeys -sEXPORTED_RUNTIME_METHODS=ccall,cwrap
I get wasm-ld errors like so
Error screenshots
What am I doing wrong? I also want to expose other functions of my source code but I was testing with just one of the functions.

Answer 1

Looks like you try to use the native version of crypto++, and this will only work if you build the webassembly version of the library.
EDIT: sorry... you were already trying that...
I saw your question here as I was doing it myself.
this is what I just published, which might help:
=> wasm online demo:
===> https://guillaumebouchetepitech.github.io/wasm-cryptopp-demo/dist/index.html
=> source code:
===> https://github.com/GuillaumeBouchetEpitech/wasm-cryptopp-demo
PS: I've added the code to set/get string values to/from the js/wasm code as well, it's not overly well done but it feels like you could also get started on that side as well thanks to it.
let me know.