I am relatively new to C and I am trying to encrypt a string data in C.

I have been provided with a PUBLIC KEY that is somewhat like

-----BEGIN PUBLIC KEY----- MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA1WRkqlsZbmaNWbOZr/M4 
.
.
.
 EKseLc8iKzkwEQcuyMn4znaFpnOL0CmSrYB5K1E9zmmtDhMvDs540ZotcH/xpJiV BwIDAQAB
-----END PUBLIC KEY-----

And a sample representation of what I am trying to achieve in Typescript

rsaEncrypt(text: string, publicKey: string): Promise<string> {
    const buffer = Buffer.from(JSON.stringify(text));
    const encrypted = publicEncrypt(
      {
        key: publicKey,
        padding: constants.RSA_PKCS1_OAEP_PADDING,
        oaepHash: 'sha1',
      },
      buffer,
    );
    return encrypted.toString('base64');
  }

This is my implementation however, my rsa is always NULL after PEM_read_bio_RSA_PUBKEY

int rsa_encrypt(const unsigned char *msg, size_t msg_len, unsigned char **enc_msg, size_t *enc_msg_len) {
    RSA *rsa = NULL;
    BIO *bio = NULL;
    int ret = -1;

    tappa_print("%s", "In rsa_enc");
    tappa_print("%s", PUBLIC_KEY);
    bio = BIO_new_mem_buf(PUBLIC_KEY, -1);
    tappa_printf("Bio %d", BIO_get_init(bio));
    if (bio == NULL) {
        fprintf(stderr, "Error creating bion");
        return -1;
    }

    rsa = PEM_read_bio_RSA_PUBKEY(bio, NULL, NULL, NULL);
    tappa_printf("RSA %d", rsa==NULL);
    if (rsa == NULL) {
        ERR_print_errors_fp(stderr);
        tappa_print("%s", strerror(errno));
        fprintf(stderr, "Error reading public keyn");
        //BIO_free(bio);
        return -1;
    }
    tappa_printf("RSA %d", RSA_size(rsa));
    *enc_msg = (unsigned char *)malloc(RSA_size(rsa));
    tappa_printf("Enc msg %d", sizeof *enc_msg);
    if (*enc_msg == NULL) {
        fprintf(stderr, "Memory allocation errorn");
        RSA_free(rsa);
        BIO_free(bio);
        return -1;
    }

    *enc_msg_len = RSA_public_encrypt(msg_len, msg, *enc_msg, rsa, RSA_PKCS1_PADDING);
    tappa_printf("Enc msg len%d", sizeof *enc_msg_len);
    if (*enc_msg_len == -1) {
        fprintf(stderr, "Encryption errorn");
        free(*enc_msg);
        RSA_free(rsa);
        BIO_free(bio);
        return -1;
    }

    ret = 0;

    tappa_printf("ret msg %d", ret);
    RSA_free(rsa);
    BIO_free(bio);

    return ret;
}

I tried another approach I saw on the internet, reading the key from a file however, I am faced with “No such file/directory” error after adding the file to my project

  FILE* fp =fopen("public.txt","r");

    if(fp==NULL){
        perror("file error");
        return NULL;
    }