Libcurl post request not working on Windows 7 - c++

Question

I am trying to make a simple POST request to my https REST API and receive the response on a Windows 7 operation system. The firewall is deactivated and the certificate is inside the .exe directory.
Here is the code that I am using:
std::string postRequest(std::string json, std::string endpoint,std::string code,std::string patchOrPOST,std::string source)
{
CURL* curl;
CURLcode res;
std::string response;
curl_global_init(CURL_GLOBAL_ALL);
curl = curl_easy_init();
std::string authorization = "Authorization: Basic " + code, portApiHttp = "Referer: " + portAPI + "/index.html", origin = "Origin: " + portAPI;//X-Requested-With: XMLHttpRequest
struct curl_slist* headers = NULL;
if (curl) {
headers = curl_slist_append(headers, "Connection: keep-alive");
headers = curl_slist_append(headers, "Content-Length: "+(int)strlen(json.c_str()));
headers = curl_slist_append(headers, authorization.c_str());
headers = curl_slist_append(headers, "Accept: application/json");
headers = curl_slist_append(headers, "Content-Type: application/json");
if (source.size() != 0)
{
headers = curl_slist_append(headers, source.c_str());
}
headers = curl_slist_append(headers, R"(sec-ch-ua: "Chromium";v="91")");
headers = curl_slist_append(headers, "sec-ch-ua-mobile: ?0");
headers = curl_slist_append(headers, "X - Requested - With: XMLHttpRequest");
headers = curl_slist_append(headers, origin.c_str());
headers = curl_slist_append(headers, "Sec-Fetch-Site: same-origin");
headers = curl_slist_append(headers, "Sec-Fetch-Mode: cors");
headers = curl_slist_append(headers, "Sec-Fetch-Dest: empty");
headers = curl_slist_append(headers, portApiHttp.c_str());
headers = curl_slist_append(headers, "Accept-Encoding: gzip, deflate, br");
headers = curl_slist_append(headers, "Accept-Language: en-US,en;q=0.9");
curl_easy_setopt(curl, CURLOPT_URL,endpoint.c_str());
curl_easy_setopt(curl, CURLOPT_CAINFO, "ca-bundle.crt");
curl_easy_setopt(curl, CURLOPT_NOPROGRESS, 1L);
if (patchOrPOST == "PATCH")
{
curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "PATCH");
}
else if (patchOrPOST == "PUT")
{
curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "PUT");
}
else if (patchOrPOST == "GET")
{
curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "GET");
}
else if(patchOrPOST=="DELETE")
{
curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "DELETE");
}
//curl_easy_setopt(curl, CURLOPT_PROXY, "127.0.0.1:8888");
curl_easy_setopt(curl, CURLOPT_POSTFIELDS, json.c_str());
curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
curl_easy_setopt(curl, CURLOPT_MAXREDIRS, 5L);
curl_easy_setopt(curl, CURLOPT_TIMEOUT, 50L);
curl_easy_setopt(curl, CURLOPT_HEADER, 1);
curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0);
if (patchOrPOST != "GET")
{
curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE, json.size());
curl_easy_setopt(curl, CURLOPT_POST, 1);
}
res= curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteCallback);
if (res!= CURLE_OK) {
curl_easy_cleanup(curl);
return "ERROR";
}
res= curl_easy_setopt(curl, CURLOPT_WRITEDATA, &response);
if (res!= CURLE_OK) {
curl_easy_cleanup(curl);
return "ERROR";
}
res = curl_easy_perform(curl);
long http_code;
/* Check for errors */
if (res != CURLE_OK)
fprintf(stderr, "curl_easy_perform() failed: %s\n",
curl_easy_strerror(res));
/* always cleanup */
curl_easy_cleanup(curl);
}
curl_global_cleanup();
return response;
}
Why does this code work on Windows 10, but has SSL issues on Windows 7?

Answer 1

Why does this code work on Windows 10, but has SSL issues on Windows 7?
Most likely, the server is requesting stronger cryptographic suites than what Windows 7 can provide.

Answer 2

I have similar issue with Windows 7 and libcurl. I have found a solution. I was using libcurl with schannel (default for windows when using vcpkg). The problem was solved when I built libcurl with openssl instead.
If you are using vcpkg, you can install libcurl with openssl with this command:
vckpg.exe install curl[openssl]
You can download a precompiled binary from curl site too. I got the hint solve this from this default windows build for curl:
https://github.com/curl/curl-for-win