obs-streamer-tools-plugin/core/src/http_curl.cpp

/*
streamer-tools OBS Camera Plugin - libcurl HTTP backend (Linux/macOS)
Copyright (C) 2026 CyberCoveLLC <jknapp85@gmail.com>

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0
*/

#include "stplugin/http.h"

#include <curl/curl.h>

#include <cstddef>
#include <mutex>

namespace stplugin {

namespace {

/// Hard cap on a response body. The two endpoints this client talks to return
/// a few hundred bytes; anything larger is a misconfigured proxy or a wrong
/// URL, and must not be allowed to grow OBS's heap without bound.
constexpr std::size_t kMaxResponseBytes = 4u * 1024u * 1024u;

struct WriteContext {
    std::string body;
    bool overflowed = false;
};

std::size_t writeCallback(char *ptr, std::size_t size, std::size_t nmemb, void *userdata)
{
    auto *ctx = static_cast<WriteContext *>(userdata);
    const std::size_t bytes = size * nmemb;
    if (ctx->body.size() + bytes > kMaxResponseBytes) {
        ctx->overflowed = true;
        return 0; // aborts the transfer with CURLE_WRITE_ERROR
    }
    ctx->body.append(ptr, bytes);
    return bytes;
}

/// curl_global_init is not thread-safe and must run once per process before
/// any easy handle is created. OBS may create several sources concurrently.
void ensureCurlGlobalInit()
{
    static std::once_flag once;
    std::call_once(once, [] { curl_global_init(CURL_GLOBAL_DEFAULT); });
}

class CurlHttpClient : public HttpClient {
public:
    HttpResponse send(const HttpRequest &request) override
    {
        ensureCurlGlobalInit();

        HttpResponse response;
        CURL *curl = curl_easy_init();
        if (!curl) {
            response.network_error = "curl_easy_init failed";
            return response;
        }

        WriteContext ctx;
        struct curl_slist *headers = nullptr;

        curl_easy_setopt(curl, CURLOPT_URL, request.url.c_str());
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, writeCallback);
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, &ctx);
        curl_easy_setopt(curl, CURLOPT_TIMEOUT_MS, static_cast<long>(request.timeout_ms));
        curl_easy_setopt(curl, CURLOPT_CONNECTTIMEOUT_MS, static_cast<long>(request.timeout_ms));
        // Redirects are never legitimate here: this client only ever talks to
        // two fixed, first-party streamer-tools API endpoints, and the read
        // key travels as a URL query parameter (see api_client.cpp). Blindly
        // following a redirect -- including an HTTPS->HTTP downgrade, which
        // curl does not refuse by default -- would hand that key to whatever
        // host the redirect points at. A redirect from our own server is a
        // configuration error, so treat it as a failed request instead of
        // silently following it. This also brings this backend in line with
        // http_winhttp.cpp, which already refuses HTTPS->HTTP downgrades by
        // default.
        curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 0L);
        curl_easy_setopt(curl, CURLOPT_USERAGENT, "streamer-tools-obs-plugin/1.0");
        // NOSIGNAL is required whenever curl is used off the main thread:
        // without it curl installs a SIGALRM handler for DNS timeouts, which
        // is process-global and would be a rude thing to do inside OBS.
        curl_easy_setopt(curl, CURLOPT_NOSIGNAL, 1L);
        // TLS verification stays on. The read key is a credential; sending it
        // to an unverified host is exactly the failure this must not have.
        curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 1L);
        curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 2L);

        if (request.method == "POST") {
            curl_easy_setopt(curl, CURLOPT_POST, 1L);
            curl_easy_setopt(curl, CURLOPT_POSTFIELDS, request.body.c_str());
            curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE, static_cast<long>(request.body.size()));
        } else if (request.method != "GET") {
            curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, request.method.c_str());
        }

        if (!request.content_type.empty()) {
            const std::string header = "Content-Type: " + request.content_type;
            headers = curl_slist_append(headers, header.c_str());
        }
        // Fastify answers a bare POST with no body fine, but some proxies
        // insert an Expect: 100-continue round trip; suppress it.
        headers = curl_slist_append(headers, "Expect:");
        if (headers)
            curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);

        const CURLcode rc = curl_easy_perform(curl);
        if (rc == CURLE_OK) {
            long status = 0;
            curl_easy_getinfo(curl, CURLINFO_RESPONSE_CODE, &status);
            response.status = status;
            response.body = std::move(ctx.body);
        } else if (ctx.overflowed) {
            response.network_error = "response body exceeded 4 MiB";
        } else {
            response.network_error = curl_easy_strerror(rc);
        }

        if (headers)
            curl_slist_free_all(headers);
        curl_easy_cleanup(curl);
        return response;
    }
};

} // namespace

HttpClient *createPlatformHttpClient()
{
    return new CurlHttpClient();
}

} // namespace stplugin