Minimize data sent in the default user agent (#14851)

src/httpfetch.cpp

@@ -40,10 +40,17 @@ static std::unordered_map<u64, std::queue<HTTPFetchResult>>
 	g_httpfetch_results;
 static PcgRandom g_callerid_randomness;
 
+static std::string default_user_agent()
+{
+	std::string ret(PROJECT_NAME_C "/");
+	ret.append(g_version_string).append(" (").append(porting::get_sysinfo()).append(")");
+	return ret;
+}
+
 HTTPFetchRequest::HTTPFetchRequest() :
 	timeout(g_settings->getS32("curl_timeout")),
 	connect_timeout(10 * 1000),
-	useragent(std::string(PROJECT_NAME_C "/") + g_version_hash + " (" + porting::get_sysinfo() + ")")
+	useragent(default_user_agent())
 {
 	timeout = std::max(timeout, MIN_HTTPFETCH_TIMEOUT_INTERACTIVE);
 }

src/porting.cpp

@@ -50,6 +50,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #endif
 #if defined(__ANDROID__)
 	#include "porting_android.h"
+	#include <android/api-level.h>
 #endif
 #if defined(__APPLE__)
 	#include <mach-o/dyld.h>
@@ -205,7 +206,10 @@ bool detectMSVCBuildDir(const std::string &path)
 	return (!removeStringEnd(path, ends).empty());
 }
 
-std::string get_sysinfo()
+// Note that the system info is sent in every HTTP request, so keep it reasonably
+// privacy-conserving while ideally still being meaningful.
+
+static std::string detectSystemInfo()
 {
 #ifdef _WIN32
 	std::ostringstream oss;
@@ -251,14 +255,34 @@ std::string get_sysinfo()
 	delete[] filePath;
 
 	return oss.str();
-#else
+#elif defined(__ANDROID__)
+	std::ostringstream oss;
 	struct utsname osinfo;
 	uname(&osinfo);
-	return std::string(osinfo.sysname) + "/"
-		+ osinfo.release + " " + osinfo.machine;
+	int api = android_get_device_api_level();
+
+	oss << "Android/" << api << " " << osinfo.machine;
+	return oss.str();
+#else /* POSIX */
+	struct utsname osinfo;
+	uname(&osinfo);
+
+	std::string_view release(osinfo.release);
+	// cut off anything but the primary version number
+	release = release.substr(0, release.find_first_not_of("0123456789."));
+
+	std::string ret = osinfo.sysname;
+	ret.append("/").append(release).append(" ").append(osinfo.machine);
+	return ret;
 #endif
 }
 
+const std::string &get_sysinfo()
+{
+	static std::string ret = detectSystemInfo();
+	return ret;
+}
+
 
 bool getCurrentWorkingDir(char *buf, size_t len)
 {

src/porting.h

@@ -138,7 +138,7 @@ void initializePaths();
 	Return system information
 	e.g. "Linux/3.12.7 x86_64"
 */
-std::string get_sysinfo();
+const std::string &get_sysinfo();
 
 
 // Monotonic timer