Fix buffer overflows in RegisterCommand on mac (#99)

src/discord_register_osx.m

@@ -5,45 +5,28 @@
 
 #include "discord_register.h"
 
-static bool Mkdir(const char* path)
-{
-    int result = mkdir(path, 0755);
-    if (result == 0) {
-        return true;
-    }
-    if (errno == EEXIST) {
-        return true;
-    }
-    return false;
-}
-
 static void RegisterCommand(const char* applicationId, const char* command)
 {
     // There does not appear to be a way to register arbitrary commands on OSX, so instead we'll save the command
     // to a file in the Discord config path, and when it is needed, Discord can try to load the file there, open
     // the command therein (will pass to js's window.open, so requires a url-like thing)
 
-    const char* home = getenv("HOME");
+    // Note: will not work for sandboxed apps
+  	NSString *home = NSHomeDirectory();
     if (!home) {
         return;
     }
 
-    char path[2048];
-    sprintf(path, "%s/Library/Application Support/discord", home);
-    Mkdir(path);
-    strcat(path, "/games");
-    Mkdir(path);
-    strcat(path, "/");
-    strcat(path, applicationId);
-    strcat(path, ".json");
+    NSString *path = [[[[[[home stringByAppendingPathComponent:@"Library"]
+                                stringByAppendingPathComponent:@"Application Support"]
+                                stringByAppendingPathComponent:@"discord"]
+                                stringByAppendingPathComponent:@"games"]
+                                stringByAppendingPathComponent:[NSString stringWithUTF8String:applicationId]]
+                                stringByAppendingPathExtension:@"json"];
+    [[NSFileManager defaultManager] createDirectoryAtPath:[path stringByDeletingLastPathComponent] withIntermediateDirectories:YES attributes:nil error:nil];
 
-    FILE* f = fopen(path, "w");
-    if (f) {
-        char jsonBuffer[2048];
-        int len = snprintf(jsonBuffer, sizeof(jsonBuffer), "{\"command\": \"%s\"}", command);
-        fwrite(jsonBuffer, (size_t)len, 1, f);
-        fclose(f);
-    }
+    NSString *jsonBuffer = [NSString stringWithFormat:@"{\"command\": \"%s\"}", command];
+    [jsonBuffer writeToFile:path atomically:NO encoding:NSUTF8StringEncoding error:nil];
 }
 
 static void RegisterURL(const char* applicationId)
@@ -83,15 +66,15 @@ void Discord_Register(const char* applicationId, const char* command)
     }
     else {
         // raii lite
-        void* pool = [[NSAutoreleasePool alloc] init];
+        @autoreleasepool {
             RegisterURL(applicationId);
-        [(id)pool drain];
+        }
     }
 }
 
 void Discord_RegisterSteamGame(const char* applicationId, const char* steamId)
 {
     char command[256];
-    sprintf(command, "steam://rungameid/%s", steamId);
+    snprintf(command, 256, "steam://rungameid/%s", steamId);
     Discord_Register(applicationId, command);
 }