I ended up written my own runtime-level equivalent of +[NSObject isSubclassOfClass:] using only class_getSuperclass and object_getClass. This class scanning code, currently used for plugin scanning, will also be used in jailbreak detecting, defeating Cydia Substrate-based iAP crackers.
> On Dec 16, 2014, at 06:25, Wim Lewis <w...@omnigroup.com> wrote:
>
>
> On Dec 13, 2014, at 11:06 AM, Maxthon Chan <m...@maxchan.info> wrote:
>> What I am doing here is scanning all loaded classes for subclasses of a
>> certain class. Before any NSObject method can be issued I have to check if
>> it is actually NSObject or NSProxy derivative instead of an Object
>> derivative that does not support NSObject methods. This calls for runtime
>> equivalent for one of the following NSObject methods:
>
> For what it’s worth we’ve run into this same problem at Omni— we have some
> code (that runs in debug builds, but not release builds, IIRC) that scans the
> class hierarchy. We simply ignore a bunch of classes that we’ve had problems
> with. This works, but it’s a little bit brittle because who knows when
> another class will appear in the runtime that can’t handle
> -respondsToSelector: and break your shipping application.
>
>
>> /* Some classes (that aren't our problem) asplode when they try to
>> dynamically create getters/setters. */
>> const char *clsName = class_getName(cls);
>> if (CLASSNAME_HAS_PREFIX(clsName, "NS") ||
>> CLASSNAME_HAS_PREFIX(clsName, "_NS") ||
>> CLASSNAME_HAS_PREFIX(clsName, "__NS") ||
>> CLASSNAME_HAS_PREFIX(clsName, "__CF") ||
>> CLASSNAME_HAS_PREFIX(clsName, "CA") ||
>> CLASSNAME_HAS_PREFIX(clsName, "_CN") ||
>> CLASSNAME_HAS_PREFIX(clsName, "VGL") ||
>> CLASSNAME_HAS_PREFIX(clsName, "VK") ||
>> strcmp(clsName, "DRDevice") == 0) {
>> /* In particular, _NS[View]Animator chokes in this case. But we
>> don't really need to check any _NS classes. */
>> continue;
>> }
>
>
> On Dec 15, 2014, at 10:23 AM, David Duncan <david.dun...@apple.com> wrote:
>> And also, if you are loading the bundle, then again there is little need to
>> do actual class walking as such, since you are in control of the bundle and
>> its formatting. Require the bundles to tell you the classes that are
>> SKFormat subclasses in the bundle’s property list and only use those.
>
> IMHO this is the best approach to the problem.
>
> Another approach is you could watch for the NSBundleDidLoadNotification and
> only scan the classes in the NSLoadedClasses entry. But I think that
> requiring the plugin to explicitly list the classes you should scan in its
> Info.plist is a good approach.
>
>
>
>
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