In the early days of the iPhone development apps are often kicked out of the AppStore for using undocumented API calls. I always asked myself how people found out about these methods and what they do.
I know a little about Objective-C and I know you can send any message to any object or you can even check if an object will answer to a methode by calling respondsToSelector. So its seems using undocumented API calls is not the problem but I have no idea how to find them.
BTW I don't want to use undocumented APi functions. I only want to know how oit is done. Can be useful when working with third party frameworks. Or maybe someday people will use frameworks I created.
Check out Class Dump. That will go through frameworks and basically create headers of every method etc that they contain. Very useful for reverse engineering frameworks.
You can also try using the strings utility from the command line. The strings utility will print out all the raw strings contained in a compiled binary file, which can be useful when looking for method names, etc.
Using strings will be a little more difficult/tedious as it can also print a lot of garbage as well as useful stuff, so you need to trawl through it to find the interesting stuff.
Hope this helps.
Related
I have not used libbpf in a while. Now, when I'm looking at the source code and examples, it looks to me that all API now is built around bpf_object while before it was based on program FD (at least on the user-facing level). I believe that fd is now hidden in bpf_object or such.
Of course it keeps backward compatibility and I still can use bpf_prog_load for example, however it looks like the preferred way of writing application code using libbpf is by bpf_object API?
Correct me if I'm wrong. Thanks!
Sounds mostly correct to me.
Low-Level Wrappers
If I remember correctly, the functions returning file descriptors in libbpf, mostly defined in tools/lib/bpf/bpf.c, have always been very low-level. This is the case for bpf_load_program() for example, which is no more than a wrapper around the bpf() system call for loading programs. Such functions are still available, but their use may be tedious for complex use cases.
bpf_prog_load()
Some more advanced functions have long been provided. bpf_prog_load(), that you mention, is one of them, but it returns an error code, not a file descriptor. It is still available as one option to load programs with the library.
bpf_object__*()
Although I don't think there are strict guidelines, I believe it is true that most example now use the bpf_object__*() function. One reason is that they provide a more consistent user experience, being organised around the manipulation of an object file to extract all the relevant bytecode and metadata, and then to load and attach the program. One other reason, I think, is that since this model has been favoured over the last releases, these functions have better support for recent eBPF features and the bpf_object__*() functions offer features that the older bpf_prog_load() workflow does not support.
Libbpf Evolves
At last, it's worth mentioning that libbpf's API is currently undergoing some review and will likely be reworked as part of a major v1.0 release. You may want to have a look at the work document linked in the announcement: Some bpf_object__ functions may be deprecated, and similarly there is currently a proposal to:
Deprecate bpf_prog_load() and bpf_prog_load_xattr() in favor of bpf_object__open_{mem, file}() and bpf_object__load() combo.
There is nothing certain yet regarding the v1.0 release, so I wouldn't worry too much about “deprecation” at the moment - I don't expect all functions to be removed just yet. But that's something you may want to consider when building your next applications.
Ok guys, so im new to iPhone development, so apologies if this is a silly question, but before i actually create my app i want to know if this is possible, and if Apple will reject this.
(Note this is all theoretical)
So i'd have a API (.NET) that runs on a cloud server somewhere and can return HTML/JSON/XML.
I'll have a website that can access this API and allow customers to do some stuff (but this is not important for this question).
I would then like my iPhone app to make a call to this API which would return JSON data. So my iPhone app might make a call to http://myapp/Foos which would return a JSON string of Foo objects. The iPhone app would then parse this JSON and do some funky stuff with it.
So, that's the background, now the questions:
Is this possible? (that is, call an external cloud API over HTTP, parse JSON response?)
What are the chances of Apple rejecting this application (because it would be calling a non-Apple API)
Are there any limitations (security, libraries, etc) on the iPhone/Objective-C/Cocoa that might hinder this solution? In regards to Security - can you freely make a HTTP (or even HTTPS call) from inside an iPhone app, and parse the response? In regards to libraries - is there sufficient support in Objective-C/Cocoa to accomplish this?
On this website, they seem to be doing exactly what im asking.
Thoughts, suggestions, links would be greatly appreciated...
Yes. It is possible. There are quite a few apps that do similar things.
Slim to none. Apple hinders what languages and libraries you can develop in and run on the phone. They won't limit you based on what external data you pull in to your app.
There shouldn't be any worries here either. You shouldn't run in to security concerns and there are plenty of libraries that you should be able to utilize to make your life much easier.
Good luck!
Yes it's certainly possible, and there are json parsers available already. Secondly, based on what you just described, should the application not break any rules outside of the scope of this question, then there is no reason I can see Apple rejecting it (except perhaps content, ie., don't display any porn or the like :)) ... Finally, you haven't properly described your application to fully answer #3, and I don't dare guess at what you meant, since it may be just a waste of your time. Feel free to expand on your #3 in comments, I'll answer there.
Edit: With regard to your edit of #3 above, yeah you won't have an issue here at all either.
I haven't found a comprehensive list of the steps that are required to use a private API from the iPhone Library.
In particular, I would like to know how to get header files, if they are even required, how to get it to compile (when I simply add the header, it complains that the functions aren't defined), and what resources one can use to learn about private APIs (e.g. from other user's experiences, such as http://iphonedevwiki.net/ which has a few).
I've read in other places that people recommend using class-dump to get the headers. Are there any alternative methods? I've noticed that there are some repositories of iPhone Private SDKs, what are the most up to date resources you would recommend?
Most of the previous questions about documentation of private APIs, have all linked to Erica Sadun's website, which doesn't seem to have documentation anymore (all the links on the left are crossed out).
Please save the comments about not using private API's... I know of the biggest risks:
App will get rejected by Apple.
App will break in future updates to the OS.
I'm talking about legitimate uses, such as:
Private application use (e.g. for unit testing, or messing around to see what's possible)
Objective-C has enough information in the compiled binary to almost completely reconstruct the headers. The only things missing are argument names, which can often be approximated from the type or method prototype, and some structure and enum definitions. That is why programs like class-dump are the best way to get the headers. They are comprehensive, including every method whether it was in the real header or not, up to date and do not need to be distributed. The other way to get headers is to look in the public version of the same framework, for example WebKit is only private on the iPhone and is otherwise well documented.
If you are interested in things besides Objective-C you pretty much have to do it the old fashioned way, slogging through disassembly to guess function arguments. Once you get a few symbols, search for them and maybe you will find a header someone else has posted. otool is a good place to start.
If you include the headers, be it for Objective-C or C, you must also include the frameworks or libraries the headers declare methods for, just like any other headers. Most of the Objective-C stuff is in a PrivateFrameworks folder right next to the regular Frameworks folder. You can look in the usr/lib folder to find libraries.
Be aware that there are lots of differences between the simulator and the device, so make sure you build headers from the real device. There are also some of methods that you will not have permission to run as a sandboxed app.
Now that monotouch is banned, I was wondering if there is a way to translate C# (or some other language) into Objective-C? I won't mind using Apple's API as long as I don't have to declare my variables in 3-4 stages (ivar-property-synthesize-dealloc). All I want is a less wordy language, to concentrate on my intent and not on the compiler syntax.
You should pause to see what actually happens instead of assuming Monotouch is banned.
Or, learn Objective-C. It's good for the mind to learn a new language anyway. And the frameworks will make more sense to you.
You could always define your own meta language for objects, write your intended meaning, parse that file, and paste the newly manufactured code into XCode.
And if you're really dead-set against ObjC and XCode, Apple has given you your ultimatum: use it or leave.
If it turns out the way people are suggesting it will turn out, then the answer to your question doesn't actually solve your problem.
The SDK agreement make specific mention to the 'originality' of the Objective-C (and other languages). Translating from C# to Objective-C breaches this requirement that applications be originally written in Objective-C.
Secondly, Monotouch already supports full AOT compilation.
Translating would be against Apples policy because your code must be originally coded in C, Obj -C, C++.
Coming from originally learning Java its really not that hard. Is the declaration of variables in multiple places really your main objection? Its easy to do and gives you tight control over your program. It is also suspected that iPhone OS 4 needs native code to be able to multitask properly. It makes sense as well otherwise they would of amended the current licence agreement if they wanted to stop Adobe.
This is something I wrote last year and may help you with the transition - Objective C by example for a C# developer, assuming Monotouch is actually forbidden.
I've been trying to find a good form of RPC to standardize on, but so far I've ran into a ton of walls and was wondering what the stackoverflow communities view was.
My ideal RPC would provide the following:
Somewhat wide support in other languages, in that people shouldn't have to write a custom stack to use our server
Input validation
Ideally, some way to turn the above input validation into some sort of automated documentation to distribute
Clean and maintainable code
I am a fan of the catalyst framework and would prefer to stick to it, but if there is a clearly better alternative for RPC servers I'd be open to that as well.
So far I have looked at the following:
Catalyst::Controller::SOAP
Doesn't appear to support returning of complex data structures, only string('literals'). I could probably serialize data on top of that, but that seems very hacky. It also lets you return a pre-formed XML object, but I couldn't get that to work and it looks like you'd need to re-create a lot of SOAP data structure for it to work.
I do like the idea of WSDLs, but the complexity of the overall spec also makes me wonder how well support for communicating with other languages will be.
Custom POSTing XML based controller
We tried to roll our own by hand in a similar way to how we've seen two other projects do it recently where there is a dispatch url that you post XML to. This lets you have XSD validation/documentation, but required creating a lot more code than we want to maintain at this point.
Catalyst::Plugin::Server::XMLRPC
Gave a warning about using a deprecated method that will be removed in a future version of Catalyst.
No input validation or doc creation, but otherwise the best I've found
JSONRPC
Looks pretty similar to XMLRPC only the module is actually updated. I'll probably go with this next unless someone suggests something better
There also appears to be two different modules for catalyst that do JSONRPC
I realize that REST isn't pure RPC (only a subset), but...
I would recommend the Catalyst::Controller::REST and Catalyst::Action::REST modules. They're frequently updated and the documentation is fairly good. There is also a good (but rather dated) example of using Catalyst::Controller::Rest in the 2006 Catalyst Advent calendar titled Day 9 - Web Services with Catalyst::Action::REST.
FWIW, Catalyst::Controller::SOAP does support returning complex data. Take a look at the documentation http://search.cpan.org/~druoso/Catalyst-Controller-SOAP-1.23/lib/Catalyst/Controller/SOAP.pm, which will show you that you can use a WSDL to describe your service. Also, see http://daniel.ruoso.com/categoria/perl/soap-today.html.en for a more detailed step-by-step process.