March 2013 - Darwin-dev - lists.apple.com

Solved, bug in DSObjCWrappers in 64-bit executables make calls fail with -14079
by Sidney San Martín 24 Mar '13

24 Mar '13

I just spent some time debugging a mysterious problem: DSObjCWrappers' -[DSoUser setPassword:] method reliably threw an exception containing the status code -14079 ("Specified buffer format is invalid"). It also affected other methods. I'm sharing my solution with the list mostly for archive purposes in case someone else runs into the same bug. It turns out that only 64-bit executables are affected, dscl and the like are 32-bit on 10.5 (the final operating system where you should be using DSObjCWrappers ;) ). There's a bug in -[DSoNode authenticateWithBufferItems:authType:authOnly:]. It (correctly, AFAICT) allocates a buffer with four bytes reserved for the length of each entry but uses a size_t to represent the length to be written into the buffer. size_t is eight bytes on 64-bit machines so the buffer is corrupted. The fix is to make ulCurrentLength in the above-named method and its brother a uint32_t. Here's a diff against <http://opensource.apple.com/source/DSTools/DSTools-112.1/DSObjCWrappers/DSo…>: --- a/DSoNode.m 2006-04-05 18:11:40.000000000 -0400 +++ b/DSoNode.m 2013-03-24 00:50:02.000000000 -0400 @@ -468,7 +468,7 @@ authOnly: (BOOL)inAuthOnly { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; - size_t ulCurrentLength = 0; + uint32_t ulCurrentLength = 0; DSoBuffer *dbAuth = nil; DSoBuffer *dbStep = [[DSoBuffer alloc] initWithDir:mDirectory bufferSize:2048] ; DSoDataNode *dnAuthType = [(DSoDataNode*)[DSoDataNode alloc] initWithDir:mDirectory cString:inAuthType] ; @@ -523,7 +523,7 @@ responseBufferItems: (NSArray**)outBufferItems { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; - size_t ulCurrentLength = 0; + uint32_t ulCurrentLength = 0; DSoBuffer *dbAuth = nil; DSoBuffer *dbStep = [[DSoBuffer alloc] initWithDir:mDirectory bufferSize:2048] ; DSoDataNode *dnAuthType = [(DSoDataNode*)[DSoDataNode alloc] initWithDir:mDirectory cString:inAuthType] ; I patched over it by overloading -[DSoNode authenticateWithBufferItems:authType:authOnly:] with a fixed version in a DSoNode category since that's the only one I use. If anyone thinks I missed the real problem (e.g. Directory Services isn't 64-bit-safe and will break horribly in other ways), lemme know. Sidney _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.ap… This email sent to site_archiver(a)lists.apple.com

1 0

Re: Launchd daemon
by Sidney San Martín 24 Mar '13

24 Mar '13

I just joined and saw this thread, might be able to fill in a couple of gaps (though as a result I don't have your email — hope you see this response). > - Communication will most probably be done with UNIX Domain Sockets. > - I will need to configure the plist, which is very well explained (in an other documentation). > > I have also taken a look at SampleD. > - It gets their socket from launch_data_dict_lookup(sockets_dict, "MyListenerSocket"); > Do I need to obtain a control socket from launchd or can I register it myself using ctl_register()? UNIX domain sockets work great. You can even have launchd create the server end of it for you and grab it at checkin time. Here's some code from a project of mine that might help with this. Does it cover what you meant by "obtaining a control socket from launchd"? It also grabs a timeout — my daemon exits if it's been idle for a while, yours may not need to. (Replace log() with calls to asl_log() or your own helpful logging function): int launchdSocketFd = 0; int launchdTimeout = 0; launch_data_t checkin_request; launch_data_t checkin_response; // Check in with launchd. Even if we weren't launched by launchd these first two calls should succeed if ((checkin_request = launch_data_new_string(LAUNCH_KEY_CHECKIN)) == NULL) { log(ASL_LEVEL_ERR, @"launch_data_new_string(\"" LAUNCH_KEY_CHECKIN "\") Unable to create string."); exit(EXIT_FAILURE); } if ((checkin_response = launch_msg(checkin_request)) == NULL) { log(ASL_LEVEL_ERR, @"launch_msg(\"" LAUNCH_KEY_CHECKIN "\") IPC failure: %s", strerror(errno)); exit(EXIT_FAILURE); } // If we were started by launchd, get the file descriptor of the socket launchd opened for us if (LAUNCH_DATA_DICTIONARY == launch_data_get_type(checkin_response)) { launch_data_t sockets_dict = launch_data_dict_lookup(checkin_response, LAUNCH_JOBKEY_SOCKETS); size_t socketCount; if (sockets_dict && (socketCount = launch_data_dict_get_count(sockets_dict))) { if(socketCount > 1){ log(ASL_LEVEL_WARNING, @"Launchd gave us extra sockets, ignoring them"); } launch_data_t listening_fd_array = launch_data_dict_lookup(sockets_dict, "sockserverSocket"); if (listening_fd_array && launch_data_array_get_count(listening_fd_array)) { launchdSocketFd = launch_data_get_fd(launch_data_array_get_index(listening_fd_array, 0)); } } launch_data_t timeout = launch_data_dict_lookup(checkin_response, LAUNCH_JOBKEY_TIMEOUT); if(timeout){ launchdTimeout = launch_data_get_integer(timeout); } if(!launchdSocketFd){ log(ASL_LEVEL_ERR, @"Missing a socket to answer requests!"); exit(EXIT_FAILURE); } } else { errno = launch_data_get_errno(checkin_response); log(ASL_LEVEL_ERR, @"Couldn't check in with launchd: %m"); } launch_data_free(checkin_request); launch_data_free(checkin_response); > - How to set up my project to use Objective-C for my daemon. > - What does my Objective-C entry point look like (int main(…) ?) > - How do I handle SIGKILL > - If I can't use a for/while/etc. loop, how do I prevent my daemon from exiting once the main function returns? > - Do I need to obtain a control socket from launchd or can I register it myself using ctl_register()? > >> Daemos are by definition command line. > Do you know how to select objective-C as developing language? Just create a Foundation command line tool! A launchd daemon can be *any* executable (though it shouldn't use AppKit), it isn't special. Your main()'ll probably look like this: int main () { [MyBigFancyController new]; [[NSRunLoop currentRunLoop] run]; return 0; } Do whatever initialization you want from main() — it can be inline, a call to a C function, or a call to one or more ObjC methods, as above. It can start listening to the domain socket you got from launchd — you're welcome to wrap it in an NSFileHandle and -acceptConnectionInBackgroundAndNotify — or open files, connect to other programs, whatever. The NSRunLoop is your infinite loop, the same one used by Cocoa apps, and the call to -run won't return while the it has input sources. Any evented ObjC call (NSTimer, -performSelector:afterDelay:, notification center, NSURLConnection, -acceptConnectionInBackgroundAndNotify, etc.) that can call you back at a later time registers itself with the run loop and counts as an input source, so don't worry about it. _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.ap… This email sent to site_archiver(a)lists.apple.com

1 0

Re: Launchd daemon
by Daniel A. Steffen 18 Mar '13

18 Mar '13

_______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.ap… This email sent to site_archiver(a)lists.apple.com

1 0

Re: Launchd daemon
by Steve Sisak 18 Mar '13

18 Mar '13

_______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.ap… This email sent to site_archiver(a)lists.apple.com

1 0

Re: Launchd daemon
by Jens Alfke 18 Mar '13

18 Mar '13

_______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.ap… This email sent to site_archiver(a)lists.apple.com

1 0

Re: Launchd daemon
by Tilghman Lesher 18 Mar '13

18 Mar '13

On Mon, Mar 18, 2013 at 10:36 AM, Erwin Namal <erwin.namal(a)gmail.com> wrote: > Sorry. I meant How do I handle SIGTERM? > > From what I have read, I shall not call fork and exec from a daemon. But can > I use GCD? I mean, can I have a serial dispatch queue in a daemon, or use > one of those provided by the system? Look at sigaction() or signal(), which allow you to specify a routine to run when you receive that signal. Note that whichever one you choose to use is generally mutually exclusive with the other, as you can only install a single routine per signal type. _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.ap… This email sent to site_archiver(a)lists.apple.com

1 0

Re: Launchd daemon
by Erwin Namal 18 Mar '13

18 Mar '13

_______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.ap… This email sent to site_archiver(a)lists.apple.com

1 0

Re: Launchd daemon
by Tilghman Lesher 18 Mar '13

18 Mar '13

On Mon, Mar 18, 2013 at 6:47 AM, Erwin Namal <erwin.namal(a)gmail.com> wrote: > Have you read this? > > <http://developer.apple.com/library/mac/#documentation/MacOSX/Conceptual/BPS…> > > > Yes, this is where they explain all about the plists. It is very well > documented, but doesn't answer my questions which are: > - How to set up my project to use Objective-C for my daemon. > - What does my Objective-C entry point look like (int main(…) ?) Basically, structure it the same wait that you thought, but instead of using a sleep(), use kqueue() to receive events from the kernel. When there are no events, your process stays suspended. > - How do I handle SIGKILL You cannot. SIGKILL, by definition, is not handle-able. If sent to your process, your process will never receive it, but it will stop running and be removed from memory. Therefore, if you have any resources that you need to shut down or close in a special way, it's critical that you do so in the timeframe allotted between the TERM and the KILL. > - If I can't use a for/while/etc. loop, how do I prevent my daemon from > exiting once the main function returns? Set up kqueue() prior to your loop, then call it at the top of your loop and use a switch statement (or multiple if/else conditions) to handle each type of event coming back from kqueue(). After you've handled one event, you can loop back to call kqueue() again, for the next event. _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.ap… This email sent to site_archiver(a)lists.apple.com

1 0

Re: Launchd daemon
by Erwin Namal 18 Mar '13

18 Mar '13

_______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.ap… This email sent to site_archiver(a)lists.apple.com

1 0

Re: Launchd daemon
by Rustam Muginov 18 Mar '13

18 Mar '13

Seems you might want to re-read this technote: http://developer.apple.com/library/mac/#technotes/tn2083/_index.html -- Sincerely, Rustam Muginov On Mar 17, 2013, at 1:59 PM, Erwin Namal wrote: > Hello, > > I have a large experience in developing cocoa applications, but none with launchd daemons. I would like to develop a system daemon running from start to shutdown and I know, from the documentation below [1] that there are a few requirements. > I have tried to compile the sampleD daemon, but it is way outdated and I can't make it work… despite setting it to 64bits and mountain lion. > So I have a few questions: > > 1. Which language can I use for my daemon? Obj-C? C? C++? > 2. Is there a specific template to use? I saw an XPC service template in Xcode but that's all. > 3. I know I need to handle SIGTERM, but I don't know how. Are there any other requirements? > 4. I think that once launched, the daemon must have an infinite loop, right? ShouldI put a sleep() call inside? If yes, for how long? > > These are pretty basic questions. I will gladly take any help, any sample code or any link towards documentations… in short amything is good to help me start. > > Thanks, > Erwin > > [1] https://developer.apple.com/library/mac/#documentation/MacOSX/Conceptual/BP… > _______________________________________________ > Do not post admin requests to the list. They will be ignored. > Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) > Help/Unsubscribe/Update your Subscription: > https://lists.apple.com/mailman/options/darwin-dev/rmuginov%40gmail.com > > This email sent to rmuginov(a)gmail.com _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.ap… This email sent to site_archiver(a)lists.apple.com

1 0