# macOS XPC Authorization
☁️ HackTricks Cloud ☁️ -🐦 Twitter 🐦 - 🎙️ Twitch 🎙️ - 🎥 Youtube 🎥 * Do you work in a **cybersecurity company**? Do you want to see your **company advertised in HackTricks**? or do you want to have access to the **latest version of the PEASS or download HackTricks in PDF**? Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)! * Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family) * Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com) * **Join the** [**💬**](https://emojipedia.org/speech-balloon/) [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** me on **Twitter** [**🐦**](https://github.com/carlospolop/hacktricks/tree/7af18b62b3bdc423e11444677a6a73d4043511e9/\[https:/emojipedia.org/bird/README.md)[**@carlospolopm**](https://twitter.com/hacktricks\_live)**.** * **Share your hacking tricks by submitting PRs to the** [**hacktricks repo**](https://github.com/carlospolop/hacktricks) **and** [**hacktricks-cloud repo**](https://github.com/carlospolop/hacktricks-cloud).
## XPC Authorization Apple also proposes another way to authenticate if the connecting process has **permissions to call the an exposed XPC method**. When an application needs to **execute actions as a privileged user**, instead of running the app as a privileged user it usually installs as root a HelperTool as an XPC service that could be called from the app to perform those actions. However, the app calling the service should have enough authorization. ### ShuoldAcceptNewConnection always YES An example could be found in [EvenBetterAuthorizationSample](https://github.com/brenwell/EvenBetterAuthorizationSample). In `App/AppDelegate.m` it tries to **connect** to the **HelperTool**. And in `HelperTool/HelperTool.m` the function **`shouldAcceptNewConnection`** **won't check** any of the requirements indicated previously. It'll always return YES: ```objectivec - (BOOL)listener:(NSXPCListener *)listener shouldAcceptNewConnection:(NSXPCConnection *)newConnection // Called by our XPC listener when a new connection comes in. We configure the connection // with our protocol and ourselves as the main object. { assert(listener == self.listener); #pragma unused(listener) assert(newConnection != nil); newConnection.exportedInterface = [NSXPCInterface interfaceWithProtocol:@protocol(HelperToolProtocol)]; newConnection.exportedObject = self; [newConnection resume]; return YES; } ``` For more information about how to properly configure this check: {% content-ref url="macos-xpc-connecting-process-check.md" %} [macos-xpc-connecting-process-check.md](macos-xpc-connecting-process-check.md) {% endcontent-ref %} ### Application rights However, there is some **authorization going on when a method from the HelperTool is called**. The function **`applicationDidFinishLaunching`** from `App/AppDelegate.m` will create an empty authorization reference after the app has started. This should always work.\ Then, it will try to **add some rights** to that authorization reference calling `setupAuthorizationRights`: ```objectivec - (void)applicationDidFinishLaunching:(NSNotification *)note { [...] err = AuthorizationCreate(NULL, NULL, 0, &self->_authRef); if (err == errAuthorizationSuccess) { err = AuthorizationMakeExternalForm(self->_authRef, &extForm); } if (err == errAuthorizationSuccess) { self.authorization = [[NSData alloc] initWithBytes:&extForm length:sizeof(extForm)]; } assert(err == errAuthorizationSuccess); // If we successfully connected to Authorization Services, add definitions for our default // rights (unless they're already in the database). if (self->_authRef) { [Common setupAuthorizationRights:self->_authRef]; } [self.window makeKeyAndOrderFront:self]; } ``` The function `setupAuthorizationRights` from `Common/Common.m` will store in the auth database `/var/db/auth.db` the rights of the application. Note how it will only add the rights that aren't yet in the database: ```objectivec + (void)setupAuthorizationRights:(AuthorizationRef)authRef // See comment in header. { assert(authRef != NULL); [Common enumerateRightsUsingBlock:^(NSString * authRightName, id authRightDefault, NSString * authRightDesc) { OSStatus blockErr; // First get the right. If we get back errAuthorizationDenied that means there's // no current definition, so we add our default one. blockErr = AuthorizationRightGet([authRightName UTF8String], NULL); if (blockErr == errAuthorizationDenied) { blockErr = AuthorizationRightSet( authRef, // authRef [authRightName UTF8String], // rightName (__bridge CFTypeRef) authRightDefault, // rightDefinition (__bridge CFStringRef) authRightDesc, // descriptionKey NULL, // bundle (NULL implies main bundle) CFSTR("Common") // localeTableName ); assert(blockErr == errAuthorizationSuccess); } else { // A right already exists (err == noErr) or any other error occurs, we // assume that it has been set up in advance by the system administrator or // this is the second time we've run. Either way, there's nothing more for // us to do. } }]; } ``` The function `enumerateRightsUsingBlock` is the one used to get applications permissions, which are defined in `commandInfo`: ```objectivec static NSString * kCommandKeyAuthRightName = @"authRightName"; static NSString * kCommandKeyAuthRightDefault = @"authRightDefault"; static NSString * kCommandKeyAuthRightDesc = @"authRightDescription"; + (NSDictionary *)commandInfo { static dispatch_once_t sOnceToken; static NSDictionary * sCommandInfo; dispatch_once(&sOnceToken, ^{ sCommandInfo = @{ NSStringFromSelector(@selector(readLicenseKeyAuthorization:withReply:)) : @{ kCommandKeyAuthRightName : @"com.example.apple-samplecode.EBAS.readLicenseKey", kCommandKeyAuthRightDefault : @kAuthorizationRuleClassAllow, kCommandKeyAuthRightDesc : NSLocalizedString( @"EBAS is trying to read its license key.", @"prompt shown when user is required to authorize to read the license key" ) }, NSStringFromSelector(@selector(writeLicenseKey:authorization:withReply:)) : @{ kCommandKeyAuthRightName : @"com.example.apple-samplecode.EBAS.writeLicenseKey", kCommandKeyAuthRightDefault : @kAuthorizationRuleAuthenticateAsAdmin, kCommandKeyAuthRightDesc : NSLocalizedString( @"EBAS is trying to write its license key.", @"prompt shown when user is required to authorize to write the license key" ) }, NSStringFromSelector(@selector(bindToLowNumberPortAuthorization:withReply:)) : @{ kCommandKeyAuthRightName : @"com.example.apple-samplecode.EBAS.startWebService", kCommandKeyAuthRightDefault : @kAuthorizationRuleClassAllow, kCommandKeyAuthRightDesc : NSLocalizedString( @"EBAS is trying to start its web service.", @"prompt shown when user is required to authorize to start the web service" ) } }; }); return sCommandInfo; } + (NSString *)authorizationRightForCommand:(SEL)command // See comment in header. { return [self commandInfo][NSStringFromSelector(command)][kCommandKeyAuthRightName]; } + (void)enumerateRightsUsingBlock:(void (^)(NSString * authRightName, id authRightDefault, NSString * authRightDesc))block // Calls the supplied block with information about each known authorization right.. { [self.commandInfo enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) { #pragma unused(key) #pragma unused(stop) NSDictionary * commandDict; NSString * authRightName; id authRightDefault; NSString * authRightDesc; // If any of the following asserts fire it's likely that you've got a bug // in sCommandInfo. commandDict = (NSDictionary *) obj; assert([commandDict isKindOfClass:[NSDictionary class]]); authRightName = [commandDict objectForKey:kCommandKeyAuthRightName]; assert([authRightName isKindOfClass:[NSString class]]); authRightDefault = [commandDict objectForKey:kCommandKeyAuthRightDefault]; assert(authRightDefault != nil); authRightDesc = [commandDict objectForKey:kCommandKeyAuthRightDesc]; assert([authRightDesc isKindOfClass:[NSString class]]); block(authRightName, authRightDefault, authRightDesc); }]; } ``` This means that at the end of this process, the permissions declared inside `commandInfo` will be stored in `/var/db/auth.db`. Note how there you can find for **each method** that will r**equire authentication**, **permission name** and the **`kCommandKeyAuthRightDefault`**. The later one **indicates who can get this right**. There are different scopes to indicate who can access a right. Some of them are defined in [AuthorizationDB.h](https://github.com/aosm/Security/blob/master/Security/libsecurity\_authorization/lib/AuthorizationDB.h) (you can find [all of them in here](https://www.dssw.co.uk/reference/authorization-rights/)), but as summary:
NameValueDescription
kAuthorizationRuleClassAllowallowAnyone
kAuthorizationRuleClassDenydenyNobody
kAuthorizationRuleIsAdminis-adminCurrent user needs to be an admin (inside admin group)
kAuthorizationRuleAuthenticateAsSessionUserauthenticate-session-ownerAsk user to authenticate.
kAuthorizationRuleAuthenticateAsAdminauthenticate-adminAsk user to authenticate. He needs to be an admin (inside admin group)
kAuthorizationRightRuleruleSpecify rules
kAuthorizationCommentcommentSpecify some extra comments on the right
### Rights Verification In `HelperTool/HelperTool.m` the function **`readLicenseKeyAuthorization`** checks if the caller is authorized to **execute such method** calling the function **`checkAuthorization`**. This function will check the **authData** sent by the calling process has a **correct format** and then will check **what is needed to get the right** to call the specific method. If all goes good the **returned `error` will be `nil`**: ```objectivec - (NSError *)checkAuthorization:(NSData *)authData command:(SEL)command { [...] // First check that authData looks reasonable. error = nil; if ( (authData == nil) || ([authData length] != sizeof(AuthorizationExternalForm)) ) { error = [NSError errorWithDomain:NSOSStatusErrorDomain code:paramErr userInfo:nil]; } // Create an authorization ref from that the external form data contained within. if (error == nil) { err = AuthorizationCreateFromExternalForm([authData bytes], &authRef); // Authorize the right associated with the command. if (err == errAuthorizationSuccess) { AuthorizationItem oneRight = { NULL, 0, NULL, 0 }; AuthorizationRights rights = { 1, &oneRight }; oneRight.name = [[Common authorizationRightForCommand:command] UTF8String]; assert(oneRight.name != NULL); err = AuthorizationCopyRights( authRef, &rights, NULL, kAuthorizationFlagExtendRights | kAuthorizationFlagInteractionAllowed, NULL ); } if (err != errAuthorizationSuccess) { error = [NSError errorWithDomain:NSOSStatusErrorDomain code:err userInfo:nil]; } } if (authRef != NULL) { junk = AuthorizationFree(authRef, 0); assert(junk == errAuthorizationSuccess); } return error; } ``` Note that to **check the requirements to get the right** to call that method the function `authorizationRightForCommand` will just check the previously comment object **`commandInfo`**. Then, it will call **`AuthorizationCopyRights`** to check **if it has the rights** to call the function (note that the flags allow interaction with the user). In this case, to call the function `readLicenseKeyAuthorization` the `kCommandKeyAuthRightDefault` is defined to `@kAuthorizationRuleClassAllow`. So **anyone can call it**. ### DB Information It was mentioned that this information is stored in `/var/db/auth.db`. You can list all the stored rules with: ```sql sudo sqlite3 /var/db/auth.db SELECT name FROM rules; SELECT name FROM rules WHERE name LIKE '%safari%'; ``` Then, you can read who can access the right with: ```bash security authorizationdb read com.apple.safaridriver.allow ```
☁️ HackTricks Cloud ☁️ -🐦 Twitter 🐦 - 🎙️ Twitch 🎙️ - 🎥 Youtube 🎥 * Do you work in a **cybersecurity company**? Do you want to see your **company advertised in HackTricks**? or do you want to have access to the **latest version of the PEASS or download HackTricks in PDF**? Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)! * Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family) * Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com) * **Join the** [**💬**](https://emojipedia.org/speech-balloon/) [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** me on **Twitter** [**🐦**](https://github.com/carlospolop/hacktricks/tree/7af18b62b3bdc423e11444677a6a73d4043511e9/\[https:/emojipedia.org/bird/README.md)[**@carlospolopm**](https://twitter.com/hacktricks\_live)**.** * **Share your hacking tricks by submitting PRs to the** [**hacktricks repo**](https://github.com/carlospolop/hacktricks) **and** [**hacktricks-cloud repo**](https://github.com/carlospolop/hacktricks-cloud).