Is mac gatekeeper only for downloaded apps

As with signed code, when you create a flat-file installation package, any modification after signing invalidates the signature. Beginning in macOS This is the recommended alternative to the deprecated xip file format, which is a signed archive you create with the xip command line utility. Xcode does not handle signing disk images.

Instead, use the command line codesign tool to do this manually:. When you sign your app with a Developer ID and distribute it using a disk image, it is possible to package additional unsigned code, such as dynamic libraries or scripts, together with the signed app bundle on the same disk image.

If your app loads this extra content at runtime using a file system path relative to its own bundle, you have introduced a security risk.

This is known as the repackaging problem because a bad actor can repackage your app bundle with a different, potentially malicious version of the external resources, and distribute the altered disk image as if it came from you. To combat this problem, beginning in macOS The system copies the app to a random location in the file system before executing it, invalidating any relative paths that the app uses to access unprotected content outside its own app bundle.

You can bypass path randomization by code signing your disk image before you distribute it. When launching an app from a code-signed disk image, Gatekeeper disables path randomization because all the contents of the disk image are covered by a code signature.

Whether you code sign manually or Xcode does it for you, when you want to test the integrity of signed code or evaluate the way in which the system is going to treat signed code, you use the codesign and spctl command line tools.

You use the codesign command to interrogate an app or other signed entity about its signature. To verify the signature on a signed binary, use the -v option with no other options:. It does not by default check that the code satisfies any requirements except its own designated requirement. To check a particular requirement, use the -R option.

Add one or more additional -v options to get details on the validation process. Here is a longer example that demonstrates these concepts:. If you pass a number rather than a path to the verify option, codesign takes the number to be the process ID pid of a running process, and performs dynamic validation instead.

When verifying signatures, add --deep to ensure recursive validation of nested code. Without --deep , validation will be shallow. Note that Gatekeeper always performs --deep style validation, as described in Checking Gatekeeper Conformance. To get information about a code signature without actually verifying it , use the -d option.

After you have produced your final deliverable, but before you ship it, you can use the spctl 8 tool to test your code signatures against various system policies that the user may set. Because the tool evaluates against the policies on the local machine, the outcome is affected by the settings in the Security preferences pane, and can further be modified by parental controls, remote management, and so on. Conversely, changes made with spctl such as adding or disabling rules affect future Gatekeeper judgments directly.

If your application or package signature is valid, these tools exit silently with an exit status of 0. If the signature is invalid, these tools print an error message and exit with a nonzero exit status. For more detailed information about why the assessment failed, you can add the --verbose flag.

For example:. To see everything the system has to say about an assessment, pass the --raw option. With this flag, the spctl tool prints a detailed assessment as a property list.

The --label is an optional tag that you can add to your own rules. This tag allows you to remove the rule easily by typing:. Note that this removes all rules that match the label, which means that it is a handy way to clean up after testing. You can also temporarily suspend your rules by typing:. Notice that the list above includes a number of predefined rules that describe the handling of certain classes of code. For example, rule 5 captures all applications signed by a Developer ID.

You can disable those applications by typing:. This command tells the system to no longer allow execution of any Developer ID-signed applications that the user has not previously run. Each rule in the list has a unique number that can be used to address it.

For example, if you type:. Notice that there are separate rules for execution 5 and installation 6 , and you can enable and disable them separately. For example, to enable installation of new applications signed with a Developer ID, you can type:. Finally, spctl allows you to enable or disable the security assessment policy subsystem. Gatekeeper is a configurable system facility that examines files that you download to your Mac, for example from a website or in an email attachment.

It applies rules to decide whether to allow or reject an attempt to open an item for the first time on a given system. By default, Gatekeeper only allows apps that have an intact signature, and that are downloaded from the Mac App Store or are signed with a Developer ID.

Beginning with macOS If an app uses rpath or an absolute path to link to a dynamic library outside of the app, Gatekeeper rejects the app. This restriction applies even if the path does not exist which normally causes the dynamic linker to fall back to a library inside the bundle. The error will appear in the system log, with a message like the following for an app MyApp.

As with other Gatekeeper functions, this check is performed the first time the app is run. It does not apply to libraries that the app loads itself using the dlopen function, although those libraries are still potentially subject to library validation, as described in Using Library Validation. This should not affect anyone using normal build tools.

Gatekeeper also rejects apps containing symbolic links that:. To get a sense of whether your app conforms to Gatekeeper policies when you distribute with Developer ID, you can use the following codesign command to mimic what Gatekeeper does:.

Alternately, the spctl utility is actually a command-line interface to the same security assessment policy subsystem that Gatekeeper uses. Run spctl on your app like this:. If you get any result other than accepted , your app is not compatible with Gatekeeper. The codesign and spctl tools give a good sense of how Gatekeeper will respond to your app, but they are not exhaustive. For example, they do not test for the condition that libraries be loaded from inside the bundle or from one of the standard system locations.

Therefore, it is best to actually invoke Gatekeeper as a final test before shipping. To do this:. Download your app from its website, mail it to yourself, or send it to yourself using AirDrop or Message. This quarantines the app. This is necessary to trigger the Gatekeeper check as Gatekeeper only checks quarantined files the first time they're opened.

If you see the dialog with a message that the app you are trying to open is from the Internet, and providing an Open button, the test succeeded. If you're told that only apps from the Mac App Store or registered developers can be installed, your app isn't Developer ID-signed. It may also be that the system doesn't think your bundle is an app bundle because its Info.

When you build and code sign using macOS There is nothing you need to do to adopt this behavior. At the same time, to maintain backward compatibility, the system includes a legacy code signature alongside the modern one, in a way that works transparently with older systems. Similarly, during code signature evaluation on macOS As with signing, there is nothing you need to do to adopt the improved hashing during code signature evaluation.

Together, these are referred to as hash agility. Compression, encoding, and encrypting the code are all fine because decompression, decoding, and decryption reverse these processes exactly. You can even use binary patching, because that process updates both the code and the embedded signature simultaneously.

You can use any installer you like, as long as it doesn't write anything into the product as it installs it. Drag-installs are fine as well. Gatekeeper on your Mac ensures that all apps from the internet have already been checked by Apple for known malicious code — before you run them the first time. Apps need your permission to access files in your Documents, Downloads, and Desktop folders as well as in iCloud Drive and external volumes.

With FileVault 2, your data is safe and secure — even if your Mac falls into the wrong hands. Mac computers built on the Apple M1 chip take data protection even further by using dedicated hardware to protect your login password and enabling file-level encryption, which developers can take advantage of — just as on iPhone.

A new weekly Privacy Report on your start page shows how Safari protects you as you browse over time. Or click the Privacy Report button in your Safari toolbar for an instant snapshot of the cross-site trackers Safari is actively preventing on that web page.

Safari uses iCloud Keychain to securely store your passwords across all your devices. If it ever detects a security concern, Password Monitoring will alert you. These devices then relay the detected location of your Mac to iCloud so you can locate it. And it all happens silently using tiny bits of data that piggyback on existing network traffic. So if your Mac is ever misplaced or lost, the only person who can erase and reactivate it is you.

Learn more about Apple Platform Security. Learn more about iCloud Security. Apple makes no representations regarding third-party website accuracy or reliability. Contact the vendor for additional information. Safely open apps on your Mac macOS includes a technology called Gatekeeper, that's designed to ensure that only trusted software runs on your Mac.

View the app security settings on your Mac By default, the security and privacy preferences of your Mac are set to allow apps from the App Store and identified developers. If macOS detects a malicious app If macOS detects that software has malicious content or its authorization has been revoked for any reason, your Mac will notify you that the app will damage your computer.

Privacy protections macOS has been designed to keep users and their data safe while respecting their privacy. Published Date: April 30, Yes No. Character limit: Maximum character limit is Start a discussion in Apple Support Communities.

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