How to use the command 'codesign' (with examples)

The ‘codesign’ command is used to create and manipulate code signatures for macOS applications. Code signing is an important security measure that ensures the authenticity and integrity of the code in an application. By signing an application with a certificate, developers can indicate that their code has not been tampered with and has been verified by a trusted source.

Use case 1: Sign an application with a certificate

Code:

codesign --sign "My Company Name" path/to/application_file.app

Motivation:

Signing an application with a certificate is necessary for distributing it securely on macOS. It provides a way to prove that the code has not been altered or maliciously modified since it was signed. This is particularly important when distributing applications through the Mac App Store or outside of the App Store.

Explanation:

• --sign "My Company Name": This argument specifies the name of the signing certificate to be used. In this example, “My Company Name” is used as a placeholder for the actual name of the certificate. You need to provide the name of the signing certificate you have configured on your system.

• path/to/application_file.app: This is the path to the application file that you want to sign. Replace “path/to/application_file.app” with the actual path to the application file.

Example output:

When the command is successfully executed, it will sign the application with the specified certificate. If the signing is successful, no explicit output will be shown. To verify the signing, you can use the ‘codesign –verify’ command.

Use case 2: Verify the certificate of an application

Code:

codesign --verify path/to/application_file.app

Motivation:

Verifying the certificate of an application is essential for ensuring that the application has been signed by a trusted source and has not been modified since it was signed. It provides reassurance to the user that the application is safe to use and has not been tampered with.

Explanation:

• --verify: This argument instructs the ‘codesign’ command to verify the code signature of the specified application.

• path/to/application_file.app: This is the path to the application file that you want to verify. Replace “path/to/application_file.app” with the actual path to the application file.

Example output:

When the command is executed, it will verify the signature of the specified application. The output will indicate whether the code signature is valid and has not been tampered with. If the verification is successful, the command will output “path/to/application_file.app: valid on disk”.

Conclusion:

The ‘codesign’ command is a powerful tool for creating and managing code signatures for macOS applications. By signing an application with a certificate, developers can ensure the integrity and authenticity of their code. Verifying the signature of an application helps users determine if the application has been signed by a trusted source and has not been modified. Using the ‘codesign’ command allows for a secure and reliable distribution of applications on macOS.