You can now manage code signing for iOS and macOS builds through the CircleCI API.
Upload your Apple signing certificate (.p12) and provisioning profiles, create a signing bundle, then reference it by name in your macos executor using the new code_signing key and the install_signing_bundle step. CircleCI installs the certificate and profiles into a temporary keychain on the runner at build time and removes them when the job finishes.
This is a native alternative to managing your own certificate store with Fastlane Match.
For setup steps, see Set up code signing for iOS and macOS projects.