A wrapper around SecCertificate to simplify accessing iOS app certificate properties found in the embedded.mobileprovision file inside the bundle payload. The WrapperImplementation file shows how to extract both the provisioning profile and the details of each certificate. Works on iOS 12, iOS 13, and newer

SecCertificateWrapper.swift

struct SecCertificateWrapper : Comparable {
    
    var data:Data
    var cert:SecCertificate
    
    // Initialize with a data object from the "DeveloperCertificates" 
    // array (see WrapperImplementation.swift)
    init(data:Data) {
        self.cert = SecCertificateCreateWithData(nil, data as CFData)!
        // Use this later for parsing the date details from the cert
        self.data = data
    }
    
    // The certificate name
    var name : String {
        return SecCertificateCopySubjectSummary(cert)! as String
    }

    // Return a tuple with both notValidBefore and notValidAfter dates
    var validDates : (notValidBefore:Date, notValidAfter:Date)? {
        guard let decodedString = String( data: self.data, encoding: .ascii ) else { return nil }
        var foundWWDRCA         = false
        var notValidBeforeDate  = ""
        var notValidAfterDate   = ""
        
        decodedString.enumerateLines { (line, _) in
            
            if foundWWDRCA && (notValidBeforeDate.isEmpty || notValidAfterDate.isEmpty) {
                let certificateData = line.prefix(13)
                if notValidBeforeDate.isEmpty && !certificateData.isEmpty {
                    notValidBeforeDate = String(certificateData)
                } else if notValidAfterDate.isEmpty && !certificateData.isEmpty {
                    notValidAfterDate = String(certificateData)
                }
            }
            
            if line.contains("Apple Worldwide Developer Relations Certification Authority") { foundWWDRCA = true }
        }
        
        return (self.format(notValidBeforeDate), self.format(notValidAfterDate))
    }
    
    // Some convenience properties for access to the notValidBefore and notValidAfter
    // dates in various formats
    var notValidAfterUnixDate : Double {
        return self.validDates?.notValidAfter.timeIntervalSince1970 ?? 0
    }
    
    var notValidAfterUnixDateAsString : String {
        return String(self.notValidAfterUnixDate)
    }

    var notValidBeforeUnixDate : Double {
        return self.validDates?.notValidBefore.timeIntervalSince1970 ?? 0
    }
    
    var notValidBeforeUnixDateAsString : String {
        return String(self.notValidBeforeUnixDate)
    }
    
    // MARK: - Utilities
    // Implement comparable by providing a less than operator
    static func < (lhs: SecCertificateWrapper, rhs: SecCertificateWrapper) -> Bool {
        guard let lhsDate = lhs.validDates?.notValidAfter, let rhsDate = rhs.validDates?.notValidAfter else { return true }
        return lhsDate < rhsDate
    }
    
    // Create a static data formatter just for convenience
    static let certificateDateFormatter : DateFormatter = {
        let formatter = DateFormatter()
        formatter.dateFormat = "yyMMddHHmmssZ"
        return formatter
    }()

    // Provide a format function to help shorten the code where date
    // formatting is performed
    func format(_ date:String) -> Date {
        return SecCertificateWrapper.certificateDateFormatter.date(from: date)!
    }

}

WrapperImplementation.swift

// This implementation file shows how to extract details for the provisioning profile
// but also demonstrates how to grab the certificate info from the DeveloperCertificates
// arry found in the plist

guard let url = Bundle.main.url(forResource: "embedded", withExtension: "mobileprovision"), let data = try? Data(contentsOf: url), let string = String(data: data, encoding: String.Encoding.isoLatin1) else {
    return
} 

// Extract the relevant part of the data string from the start of the opening plist tag
// to the ending one.
let scanner = Scanner(string: string)
if scanner.scanUpTo("<plist", into: nil) {
    var plistString:NSString? = ""
    if scanner.scanUpTo("</plist>", into: &plistString) {
        plistString = (plistString! as String) + "</plist>" as NSString
        
        if let plistData = plistString?.data(using: String.Encoding.isoLatin1.rawValue) {
            // Load the property list into a dictionary
            if let mobileProvision = try? PropertyListSerialization.propertyList(from: plistData, options: [], format: nil) as? [String:Any] {
                
                // Grab all of the profile properties
                let appName            = mobileProvision["AppIDName"] as! String
                let creationDate       = mobileProvision["CreationDate"] as! Date
                let expirationDate     = mobileProvision["ExpirationDate"] as! Date
                let teamName           = mobileProvision["TeamName"] as! String
                let ttl                = mobileProvision["TimeToLive"] as! Int
                let name               = mobileProvision["Name"] as! String
                
                // Grab the nested entitlements dictionary and relevant properties
                let entitlements       = mobileProvision["Entitlements"] as! [String:Any]
                var taskAllow          = entitlements["get-task-allow"] as? Bool ?? false
                let appId              = entitlements["application-identifier"] as! String
                let teamId             = entitlements["com.apple.developer.team-identifier"] as! String
                
                // Iterate through the DeveloperCertificates array sorted by notValidAfter date
                // (see Comparable implementation in the SecCertificateWrapper.swift file) and 
                // create and print SecCertificateWrapper objects
                if let certData = mobileProvision["DeveloperCertificates"] as? [Data] {
                    for cert in certData.map( { SecCertificateWrapper(data: $0) }).sorted() {
                        debugPrint("Name: \(cert.name), Not Valid After Date: \(cert.notValidAfterUnixDateAsString)")

                    }
                }
            }
        }
    }
}