I'm reading about some good practices for developing iOS apps and looking at the possibility of monitoring logs of an iOS app installed from App Store using Console.app. So, I was testing here, but I noticed that print statements didn't show up in Console.app, only NSLog does. My question is: is there any way that is possible to see logs that are made with print commands within iOS apps installed on a device? With Frida, Console.app or any other means?
If there is no other method, does it mean that print commands are more secure than NSLog? This seems very counterintuitive to me 🤔
print statement in iOS apps are not logged to one the [persistent] logging systems on iOS, therefore you can not access the output of an app via print statements if they had occur in the past.
By default you can only seem the output of print commands in XCode output panel. However the print commands themselves are always included in the debug and release builds and are therefore executed. Just the output of the print statements is discarded if no XCode is connected to retrieve it.
I tested this by building the following SwiftUI test app (see the end of this answer), made sure the Archive profile is set to RELEASE and the archived the project, to build an IPA file.
The IPA file was then analyzed in IdaPro to see the actual ARM assembler code.
And in all tests using different options (e.g. "Rebuild from Bitcode" (de)activated) the code was always there.
Therefore if you attach Frida to an app you can e.g. hook the print method print(_:separator:terminator:) to retrieve all output that would otherwise be discarded.
struct ContentView: View {
#State var number : Int = 1
var body: some View {
VStack {
Button(" Print ") {
print("print test abcdefgh number %d", number)
}.padding()
Button(" os_log ") {
os_log("os_log test abcdefgh number %d", number)
}.padding()
Button("randomize") {
self.number = Int.random(in: 1...11111)
}.padding()
}
}
}
If, and only if, you want to use print and printf in your app to go to a file or whatever file descriptor:
import SwiftUI
import Darwin
import os.log
extension OSLog {
private static var subsystem = Bundle.main.bundleIdentifier!
static let `default` = OSLog(subsystem: subsystem, category: "default")
}
extension TestApp {
func subscribeFileToStderrAndStdoutIfNotAttachedToDebugger() {
if isatty(STDERR_FILENO) != 1 {
let documentsUrl = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
let logfileUrl = documentsUrl.appendingPathComponent("out.log")
logfileUrl.withUnsafeFileSystemRepresentation { path in
guard let path = path else {
return
}
print("redirect stdout and stderr to: \(String(cString: path))")
let file = fopen(path, "a")
assert(file != nil, String(cString: strerror(errno)))
let fd = fileno(file)
assert(fd >= 0, String(cString: strerror(errno)))
let result1 = dup2(fd, STDERR_FILENO)
assert(result1 >= 0, String(cString: strerror(errno)))
let result2 = dup2(fd, STDOUT_FILENO)
assert(result2 >= 0, String(cString: strerror(errno)))
}
}
}
}
class AppDelegate: NSObject, UIApplicationDelegate {
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey : Any]? = nil) -> Bool {
subscribeFileToStderrAndStdoutIfNotAttachedToDebugger()
return true
}
}
I'm getting a deprecation warning in iOS 15 SDK, but the suggested replacement is not a one-to-one replacement. This is what I have for evaluating the SSL trust chain:
func valid(_ trust: SecTrust, forHost host: String) -> Bool {
guard valid(trust, for: [SecPolicyCreateSSL(true, nil)]),
valid(trust, for: [SecPolicyCreateSSL(true, host as CFString)]) else {
return false
}
let serverCertificatesData = Set(
(0..<SecTrustGetCertificateCount(trust))
.compactMap { SecTrustGetCertificateAtIndex(trust, $0) }
.map { SecCertificateCopyData($0) as Data }
)
let pinnedCertificatesData = Set(
certificates.map { SecCertificateCopyData($0) as Data }
)
return !serverCertificatesData.isDisjoint(with: pinnedCertificatesData)
}
The warning I get in Xcode 13 beta is:
'SecTrustGetCertificateAtIndex' was deprecated in iOS 15.0: renamed to 'SecTrustCopyCertificateChain(_:)'.
Use 'SecTrustCopyCertificateChain(_:)' instead.
However, SecTrustGetCertificateAtIndex (docs) returns SecCertificate where SecTrustCopyCertificateChain (docs) returns a CFArray. How can this properly be updated in the usage I provided?
iOS 14.5 => iOS 15 SDK Diff indicates that the only additions are these (as of Xcode 13 Beta 1)
SecBase.h
Added errSecInvalidCRLAuthority
Added errSecInvalidTupleCredentials
Added errSecCertificateDuplicateExtension
SecTrust.h
Added SecTrustCopyCertificateChain()
They didn't add any new sibling type to SecCertificate. As you already noted that it returns a CFArray.
func SecTrustCopyCertificateChain(_ trust: SecTrust) -> CFArray?
So for this part of your code -
let serverCertificatesData = Set(
(0..<SecTrustGetCertificateCount(trust))
.compactMap { SecTrustGetCertificateAtIndex(trust, $0) }
.map { SecCertificateCopyData($0) as Data }
)
It seems worth a try that SecTrustCopyCertificateChain might return a CFArray of SecCertificate instances? Unfortunately I can't debug this right now.
Maybe try something like this -
if let certificates = SecTrustCopyCertificateChain(trust) as? [SecCertificate] {
let serverCertificatesData = Set(
certificates.map { SecCertificateCopyData($0) as Data }
)
}
I have a working REST API based on this API Gateway tutorial. I'm able to successfully invoke it via the test functionality of the AWS Console; and I'm able to successfully invoke it via my simple iOS Swift 4.2 Xcode application using the iPhone XR simulator.
I know it's working via a real, live external call because I can see the Cloudwatch logs which always register a 200 response and is sending the results back to the Client.
My problem is really in understanding the Swift code, and I'm hoping that a Swift expert can help me understand how to unpack result in the code below.
Here's my code in ViewController.swift for invoking the REST API and attempting to print result to the console:
#IBAction func userInvokeApi(_ sender: UIButton) {
print("You clicked invoke api...")
let client = SVTLambdaGateClient.default()
client.calcGet(operand2: "3", _operator: "+", operand1: "5").continueWith{ (task: AWSTask?) -> AnyObject? in
if let error = task?.error {
print("Error occurred: \(error)")
return nil
}
if let result = task?.result {
// Do something with result
print("The result is... \(result)")
}
return nil
}
}
As pointed out in the comments below, I'm getting the following result because it's printing out the address of the object:
You clicked invoke api...
The result is... <AmplifyRestApiTest.Empty: 0x600002020770> {
}
(where AmplifyRestApiTest is the name of my Xcode project.)
UPDATE When I set a breakpoint on the print statement, this is what I see in the Debug pane:
UPDATE 2
When I type task?.result there are two viable properties as per this answer from the Amplify team: error and result. So, since my API responds successfully I am assuming I just don't know how to view result.
Can someone help me understand what steps I must take to access members of this class object?
Here is the corresponding method in the API Gateway-generated iOS Swift SDK code:
/*
#param operand2
#param _operator
#param operand1
return type: Empty
*/
public func calcGet(operand2: String, _operator: String, operand1: String) -> AWSTask<Empty> {
let headerParameters = [
"Content-Type": "application/json",
"Accept": "application/json",
]
var queryParameters:[String:Any] = [:]
queryParameters["operand2"] = operand2
queryParameters["operator"] = _operator
queryParameters["operand1"] = operand1
let pathParameters:[String:Any] = [:]
return self.invokeHTTPRequest("GET", urlString: "/calc", pathParameters: pathParameters, queryParameters: queryParameters, headerParameters: headerParameters, body: nil, responseClass: Empty.self) as! AWSTask<Empty>
}
I'm fairly certain this return type of Empty refers to the Empty model defined for the REST API as shown in the screenshot below. I think it's "empty" because the API doesn't alter the response from the Lambda function back to the Client. So, it's all pass-through. Indeed, the tutorial explains that the other models -- Output and Result -- are not used because it "relies on the passthrough behavior and does not use this model."
Any thoughts?
I would like to globally ignore all println() calls in my Swift code if I am not in a Debug build. I can't find any robust step by step instructions for this and would appreciate guidance. is there a way to do this globally, or do I need to surround every println() with #IF DEBUG/#ENDIF statements?
The simplest way is to put your own global function in front of Swift's println:
func println(object: Any) {
Swift.println(object)
}
When it's time to stop logging, just comment out the body of that function:
func println(object: Any) {
// Swift.println(object)
}
Or you can make it automatic by using a conditional:
func println(object: Any) {
#if DEBUG
Swift.println(object)
#endif
}
EDIT In Swift 2.0 println is changed to print. Unfortunately it now has a variadic first parameter; this is cool, but it means you can't easily override it because Swift has no "splat" operator so you can't pass a variadic in code (it can only be created literally). But you can make a reduced version that works if, as will usually be the case, you are printing just one value:
func print(items: Any..., separator: String = " ", terminator: String = "\n") {
Swift.print(items[0], separator:separator, terminator: terminator)
}
In Swift 3, you need to suppress the external label of the first parameter:
func print(_ items: Any..., separator: String = " ", terminator: String = "\n") {
Swift.print(items[0], separator:separator, terminator: terminator)
}
Updated for Swift 4.x:
With Swift 2.0/3.0 and Xcode 7/8 now out of beta, there have been some changes to how you disable the print function in release builds.
There are some important points mentioned by #matt and #Nate Birkholz above that are still valid.
The println() function has been replaced by print()
To use the #if DEBUG macro then you have to define the "Swift Compiler - Custom Flags -Other Flags" to contain the value -D DEBUG
I would recommend overriding the Swift.print() function in the global scope so that you can use the print() function as normal in your code, but it will remove output for non-debug builds. Here is a function signature that you can add at the global scope to do this in Swift 2.0/3.0:
func print(items: Any..., separator: String = " ", terminator: String = "\n") {
#if DEBUG
var idx = items.startIndex
let endIdx = items.endIndex
repeat {
Swift.print(items[idx], separator: separator, terminator: idx == (endIdx - 1) ? terminator : separator)
idx += 1
}
while idx < endIdx
#endif
}
Note: We have set the default separator to be a space here, and the default terminator to be a newline. You can configure this differently in your project if you would like.
Hope this helps.
Update:
It is usually preferable to put this function at the global scope, so that it sits in front of Swift's print function. I find that the best way to organize this is to add a utility file to your project (like DebugOptions.Swift) where you can place this function at the global scope.
As of Swift 3 the ++ operator will be deprecated. I have updated the snippet above to reflect this change.
The problem with all these approaches, including mine, is that they do not remove the overhead of evaluating the print arguments. No matter which of them you use, this is going to be expensive:
print(myExpensiveFunction())
The only decent solution is to wrap the actual print call in conditional compilation (let's assume that DEBUG is defined only for debug builds):
#if DEBUG
print(myExpensiveFunction())
#endif
That, and only that, prevents myExpensiveFunction from being called in a release build.
However, you can push back evaluation one level by using autoclosure. Thus, you could rewrite my solution (this is Swift 3) like this:
func print(_ item: #autoclosure () -> Any, separator: String = " ", terminator: String = "\n") {
#if DEBUG
Swift.print(item(), separator: separator, terminator: terminator)
#endif
}
This solves the problem just in the case where you are printing just one thing, which is usually true. That's because item() is not called in release mode. print(myExpensiveFunction()) thus ceases to be expensive, because the call is wrapped in a closure without being evaluated, and in release mode, it won't be evaluated at all.
Easy Answer - Xcode 14, Swift 5
Create a new file in your project and paste in this code:
import Foundation
func print(_ items: Any..., separator: String = " ", terminator: String = "\n") {
#if DEBUG
Swift.print(items, separator: separator, terminator: terminator)
#endif
}
This function signature matches the default Swift print so it overwrites the function throughout your project. If needed you can still access the original by using Swift.print().
Once you've added the code above, keep using print() the as usual and it will only print in debug builds.
As noted, i am a student and need things defined a little more clearly to follow along. After lots of research, the sequence I needed to follow is:
Click on the project name at the top of the File Navigator at the left of the Xcode project window. This is line that has the name of the project, how many build targets there are, and the iOS SDK version.
Choose the Build Settings tab and scroll down to the "Swift Compiler - Custom Flags" section near the bottom. Click the Down Arrow next to Other Flags to expand the section.
Click on the Debug line to select it. Place your mouse cursor over the right side of the line and double-click. A list view will appear. Click the + button at the lower left of the list view to add a value. A text field will become active.
In the text field, enter the text -D DEBUG and press Return to commit the line.
Add a new Swift file to your project. You are going to want to make a custom class for the file, so enter text along the lines of the following:
class Log {
var intFor : Int
init() {
intFor = 42
}
func DLog(message: String, function: String = __FUNCTION__) {
#if DEBUG
println("\(function): \(message)")
#endif
}
}
I was having trouble getting the class to be accepted by Xcode today, so the init may be a bit more heavyweight than necessary.
Now you will need to reference your custom class in any class in which you intend to use the new custom function in place of println() Add this as a property in every applicable class:
let logFor = Log()
Now you can replace any instances of println() with logFor.DLog(). The output also includes the name of the function in which the line was called.
Note that inside class functions I couldn't call the function unless I made a copy of the function as a class function in that class, and println() is also a bit more flexible with the input, so I couldn't use this in every instance in my code.
Here is a function that I use, which works perfectly in Swift 3:
func gLog<T>( _ object: #autoclosure() -> T, _ file: String = #file, _ function: String = #function, _ line: Int = #line)
{
#if DEBUG
let value = object()
let stringRepresentation: String
if let value = value as? CustomDebugStringConvertible
{
stringRepresentation = value.debugDescription
}
else if let value = value as? CustomStringConvertible
{
stringRepresentation = value.description
}
else
{
fatalError("gLog only works for values that conform to CustomDebugStringConvertible or CustomStringConvertible")
}
let fileURL = NSURL(string: file)?.lastPathComponent ?? "Unknown file"
let queue = Thread.isMainThread ? "UI" : "BG"
let gFormatter = DateFormatter()
gFormatter.dateFormat = "HH:mm:ss:SSS"
let timestamp = gFormatter.string(from: Date())
print("✅ \(timestamp) {\(queue)} \(fileURL) > \(function)[\(line)]: " + stringRepresentation + "\n")
#endif
}
Here is an example of the output it generates:
Explanation:
the green checkmark is used to enable you to quickly see your print (gLog) messages in the console, where they can sometimes get lost in a sea of other messages
the time/date stamp
the thread it is being run on -- in my case it is either the MainThread (which I call UI), or not the MainThread (which I call BG, for background thread)
the name of the file that the gLog message resides in
the function within the file that the gLog message resides in
the line number of the gLog message
the actual gLog message you would like to print out
Hope this is useful to someone else!
Tested with Swift 2.1 & Xcode 7.1.1
There's an easy way to exclude all print statements from release versions, once you know that empty functions are removed by the Swift compiler.
Side note : In the era of Objective-C, there was a pre-parser which could be used to remove NSLog statements before the compiler kicked in, like described in my answer here. But since Swift no longer has a pre-parser this approach is no longer valid.
Here's what I use today as an advanced and easily configurable log function, without ever having to worry about removing it in release builds. Also by setting different compiler flags, you can tweak the information that is logged as needed.
You can tweak the function as needed, any suggestion to improve it is welcome!
// Gobal log() function
//
// note that empty functions are removed by the Swift compiler -> use #if $endif to enclose all the code inside the log()
// these log() statements therefore do not need to be removed in the release build !
//
// to enable logging
//
// Project -> Build Settings -> Swift Compiler - Custom flags -> Other Swift flags -> Debug
// add one of these 3 possible combinations :
//
// -D kLOG_ENABLE
// -D kLOG_ENABLE -D kLOG_DETAILS
// -D kLOG_ENABLE -D kLOG_DETAILS -D kLOG_THREADS
//
// you can just call log() anywhere in the code, or add a message like log("hello")
//
func log(message: String = "", filePath: String = #file, line: Int = #line, function: String = #function) {
#if kLOG_ENABLE
#if kLOG_DETAILS
var threadName = ""
#if kLOG_THREADS
threadName = NSThread.currentThread().isMainThread ? "MAIN THREAD" : (NSThread.currentThread().name ?? "UNKNOWN THREAD")
threadName = "[" + threadName + "] "
#endif
let fileName = NSURL(fileURLWithPath: filePath).URLByDeletingPathExtension?.lastPathComponent ?? "???"
var msg = ""
if message != "" {
msg = " - \(message)"
}
NSLog("-- " + threadName + fileName + "(\(line))" + " -> " + function + msg)
#else
NSLog(message)
#endif
#endif
}
Here's where you set the compiler flags :
An example output with all flags on looks like this :
2016-01-13 23:48:38.026 FoodTracker[48735:4147607] -- [MAIN THREAD] ViewController(19) -> viewDidLoad() - hello
The code with the log() looks like this :
override func viewDidLoad() { log("hello")
super.viewDidLoad()
// Handle the text field's user input through delegate callbacks
nameTextField.delegate = self
}
Even simpler, after making sure -D DEBUG is set for the OTHER_SWIFT_FLAGS Debug build settings:
#if !DEBUG
func print(_ items: Any..., separator: String = " ", terminator: String = "\n") { }
#endif
XCode 8 introduced a few new build settings.
In particular one referred to Active Compilation Conditions does in a similar way what Other Flags settings did.
"Active Compilation Conditions" is a new build setting for passing conditional compilation flags to the Swift compiler.
As per XCode 8 (tested in 8.3.2) you will get this by default:
So without any config you can write the following:
#if DEBUG
print("⚠️ Something weird happened")
#endif
I strongly recommend you that if you use this approach extensively create a class/struct/function that wraps this logging logic. You may want to extend this further down the road.
Varun Naharia has the better solution so far. I would combine his answer with Rivera's ...
create a -D DEBUG flag on the compiler directives, build settings.
then add this code:
#if !DEBUG
public func print(_ items: Any..., separator: String = " ", terminator: String = "\n") {
}
#endif
This code will convert every print into nothing for release.
Swift 4
Xcode 10.0
maybe you could use this
func dPrint(_ message: #autoclosure () -> Any) {
#if DEBUG
print(message())
#endif
}
The reason of using #autoclosure is that if you pass a function as the message parameter, the function will be called only in debug mode, it will cause a performance hit.
unlike the Swift.print(_ items: Any..., separator: String = default, terminator: String = default) function, my solution has only one parameter, because in most cases, we don't pass multiple parameters as the print function only shows information in console, we can just convert the parameters to String: "\(param1)"+"\(param2)", right?
hope u like my solution
for my solution i make it simple
import UIKit
class DLog: NSObject {
init(title:String, log:Any) {
#if DEBUG
print(title, log)
#endif
}
}
then to show it just call
_ = DLog(title:"any title", log:Any)
You can also use a breakpoint, set it to continue after evaluation, and write the print message in the breakpoint!
You could define debug_println whose contents would be roughly:
#if DEBUG
println()
#endif
My Solution is use this code in AppDelegate before class
// Disable console log in live app
#if !arch(x86_64) && !arch(i386)
public func debugPrint(items: Any..., separator: String = " ", terminator: String = "\n") {
}
public func print(_ items: Any..., separator: String = " ", terminator: String = "\n") {
}
#endif
class AppDelegate: UIResponder, UIApplicationDelegate {
// App Delegate Code
}
Even simpler: take advantage of the fact that asserts are removed from release builds and only from there call the print. This removes all log calls (yes, even the calls to Log.da) as they are empty when building for release.
But I also heard that prints are removed for release builds, but not been able to find it in writing. So for now, I am using something like this Log below. I have a more meaty version on GitHub with emojis (for readability) and log topics (for consistency):
https://github.com/Gatada/JBits/blob/master/Project/Utility/Log.swift
public enum Log {
/// A date formatter used to create the timestamp in the log.
///
/// This formatter is only created if it is actually used, reducing the
/// overhead to zero.
static var formatter: DateFormatter?
// MARK: - API
/// Call to print message in debug area.
///
/// Asserts are removed in release builds, which make
/// the function body empty, which caused all calls to
/// be removed as well.
///
/// Result is zero overhead for release builds.
public static func da(_ message: String) {
assert(debugAreaPrint(message))
}
// MARK: - Helpers
/// The function that actually does the printing. It returns `true` to
/// prevent the assert from kicking in on debug builds.
private static func debugAreaPrint(_ message: String) -> Bool {
print("\(timestamp) - \(message)")
return true
}
/// Creates a timestamp used as part of the temporary logging in the debug area.
static private var timestamp: String {
if formatter == nil {
formatter = DateFormatter()
formatter!.dateFormat = "HH:mm:ss.SSS"
}
let date = Date()
return formatter!.string(from: date)
}
}
In code:
Log.da("This is only handled in a debug build.")
Seen in the Xcode debug area only when running a debug build:
13:36:15.047 - This is only handled in a debug build.
My Project was developed in Objective C, but from the past year I have started merging new code in Swift, So In Swift below solution worked for me, I have added that code in My Swift constant file :
func print(_ items: Any..., separator: String = " ", terminator: String = "\n") {
#if DEBUG
items.forEach {
Swift.print($0, separator: separator, terminator: terminator)
}
#endif
}
This works for me (add this as a global function in the project)
func print(_ items: Any...) {
#if DEBUG
Swift.print(items[0])
#endif
}
Looked all over SO and through Amazon's docs as well, but couldn't find any solid documentation on how to make a put request using iOS SDK, specifically using Swift.
I gather that I need to instantiate an AWSDynamoDBClient first (https://aws.amazon.com/articles/7439603059327617) but don't see that appear as a type when I'm working in xcode.
I've honestly only got two lines of code after all this struggle:
var myDynamoDBPutRequest:AWSDynamoDBPutRequest = AWSDynamoDBPutRequest()
myDynamoDBPutRequest.item = ["fbid": "test"]
I can't figure out how to run it, and doubt that request is set up properly anyway. I've also looked at PutItemInputs, but not sure how that differs from putRequest.item. If anyone can just point me in the right direction I'll be happy to investigate on my own - I'm just running out of places to look for good documentation :/
EDIT:
I've made a bit of progress, but still can't figure out how to properly create a put item input . Here is the code I have now:
var myPutItemInput:AWSDynamoDBPutItemInput = AWSDynamoDBPutItemInput()
myPutItemInput.tableName = "mytable"
var myDynamoDB = AWSDynamoDB.defaultDynamoDB()
myDynamoDB.putItem(myPutItemInput).continueWithBlock { (task:BFTask!) -> AnyObject! in
if(task.result != nil){
let myPutOutput = task.result as AWSDynamoDBPutItemOutput
println(task.result)
}else{
println("task.result was nil for put item request")
}
return nil
}//end put item task
right now I at least figured out how to execute the request, but the result is nil each time.
Here is an example of - putItem:
let dynamoDB = AWSDynamoDB.defaultDynamoDB()
let putItemInput = AWSDynamoDBPutItemInput()
putItemInput.tableName = "testTableName"
let hashValue = AWSDynamoDBAttributeValue()
hashValue.S = "testPutItem"
let stringValue = AWSDynamoDBAttributeValue()
stringValue.S = "stringValue";
putItemInput.item = [
"hashKey" : hashValue,
"stringKey" : stringValue
]
dynamoDB.putItem(putItemInput).continueWithBlock { (task:AWSTask?) -> AnyObject? in
if(task.error != nil) {
println(task.error)
}
if (task.result != nil) {
let putItemOutput = task.result as AWSDynamoDBPutItemOutput
println(putItemOutput)
}
return nil
}
Even though it's in Objective-C, looking at the integration tests may help understand how to use Amazon DynamoDB with the AWS Mobile SDK for iOS v2.