Problems when passing password containing umlauts to Process as argument in Swift

Question

So I am trying to execute a command using sudo from Swift using the following code (as suggested here:

func doTask(_ password:String) {
    let taskOne = Process()
    taskOne.launchPath = "/bin/echo"
    taskOne.arguments = [password]

    let taskTwo = Process()
    taskTwo.launchPath = "/usr/bin/sudo"
    taskTwo.arguments = ["-S", "/usr/bin/xattr", "-d", "-r", "com.test.exemple", " /Desktop/file.extension"]
    //taskTwo.arguments = ["-S", "/usr/bin/touch", "/tmp/foo.bar.baz"]

    let pipeBetween:Pipe = Pipe()
    taskOne.standardOutput = pipeBetween
    taskTwo.standardInput = pipeBetween

    let pipeToMe = Pipe()
    taskTwo.standardOutput = pipeToMe
    taskTwo.standardError = pipeToMe

    taskOne.launch()
    taskTwo.launch()

    let data = pipeToMe.fileHandleForReading.readDataToEndOfFile()
    let output : String = NSString(data: data, encoding: String.Encoding.utf8.rawValue) as! String
    print(output)
}

It works just fine for passwords such as "test", "password#123" etc. But when I try a password containing an umlaut such as "ä","ü" or "ö" in doesn't work. Any ideas why?

What do you get for the umlauted characters? Is it just umlauts that are the problem? Have you tried other diacritics for example `é` or `ñ`? — Chip Jarred, Jul 01 '21 at 12:23
@ChipJarred I just tried the password "aaaé" and that doesn't work either. So I assume other diacritics will not work too. — user10802841, Jul 01 '21 at 12:28
Just a thought. `sudo` is a very old part of `Unix`. It might not take `.utf8` encoded characters. I'm pretty sure `.ascii` won't work because technically ASCII is only 7 bit characters, but you could try `.isoLatin1`, `.isoLatin2`, `.macRoman`, or `.nextstep` — Chip Jarred, Jul 01 '21 at 12:30
I ran your code in a playground. Replaced the password with `"ü"`. The output correctly indicates that my password is incorrect. — Sweeper, Jul 01 '21 at 12:38
Completely unrelated but the `NSString - String` dance is horrible. Replace the line with `let output = String(data: data, encoding: .utf8)!` — vadian, Jul 01 '21 at 12:49
Does `echo yourPassword | sudo -S xattr…` on the command line work with umlauts? — Martin R, Jul 01 '21 at 12:50
@ChipJarred How would you do that? I tried it with this: `String(data: "+ü#ä".data(using: .macOSRoman)!, encoding: .macOSRoman)!` but it doesn't work. Output: `Password:Sorry, try again. Password: sudo: no password was provided sudo: 1 incorrect password attempt` — user10802841, Jul 01 '21 at 13:10
Actually the problem will be where you set the password, because that's where it will be sent through the pipe to `sudo`. I think you first need to determine see what's coming out the other end of the pipe... so maybe replace `task2` with `/usr/bin/cat` to just dump the pipe to stdout. Or even better to `/usr/bin/tee`. For `tee` you'll need to provide a file path as a parameter, just a file in your home directory will work. Then you can open it to see exactly what is being received through the pipe without worry about how Swift decodes it. — Chip Jarred, Jul 01 '21 at 13:25
I hope it was obvious but use a temporary file name for the argument to `tee` in my last comment, because it will overwrite the file, so you don't want to use path to an existing file you want to keep. — Chip Jarred, Jul 01 '21 at 13:31
@ChipJarred I tried that one and dumped the output of echo to test.txt using tee. The output of test.txt is: `+ü#ä` so the exact same text I put in :/ (See https://imgur.com/a/598Tu9s) — user10802841, Jul 01 '21 at 13:59

idz · Accepted Answer · 2021-07-02T17:57:15.603

1

I'm not sure why the answer to the other question piped through echo... seems to introduce unnecessary complications and unknowns.

The following more direct approach is tested and working:

import Foundation

let password = "äëïöü"
let passwordWithNewline = password + "\n"
let sudo = Process()
sudo.launchPath = "/usr/bin/sudo"
sudo.arguments = ["-S", "/bin/ls"]
let sudoIn = Pipe()
let sudoOut = Pipe()
sudo.standardOutput = sudoOut
sudo.standardError = sudoOut
sudo.standardInput = sudoIn
sudo.launch()

// Show the output as it is produced
sudoOut.fileHandleForReading.readabilityHandler = { fileHandle in
    let data = fileHandle.availableData
    if (data.count == 0) { return }
    print("read \(data.count)")
    print("\(String(bytes: data, encoding: .utf8) ?? "<UTF8 conversion failed>")")

}
// Write the password
sudoIn.fileHandleForWriting.write(passwordWithNewline.data(using: .utf8)!)

// Close the file handle after writing the password; avoids a
// hang for incorrect password.
try? sudoIn.fileHandleForWriting.close()

// Make sure we don't disappear while output is still being produced.
sudo.waitUntilExit()
print("Process did exit")

The crux is that you must add a newline after the password. (I suppose in some ways echo is just an overly complicated way of doing that!)

edited Jul 02 '21 at 17:57

answered Jul 01 '21 at 15:36

idz

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However, I noticed that if you enter a wrong password, the process runs indefinitely. – user10802841 Jul 02 '21 at 12:59
1

Hmm, not the behavior I observed, but easily fixed if you parse the output. It will hang if you do not include the new line. – idz Jul 02 '21 at 14:47
1

Whoops! my apologies, I just rechecked my code and I left out a line in my answer (this is why I was not seeing a hang on an incorrect password). I close the input stream after writing the password. I will update my answer! – idz Jul 02 '21 at 17:55
Thank you! Is there an alternative for ```sudoIn.fileHandleForWriting.close()``` because this function is only avaiable in macOS 10.15 or higher. – user10802841 Jul 09 '21 at 20:32
Would ```sudoIn.fileHandleForWriting.closeFile()``` work? – user10802841 Jul 09 '21 at 20:51
1

Should be fine, I guess they changed the name? Try it and see! – idz Jul 09 '21 at 20:53

Problems when passing password containing umlauts to Process as argument in Swift

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