Ask Ubuntu General Room

Serg

12:13 AM

@IanC evening !

IanC

how are you doing @Serg?

better from that annoying cold?

Serg

@IanC slightly better , but still coughing hard. I take forever to recover from colds

I need eye and ear bleach right now

Seth

so apparently the sticky keys binary in Windows is named sethc.exe

Thomas Ward

we have something that is about as useful, @Serg

but you won't like it.

Serg

@Seth yer a sticky key, Sethy !

Kaz Wolfe

12:24 AM

@Seth Why does that need its own binary, as opposed to being part of the keyboard system in general?

Seth

haha

Serg

@ThomasWard i wonder what could that be

Seth

@KazWolfe I asked myself the same thing.

Eliah Kagan

Yes. You can back it up and replace it with a copy of cmd.exe to get a SYSTEM command prompt on the login screen by pressing shift five times. (This is not a security vulnerability in Windows -- you have to be an administrator to set it up that way -- but of course one should not leave one's system that way after one is done.) This is handy if one needs to reset a lost password, and one doesn't have (or wish to use) MSDaRT or some other environment with the ability to edit the registry.

Serg

Yeah, it's an ancient trick, heard of it a while back.

Kaz Wolfe

12:26 AM

@EliahKagan That seems excessively dangerous and just shows how poor Windows' security model is.

Serg

Another old trick on windows was somehow via recovery. There was a way to bring up notepad, open the "open file" dialog, and browse filesystem. Effectively as privileged user, i think

Don't remember the details though

Thomas Ward

probably before UAC became a thing

Eliah Kagan

@KazWolfe I definitely wouldn't recommend doing it on a machine that shows its login screen to untrusted clients over RDP! Aside from that, though, I don't see how it's more dangerous than any other way of temporarily allowing access to fix a broken system. I see no reason something similar couldn't be done in Ubuntu. One could replace login, or something. Of course this is unnecessary because we have chroot, store most configuration in plain text, and so forth.

I much prefer the Unix way. But I don't think the main difference (in this particular case) is one of security.

Serg

Definitely Unix security is better

Eliah Kagan

I agree it is better.

Kaz Wolfe

12:29 AM

@EliahKagan Doesn't login run as its own user as opposed to root? I mean, yeah, there is always the issue of binary swapping, but the system has a lot more sane permission restrictions.

Serg

There was a pretty good answer on Quora about it somewhere

Kaz Wolfe

\o/ self-answers = rep farm

Serg

@KazWolfe unless someone faster answers your question before you post yours

Journeyman Geek

@KazWolfe I think of it as sock-umentation ;p

Kaz Wolfe

@Serg there's that checkmark on the ask page.

IanC

12:32 AM

you can ask and answer at the same time

Thomas Ward

@JourneymanGeek You either meant sock-umentation or documentation

IanC

man, I'm having a headache with scanf

Serg

And yes, self - documentation

Journeyman Geek

@ThomasWard yes

Eliah Kagan

12:45 AM

@KazWolfe I believe it is true way less runs as root on a modern Unix-like operating system than runs as SYSTEM on Windows, and that this is one of a number of factors that make Unix-like systems these days more secure overall. ...In a 16.04 system with one user logged in and no logins in progress, with no GUI installed, /bin/login -- is running as root. Still, that wasn't really the right example.

A Unix-like system has a number of setuid root executables, like the passwd, su and (on many systems, including Ubuntu) sudo. Someone who can change files can just copy whatever they want into those executables, or just make their own executables setuid root. This is not a vulnerability, even though it may be alarming to some people who learn of it.

Kaz Wolfe

True, but setuid needs someone to be root, unless someone foolishly added o+w on that file.

Eliah Kagan

@KazWolfe Right. That's why it's not a vulnerability. Same deal with making sethc.exe really cmd.exe on Windows -- you have to already be an administrator to make that change.

Kaz Wolfe

Windows, though, is a lot more lenient about giving perms out.

Eliah Kagan

@KazWolfe Agreed. In particular, people usually run as administrators (though perhaps more for cultural reasons than technical ones, these days), and UAC, while better than nothing, is not the same as actually having a separate user account that doesn't formally have unlimited power.

@Serg That reminds me of Novell Netware for Windows 98. The login screen had a question mark button you could click to get help. When you went into the help, you could go to File > Open to open a help file. You could browse the filesystem this way. Only folders and help files were shown, but if you typed in *.* it would show all files, and you could find any executable, right-click on it, and run it. You could thus run explorer.exe this way and get a desktop, without having to log in.

Kaz Wolfe

openvpn, pls work.

Eliah Kagan

12:58 AM

@IanC scanf woes?

Serg

@IanC try fscanf() maybe ?

IanC

@EliahKagan @Serg I'm trying to improve an answer on SO. There was one suggestion on using scanf instead of a loop to clear the stdin before fgets. According to some answers scanf("%*[^\n]%*c"); or scanf("%*[^\n]\n"); should work, but both are failing -.-

I could just keep the loop on the answer, but my curiosity is killing me

because theoretically it should work

"%*[^\n]" would consume everything up to (but not including) the newline, and then "%*c" would consume one character (a newline). "\n" would consume any whitespaces (including a newline character)

so both should be able to clear the hanging newline left of a scanf("%d", &number);

Serg

God I hate when someone openly tries to argue just to get their way

@IanC very peculiar use of scanf() , I've never seen that before. It sort of looks like regular expression, which I thought cannot be used in C

IanC

it isn't a regular expression, I first thought that too, but it's specified on the scanf formats

cplusplus.com/reference/cstdio/scanf

the * means discard whatever is read

%*[^\n] = discards everything that doesn't match a newline (would stop at the newline character without consuming it)

%*c = consume exactly one character discarding it

\n = whitespace character: would read and discard every white space character until the first non-white space character

according to their meaning both should work on cleaning the stdin after scanf("%d", &number);, but fgets is still quitting prematurely, meaning there's probably still some newline hanging

IanC

2:08 AM

0

Q: Why aren't scanf("%*[^\n]\n"); and scanf("%*[^\n]%*c"); clearing a hanging newline?

After a call to scanf("%d", &variable); we are left with a newline hanging at the stdin, which should be cleared before a call to fgets, or we end up feeding it a newline and making it return prematurely. I've found answers suggesting using scanf("%*[^\n]%*c"); after the first call to scanf to d...

I hope someone can answer that, because I've seem people using those approaches in other answers and have no idea why it isn't working here

but for the time being, I just edited my answer to use better words, still using the functional code

Zacharee1

2:25 AM

I wonder how long it's gonna take for this guy to get banned askubuntu.com/users/609989/phoen1x74

2GHz of memory makes no sense... — Zacharee1 14 secs ago

Seth

0

Q: How to add another boot option to grub?

So after creating a new 100 gb partition /dev/sda6, I extracted the .iso of RemixOS (which I want to dualboot with Ubuntu) to. I'm wondering how I get it to show up on GRUB's menu as an OS.

grub2

do we not have a generic question about updating grub?

btw, that's not off-topic people!

Zacharee1

@Fabby don't downvote answers just because they answer a bad question. Judge by the post. — Zacharee1 12 secs ago

tsk tsk

Serg

@Seth apparently they noticed Remix OS there in the text body, and close voting without reading

IanC

@Serg I got an answer!! :)

Serg

@IanC saw it. Needs two scanf calls

Seth

2:34 AM

@Serg I hate it when people do that

Serg

@Seth don't mind if I go rant there in the comments just a little ?

Seth

Ranting here is fine. Not the comment unless you have something constructive to add please.

Zacharee1

wait

the question itself may not be off topic, but the answer for that question isn't going to work

Seth

no, it's not. but what you said still stands.

Zacharee1

RemixOS is Android, and runs under a system.img and data.img

GRUB isn't going to find that

Seth

2:37 AM

Add a comment on the question

Zacharee1

I've done the RemixOS setup for GRUB. I needed to install with Windows, do the GRUB scan, boot into it, bypass the error, get to the RemixOS GRUB, let it actually install, etc etc etc

I don't even remember what I did

Serg

Huh, very odd. That question says there's 2 close votes, but once i click on the close button and show the menu, it shows only one as off-topic

Zacharee1

refresh

added