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Windows 95 defenses against installers that overwrite a file with an older one

devblogs.microsoft.com

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Re: Windows 95 defenses against installers that overwrite a file with an older one

#21

Post by Legend2440 »

bigstrat2003 wrote: post #17
chihuahua wrote: post #11

It must have been difficult and frustrating to work as part of the Windows team back in those days. You see all the wacky software that doesn't follow the rules properly, does whatever it wants, breaks things. And you have to figure out how Windows can accommodate all that software, keep it from breaking, and also prevent it from messing up a computer or undo the damage. They did not have the option of saying "this a…

One of the craziest Raymond Chen stories is one where a Windows API call would return a pointer to a data structure the OS had allocated for the operation. The programmers at Microsoft made the data structure bigger than they needed, for future expansion. But some third party devs noticed the extra space, and started to use it to store data for their program. Then when Windows tried to start using the extra space, th…

>I still do not understand how one can consider writing to memory the OS owns to be ok.

Things were different back then. People did a lot of hacky stuff to fit their programs into memory, because you were genuinely constrained by hardware limitations.

Not to mention, the idea of the OS owning the machine was not as well developed as it is today. Windows 3.11 was just another program, it didn't have special permissions like modern OSes, and you would routinely bypass it to talk to the hardware directly.

Re: Windows 95 defenses against installers that overwrite a file with an older one

#22

Post by rkagerer »

akdev1l wrote: post #4

>Windows 95 worked around this by keeping a backup copy of commonly-overwritten files in a hidden C:\Windows\SYSBCKUP directory. Whenever an installer finished, Windows went and checked whether any of these commonly-overwritten files had indeed been overwritten. This is truly unhinged. I wonder if running an installer under wine in win95 mode will do this.

This is truly unhinged

Granted, but at the same time it's also resolutely pragmatic.

Apparently there was already lots of software out there which expected to be able to write new versions of system components. As well as buggy software that incidentally expected to be able to write old versions, because its developers ignored Microsoft's published best practices (not to mention common sense) and and didn't bother to do a version comparison first.

The choice was to break the old software, or let it think it succeeded then clean up after the mess it made. I'd bet they considered other alternatives (e.g. sandbox each piece of software with its own set of system libraries, or intercept and override DLL calls thus ignoring written files altogether) but those introduce more complexity and redirection with arguably little benefit. (I do wonder if the cleanup still happens if something like an unexpected reboot or power loss happens at exactly the wrong time).

Could the OS have been architected in a more robust fashion from the get-go? Of course.

Could they have simply forbidden software from downgrading system components? Sure, but it'd break installers and degrade the user experience.

Since the OS historically tolerated the broken behavior, they were kind of stuck continuing to tolerate it. One thing I learned leading groups of people is if you make a rule but don't enforce it, then it isn't much of a rule (at least not one you can rely on).

I would argue the deeper mistake was not providing more suitable tooling for developers to ensure the presence of compatible versions of shared libraries. This requires a bit of game theory up front; you want to always make the incorrect path frictiony and the correct one seamless.

Re: Windows 95 defenses against installers that overwrite a file with an older one

#23

Post by kstrauser »

layer8 wrote: post #16
chihuahua wrote: post #11

It must have been difficult and frustrating to work as part of the Windows team back in those days. You see all the wacky software that doesn't follow the rules properly, does whatever it wants, breaks things. And you have to figure out how Windows can accommodate all that software, keep it from breaking, and also prevent it from messing up a computer or undo the damage. They did not have the option of saying "this a…

> I wonder how much of this problem was caused by lack of adequate documentation describing how an installer should behave, and how much was developers not reading that documentation and being content when it works on their machine. It was mostly the latter. And when Windows broke, people would blame it on Microsoft, not on the software they installed. The same if the software broke. And you didn’t have online update…

> So Microsoft had to do everything they could to ensure broken software would still work

I think they chose to do everything they could to keep it limping along. An alternative would've been a name-and-shame approach, like "This program crashed because the author made this mistake: [short description or code or whatever]", and leave them out to try until the devs stopped doing those dumb things. After a few years of pain, people would've gotten with the program, so to speak. Instead, they chose the path that put zero pressure on devs to write correctly-behaving software.

Re: Windows 95 defenses against installers that overwrite a file with an older one

#24

Post by marcosdumay »

phendrenad2 wrote: post #13

Windows, especially old versions, were beautifully pragmatic. Think about the things that would need to exist on an open-source OS to match this functionality. You'd need to: 1. Convince people to distribute programs via installers. 2. Provide some way that installers can tell the OS that they're an installer (and not invent 5 different ways to do this!) 3. Convince the creators of installers to actually use that fun…

That's not exactly what Windows installers did.

They absolutely created 10 different ways to install software; they didn't really advertised they were an installer; the only backward compatible thing there are the MS libraries; there was no common backup/restore format.

Instead, the Unix people made a mechanism for random programs to use their own libraries and not touch the system one. In fact, Windows had one too, but most applications still decided they need to break the system.

Re: Windows 95 defenses against installers that overwrite a file with an older one

#25

Post by acka »

akdev1l wrote: post #9
bombcar wrote: post #6

Earlier quoted context omitted.

> This is truly unhinged. This is bog-standard boring stuff (when presented with a similar problem, Linux invented containers lol) - read some of his other posts to realize the extent Microsoft went to maintain backwards compatibility - some are insane, some no doubt led to security issues, but you have to respect the drive.

It’s not bog-standard. Containers are not equivalent to doing what is described in the article. Containers are in fact redirecting writes so an installer script could not replace system libraries. The equivalent would be a Linux distro having the assumption that installer scripts will overwrite /usr/lib/libopenssl.so.1 with its own version and just keeping a backup somewhere and copying it back after the script execu…

Two words: proprietary installers.

If an installer expects to be able to overwrite a file and fails to do so, it might crash, leaving the user with a borked installation.

Of course you can blame the installer, but resolution of the problem might take a long time, or might never happen, depending on the willingness of the vendor to fix it.

Re: Windows 95 defenses against installers that overwrite a file with an older one

#26

Post by topspin »

jjmarr wrote: post #20
bigstrat2003 wrote: post #17

Earlier quoted context omitted.

One of the craziest Raymond Chen stories is one where a Windows API call would return a pointer to a data structure the OS had allocated for the operation. The programmers at Microsoft made the data structure bigger than they needed, for future expansion. But some third party devs noticed the extra space, and started to use it to store data for their program. Then when Windows tried to start using the extra space, th…

> But I still do not understand how one can consider writing to memory the OS owns to be ok. Your manager tells you to reduce memory usage of the program "or else".

Or you desperately need to tag some system object and the system provides no legitimate means to do so. That can be invaluable when troubleshooting things, or even just understanding how things work when the system fails to document behavior or unreasonably conceals things.

I've been there and done it, and I offer no apologies. The platform preferred and the requirements demanded by The Powers That Be were not my fault.

Re: Windows 95 defenses against installers that overwrite a file with an older one

#27

Post by badsectoracula »

jjmarr wrote: post #20
bigstrat2003 wrote: post #17

Earlier quoted context omitted.

One of the craziest Raymond Chen stories is one where a Windows API call would return a pointer to a data structure the OS had allocated for the operation. The programmers at Microsoft made the data structure bigger than they needed, for future expansion. But some third party devs noticed the extra space, and started to use it to store data for their program. Then when Windows tried to start using the extra space, th…

> But I still do not understand how one can consider writing to memory the OS owns to be ok. Your manager tells you to reduce memory usage of the program "or else".

TBH i think a more likely explanation is that they needed to somehow identify separate instances of that data structure and they thought to store some ID or something in it so that when they encountered it next they'd be able to do that without keeping copies of all the data in it and then comparing their data with the system's.

Re: Windows 95 defenses against installers that overwrite a file with an older one

#28

Post by adrian_b »

akdev1l wrote: post #9
bombcar wrote: post #6

Earlier quoted context omitted.

> This is truly unhinged. This is bog-standard boring stuff (when presented with a similar problem, Linux invented containers lol) - read some of his other posts to realize the extent Microsoft went to maintain backwards compatibility - some are insane, some no doubt led to security issues, but you have to respect the drive.

It’s not bog-standard. Containers are not equivalent to doing what is described in the article. Containers are in fact redirecting writes so an installer script could not replace system libraries. The equivalent would be a Linux distro having the assumption that installer scripts will overwrite /usr/lib/libopenssl.so.1 with its own version and just keeping a backup somewhere and copying it back after the script execu…

Windows 95 was not Windows NT and it still used the FAT32 file system, where it was not really possible to enforce access rights.

As TFA says:

You even had installers that took even more extreme measures and said, “Okay, fine, I can’t overwrite the file, so I’m going to reboot the system and then overwrite the file from a batch file, see if you can stop me.”

Re: Windows 95 defenses against installers that overwrite a file with an older one

#29

Post by acuozzo »

kstrauser wrote: post #23
layer8 wrote: post #16

Earlier quoted context omitted.

> I wonder how much of this problem was caused by lack of adequate documentation describing how an installer should behave, and how much was developers not reading that documentation and being content when it works on their machine. It was mostly the latter. And when Windows broke, people would blame it on Microsoft, not on the software they installed. The same if the software broke. And you didn’t have online update…

> So Microsoft had to do everything they could to ensure broken software would still work I think they chose to do everything they could to keep it limping along. An alternative would've been a name-and-shame approach, like "This program crashed because the author made this mistake: [short description or code or whatever]", and leave them out to try until the devs stopped doing those dumb things . After a few years o…

> After a few years of pain, people would've gotten with the program, so to speak.

Not necessarily. This was still very much the time in which choosing to stick with an old version which worked (e.g. Windows 3.1) wasn't uncommon.

Just look at how many people jumped from XP to 7 due to the network effect of "Vista sucks" and then multiply that by the fact that, at the time of 3.1->95, people had far fewer computer security concerns, if any.

Re: Windows 95 defenses against installers that overwrite a file with an older one

#30

Post by anonymars »

kstrauser wrote: post #23
layer8 wrote: post #16

Earlier quoted context omitted.

> I wonder how much of this problem was caused by lack of adequate documentation describing how an installer should behave, and how much was developers not reading that documentation and being content when it works on their machine. It was mostly the latter. And when Windows broke, people would blame it on Microsoft, not on the software they installed. The same if the software broke. And you didn’t have online update…

> So Microsoft had to do everything they could to ensure broken software would still work I think they chose to do everything they could to keep it limping along. An alternative would've been a name-and-shame approach, like "This program crashed because the author made this mistake: [short description or code or whatever]", and leave them out to try until the devs stopped doing those dumb things . After a few years o…

Yes, but that doesn't solve the customer's problem

And what does the customer do if the vendor has discontinued it? Or charges for an upgrade? Or has gone out of business?

https://devblogs.microsoft.com/oldnewthing/20031224-00/?p=41...

I'm pretty sure another one was "what if you're wrong/have a false positive detection, and slander another company, one with lawyers?"

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