How to make RustDesk builds work on Windows 7 (and probably Windows 8)

[Nadahar]

This isn't a request for support, I've been struggling with this for a couple of days and finally found the culprit. I'm thus writing this merely to share my findings with others. Rust has in their infinite wisdom (and with good help from Microsoft I'm sure) decided to stop supporting all Windows versions before Windows 10 (for a programming language that is quite serious, and this is a good reason to stay way clear of Rust) after version 1.75.

The result when trying to run an executable compiled with a more recent version of rust is the following error:

The procedure entry point ProcessPrng could not be located in the dynamic link library bcryptprimitives.dll.

I've dug into the issue a little bit, and this seems to be part of a request to Windows' random generator. Microsoft has done some shuffling of how things are organized in the DLLs, and the change done to Rust has no obvious "benefit" and I strongly suspect deliberate sabotage.

Anyway, the "fix" is sticking to Rust 1.75. The way to do this so that the builds actually work isn't that straight forward though, since the whole toolchain must be held back. What I found is that the rustup toolchain must be set to 1.75.0-x86_64-pc-windows-msvc for x86_64 builds. If you don't want to specify the toolchain for every call (including modifying the python build scripts), it's easiest to set this as the default with rustup default 1.75.0-x86_64-pc-windows-msvc. For the x86 builds it's even "harder" because it needs a nightly toolchain to support the x86 calling convention - but I found that using nightly-2023-12-21-i686-pc-windows-msvc (which should correspond to 1.75) works.

I have no Windows 8 installations, neither physical nor virtual, so I haven't been able to test Windows 8, but I'm pretty sure that the issue applies to Windows 8 as well - since the intention behind this most likely is to make things stop working for the versions of Windows that Microsoft wants to "kill".

I'm considering to make a PR modifying the build scripts to accommodate this, but it's not trivial for me to test the workflows to see that it actually works so I won't make any promises. The change in Rust has been made after the release of 1.2.3-1, so the binaries in that release work on Windows 7.

[rustdesk]

bcryptprimitives.dll is introduced by new Rust? Nobody report this issue on Rust repo?

[Nadahar]

I don't know why, bcryptprimitives.dll exists in previous Windows version too I think, but it has something to do with how they call functions or which function they use. Usually applications (or "frameworks", standard libraries) don't call it directly, they call one of several other undocumented API which then again calls ProcessPrng. Here is a discussion on the topic regarding Go. These calls aren't documented and is not in "the official API" as far as I understand, but people have found ways to call them that have worked for ages. I don't really understand the details, but as far as I can tell people are committing "optimizations" that might be a few nanoseconds quicker while killing compatibility with "unsupported" systems. I could have misunderstood something though.

[rustdesk]

rust-lang/rust#121337
I will change rust to 1.75 in the CI.

Thank you very much.

[rustdesk]

@Nadahar @21pages please test if it works on win7

[Nadahar]

@rustdesk I can't find a binary attached to the workflow run... am I looking in the wrong place? Or do I have to run the workflow myself?

[rustdesk]

Building

[21pages]

Now it works

[Nadahar]

I don't know how @21pages built it, but my manual build process is quite different from the workflows so it wouldn't be a fruitful test to use. So, while it's taken me some time, I've now modified the workflows to run in my fork and built the latest master with GitHub. I've tested both the x86 and the x86_64 versions on 32 and 64 bits Windows 7, and they both work perfectly fine 👍

Thank you for prompt action 😄

[deadash]

after testing
cargo +nightly-2024-01-25 build --target i686-pc-windows-msvc
Works, later versions fail
Stable version 1.77.0 should work, 1.77.1/2 does not

[deadash]

For more information, refer to the PR at: rust-lang/rust#121337

[asorc]

Did anyone have any problem with the Visual studio tools? Because I tried to install them, but It's not possible on Windows 7 with the usual installed at least.

[rustdesk]

https://discord.com/invite/nDceKgxnkV build channel