Question

I want to rewrite my project from C# to rust. But I stuck in Segmentation Fault situation. I think I misunderstood something, or meet crate limitation, hope for some help.

Rust Code

• find interface UUID regedit capture
• find CLSID regedit capture
• other id (I'm not sure shall we need it) regedit capture

use windows::core::{GUID, HRESULT, IUnknown, IUnknown_Vtbl, interface};
use windows::Win32::System::Com::{
    COINIT_APARTMENTTHREADED, 
    CLSCTX_ALL,
    CoInitializeEx,
    CoCreateInstance};

// define interface
#[interface("288EFDEC-3CF0-4F6C-8473-4E4CD47A93C7")]
unsafe trait Inhicshisx: IUnknown {
    fn VPNGetRandomX(&self) -> HRESULT;
}

fn run() -> Result<(), anyhow::Error> {
    unsafe {
        // 2F5AECD5-B5CD-41E1-8265-E2F6AA4548CB
        const CLSID: GUID = GUID {
            data1: 0x2F5AECD5,
            data2: 0xB5CD,
            data3: 0x41E1,
            data4: [0x82, 0x65, 0xE2, 0xF6, 0xAA, 0x45, 0x48, 0xCB],
        };
        
        // initialize runtime
        CoInitializeEx(Some(ptr::null_mut() as *mut c_void), COINIT_APARTMENTTHREADED)?;
        
        // create COM object
        let hisx: Inhicshisx = CoCreateInstance(&CLSID, None, CLSCTX_ALL)?;
        
        // call object function
        let value = hisx.VPNGetRandomX();
    }
    
    Ok(())
}

C# Part

• add a reference regedit capture
• call function

using CSHISXLib;
string MyStr0;
CSHISXLib.Inhicshisx CSHISXLibObj = new CSHISXLib.nhicshisx();
MyStr0 = CSHISXLibObj.VPNGetRandomX();
Console.WriteLine(MyStr0);

• It works.

Update information

According to @IInspectable help, I can generate interface by oleview.exe tool.

• generated interface

[
  odl,
  uuid(288EFDEC-3CF0-4F6C-8473-4E4CD47A93C7),
  helpstring("Inhicshisx Interface"),
  dual,
  oleautomation
]
interface Inhicshisx : IDispatch {
    [id(0x00000001), helpstring("method VPNGetRandomX")]
    HRESULT VPNGetRandomX([out, retval] BSTR* strRandom);
    [id(0x00000002), helpstring("method VPNH_SignX")]
    HRESULT VPNH_SignX(
                    [in] BSTR strRandom, 
                    [in, optional, defaultvalue("")] BSTR strCardType, 
                    [in, optional, defaultvalue("")] BSTR strServiceType, 
                    [out, retval] BSTR* strRet);
}

• Rust code change

use windows::core::BSTR;

#[interface("288EFDEC-3CF0-4F6C-8473-4E4CD47A93C7")]
unsafe trait Inhicshisx: IDispatch {
    fn VPNGetRandomX(&self) -> BSTR;
    fn VPNH_SignX(&self, *mut BSTR, *mut BSTR, *mut BSTR) -> BSTR;
}

But it still cause Segmentation Fault, hope some advice 🙏

Thank for @IInspectable advice.

Segmentation Fault caused by wrong interface.

Find the COM interface

you can use oleview to display for COM library interface. In my case, the interface like this.

interface Inhicshisx : IDispatch {
    [id(0x00000001), helpstring("method VPNGetRandomX")]
    HRESULT VPNGetRandomX([out, retval] BSTR* strRandom);
    [id(0x00000002), helpstring("method VPNH_SignX")]
    HRESULT VPNH_SignX(
                    [in] BSTR strRandom, 
                    [in, optional, defaultvalue("")] BSTR strCardType, 
                    [in, optional, defaultvalue("")] BSTR strServiceType, 
                    [out, retval] BSTR* strRet);
}

Declare interface in Rust

#[interface("288EFDEC-3CF0-4F6C-8473-4E4CD47A93C7")]
unsafe trait Inhicshisx: IDispatch {
    fn VPNGetRandomX(&self, random: *mut BSTR) -> HRESULT;
    fn VPNH_SignX(&self, random: BSTR, card_type: BSTR, service_type: BSTR, sign: *mut BSTR) -> HRESULT;
}