ci: run PEDM simulator as LocalSystem using psexec

Author: CBenoit

.github/workflows/ci.yml

@@ -1000,17 +1000,27 @@ jobs:
           ref: ${{ needs.preflight.outputs.ref }}
 
       - name: Prepare runner
-        run: rustup toolchain install nightly
+        run: |
+          rustup toolchain install nightly
+          choco install pstools --yes
 
       - name: Prepare PEDM simulator build
         run: ./crates/pedm-simulator/prepare.ps1
 
       - name: Build PEDM simulator container
         run: ./crates/pedm-simulator/build-container.ps1
 
-      - name: Run PEDM simulator (limited test)
+      - name: Run PEDM simulator (container with limited user)
         run: ./crates/pedm-simulator/run-container.ps1
 
+      - name: Run PEDM simulator (as LocalSystem)
+        run: |
+          # It’s difficult to get realtime stdout/stderr when using psexec -s.
+          # Instead, the run-expect-elevation.ps1 script will redirect the output into a file that we can read afterwards.
+          $scriptPath = Resolve-Path -Path "./crates/pedm-simulator/run-expect-elevation.ps1"
+          psexec -accepteula -s pwsh.exe $scriptPath
+          Get-Content -Path ./crates/pedm-simulator/pedm-simulator_run-expect-elevation.out
+
   success:
     name: Success
     runs-on: ubuntu-latest

crates/pedm-simulator/README.md

@@ -8,15 +8,15 @@
 
 ## Limited test with no elevation
 
-This mode is a stopgap until we have proper infrastructure for performing
-the complete test in the CI. Indeed, there is no way to perform the complete
-test using GitHub-hosted runners (or docker), because for security reasons
-ContainerAdministrator is not assigned the SE_CREATE_TOKEN_NAME privilege, and
-it’s not possible to perform nested virtualization either.
+A limited test where the elevation procedure will fail. This test is still
+useful because it will exercise a different code path than the "complete" test.
+It’s also convenient for testing without using an elevated account with the
+`SE_CREATE_TOKEN_NAME` privilege assigned.
 
-You can run the pedm-simulator.exe executable directly.
+When running under a user without the `SE_CREATE_TOKEN_NAME` privilege, you can
+just run the `pedm-simulator.exe` executable directly.
 
-If you are running using an elevated account with the SE_CREATE_TOKEN_NAME
+If you are running using an elevated account with the `SE_CREATE_TOKEN_NAME`
 privilege assigned, you can build and run a container instead to ensure
 the privilege is not available.
 
@@ -25,9 +25,11 @@ the privilege is not available.
 .\run-container.ps1
 ```
 
+You may also consider logging into a different user with lower privileges.
+
 ## Complete test with elevation
 
-It is recommended to use a dedicated VM.
+It is recommended to use a dedicated VM for this test.
 
 Visual C++ Redistribuable are required.
 
@@ -40,9 +42,9 @@ Start-Process -filepath C:\vc_redist.x64.exe -ArgumentList "/install", "/passive
 Remove-Item -Force vc_redist.x64.exe
 ```
 
-Retrieve the artifacts (including clang_rt.asan_dynamic-x86_64.dll).
+Retrieve the artifacts (including `clang_rt.asan_dynamic-x86_64.dll`).
 
-For the next steps, make sure to use an account with the SE_CREATE_TOKEN_NAME
+For the next steps, make sure to use an account with the `SE_CREATE_TOKEN_NAME`
 privilege assigned.
 
 Set the `PEDM_SIMULATOR_EXPECT_ELEVATION` environment variable.

crates/pedm-simulator/run-expect-elevation.ps1

@@ -0,0 +1,16 @@
+#!/bin/env pwsh
+
+$ErrorActionPreference = "Stop"
+
+Push-Location -Path $PSScriptRoot
+
+$exitCode = 0
+
+try {
+	$Env:PEDM_SIMULATOR_EXPECT_ELEVATION = '1'
+	& ./artifacts/pedm-simulator.exe 2>&1 | Out-File ./pedm-simulator_run-expect-elevation.out
+	$exitCode = $LASTEXITCODE
+} finally {
+	Pop-Location
+	exit $exitCode
+}

crates/pedm-simulator/src/main.rs

@@ -4,6 +4,7 @@ use anyhow::Context as _;
 use win_api_wrappers::identity::account::{enumerate_account_rights, get_username, lookup_account_by_name};
 use win_api_wrappers::identity::sid::{Sid, SidAndAttributes};
 use win_api_wrappers::process::Process;
+use win_api_wrappers::raw::core::HRESULT;
 use win_api_wrappers::raw::Win32::Foundation::LUID;
 use win_api_wrappers::raw::Win32::Security;
 use win_api_wrappers::raw::Win32::System::SystemServices;
@@ -25,32 +26,56 @@ fn main() -> anyhow::Result<()> {
         .context("open current process token")?;
 
     // Verify that the current account is assigned with the SE_CREATE_TOKEN_NAME privilege.
-    let account_username = get_username(Security::Authentication::Identity::NameSamCompatible).unwrap();
+    println!("Attempting to verify whether the current account is assigned with the SE_CREATE_TOKEN_NAME privilege");
+    let account_username =
+        get_username(Security::Authentication::Identity::NameSamCompatible).context("retrieve account username")?;
     println!("Account name: {account_username:?}");
-    let account = lookup_account_by_name(&account_username).unwrap();
-    let rights = enumerate_account_rights(&account.sid).unwrap();
-    let has_create_token_right = rights.iter().any(|right| right == u16cstr!("SeCreateTokenPrivilege"));
 
-    if expect_elevation {
-        assert!(has_create_token_right);
-
-        // SE_CREATE_TOKEN_NAME is required for performing the elevation.
-        let se_create_token_name_luid = privilege::lookup_privilege_value(None, privilege::SE_CREATE_TOKEN_NAME)
-            .context("lookup SE_CREATE_TOKEN_NAME privilege")?;
-        token
-            .adjust_privileges(&TokenPrivilegesAdjustment::Enable(vec![se_create_token_name_luid]))
-            .context("enable SE_CREATE_TOKEN_NAME privilege")?;
-
-        // Verify the SE_CREATE_TOKEN_NAME privilege is actually enabled.
-        let se_create_token_name_is_enabled = token
-            .privileges()
-            .context("list token privileges")?
-            .as_slice()
-            .iter()
-            .find(|privilege| privilege.Luid == se_create_token_name_luid)
-            .is_some();
-
-        assert!(se_create_token_name_is_enabled);
+    match lookup_account_by_name(&account_username) {
+        Ok(account) => {
+            let rights = enumerate_account_rights(&account.sid)
+                .with_context(|| format!("enumerate account rights for {account_username:?}"))?;
+            let has_create_token_right = rights.iter().any(|right| right == u16cstr!("SeCreateTokenPrivilege"));
+
+            if expect_elevation {
+                assert!(has_create_token_right);
+
+                // SE_CREATE_TOKEN_NAME is required for performing the elevation.
+                let se_create_token_name_luid =
+                    privilege::lookup_privilege_value(None, privilege::SE_CREATE_TOKEN_NAME)
+                        .context("lookup SE_CREATE_TOKEN_NAME privilege")?;
+                token
+                    .adjust_privileges(&TokenPrivilegesAdjustment::Enable(vec![se_create_token_name_luid]))
+                    .context("enable SE_CREATE_TOKEN_NAME privilege")?;
+
+                // Verify the SE_CREATE_TOKEN_NAME privilege is actually enabled.
+                let se_create_token_name_is_enabled = token
+                    .privileges()
+                    .context("list token privileges")?
+                    .as_slice()
+                    .iter()
+                    .find(|privilege| privilege.Luid == se_create_token_name_luid)
+                    .is_some();
+
+                assert!(se_create_token_name_is_enabled);
+            }
+        }
+        Err(e) => {
+            println!("Failed to look up account for {account_username:?}: {e}");
+
+            // Possible issue when running this program using psexec -s, under `NT AUTHORITY\SYSTEM` (LocalSystem):
+            // - There is no direct domain credentials by default, unless the machine is domain joined and has a line-of-sight to the DC.
+            // - This context may not be able to see the same network resources or DC that the interactive user.
+            // Causing LookupAccountNameW to fail with a "no mapping" error.
+            // Let’s just go ahead with the elevation in this case, assuming LocalSystem is enough for all intents and purposes at this point.
+            if e.code() == HRESULT(0x80070534u32 as i32) {
+                println!("Got the 'no mapping' error; continuing...")
+            } else {
+                return Err(anyhow::Error::new(e).context(format!(
+                    "unexpected error when looking up the account for {account_username:?}"
+                )));
+            }
+        }
     }
 
     let token_source = build_token_source(LADM_SRC_NAME, LADM_SRC_LUID);
@@ -122,7 +147,7 @@ fn main() -> anyhow::Result<()> {
     } else {
         match res {
             Ok(_) => {
-                anyhow::bail!("admin token creation should have failed, because the current process is not elevated")
+                anyhow::bail!("admin token creation succeded, but this was not expected")
             }
             Err(e) => {
                 assert_eq!(e.to_string(), "no token found for SE_CREATE_TOKEN_NAME privilege");