add direct test for new ProcessPrng shim

Author: RalfJung

src/tools/miri/tests/pass/shims/windows-rand.rs

@@ -6,6 +6,7 @@ use core::ptr::null_mut;
 // Windows API definitions.
 type NTSTATUS = i32;
 type BOOLEAN = u8;
+type BOOL = i32; // yes, seriously, BOOL and BOOLEAN are very different...
 const BCRYPT_USE_SYSTEM_PREFERRED_RNG: u32 = 0x00000002;
 const BCRYPT_RNG_ALG_HANDLE: *mut c_void = 0x81 as *mut c_void;
 #[link(name = "bcrypt")]
@@ -22,6 +23,16 @@ extern "system" {
     #[link_name = "SystemFunction036"]
     fn RtlGenRandom(RandomBuffer: *mut u8, RandomBufferLength: u32) -> BOOLEAN;
 }
+#[cfg(target_arch = "x86")]
+#[link(name = "bcryptprimitives", kind = "raw-dylib", import_name_type = "undecorated")]
+extern "system" {
+    pub fn ProcessPrng(pbdata: *mut u8, cbdata: usize) -> BOOL;
+}
+#[cfg(not(target_arch = "x86"))]
+#[link(name = "bcryptprimitives", kind = "raw-dylib")]
+extern "system" {
+    pub fn ProcessPrng(pbdata: *mut u8, cbdata: usize) -> BOOL;
+}
 
 fn main() {
     let mut key = [0u8; 24];
@@ -38,4 +49,10 @@ fn main() {
     let ret = unsafe { RtlGenRandom(key.as_mut_ptr(), len) };
     // RtlGenRandom returns a BOOLEAN where 0 indicates an error
     assert_ne!(ret, 0);
+
+    let len = key.len();
+    let ret = unsafe { ProcessPrng(key.as_mut_ptr(), len) };
+    // ProcessPrng is documented as always returning `TRUE`.
+    // https://learn.microsoft.com/en-us/windows/win32/seccng/processprng#return-value
+    assert_eq!(ret, 1);
 }