Remove static dependency on bcrypt.dll, advapi32.dll, userenv.dll

- Make `home_dir_crt` return `None` if the required APIs are not available
- Fall back to `RtlGenRandom` if `BCryptGenRandom` is not supported
- Fall back to custom `hashmap_random_keys` implementation if `RtlGenRandom` is also not supported

Author: seritools

library/std/src/sys/windows/c.rs

@@ -469,6 +469,55 @@ compat_fn_optional! {
     pub fn WakeConditionVariable(conditionvariable: *mut CONDITION_VARIABLE) -> ();
 }
 
+compat_fn_lazy! {
+    pub static USERENV: &CStr = c"userenv" => { load: true, unicows: false };
+
+    pub fn GetUserProfileDirectoryW(
+        htoken: HANDLE,
+        lpprofiledir: PWSTR,
+        lpcchsize: *mut u32,
+    ) -> BOOL;
+}
+
+compat_fn_with_fallback! {
+    pub static BCRYPT: &CStr = c"bcrypt" => { load: true, unicows: false };
+
+    pub fn BCryptGenRandom(
+        halgorithm: BCRYPT_ALG_HANDLE,
+        pbbuffer: *mut u8,
+        cbbuffer: u32,
+        dwflags: BCRYPTGENRANDOM_FLAGS,
+    ) -> NTSTATUS {
+        if SystemFunction036(pbbuffer.cast(), cbbuffer) == TRUE as _ {
+            0 // STATUS_SUCCESS
+        } else {
+            0xC0000001u32 as i32 // STATUS_UNSUCCESSFUL
+        }
+    }
+}
+
+compat_fn_lazy! {
+    pub static ADVAPI32: &CStr = c"advapi32" => { load: true, unicows: false };
+
+    pub fn OpenProcessToken(
+        processhandle: HANDLE,
+        desiredaccess: TOKEN_ACCESS_MASK,
+        tokenhandle: *mut HANDLE,
+    ) -> BOOL;
+}
+compat_fn_with_fallback! {
+    pub static ADVAPI32: &CStr = c"advapi32" => { load: true, unicows: false };
+
+    pub fn SystemFunction036(randombuffer: *mut ::core::ffi::c_void, randombufferlength: u32)
+    -> BOOLEAN {
+        0
+    }
+}
+pub const RtlGenRandom: unsafe fn(
+    randombuffer: *mut ::core::ffi::c_void,
+    randombufferlength: u32,
+) -> BOOLEAN = SystemFunction036;
+
 compat_fn_with_fallback! {
     pub static NTDLL: &CStr = c"ntdll" => { load: true, unicows: false };
 

library/std/src/sys/windows/c/windows_sys.lst

@@ -2617,3 +2617,7 @@ Windows.Win32.System.Time.SystemTimeToFileTime
 Windows.Win32.Storage.FileSystem.SetFilePointer
 Windows.Win32.Storage.FileSystem.SetEndOfFile
 Windows.Win32.Storage.FileSystem.INVALID_SET_FILE_POINTER
+
+// hashmap crypt fallback
+Windows.Win32.System.SystemInformation.GetTickCount
+Windows.Win32.System.Threading.GetCurrentThreadId

library/std/src/sys/windows/c/windows_sys.rs

@@ -282,6 +282,10 @@ extern "system" {
     pub fn GetCurrentThread() -> HANDLE;
 }
 #[link(name = "kernel32")]
+extern "system" {
+    pub fn GetCurrentThreadId() -> u32;
+}
+#[link(name = "kernel32")]
 extern "system" {
     pub fn GetEnvironmentStringsW() -> PWSTR;
 }
@@ -393,6 +397,10 @@ extern "system" {
     pub fn GetTempPathW(nbufferlength: u32, lpbuffer: PWSTR) -> u32;
 }
 #[link(name = "kernel32")]
+extern "system" {
+    pub fn GetTickCount() -> u32;
+}
+#[link(name = "kernel32")]
 extern "system" {
     pub fn GetWindowsDirectoryW(lpbuffer: PWSTR, usize: u32) -> u32;
 }

library/std/src/sys/windows/os.rs

@@ -320,6 +320,10 @@ pub fn temp_dir() -> PathBuf {
 
 #[cfg(not(target_vendor = "uwp"))]
 fn home_dir_crt() -> Option<PathBuf> {
+    if c::OpenProcessToken::option().is_none() || c::GetUserProfileDirectoryW::option().is_none() {
+        return None;
+    }
+
     unsafe {
         // The magic constant -4 can be used as the token passed to GetUserProfileDirectoryW below
         // instead of us having to go through these multiple steps to get a token. However this is

library/std/src/sys/windows/rand.rs

@@ -4,15 +4,22 @@ use crate::sys::c;
 
 pub fn hashmap_random_keys() -> (u64, u64) {
     let mut v = (0, 0);
-    let ret = unsafe {
-        c::BCryptGenRandom(
-            ptr::null_mut(),
-            &mut v as *mut _ as *mut u8,
-            mem::size_of_val(&v) as c::ULONG,
-            c::BCRYPT_USE_SYSTEM_PREFERRED_RNG,
-        )
-    };
-    if c::nt_success(ret) { v } else { fallback_rng() }
+
+    if c::BCryptGenRandom::available() {
+        let ret = unsafe {
+            c::BCryptGenRandom(
+                ptr::null_mut(),
+                &mut v as *mut _ as *mut u8,
+                mem::size_of_val(&v) as c::ULONG,
+                c::BCRYPT_USE_SYSTEM_PREFERRED_RNG,
+            )
+        };
+        if c::nt_success(ret) { v } else { fallback_rng() }
+    } else if c::SystemFunction036::available() {
+        fallback_rng()
+    } else {
+        true_fallback_rng()
+    }
 }
 
 /// Generate random numbers using the fallback RNG function (RtlGenRandom)
@@ -40,3 +47,18 @@ fn fallback_rng() -> (u64, u64) {
 fn fallback_rng() -> (u64, u64) {
     panic!("fallback RNG broken: RtlGenRandom() not supported on UWP");
 }
+
+#[inline(never)]
+fn true_fallback_rng() -> (u64, u64) {
+    unsafe {
+        let tickCount = c::GetTickCount();
+        let id = c::GetCurrentThreadId();
+        let mut file_time: c::FILETIME = crate::mem::zeroed();
+        c::GetSystemTimeAsFileTime(&mut file_time as *mut _);
+
+        (
+            (file_time.dwHighDateTime as u64) << 32 | tickCount as u64,
+            (id as u64) << 32 | file_time.dwLowDateTime as u64,
+        )
+    }
+}