ipc: remove windows elevation

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

2 files changed, 36 insertions, 150 deletions

diff --git a/src/ipc-uapi-windows.h b/src/ipc-uapi-windows.h
index 4d362d0..8ea4f75 100644
--- a/src/ipc-uapi-windows.h
+++ b/src/ipc-uapi-windows.h
@@ -14,102 +14,37 @@
 
 static FILE *userspace_interface_file(const char *iface)
 {
-	char fname[MAX_PATH], error_message[1024 * 128] = { 0 };
-	HANDLE thread_token, process_snapshot, winlogon_process, winlogon_token, duplicated_token, pipe_handle = INVALID_HANDLE_VALUE;
-	PROCESSENTRY32 entry = { .dwSize = sizeof(PROCESSENTRY32) };
-	PSECURITY_DESCRIPTOR pipe_sd;
-	PSID pipe_sid;
+	char fname[MAX_PATH];
+	HANDLE pipe_handle;
 	SID expected_sid;
-	BOOL ret;
+	DWORD bytes = sizeof(expected_sid);
+	PSID pipe_sid;
+	PSECURITY_DESCRIPTOR pipe_sd;
+	bool equal;
 	int fd;
-	DWORD last_error = ERROR_SUCCESS, bytes = sizeof(expected_sid);
-	TOKEN_PRIVILEGES privileges = {
-		.PrivilegeCount = 1,
-		.Privileges = {{ .Attributes = SE_PRIVILEGE_ENABLED }}
-	};
 
-	if (!LookupPrivilegeValue(NULL, SE_DEBUG_NAME, &privileges.Privileges[0].Luid))
-		goto err;
 	if (!CreateWellKnownSid(WinLocalSystemSid, NULL, &expected_sid, &bytes))
 		goto err;
 
-	process_snapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
-	if (process_snapshot == INVALID_HANDLE_VALUE)
-		goto err;
-	for (ret = Process32First(process_snapshot, &entry); ret; last_error = GetLastError(), ret = Process32Next(process_snapshot, &entry)) {
-		if (strcasecmp(entry.szExeFile, "winlogon.exe"))
-			continue;
-
-		RevertToSelf();
-		if (!ImpersonateSelf(SecurityImpersonation))
-			continue;
-		if (!OpenThreadToken(GetCurrentThread(), TOKEN_ADJUST_PRIVILEGES, FALSE, &thread_token))
-			continue;
-		if (!AdjustTokenPrivileges(thread_token, FALSE, &privileges, sizeof(privileges), NULL, NULL)) {
-			last_error = GetLastError();
-			CloseHandle(thread_token);
-			continue;
-		}
-		CloseHandle(thread_token);
-
-		winlogon_process = OpenProcess(PROCESS_QUERY_INFORMATION, FALSE, entry.th32ProcessID);
-		if (!winlogon_process)
-			continue;
-		if (!OpenProcessToken(winlogon_process, TOKEN_IMPERSONATE | TOKEN_DUPLICATE, &winlogon_token))
-			continue;
-		CloseHandle(winlogon_process);
-		if (!DuplicateToken(winlogon_token, SecurityImpersonation, &duplicated_token)) {
-			last_error = GetLastError();
-			RevertToSelf();
-			continue;
-		}
-		CloseHandle(winlogon_token);
-		if (!SetThreadToken(NULL, duplicated_token)) {
-			last_error = GetLastError();
-			CloseHandle(duplicated_token);
-			continue;
-		}
-		CloseHandle(duplicated_token);
-
-		snprintf(fname, sizeof(fname), "\\\\.\\pipe\\ProtectedPrefix\\Administrators\\WireGuard\\%s", iface);
-		pipe_handle = CreateFile(fname, GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL);
-		last_error = GetLastError();
-		if (pipe_handle == INVALID_HANDLE_VALUE)
-			continue;
-		last_error = GetSecurityInfo(pipe_handle, SE_FILE_OBJECT, OWNER_SECURITY_INFORMATION, &pipe_sid, NULL, NULL, NULL, &pipe_sd);
-		if (last_error != ERROR_SUCCESS) {
-			CloseHandle(pipe_handle);
-			continue;
-		}
-		last_error = EqualSid(&expected_sid, pipe_sid) ? ERROR_SUCCESS : ERROR_ACCESS_DENIED;
-		LocalFree(pipe_sd);
-		if (last_error != ERROR_SUCCESS) {
-			CloseHandle(pipe_handle);
-			continue;
-		}
-		last_error = ERROR_SUCCESS;
-		break;
-	}
-	RevertToSelf();
-	CloseHandle(process_snapshot);
-
-	if (last_error != ERROR_SUCCESS || pipe_handle == INVALID_HANDLE_VALUE)
+	snprintf(fname, sizeof(fname), "\\\\.\\pipe\\ProtectedPrefix\\Administrators\\WireGuard\\%s", iface);
+	pipe_handle = CreateFileA(fname, GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL);
+	if (pipe_handle == INVALID_HANDLE_VALUE)
 		goto err;
+	if (GetSecurityInfo(pipe_handle, SE_FILE_OBJECT, OWNER_SECURITY_INFORMATION, &pipe_sid, NULL, NULL, NULL, &pipe_sd) != ERROR_SUCCESS)
+		goto err_close;
+	equal = EqualSid(&expected_sid, pipe_sid);
+	LocalFree(pipe_sd);
+	if (!equal)
+		goto err_close;
 	fd = _open_osfhandle((intptr_t)pipe_handle, _O_RDWR);
 	if (fd == -1) {
-		last_error = GetLastError();
 		CloseHandle(pipe_handle);
-		goto err;
+		return NULL;
 	}
 	return _fdopen(fd, "r+");
-
+err_close:
+	CloseHandle(pipe_handle);
 err:
-	if (last_error == ERROR_SUCCESS)
-		last_error = GetLastError();
-	if (last_error == ERROR_SUCCESS)
-		last_error = ERROR_ACCESS_DENIED;
-	FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, NULL, last_error, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), error_message, sizeof(error_message) - 1, NULL);
-	fprintf(stderr, "Error: Unable to open IPC handle via SYSTEM impersonation: %ld: %s\n", last_error, error_message);
 	errno = EACCES;
 	return NULL;
 }
diff --git a/src/ipc-windows.h b/src/ipc-windows.h
index 2382847..9c72a62 100644
--- a/src/ipc-windows.h
+++ b/src/ipc-windows.h
@@ -311,66 +311,6 @@ skip:;
 	return handle;
 }
 
-static BOOL elevated_ioctl(HANDLE handle, DWORD code, void *in_buf, DWORD in_buf_len, void *out_buf, DWORD out_buf_len, DWORD *bytes_returned)
-{
-	HANDLE thread_token, process_snapshot, winlogon_process, winlogon_token, duplicated_token;
-	PROCESSENTRY32 entry = { .dwSize = sizeof(PROCESSENTRY32) };
-	TOKEN_PRIVILEGES privileges = {
-		.PrivilegeCount = 1,
-		.Privileges = {{ .Attributes = SE_PRIVILEGE_ENABLED }}
-	};
-	SID expected_sid;
-	DWORD bytes = sizeof(expected_sid);
-	BOOL ret;
-
-	if (!LookupPrivilegeValue(NULL, SE_DEBUG_NAME, &privileges.Privileges[0].Luid))
-		return FALSE;
-	if (!CreateWellKnownSid(WinLocalSystemSid, NULL, &expected_sid, &bytes))
-		return FALSE;
-
-	process_snapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
-	if (process_snapshot == INVALID_HANDLE_VALUE)
-		return FALSE;
-	for (ret = Process32First(process_snapshot, &entry); ret; ret = Process32Next(process_snapshot, &entry)) {
-		if (strcasecmp(entry.szExeFile, "winlogon.exe"))
-			continue;
-
-		RevertToSelf();
-		if (!ImpersonateSelf(SecurityImpersonation))
-			continue;
-		if (!OpenThreadToken(GetCurrentThread(), TOKEN_ADJUST_PRIVILEGES, FALSE, &thread_token))
-			continue;
-		if (!AdjustTokenPrivileges(thread_token, FALSE, &privileges, sizeof(privileges), NULL, NULL)) {
-			CloseHandle(thread_token);
-			continue;
-		}
-		CloseHandle(thread_token);
-
-		winlogon_process = OpenProcess(PROCESS_QUERY_INFORMATION, FALSE, entry.th32ProcessID);
-		if (!winlogon_process)
-			continue;
-		if (!OpenProcessToken(winlogon_process, TOKEN_IMPERSONATE | TOKEN_DUPLICATE, &winlogon_token))
-			continue;
-		CloseHandle(winlogon_process);
-		if (!DuplicateToken(winlogon_token, SecurityImpersonation, &duplicated_token)) {
-			RevertToSelf();
-			continue;
-		}
-		CloseHandle(winlogon_token);
-		if (!SetThreadToken(NULL, duplicated_token)) {
-			CloseHandle(duplicated_token);
-			continue;
-		}
-		CloseHandle(duplicated_token);
-		ret = DeviceIoControl(handle, code, in_buf, in_buf_len, out_buf, out_buf_len, bytes_returned, NULL);
-		break;
-	}
-
-	RevertToSelf();
-	CloseHandle(process_snapshot);
-	return ret;
-}
-
 static int kernel_get_device(struct wgdevice **device, const char *iface)
 {
 	WG_IOCTL_INTERFACE *wg_iface;
@@ -389,10 +329,10 @@ static int kernel_get_device(struct wgdevice **device, const char *iface)
 	if (!handle)
 		return -errno;
 
-	while (!elevated_ioctl(handle, WG_IOCTL_GET, NULL, 0, buf, buf_len, &buf_len)) {
+	while (!DeviceIoControl(handle, WG_IOCTL_GET, NULL, 0, buf, buf_len, &buf_len, NULL)) {
 		free(buf);
 		if (GetLastError() != ERROR_MORE_DATA) {
-			errno = EIO;
+			errno = EACCES;
 			return -errno;
 		}
 		buf = malloc(buf_len);
@@ -500,10 +440,10 @@ out:
 
 static int kernel_set_device(struct wgdevice *dev)
 {
-	WG_IOCTL_INTERFACE *wg_iface;
+	WG_IOCTL_INTERFACE *wg_iface = NULL;
 	WG_IOCTL_PEER *wg_peer;
 	WG_IOCTL_ALLOWED_IP *wg_aip;
-	size_t buf_len = sizeof(WG_IOCTL_INTERFACE);
+	DWORD buf_len = sizeof(WG_IOCTL_INTERFACE);
 	HANDLE handle = kernel_interface_handle(dev->name);
 	struct wgpeer *peer;
 	struct wgallowedip *aip;
@@ -514,13 +454,22 @@ static int kernel_set_device(struct wgdevice *dev)
 		return -errno;
 
 	for_each_wgpeer(dev, peer) {
+		if (DWORD_MAX - buf_len < sizeof(WG_IOCTL_PEER)) {
+			errno = EOVERFLOW;
+			goto out;
+		}
 		buf_len += sizeof(WG_IOCTL_PEER);
-		for_each_wgallowedip(peer, aip)
+		for_each_wgallowedip(peer, aip) {
+			if (DWORD_MAX - buf_len < sizeof(WG_IOCTL_ALLOWED_IP)) {
+				errno = EOVERFLOW;
+				goto out;
+			}
 			buf_len += sizeof(WG_IOCTL_ALLOWED_IP);
+		}
 	}
 	wg_iface = calloc(1, buf_len);
 	if (!wg_iface)
-		return -errno;
+		goto out;
 
 	if (dev->flags & WGDEVICE_HAS_PRIVATE_KEY) {
 		memcpy(wg_iface->PrivateKey, dev->private_key, sizeof(wg_iface->PrivateKey));
@@ -586,8 +535,10 @@ static int kernel_set_device(struct wgdevice *dev)
 	}
 	wg_iface->PeersCount = peer_count;
 
-	if (!elevated_ioctl(handle, WG_IOCTL_SET, NULL, 0, wg_iface, buf_len, &buf_len))
+	if (!DeviceIoControl(handle, WG_IOCTL_SET, NULL, 0, wg_iface, buf_len, &buf_len, NULL)) {
+		errno = EACCES;
 		goto out;
+	}
 	errno = 0;
 
 out: