From 0443ad2b6ed839e8480e250a655001f7d403c9cb Mon Sep 17 00:00:00 2001
From: midipix <writeonce@midipix.org>
Date: May 09 2020 23:04:43 +0000
Subject: pe_get_device_dos_drive_letter(): open the drive, not the volume.


Opening the drive rather than the volume's top-level directory requires
reduced permissions, and so should always be preferred for as long as
it is sufficient.

This change, however, is also motivated by annoying media-drive driver
behavior of popping up a dialog (how awful) window whenever an allegedly
interactive application (that is, interactive by its subsystem) attempts
to access a directory (or a file) in the drive while it is empty.

---

diff --git a/src/internal/pe_os.h b/src/internal/pe_os.h
index 11e334b..6963613 100644
--- a/src/internal/pe_os.h
+++ b/src/internal/pe_os.h
@@ -29,6 +29,7 @@
 
 #define OS_FILE_DIRECTORY_FILE			0x00000001
 #define OS_FILE_NON_DIRECTORY_FILE		0x00000040
+#define OS_FILE_SYNCHRONOUS_IO_ALERT		0x00000010
 
 #define OS_FILE_SHARE_READ			0x00000001
 #define OS_FILE_SHARE_WRITE			0x00000002
diff --git a/src/ldso/pe_load_framework_loader.c b/src/ldso/pe_load_framework_loader.c
index 347d3ab..4595b99 100644
--- a/src/ldso/pe_load_framework_loader.c
+++ b/src/ldso/pe_load_framework_loader.c
@@ -34,7 +34,7 @@ static int32_t pe_get_device_dos_drive_letter(
 
 	wchar16_t		namebuf[8] = {
 				'\\','?','?','\\',
-				'X',':','\\',0};
+				'X',':',0};
 
 	unsigned char		letters[26] = {
 				'C','Z','Y','X','W','V',
@@ -54,7 +54,7 @@ static int32_t pe_get_device_dos_drive_letter(
 
 	/* path */
 	path.buffer = namebuf;
-	path.strlen = 7 * sizeof(wchar16_t);
+	path.strlen = 6 * sizeof(wchar16_t);
 	path.maxlen = 0;
 
 	/* oa */
@@ -72,13 +72,12 @@ static int32_t pe_get_device_dos_drive_letter(
 		status = zw_open_file(
 			&hdevice,
 			OS_SEC_SYNCHRONIZE
-				| OS_FILE_READ_ATTRIBUTES
-				| OS_FILE_READ_ACCESS,
+				| OS_FILE_READ_ATTRIBUTES,
 			&oa,&iosb,
 			OS_FILE_SHARE_READ
 				| OS_FILE_SHARE_WRITE
 				| OS_FILE_SHARE_DELETE,
-			OS_FILE_DIRECTORY_FILE);
+			OS_FILE_SYNCHRONOUS_IO_ALERT);
 
 		if (status == OS_STATUS_SUCCESS) {
 			status = zw_query_object(
@@ -92,17 +91,19 @@ static int32_t pe_get_device_dos_drive_letter(
 				src = devname;
 				dst = dpath->buffer;
 
-				idx = 0;
-				cap = devnamelen / sizeof(wchar16_t);
+				if (devnamelen == dpath->strlen) {
+					idx = 0;
+					cap = devnamelen / sizeof(wchar16_t);
 
-				for (; idx<cap && src[idx]==dst[idx]; )
-					idx++;
+					for (; idx<cap && src[idx]==dst[idx]; )
+						idx++;
 
-				if (idx==cap && dst[idx]=='\\') {
-					zw_close(hdevice);
-					*letter = letters[sigh];
+					if (idx==cap) {
+						zw_close(hdevice);
+						*letter = letters[sigh];
 
-					return OS_STATUS_SUCCESS;
+						return OS_STATUS_SUCCESS;
+					}
 				}
 			}