os: use CreateFile for Stat of symlinks

Stat uses Windows FindFirstFile + CreateFile to gather symlink
information - FindFirstFile determines if file is a symlink,
and then CreateFile follows symlink to capture target details.

Lstat only uses FindFirstFile.

This CL replaces current approach with just a call to CreateFile.
Lstat uses FILE_FLAG_OPEN_REPARSE_POINT flag, that instructs
CreateFile not to follow symlink. Other than that both Stat and
Lstat look the same now. New code is simpler.

CreateFile + GetFileInformationByHandle (unlike FindFirstFile)
does not report reparse tag of a file. I tried to ignore reparse
tag altogether. And it works for symlinks and mount points.
Unfortunately (see https://github.com/moby/moby/issues/37026),
files on deduped disk volumes are reported with
FILE_ATTRIBUTE_REPARSE_POINT attribute set and reparse tag set
to IO_REPARSE_TAG_DEDUP. So, if we ignore reparse tag, Lstat
interprets deduped volume files as symlinks. That is incorrect.
So I had to add GetFileInformationByHandleEx call to gather
reparse tag after calling CreateFile and GetFileInformationByHandle.

Fixes #27225
Fixes #27515

Change-Id: If60233bcf18836c147597cc17450d82f3f88c623
Reviewed-on: https://go-review.googlesource.com/c/143578
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Kirill Kolyshkin <kolyshkin@gmail.com>

3 files changed, 61 insertions, 23 deletions

diff --git a/src/internal/syscall/windows/mksyscall.go b/src/internal/syscall/windows/mksyscall.go
index 23efb6a01a..a8edafb3c3 100644
--- a/src/internal/syscall/windows/mksyscall.go
+++ b/src/internal/syscall/windows/mksyscall.go
@@ -4,4 +4,4 @@
 
 package windows
 
-//go:generate go run $GOROOT/src/syscall/mksyscall_windows.go -output zsyscall_windows.go syscall_windows.go security_windows.go psapi_windows.go
+//go:generate go run $GOROOT/src/syscall/mksyscall_windows.go -output zsyscall_windows.go syscall_windows.go security_windows.go psapi_windows.go symlink_windows.go
diff --git a/src/internal/syscall/windows/symlink_windows.go b/src/internal/syscall/windows/symlink_windows.go
index cc2163e933..b64d058d13 100644
--- a/src/internal/syscall/windows/symlink_windows.go
+++ b/src/internal/syscall/windows/symlink_windows.go
@@ -11,4 +11,29 @@ const (
 
 	// symlink support for CreateSymbolicLink() starting with Windows 10 (1703, v10.0.14972)
 	SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE = 0x2
+
+	// FileInformationClass values
+	FileBasicInfo                  = 0    // FILE_BASIC_INFO
+	FileStandardInfo               = 1    // FILE_STANDARD_INFO
+	FileNameInfo                   = 2    // FILE_NAME_INFO
+	FileStreamInfo                 = 7    // FILE_STREAM_INFO
+	FileCompressionInfo            = 8    // FILE_COMPRESSION_INFO
+	FileAttributeTagInfo           = 9    // FILE_ATTRIBUTE_TAG_INFO
+	FileIdBothDirectoryInfo        = 0xa  // FILE_ID_BOTH_DIR_INFO
+	FileIdBothDirectoryRestartInfo = 0xb  // FILE_ID_BOTH_DIR_INFO
+	FileRemoteProtocolInfo         = 0xd  // FILE_REMOTE_PROTOCOL_INFO
+	FileFullDirectoryInfo          = 0xe  // FILE_FULL_DIR_INFO
+	FileFullDirectoryRestartInfo   = 0xf  // FILE_FULL_DIR_INFO
+	FileStorageInfo                = 0x10 // FILE_STORAGE_INFO
+	FileAlignmentInfo              = 0x11 // FILE_ALIGNMENT_INFO
+	FileIdInfo                     = 0x12 // FILE_ID_INFO
+	FileIdExtdDirectoryInfo        = 0x13 // FILE_ID_EXTD_DIR_INFO
+	FileIdExtdDirectoryRestartInfo = 0x14 // FILE_ID_EXTD_DIR_INFO
 )
+
+type FILE_ATTRIBUTE_TAG_INFO struct {
+	FileAttributes uint32
+	ReparseTag     uint32
+}
+
+//sys	GetFileInformationByHandleEx(handle syscall.Handle, class uint32, info *byte, bufsize uint32) (err error)
diff --git a/src/internal/syscall/windows/zsyscall_windows.go b/src/internal/syscall/windows/zsyscall_windows.go
index 550a8a5bd4..2212697b1b 100644
--- a/src/internal/syscall/windows/zsyscall_windows.go
+++ b/src/internal/syscall/windows/zsyscall_windows.go
@@ -44,28 +44,29 @@ var (
 	moduserenv  = syscall.NewLazyDLL(sysdll.Add("userenv.dll"))
 	modpsapi    = syscall.NewLazyDLL(sysdll.Add("psapi.dll"))
 
-	procGetAdaptersAddresses      = modiphlpapi.NewProc("GetAdaptersAddresses")
-	procGetComputerNameExW        = modkernel32.NewProc("GetComputerNameExW")
-	procMoveFileExW               = modkernel32.NewProc("MoveFileExW")
-	procGetModuleFileNameW        = modkernel32.NewProc("GetModuleFileNameW")
-	procWSASocketW                = modws2_32.NewProc("WSASocketW")
-	procGetACP                    = modkernel32.NewProc("GetACP")
-	procGetConsoleCP              = modkernel32.NewProc("GetConsoleCP")
-	procMultiByteToWideChar       = modkernel32.NewProc("MultiByteToWideChar")
-	procGetCurrentThread          = modkernel32.NewProc("GetCurrentThread")
-	procNetShareAdd               = modnetapi32.NewProc("NetShareAdd")
-	procNetShareDel               = modnetapi32.NewProc("NetShareDel")
-	procGetFinalPathNameByHandleW = modkernel32.NewProc("GetFinalPathNameByHandleW")
-	procImpersonateSelf           = modadvapi32.NewProc("ImpersonateSelf")
-	procRevertToSelf              = modadvapi32.NewProc("RevertToSelf")
-	procOpenThreadToken           = modadvapi32.NewProc("OpenThreadToken")
-	procLookupPrivilegeValueW     = modadvapi32.NewProc("LookupPrivilegeValueW")
-	procAdjustTokenPrivileges     = modadvapi32.NewProc("AdjustTokenPrivileges")
-	procDuplicateTokenEx          = modadvapi32.NewProc("DuplicateTokenEx")
-	procSetTokenInformation       = modadvapi32.NewProc("SetTokenInformation")
-	procGetProfilesDirectoryW     = moduserenv.NewProc("GetProfilesDirectoryW")
-	procNetUserGetLocalGroups     = modnetapi32.NewProc("NetUserGetLocalGroups")
-	procGetProcessMemoryInfo      = modpsapi.NewProc("GetProcessMemoryInfo")
+	procGetAdaptersAddresses         = modiphlpapi.NewProc("GetAdaptersAddresses")
+	procGetComputerNameExW           = modkernel32.NewProc("GetComputerNameExW")
+	procMoveFileExW                  = modkernel32.NewProc("MoveFileExW")
+	procGetModuleFileNameW           = modkernel32.NewProc("GetModuleFileNameW")
+	procWSASocketW                   = modws2_32.NewProc("WSASocketW")
+	procGetACP                       = modkernel32.NewProc("GetACP")
+	procGetConsoleCP                 = modkernel32.NewProc("GetConsoleCP")
+	procMultiByteToWideChar          = modkernel32.NewProc("MultiByteToWideChar")
+	procGetCurrentThread             = modkernel32.NewProc("GetCurrentThread")
+	procNetShareAdd                  = modnetapi32.NewProc("NetShareAdd")
+	procNetShareDel                  = modnetapi32.NewProc("NetShareDel")
+	procGetFinalPathNameByHandleW    = modkernel32.NewProc("GetFinalPathNameByHandleW")
+	procImpersonateSelf              = modadvapi32.NewProc("ImpersonateSelf")
+	procRevertToSelf                 = modadvapi32.NewProc("RevertToSelf")
+	procOpenThreadToken              = modadvapi32.NewProc("OpenThreadToken")
+	procLookupPrivilegeValueW        = modadvapi32.NewProc("LookupPrivilegeValueW")
+	procAdjustTokenPrivileges        = modadvapi32.NewProc("AdjustTokenPrivileges")
+	procDuplicateTokenEx             = modadvapi32.NewProc("DuplicateTokenEx")
+	procSetTokenInformation          = modadvapi32.NewProc("SetTokenInformation")
+	procGetProfilesDirectoryW        = moduserenv.NewProc("GetProfilesDirectoryW")
+	procNetUserGetLocalGroups        = modnetapi32.NewProc("NetUserGetLocalGroups")
+	procGetProcessMemoryInfo         = modpsapi.NewProc("GetProcessMemoryInfo")
+	procGetFileInformationByHandleEx = modkernel32.NewProc("GetFileInformationByHandleEx")
 )
 
 func GetAdaptersAddresses(family uint32, flags uint32, reserved uintptr, adapterAddresses *IpAdapterAddresses, sizePointer *uint32) (errcode error) {
@@ -321,3 +322,15 @@ func GetProcessMemoryInfo(handle syscall.Handle, memCounters *PROCESS_MEMORY_COU
 	}
 	return
 }
+
+func GetFileInformationByHandleEx(handle syscall.Handle, class uint32, info *byte, bufsize uint32) (err error) {
+	r1, _, e1 := syscall.Syscall6(procGetFileInformationByHandleEx.Addr(), 4, uintptr(handle), uintptr(class), uintptr(unsafe.Pointer(info)), uintptr(bufsize), 0, 0)
+	if r1 == 0 {
+		if e1 != 0 {
+			err = errnoErr(e1)
+		} else {
+			err = syscall.EINVAL
+		}
+	}
+	return
+}