crypto/rand,runtime: switch RtlGenRandom for ProcessPrng

RtlGenRandom is a semi-undocumented API, also known as
SystemFunction036, which we use to generate random data on Windows.
It's definition, in cryptbase.dll, is an opaque wrapper for the
documented API ProcessPrng. Instead of using RtlGenRandom, switch to
using ProcessPrng, since the former is simply a wrapper for the latter,
there should be no practical change on the user side, other than a minor
change in the DLLs we load.

Change-Id: Ie6891bf97b1d47f5368cccbe92f374dba2c2672a
Reviewed-on: https://go-review.googlesource.com/c/go/+/536235
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Quim Muntal <quimmuntal@gmail.com>
Auto-Submit: Roland Shoemaker <roland@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

2 files changed, 12 insertions, 11 deletions

diff --git a/src/internal/syscall/windows/syscall_windows.go b/src/internal/syscall/windows/syscall_windows.go
index ab4ad2ec64..5854ca60b5 100644
--- a/src/internal/syscall/windows/syscall_windows.go
+++ b/src/internal/syscall/windows/syscall_windows.go
@@ -373,7 +373,7 @@ func ErrorLoadingGetTempPath2() error {
 //sys	DestroyEnvironmentBlock(block *uint16) (err error) = userenv.DestroyEnvironmentBlock
 //sys	CreateEvent(eventAttrs *SecurityAttributes, manualReset uint32, initialState uint32, name *uint16) (handle syscall.Handle, err error) = kernel32.CreateEventW
 
-//sys	RtlGenRandom(buf []byte) (err error) = advapi32.SystemFunction036
+//sys	ProcessPrng(buf []byte) (err error) = bcryptprimitives.ProcessPrng
 
 type FILE_ID_BOTH_DIR_INFO struct {
 	NextEntryOffset uint32
diff --git a/src/internal/syscall/windows/zsyscall_windows.go b/src/internal/syscall/windows/zsyscall_windows.go
index e3f6d8d2a2..5a587ad4f1 100644
--- a/src/internal/syscall/windows/zsyscall_windows.go
+++ b/src/internal/syscall/windows/zsyscall_windows.go
@@ -37,13 +37,14 @@ func errnoErr(e syscall.Errno) error {
 }
 
 var (
-	modadvapi32 = syscall.NewLazyDLL(sysdll.Add("advapi32.dll"))
-	modiphlpapi = syscall.NewLazyDLL(sysdll.Add("iphlpapi.dll"))
-	modkernel32 = syscall.NewLazyDLL(sysdll.Add("kernel32.dll"))
-	modnetapi32 = syscall.NewLazyDLL(sysdll.Add("netapi32.dll"))
-	modpsapi    = syscall.NewLazyDLL(sysdll.Add("psapi.dll"))
-	moduserenv  = syscall.NewLazyDLL(sysdll.Add("userenv.dll"))
-	modws2_32   = syscall.NewLazyDLL(sysdll.Add("ws2_32.dll"))
+	modadvapi32         = syscall.NewLazyDLL(sysdll.Add("advapi32.dll"))
+	modbcryptprimitives = syscall.NewLazyDLL(sysdll.Add("bcryptprimitives.dll"))
+	modiphlpapi         = syscall.NewLazyDLL(sysdll.Add("iphlpapi.dll"))
+	modkernel32         = syscall.NewLazyDLL(sysdll.Add("kernel32.dll"))
+	modnetapi32         = syscall.NewLazyDLL(sysdll.Add("netapi32.dll"))
+	modpsapi            = syscall.NewLazyDLL(sysdll.Add("psapi.dll"))
+	moduserenv          = syscall.NewLazyDLL(sysdll.Add("userenv.dll"))
+	modws2_32           = syscall.NewLazyDLL(sysdll.Add("ws2_32.dll"))
 
 	procAdjustTokenPrivileges             = modadvapi32.NewProc("AdjustTokenPrivileges")
 	procDuplicateTokenEx                  = modadvapi32.NewProc("DuplicateTokenEx")
@@ -55,7 +56,7 @@ var (
 	procQueryServiceStatus                = modadvapi32.NewProc("QueryServiceStatus")
 	procRevertToSelf                      = modadvapi32.NewProc("RevertToSelf")
 	procSetTokenInformation               = modadvapi32.NewProc("SetTokenInformation")
-	procSystemFunction036                 = modadvapi32.NewProc("SystemFunction036")
+	procProcessPrng                       = modbcryptprimitives.NewProc("ProcessPrng")
 	procGetAdaptersAddresses              = modiphlpapi.NewProc("GetAdaptersAddresses")
 	procCreateEventW                      = modkernel32.NewProc("CreateEventW")
 	procGetACP                            = modkernel32.NewProc("GetACP")
@@ -179,12 +180,12 @@ func SetTokenInformation(tokenHandle syscall.Token, tokenInformationClass uint32
 	return
 }
 
-func RtlGenRandom(buf []byte) (err error) {
+func ProcessPrng(buf []byte) (err error) {
 	var _p0 *byte
 	if len(buf) > 0 {
 		_p0 = &buf[0]
 	}
-	r1, _, e1 := syscall.Syscall(procSystemFunction036.Addr(), 2, uintptr(unsafe.Pointer(_p0)), uintptr(len(buf)), 0)
+	r1, _, e1 := syscall.Syscall(procProcessPrng.Addr(), 2, uintptr(unsafe.Pointer(_p0)), uintptr(len(buf)), 0)
 	if r1 == 0 {
 		err = errnoErr(e1)
 	}