1 files changed, 8 insertions, 32 deletions
diff --git a/src/crypto/rand/rand_windows.go b/src/crypto/rand/rand_windows.go
index 78a4ed6d67..8b2c960906 100644
--- a/src/crypto/rand/rand_windows.go
+++ b/src/crypto/rand/rand_windows.go
@@ -9,48 +9,24 @@ package rand
 
 import (
 	"os"
-	"sync"
-	"sync/atomic"
 	"syscall"
-	"time"
 )
 
-// Implemented by using Windows CryptoAPI 2.0.
-
 func init() { Reader = &rngReader{} }
 
-// A rngReader satisfies reads by reading from the Windows CryptGenRandom API.
-type rngReader struct {
-	used int32 // atomic; whether this rngReader has been used
-	prov syscall.Handle
-	mu   sync.Mutex
-}
+type rngReader struct{}
 
 func (r *rngReader) Read(b []byte) (n int, err error) {
-	if atomic.CompareAndSwapInt32(&r.used, 0, 1) {
-		// First use of randomness. Start timer to warn about
-		// being blocked on entropy not being available.
-		t := time.AfterFunc(60*time.Second, warnBlocked)
-		defer t.Stop()
-	}
-	r.mu.Lock()
-	if r.prov == 0 {
-		const provType = syscall.PROV_RSA_FULL
-		const flags = syscall.CRYPT_VERIFYCONTEXT | syscall.CRYPT_SILENT
-		err := syscall.CryptAcquireContext(&r.prov, nil, nil, provType, flags)
-		if err != nil {
-			r.mu.Unlock()
-			return 0, os.NewSyscallError("CryptAcquireContext", err)
-		}
-	}
-	r.mu.Unlock()
+	// RtlGenRandom only accepts 2**32-1 bytes at a time, so truncate.
+	inputLen := uint32(len(b))
 
-	if len(b) == 0 {
+	if inputLen == 0 {
 		return 0, nil
 	}
-	err = syscall.CryptGenRandom(r.prov, uint32(len(b)), &b[0])
+
+	err = syscall.RtlGenRandom(&b[0], inputLen)
 	if err != nil {
-		return 0, os.NewSyscallError("CryptGenRandom", err)
+		return 0, os.NewSyscallError("RtlGenRandom", err)
 	}
-	return len(b), nil
+	return int(inputLen), nil
 }