[release-branch.go1.10] crypto/tls: copy and use adjusted syscall.CertChainPolicyPara

As discussed in issue #21376, it is unsafe to have
syscall.CertChainPolicyPara.ExtraPolicyPara uintptr -
it has to be a pointer type. So copy syscall.CertChainPolicyPara
into crypto/tls package, make ExtraPolicyPara unsafe.Pointer,
and use new struct instead of syscall.CertChainPolicyPara.

Fixes #25033

Change-Id: If914af056cbbb0c4d93ffaa915b3d2cb5ecad0cd
Reviewed-on: https://go-review.googlesource.com/111715
Reviewed-by: Austin Clements <[email protected]>
Run-TryBot: Austin Clements <[email protected]>

Author: alexbrainman

src/crypto/x509/root_windows.go

@@ -95,6 +95,12 @@ func checkChainTrustStatus(c *Certificate, chainCtx *syscall.CertChainContext) e
 	return nil
 }
 
+type _CertChainPolicyPara struct {
+	Size            uint32
+	Flags           uint32
+	ExtraPolicyPara unsafe.Pointer
+}
+
 // checkChainSSLServerPolicy checks that the certificate chain in chainCtx is valid for
 // use as a certificate chain for a SSL/TLS server.
 func checkChainSSLServerPolicy(c *Certificate, chainCtx *syscall.CertChainContext, opts *VerifyOptions) error {
@@ -108,13 +114,13 @@ func checkChainSSLServerPolicy(c *Certificate, chainCtx *syscall.CertChainContex
 	}
 	sslPara.Size = uint32(unsafe.Sizeof(*sslPara))
 
-	para := &syscall.CertChainPolicyPara{
-		ExtraPolicyPara: uintptr(unsafe.Pointer(sslPara)),
+	para := &_CertChainPolicyPara{
+		ExtraPolicyPara: unsafe.Pointer(sslPara),
 	}
 	para.Size = uint32(unsafe.Sizeof(*para))
 
 	status := syscall.CertChainPolicyStatus{}
-	err = syscall.CertVerifyCertificateChainPolicy(syscall.CERT_CHAIN_POLICY_SSL, chainCtx, para, &status)
+	err = syscall.CertVerifyCertificateChainPolicy(syscall.CERT_CHAIN_POLICY_SSL, chainCtx, (*syscall.CertChainPolicyPara)(unsafe.Pointer(para)), &status)
 	if err != nil {
 		return err
 	}