control/controlclient: support certstore without cgo

We no longer build Windows releases with cgo enabled, which
automatically turned off certstore support. Rather than re-enabling cgo,
we updated our fork of the certstore package to no longer require cgo.
This updates the package, cleans up how the feature is configured, and
removes the cgo build tag requirement.

Fixes tailscale/corp#14797
Fixes tailscale/coral#118

Change-Id: Iaea34340761c0431d759370532c16a48c0913374
Signed-off-by: Adrian Dewhurst <adrian@tailscale.com>

Author: sailorfrag

cmd/tailscaled/depaware.txt

@@ -133,7 +133,6 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
    L    github.com/pierrec/lz4/v4/internal/lz4errors                 from github.com/pierrec/lz4/v4+
    L    github.com/pierrec/lz4/v4/internal/lz4stream                 from github.com/pierrec/lz4/v4
    L    github.com/pierrec/lz4/v4/internal/xxh32                     from github.com/pierrec/lz4/v4/internal/lz4stream
-   W    github.com/pkg/errors                                        from github.com/tailscale/certstore
   LD    github.com/pkg/sftp                                          from tailscale.com/ssh/tailssh
   LD    github.com/pkg/sftp/internal/encoding/ssh/filexfer           from github.com/pkg/sftp
    W 💣 github.com/tailscale/certstore                               from tailscale.com/control/controlclient
@@ -367,7 +366,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/util/testenv                                   from tailscale.com/ipn/ipnlocal+
         tailscale.com/util/uniq                                      from tailscale.com/wgengine/magicsock+
         tailscale.com/util/vizerror                                  from tailscale.com/types/ipproto+
-     💣 tailscale.com/util/winutil                                   from tailscale.com/control/controlclient+
+     💣 tailscale.com/util/winutil                                   from tailscale.com/clientupdate+
    W 💣 tailscale.com/util/winutil/authenticode                      from tailscale.com/util/osdiag+
    W    tailscale.com/util/winutil/policy                            from tailscale.com/ipn/ipnlocal
         tailscale.com/version                                        from tailscale.com/derp+

control/controlclient/sign_supported.go

@@ -1,11 +1,9 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
-//go:build windows && cgo
+//go:build windows
 
-// darwin,cgo is also supported by certstore but machineCertificateSubject will
-// need to be loaded by a different mechanism, so this is not currently enabled
-// on darwin.
+// darwin,cgo is also supported by certstore but untested, so it is not enabled.
 
 package controlclient
 
@@ -21,7 +19,7 @@ import (
 	"github.com/tailscale/certstore"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/key"
-	"tailscale.com/util/winutil"
+	"tailscale.com/util/syspolicy"
 )
 
 var getMachineCertificateSubjectOnce struct {
@@ -40,7 +38,7 @@ var getMachineCertificateSubjectOnce struct {
 // Example: "CN=Tailscale Inc Test Root CA,OU=Tailscale Inc Test Certificate Authority,O=Tailscale Inc,ST=ON,C=CA"
 func getMachineCertificateSubject() string {
 	getMachineCertificateSubjectOnce.Do(func() {
-		getMachineCertificateSubjectOnce.v, _ = winutil.GetRegString("MachineCertificateSubject")
+		getMachineCertificateSubjectOnce.v, _ = syspolicy.GetString("MachineCertificateSubject", "")
 	})
 
 	return getMachineCertificateSubjectOnce.v

control/controlclient/sign_unsupported.go

@@ -1,7 +1,7 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
-//go:build !windows || !cgo
+//go:build !windows
 
 package controlclient
 

go.mod

@@ -58,7 +58,7 @@ require (
 	github.com/prometheus/client_golang v1.17.0
 	github.com/prometheus/common v0.44.0
 	github.com/skip2/go-qrcode v0.0.0-20200617195104-da1b6568686e
-	github.com/tailscale/certstore v0.1.1-0.20220316223106-78d6e1c49d8d
+	github.com/tailscale/certstore v0.1.1-0.20231020161753-77811a65f4ff
 	github.com/tailscale/depaware v0.0.0-20210622194025-720c4b409502
 	github.com/tailscale/goexpect v0.0.0-20210902213824-6e8c725cea41
 	github.com/tailscale/golang-x-crypto v0.0.0-20230713185742-f0b76a10a08e

go.sum

@@ -864,8 +864,8 @@ github.com/subosito/gotenv v1.4.2 h1:X1TuBLAMDFbaTAChgCBLu3DU3UPyELpnF2jjJ2cz/S8
 github.com/subosito/gotenv v1.4.2/go.mod h1:ayKnFf/c6rvx/2iiLrJUk1e6plDbT3edrFNGqEflhK0=
 github.com/t-yuki/gocover-cobertura v0.0.0-20180217150009-aaee18c8195c h1:+aPplBwWcHBo6q9xrfWdMrT9o4kltkmmvpemgIjep/8=
 github.com/t-yuki/gocover-cobertura v0.0.0-20180217150009-aaee18c8195c/go.mod h1:SbErYREK7xXdsRiigaQiQkI9McGRzYMvlKYaP3Nimdk=
-github.com/tailscale/certstore v0.1.1-0.20220316223106-78d6e1c49d8d h1:K3j02b5j2Iw1xoggN9B2DIEkhWGheqFOeDkdJdBrJI8=
-github.com/tailscale/certstore v0.1.1-0.20220316223106-78d6e1c49d8d/go.mod h1:2P+hpOwd53e7JMX/L4f3VXkv1G+33ES6IWZSrkIeWNs=
+github.com/tailscale/certstore v0.1.1-0.20231020161753-77811a65f4ff h1:vnxdYZUJbsSRcIcduDW3DcQqfqaiv4FUgy25q8X+vfI=
+github.com/tailscale/certstore v0.1.1-0.20231020161753-77811a65f4ff/go.mod h1:XrBNfAFN+pwoWuksbFS9Ccxnopa15zJGgXRFN90l3K4=
 github.com/tailscale/depaware v0.0.0-20210622194025-720c4b409502 h1:34icjjmqJ2HPjrSuJYEkdZ+0ItmGQAQ75cRHIiftIyE=
 github.com/tailscale/depaware v0.0.0-20210622194025-720c4b409502/go.mod h1:p9lPsd+cx33L3H9nNoecRRxPssFKUwwI50I3pZ0yT+8=
 github.com/tailscale/goexpect v0.0.0-20210902213824-6e8c725cea41 h1:/V2rCMMWcsjYaYO2MeovLw+ClP63OtXgCF2Y1eb8+Ns=