util/osdiag: add logging for winsock layered service providers to Windows bugreports

The Layered Service Provider (LSP) is a deprecated (but still supported)
mechanism for inserting user-mode DLLs into a filter chain between the
Winsock API surface (ie, ws2_32.dll) and the internal user-mode interface
to the networking stack.

While their use is becoming more rare due to the aforementioned deprecation,
it is still possible for third-party software to install their DLLs into
this filter chain and interfere with Winsock API calls. Knowing whether
this is happening is useful for troubleshooting.

Fixes https://github.com/tailscale/tailscale/issues/8142

Signed-off-by: Aaron Klotz <aaron@tailscale.com>

util/osdiag/osdiag_windows.go

@@ -22,6 +22,10 @@ import (
 	"tailscale.com/util/winutil/authenticode"
 )
 
+var (
+	errUnexpectedResult = errors.New("API call returned an unexpected value")
+)
+
 const (
 	maxBinaryValueLen  = 128   // we'll truncate any binary values longer than this
 	maxRegValueNameLen = 16384 // maximum length supported by Windows + 1
@@ -38,8 +42,9 @@ func logSupportInfo(logf logger.Logf, reason LogSupportInfoReason) {
 }
 
 const (
-	supportInfoKeyModules  = "modules"
-	supportInfoKeyRegistry = "registry"
+	supportInfoKeyModules    = "modules"
+	supportInfoKeyRegistry   = "registry"
+	supportInfoKeyWinsockLSP = "winsockLSP"
 )
 
 func getSupportInfo(w io.Writer, reason LogSupportInfoReason) error {
@@ -59,6 +64,13 @@ func getSupportInfo(w io.Writer, reason LogSupportInfoReason) error {
 		} else {
 			output[supportInfoKeyModules] = err
 		}
+
+		lspInfo, err := getWinsockLSPInfo()
+		if err == nil {
+			output[supportInfoKeyWinsockLSP] = lspInfo
+		} else {
+			output[supportInfoKeyWinsockLSP] = err
+		}
 	}
 
 	enc := json.NewEncoder(w)
@@ -228,8 +240,8 @@ func (mi *moduleInfo) setVersionInfo() {
 
 var errAssertingType = errors.New("asserting DataDirectory type")
 
-func (mi *moduleInfo) setDebugInfo(base uintptr, size uint32) {
-	pem, err := pe.NewPEFromBaseAddressAndSize(base, size)
+func (mi *moduleInfo) setDebugInfo() {
+	pem, err := pe.NewPEFromBaseAddressAndSize(mi.BaseAddress, mi.Size)
 	if err != nil {
 		mi.DebugInfoErr = err
 		return
@@ -320,7 +332,7 @@ func getModuleInfo() (map[string]moduleInfo, error) {
 		}
 
 		entry.setVersionInfo()
-		entry.setDebugInfo(base, size)
+		entry.setDebugInfo()
 		entry.setAuthenticodeInfo()
 
 		result[name] = entry
@@ -328,3 +340,145 @@ func getModuleInfo() (map[string]moduleInfo, error) {
 
 	return result, nil
 }
+
+type _WSC_PROVIDER_INFO_TYPE int32
+
+const (
+	providerInfoLspCategories _WSC_PROVIDER_INFO_TYPE = 0
+)
+
+const (
+	_SOCKET_ERROR = -1
+)
+
+// Note that wsaProtocolInfo needs to be identical to windows.WSAProtocolInfo;
+// the purpose of this type is to have the ability to use it as a reciever in
+// the path and categoryFlags funcs defined below.
+type wsaProtocolInfo windows.WSAProtocolInfo
+
+func (pi *wsaProtocolInfo) path() (string, error) {
+	var errno int32
+	var buf [windows.MAX_PATH]uint16
+	bufCount := int32(len(buf))
+	ret := wscGetProviderPath(&pi.ProviderId, &buf[0], &bufCount, &errno)
+	if ret == _SOCKET_ERROR {
+		return "", windows.Errno(errno)
+	}
+	if ret != 0 {
+		return "", errUnexpectedResult
+	}
+
+	return windows.UTF16ToString(buf[:bufCount]), nil
+}
+
+func (pi *wsaProtocolInfo) categoryFlags() (uint32, error) {
+	var errno int32
+	var result uint32
+	bufLen := uintptr(unsafe.Sizeof(result))
+	ret := wscGetProviderInfo(&pi.ProviderId, providerInfoLspCategories, unsafe.Pointer(&result), &bufLen, 0, &errno)
+	if ret == _SOCKET_ERROR {
+		return 0, windows.Errno(errno)
+	}
+	if ret != 0 {
+		return 0, errUnexpectedResult
+	}
+
+	return result, nil
+}
+
+type wsaProtocolInfoOutput struct {
+	Description     string   `json:"description,omitempty"`
+	Version         int32    `json:"version"`
+	AddressFamily   int32    `json:"addressFamily"`
+	SocketType      int32    `json:"socketType"`
+	Protocol        int32    `json:"protocol"`
+	ServiceFlags1   string   `json:"serviceFlags1"`
+	ProviderFlags   string   `json:"providerFlags"`
+	Path            string   `json:"path,omitempty"`
+	PathErr         error    `json:"pathErr,omitempty"`
+	Category        string   `json:"category,omitempty"`
+	CategoryErr     error    `json:"categoryErr,omitempty"`
+	BaseProviderID  string   `json:"baseProviderID,omitempty"`
+	LayerProviderID string   `json:"layerProviderID,omitempty"`
+	Chain           []uint32 `json:"chain,omitempty"`
+}
+
+func getWinsockLSPInfo() (map[uint32]wsaProtocolInfoOutput, error) {
+	protocols, err := enumWinsockProtocols()
+	if err != nil {
+		return nil, err
+	}
+
+	result := make(map[uint32]wsaProtocolInfoOutput, len(protocols))
+	for _, p := range protocols {
+		v := wsaProtocolInfoOutput{
+			Description:   windows.UTF16ToString(p.ProtocolName[:]),
+			Version:       p.Version,
+			AddressFamily: p.AddressFamily,
+			SocketType:    p.SocketType,
+			Protocol:      p.Protocol,
+			ServiceFlags1: fmt.Sprintf("0x%08X", p.ServiceFlags1), // Serializing as hex string to make the flags easier to decode by human inspection
+			ProviderFlags: fmt.Sprintf("0x%08X", p.ProviderFlags),
+		}
+
+		switch p.ProtocolChain.ChainLen {
+		case windows.BASE_PROTOCOL:
+			v.BaseProviderID = p.ProviderId.String()
+		case windows.LAYERED_PROTOCOL:
+			v.LayerProviderID = p.ProviderId.String()
+		default:
+			v.Chain = p.ProtocolChain.ChainEntries[:p.ProtocolChain.ChainLen]
+		}
+
+		// Queries that are only valid for base and layered protocols (not chains)
+		if v.Chain == nil {
+			path, err := p.path()
+			if err == nil {
+				v.Path = strings.ToLower(path)
+			} else {
+				v.PathErr = err
+			}
+
+			category, err := p.categoryFlags()
+			if err == nil {
+				v.Category = fmt.Sprintf("0x%08X", category)
+			} else if !errors.Is(err, windows.WSAEINVALIDPROVIDER) {
+				// WSAEINVALIDPROVIDER == "no category info found", so we only log
+				// errors other than that one.
+				v.CategoryErr = err
+			}
+		}
+
+		// Chains reference other providers using catalog entry IDs, so we use that
+		// value as the key in our map.
+		result[p.CatalogEntryId] = v
+	}
+
+	return result, nil
+}
+
+func enumWinsockProtocols() ([]wsaProtocolInfo, error) {
+	// Get the required size
+	var errno int32
+	var bytesReqd uint32
+	ret := wscEnumProtocols(nil, nil, &bytesReqd, &errno)
+	if ret != _SOCKET_ERROR {
+		return nil, errUnexpectedResult
+	}
+	if e := windows.Errno(errno); e != windows.WSAENOBUFS {
+		return nil, e
+	}
+
+	// Allocate
+	szEntry := uint32(unsafe.Sizeof(wsaProtocolInfo{}))
+	buf := make([]wsaProtocolInfo, bytesReqd/szEntry)
+
+	// Now do the query for real
+	bufLen := uint32(len(buf)) * szEntry
+	ret = wscEnumProtocols(nil, &buf[0], &bufLen, &errno)
+	if ret == _SOCKET_ERROR {
+		return nil, windows.Errno(errno)
+	}
+
+	return buf, nil
+}