fix crash in check_pdh

filled buffer must use the actual sizeOf to be large enough.

Author: sni

Changes

@@ -3,6 +3,7 @@ This file documents the revision history for the SNClient agent.
 next:
          - change showing performance data in check_files and check_services (#243)
          - kill orphanded managed exporters which might block listen ports
+         - fix crash in check_pdh
 
 0.34     Wed May 28 13:56:57 CEST 2025
          - add /api/v1/admin/csr endpoint to create csr

go.mod

@@ -1,6 +1,6 @@
 module github.com/consol-monitoring/snclient
 
-go 1.23.8
+go 1.23.10
 
 require (
 	github.com/beevik/ntp v1.4.3
@@ -9,6 +9,7 @@ require (
 	github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc
 	github.com/go-chi/chi/v5 v5.2.1
 	github.com/go-ole/go-ole v1.3.0
+	github.com/goccy/go-json v0.10.5
 	github.com/kdar/factorlog v0.0.0-20211012144011-6ea75a169038
 	github.com/mackerelio/checkers v0.2.0
 	github.com/miekg/dns v1.1.66

go.sum

@@ -26,6 +26,8 @@ github.com/go-chi/chi/v5 v5.2.1/go.mod h1:L2yAIGWB3H+phAw1NxKwWM+7eUH/lU8pOMm5hH
 github.com/go-ole/go-ole v1.2.6/go.mod h1:pprOEPIfldk/42T2oK7lQ4v4JSDwmV0As9GaiUsvbm0=
 github.com/go-ole/go-ole v1.3.0 h1:Dt6ye7+vXGIKZ7Xtk4s6/xVdGDQynvom7xCFEdWr6uE=
 github.com/go-ole/go-ole v1.3.0/go.mod h1:5LS6F96DhAwUc7C+1HLexzMXY1xGRSryjyPPKW6zv78=
+github.com/goccy/go-json v0.10.5 h1:Fq85nIqj+gXn/S5ahsiTlK3TmC85qgirsdTP/+DeaC4=
+github.com/goccy/go-json v0.10.5/go.mod h1:oq7eo15ShAhp70Anwd5lgX2pLfOS3QCiwU/PULtXL6M=
 github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
 github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
 github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2s0bqwp9tc8=

pkg/snclient/check_omd.go

@@ -3,7 +3,6 @@ package snclient
 import (
 	"bytes"
 	"context"
-	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
@@ -15,6 +14,7 @@ import (
 	"time"
 
 	"github.com/consol-monitoring/snclient/pkg/convert"
+	"github.com/goccy/go-json"
 )
 
 func init() {

pkg/snclient/check_pdh_windows.go

@@ -7,11 +7,14 @@ import (
 	"strconv"
 	"strings"
 	"time"
+	"unsafe"
 
 	"github.com/consol-monitoring/snclient/pkg/pdh"
 	"golang.org/x/sys/windows"
 )
 
+const querySleepDuration = 500 * time.Millisecond
+
 type PdhValue struct {
 	CounterInstance string
 	Value           int64
@@ -29,12 +32,11 @@ func (c *CheckPDH) check(_ context.Context, _ *Agent, check *CheckData, args []A
 	var possiblePaths []string
 	var hQuery pdh.PDH_HQUERY
 	// Open Query  - Data Source = 0 => Real Time Datasource
-	ret := pdh.PdhOpenQuery(uintptr(0), uintptr(0), &hQuery)
-	defer pdh.PdhCloseQuery(hQuery)
-
+	ret := pdh.PdhOpenQuery(0, 0, &hQuery)
 	if ret != pdh.ERROR_SUCCESS {
 		return nil, fmt.Errorf("could not open query, something is wrong with the countername")
 	}
+	defer pdh.PdhCloseQuery(hQuery)
 
 	tmpPath := c.CounterPath
 	if c.EnglishFallBackNames {
@@ -168,7 +170,7 @@ func collectQueryData(hQuery *pdh.PDH_HQUERY) uint32 {
 		return ret
 	}
 	// PDH requires a double collection with a second wait between the calls See MSDN
-	time.Sleep(time.Duration(1))
+	time.Sleep(querySleepDuration)
 	ret = pdh.PdhCollectQueryData(*hQuery)
 
 	return ret
@@ -180,26 +182,24 @@ func collectQueryData(hQuery *pdh.PDH_HQUERY) uint32 {
 - if More Data -> Create Actual Array and fill
 */
 func collectLargeValuesArray(hCounter pdh.PDH_HCOUNTER, hQuery pdh.PDH_HQUERY) (values []PdhValue, apiResponseCode uint32) {
-	var resArr [1]pdh.PDH_FMT_COUNTERVALUE_ITEM_LARGE // Need at least one nil pointer
-	var ret uint32
-	var filledBuf []pdh.PDH_FMT_COUNTERVALUE_ITEM_LARGE
-	size := uint32(0)
-	bufferCount := uint32(0)
+	var bufCount uint32
+	var bufSize uint32
+	size := uint32(unsafe.Sizeof(pdh.PDH_FMT_COUNTERVALUE_ITEM_LARGE{}))
+	var emptyBuf [1]pdh.PDH_FMT_COUNTERVALUE_ITEM_LARGE // need at least 1 addressable null ptr.
 	if res := collectQueryData(&hQuery); res != pdh.ERROR_SUCCESS {
 		return nil, res
 	}
-	if ret = pdh.PdhGetFormattedCounterArrayLarge(hCounter, &size, &bufferCount, &resArr[0]); ret == pdh.PDH_MORE_DATA {
-		// create array of size = bufferCount * sizeOf(pdh.PDH_FMT_COUNTERVALUE_ITEM_LARGE)
-		filledBuf = make([]pdh.PDH_FMT_COUNTERVALUE_ITEM_LARGE, bufferCount)
-		ret = pdh.PdhGetFormattedCounterArrayLarge(hCounter, &size, &bufferCount, &filledBuf[0])
-	}
-	returnArray := make([]PdhValue, 0, bufferCount)
-	for _, pdhVal := range filledBuf {
-		returnArray = append(returnArray, PdhValue{
-			CounterInstance: windows.UTF16PtrToString(pdhVal.SzName),
-			Value:           pdhVal.FmtValue.LargeValue,
-		})
+	returnArray := []PdhValue{}
+	if ret := pdh.PdhGetFormattedCounterArrayLarge(hCounter, &bufSize, &bufCount, &emptyBuf[0]); ret == pdh.PDH_MORE_DATA {
+		filledBuf := make([]pdh.PDH_FMT_COUNTERVALUE_ITEM_LARGE, bufCount*size)
+		pdh.PdhGetFormattedCounterArrayLarge(hCounter, &bufSize, &bufCount, &filledBuf[0])
+		for i := range int(bufCount) {
+			returnArray = append(returnArray, PdhValue{
+				CounterInstance: windows.UTF16PtrToString(filledBuf[i].SzName),
+				Value:           filledBuf[i].FmtValue.LargeValue,
+			})
+		}
 	}
 
-	return returnArray, ret
+	return returnArray, pdh.ERROR_SUCCESS
 }

pkg/snclient/check_tasksched_windows.go

@@ -5,11 +5,12 @@ package snclient
 import (
 	"context"
 	_ "embed"
-	"encoding/json"
 	"fmt"
 	"strconv"
 	"syscall"
 	"time"
+
+	"github.com/goccy/go-json"
 )
 
 //go:embed embed/scripts/windows/scheduled_tasks.ps1

pkg/snclient/commands/inventory.go

@@ -2,10 +2,10 @@ package commands
 
 import (
 	"context"
-	"encoding/json"
 	"fmt"
 
 	"github.com/consol-monitoring/snclient/pkg/snclient"
+	"github.com/goccy/go-json"
 	"github.com/spf13/cobra"
 )
 

pkg/snclient/listen_exporterexporter.go

@@ -238,7 +238,7 @@ func (l *HandlerExporterExporter) listModules(res http.ResponseWriter, req *http
 	switch req.Header.Get("Accept") {
 	case "application/json":
 		log.Debugf("Listing modules in json")
-		moduleJSON, err := json.Marshal(l.modules) //nolint:musttag // no idea what this linter wants to have tagged
+		moduleJSON, err := json.Marshal(l.modules)
 		if err != nil {
 			log.Error(err)
 			http.Error(res, "Failed to produce JSON", http.StatusInternalServerError)

pkg/snclient/listen_web.go

@@ -1,7 +1,6 @@
 package snclient
 
 import (
-	"encoding/json"
 	"fmt"
 	"net/http"
 	"net/url"
@@ -10,6 +9,7 @@ import (
 
 	"github.com/consol-monitoring/snclient/pkg/utils"
 	"github.com/go-chi/chi/v5"
+	"github.com/goccy/go-json"
 )
 
 func init() {
@@ -369,7 +369,7 @@ type HandlerWebLegacy struct {
 func (l *HandlerWebLegacy) ServeHTTP(res http.ResponseWriter, req *http.Request) {
 	command := chi.URLParam(req, "command")
 	result := l.Handler.runCheck(req, command)
-	data, err := json.Marshal(map[string]interface{}{
+	jsonData := map[string]interface{}{
 		"payload": []interface{}{
 			map[string]interface{}{
 				"command": command,
@@ -382,7 +382,8 @@ func (l *HandlerWebLegacy) ServeHTTP(res http.ResponseWriter, req *http.Request)
 				},
 			},
 		},
-	})
+	}
+	data, err := json.Marshal(jsonData)
 	if err != nil {
 		msg := fmt.Sprintf("json error: %s", err.Error())
 		log.Errorf("%s", msg)
@@ -440,11 +441,12 @@ func (l *HandlerWebV1) serveCommand(res http.ResponseWriter, req *http.Request)
 	command := chi.URLParam(req, "command")
 	result := l.Handler.runCheck(req, command)
 	res.Header().Set("Content-Type", "application/json")
-	data, err := json.Marshal(map[string]interface{}{
+	jsonData := map[string]interface{}{
 		"command": command,
 		"result":  result.State,
 		"lines":   l.Handler.result2V1(result),
-	})
+	}
+	data, err := json.Marshal(jsonData)
 	if err != nil {
 		msg := fmt.Sprintf("json error: %s", err.Error())
 		log.Errorf("%s", msg)

pkg/snclient/listen_web_admin.go

@@ -6,13 +6,14 @@ import (
 	"crypto/x509"
 	"crypto/x509/pkix"
 	"encoding/base64"
-	"encoding/json"
 	"encoding/pem"
 	"fmt"
 	"net/http"
 	"os"
 	"strings"
 	"syscall"
+
+	"github.com/goccy/go-json"
 )
 
 func init() {