feat(security): add sensitive data filtering for tool results sent to

LLM

Prevent LLM from seeing its own credentials (API keys, tokens, secrets)
by filtering sensitive values from tool call results before sending to
the
model. Values are collected from .security.yml and replaced with
[FILTERED] using an efficient strings.Replacer (O(n+m)).

- Add FilterSensitiveData and FilterMinLength to ToolsConfig
- Implement SensitiveDataReplacer() with sync.Once caching in
  SecurityConfig
- Use reflection to collect all sensitive values (Model API keys,
  channel
  tokens, web tool API keys, skills tokens)
- Apply filtering in agent loop at 4 tool result locations
- Add comprehensive tests covering all token types

pkg/config/security.go

@@ -10,6 +10,9 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"reflect"
+	"strings"
+	"sync"
 
 	"github.com/caarlos0/env/v11"
 	"github.com/tencent-connect/botgo/log"
@@ -35,6 +38,9 @@ type SecurityConfig struct {
 
 	Web    WebToolsSecurity `yaml:"web,omitempty"`
 	Skills SkillsSecurity   `yaml:"skills,omitempty"`
+
+	// cache for sensitive values and compiled regex (computed once)
+	sensitiveCache *SensitiveDataCache
 }
 
 // ModelSecurityEntry stores security data for a model
@@ -218,3 +224,91 @@ func saveSecurityConfig(securityPath string, sec *SecurityConfig) error {
 	}
 	return fileutil.WriteFileAtomic(securityPath, buf.Bytes(), 0o600)
 }
+
+// SensitiveDataCache caches the compiled regex for filtering sensitive data.
+// SensitiveDataCache caches the strings.Replacer for filtering sensitive data.
+// Computed once on first access via sync.Once.
+type SensitiveDataCache struct {
+	replacer *strings.Replacer
+	once     sync.Once
+}
+
+// SensitiveDataReplacer returns the strings.Replacer for filtering sensitive data.
+// It is computed once on first access via sync.Once.
+func (sec *SecurityConfig) SensitiveDataReplacer() *strings.Replacer {
+	sec.initSensitiveCache()
+	return sec.sensitiveCache.replacer
+}
+
+// initSensitiveCache initializes the sensitive data cache if not already done.
+func (sec *SecurityConfig) initSensitiveCache() {
+	if sec.sensitiveCache == nil {
+		sec.sensitiveCache = &SensitiveDataCache{}
+	}
+	sec.sensitiveCache.once.Do(func() {
+		values := sec.collectSensitiveValues()
+		if len(values) == 0 {
+			sec.sensitiveCache.replacer = strings.NewReplacer()
+			return
+		}
+
+		// Build old/new pairs for strings.Replacer
+		var pairs []string
+		for _, v := range values {
+			if len(v) > 3 {
+				pairs = append(pairs, v, "[FILTERED]")
+			}
+		}
+		if len(pairs) == 0 {
+			sec.sensitiveCache.replacer = strings.NewReplacer()
+			return
+		}
+		sec.sensitiveCache.replacer = strings.NewReplacer(pairs...)
+	})
+}
+
+// collectSensitiveValues collects all sensitive strings from SecurityConfig using reflection.
+func (sec *SecurityConfig) collectSensitiveValues() []string {
+	var values []string
+	collectSensitive(reflect.ValueOf(sec), &values)
+	return values
+}
+
+// collectSensitive recursively traverses the value and collects all non-empty string fields.
+func collectSensitive(v reflect.Value, values *[]string) {
+	// Dereference pointers/interfaces to get the underlying value
+	for v.Kind() == reflect.Ptr || v.Kind() == reflect.Interface {
+		if v.IsNil() {
+			return
+		}
+		v = v.Elem()
+	}
+
+	switch v.Kind() {
+	case reflect.Struct:
+		for i := 0; i < v.NumField(); i++ {
+			field := v.Field(i)
+			fieldType := v.Type().Field(i)
+			if !fieldType.IsExported() {
+				continue
+			}
+			collectSensitive(field, values)
+		}
+	case reflect.String:
+		if v.String() != "" {
+			*values = append(*values, v.String())
+		}
+	case reflect.Slice:
+		if v.Type().Elem().Kind() == reflect.String {
+			for i := 0; i < v.Len(); i++ {
+				if s := v.Index(i).String(); s != "" {
+					*values = append(*values, s)
+				}
+			}
+		}
+	case reflect.Map:
+		for _, key := range v.MapKeys() {
+			collectSensitive(v.MapIndex(key), values)
+		}
+	}
+}