feat(16-01): add VirusTotal and IntelligenceX recon sources

- VirusTotalSource searches VT Intelligence API for files containing API keys
- IntelligenceXSource searches IX archive with 3-step flow (search/results/read)
- Both credential-gated (Enabled returns false without API key)
- ciLogKeyPattern used for content matching
- Tests with httptest mocks for happy path and empty results

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pkg/recon/sources/virustotal.go

@@ -0,0 +1,116 @@
+package sources
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"time"
+
+	"golang.org/x/time/rate"
+
+	"github.com/salvacybersec/keyhunter/pkg/providers"
+	"github.com/salvacybersec/keyhunter/pkg/recon"
+)
+
+// VirusTotalSource searches the VirusTotal Intelligence API for files and URLs
+// containing API key patterns. Malware samples frequently contain hard-coded
+// API keys used by threat actors to exfiltrate data or proxy requests.
+type VirusTotalSource struct {
+	APIKey   string
+	BaseURL  string
+	Registry *providers.Registry
+	Limiters *recon.LimiterRegistry
+	Client   *Client
+}
+
+var _ recon.ReconSource = (*VirusTotalSource)(nil)
+
+func (s *VirusTotalSource) Name() string         { return "virustotal" }
+func (s *VirusTotalSource) RateLimit() rate.Limit { return rate.Every(15 * time.Second) }
+func (s *VirusTotalSource) Burst() int            { return 2 }
+func (s *VirusTotalSource) RespectsRobots() bool   { return false }
+func (s *VirusTotalSource) Enabled(_ recon.Config) bool {
+	return s.APIKey != ""
+}
+
+// vtSearchResponse represents the top-level VT intelligence search response.
+type vtSearchResponse struct {
+	Data []vtSearchItem `json:"data"`
+}
+
+// vtSearchItem is a single item in the VT search results.
+type vtSearchItem struct {
+	ID         string          `json:"id"`
+	Attributes json.RawMessage `json:"attributes"`
+}
+
+func (s *VirusTotalSource) Sweep(ctx context.Context, query string, out chan<- recon.Finding) error {
+	base := s.BaseURL
+	if base == "" {
+		base = "https://www.virustotal.com/api/v3"
+	}
+	client := s.Client
+	if client == nil {
+		client = NewClient()
+	}
+
+	queries := BuildQueries(s.Registry, "virustotal")
+	if len(queries) == 0 {
+		return nil
+	}
+
+	for _, q := range queries {
+		if err := ctx.Err(); err != nil {
+			return err
+		}
+
+		if s.Limiters != nil {
+			if err := s.Limiters.Wait(ctx, s.Name(), s.RateLimit(), s.Burst(), false); err != nil {
+				return err
+			}
+		}
+
+		searchURL := fmt.Sprintf(
+			"%s/intelligence/search?query=%s&limit=10",
+			base, url.QueryEscape(q),
+		)
+		req, err := http.NewRequestWithContext(ctx, http.MethodGet, searchURL, nil)
+		if err != nil {
+			continue
+		}
+		req.Header.Set("x-apikey", s.APIKey)
+
+		resp, err := client.Do(ctx, req)
+		if err != nil {
+			continue
+		}
+
+		data, err := io.ReadAll(io.LimitReader(resp.Body, 512*1024))
+		_ = resp.Body.Close()
+		if err != nil {
+			continue
+		}
+
+		var result vtSearchResponse
+		if err := json.Unmarshal(data, &result); err != nil {
+			continue
+		}
+
+		for _, item := range result.Data {
+			attrs := string(item.Attributes)
+			if ciLogKeyPattern.MatchString(attrs) {
+				out <- recon.Finding{
+					ProviderName: q,
+					Source:       fmt.Sprintf("https://www.virustotal.com/gui/file/%s", item.ID),
+					SourceType:   "recon:virustotal",
+					Confidence:   "medium",
+					DetectedAt:   time.Now(),
+				}
+			}
+		}
+	}
+	return nil
+}