feat(12-02): implement FOFA, Netlas, BinaryEdge recon sources

- FOFASource searches FOFA API with base64-encoded queries (email+key auth)
- NetlasSource searches Netlas API with X-API-Key header auth
- BinaryEdgeSource searches BinaryEdge API with X-Key header auth
- All three implement recon.ReconSource with shared Client retry/backoff

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

pkg/recon/sources/fofa.go

@@ -0,0 +1,144 @@
+package sources
+
+import (
+	"context"
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/http"
+	"strings"
+	"time"
+
+	"golang.org/x/time/rate"
+
+	"github.com/salvacybersec/keyhunter/pkg/providers"
+	"github.com/salvacybersec/keyhunter/pkg/recon"
+)
+
+// FOFASource implements recon.ReconSource against the FOFA internet search
+// engine API. It iterates provider keyword queries and emits a Finding per
+// result.
+//
+// A missing Email or API key disables the source without error.
+type FOFASource struct {
+	Email    string
+	APIKey   string
+	BaseURL  string
+	Registry *providers.Registry
+	Limiters *recon.LimiterRegistry
+	client   *Client
+}
+
+// Compile-time assertion.
+var _ recon.ReconSource = (*FOFASource)(nil)
+
+func (s *FOFASource) Name() string         { return "fofa" }
+func (s *FOFASource) RateLimit() rate.Limit { return rate.Every(1 * time.Second) }
+func (s *FOFASource) Burst() int            { return 1 }
+func (s *FOFASource) RespectsRobots() bool  { return false }
+
+// Enabled returns true only when both Email and APIKey are configured.
+func (s *FOFASource) Enabled(_ recon.Config) bool { return s.Email != "" && s.APIKey != "" }
+
+// Sweep issues one FOFA search request per provider keyword and emits a
+// Finding for every result row.
+func (s *FOFASource) Sweep(ctx context.Context, _ string, out chan<- recon.Finding) error {
+	if s.Email == "" || s.APIKey == "" {
+		return nil
+	}
+	if s.client == nil {
+		s.client = NewClient()
+	}
+	base := s.BaseURL
+	if base == "" {
+		base = "https://fofa.info"
+	}
+
+	queries := BuildQueries(s.Registry, "fofa")
+	kwIndex := fofaKeywordIndex(s.Registry)
+
+	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
+			}
+		}
+
+		qb64 := base64.StdEncoding.EncodeToString([]byte(q))
+		endpoint := fmt.Sprintf("%s/api/v1/search/all?email=%s&key=%s&qbase64=%s&size=100",
+			base, s.Email, s.APIKey, qb64)
+		req, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
+		if err != nil {
+			return fmt.Errorf("fofa: build request: %w", err)
+		}
+		req.Header.Set("Accept", "application/json")
+
+		resp, err := s.client.Do(ctx, req)
+		if err != nil {
+			if errors.Is(err, ErrUnauthorized) {
+				return err
+			}
+			if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
+				return err
+			}
+			continue
+		}
+
+		var parsed fofaSearchResponse
+		decErr := json.NewDecoder(resp.Body).Decode(&parsed)
+		_ = resp.Body.Close()
+		if decErr != nil {
+			continue
+		}
+
+		provName := kwIndex[strings.ToLower(q)]
+		for _, row := range parsed.Results {
+			// Each row is [host, ip, port].
+			if len(row) < 3 {
+				continue
+			}
+			f := recon.Finding{
+				ProviderName: provName,
+				Confidence:   "low",
+				Source:       fmt.Sprintf("fofa://%s:%s", row[1], row[2]),
+				SourceType:   "recon:fofa",
+				DetectedAt:   time.Now(),
+			}
+			select {
+			case out <- f:
+			case <-ctx.Done():
+				return ctx.Err()
+			}
+		}
+	}
+	return nil
+}
+
+type fofaSearchResponse struct {
+	Results [][]string `json:"results"`
+	Size    int        `json:"size"`
+}
+
+// fofaKeywordIndex maps lowercased keywords to provider names.
+func fofaKeywordIndex(reg *providers.Registry) map[string]string {
+	m := make(map[string]string)
+	if reg == nil {
+		return m
+	}
+	for _, p := range reg.List() {
+		for _, k := range p.Keywords {
+			kl := strings.ToLower(strings.TrimSpace(k))
+			if kl == "" {
+				continue
+			}
+			if _, exists := m[kl]; !exists {
+				m[kl] = p.Name
+			}
+		}
+	}
+	return m
+}