Add recon form fingerprint library and SSRF canary mode.

Score crawl inputs by SSRF-prone field names and register ping-back canaries for operator paste confirmation.

server/internal/recon/fingerprint.go

@@ -0,0 +1,104 @@
+package recon
+
+import (
+	"sort"
+	"strings"
+
+	"golang.org/x/net/html"
+)
+
+var formFingerprintKeywords = []struct {
+	keyword string
+	weight  int
+}{
+	{"url", 12}, {"src", 10}, {"href", 10}, {"callback", 14}, {"redirect", 13},
+	{"avatar", 8}, {"import", 11}, {"feed", 9}, {"screenshot", 12}, {"pdf", 10}, {"proxy", 11},
+}
+
+func ScoreFormFieldFingerprint(name, id, placeholder string) (score int, matches []string) {
+	joined := strings.ToLower(strings.Join([]string{name, id, placeholder}, " "))
+	seen := map[string]bool{}
+	for _, kw := range formFingerprintKeywords {
+		if strings.Contains(joined, kw.keyword) {
+			score += kw.weight
+			if !seen[kw.keyword] {
+				seen[kw.keyword] = true
+				matches = append(matches, kw.keyword)
+			}
+		}
+	}
+	return score, matches
+}
+
+func ExtractFormFieldFingerprints(pageURL, body string) []FormFieldFingerprint {
+	root, err := html.Parse(strings.NewReader(body))
+	if err != nil {
+		return nil
+	}
+	var out []FormFieldFingerprint
+	var walk func(*html.Node)
+	walk = func(n *html.Node) {
+		if n.Type == html.ElementNode && (n.Data == "input" || n.Data == "textarea" || n.Data == "select") {
+			name := fingerprintAttr(n, "name")
+			id := fingerprintAttr(n, "id")
+			placeholder := fingerprintAttr(n, "placeholder")
+			score, matches := ScoreFormFieldFingerprint(name, id, placeholder)
+			if score > 0 {
+				out = append(out, FormFieldFingerprint{
+					PageURL: pageURL, Name: name, ID: id, Placeholder: placeholder,
+					Score: score, Matches: matches,
+				})
+			}
+		}
+		for c := n.FirstChild; c != nil; c = c.NextSibling {
+			walk(c)
+		}
+	}
+	walk(root)
+	sort.Slice(out, func(i, j int) bool {
+		if out[i].Score != out[j].Score {
+			return out[i].Score > out[j].Score
+		}
+		if out[i].Name != out[j].Name {
+			return out[i].Name < out[j].Name
+		}
+		return out[i].ID < out[j].ID
+	})
+	return out
+}
+
+func fingerprintAttr(n *html.Node, key string) string {
+	for _, a := range n.Attr {
+		if a.Key == key {
+			return a.Val
+		}
+	}
+	return ""
+}
+
+func TopFormFieldFingerprint(fields []FormFieldFingerprint) *FormFieldFingerprint {
+	if len(fields) == 0 {
+		return nil
+	}
+	top := fields[0]
+	return &top
+}
+
+func ApplyCanaryPasteTarget(fields []FormFieldFingerprint, canaryURL string) {
+	for i := range fields {
+		fields[i].PasteTarget = canaryURL
+	}
+}
+
+func AppendPageFingerprints(report *CrawlReport, pageURL, body string) {
+	if report == nil {
+		return
+	}
+	fps := ExtractFormFieldFingerprints(pageURL, body)
+	report.FingerprintFields = append(report.FingerprintFields, fps...)
+	for _, fp := range fps {
+		if fp.Score >= 10 {
+			report.SSRFScore += fp.Score / 5
+		}
+	}
+}