feat(build): 扫描门按可配严重度拦截并可接受已知风险，留存 Trivy 报告与 CycloneDX SBOM，面板构建页展示扫描结果

cmd/felis/scangate.go

@@ -0,0 +1,166 @@
+package main
+
+import (
+	"errors"
+	"flag"
+	"fmt"
+	"io"
+	"io/fs"
+	"os"
+	"strings"
+
+	"felis.lolicon.best/internal/build"
+)
+
+// maxScanDocument bounds each document scan-gate reads: a modpack report lists a
+// few thousand packages, far below this. Tests shrink it.
+var maxScanDocument int64 = 64 << 20
+
+// cmdScanGate is the build pod's verdict step, after trivy wrote its full JSON
+// report and trivy convert wrote the CycloneDX SBOM. It applies the scan policy
+// to the report, prints the verdict and every blocking finding, then appends the
+// verdict, the report and the SBOM to its log as the envelope felis-api keeps on
+// the build (build.WriteScanEnvelope). It exits 1 when a finding blocks, which
+// fails the pod before the push step runs, and 2 when the report cannot be read,
+// so a scan that produced nothing usable never admits an image.
+func cmdScanGate(args []string, stdout, stderr io.Writer) int {
+	fset := flag.NewFlagSet("scan-gate", flag.ContinueOnError)
+	fset.SetOutput(stderr)
+	reportPath := fset.String("report", "", "trivy JSON report (required)")
+	sbomPath := fset.String("sbom", "", "CycloneDX SBOM to keep with the report")
+	failOn := fset.String("fail-on", strings.Join(build.DefaultScanFailOn, ","), "comma-separated severities that block the image")
+	failUnfixed := fset.Bool("fail-unfixed", false, "block on vulnerabilities that have no fixed release too")
+	accept := fset.String("accept", "", "comma-separated vulnerability ids and secret rule ids that never block")
+	termLog := fset.String("termination-log", "/dev/termination-log", "where the one-line verdict goes for the pod status")
+	if err := fset.Parse(args); err != nil {
+		return 2
+	}
+	// A stray argument is a policy the gate would otherwise drop without a word
+	// (a comma split out of --fail-on, say).
+	if fset.NArg() > 0 {
+		fmt.Fprintf(stderr, "felis scan-gate: unexpected argument %q\n", fset.Arg(0))
+		return 2
+	}
+	sevs, err := build.ParseSeverities(*failOn)
+	if err != nil {
+		fmt.Fprintf(stderr, "felis scan-gate: --fail-on: %v\n", err)
+		return 2
+	}
+	accepted, err := build.ParseScanAccept(*accept)
+	if err != nil {
+		fmt.Fprintf(stderr, "felis scan-gate: --accept: %v\n", err)
+		return 2
+	}
+	if *reportPath == "" {
+		fmt.Fprintln(stderr, "felis scan-gate: --report is required")
+		return 2
+	}
+	fail := func(msg string) int {
+		fmt.Fprintln(stderr, "felis scan-gate: "+msg)
+		writeTerminationLog(*termLog, msg)
+		return 2
+	}
+	report, err := readScanDocument(*reportPath)
+	if err != nil {
+		return fail("the scan report is unreadable: " + err.Error())
+	}
+	policy := build.ScanPolicy{FailOn: sevs, FailUnfixed: *failUnfixed, Accept: accepted}
+	summary, err := build.Summarize(report, policy)
+	if err != nil {
+		return fail("the scan report is unreadable: " + err.Error())
+	}
+	env := build.ScanEnvelope{Summary: summary, Report: report}
+	if *sbomPath != "" {
+		switch sbom, err := readScanDocument(*sbomPath); {
+		case err == nil:
+			env.SBOM = sbom
+		case errors.Is(err, fs.ErrNotExist):
+			fmt.Fprintf(stdout, "felis scan-gate: no SBOM at %s; keeping the report alone\n", *sbomPath)
+		default:
+			return fail("the SBOM is unreadable: " + err.Error())
+		}
+	}
+
+	printScanVerdict(stdout, summary)
+	written, err := build.WriteScanEnvelope(stdout, env)
+	if err != nil {
+		return fail("could not write the scan envelope: " + err.Error())
+	}
+	for _, doc := range written.Summary.Omitted {
+		fmt.Fprintf(stderr, "felis scan-gate: the %s is too large to keep with the build and was left out\n", doc)
+	}
+	if summary.Blocked {
+		writeTerminationLog(*termLog, summary.Reason())
+		return 1
+	}
+	writeTerminationLog(*termLog, "the scan passed")
+	return 0
+}
+
+// printScanVerdict writes the human half of scan-gate's log.
+func printScanVerdict(w io.Writer, s build.ScanSummary) {
+	var counts []string
+	for _, sev := range build.Severities {
+		counts = append(counts, fmt.Sprintf("%s %d", sev, s.Counts[sev]))
+	}
+	fmt.Fprintf(w, "felis scan-gate: %d packages; findings: %s\n", s.Packages, strings.Join(counts, ", "))
+	unfixed := "vulnerabilities with no fixed release do not block"
+	if s.Policy.FailUnfixed {
+		unfixed = "vulnerabilities with no fixed release block too"
+	}
+	fmt.Fprintf(w, "felis scan-gate: blocking on %s (%s)\n", strings.Join(s.Policy.FailOn, ", "), unfixed)
+	if len(s.Policy.Accept) > 0 {
+		matched := 0
+		for _, f := range s.Findings {
+			if f.Accepted {
+				matched++
+			}
+		}
+		fmt.Fprintf(w, "felis scan-gate: accepted ids, never blocking: %s; listed findings under them: %d\n", strings.Join(s.Policy.Accept, ", "), matched)
+	}
+	if !s.Blocked {
+		fmt.Fprintln(w, "felis scan-gate: nothing blocks this image")
+		return
+	}
+	fmt.Fprintln(w, "felis scan-gate: "+build.Printable(s.Reason()))
+	for _, f := range s.Findings {
+		if !f.Blocking {
+			break
+		}
+		fix := f.Fixed
+		if fix == "" {
+			fix = "no fix"
+		}
+		if f.Kind == build.FindingSecret {
+			fmt.Fprintf(w, "  %s %s secret in %s: %s\n", build.Printable(f.ID), f.Severity, build.Printable(f.Target), build.Printable(f.Title))
+			continue
+		}
+		fmt.Fprintf(w, "  %s %s %s %s -> %s (%s)\n", build.Printable(f.ID), f.Severity,
+			build.Printable(f.Package), build.Printable(f.Installed), build.Printable(fix), build.Printable(f.Target))
+	}
+}
+
+func readScanDocument(path string) ([]byte, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	b, err := io.ReadAll(io.LimitReader(f, maxScanDocument+1))
+	if err != nil {
+		return nil, err
+	}
+	if int64(len(b)) > maxScanDocument {
+		return nil, fmt.Errorf("%s exceeds %d bytes", path, maxScanDocument)
+	}
+	return b, nil
+}
+
+// writeTerminationLog leaves msg where the kubelet copies it into the container
+// status. It is best effort: the log carries the same verdict.
+func writeTerminationLog(path, msg string) {
+	if path == "" {
+		return
+	}
+	_ = os.WriteFile(path, []byte(build.Printable(msg)), 0o644)
+}