feat(security): scan Homebrew pkgs via brew-vulns

Add Audit.ScanHomebrew, which shells out to "brew vulns --json" (the homebrew/brew-vulns tap) to cover the Homebrew formulae that ScanOSV skips. It resolves each formula's source repo and version tag and queries OSV via the GIT ecosystem. brew-vulns exits 1 when vulnerabilities are found, so success is detected by parseable JSON on stdout rather than the exit code; if the tool is not installed the scan is skipped with a notice instead of failing the audit. Qualitative severities are mapped through the existing severityLabelToScore/cvssToSeverity helpers for consistency. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01GVbEgdgcC1w6qwSq3zC4kg
2026-06-23 23:58:42 +02:00
parent aac1fa7351
commit 5a610ff5c4
3 changed files with 247 additions and 0 deletions
@@ -0,0 +1,137 @@
+package security
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"os/exec"
+	"strings"
+)
+
+// brewVulnsResult mirrors a single element of the JSON array emitted by
+// `brew vulns --json` (the homebrew/brew-vulns tap). Only formulae that have
+// at least one vulnerability are included in the output.
+type brewVulnsResult struct {
+	Formula         string `json:"formula"`
+	Version         string `json:"version"`
+	Tag             string `json:"tag"`
+	RepoURL         string `json:"repo_url"`
+	Vulnerabilities []struct {
+		ID            string   `json:"id"`
+		Severity      string   `json:"severity"` // CRITICAL/HIGH/MEDIUM/LOW/UNKNOWN
+		Summary       string   `json:"summary"`
+		Aliases       []string `json:"aliases"`
+		FixedVersions []string `json:"fixed_versions"`
+	} `json:"vulnerabilities"`
+}
+
+// ScanHomebrew scans installed Homebrew formulae for known vulnerabilities by
+// shelling out to `brew vulns --json`. That subcommand resolves each formula's
+// source repository and version tag and queries OSV.dev via the GIT ecosystem
+// — covering the Homebrew packages that ScanOSV deliberately skips.
+//
+// brew-vulns is an optional external dependency: if it is not installed (or
+// otherwise fails to produce JSON), the Homebrew scan is skipped with a notice
+// rather than failing the whole audit. Note that `brew vulns` exits with code
+// 1 when vulnerabilities are found, so the exit code is not used to detect
+// failure — the presence of parseable JSON on stdout is.
+func (a *Audit) ScanHomebrew() error {
+	fmt.Println("  Scanning Homebrew packages via brew-vulns...")
+
+	cmd := exec.Command("brew", "vulns", "--json")
+	var stdout, stderr bytes.Buffer
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+	runErr := cmd.Run()
+
+	out := bytes.TrimSpace(stdout.Bytes())
+
+	findings, n, err := parseBrewVulns(out)
+	if err != nil {
+		// No JSON on stdout: brew-vulns is likely not installed, or it errored
+		// (e.g. an OSV outage). Treat as optional and skip.
+		detail := strings.TrimSpace(stderr.String())
+		if detail == "" && runErr != nil {
+			detail = runErr.Error()
+		}
+		if detail == "" {
+			detail = "no output"
+		}
+		fmt.Printf("  ⏭️  Skipping Homebrew scan (brew-vulns unavailable): %s\n", firstLine(detail))
+		fmt.Println("     Install with: brew install homebrew/brew-vulns/brew-vulns")
+		return nil
+	}
+
+	a.Findings = append(a.Findings, findings...)
+	fmt.Printf("  Homebrew scan: %d vulnerabilities across %d formula(e)\n", len(findings), n)
+	return nil
+}
+
+// parseBrewVulns converts `brew vulns --json` output into Findings. It returns
+// the findings and the number of affected formulae, or an error if the output
+// is not a parseable brew-vulns JSON array.
+func parseBrewVulns(out []byte) ([]Finding, int, error) {
+	out = bytes.TrimSpace(out)
+	if len(out) == 0 {
+		return nil, 0, fmt.Errorf("empty output")
+	}
+
+	var results []brewVulnsResult
+	if err := json.Unmarshal(out, &results); err != nil {
+		return nil, 0, err
+	}
+
+	var findings []Finding
+	for _, r := range results {
+		for _, v := range r.Vulnerabilities {
+			cvss := severityLabelToScore(v.Severity)
+			findings = append(findings, Finding{
+				PackageName:    r.Formula,
+				PackageVersion: r.Version,
+				CVE:            preferCVE(v.ID, v.Aliases),
+				CVSS:           cvss,
+				Summary:        v.Summary,
+				Link:           advisoryLink(v.ID),
+				Severity:       cvssToSeverity(cvss),
+			})
+		}
+	}
+	return findings, len(results), nil
+}
+
+// preferCVE returns a CVE identifier when one is available, since CVE IDs are
+// the most widely recognized. brew-vulns reports the OSV record ID (which may
+// be a GHSA or OSV ID) plus any aliases.
+func preferCVE(id string, aliases []string) string {
+	if strings.HasPrefix(id, "CVE-") {
+		return id
+	}
+	for _, a := range aliases {
+		if strings.HasPrefix(a, "CVE-") {
+			return a
+		}
+	}
+	return id
+}
+
+// advisoryLink builds a human-facing advisory URL for an OSV record ID.
+func advisoryLink(id string) string {
+	switch {
+	case strings.HasPrefix(id, "CVE-"):
+		return "https://nvd.nist.gov/vuln/detail/" + id
+	case strings.HasPrefix(id, "GHSA-"):
+		return "https://github.com/advisories/" + id
+	case id == "":
+		return ""
+	default:
+		return "https://osv.dev/vulnerability/" + id
+	}
+}
+
+// firstLine returns the first non-empty line of s, for compact error display.
+func firstLine(s string) string {
+	if i := strings.IndexByte(s, '\n'); i != -1 {
+		return strings.TrimSpace(s[:i])
+	}
+	return s
+}