fix(safety): compile baked policy to code to resist binary tampering

Compile baked safety-profile policies into generated hash switches so the raw allow/deny rule strings are no longer embedded as a patchable YAML blob.

Verification before merge:
- `go test ./cmd/bake-safety-profile ./internal/safetyprofile ./internal/cmd`
- `make lint`
- `./build-safe.sh safety-profiles/agent-safe.yaml -o bin/gog-agent-safe-review`
- `./build-safe.sh safety-profiles/readonly.yaml -o bin/gog-readonly-review`
- runtime block checks for agent-safe and readonly baked binaries

Co-authored-by: drewburchfield <drewburchfield@gmail.com>

Author: drewburchfield

.golangci.yml

@@ -120,6 +120,11 @@ linters:
           - dupl
           - wsl_v5
           - tagliatelle
+      - path: internal/safetyprofile/.*\.go
+        linters:
+          - err113
+          - wrapcheck
+          - wsl_v5
       - path: internal/googleauth/.*\.go
         linters:
           - tagliatelle

cmd/bake-safety-profile/main.go

@@ -5,36 +5,111 @@ import (
 	"fmt"
 	"os"
 	"strconv"
+	"strings"
 
-	"github.com/steipete/gogcli/internal/cmd"
+	"github.com/steipete/gogcli/internal/safetyprofile"
 )
 
+const usage = `Usage: bake-safety-profile <profile.yaml> <output.go>` + "\n"
+
 func main() {
-	if len(os.Args) != 3 {
-		_, _ = fmt.Fprintln(os.Stderr, "usage: bake-safety-profile <profile.yaml> <output.go>")
+	args := os.Args[1:]
+	if len(args) != 2 {
+		_, _ = fmt.Fprint(os.Stderr, usage)
 		os.Exit(2)
 	}
 
-	raw, err := os.ReadFile(os.Args[1]) // #nosec G304 G703 -- build helper intentionally reads the requested profile path.
+	raw, err := os.ReadFile(args[0]) // #nosec G304 G703 -- build helper intentionally reads the requested profile path.
 	if err != nil {
 		_, _ = fmt.Fprintf(os.Stderr, "read profile: %v\n", err)
 		os.Exit(1)
 	}
-	if err := cmd.ValidateSafetyProfile(string(raw)); err != nil {
+
+	profile, err := safetyprofile.Parse(string(raw))
+	if err != nil {
 		_, _ = fmt.Fprintf(os.Stderr, "parse profile: %v\n", err)
 		os.Exit(1)
 	}
 
+	out := generate(profile)
+	if err := os.WriteFile(args[1], out, 0o600); err != nil { // #nosec G306 G703 -- build helper intentionally writes the requested generated Go path.
+		_, _ = fmt.Fprintf(os.Stderr, "write output: %v\n", err)
+		os.Exit(1)
+	}
+}
+
+// generate emits a Go file that resolves the bakedSafety* package-level
+// functions for safety_profile builds. Allow and deny rules are encoded as
+// FNV-64a hashes in switch statements so that the rule set itself is no
+// longer a contiguous, patchable string in the binary.
+func generate(profile *safetyprofile.Profile) []byte {
 	var out bytes.Buffer
+	hasAllowRules := profile.AllowAll || len(profile.AllowRules) > 0
+
 	out.WriteString("// Code generated by cmd/bake-safety-profile; DO NOT EDIT.\n")
+	commentName := strings.ReplaceAll(strings.ReplaceAll(profile.Name, "\n", " "), "\r", " ")
+	fmt.Fprintf(&out, "// Profile: %s (%d allow, %d deny, allow-all=%t)\n", commentName, len(profile.AllowRules), len(profile.DenyRules), profile.AllowAll)
+	out.WriteString("// Hash: FNV-64a over dotted command paths.\n")
 	out.WriteString("//go:build safety_profile\n\n")
 	out.WriteString("package cmd\n\n")
-	out.WriteString("var bakedSafetyProfileYAML = ")
-	out.WriteString(strconv.Quote(string(raw)))
+
+	out.WriteString("const bakedSafetyProfileNameConst = ")
+	out.WriteString(strconv.Quote(profile.Name))
+	out.WriteString("\n\n")
+
+	out.WriteString("func bakedSafetyEnabled() bool       { return true }\n")
+	out.WriteString("func bakedSafetyProfileName() string { return bakedSafetyProfileNameConst }\n")
+	fmt.Fprintf(&out, "func bakedSafetyHasAllowRules() bool { return %t }\n\n", hasAllowRules)
+
+	writeMatcher(&out, "bakedSafetyAllowMatch", profile.AllowRules, profile.AllowAll)
 	out.WriteString("\n")
+	writeMatcher(&out, "bakedSafetyDenyMatch", profile.DenyRules, false)
 
-	if err := os.WriteFile(os.Args[2], out.Bytes(), 0o600); err != nil { // #nosec G306 G703 -- build helper intentionally writes the requested generated Go path.
-		_, _ = fmt.Fprintf(os.Stderr, "write output: %v\n", err)
-		os.Exit(1)
+	return out.Bytes()
+}
+
+func writeMatcher(out *bytes.Buffer, name string, rules []string, matchAll bool) {
+	fmt.Fprintf(out, "func %s(path []string) bool {\n", name)
+	if matchAll {
+		out.WriteString("\treturn true\n}\n")
+		return
+	}
+	if len(rules) == 0 {
+		out.WriteString("\treturn false\n}\n")
+		return
+	}
+
+	out.WriteString("\tif len(path) == 0 {\n\t\treturn false\n\t}\n")
+	out.WriteString("\tfor i := 1; i <= len(path); i++ {\n")
+	out.WriteString("\t\tswitch bakedSafetyHashPath(path[:i]) {\n")
+	out.WriteString("\t\tcase ")
+
+	cases := make([]string, 0, len(rules))
+	seen := make(map[uint64]string, len(rules))
+	for _, rule := range rules {
+		h := safetyprofile.HashRule(rule)
+		if existing, dup := seen[h]; dup {
+			fmt.Fprintf(os.Stderr, "bake-safety-profile: hash collision between %q and %q (FNV-64a=%#x); pick a different name or extend the hash\n", existing, rule, h)
+			os.Exit(1)
+		}
+		seen[h] = rule
+		cases = append(cases, fmt.Sprintf("0x%016x", h))
+	}
+
+	const perLine = 4
+	for i, c := range cases {
+		out.WriteString(c)
+		if i == len(cases)-1 {
+			break
+		}
+		out.WriteString(",")
+		if (i+1)%perLine == 0 {
+			out.WriteString("\n\t\t\t")
+		} else {
+			out.WriteString(" ")
+		}
 	}
+	out.WriteString(":\n\t\t\treturn true\n")
+	out.WriteString("\t\t}\n\t}\n")
+	out.WriteString("\treturn false\n}\n")
 }

cmd/bake-safety-profile/main_test.go

@@ -0,0 +1,138 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"go/parser"
+	"go/token"
+	"strings"
+	"testing"
+
+	"github.com/steipete/gogcli/internal/safetyprofile"
+)
+
+func TestGenerateProducesParseableGoWithExpectedHashes(t *testing.T) {
+	profile := &safetyprofile.Profile{
+		Name:       "test",
+		AllowAll:   false,
+		AllowRules: []string{"version", "gmail.search", "gmail.drafts.create"},
+		DenyRules:  []string{"gmail.send", "gmail.drafts.send"},
+	}
+
+	out := generate(profile)
+
+	if _, err := parser.ParseFile(token.NewFileSet(), "gen.go", out, parser.AllErrors); err != nil {
+		t.Fatalf("generated code does not parse as Go:\n%s\n\nerror: %v", out, err)
+	}
+
+	want := []string{
+		`//go:build safety_profile`,
+		`package cmd`,
+		`const bakedSafetyProfileNameConst = "test"`,
+		`func bakedSafetyEnabled() bool       { return true }`,
+		`func bakedSafetyHasAllowRules() bool { return true }`,
+	}
+	for _, line := range want {
+		if !bytes.Contains(out, []byte(line)) {
+			t.Fatalf("generated output missing %q\n\nfull output:\n%s", line, out)
+		}
+	}
+
+	for _, rule := range profile.AllowRules {
+		hex := fmt.Sprintf("0x%016x", safetyprofile.HashRule(rule))
+		if !bytes.Contains(out, []byte(hex)) {
+			t.Fatalf("expected allow hash %s for rule %q in output", hex, rule)
+		}
+	}
+	for _, rule := range profile.DenyRules {
+		hex := fmt.Sprintf("0x%016x", safetyprofile.HashRule(rule))
+		if !bytes.Contains(out, []byte(hex)) {
+			t.Fatalf("expected deny hash %s for rule %q in output", hex, rule)
+		}
+	}
+
+	for _, rule := range profile.AllowRules {
+		if bytes.Contains(out, []byte(fmt.Sprintf("%q", rule))) {
+			t.Fatalf("rule string %q must not appear in generated output", rule)
+		}
+	}
+	for _, rule := range profile.DenyRules {
+		if bytes.Contains(out, []byte(fmt.Sprintf("%q", rule))) {
+			t.Fatalf("rule string %q must not appear in generated output", rule)
+		}
+	}
+}
+
+func TestGenerateSanitizesProfileNameInComment(t *testing.T) {
+	profile := &safetyprofile.Profile{
+		Name:      "bad\nname\rwith-controls",
+		AllowAll:  true,
+		DenyRules: []string{},
+	}
+	out := generate(profile)
+
+	if _, err := parser.ParseFile(token.NewFileSet(), "gen.go", out, parser.AllErrors); err != nil {
+		t.Fatalf("generated code with control chars in name does not parse:\n%s\n\nerror: %v", out, err)
+	}
+	if bytes.Contains(out, []byte("\nname\r")) || bytes.Contains(out, []byte("\nname\n")) {
+		t.Fatalf("comment header leaked control chars from profile name:\n%s", out)
+	}
+}
+
+func TestGenerateAllowAllEmitsConstantTrue(t *testing.T) {
+	profile := &safetyprofile.Profile{
+		Name:      "full",
+		AllowAll:  true,
+		DenyRules: []string{},
+	}
+	out := string(generate(profile))
+
+	allowFn := extractFunc(t, out, "bakedSafetyAllowMatch")
+	if !strings.Contains(allowFn, "return true") || strings.Contains(allowFn, "switch ") {
+		t.Fatalf("AllowAll allow matcher should be `return true` only, got:\n%s", allowFn)
+	}
+
+	denyFn := extractFunc(t, out, "bakedSafetyDenyMatch")
+	if !strings.Contains(denyFn, "return false") {
+		t.Fatalf("empty deny matcher should `return false`, got:\n%s", denyFn)
+	}
+}
+
+func TestGenerateEmptyAllowEmitsConstantFalse(t *testing.T) {
+	profile := &safetyprofile.Profile{
+		Name:      "deny-only",
+		AllowAll:  false,
+		DenyRules: []string{"gmail.send"},
+	}
+	out := string(generate(profile))
+
+	if !strings.Contains(out, "func bakedSafetyHasAllowRules() bool { return false }") {
+		t.Fatalf("expected hasAllowRules=false for deny-only profile, got:\n%s", out)
+	}
+	allowFn := extractFunc(t, out, "bakedSafetyAllowMatch")
+	if !strings.Contains(allowFn, "return false") || strings.Contains(allowFn, "switch ") {
+		t.Fatalf("empty allow matcher should be `return false` only, got:\n%s", allowFn)
+	}
+}
+
+func extractFunc(t *testing.T, src, name string) string {
+	t.Helper()
+	start := strings.Index(src, "func "+name+"(")
+	if start < 0 {
+		t.Fatalf("function %s not found in:\n%s", name, src)
+	}
+	depth := 0
+	for i := start; i < len(src); i++ {
+		switch src[i] {
+		case '{':
+			depth++
+		case '}':
+			depth--
+			if depth == 0 {
+				return src[start : i+1]
+			}
+		}
+	}
+	t.Fatalf("function %s has unbalanced braces", name)
+	return ""
+}

docs/safety-profiles.md

@@ -67,6 +67,21 @@ bin/gog-readonly --enable-commands gmail.send gmail send \
 The command still fails because the baked policy is checked before runtime
 allowlists.
 
+## Tamper Resistance
+
+The generator emits the allow and deny rule sets as `switch` statements on the
+FNV-64a hash of each dotted command path, not as raw YAML. The compiled rule
+table never contains the rule strings themselves, so to re-enable a blocked
+command an attacker has to patch compiled machine code rather than flip ASCII
+bytes in a YAML blob; the cost goes from a one-line `sed` invocation to
+disassembly-level work.
+
+Note that command names may still appear in the binary from unrelated metadata
+(API URLs, error message format strings, Kong help text). What this hardening
+guarantees is that the rule set itself is no longer a contiguous, patchable
+string. The profile name (e.g. `agent-safe`) is also embedded as a constant so
+error messages can reference it.
+
 ## Preset Profiles
 
 `safety-profiles/agent-safe.yaml`