AD-901: Add permission policy

apps/server/src/index.ts

@@ -68,3 +68,18 @@ export type {
   ProposeWorkflowPatchInput,
   WorkflowPatchProposal,
 } from "./patches/patch-schema.js";
+export {
+  DEFAULT_AGENT_PERMISSION_GRANTS,
+  PERMISSION_NAMES,
+  createDefaultPermissionPolicy,
+} from "./security/permission-policy.js";
+export type {
+  CommandPermissionEvaluationRequest,
+  CreateDefaultPermissionPolicyOptions,
+  PermissionDecision,
+  PermissionEvaluationRequest,
+  PermissionEvaluationResult,
+  PermissionGrants,
+  PermissionName,
+  PermissionPolicy,
+} from "./security/permission-policy.js";

apps/server/src/security/permission-policy.test.ts

@@ -0,0 +1,91 @@
+import { describe, expect, it } from "vitest";
+
+import {
+  createDefaultPermissionPolicy,
+  DEFAULT_AGENT_PERMISSION_GRANTS,
+} from "./permission-policy.js";
+
+describe("createDefaultPermissionPolicy", () => {
+  it("allows read-only behavior for the default agent policy", () => {
+    const policy = createDefaultPermissionPolicy();
+
+    expect(DEFAULT_AGENT_PERMISSION_GRANTS).toEqual({
+      read: true,
+      write: false,
+      safeCommands: true,
+      arbitraryCommands: false,
+      network: false,
+      installDependencies: false,
+      gitCommit: false,
+      gitPush: false,
+    });
+    expect(policy.evaluate({ permission: "read" })).toMatchObject({
+      decision: "allow",
+      requiresApproval: false,
+    });
+  });
+
+  it("rejects writes, installs, arbitrary commands, commits, pushes, and network by default", () => {
+    const policy = createDefaultPermissionPolicy();
+
+    for (const permission of [
+      "write",
+      "arbitraryCommands",
+      "network",
+      "installDependencies",
+      "gitCommit",
+      "gitPush",
+    ] as const) {
+      expect(policy.evaluate({ permission })).toMatchObject({
+        permission,
+        decision: "deny",
+        requiresApproval: true,
+      });
+    }
+  });
+
+  it("allows safe commands and denies unsafe commands without arbitrary command approval", () => {
+    const policy = createDefaultPermissionPolicy();
+
+    expect(
+      policy.evaluateCommand({
+        command: "git status --short",
+        safe: true,
+      }),
+    ).toMatchObject({
+      permission: "safeCommands",
+      decision: "allow",
+      requiresApproval: false,
+    });
+
+    expect(
+      policy.evaluateCommand({
+        command: "rm -rf dist",
+        safe: false,
+      }),
+    ).toMatchObject({
+      permission: "arbitraryCommands",
+      decision: "deny",
+      requiresApproval: true,
+      reason: 'Permission "arbitraryCommands" is not granted by the active policy.',
+    });
+  });
+
+  it("allows dangerous permissions when explicitly granted", () => {
+    const policy = createDefaultPermissionPolicy({
+      grants: {
+        write: true,
+        network: true,
+      },
+    });
+
+    expect(policy.evaluate({ permission: "write" })).toMatchObject({
+      decision: "allow",
+      requiresApproval: false,
+    });
+    expect(policy.evaluate({ permission: "network" })).toMatchObject({
+      decision: "allow",
+      requiresApproval: false,
+    });
+  });
+});

apps/server/src/security/permission-policy.ts

@@ -0,0 +1,105 @@
+export const PERMISSION_NAMES = [
+  "read",
+  "write",
+  "safeCommands",
+  "arbitraryCommands",
+  "network",
+  "installDependencies",
+  "gitCommit",
+  "gitPush",
+] as const;
+
+export type PermissionName = (typeof PERMISSION_NAMES)[number];
+export type PermissionDecision = "allow" | "deny";
+
+export type PermissionGrants = Readonly<Record<PermissionName, boolean>>;
+
+export interface PermissionEvaluationRequest {
+  readonly permission: PermissionName;
+}
+
+export interface CommandPermissionEvaluationRequest {
+  readonly command: string;
+  readonly safe: boolean;
+}
+
+export interface PermissionEvaluationResult {
+  readonly permission: PermissionName;
+  readonly decision: PermissionDecision;
+  readonly requiresApproval: boolean;
+  readonly reason: string;
+}
+
+export interface PermissionPolicy {
+  readonly grants: PermissionGrants;
+  readonly evaluate: (request: PermissionEvaluationRequest) => PermissionEvaluationResult;
+  readonly evaluateCommand: (
+    request: CommandPermissionEvaluationRequest,
+  ) => PermissionEvaluationResult;
+}
+
+export interface CreateDefaultPermissionPolicyOptions {
+  readonly grants?: Partial<PermissionGrants>;
+}
+
+export const DEFAULT_AGENT_PERMISSION_GRANTS: PermissionGrants = {
+  read: true,
+  write: false,
+  safeCommands: true,
+  arbitraryCommands: false,
+  network: false,
+  installDependencies: false,
+  gitCommit: false,
+  gitPush: false,
+};
+
+const DANGEROUS_PERMISSIONS = new Set<PermissionName>([
+  "write",
+  "arbitraryCommands",
+  "network",
+  "installDependencies",
+  "gitCommit",
+  "gitPush",
+]);
+
+export function createDefaultPermissionPolicy(
+  options: CreateDefaultPermissionPolicyOptions = {},
+): PermissionPolicy {
+  const grants = {
+    ...DEFAULT_AGENT_PERMISSION_GRANTS,
+    ...options.grants,
+  };
+
+  return {
+    grants,
+    evaluate(request) {
+      return evaluatePermission(grants, request.permission);
+    },
+    evaluateCommand(request) {
+      return evaluatePermission(grants, request.safe ? "safeCommands" : "arbitraryCommands");
+    },
+  };
+}
+
+function evaluatePermission(
+  grants: PermissionGrants,
+  permission: PermissionName,
+): PermissionEvaluationResult {
+  const granted = grants[permission];
+
+  if (granted) {
+    return {
+      permission,
+      decision: "allow",
+      requiresApproval: false,
+      reason: `Permission "${permission}" is granted by the active policy.`,
+    };
+  }
+
+  return {
+    permission,
+    decision: "deny",
+    requiresApproval: DANGEROUS_PERMISSIONS.has(permission),
+    reason: `Permission "${permission}" is not granted by the active policy.`,
+  };
+}

docs/development/task-backlog.md

@@ -511,9 +511,9 @@ Status markers:
 
 **Tasks:**
 
-- [ ] Implement permissions for read, write, safe commands, arbitrary commands, network, install dependencies, git commit, and git push.
-- [ ] Require approval for dangerous permissions by default.
-- [ ] Commit with message `feat: add permission policy`.
+- [x] Implement permissions for read, write, safe commands, arbitrary commands, network, install dependencies, git commit, and git push.
+- [x] Require approval for dangerous permissions by default.
+- [x] Commit with message `feat: add permission policy`.
 
 **Acceptance Criteria:**