fix: scope s3:ListBucket to the releases/ prefix (F-1/IAC-04)

The instance role and the GitHub deploy app role granted s3:ListBucket on the
whole assets bucket. Every caller (deploy.sh, the publish/rollback scripts)
only ever lists under releases/, so add a StringLike s3:prefix=releases/*
condition. GetBucketLocation has no s3:prefix in its request context, so it
moves to its own unconditioned statement. Also document the accepted F-2
cross-env existence-oracle residual on BatchGetSecretValue.

infra/lib/constructs/github-deploy-roles.ts

@@ -150,10 +150,22 @@ export class GithubDeployRoles extends Construct {
         resources: [`arn:aws:s3:::open-swe-${envName}-assets/releases/*`],
       }),
     );
+    // ListBucket is constrained to the releases/ prefix (F-1/IAC-04): the
+    // publish/rollback scripts only ever list under releases/, so a leaked CI
+    // token cannot enumerate anything else in the bucket. GetBucketLocation
+    // carries no s3:prefix, so it stays a separate, unconditioned statement.
     this.appRole.addToPolicy(
       new iam.PolicyStatement({
         sid: "ListArtifactBucket",
-        actions: ["s3:ListBucket", "s3:GetBucketLocation"],
+        actions: ["s3:ListBucket"],
+        resources: [`arn:aws:s3:::open-swe-${envName}-assets`],
+        conditions: { StringLike: { "s3:prefix": ["releases/*"] } },
+      }),
+    );
+    this.appRole.addToPolicy(
+      new iam.PolicyStatement({
+        sid: "GetArtifactBucketLocation",
+        actions: ["s3:GetBucketLocation"],
         resources: [`arn:aws:s3:::open-swe-${envName}-assets`],
       }),
     );

infra/lib/constructs/instance-role.ts

@@ -43,10 +43,23 @@ export class InstanceRole extends Construct {
         resources: [`arn:aws:s3:::${p}-assets/releases/*`],
       }),
     );
+    // ListBucket is constrained to the releases/ prefix (F-1/IAC-04) — the box
+    // only ever lists release artifacts, so a compromised box cannot enumerate
+    // any other object that might land in the bucket. GetBucketLocation has no
+    // s3:prefix in its request context, so it stays a separate, unconditioned
+    // statement (the condition would otherwise AccessDeny it).
     this.role.addToPolicy(
       new iam.PolicyStatement({
         sid: "ListArtifactBucket",
-        actions: ["s3:ListBucket", "s3:GetBucketLocation"],
+        actions: ["s3:ListBucket"],
+        resources: [`arn:aws:s3:::${p}-assets`],
+        conditions: { StringLike: { "s3:prefix": ["releases/*"] } },
+      }),
+    );
+    this.role.addToPolicy(
+      new iam.PolicyStatement({
+        sid: "GetArtifactBucketLocation",
+        actions: ["s3:GetBucketLocation"],
         resources: [`arn:aws:s3:::${p}-assets`],
       }),
     );
@@ -85,6 +98,11 @@ export class InstanceRole extends Construct {
     // holds. The win that DID survive: fetch-config uses `--secret-id-list` (explicit
     // names, no name filter), so `secretsmanager:ListSecrets` is NOT needed and is
     // intentionally omitted — the box cannot enumerate secret names account-wide.
+    // F-2 (accepted residual): because the grant is `*`, a caller naming a secret
+    // in ANOTHER env's prefix learns whether that name EXISTS (an existence oracle
+    // via the per-secret AccessDenied-vs-not signal) even though the VALUE stays
+    // gated by the prefix-scoped GetSecretValue above. Accepted within Sea Haven's
+    // single-tenant account 328440206208 — cross-env VALUE isolation is preserved.
     this.role.addToPolicy(
       new iam.PolicyStatement({
         sid: "BatchGetSecretValues",

infra/test/s3-list-prefix.test.ts

@@ -0,0 +1,71 @@
+import * as cdk from "aws-cdk-lib";
+import { Match, Template } from "aws-cdk-lib/assertions";
+import { OpenSweIamStack } from "../lib/open-swe-iam-stack";
+import { OpenSweStack } from "../lib/open-swe-stack";
+
+const ENV = { account: "328440206208", region: "us-east-1" };
+
+// F-1 / IAC-04: s3:ListBucket must be constrained to the releases/ prefix so a
+// compromised box / leaked CI token cannot enumerate the rest of the bucket.
+const RELEASES_PREFIX_CONDITION = { StringLike: { "s3:prefix": ["releases/*"] } };
+
+describe("S3 ListBucket prefix scoping (F-1/IAC-04)", () => {
+  it("instance role ListBucket is constrained to releases/*", () => {
+    const app = new cdk.App();
+    const stack = new OpenSweStack(app, "OpenSweDevStack", {
+      stackName: "open-swe-dev",
+      env: ENV,
+      envName: "dev",
+    });
+    Template.fromStack(stack).hasResourceProperties("AWS::IAM::Policy", {
+      PolicyDocument: Match.objectLike({
+        Statement: Match.arrayWith([
+          Match.objectLike({
+            Sid: "ListArtifactBucket",
+            Action: "s3:ListBucket",
+            Condition: RELEASES_PREFIX_CONDITION,
+          }),
+        ]),
+      }),
+    });
+  });
+
+  it("github deploy app role ListBucket is constrained to releases/*", () => {
+    const app = new cdk.App();
+    const stack = new OpenSweIamStack(app, "OpenSweIamStack", {
+      stackName: "open-swe-iam",
+      env: ENV,
+    });
+    Template.fromStack(stack).hasResourceProperties("AWS::IAM::Policy", {
+      PolicyDocument: Match.objectLike({
+        Statement: Match.arrayWith([
+          Match.objectLike({
+            Sid: "ListArtifactBucket",
+            Action: "s3:ListBucket",
+            Condition: RELEASES_PREFIX_CONDITION,
+          }),
+        ]),
+      }),
+    });
+  });
+
+  it("GetBucketLocation stays a separate, unconditioned statement", () => {
+    const app = new cdk.App();
+    const stack = new OpenSweStack(app, "OpenSweDevStack", {
+      stackName: "open-swe-dev",
+      env: ENV,
+      envName: "dev",
+    });
+    Template.fromStack(stack).hasResourceProperties("AWS::IAM::Policy", {
+      PolicyDocument: Match.objectLike({
+        Statement: Match.arrayWith([
+          Match.objectLike({
+            Sid: "GetArtifactBucketLocation",
+            Action: "s3:GetBucketLocation",
+            Condition: Match.absent(),
+          }),
+        ]),
+      }),
+    });
+  });
+});