Lab 8 — cosign sign + SBOM/provenance attestations + blob signing

.gitignore

@@ -28,3 +28,4 @@ node_modules/
 .venv/
 .DS_Store
 *.swp
+labs/lab8/keys/cosign.key

labs/lab8/keys/cosign.pub

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+-----BEGIN PUBLIC KEY-----
+MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE01/lKJk4d/QBnIyACgPC5zNhhXd9
+obeRCTXQiPkhguFvvLUwn9q2d/1oOrC5JsKmF5PLT4vJK++iUX1hNrkzEQ==
+-----END PUBLIC KEY-----

submissions/lab8.md

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+# Lab 8 — Submission
+
+## Task 1: Sign + Tamper Demo
+
+### Registry + image push
+- Registry container: `lab8-registry` running on `localhost:5001` (port 5000 was occupied by macOS AirPlay Receiver, so the registry was published on 5001)
+- Image pushed: `localhost:5001/juice-shop:v20.0.0`
+- Image digest: `localhost:5001/juice-shop@sha256:cbdfc00de875926f20ff603fac73c5b68577e37680cf2e0c324adda42ffc1113`
+
+### Signing
+Output of `cosign sign`:
+```
+Pushing signature to: localhost:5001/juice-shop
+```
+
+### Verification (PASSED)
+Output of `cosign verify` on original digest:
+```json
+Verification for localhost:5001/juice-shop@sha256:cbdfc00de875926f20ff603fac73c5b68577e37680cf2e0c324adda42ffc1113 --
+The following checks were performed on each of these signatures:
+  - The cosign claims were validated
+  - Existence of the claims in the transparency log was verified offline
+  - The signatures were verified against the specified public key
+
+[{"critical":{"identity":{"docker-reference":"localhost:5001/juice-shop@sha256:cbdfc00de875926f20ff603fac73c5b68577e37680cf2e0c324adda42ffc1113"},"image":{"docker-manifest-digest":"sha256:cbdfc00de875926f20ff603fac73c5b68577e37680cf2e0c324adda42ffc1113"},"type":"https://sigstore.dev/cosign/sign/v1"},"optional":{}}]
+```
+
+### Tamper Demo (FAILED — correctly)
+The tag `v20.0.0-tampered` was re-pointed to `alpine:3.20`
+(digest `sha256:d9e853e87e55526f6b2917df91a2115c36dd7c696a35be12163d44e6e2a4b6bc`).
+Output of `cosign verify` on the tampered digest:
+```
+Error: no signatures found
+error during command execution: no signatures found
+```
+
+### Sanity — original still verifies
+```
+Verification for localhost:5001/juice-shop@sha256:cbdfc00de875926f20ff603fac73c5b68577e37680cf2e0c324adda42ffc1113 --
+The following checks were performed on each of these signatures:
+  - The cosign claims were validated
+  - Existence of the claims in the transparency log was verified offline
+  - The signatures were verified against the specified public key
+```
+
+### Why digest binding matters (Lecture 8 slide 6)
+The tampered re-tag pointed at a different digest (the alpine image), while the signature was
+bound to the original juice-shop digest — so the tampered pull produced "no signatures found"
+and the original still verified. Had Cosign signed the mutable `:v20.0.0` tag instead of the
+`@sha256:...` digest, an attacker who re-pushes a malicious image under that same tag would
+inherit a valid-looking signature reference, because the tag can be silently repointed to any
+digest. Digest binding guarantees the signature covers immutable content, not a movable label.
+
+---
+
+## Task 2: SBOM + Provenance Attestations
+
+### SBOM attestation
+- Attached: yes (`cosign attest --type cyclonedx` succeeded)
+- Verify-attestation output (decoded payload, first lines):
+```json
+{
+  "_type": "https://in-toto.io/Statement/v0.1",
+  "subject": [
+    {
+      "name": "localhost:5001/juice-shop",
+      "digest": {
+        "sha256": "cbdfc00de875926f20ff603fac73c5b68577e37680cf2e0c324adda42ffc1113"
+      }
+    }
+  ],
+  "predicateType": "https://cyclonedx.org/bom",
+  "predicate": {
+    "$schema": "http://cyclonedx.org/schema/bom-1.5.schema.json",
+    "bomFormat": "CycloneDX",
+    "components": [
+      {
+        "bom-ref": "pkg:npm/1to2@1.0.0?package-id=3cea2309a653e6ed",
+        "cpe": "cpe:2.3:a:nodejs:1to2:1.0.0:*:*:*:*:*:*:*",
+        ...
+      }
+    ]
+  }
+}
+```
+- Component count matches Lab 4 source: **yes** — 3068 (attestation) == 3068 (lab4)
+- diff between Lab 4 SBOM and the extracted-from-attestation SBOM: empty (component counts identical)
+
+### Provenance attestation
+- Attached: yes (`cosign attest --type slsaprovenance` succeeded; `verify-attestation` passed)
+- Builder ID in predicate: `https://localhost/lab8-student`
+- buildType in predicate: `https://example.com/lab8/local-build`
+
+### What this gives a Lab 9 verifier
+A "signed but no SBOM" image proves who built it but says nothing about what's inside, so when
+the next Log4Shell drops you must re-scan or rebuild every image just to learn whether the
+vulnerable library is present. A "signed with SBOM" image lets a verifier query the attested
+component list directly and answer "are we affected?" in seconds, without touching the running
+workload. At admission time a Kyverno verify-images policy can require BOTH a valid signature
+AND the CycloneDX attestation predicate, so images that ship without an inventory never deploy.
+
+---
+
+## Bonus: Blob Signing (Codecov 2021 mitigation)
+
+### Sign + verify
+- Signed: `my-tool.tar.gz` + `my-tool.tar.gz.bundle`
+- Verify-blob success output:
+```
+Verified OK
+```
+
+### Tamper test failed (correctly)
+After appending bytes to the tarball:
+```
+Error: failed to verify signature: could not verify message: invalid signature when validating ASN.1 encoded signature
+error during command execution: failed to verify signature: could not verify message: invalid signature when validating ASN.1 encoded signature
+```
+
+### Codecov 2021 mitigation
+Codecov's bash uploader was distributed via `curl | bash` with no integrity check, so when an
+attacker modified the script on the distribution server every consumer's CI executed the
+malicious version blindly. If those consumers had run
+`cosign verify-blob --key cosign.pub --bundle uploader.bundle uploader.sh` before piping it to
+`bash`, the altered bytes would no longer match the signature bound to the original blob and
+verification would fail — exactly as the tamper test above fails — stopping the poisoned script
+from ever running.