Pad SHA-256 attestation report data

Author: h4x3rotab

consul-postgres-ha/ATTESTATION.md

@@ -40,11 +40,13 @@ current dstack guest agents: `quote`, `event_log`, and `vm_config`.
 
 ## Report Data
 
-`report_data` is an unstructured SHA-256 digest. The structured
-admission data stays outside the quote in the binding statement:
+`report_data` is the 64-byte TDX REPORTDATA field. The structured
+admission data stays outside the quote in the binding statement.
+The first 32 bytes are a SHA-256 digest; the remaining 32 bytes are
+zero padding:
 
 ```text
-report_data = SHA-256(binding_statement_json || broker_nonce)
+report_data = SHA-256(binding_statement_json || broker_nonce) || 32 zero bytes
 ```
 
 The broker nonce is 32 random bytes encoded as hex. The binding

consul-postgres-ha/PROGRESS.md

@@ -60,7 +60,8 @@ deployment model, trust model, or operational status.
 
 - Workload identity is the Terraform-declared identity; compose hash
   is revision evidence, not the workload key.
-- `report_data` is `SHA-256(binding_statement_json || nonce)`.
+- `report_data` is the 64-byte TDX REPORTDATA field:
+  `SHA-256(binding_statement_json || nonce) || 32 zero bytes`.
 - The broker relies on `dstack-verifier` for quote and event-log
   semantics. It does not parse raw RTMR event-log internals itself.
 - `peer_id` is the logical mesh/Consul node label, for example

consul-postgres-ha/admission-broker/main.go

@@ -344,7 +344,10 @@ func reportDataHex(bindingHex, nonceHex string) (string, error) {
 	h := sha256.New()
 	h.Write(binding)
 	h.Write(nonce)
-	return hex.EncodeToString(h.Sum(nil)), nil
+	digest := h.Sum(nil)
+	reportData := make([]byte, 64)
+	copy(reportData, digest)
+	return hex.EncodeToString(reportData), nil
 }
 
 func rawJSONAsString(raw json.RawMessage) string {

consul-postgres-ha/admission-broker/main_test.go

@@ -123,7 +123,9 @@ func TestReportDataHexBindsStatementAndNonce(t *testing.T) {
 	h := sha256.New()
 	h.Write(bindingBytes)
 	h.Write(nonceBytes)
-	want := hex.EncodeToString(h.Sum(nil))
+	wantBytes := make([]byte, 64)
+	copy(wantBytes, h.Sum(nil))
+	want := hex.EncodeToString(wantBytes)
 	if got != want {
 		t.Fatalf("report_data mismatch\nwant %s\n got %s", want, got)
 	}

consul-postgres-ha/admission-client/main.go

@@ -240,7 +240,10 @@ func reportData(statementBytes []byte, nonceHex string) ([]byte, error) {
 	h := sha256.New()
 	h.Write(statementBytes)
 	h.Write(nonce)
-	return h.Sum(nil), nil
+	digest := h.Sum(nil)
+	reportData := make([]byte, 64)
+	copy(reportData, digest)
+	return reportData, nil
 }
 
 func writeToken(path, token string) error {

consul-postgres-ha/admission-client/main_test.go

@@ -26,7 +26,9 @@ func TestReportDataBindsStatementAndNonce(t *testing.T) {
 	h := sha256.New()
 	h.Write(statement)
 	h.Write(nonceBytes)
-	if !bytes.Equal(got, h.Sum(nil)) {
+	want := make([]byte, 64)
+	copy(want, h.Sum(nil))
+	if !bytes.Equal(got, want) {
 		t.Fatalf("report data mismatch")
 	}
 }

consul-postgres-ha/design/attestation-admission.md

@@ -141,10 +141,11 @@ The broker validates:
 1. **Quote chain**: TDX → Intel PCS root, via a sibling
    `dstack-verifier` HTTP service.
 2. **`report_data` binding**: must equal
-   `SHA-256(binding_statement || nonce)`. Anything else means the
-   quote was generated for a different handshake; reject. The broker
-   also verifies that the statement identity equals the claimed
-   identity.
+   `SHA-256(binding_statement || nonce)` placed in the first 32 bytes
+   of the 64-byte TDX REPORTDATA field, with the remaining 32 bytes
+   zero padded. Anything else means the quote was generated for a
+   different handshake; reject. The broker also verifies that the
+   statement identity equals the claimed identity.
 3. **Nonce freshness**: must be a nonce the broker issued
    recently and hasn't been consumed.
 4. **Verifier event-log result**: require `event_log_verified` from
@@ -328,7 +329,7 @@ client agent itself, then for each declared service identity.
 
 3. POST /v1/admission/challenge to broker. Receive nonce.
 
-4. report_data = SHA-256(binding_statement || nonce)
+4. report_data = SHA-256(binding_statement || nonce) || 32 zero bytes
    Call dstack GetQuote(report_data). Receive quote, event_log,
    vm_config, and report_data.