[spm] add ability to generate hashed OT LC tokens

This updates the SPM to enable generating cSHAKE128 hashed OpenTitan lifecycle tokens using the DeriveSymmetricKeys RPC function. This partially addresses #4. Signed-off-by: Tim Trippel <[email protected]>
lowRISC · Oct 8, 2024 · 892487b · 892487b
1 parent 798f82f
commit 892487b
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Showing 4 changed files with 19 additions and 3 deletions.
diff --git a/src/pa/loadtest.go b/src/pa/loadtest.go
@@ -141,7 +141,7 @@ func (c *clientTask) ot_run(ctx context.Context, numCalls int) {
 			},
 			&pbp.SymmetricKeygenParams{
 				Seed:        pbp.SymmetricKeySeed_SYMMETRIC_KEY_SEED_HIGH_SECURITY,
-				Type:        pbp.SymmetricKeyType_SYMMETRIC_KEY_TYPE_RAW,
+				Type:        pbp.SymmetricKeyType_SYMMETRIC_KEY_TYPE_HASHED_OT_LC_TOKEN,
 				Size:        pbp.SymmetricKeySize_SYMMETRIC_KEY_SIZE_128_BITS,
 				Diversifier: "rma,device_id",
 			},

diff --git a/src/spm/services/BUILD.bazel b/src/spm/services/BUILD.bazel
@@ -60,6 +60,7 @@ go_library(
         "//src/pk11",
         "@org_golang_google_grpc//codes",
         "@org_golang_google_grpc//status",
+        "@org_golang_x_crypto//sha3",
     ],
 )
 
@@ -76,5 +77,6 @@ go_test(
         "@com_github_google_go_cmp//cmp",
         "@com_github_google_tink_go//kwp/subtle:go_default_library",
         "@org_golang_x_crypto//hkdf",
+        "@org_golang_x_crypto//sha3",
     ],
 )
diff --git a/src/spm/services/se_pk11.go b/src/spm/services/se_pk11.go
@@ -13,6 +13,7 @@ import (
 	"fmt"
 	"reflect"
 
+	"golang.org/x/crypto/sha3"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
 
@@ -376,7 +377,14 @@ func (h *HSM) GenerateSymmetricKeys(params []*SymmetricKeygenParams) ([][]byte,
 				"failed to parse extracted symmetric key: %v", ok)
 		}
 		keyBytes := []byte(aesKey)
-		// TODO: format it based on type (i.e. LC token or RAW)
+		if p.KeyType == SymmetricKeyTypeHashedOtLcToken {
+			// OpenTitan lifecycle tokens are stored in OTP in hashed form using the
+			// cSHAKE128 algorithm with the "LC_CTRL" customization string.
+			hasher := sha3.NewCShake128([]byte(""), []byte("LC_CTRL"))
+			hasher.Write(keyBytes)
+			hasher.Read(keyBytes)
+		}
+
 		symmetricKeys = append(symmetricKeys, keyBytes)
 	}
 

diff --git a/src/spm/services/se_pk11_test.go b/src/spm/services/se_pk11_test.go
@@ -21,6 +21,7 @@ import (
 	"github.com/google/go-cmp/cmp"
 	kwp "github.com/google/tink/go/kwp/subtle"
 	"golang.org/x/crypto/hkdf"
+	"golang.org/x/crypto/sha3"
 
 	"github.com/lowRISC/opentitan-provisioning/src/cert/signer"
 	"github.com/lowRISC/opentitan-provisioning/src/cert/templates/tpm"
@@ -103,7 +104,7 @@ func TestGenerateSymmKeys(t *testing.T) {
 	// RMA token
 	rmaTokenParams := SymmetricKeygenParams{
 		UseHighSecuritySeed: true,
-		KeyType:             SymmetricKeyTypeRaw,
+		KeyType:             SymmetricKeyTypeHashedOtLcToken,
 		SizeInBits:          128,
 		Sku:                 "test sku",
 		Diversifier:         "rma: device_id",
@@ -138,6 +139,11 @@ func TestGenerateSymmKeys(t *testing.T) {
 		}
 		expected_key := make([]byte, len(keys[i]))
 		keyGenerator.Read(expected_key)
+		if p.KeyType == SymmetricKeyTypeHashedOtLcToken {
+			hasher := sha3.NewCShake128([]byte(""), []byte("LC_CTRL"))
+			hasher.Write(expected_key)
+			hasher.Read(expected_key)
+		}
 
 		// Check the actual and expected keys are equal.
 		log.Printf("Actual   Key: %q", hex.EncodeToString(keys[i]))