Fix #332: Use URL-safe base64 encoding for session nonces

handler/store_rpc.go

@@ -241,13 +241,13 @@ func (s *StoreRPCClient) GetTrustAnchorIDs(token *proto.AttestationToken) ([]str
 
 	data, err = json.Marshal(token)
 	if err != nil {
-		return []string{""}, fmt.Errorf("marshaling token: %w", err)
+		return nil, fmt.Errorf("marshaling token: %w", err)
 	}
 
 	err = s.client.Call("Plugin.GetTrustAnchorIDs", data, &resp)
 	if err != nil {
 		err = ParseError(err)
-		return []string{""}, fmt.Errorf("Plugin.GetTrustAnchorIDs RPC call failed: %w", err) // nolint
+		return nil, fmt.Errorf("Plugin.GetTrustAnchorIDs RPC call failed: %w", err) // nolint
 	}
 
 	return resp, nil

integration-tests/data/claims/cca.good.json

@@ -35,7 +35,7 @@
     "cca-platform-hash-algo-id": "sha-256"
   },
   "cca-realm-delegated-token": {
-    "cca-realm-challenge": "byTWuWNaLIu/WOkIuU4Ewb+zroDN6+gyQkV4SZ/jF2Hn9eHYvOASGET1Sr36UobaiPU6ZXsVM1yTlrQyklS8XA==",
+    "cca-realm-challenge": "byTWuWNaLIu_WOkIuU4Ewb-zroDN6-gyQkV4SZ_jF2Hn9eHYvOASGET1Sr36UobaiPU6ZXsVM1yTlrQyklS8XA==",
     "cca-realm-personalization-value": "QURBREFEQURBREFEQURBREFEQURBREFEQURBREFEQURBREFEQURBREFEQURBREFEQURBREFEQURBREFEQURBRA==",
     "cca-realm-initial-measurement": "Q0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQw==",
     "cca-realm-extensible-measurements": [

integration-tests/data/results/cca.end-to-end.json

@@ -61,7 +61,7 @@
         "storage-opaque": 0
       },
       "ear.veraison.annotated-evidence": {
-        "cca-realm-challenge": "byTWuWNaLIu/WOkIuU4Ewb+zroDN6+gyQkV4SZ/jF2Hn9eHYvOASGET1Sr36UobaiPU6ZXsVM1yTlrQyklS8XA==",
+        "cca-realm-challenge": "byTWuWNaLIu_WOkIuU4Ewb-zroDN6-gyQkV4SZ_jF2Hn9eHYvOASGET1Sr36UobaiPU6ZXsVM1yTlrQyklS8XA==",
         "cca-realm-extensible-measurements": [
           "Q0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQw==",
           "Q0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQw==",

integration-tests/data/results/cca.good.json

@@ -63,7 +63,7 @@
       "storage-opaque": 0
     },
     "ear.veraison.annotated-evidence": {
-      "cca-realm-challenge": "byTWuWNaLIu/WOkIuU4Ewb+zroDN6+gyQkV4SZ/jF2Hn9eHYvOASGET1Sr36UobaiPU6ZXsVM1yTlrQyklS8XA==",
+      "cca-realm-challenge": "byTWuWNaLIu_WOkIuU4Ewb-zroDN6-gyQkV4SZ_jF2Hn9eHYvOASGET1Sr36UobaiPU6ZXsVM1yTlrQyklS8XA==",
       "cca-realm-extensible-measurements": [
         "Q0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQw==",
         "Q0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQw==",

integration-tests/data/results/cca.verify-challenge.json

@@ -61,7 +61,7 @@
       "storage-opaque": 0
     },
     "ear.veraison.annotated-evidence": {
-      "cca-realm-challenge": "byTWuWNaLIu/WOkIuU4Ewb+zroDN6+gyQkV4SZ/jF2Hn9eHYvOASGET1Sr36UobaiPU6ZXsVM1yTlrQyklS8XA==",
+      "cca-realm-challenge": "byTWuWNaLIu_WOkIuU4Ewb-zroDN6-gyQkV4SZ_jF2Hn9eHYvOASGET1Sr36UobaiPU6ZXsVM1yTlrQyklS8XA==",
       "cca-realm-extensible-measurements": [
         "Q0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQw==",
         "Q0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQ0NDQw==",

integration-tests/docker/Dockerfile

@@ -23,8 +23,18 @@ RUN apt-get update \
     && rm -rf /var/lib/apt/lists/* /var/tmp/* /tmp/* && \
     gem install cbor-diag
 
-RUN userdel -f $(cat /etc/passwd | awk -F: "\$3 == ${TESTER_UID}" | cut -d: -f1); \
-    groupdel -f $(cat /etc/group | awk -F: "\$3 == ${TESTER_GID}" | cut -d: -f1); \
+# Note: unfortunately this does not get packaged as part of the distro (so
+# cannot be installed with apt), and the upstream only provide an amd64 deb, so
+# this will not work on arm64 platforms.
+RUN wget https://dl.step.sm/gh-release/cli/docs-cli-install/v0.23.1/step-cli_0.23.1_amd64.deb && \
+    dpkg -i step-cli_0.23.1_amd64.deb; \
+    rm step-cli_0.23.1_amd64.deb
+
+
+RUN user_to_del=$(awk -F: "\$3 == ${TESTER_UID} {print \$1}" /etc/passwd) && \
+    [ -n "$user_to_del" ] && userdel -f "$user_to_del" || true && \
+    group_to_del=$(awk -F: "\$3 == ${TESTER_GID} {print \$1}" /etc/group) && \
+    [ -n "$group_to_del" ] && groupdel -f "$group_to_del" || true && \
     groupadd -g ${TESTER_GID} tavern && \
     groupadd -g 616 veraison && \
     useradd -m -u ${TESTER_UID} -g tavern -G veraison \

integration-tests/utils/checkers.py

@@ -38,6 +38,7 @@ def compare_to_expected_result(response, expected, verifier_key):
             print("Key exists in the dictionary.")
         except KeyError:
             print(f"Key {key} does not exist in the dictionary.")
+            raise
 
         assert decoded_claims["ear.status"] == expected_claims["ear.status"]
         print(f"Evaluating Submod with SubModName {key}")

integration-tests/utils/generators.py

@@ -128,18 +128,18 @@ def generate_evidence(scheme, evidence, nonce, signing, outname):
 
     if scheme == 'psa' and nonce:
         claims_file = f'{GENDIR}/claims/{scheme}.{evidence}.json'
+        # Use nonce directly as URL-safe base64 to match verification API
         update_json(
                 f'data/claims/{scheme}.{evidence}.json',
                 {f'{scheme}-nonce': nonce},
                 claims_file,
                 )
     elif scheme == 'cca' and nonce:
         claims_file = f'{GENDIR}/claims/{scheme}.{evidence}.json'
-        # convert nonce from base64url to base64
-        translated_nonce = nonce.replace('-', '+').replace('_', '/')
+        # Use nonce directly as URL-safe base64 to match verification API
         update_json(
                 f'data/claims/{scheme}.{evidence}.json',
-                {'cca-realm-delegated-token': {f'cca-realm-challenge': translated_nonce}},
+                {'cca-realm-delegated-token': {f'cca-realm-challenge': nonce}},
                 claims_file,
                 )
     else:

log/hclogger.go

@@ -1,4 +1,4 @@
-// Copyright 2022-2023 Contributors to the Veraison project.
+// Copyright 2022-2025 Contributors to the Veraison project.
 // SPDX-License-Identifier: Apache-2.0
 package log
 

scheme/arm-cca/store_handler.go

@@ -48,16 +48,16 @@ func (s StoreHandler) SynthKeysFromTrustAnchor(tenantID string, ta *handler.Endo
 func (s StoreHandler) GetTrustAnchorIDs(token *proto.AttestationToken) ([]string, error) {
 	evidence, err := ccatoken.DecodeAndValidateEvidenceFromCBOR(token.Data)
 	if err != nil {
-		return []string{""}, handler.BadEvidence(err)
+		return nil, handler.BadEvidence(err)
 	}
 
 	claims := evidence.PlatformClaims
 	if err != nil {
-		return []string{""}, err
+		return nil, err
 	}
 	taID, err := arm.GetTrustAnchorID(SchemeName, token.TenantId, claims)
 	if err != nil {
-		return []string{""}, err
+		return nil, err
 	}
 
 	return []string{taID}, nil

scheme/parsec-cca/store_handler.go

@@ -43,13 +43,13 @@ func (s StoreHandler) GetTrustAnchorIDs(token *proto.AttestationToken) ([]string
 
 	err := evidence.FromCBOR(token.Data)
 	if err != nil {
-		return []string{""}, handler.BadEvidence(err)
+		return nil, handler.BadEvidence(err)
 	}
 	claims := evidence.Pat.PlatformClaims
 
 	taID, err := arm.GetTrustAnchorID(SchemeName, token.TenantId, claims)
 	if err != nil {
-		return []string{""}, err
+		return nil, err
 	}
 
 	return []string{taID}, nil

scheme/parsec-tpm/store_handler.go

@@ -42,12 +42,12 @@ func (s StoreHandler) GetTrustAnchorIDs(token *proto.AttestationToken) ([]string
 	var ev tpm.Evidence
 	err := ev.FromCBOR(token.Data)
 	if err != nil {
-		return []string{""}, handler.BadEvidence(err)
+		return nil, handler.BadEvidence(err)
 	}
 
 	kat := ev.Kat
 	if kat == nil {
-		return []string{""}, errors.New("no key attestation token to fetch Key ID")
+		return nil, errors.New("no key attestation token to fetch Key ID")
 	}
 	kid := *kat.KID
 	instance_id := base64.StdEncoding.EncodeToString(kid)

scheme/psa-iot/store_handler.go

@@ -38,14 +38,14 @@ func (s StoreHandler) SynthKeysFromTrustAnchor(tenantID string, ta *handler.Endo
 func (s StoreHandler) GetTrustAnchorIDs(token *proto.AttestationToken) ([]string, error) {
 	psaToken, err := psatoken.DecodeAndValidateEvidenceFromCOSE(token.Data)
 	if err != nil {
-		return []string{""}, handler.BadEvidence(err)
+		return nil, handler.BadEvidence(err)
 	}
 
 	claims := psaToken.Claims
 
 	taID, err := arm.GetTrustAnchorID(SchemeName, token.TenantId, claims)
 	if err != nil {
-		return []string{""}, err
+		return nil, err
 	}
 
 	return []string{taID}, nil

scheme/tpm-enacttrust/store_handler.go

@@ -43,7 +43,7 @@ func (s StoreHandler) GetTrustAnchorIDs(token *proto.AttestationToken) ([]string
 			strings.Join(EvidenceMediaTypes, ", "),
 			token.MediaType,
 		)
-		return []string{""}, err
+		return nil, err
 	}
 
 	var decoded Token

verification/api/challengeresponsesession.go

@@ -1,11 +1,12 @@
-// Copyright 2022-2023 Contributors to the Veraison project.
+// Copyright 2022-2025 Contributors to the Veraison project.
 // SPDX-License-Identifier: Apache-2.0
 
 // The api package implements the REST API defined in
 // https://github.com/veraison/docs/blob/main/api/challenge-response
 package api
 
 import (
+	"encoding/base64"
 	"encoding/json"
 	"fmt"
 	"time"
@@ -64,6 +65,32 @@ func (o *Status) UnmarshalJSON(b []byte) error {
 	return o.FromString(s)
 }
 
+// URLSafeNonce is a wrapper around []byte that marshals/unmarshals using URL-safe base64
+type URLSafeNonce []byte
+
+func (n URLSafeNonce) MarshalJSON() ([]byte, error) {
+	if n == nil {
+		return []byte("null"), nil
+	}
+	encoded := base64.URLEncoding.EncodeToString(n)
+	return json.Marshal(encoded)
+}
+
+func (n *URLSafeNonce) UnmarshalJSON(data []byte) error {
+	var s string
+	if err := json.Unmarshal(data, &s); err != nil {
+		return err
+	}
+
+	decoded, err := base64.URLEncoding.DecodeString(s)
+	if err != nil {
+		return err
+	}
+
+	*n = URLSafeNonce(decoded)
+	return nil
+}
+
 type EvidenceBlob struct {
 	Type  string `json:"type"`
 	Value []byte `json:"value"`
@@ -72,7 +99,7 @@ type EvidenceBlob struct {
 type ChallengeResponseSession struct {
 	id       string
 	Status   Status        `json:"status"`
-	Nonce    []byte        `json:"nonce"`
+	Nonce    URLSafeNonce  `json:"nonce"`
 	Expiry   time.Time     `json:"expiry"`
 	Accept   []string      `json:"accept"`
 	Evidence *EvidenceBlob `json:"evidence,omitempty"`

verification/api/handler.go

@@ -1,4 +1,4 @@
-// Copyright 2022-2024 Contributors to the Veraison project.
+// Copyright 2022-2025 Contributors to the Veraison project.
 // SPDX-License-Identifier: Apache-2.0
 package api
 
@@ -168,7 +168,7 @@ func newSession(nonce []byte, supportedMediaTypes []string, ttl time.Duration) (
 	session := &ChallengeResponseSession{
 		id:     id.String(),
 		Status: StatusWaiting, // start in waiting status
-		Nonce:  nonce,
+		Nonce:  URLSafeNonce(nonce),
 		Expiry: time.Now().Add(ttl), // RFC3339 format, with sub-second precision added if present
 		Accept: supportedMediaTypes,
 	}
@@ -394,7 +394,7 @@ func (o *Handler) SubmitEvidence(c *gin.Context) {
 	// reported if something in the verifier or the connection goes wrong.
 	// Any problems with the evidence are expected to be reported via the
 	// attestation result.
-	attestationResult, err := o.Verifier.ProcessEvidence(tenantID, session.Nonce,
+	attestationResult, err := o.Verifier.ProcessEvidence(tenantID, []byte(session.Nonce),
 		evidence, mediaType)
 	if err != nil {
 		o.logger.Error(err)

verification/api/handler_test.go

@@ -1,4 +1,4 @@
-// Copyright 2022-2024 Contributors to the Veraison project.
+// Copyright 2022-2025 Contributors to the Veraison project.
 // SPDX-License-Identifier: Apache-2.0
 package api
 
@@ -45,7 +45,7 @@ var (
 	testJSONBody                  = `{ "k": "v" }`
 	testSession                   = `{
 	"status": "waiting",
-	"nonce": "mVubqtg3Wa5GSrx3L/2B99cQU2bMQFVYUI9aTmDYi64=",
+	"nonce": "mVubqtg3Wa5GSrx3L_2B99cQU2bMQFVYUI9aTmDYi64=",
 	"expiry": "2022-07-13T13:50:24.520525+01:00",
 	"accept": [
 		"application/eat_cwt;profile=http://arm.com/psa/2.0.0",
@@ -61,7 +61,7 @@ var (
 }`
 	testProcessingSession = `{
 	"status": "processing",
-	"nonce": "mVubqtg3Wa5GSrx3L/2B99cQU2bMQFVYUI9aTmDYi64=",
+	"nonce": "mVubqtg3Wa5GSrx3L_2B99cQU2bMQFVYUI9aTmDYi64=",
 	"expiry": "2022-07-13T13:50:24.520525+01:00",
 	"accept": [
 		"application/eat_cwt;profile=http://arm.com/psa/2.0.0",
@@ -75,7 +75,7 @@ var (
 }`
 	testCompleteSession = `{
 	"status": "complete",
-	"nonce": "mVubqtg3Wa5GSrx3L/2B99cQU2bMQFVYUI9aTmDYi64=",
+	"nonce": "mVubqtg3Wa5GSrx3L_2B99cQU2bMQFVYUI9aTmDYi64=",
 	"expiry": "2022-07-13T13:50:24.520525+01:00",
 	"accept": [
 		"application/eat_cwt;profile=http://arm.com/psa/2.0.0",
@@ -289,12 +289,42 @@ func TestHandler_NewChallengeResponse_NonceParameter(t *testing.T) {
 	assert.Equal(t, expectedCode, w.Code)
 	assert.Equal(t, expectedType, w.Result().Header.Get("Content-Type"))
 	assert.Regexp(t, expectedLocationRE, w.Result().Header.Get("Location"))
-	assert.Equal(t, expectedNonce, body.Nonce)
+	assert.Equal(t, expectedNonce, []byte(body.Nonce))
 	assert.Nil(t, body.Evidence)
 	assert.Nil(t, body.Result)
 	assert.Equal(t, expectedSessionStatus, body.Status)
 }
 
+func TestURLSafeNonce_EncodingFormat(t *testing.T) {
+	// Test that nonces with characters that would be URL-unsafe in standard base64
+	// are properly encoded as URL-safe base64
+	testNonce := []byte{0x99, 0x5b, 0x9b, 0xaa, 0xd8, 0x37, 0x59, 0xae,
+		0x46, 0x4a, 0xbc, 0x77, 0x2f, 0xfd, 0x81, 0xf7,
+		0xd7, 0x10, 0x53, 0x66, 0xcc, 0x40, 0x55, 0x58,
+		0x50, 0x8f, 0x5a, 0x4e, 0x60, 0xd8, 0x8b, 0xae}
+
+	urlSafeNonce := URLSafeNonce(testNonce)
+	jsonBytes, err := json.Marshal(urlSafeNonce)
+	require.NoError(t, err)
+
+	jsonStr := string(jsonBytes)
+	t.Logf("Encoded nonce: %s", jsonStr)
+
+	// Should not contain URL-unsafe characters '+' or '/'
+	assert.NotContains(t, jsonStr, "+", "Nonce should not contain '+' character")
+	assert.NotContains(t, jsonStr, "/", "Nonce should not contain '/' character")
+
+	// Should contain URL-safe alternatives '_' and '-' instead
+	// Note: This specific test nonce should contain '_' character
+	assert.Contains(t, jsonStr, "_", "URL-safe nonce should contain '_' character")
+
+	// Test round-trip: unmarshal and compare
+	var unmarshaled URLSafeNonce
+	err = json.Unmarshal(jsonBytes, &unmarshaled)
+	require.NoError(t, err)
+	assert.Equal(t, testNonce, []byte(unmarshaled), "Round-trip encoding should preserve nonce data")
+}
+
 func TestHandler_NewChallengeResponse_NonceSizeParameter(t *testing.T) {
 	ctrl := gomock.NewController(t)
 	defer ctrl.Finish()

vts/trustedservices/trustedservices_grpc.go

@@ -442,7 +442,6 @@ func (o *GRPC) GetAttestation(
 
 	var multEndorsements []string
 	for _, refvalID := range appraisal.EvidenceContext.ReferenceIds {
-
 		endorsements, err := o.EnStore.Get(refvalID)
 		if err != nil && !errors.Is(err, kvstore.ErrKeyNotFound) {
 			return o.finalize(appraisal, err)
@@ -507,12 +506,12 @@ func (c *GRPC) getTrustAnchors(id []string) ([]string, error) {
 	for _, taID := range id {
 		values, err := c.TaStore.Get(taID)
 		if err != nil {
-			return []string{""}, err
+			return nil, err
 		}
 
 		// For now, Veraison schemes only support one trust anchor per trustAnchorID
 		if len(values) != 1 {
-			return []string{""}, fmt.Errorf("found %d trust anchors, want 1", len(values))
+			return nil, fmt.Errorf("found %d trust anchors, want 1", len(values))
 		}
 		taValues = append(taValues, values[0])
 	}