pkcs11: Change how unavailable attributes like CKA_TRUSTED are handled

If a PKCS#11 library/token doesn't provide one or more attributes via
C_GetAttributeValue(), we get back CKR_ATTRIBUTE_TYPE_INVALID (similar
for protected attributes where CKR_ATTRIBUTE_SENSITIVE is returned).
This is not an error as the spec demands that all attributes have been
processed with the unavailable attributes having set their length
field to CK_UNAVAILABLE_INFORMATION.

We use this to handle the CKA_TRUSTED attribute, which some tokens
apparently don't support.  We previously used a version check to remove
the attribute from the call but even the latest spec doesn't make the
attribute mandatory (it's just in a list of "common" attributes for
CKO_CERTIFICATE objects, without a default value), so there are current
tokens that don't support it and prevent us from enumerating certificates.

src/libstrongswan/plugins/pkcs11/pkcs11_creds.c

@@ -83,21 +83,21 @@ static void find_certificates(private_pkcs11_creds_t *this,
 
 	/* store result in a temporary list, avoid recursive operation */
 	raw = linked_list_create();
-	/* do not use trusted argument if not supported */
-	if (!(this->lib->get_features(this->lib) & PKCS11_TRUSTED_CERTS))
-	{
-		count--;
-	}
 	enumerator = this->lib->create_object_enumerator(this->lib,
 									session, tmpl, countof(tmpl), attr, count);
 	while (enumerator->enumerate(enumerator, &object))
 	{
-		entry = malloc(sizeof(*entry));
+		if (attr[0].ulValueLen == CK_UNAVAILABLE_INFORMATION ||
-		entry->value = chunk_clone(
+			attr[1].ulValueLen == CK_UNAVAILABLE_INFORMATION)
-							chunk_create(attr[0].pValue, attr[0].ulValueLen));
+		{
-		entry->label = chunk_clone(
+			continue;
-							chunk_create(attr[1].pValue, attr[1].ulValueLen));
+		}
-		entry->trusted = trusted;
+		INIT(entry,
+			.value = chunk_clone(chunk_create(attr[0].pValue, attr[0].ulValueLen)),
+			.label = chunk_clone(chunk_create(attr[1].pValue, attr[1].ulValueLen)),
+			/* assume trusted certificates if attribute is not available */
+			.trusted = attr[2].ulValueLen == CK_UNAVAILABLE_INFORMATION || trusted,
+		);
 		raw->insert_last(raw, entry);
 	}
 	enumerator->destroy(enumerator);
@@ -339,7 +339,8 @@ certificate_t *pkcs11_creds_load(certificate_type_t type, va_list args)
 		}
 		certs = p11->create_object_enumerator(p11, session,
 									tmpl, countof(tmpl), attr, countof(attr));
-		if (certs->enumerate(certs, &object))
+		if (certs->enumerate(certs, &object) &&
+			attr[0].ulValueLen != CK_UNAVAILABLE_INFORMATION)
 		{
 			data = chunk_clone(chunk_create(attr[0].pValue, attr[0].ulValueLen));
 		}

src/libstrongswan/plugins/pkcs11/pkcs11_library.c

@@ -624,6 +624,8 @@ typedef struct {
 	pkcs11_library_t *lib;
 	/* attributes to retrieve */
 	CK_ATTRIBUTE_PTR attr;
+	/* copy of the original attributes provided by the caller */
+	CK_ATTRIBUTE_PTR orig_attr;
 	/* number of attributes */
 	CK_ULONG count;
 	/* object handle in case of a single object */
@@ -633,17 +635,36 @@ typedef struct {
 } object_enumerator_t;
 
 /**
- * Free contents of attributes in a list
+ * Keep a copy of the original attribute values so we can restore them while
+ * enumerating e.g. if an attribute was unavailable for a particular object.
+ */
+static void init_attrs(object_enumerator_t *this)
+{
+	int i;
+
+	this->orig_attr = calloc(this->count, sizeof(CK_ATTRIBUTE));
+	for (i = 0; i < this->count; i++)
+	{
+		this->orig_attr[i] = this->attr[i];
+	}
+}
+
+/**
+ * Free contents of allocated attributes and reset them to their original
+ * values.
  */
 static void free_attrs(object_enumerator_t *this)
 {
 	CK_ATTRIBUTE_PTR attr;
+	int i;
 
 	while (this->freelist->remove_last(this->freelist, (void**)&attr) == SUCCESS)
 	{
 		free(attr->pValue);
-		attr->pValue = NULL;
+	}
-		attr->ulValueLen = 0;
+	for (i = 0; i < this->count; i++)
+	{
+		this->attr[i] = this->orig_attr[i];
 	}
 }
 
@@ -687,7 +708,9 @@ static bool get_attributes(object_enumerator_t *this, CK_OBJECT_HANDLE object)
 	/* get length of objects first */
 	rv = this->lib->f->C_GetAttributeValue(this->session, object,
 										   this->attr, this->count);
-	if (rv != CKR_OK)
+	if (rv != CKR_OK &&
+		rv != CKR_ATTRIBUTE_SENSITIVE &&
+		rv != CKR_ATTRIBUTE_TYPE_INVALID)
 	{
 		DBG1(DBG_CFG, "C_GetAttributeValue(NULL) error: %N", ck_rv_names, rv);
 		return FALSE;
@@ -695,8 +718,12 @@ static bool get_attributes(object_enumerator_t *this, CK_OBJECT_HANDLE object)
 	/* allocate required chunks */
 	for (i = 0; i < this->count; i++)
 	{
-		if (this->attr[i].pValue == NULL &&
+		if (this->attr[i].ulValueLen == CK_UNAVAILABLE_INFORMATION)
-			this->attr[i].ulValueLen != 0 && this->attr[i].ulValueLen != -1)
+		{	/* reset this unavailable attribute before the next call */
+			this->attr[i] = this->orig_attr[i];
+		}
+		else if (this->attr[i].pValue == NULL &&
+				 this->attr[i].ulValueLen != 0)
 		{
 			this->attr[i].pValue = malloc(this->attr[i].ulValueLen);
 			this->freelist->insert_last(this->freelist, &this->attr[i]);
@@ -705,9 +732,10 @@ static bool get_attributes(object_enumerator_t *this, CK_OBJECT_HANDLE object)
 	/* get the data */
 	rv = this->lib->f->C_GetAttributeValue(this->session, object,
 										   this->attr, this->count);
-	if (rv != CKR_OK)
+	if (rv != CKR_OK &&
+		rv != CKR_ATTRIBUTE_SENSITIVE &&
+		rv != CKR_ATTRIBUTE_TYPE_INVALID)
 	{
-		free_attrs(this);
 		DBG1(DBG_CFG, "C_GetAttributeValue() error: %N", ck_rv_names, rv);
 		return FALSE;
 	}
@@ -774,6 +802,7 @@ METHOD(enumerator_t, object_destroy, void,
 	}
 	free_attrs(this);
 	this->freelist->destroy(this->freelist);
+	free(this->orig_attr);
 	free(this);
 }
 
@@ -804,6 +833,7 @@ METHOD(pkcs11_library_t, create_object_enumerator, enumerator_t*,
 		.count = acount,
 		.freelist = linked_list_create(),
 	);
+	init_attrs(enumerator);
 	return &enumerator->public;
 }
 
@@ -826,6 +856,7 @@ METHOD(pkcs11_library_t, create_object_attr_enumerator, enumerator_t*,
 		.object = object,
 		.freelist = linked_list_create(),
 	);
+	init_attrs(enumerator);
 	return &enumerator->public;
 }
 
@@ -1033,7 +1064,6 @@ static void check_features(private_pkcs11_library_t *this, CK_INFO *info)
 {
 	if (has_version(info, 2, 20))
 	{
-		this->features |= PKCS11_TRUSTED_CERTS;
 		this->features |= PKCS11_ALWAYS_AUTH_KEYS;
 	}
 }

src/libstrongswan/plugins/pkcs11/pkcs11_library.h

@@ -37,10 +37,8 @@ typedef struct pkcs11_library_t pkcs11_library_t;
  * Optional PKCS#11 features some libraries support, some not
  */
 enum pkcs11_feature_t {
-	/** CKA_TRUSTED attribute supported for certificate objects */
-	PKCS11_TRUSTED_CERTS = (1<<0),
 	/** CKA_ALWAYS_AUTHENTICATE attribute supported for private keys */
-	PKCS11_ALWAYS_AUTH_KEYS = (1<<1),
+	PKCS11_ALWAYS_AUTH_KEYS = (1<<0),
 };
 
 /**
@@ -73,6 +71,8 @@ struct pkcs11_library_t {
 	 * An optional attribute array is automatically filled in with the
 	 * objects associated attributes. If the value of an output attribute
 	 * is NULL, the value gets allocated/freed during enumeration.
+	 * For attributes that are unavailable, the length field will be set to
+	 * CK_UNAVAILABLE_INFORMATION.
 	 *
 	 * @param session	session to use
 	 * @param tmpl		search template
@@ -92,6 +92,8 @@ struct pkcs11_library_t {
 	 * The given attribute array is automatically filled in with the
 	 * associated attributes. If the value of an output attribute is NULL,
 	 * the required memory gets allocated/freed during enumeration.
+	 * For attributes that are unavailable, the length field will be set to
+	 * CK_UNAVAILABLE_INFORMATION.
 	 *
 	 * @param session	session to use
 	 * @param object	object handle

src/libstrongswan/plugins/pkcs11/pkcs11_manager.c

@@ -389,4 +389,3 @@ pkcs11_manager_t *pkcs11_manager_create(pkcs11_manager_token_event_t cb,
 
 	return &this->public;
 }
-

src/libstrongswan/plugins/pkcs11/pkcs11_private_key.c

@@ -627,13 +627,17 @@ static pkcs11_library_t* find_lib_and_keyid_by_skid(chunk_t keyid_chunk,
 											  attr, countof(attr));
 		while (certs->enumerate(certs, &object))
 		{
-			INIT(entry,
+			if (attr[0].ulValueLen != CK_UNAVAILABLE_INFORMATION &&
-				.value = chunk_clone(
+				attr[1].ulValueLen != CK_UNAVAILABLE_INFORMATION)
-							chunk_create(attr[0].pValue, attr[0].ulValueLen)),
+			{
-				.ckaid = chunk_clone(
+				INIT(entry,
-							chunk_create(attr[1].pValue, attr[1].ulValueLen)),
+					.value = chunk_clone(
-			);
+								chunk_create(attr[0].pValue, attr[0].ulValueLen)),
-			raw->insert_last(raw, entry);
+					.ckaid = chunk_clone(
+								chunk_create(attr[1].pValue, attr[1].ulValueLen)),
+				);
+				raw->insert_last(raw, entry);
+			}
 		}
 		certs->destroy(certs);
 
@@ -708,7 +712,8 @@ static bool find_key(private_pkcs11_private_key_t *this, chunk_t keyid)
 	}
 	enumerator = this->lib->create_object_enumerator(this->lib,
 							this->session, tmpl, countof(tmpl), attr, count);
-	if (enumerator->enumerate(enumerator, &object))
+	if (enumerator->enumerate(enumerator, &object) &&
+		attr[0].ulValueLen != CK_UNAVAILABLE_INFORMATION)
 	{
 		this->type = KEY_RSA;
 		switch (type)
@@ -717,7 +722,10 @@ static bool find_key(private_pkcs11_private_key_t *this, chunk_t keyid)
 				this->type = KEY_ECDSA;
 				/* fall-through */
 			case CKK_RSA:
-				this->reauth = reauth;
+				if (attr[1].ulValueLen != CK_UNAVAILABLE_INFORMATION)
+				{
+					this->reauth = reauth;
+				}
 				this->object = object;
 				found = TRUE;
 				break;
@@ -803,7 +811,8 @@ static public_key_t* find_pubkey_in_certs(private_pkcs11_private_key_t *this,
 
 	enumerator = this->lib->create_object_enumerator(this->lib, this->session,
 									tmpl, countof(tmpl), attr, countof(attr));
-	if (enumerator->enumerate(enumerator, &object))
+	if (enumerator->enumerate(enumerator, &object) &&
+		attr[0].ulValueLen != CK_UNAVAILABLE_INFORMATION)
 	{
 		data = chunk_clone(chunk_create(attr[0].pValue, attr[0].ulValueLen));
 	}

src/libstrongswan/plugins/pkcs11/pkcs11_public_key.c

@@ -888,7 +888,8 @@ static private_pkcs11_public_key_t *find_key_by_keyid(pkcs11_library_t *p11,
 
 	enumerator = p11->create_object_enumerator(p11, session, tmpl, count, attr,
 											   countof(attr));
-	if (enumerator->enumerate(enumerator, &object))
+	if (enumerator->enumerate(enumerator, &object) &&
+		attr[0].ulValueLen != CK_UNAVAILABLE_INFORMATION)
 	{
 		switch (type)
 		{