1 files changed, 94 insertions, 38 deletions

diff --git a/fs/crypto/keyring.c b/fs/crypto/keyring.c
index 787e9c8938ba..ace369f13068 100644
--- a/fs/crypto/keyring.c
+++ b/fs/crypto/keyring.c
@@ -149,11 +149,11 @@ static int fscrypt_user_key_instantiate(struct key *key,
 					struct key_preparsed_payload *prep)
 {
 	/*
-	 * We just charge FSCRYPT_MAX_KEY_SIZE bytes to the user's key quota for
-	 * each key, regardless of the exact key size.  The amount of memory
+	 * We just charge FSCRYPT_MAX_RAW_KEY_SIZE bytes to the user's key quota
+	 * for each key, regardless of the exact key size.  The amount of memory
 	 * actually used is greater than the size of the raw key anyway.
 	 */
-	return key_payload_reserve(key, FSCRYPT_MAX_KEY_SIZE);
+	return key_payload_reserve(key, FSCRYPT_MAX_RAW_KEY_SIZE);
 }
 
 static void fscrypt_user_key_describe(const struct key *key, struct seq_file *m)
@@ -558,20 +558,45 @@ static int add_master_key(struct super_block *sb,
 	int err;
 
 	if (key_spec->type == FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER) {
-		err = fscrypt_init_hkdf(&secret->hkdf, secret->raw,
-					secret->size);
-		if (err)
-			return err;
+		u8 sw_secret[BLK_CRYPTO_SW_SECRET_SIZE];
+		u8 *kdf_key = secret->bytes;
+		unsigned int kdf_key_size = secret->size;
+		u8 keyid_kdf_ctx = HKDF_CONTEXT_KEY_IDENTIFIER_FOR_RAW_KEY;
 
 		/*
-		 * Now that the HKDF context is initialized, the raw key is no
-		 * longer needed.
+		 * For raw keys, the fscrypt master key is used directly as the
+		 * fscrypt KDF key.  For hardware-wrapped keys, we have to pass
+		 * the master key to the hardware to derive the KDF key, which
+		 * is then only used to derive non-file-contents subkeys.
+		 */
+		if (secret->is_hw_wrapped) {
+			err = fscrypt_derive_sw_secret(sb, secret->bytes,
+						       secret->size, sw_secret);
+			if (err)
+				return err;
+			kdf_key = sw_secret;
+			kdf_key_size = sizeof(sw_secret);
+			/*
+			 * To avoid weird behavior if someone manages to
+			 * determine sw_secret and add it as a raw key, ensure
+			 * that hardware-wrapped keys and raw keys will have
+			 * different key identifiers by deriving their key
+			 * identifiers using different KDF contexts.
+			 */
+			keyid_kdf_ctx =
+				HKDF_CONTEXT_KEY_IDENTIFIER_FOR_HW_WRAPPED_KEY;
+		}
+		err = fscrypt_init_hkdf(&secret->hkdf, kdf_key, kdf_key_size);
+		/*
+		 * Now that the KDF context is initialized, the raw KDF key is
+		 * no longer needed.
 		 */
-		memzero_explicit(secret->raw, secret->size);
+		memzero_explicit(kdf_key, kdf_key_size);
+		if (err)
+			return err;
 
 		/* Calculate the key identifier */
-		err = fscrypt_hkdf_expand(&secret->hkdf,
-					  HKDF_CONTEXT_KEY_IDENTIFIER, NULL, 0,
+		err = fscrypt_hkdf_expand(&secret->hkdf, keyid_kdf_ctx, NULL, 0,
 					  key_spec->u.identifier,
 					  FSCRYPT_KEY_IDENTIFIER_SIZE);
 		if (err)
@@ -580,19 +605,36 @@ static int add_master_key(struct super_block *sb,
 	return do_add_master_key(sb, secret, key_spec);
 }
 
+/*
+ * Validate the size of an fscrypt master key being added.  Note that this is
+ * just an initial check, as we don't know which ciphers will be used yet.
+ * There is a stricter size check later when the key is actually used by a file.
+ */
+static inline bool fscrypt_valid_key_size(size_t size, u32 add_key_flags)
+{
+	u32 max_size = (add_key_flags & FSCRYPT_ADD_KEY_FLAG_HW_WRAPPED) ?
+		       FSCRYPT_MAX_HW_WRAPPED_KEY_SIZE :
+		       FSCRYPT_MAX_RAW_KEY_SIZE;
+
+	return size >= FSCRYPT_MIN_KEY_SIZE && size <= max_size;
+}
+
 static int fscrypt_provisioning_key_preparse(struct key_preparsed_payload *prep)
 {
 	const struct fscrypt_provisioning_key_payload *payload = prep->data;
 
-	if (prep->datalen < sizeof(*payload) + FSCRYPT_MIN_KEY_SIZE ||
-	    prep->datalen > sizeof(*payload) + FSCRYPT_MAX_KEY_SIZE)
+	if (prep->datalen < sizeof(*payload))
+		return -EINVAL;
+
+	if (!fscrypt_valid_key_size(prep->datalen - sizeof(*payload),
+				    payload->flags))
 		return -EINVAL;
 
 	if (payload->type != FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR &&
 	    payload->type != FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER)
 		return -EINVAL;
 
-	if (payload->__reserved)
+	if (payload->flags & ~FSCRYPT_ADD_KEY_FLAG_HW_WRAPPED)
 		return -EINVAL;
 
 	prep->payload.data[0] = kmemdup(payload, prep->datalen, GFP_KERNEL);
@@ -636,21 +678,21 @@ static struct key_type key_type_fscrypt_provisioning = {
 };
 
 /*
- * Retrieve the raw key from the Linux keyring key specified by 'key_id', and
- * store it into 'secret'.
+ * Retrieve the key from the Linux keyring key specified by 'key_id', and store
+ * it into 'secret'.
  *
- * The key must be of type "fscrypt-provisioning" and must have the field
- * fscrypt_provisioning_key_payload::type set to 'type', indicating that it's
- * only usable with fscrypt with the particular KDF version identified by
- * 'type'.  We don't use the "logon" key type because there's no way to
- * completely restrict the use of such keys; they can be used by any kernel API
- * that accepts "logon" keys and doesn't require a specific service prefix.
+ * The key must be of type "fscrypt-provisioning" and must have the 'type' and
+ * 'flags' field of the payload set to the given values, indicating that the key
+ * is intended for use for the specified purpose.  We don't use the "logon" key
+ * type because there's no way to completely restrict the use of such keys; they
+ * can be used by any kernel API that accepts "logon" keys and doesn't require a
+ * specific service prefix.
  *
  * The ability to specify the key via Linux keyring key is intended for cases
  * where userspace needs to re-add keys after the filesystem is unmounted and
- * re-mounted.  Most users should just provide the raw key directly instead.
+ * re-mounted.  Most users should just provide the key directly instead.
  */
-static int get_keyring_key(u32 key_id, u32 type,
+static int get_keyring_key(u32 key_id, u32 type, u32 flags,
 			   struct fscrypt_master_key_secret *secret)
 {
 	key_ref_t ref;
@@ -667,12 +709,16 @@ static int get_keyring_key(u32 key_id, u32 type,
 		goto bad_key;
 	payload = key->payload.data[0];
 
-	/* Don't allow fscrypt v1 keys to be used as v2 keys and vice versa. */
-	if (payload->type != type)
+	/*
+	 * Don't allow fscrypt v1 keys to be used as v2 keys and vice versa.
+	 * Similarly, don't allow hardware-wrapped keys to be used as
+	 * non-hardware-wrapped keys and vice versa.
+	 */
+	if (payload->type != type || payload->flags != flags)
 		goto bad_key;
 
 	secret->size = key->datalen - sizeof(*payload);
-	memcpy(secret->raw, payload->raw, secret->size);
+	memcpy(secret->bytes, payload->raw, secret->size);
 	err = 0;
 	goto out_put;
 
@@ -734,19 +780,28 @@ int fscrypt_ioctl_add_key(struct file *filp, void __user *_uarg)
 		return -EACCES;
 
 	memset(&secret, 0, sizeof(secret));
+
+	if (arg.flags) {
+		if (arg.flags & ~FSCRYPT_ADD_KEY_FLAG_HW_WRAPPED)
+			return -EINVAL;
+		if (arg.key_spec.type != FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER)
+			return -EINVAL;
+		secret.is_hw_wrapped = true;
+	}
+
 	if (arg.key_id) {
 		if (arg.raw_size != 0)
 			return -EINVAL;
-		err = get_keyring_key(arg.key_id, arg.key_spec.type, &secret);
+		err = get_keyring_key(arg.key_id, arg.key_spec.type, arg.flags,
+				      &secret);
 		if (err)
 			goto out_wipe_secret;
 	} else {
-		if (arg.raw_size < FSCRYPT_MIN_KEY_SIZE ||
-		    arg.raw_size > FSCRYPT_MAX_KEY_SIZE)
+		if (!fscrypt_valid_key_size(arg.raw_size, arg.flags))
 			return -EINVAL;
 		secret.size = arg.raw_size;
 		err = -EFAULT;
-		if (copy_from_user(secret.raw, uarg->raw, secret.size))
+		if (copy_from_user(secret.bytes, uarg->raw, secret.size))
 			goto out_wipe_secret;
 	}
 
@@ -770,13 +825,13 @@ EXPORT_SYMBOL_GPL(fscrypt_ioctl_add_key);
 static void
 fscrypt_get_test_dummy_secret(struct fscrypt_master_key_secret *secret)
 {
-	static u8 test_key[FSCRYPT_MAX_KEY_SIZE];
+	static u8 test_key[FSCRYPT_MAX_RAW_KEY_SIZE];
 
-	get_random_once(test_key, FSCRYPT_MAX_KEY_SIZE);
+	get_random_once(test_key, sizeof(test_key));
 
 	memset(secret, 0, sizeof(*secret));
-	secret->size = FSCRYPT_MAX_KEY_SIZE;
-	memcpy(secret->raw, test_key, FSCRYPT_MAX_KEY_SIZE);
+	secret->size = sizeof(test_key);
+	memcpy(secret->bytes, test_key, sizeof(test_key));
 }
 
 int fscrypt_get_test_dummy_key_identifier(
@@ -787,10 +842,11 @@ int fscrypt_get_test_dummy_key_identifier(
 
 	fscrypt_get_test_dummy_secret(&secret);
 
-	err = fscrypt_init_hkdf(&secret.hkdf, secret.raw, secret.size);
+	err = fscrypt_init_hkdf(&secret.hkdf, secret.bytes, secret.size);
 	if (err)
 		goto out;
-	err = fscrypt_hkdf_expand(&secret.hkdf, HKDF_CONTEXT_KEY_IDENTIFIER,
+	err = fscrypt_hkdf_expand(&secret.hkdf,
+				  HKDF_CONTEXT_KEY_IDENTIFIER_FOR_RAW_KEY,
 				  NULL, 0, key_identifier,
 				  FSCRYPT_KEY_IDENTIFIER_SIZE);
 out: