1 files changed, 74 insertions, 48 deletions

diff --git a/fs/crypto/keyinfo.c b/fs/crypto/keyinfo.c
index f63bfd6dffd6..f248ee9974fa 100644
--- a/fs/crypto/keyinfo.c
+++ b/fs/crypto/keyinfo.c
@@ -27,7 +27,7 @@ static struct crypto_shash *essiv_hash_tfm;
  *
  * Return: Zero on success; non-zero otherwise.
  */
-static int derive_key_aes(u8 deriving_key[FS_KEY_DERIVATION_NONCE_SIZE],
+static int derive_key_aes(const u8 deriving_key[FS_KEY_DERIVATION_NONCE_SIZE],
 				const struct fscrypt_key *source_key,
 				u8 derived_raw_key[FS_MAX_KEY_SIZE])
 {
@@ -67,52 +67,88 @@ out:
 	return res;
 }
 
-static int validate_user_key(struct fscrypt_info *crypt_info,
-			struct fscrypt_context *ctx, u8 *raw_key,
-			const char *prefix, int min_keysize)
+/*
+ * Search the current task's subscribed keyrings for a "logon" key with
+ * description prefix:descriptor, and if found acquire a read lock on it and
+ * return a pointer to its validated payload in *payload_ret.
+ */
+static struct key *
+find_and_lock_process_key(const char *prefix,
+			  const u8 descriptor[FS_KEY_DESCRIPTOR_SIZE],
+			  unsigned int min_keysize,
+			  const struct fscrypt_key **payload_ret)
 {
 	char *description;
-	struct key *keyring_key;
-	struct fscrypt_key *master_key;
+	struct key *key;
 	const struct user_key_payload *ukp;
-	int res;
+	const struct fscrypt_key *payload;
 
 	description = kasprintf(GFP_NOFS, "%s%*phN", prefix,
-				FS_KEY_DESCRIPTOR_SIZE,
-				ctx->master_key_descriptor);
+				FS_KEY_DESCRIPTOR_SIZE, descriptor);
 	if (!description)
-		return -ENOMEM;
+		return ERR_PTR(-ENOMEM);
 
-	keyring_key = request_key(&key_type_logon, description, NULL);
+	key = request_key(&key_type_logon, description, NULL);
 	kfree(description);
-	if (IS_ERR(keyring_key))
-		return PTR_ERR(keyring_key);
-	down_read(&keyring_key->sem);
-
-	ukp = user_key_payload_locked(keyring_key);
-	if (!ukp) {
-		/* key was revoked before we acquired its semaphore */
-		res = -EKEYREVOKED;
-		goto out;
+	if (IS_ERR(key))
+		return key;
+
+	down_read(&key->sem);
+	ukp = user_key_payload_locked(key);
+
+	if (!ukp) /* was the key revoked before we acquired its semaphore? */
+		goto invalid;
+
+	payload = (const struct fscrypt_key *)ukp->data;
+
+	if (ukp->datalen != sizeof(struct fscrypt_key) ||
+	    payload->size < 1 || payload->size > FS_MAX_KEY_SIZE) {
+		fscrypt_warn(NULL,
+			     "key with description '%s' has invalid payload",
+			     key->description);
+		goto invalid;
 	}
-	if (ukp->datalen != sizeof(struct fscrypt_key)) {
-		res = -EINVAL;
-		goto out;
+
+	if (payload->size < min_keysize ||
+	    payload->size % AES_BLOCK_SIZE != 0) {
+		fscrypt_warn(NULL,
+			     "key with description '%s' is too short or is misaligned (got %u bytes, need %u+ bytes)",
+			     key->description, payload->size, min_keysize);
+		goto invalid;
 	}
-	master_key = (struct fscrypt_key *)ukp->data;
 
-	if (master_key->size < min_keysize || master_key->size > FS_MAX_KEY_SIZE
-	    || master_key->size % AES_BLOCK_SIZE != 0) {
-		fscrypt_warn(NULL, "key size incorrect: %u",
-			     master_key->size);
-		res = -ENOKEY;
-		goto out;
+	*payload_ret = payload;
+	return key;
+
+invalid:
+	up_read(&key->sem);
+	key_put(key);
+	return ERR_PTR(-ENOKEY);
+}
+
+/* Find the master key, then derive the inode's actual encryption key */
+static int find_and_derive_key(const struct inode *inode,
+			       const struct fscrypt_context *ctx,
+			       u8 *derived_key, unsigned int derived_keysize)
+{
+	struct key *key;
+	const struct fscrypt_key *payload;
+	int err;
+
+	key = find_and_lock_process_key(FS_KEY_DESC_PREFIX,
+					ctx->master_key_descriptor,
+					derived_keysize, &payload);
+	if (key == ERR_PTR(-ENOKEY) && inode->i_sb->s_cop->key_prefix) {
+		key = find_and_lock_process_key(inode->i_sb->s_cop->key_prefix,
+						ctx->master_key_descriptor,
+						derived_keysize, &payload);
 	}
-	res = derive_key_aes(ctx->nonce, master_key, raw_key);
-out:
-	up_read(&keyring_key->sem);
-	key_put(keyring_key);
-	return res;
+	if (IS_ERR(key))
+		return PTR_ERR(key);
+	err = derive_key_aes(ctx->nonce, payload, derived_key);
+	up_read(&key->sem);
+	key_put(key);
+	return err;
 }
 
 static const struct {
@@ -293,20 +329,10 @@ int fscrypt_get_encryption_info(struct inode *inode)
 	if (!raw_key)
 		goto out;
 
-	res = validate_user_key(crypt_info, &ctx, raw_key, FS_KEY_DESC_PREFIX,
-				keysize);
-	if (res && inode->i_sb->s_cop->key_prefix) {
-		int res2 = validate_user_key(crypt_info, &ctx, raw_key,
-					     inode->i_sb->s_cop->key_prefix,
-					     keysize);
-		if (res2) {
-			if (res2 == -ENOKEY)
-				res = -ENOKEY;
-			goto out;
-		}
-	} else if (res) {
+	res = find_and_derive_key(inode, &ctx, raw_key, keysize);
+	if (res)
 		goto out;
-	}
+
 	ctfm = crypto_alloc_skcipher(cipher_str, 0, 0);
 	if (IS_ERR(ctfm)) {
 		res = PTR_ERR(ctfm);