--- /dev/null
+/*
+ * linux/fs/ext4/crypto_key.c
+ *
+ * Copyright (C) 2015, Google, Inc.
+ *
+ * This contains encryption key functions for ext4
+ *
+ * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
+ */
+
+#include <keys/encrypted-type.h>
+#include <keys/user-type.h>
+#include <linux/random.h>
+#include <linux/scatterlist.h>
+#include <uapi/linux/keyctl.h>
+
+#include "ext4.h"
+#include "xattr.h"
+
+struct derive_crypt_result {
+ struct completion completion;
+ int rc;
+};
+
+static void derive_crypt_complete(struct crypto_async_request *req, int rc)
+{
+ struct derive_crypt_result *dcr = req->data;
+
+ if (rc == -EINPROGRESS)
+ return;
+
+ dcr->rc = rc;
+ complete(&dcr->completion);
+}
+
+/**
+ * ext4_derive_key_aes() - Derive a key using AES-128-ECB
+ * @deriving_key: Encryption key used for derivatio.
+ * @source_key: Source key to which to apply derivation.
+ * @derived_key: Derived key.
+ *
+ * Return: Zero on success; non-zero otherwise.
+ */
+static int ext4_derive_key_aes(char deriving_key[EXT4_AES_128_ECB_KEY_SIZE],
+ char source_key[EXT4_AES_256_XTS_KEY_SIZE],
+ char derived_key[EXT4_AES_256_XTS_KEY_SIZE])
+{
+ int res = 0;
+ struct ablkcipher_request *req = NULL;
+ struct derive_crypt_result dcr;
+ struct scatterlist src_sg, dst_sg;
+ struct crypto_ablkcipher *tfm = crypto_alloc_ablkcipher("ecb(aes)", 0,
+ 0);
+
+ if (IS_ERR(tfm)) {
+ res = PTR_ERR(tfm);
+ tfm = NULL;
+ goto out;
+ }
+ crypto_ablkcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
+ req = ablkcipher_request_alloc(tfm, GFP_NOFS);
+ if (!req) {
+ res = -ENOMEM;
+ goto out;
+ }
+ ablkcipher_request_set_callback(req,
+ CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
+ derive_crypt_complete, &dcr);
+ res = crypto_ablkcipher_setkey(tfm, deriving_key,
+ EXT4_AES_128_ECB_KEY_SIZE);
+ if (res < 0)
+ goto out;
+ sg_init_one(&src_sg, source_key, EXT4_AES_256_XTS_KEY_SIZE);
+ sg_init_one(&dst_sg, derived_key, EXT4_AES_256_XTS_KEY_SIZE);
+ ablkcipher_request_set_crypt(req, &src_sg, &dst_sg,
+ EXT4_AES_256_XTS_KEY_SIZE, NULL);
+ res = crypto_ablkcipher_encrypt(req);
+ if (res == -EINPROGRESS || res == -EBUSY) {
+ struct derive_crypt_result *dcr = req->base.data;
+
+ wait_for_completion(&dcr->completion);
+ res = dcr->rc;
+ }
+
+out:
+ if (req)
+ ablkcipher_request_free(req);
+ if (tfm)
+ crypto_free_ablkcipher(tfm);
+ return res;
+}
+
+/**
+ * ext4_generate_encryption_key() - generates an encryption key
+ * @inode: The inode to generate the encryption key for.
+ */
+int ext4_generate_encryption_key(struct inode *inode)
+{
+ struct ext4_inode_info *ei = EXT4_I(inode);
+ struct ext4_encryption_key *crypt_key = &ei->i_encryption_key;
+ char full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE +
+ (EXT4_KEY_DESCRIPTOR_SIZE * 2) + 1];
+ struct key *keyring_key = NULL;
+ struct ext4_encryption_key *master_key;
+ struct ext4_encryption_context ctx;
+ struct user_key_payload *ukp;
+ int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
+ EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
+ &ctx, sizeof(ctx));
+
+ if (res != sizeof(ctx)) {
+ if (res > 0)
+ res = -EINVAL;
+ goto out;
+ }
+ res = 0;
+
+ memcpy(full_key_descriptor, EXT4_KEY_DESC_PREFIX,
+ EXT4_KEY_DESC_PREFIX_SIZE);
+ ext4_to_hex(&full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE],
+ ctx.master_key_descriptor, EXT4_KEY_DESCRIPTOR_SIZE);
+ full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE +
+ (2 * EXT4_KEY_DESCRIPTOR_SIZE)] = '\0';
+ keyring_key = request_key(&key_type_logon, full_key_descriptor, NULL);
+ if (IS_ERR(keyring_key)) {
+ res = PTR_ERR(keyring_key);
+ keyring_key = NULL;
+ goto out;
+ }
+ BUG_ON(keyring_key->type != &key_type_logon);
+ ukp = ((struct user_key_payload *)keyring_key->payload.data);
+ if (ukp->datalen != sizeof(struct ext4_encryption_key)) {
+ res = -EINVAL;
+ goto out;
+ }
+ master_key = (struct ext4_encryption_key *)ukp->data;
+
+ if (S_ISREG(inode->i_mode))
+ crypt_key->mode = ctx.contents_encryption_mode;
+ else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
+ crypt_key->mode = ctx.filenames_encryption_mode;
+ else {
+ printk(KERN_ERR "ext4 crypto: Unsupported inode type.\n");
+ BUG();
+ }
+ crypt_key->size = ext4_encryption_key_size(crypt_key->mode);
+ BUG_ON(!crypt_key->size);
+ BUILD_BUG_ON(EXT4_AES_128_ECB_KEY_SIZE !=
+ EXT4_KEY_DERIVATION_NONCE_SIZE);
+ BUG_ON(master_key->size != EXT4_AES_256_XTS_KEY_SIZE);
+ BUG_ON(crypt_key->size < EXT4_AES_256_CBC_KEY_SIZE);
+ res = ext4_derive_key_aes(ctx.nonce, master_key->raw, crypt_key->raw);
+out:
+ if (keyring_key)
+ key_put(keyring_key);
+ if (res < 0)
+ crypt_key->mode = EXT4_ENCRYPTION_MODE_INVALID;
+ return res;
+}
+
+int ext4_has_encryption_key(struct inode *inode)
+{
+ struct ext4_inode_info *ei = EXT4_I(inode);
+ struct ext4_encryption_key *crypt_key = &ei->i_encryption_key;
+
+ return (crypt_key->mode != EXT4_ENCRYPTION_MODE_INVALID);
+}