ext4 crypto: add encryption policy and password salt support
Signed-off-by: Michael Halcrow <mhalcrow@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Ildar Muslukhov <muslukhovi@gmail.com>
diff --git a/fs/ext4/crypto_policy.c b/fs/ext4/crypto_policy.c
new file mode 100644
index 0000000..532b69c
--- /dev/null
+++ b/fs/ext4/crypto_policy.c
@@ -0,0 +1,167 @@
+/*
+ * linux/fs/ext4/crypto_policy.c
+ *
+ * Copyright (C) 2015, Google, Inc.
+ *
+ * This contains encryption policy functions for ext4
+ *
+ * Written by Michael Halcrow, 2015.
+ */
+
+#include <linux/random.h>
+#include <linux/string.h>
+#include <linux/types.h>
+
+#include "ext4.h"
+#include "xattr.h"
+
+static int ext4_inode_has_encryption_context(struct inode *inode)
+{
+ int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
+ EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, NULL, 0);
+ return (res > 0);
+}
+
+/*
+ * check whether the policy is consistent with the encryption context
+ * for the inode
+ */
+static int ext4_is_encryption_context_consistent_with_policy(
+ struct inode *inode, const struct ext4_encryption_policy *policy)
+{
+ struct ext4_encryption_context ctx;
+ int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
+ EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
+ sizeof(ctx));
+ if (res != sizeof(ctx))
+ return 0;
+ return (memcmp(ctx.master_key_descriptor, policy->master_key_descriptor,
+ EXT4_KEY_DESCRIPTOR_SIZE) == 0 &&
+ (ctx.contents_encryption_mode ==
+ policy->contents_encryption_mode) &&
+ (ctx.filenames_encryption_mode ==
+ policy->filenames_encryption_mode));
+}
+
+static int ext4_create_encryption_context_from_policy(
+ struct inode *inode, const struct ext4_encryption_policy *policy)
+{
+ struct ext4_encryption_context ctx;
+ int res = 0;
+
+ ctx.format = EXT4_ENCRYPTION_CONTEXT_FORMAT_V1;
+ memcpy(ctx.master_key_descriptor, policy->master_key_descriptor,
+ EXT4_KEY_DESCRIPTOR_SIZE);
+ ctx.contents_encryption_mode = policy->contents_encryption_mode;
+ ctx.filenames_encryption_mode = policy->filenames_encryption_mode;
+ BUILD_BUG_ON(sizeof(ctx.nonce) != EXT4_KEY_DERIVATION_NONCE_SIZE);
+ get_random_bytes(ctx.nonce, EXT4_KEY_DERIVATION_NONCE_SIZE);
+
+ res = ext4_xattr_set(inode, EXT4_XATTR_INDEX_ENCRYPTION,
+ EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
+ sizeof(ctx), 0);
+ if (!res)
+ ext4_set_inode_flag(inode, EXT4_INODE_ENCRYPT);
+ return res;
+}
+
+int ext4_process_policy(const struct ext4_encryption_policy *policy,
+ struct inode *inode)
+{
+ if (policy->version != 0)
+ return -EINVAL;
+
+ if (!ext4_inode_has_encryption_context(inode)) {
+ if (!ext4_empty_dir(inode))
+ return -ENOTEMPTY;
+ return ext4_create_encryption_context_from_policy(inode,
+ policy);
+ }
+
+ if (ext4_is_encryption_context_consistent_with_policy(inode, policy))
+ return 0;
+
+ printk(KERN_WARNING "%s: Policy inconsistent with encryption context\n",
+ __func__);
+ return -EINVAL;
+}
+
+int ext4_get_policy(struct inode *inode, struct ext4_encryption_policy *policy)
+{
+ struct ext4_encryption_context ctx;
+
+ int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
+ EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
+ &ctx, sizeof(ctx));
+ if (res != sizeof(ctx))
+ return -ENOENT;
+ if (ctx.format != EXT4_ENCRYPTION_CONTEXT_FORMAT_V1)
+ return -EINVAL;
+ policy->version = 0;
+ policy->contents_encryption_mode = ctx.contents_encryption_mode;
+ policy->filenames_encryption_mode = ctx.filenames_encryption_mode;
+ memcpy(&policy->master_key_descriptor, ctx.master_key_descriptor,
+ EXT4_KEY_DESCRIPTOR_SIZE);
+ return 0;
+}
+
+int ext4_is_child_context_consistent_with_parent(struct inode *parent,
+ struct inode *child)
+{
+ struct ext4_encryption_context parent_ctx, child_ctx;
+ int res;
+
+ if ((parent == NULL) || (child == NULL)) {
+ pr_err("parent %p child %p\n", parent, child);
+ BUG_ON(1);
+ }
+ /* no restrictions if the parent directory is not encrypted */
+ if (!ext4_encrypted_inode(parent))
+ return 1;
+ res = ext4_xattr_get(parent, EXT4_XATTR_INDEX_ENCRYPTION,
+ EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
+ &parent_ctx, sizeof(parent_ctx));
+ if (res != sizeof(parent_ctx))
+ return 0;
+ /* if the child directory is not encrypted, this is always a problem */
+ if (!ext4_encrypted_inode(child))
+ return 0;
+ res = ext4_xattr_get(child, EXT4_XATTR_INDEX_ENCRYPTION,
+ EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
+ &child_ctx, sizeof(child_ctx));
+ if (res != sizeof(child_ctx))
+ return 0;
+ return (memcmp(parent_ctx.master_key_descriptor,
+ child_ctx.master_key_descriptor,
+ EXT4_KEY_DESCRIPTOR_SIZE) == 0 &&
+ (parent_ctx.contents_encryption_mode ==
+ child_ctx.contents_encryption_mode) &&
+ (parent_ctx.filenames_encryption_mode ==
+ child_ctx.filenames_encryption_mode));
+}
+
+/**
+ * ext4_inherit_context() - Sets a child context from its parent
+ * @parent: Parent inode from which the context is inherited.
+ * @child: Child inode that inherits the context from @parent.
+ *
+ * Return: Zero on success, non-zero otherwise
+ */
+int ext4_inherit_context(struct inode *parent, struct inode *child)
+{
+ struct ext4_encryption_context ctx;
+ int res = ext4_xattr_get(parent, EXT4_XATTR_INDEX_ENCRYPTION,
+ EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
+ &ctx, sizeof(ctx));
+
+ if (res != sizeof(ctx))
+ return -ENOENT;
+
+ get_random_bytes(ctx.nonce, EXT4_KEY_DERIVATION_NONCE_SIZE);
+ res = ext4_xattr_set(child, EXT4_XATTR_INDEX_ENCRYPTION,
+ EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
+ sizeof(ctx), 0);
+ if (!res)
+ ext4_set_inode_flag(child, EXT4_INODE_ENCRYPT);
+ return res;
+}