264 lines
7.1 KiB
C
264 lines
7.1 KiB
C
/*
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* Encryption policy functions for per-file encryption support.
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*
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* Copyright (C) 2015, Google, Inc.
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* Copyright (C) 2015, Motorola Mobility.
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*
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* Written by Michael Halcrow, 2015.
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* Modified by Jaegeuk Kim, 2015.
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*/
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#include <linux/random.h>
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#include <linux/string.h>
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#include <linux/mount.h>
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#include "fscrypt_private.h"
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static int inode_has_encryption_context(struct inode *inode)
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{
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if (!inode->i_sb->s_cop->get_context)
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return 0;
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return (inode->i_sb->s_cop->get_context(inode, NULL, 0L) > 0);
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}
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/*
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* check whether the policy is consistent with the encryption context
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* for the inode
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*/
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static int is_encryption_context_consistent_with_policy(struct inode *inode,
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const struct fscrypt_policy *policy)
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{
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struct fscrypt_context ctx;
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int res;
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if (!inode->i_sb->s_cop->get_context)
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return 0;
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res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
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if (res != sizeof(ctx))
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return 0;
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return (memcmp(ctx.master_key_descriptor, policy->master_key_descriptor,
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FS_KEY_DESCRIPTOR_SIZE) == 0 &&
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(ctx.flags == policy->flags) &&
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(ctx.contents_encryption_mode ==
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policy->contents_encryption_mode) &&
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(ctx.filenames_encryption_mode ==
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policy->filenames_encryption_mode));
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}
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static int create_encryption_context_from_policy(struct inode *inode,
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const struct fscrypt_policy *policy)
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{
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struct fscrypt_context ctx;
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int res;
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if (!inode->i_sb->s_cop->set_context)
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return -EOPNOTSUPP;
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if (inode->i_sb->s_cop->prepare_context) {
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res = inode->i_sb->s_cop->prepare_context(inode);
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if (res)
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return res;
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}
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ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
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memcpy(ctx.master_key_descriptor, policy->master_key_descriptor,
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FS_KEY_DESCRIPTOR_SIZE);
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if (!fscrypt_valid_contents_enc_mode(
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policy->contents_encryption_mode)) {
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printk(KERN_WARNING
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"%s: Invalid contents encryption mode %d\n", __func__,
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policy->contents_encryption_mode);
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return -EINVAL;
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}
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if (!fscrypt_valid_filenames_enc_mode(
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policy->filenames_encryption_mode)) {
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printk(KERN_WARNING
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"%s: Invalid filenames encryption mode %d\n", __func__,
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policy->filenames_encryption_mode);
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return -EINVAL;
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}
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if (policy->flags & ~FS_POLICY_FLAGS_VALID)
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return -EINVAL;
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ctx.contents_encryption_mode = policy->contents_encryption_mode;
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ctx.filenames_encryption_mode = policy->filenames_encryption_mode;
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ctx.flags = policy->flags;
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BUILD_BUG_ON(sizeof(ctx.nonce) != FS_KEY_DERIVATION_NONCE_SIZE);
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get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
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return inode->i_sb->s_cop->set_context(inode, &ctx, sizeof(ctx), NULL);
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}
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int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg)
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{
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struct fscrypt_policy policy;
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struct inode *inode = file_inode(filp);
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int ret;
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if (copy_from_user(&policy, arg, sizeof(policy)))
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return -EFAULT;
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if (!inode_owner_or_capable(inode))
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return -EACCES;
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if (policy.version != 0)
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return -EINVAL;
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ret = mnt_want_write_file(filp);
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if (ret)
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return ret;
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inode_lock(inode);
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if (!inode_has_encryption_context(inode)) {
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if (!S_ISDIR(inode->i_mode))
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ret = -EINVAL;
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else if (!inode->i_sb->s_cop->empty_dir)
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ret = -EOPNOTSUPP;
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else if (!inode->i_sb->s_cop->empty_dir(inode))
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ret = -ENOTEMPTY;
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else
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ret = create_encryption_context_from_policy(inode,
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&policy);
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} else if (!is_encryption_context_consistent_with_policy(inode,
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&policy)) {
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printk(KERN_WARNING
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"%s: Policy inconsistent with encryption context\n",
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__func__);
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ret = -EINVAL;
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}
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inode_unlock(inode);
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mnt_drop_write_file(filp);
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return ret;
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}
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EXPORT_SYMBOL(fscrypt_ioctl_set_policy);
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int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg)
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{
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struct inode *inode = file_inode(filp);
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struct fscrypt_context ctx;
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struct fscrypt_policy policy;
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int res;
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if (!inode->i_sb->s_cop->get_context ||
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!inode->i_sb->s_cop->is_encrypted(inode))
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return -ENODATA;
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res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
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if (res != sizeof(ctx))
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return -ENODATA;
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if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1)
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return -EINVAL;
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policy.version = 0;
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policy.contents_encryption_mode = ctx.contents_encryption_mode;
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policy.filenames_encryption_mode = ctx.filenames_encryption_mode;
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policy.flags = ctx.flags;
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memcpy(policy.master_key_descriptor, ctx.master_key_descriptor,
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FS_KEY_DESCRIPTOR_SIZE);
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if (copy_to_user(arg, &policy, sizeof(policy)))
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return -EFAULT;
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return 0;
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}
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EXPORT_SYMBOL(fscrypt_ioctl_get_policy);
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int fscrypt_has_permitted_context(struct inode *parent, struct inode *child)
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{
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struct fscrypt_info *parent_ci, *child_ci;
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int res;
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if ((parent == NULL) || (child == NULL)) {
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printk(KERN_ERR "parent %p child %p\n", parent, child);
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BUG_ON(1);
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}
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/* No restrictions on file types which are never encrypted */
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if (!S_ISREG(child->i_mode) && !S_ISDIR(child->i_mode) &&
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!S_ISLNK(child->i_mode))
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return 1;
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/* no restrictions if the parent directory is not encrypted */
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if (!parent->i_sb->s_cop->is_encrypted(parent))
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return 1;
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/* if the child directory is not encrypted, this is always a problem */
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if (!parent->i_sb->s_cop->is_encrypted(child))
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return 0;
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res = fscrypt_get_encryption_info(parent);
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if (res)
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return 0;
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res = fscrypt_get_encryption_info(child);
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if (res)
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return 0;
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parent_ci = parent->i_crypt_info;
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child_ci = child->i_crypt_info;
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if (!parent_ci && !child_ci)
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return 1;
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if (!parent_ci || !child_ci)
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return 0;
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return (memcmp(parent_ci->ci_master_key,
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child_ci->ci_master_key,
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FS_KEY_DESCRIPTOR_SIZE) == 0 &&
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(parent_ci->ci_data_mode == child_ci->ci_data_mode) &&
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(parent_ci->ci_filename_mode == child_ci->ci_filename_mode) &&
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(parent_ci->ci_flags == child_ci->ci_flags));
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}
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EXPORT_SYMBOL(fscrypt_has_permitted_context);
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/**
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* fscrypt_inherit_context() - Sets a child context from its parent
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* @parent: Parent inode from which the context is inherited.
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* @child: Child inode that inherits the context from @parent.
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* @fs_data: private data given by FS.
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* @preload: preload child i_crypt_info
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*
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* Return: Zero on success, non-zero otherwise
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*/
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int fscrypt_inherit_context(struct inode *parent, struct inode *child,
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void *fs_data, bool preload)
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{
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struct fscrypt_context ctx;
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struct fscrypt_info *ci;
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int res;
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if (!parent->i_sb->s_cop->set_context)
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return -EOPNOTSUPP;
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res = fscrypt_get_encryption_info(parent);
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if (res < 0)
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return res;
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ci = parent->i_crypt_info;
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if (ci == NULL)
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return -ENOKEY;
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ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
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if (fscrypt_dummy_context_enabled(parent)) {
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ctx.contents_encryption_mode = FS_ENCRYPTION_MODE_AES_256_XTS;
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ctx.filenames_encryption_mode = FS_ENCRYPTION_MODE_AES_256_CTS;
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ctx.flags = 0;
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memset(ctx.master_key_descriptor, 0x42, FS_KEY_DESCRIPTOR_SIZE);
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res = 0;
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} else {
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ctx.contents_encryption_mode = ci->ci_data_mode;
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ctx.filenames_encryption_mode = ci->ci_filename_mode;
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ctx.flags = ci->ci_flags;
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memcpy(ctx.master_key_descriptor, ci->ci_master_key,
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FS_KEY_DESCRIPTOR_SIZE);
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}
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get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
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res = parent->i_sb->s_cop->set_context(child, &ctx,
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sizeof(ctx), fs_data);
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if (res)
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return res;
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return preload ? fscrypt_get_encryption_info(child): 0;
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}
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EXPORT_SYMBOL(fscrypt_inherit_context);
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