309 lines
9.2 KiB
C
309 lines
9.2 KiB
C
/*
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* linux/fs/ext4/crypto_policy.c
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*
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* Copyright (C) 2015, Google, Inc.
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*
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* This contains encryption policy functions for ext4
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*
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* Written by Michael Halcrow, 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/types.h>
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#include "ext4_jbd2.h"
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#include "ext4.h"
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#include "xattr.h"
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#ifdef CONFIG_EXT4CRYPT_SDP
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#include "sdp/fscrypto_sdp_dek_private.h"
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#endif
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static int ext4_inode_has_encryption_context(struct inode *inode)
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{
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int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
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EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, NULL, 0);
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return (res > 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 ext4_is_encryption_context_consistent_with_policy(
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struct inode *inode, const struct ext4_encryption_policy *policy)
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{
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struct ext4_encryption_context ctx;
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int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
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EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
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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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EXT4_KEY_DESCRIPTOR_SIZE) == 0 &&
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#ifdef CONFIG_EXT4_PRIVATE_ENCRYPTION
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((ctx.flags & EXT4_POLICY_FLAGS_PAD_MASK) == (policy->flags & EXT4_POLICY_FLAGS_PAD_MASK)) &&
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#else
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(ctx.flags ==
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policy->flags) &&
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#endif
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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 ext4_create_encryption_context_from_policy(
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struct inode *inode, const struct ext4_encryption_policy *policy)
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{
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struct ext4_encryption_context ctx;
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handle_t *handle;
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int res, res2;
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res = ext4_convert_inline_data(inode);
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if (res)
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return res;
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ctx.format = EXT4_ENCRYPTION_CONTEXT_FORMAT_V1;
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memcpy(ctx.master_key_descriptor, policy->master_key_descriptor,
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EXT4_KEY_DESCRIPTOR_SIZE);
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if (!ext4_valid_contents_enc_mode(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 (!ext4_valid_filenames_enc_mode(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 & ~EXT4_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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#if defined(CONFIG_EXT4CRYPT_SDP) || defined(CONFIG_DDAR)
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ctx.knox_flags = 0;
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#endif
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BUILD_BUG_ON(sizeof(ctx.nonce) != EXT4_KEY_DERIVATION_NONCE_SIZE);
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get_random_bytes(ctx.nonce, EXT4_KEY_DERIVATION_NONCE_SIZE);
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handle = ext4_journal_start(inode, EXT4_HT_MISC,
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ext4_jbd2_credits_xattr(inode));
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if (IS_ERR(handle))
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return PTR_ERR(handle);
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res = ext4_xattr_set(inode, EXT4_XATTR_INDEX_ENCRYPTION,
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EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
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sizeof(ctx), 0);
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if (!res) {
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ext4_set_inode_flag(inode, EXT4_INODE_ENCRYPT);
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res = ext4_mark_inode_dirty(handle, inode);
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if (res)
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EXT4_ERROR_INODE(inode, "Failed to mark inode dirty");
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}
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res2 = ext4_journal_stop(handle);
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if (!res)
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res = res2;
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return res;
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}
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int ext4_process_policy(const struct ext4_encryption_policy *policy,
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struct inode *inode)
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{
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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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if (!ext4_inode_has_encryption_context(inode)) {
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if (!S_ISDIR(inode->i_mode))
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return -EINVAL;
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if (!ext4_empty_dir(inode))
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return -ENOTEMPTY;
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return ext4_create_encryption_context_from_policy(inode,
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policy);
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}
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if (ext4_is_encryption_context_consistent_with_policy(inode, policy))
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return 0;
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printk(KERN_WARNING "%s: Policy inconsistent with encryption context\n",
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__func__);
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return -EINVAL;
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}
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int ext4_get_policy(struct inode *inode, struct ext4_encryption_policy *policy)
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{
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struct ext4_encryption_context ctx;
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int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
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EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
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&ctx, sizeof(ctx));
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if (res != sizeof(ctx))
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return -ENOENT;
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if (ctx.format != EXT4_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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#ifdef CONFIG_EXT4_PRIVATE_ENCRYPTION
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policy->flags = ctx.flags & EXT4_POLICY_FLAGS_PAD_MASK;
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#else
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policy->flags = ctx.flags;
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#endif
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memcpy(&policy->master_key_descriptor, ctx.master_key_descriptor,
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EXT4_KEY_DESCRIPTOR_SIZE);
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return 0;
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}
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int ext4_is_child_context_consistent_with_parent(struct inode *parent,
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struct inode *child)
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{
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const struct ext4_crypt_info *parent_ci, *child_ci;
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struct ext4_encryption_context parent_ctx, child_ctx;
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int res;
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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 unencrypted */
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if (!ext4_encrypted_inode(parent))
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return 1;
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/* Encrypted directories must not contain unencrypted files */
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if (!ext4_encrypted_inode(child))
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return 0;
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/*
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* Both parent and child are encrypted, so verify they use the same
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* encryption policy. Compare the fscrypt_info structs if the keys are
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* available, otherwise retrieve and compare the fscrypt_contexts.
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*
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* Note that the fscrypt_context retrieval will be required frequently
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* when accessing an encrypted directory tree without the key.
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* Performance-wise this is not a big deal because we already don't
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* really optimize for file access without the key (to the extent that
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* such access is even possible), given that any attempted access
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* already causes a fscrypt_context retrieval and keyring search.
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*
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* In any case, if an unexpected error occurs, fall back to "forbidden".
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*/
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res = ext4_get_encryption_info(parent);
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if (res)
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return 0;
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res = ext4_get_encryption_info(child);
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if (res)
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return 0;
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parent_ci = EXT4_I(parent)->i_crypt_info;
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child_ci = EXT4_I(child)->i_crypt_info;
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if (parent_ci && child_ci) {
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return memcmp(parent_ci->ci_master_key, child_ci->ci_master_key,
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EXT4_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 ==
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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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res = ext4_xattr_get(parent, EXT4_XATTR_INDEX_ENCRYPTION,
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EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
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&parent_ctx, sizeof(parent_ctx));
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if (res != sizeof(parent_ctx))
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return 0;
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res = ext4_xattr_get(child, EXT4_XATTR_INDEX_ENCRYPTION,
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EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
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&child_ctx, sizeof(child_ctx));
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if (res != sizeof(child_ctx))
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return 0;
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return memcmp(parent_ctx.master_key_descriptor,
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child_ctx.master_key_descriptor,
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EXT4_KEY_DESCRIPTOR_SIZE) == 0 &&
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(parent_ctx.contents_encryption_mode ==
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child_ctx.contents_encryption_mode) &&
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(parent_ctx.filenames_encryption_mode ==
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child_ctx.filenames_encryption_mode) &&
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#ifdef CONFIG_EXT4_PRIVATE_ENCRYPTION
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((parent_ctx.flags & EXT4_POLICY_FLAGS_PAD_MASK) == (child_ctx.flags & EXT4_POLICY_FLAGS_PAD_MASK));
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#else
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(parent_ctx.flags == child_ctx.flags);
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#endif
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}
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/**
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* ext4_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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*
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* Return: Zero on success, non-zero otherwise
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*/
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int ext4_inherit_context(struct inode *parent, struct inode *child)
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{
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struct ext4_encryption_context ctx;
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struct ext4_crypt_info *ci;
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int res;
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res = ext4_get_encryption_info(parent);
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if (res < 0)
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return res;
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ci = EXT4_I(parent)->i_crypt_info;
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if (ci == NULL)
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return -ENOKEY;
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ctx.format = EXT4_ENCRYPTION_CONTEXT_FORMAT_V1;
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if (DUMMY_ENCRYPTION_ENABLED(EXT4_SB(parent->i_sb))) {
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ctx.contents_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS;
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ctx.filenames_encryption_mode =
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EXT4_ENCRYPTION_MODE_AES_256_CTS;
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ctx.flags = 0;
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memset(ctx.master_key_descriptor, 0x42,
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EXT4_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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#ifdef CONFIG_EXT4_PRIVATE_ENCRYPTION
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if (!S_ISDIR(child->i_mode))
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ctx.flags |= EXT4_POLICY_FLAGS_PRIVATE_ALGO;
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#endif
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memcpy(ctx.master_key_descriptor, ci->ci_master_key,
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EXT4_KEY_DESCRIPTOR_SIZE);
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}
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get_random_bytes(ctx.nonce, EXT4_KEY_DERIVATION_NONCE_SIZE);
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#if defined(CONFIG_DDAR) || defined(CONFIG_EXT4CRYPT_SDP)
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ctx.knox_flags = 0;
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#endif
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#ifdef CONFIG_EXT4CRYPT_SDP
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#ifdef CONFIG_SDP_ENHANCED
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res = fscrypt_sdp_inherit_context(parent, child, &ctx);
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#else
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res = fscrypt_sdp_test_and_inherit_context(parent, child, &ctx);
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#endif
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if (res) {
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printk_once(KERN_WARNING
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"%s: Failed to set sensitive ongoing flag (err:%d)\n", __func__, res);
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return res;
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}
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#endif
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res = ext4_xattr_set(child, EXT4_XATTR_INDEX_ENCRYPTION,
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EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
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sizeof(ctx), 0);
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if (!res) {
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ext4_set_inode_flag(child, EXT4_INODE_ENCRYPT);
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ext4_clear_inode_state(child, EXT4_STATE_MAY_INLINE_DATA);
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res = ext4_get_encryption_info(child);
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}
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return res;
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}
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