diff options
Diffstat (limited to 'fs/ext4/crypto_policy.c')
| -rw-r--r-- | fs/ext4/crypto_policy.c | 268 |
1 files changed, 268 insertions, 0 deletions
diff --git a/fs/ext4/crypto_policy.c b/fs/ext4/crypto_policy.c new file mode 100644 index 000000000000..e4f4fc4e56ab --- /dev/null +++ b/fs/ext4/crypto_policy.c @@ -0,0 +1,268 @@ +/* + * 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_jbd2.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.flags == + policy->flags) && + (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; + handle_t *handle; + int res, res2; + + res = ext4_convert_inline_data(inode); + if (res) + return res; + + ctx.format = EXT4_ENCRYPTION_CONTEXT_FORMAT_V1; + memcpy(ctx.master_key_descriptor, policy->master_key_descriptor, + EXT4_KEY_DESCRIPTOR_SIZE); + if (!ext4_valid_contents_enc_mode(policy->contents_encryption_mode)) { + printk(KERN_WARNING + "%s: Invalid contents encryption mode %d\n", __func__, + policy->contents_encryption_mode); + return -EINVAL; + } + if (!ext4_valid_filenames_enc_mode(policy->filenames_encryption_mode)) { + printk(KERN_WARNING + "%s: Invalid filenames encryption mode %d\n", __func__, + policy->filenames_encryption_mode); + return -EINVAL; + } + if (policy->flags & ~EXT4_POLICY_FLAGS_VALID) + return -EINVAL; + ctx.contents_encryption_mode = policy->contents_encryption_mode; + ctx.filenames_encryption_mode = policy->filenames_encryption_mode; + ctx.flags = policy->flags; + BUILD_BUG_ON(sizeof(ctx.nonce) != EXT4_KEY_DERIVATION_NONCE_SIZE); + get_random_bytes(ctx.nonce, EXT4_KEY_DERIVATION_NONCE_SIZE); + + handle = ext4_journal_start(inode, EXT4_HT_MISC, + ext4_jbd2_credits_xattr(inode)); + if (IS_ERR(handle)) + return PTR_ERR(handle); + 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); + res = ext4_mark_inode_dirty(handle, inode); + if (res) + EXT4_ERROR_INODE(inode, "Failed to mark inode dirty"); + } + res2 = ext4_journal_stop(handle); + if (!res) + res = res2; + return res; +} + +int ext4_process_policy(const struct ext4_encryption_policy *policy, + struct inode *inode) +{ + if (!inode_owner_or_capable(inode)) + return -EACCES; + + if (policy->version != 0) + return -EINVAL; + + if (!ext4_inode_has_encryption_context(inode)) { + if (!S_ISDIR(inode->i_mode)) + return -EINVAL; + 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; + policy->flags = ctx.flags; + 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) +{ + const struct ext4_crypt_info *parent_ci, *child_ci; + struct ext4_encryption_context parent_ctx, child_ctx; + int res; + + /* No restrictions on file types which are never encrypted */ + if (!S_ISREG(child->i_mode) && !S_ISDIR(child->i_mode) && + !S_ISLNK(child->i_mode)) + return 1; + + /* No restrictions if the parent directory is unencrypted */ + if (!ext4_encrypted_inode(parent)) + return 1; + + /* Encrypted directories must not contain unencrypted files */ + if (!ext4_encrypted_inode(child)) + return 0; + + /* + * Both parent and child are encrypted, so verify they use the same + * encryption policy. Compare the fscrypt_info structs if the keys are + * available, otherwise retrieve and compare the fscrypt_contexts. + * + * Note that the fscrypt_context retrieval will be required frequently + * when accessing an encrypted directory tree without the key. + * Performance-wise this is not a big deal because we already don't + * really optimize for file access without the key (to the extent that + * such access is even possible), given that any attempted access + * already causes a fscrypt_context retrieval and keyring search. + * + * In any case, if an unexpected error occurs, fall back to "forbidden". + */ + + res = ext4_get_encryption_info(parent); + if (res) + return 0; + res = ext4_get_encryption_info(child); + if (res) + return 0; + parent_ci = EXT4_I(parent)->i_crypt_info; + child_ci = EXT4_I(child)->i_crypt_info; + if (parent_ci && child_ci) { + return memcmp(parent_ci->ci_master_key, child_ci->ci_master_key, + EXT4_KEY_DESCRIPTOR_SIZE) == 0 && + (parent_ci->ci_data_mode == child_ci->ci_data_mode) && + (parent_ci->ci_filename_mode == + child_ci->ci_filename_mode) && + (parent_ci->ci_flags == child_ci->ci_flags); + } + + 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; + + 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) && + (parent_ctx.flags == child_ctx.flags); +} + +/** + * 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; + struct ext4_crypt_info *ci; + int res; + + res = ext4_get_encryption_info(parent); + if (res < 0) + return res; + ci = EXT4_I(parent)->i_crypt_info; + if (ci == NULL) + return -ENOKEY; + + ctx.format = EXT4_ENCRYPTION_CONTEXT_FORMAT_V1; + if (DUMMY_ENCRYPTION_ENABLED(EXT4_SB(parent->i_sb))) { + ctx.contents_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS; + ctx.filenames_encryption_mode = + EXT4_ENCRYPTION_MODE_AES_256_CTS; + ctx.flags = 0; + memset(ctx.master_key_descriptor, 0x42, + EXT4_KEY_DESCRIPTOR_SIZE); + res = 0; + } else { + ctx.contents_encryption_mode = ci->ci_data_mode; + ctx.filenames_encryption_mode = ci->ci_filename_mode; + ctx.flags = ci->ci_flags; + memcpy(ctx.master_key_descriptor, ci->ci_master_key, + EXT4_KEY_DESCRIPTOR_SIZE); + } + 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); + ext4_clear_inode_state(child, EXT4_STATE_MAY_INLINE_DATA); + res = ext4_get_encryption_info(child); + } + return res; +} |