From 9bd8212f981ea6375911fe055382ad7529be5b28 Mon Sep 17 00:00:00 2001 From: Michael Halcrow Date: Sat, 11 Apr 2015 07:48:01 -0400 Subject: [PATCH] ext4 crypto: add encryption policy and password salt support Signed-off-by: Michael Halcrow Signed-off-by: Theodore Ts'o Signed-off-by: Ildar Muslukhov --- fs/ext4/Makefile | 1 + fs/ext4/crypto_policy.c | 167 ++++++++++++++++++++++++++++++++++++++++ fs/ext4/ext4.h | 15 ++++ fs/ext4/ext4_crypto.h | 49 ++++++++++++ fs/ext4/ioctl.c | 85 ++++++++++++++++++++ 5 files changed, 317 insertions(+) create mode 100644 fs/ext4/crypto_policy.c create mode 100644 fs/ext4/ext4_crypto.h diff --git a/fs/ext4/Makefile b/fs/ext4/Makefile index cd6f50fce278..3886ee45f556 100644 --- a/fs/ext4/Makefile +++ b/fs/ext4/Makefile @@ -12,3 +12,4 @@ ext4-y := balloc.o bitmap.o dir.o file.o fsync.o ialloc.o inode.o page-io.o \ ext4-$(CONFIG_EXT4_FS_POSIX_ACL) += acl.o ext4-$(CONFIG_EXT4_FS_SECURITY) += xattr_security.o +ext4-$(CONFIG_EXT4_FS_ENCRYPTION) += crypto_policy.o diff --git a/fs/ext4/crypto_policy.c b/fs/ext4/crypto_policy.c new file mode 100644 index 000000000000..532b69c0afab --- /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 +#include +#include + +#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; +} diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 180111de2302..ab873aa9955e 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -589,6 +589,8 @@ enum { #define EXT4_ENCRYPTION_MODE_AES_256_CBC 3 #define EXT4_ENCRYPTION_MODE_AES_256_CTS 4 +#include "ext4_crypto.h" + /* * ioctl commands */ @@ -610,6 +612,9 @@ enum { #define EXT4_IOC_RESIZE_FS _IOW('f', 16, __u64) #define EXT4_IOC_SWAP_BOOT _IO('f', 17) #define EXT4_IOC_PRECACHE_EXTENTS _IO('f', 18) +#define EXT4_IOC_SET_ENCRYPTION_POLICY _IOR('f', 19, struct ext4_encryption_policy) +#define EXT4_IOC_GET_ENCRYPTION_PWSALT _IOW('f', 20, __u8[16]) +#define EXT4_IOC_GET_ENCRYPTION_POLICY _IOW('f', 21, struct ext4_encryption_policy) #if defined(__KERNEL__) && defined(CONFIG_COMPAT) /* @@ -2011,6 +2016,16 @@ extern unsigned ext4_free_clusters_after_init(struct super_block *sb, struct ext4_group_desc *gdp); ext4_fsblk_t ext4_inode_to_goal_block(struct inode *); +/* crypto_policy.c */ +int ext4_is_child_context_consistent_with_parent(struct inode *parent, + struct inode *child); +int ext4_inherit_context(struct inode *parent, struct inode *child); +void ext4_to_hex(char *dst, char *src, size_t src_size); +int ext4_process_policy(const struct ext4_encryption_policy *policy, + struct inode *inode); +int ext4_get_policy(struct inode *inode, + struct ext4_encryption_policy *policy); + /* dir.c */ extern int __ext4_check_dir_entry(const char *, unsigned int, struct inode *, struct file *, diff --git a/fs/ext4/ext4_crypto.h b/fs/ext4/ext4_crypto.h new file mode 100644 index 000000000000..a69d2ba54bee --- /dev/null +++ b/fs/ext4/ext4_crypto.h @@ -0,0 +1,49 @@ +/* + * linux/fs/ext4/ext4_crypto.h + * + * Copyright (C) 2015, Google, Inc. + * + * This contains encryption header content for ext4 + * + * Written by Michael Halcrow, 2015. + */ + +#ifndef _EXT4_CRYPTO_H +#define _EXT4_CRYPTO_H + +#include + +#define EXT4_KEY_DESCRIPTOR_SIZE 8 + +/* Policy provided via an ioctl on the topmost directory */ +struct ext4_encryption_policy { + char version; + char contents_encryption_mode; + char filenames_encryption_mode; + char master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE]; +} __attribute__((__packed__)); + +#define EXT4_ENCRYPTION_CONTEXT_FORMAT_V1 1 +#define EXT4_KEY_DERIVATION_NONCE_SIZE 16 + +/** + * Encryption context for inode + * + * Protector format: + * 1 byte: Protector format (1 = this version) + * 1 byte: File contents encryption mode + * 1 byte: File names encryption mode + * 1 byte: Reserved + * 8 bytes: Master Key descriptor + * 16 bytes: Encryption Key derivation nonce + */ +struct ext4_encryption_context { + char format; + char contents_encryption_mode; + char filenames_encryption_mode; + char reserved; + char master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE]; + char nonce[EXT4_KEY_DERIVATION_NONCE_SIZE]; +} __attribute__((__packed__)); + +#endif /* _EXT4_CRYPTO_H */ diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c index f1aa32c2277c..2cb9e178d1c5 100644 --- a/fs/ext4/ioctl.c +++ b/fs/ext4/ioctl.c @@ -13,6 +13,7 @@ #include #include #include +#include #include #include "ext4_jbd2.h" #include "ext4.h" @@ -195,6 +196,16 @@ journal_err_out: return err; } +static int uuid_is_zero(__u8 u[16]) +{ + int i; + + for (i = 0; i < 16; i++) + if (u[i]) + return 0; + return 1; +} + long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) { struct inode *inode = file_inode(filp); @@ -614,7 +625,78 @@ resizefs_out: } case EXT4_IOC_PRECACHE_EXTENTS: return ext4_ext_precache(inode); + case EXT4_IOC_SET_ENCRYPTION_POLICY: { +#ifdef CONFIG_EXT4_FS_ENCRYPTION + struct ext4_encryption_policy policy; + int err = 0; + + if (copy_from_user(&policy, + (struct ext4_encryption_policy __user *)arg, + sizeof(policy))) { + err = -EFAULT; + goto encryption_policy_out; + } + err = ext4_process_policy(&policy, inode); +encryption_policy_out: + return err; +#else + return -EOPNOTSUPP; +#endif + } + case EXT4_IOC_GET_ENCRYPTION_PWSALT: { + int err, err2; + struct ext4_sb_info *sbi = EXT4_SB(sb); + handle_t *handle; + + if (!ext4_sb_has_crypto(sb)) + return -EOPNOTSUPP; + if (uuid_is_zero(sbi->s_es->s_encrypt_pw_salt)) { + err = mnt_want_write_file(filp); + if (err) + return err; + handle = ext4_journal_start_sb(sb, EXT4_HT_MISC, 1); + if (IS_ERR(handle)) { + err = PTR_ERR(handle); + goto pwsalt_err_exit; + } + err = ext4_journal_get_write_access(handle, sbi->s_sbh); + if (err) + goto pwsalt_err_journal; + generate_random_uuid(sbi->s_es->s_encrypt_pw_salt); + err = ext4_handle_dirty_metadata(handle, NULL, + sbi->s_sbh); + pwsalt_err_journal: + err2 = ext4_journal_stop(handle); + if (err2 && !err) + err = err2; + pwsalt_err_exit: + mnt_drop_write_file(filp); + if (err) + return err; + } + if (copy_to_user((void *) arg, sbi->s_es->s_encrypt_pw_salt, + 16)) + return -EFAULT; + return 0; + } + case EXT4_IOC_GET_ENCRYPTION_POLICY: { +#ifdef CONFIG_EXT4_FS_ENCRYPTION + struct ext4_encryption_policy policy; + int err = 0; + + if (!ext4_encrypted_inode(inode)) + return -ENOENT; + err = ext4_get_policy(inode, &policy); + if (err) + return err; + if (copy_to_user((void *)arg, &policy, sizeof(policy))) + return -EFAULT; + return 0; +#else + return -EOPNOTSUPP; +#endif + } default: return -ENOTTY; } @@ -679,6 +761,9 @@ long ext4_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg) case FITRIM: case EXT4_IOC_RESIZE_FS: case EXT4_IOC_PRECACHE_EXTENTS: + case EXT4_IOC_SET_ENCRYPTION_POLICY: + case EXT4_IOC_GET_ENCRYPTION_PWSALT: + case EXT4_IOC_GET_ENCRYPTION_POLICY: break; default: return -ENOIOCTLCMD; -- 2.20.1