1/* 2 * linux/fs/ext4/crypto_policy.c 3 * 4 * Copyright (C) 2015, Google, Inc. 5 * 6 * This contains encryption policy functions for ext4 7 * 8 * Written by Michael Halcrow, 2015. 9 */ 10 11#include <linux/random.h> 12#include <linux/string.h> 13#include <linux/types.h> 14 15#include "ext4.h" 16#include "xattr.h" 17 18static int ext4_inode_has_encryption_context(struct inode *inode) 19{ 20 int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION, 21 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, NULL, 0); 22 return (res > 0); 23} 24 25/* 26 * check whether the policy is consistent with the encryption context 27 * for the inode 28 */ 29static int ext4_is_encryption_context_consistent_with_policy( 30 struct inode *inode, const struct ext4_encryption_policy *policy) 31{ 32 struct ext4_encryption_context ctx; 33 int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION, 34 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx, 35 sizeof(ctx)); 36 if (res != sizeof(ctx)) 37 return 0; 38 return (memcmp(ctx.master_key_descriptor, policy->master_key_descriptor, 39 EXT4_KEY_DESCRIPTOR_SIZE) == 0 && 40 (ctx.flags == 41 policy->flags) && 42 (ctx.contents_encryption_mode == 43 policy->contents_encryption_mode) && 44 (ctx.filenames_encryption_mode == 45 policy->filenames_encryption_mode)); 46} 47 48static int ext4_create_encryption_context_from_policy( 49 struct inode *inode, const struct ext4_encryption_policy *policy) 50{ 51 struct ext4_encryption_context ctx; 52 int res = 0; 53 54 ctx.format = EXT4_ENCRYPTION_CONTEXT_FORMAT_V1; 55 memcpy(ctx.master_key_descriptor, policy->master_key_descriptor, 56 EXT4_KEY_DESCRIPTOR_SIZE); 57 if (!ext4_valid_contents_enc_mode(policy->contents_encryption_mode)) { 58 printk(KERN_WARNING 59 "%s: Invalid contents encryption mode %d\n", __func__, 60 policy->contents_encryption_mode); 61 return -EINVAL; 62 } 63 if (!ext4_valid_filenames_enc_mode(policy->filenames_encryption_mode)) { 64 printk(KERN_WARNING 65 "%s: Invalid filenames encryption mode %d\n", __func__, 66 policy->filenames_encryption_mode); 67 return -EINVAL; 68 } 69 if (policy->flags & ~EXT4_POLICY_FLAGS_VALID) 70 return -EINVAL; 71 ctx.contents_encryption_mode = policy->contents_encryption_mode; 72 ctx.filenames_encryption_mode = policy->filenames_encryption_mode; 73 ctx.flags = policy->flags; 74 BUILD_BUG_ON(sizeof(ctx.nonce) != EXT4_KEY_DERIVATION_NONCE_SIZE); 75 get_random_bytes(ctx.nonce, EXT4_KEY_DERIVATION_NONCE_SIZE); 76 77 res = ext4_xattr_set(inode, EXT4_XATTR_INDEX_ENCRYPTION, 78 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx, 79 sizeof(ctx), 0); 80 if (!res) 81 ext4_set_inode_flag(inode, EXT4_INODE_ENCRYPT); 82 return res; 83} 84 85int ext4_process_policy(const struct ext4_encryption_policy *policy, 86 struct inode *inode) 87{ 88 if (policy->version != 0) 89 return -EINVAL; 90 91 if (!ext4_inode_has_encryption_context(inode)) { 92 if (!ext4_empty_dir(inode)) 93 return -ENOTEMPTY; 94 return ext4_create_encryption_context_from_policy(inode, 95 policy); 96 } 97 98 if (ext4_is_encryption_context_consistent_with_policy(inode, policy)) 99 return 0; 100 101 printk(KERN_WARNING "%s: Policy inconsistent with encryption context\n", 102 __func__); 103 return -EINVAL; 104} 105 106int ext4_get_policy(struct inode *inode, struct ext4_encryption_policy *policy) 107{ 108 struct ext4_encryption_context ctx; 109 110 int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION, 111 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, 112 &ctx, sizeof(ctx)); 113 if (res != sizeof(ctx)) 114 return -ENOENT; 115 if (ctx.format != EXT4_ENCRYPTION_CONTEXT_FORMAT_V1) 116 return -EINVAL; 117 policy->version = 0; 118 policy->contents_encryption_mode = ctx.contents_encryption_mode; 119 policy->filenames_encryption_mode = ctx.filenames_encryption_mode; 120 policy->flags = ctx.flags; 121 memcpy(&policy->master_key_descriptor, ctx.master_key_descriptor, 122 EXT4_KEY_DESCRIPTOR_SIZE); 123 return 0; 124} 125 126int ext4_is_child_context_consistent_with_parent(struct inode *parent, 127 struct inode *child) 128{ 129 struct ext4_encryption_context parent_ctx, child_ctx; 130 int res; 131 132 if ((parent == NULL) || (child == NULL)) { 133 pr_err("parent %p child %p\n", parent, child); 134 BUG_ON(1); 135 } 136 /* no restrictions if the parent directory is not encrypted */ 137 if (!ext4_encrypted_inode(parent)) 138 return 1; 139 res = ext4_xattr_get(parent, EXT4_XATTR_INDEX_ENCRYPTION, 140 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, 141 &parent_ctx, sizeof(parent_ctx)); 142 if (res != sizeof(parent_ctx)) 143 return 0; 144 /* if the child directory is not encrypted, this is always a problem */ 145 if (!ext4_encrypted_inode(child)) 146 return 0; 147 res = ext4_xattr_get(child, EXT4_XATTR_INDEX_ENCRYPTION, 148 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, 149 &child_ctx, sizeof(child_ctx)); 150 if (res != sizeof(child_ctx)) 151 return 0; 152 return (memcmp(parent_ctx.master_key_descriptor, 153 child_ctx.master_key_descriptor, 154 EXT4_KEY_DESCRIPTOR_SIZE) == 0 && 155 (parent_ctx.contents_encryption_mode == 156 child_ctx.contents_encryption_mode) && 157 (parent_ctx.filenames_encryption_mode == 158 child_ctx.filenames_encryption_mode)); 159} 160 161/** 162 * ext4_inherit_context() - Sets a child context from its parent 163 * @parent: Parent inode from which the context is inherited. 164 * @child: Child inode that inherits the context from @parent. 165 * 166 * Return: Zero on success, non-zero otherwise 167 */ 168int ext4_inherit_context(struct inode *parent, struct inode *child) 169{ 170 struct ext4_encryption_context ctx; 171 int res = ext4_xattr_get(parent, EXT4_XATTR_INDEX_ENCRYPTION, 172 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, 173 &ctx, sizeof(ctx)); 174 175 if (res != sizeof(ctx)) { 176 if (DUMMY_ENCRYPTION_ENABLED(EXT4_SB(parent->i_sb))) { 177 ctx.format = EXT4_ENCRYPTION_CONTEXT_FORMAT_V1; 178 ctx.contents_encryption_mode = 179 EXT4_ENCRYPTION_MODE_AES_256_XTS; 180 ctx.filenames_encryption_mode = 181 EXT4_ENCRYPTION_MODE_AES_256_CTS; 182 ctx.flags = 0; 183 memset(ctx.master_key_descriptor, 0x42, 184 EXT4_KEY_DESCRIPTOR_SIZE); 185 res = 0; 186 } else { 187 goto out; 188 } 189 } 190 get_random_bytes(ctx.nonce, EXT4_KEY_DERIVATION_NONCE_SIZE); 191 res = ext4_xattr_set(child, EXT4_XATTR_INDEX_ENCRYPTION, 192 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx, 193 sizeof(ctx), 0); 194out: 195 if (!res) 196 ext4_set_inode_flag(child, EXT4_INODE_ENCRYPT); 197 return res; 198} 199