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ext4 crypto: add encryption policy and password salt support
Signed-off-by: Michael Halcrow <[email protected]> Signed-off-by: Theodore Ts'o <[email protected]> Signed-off-by: Ildar Muslukhov <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -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 <linux/random.h> | ||
| #include <linux/string.h> | ||
| #include <linux/types.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.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; | ||
|
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| 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; | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -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 | ||
|
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| #include <linux/fs.h> | ||
|
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| #define EXT4_KEY_DESCRIPTOR_SIZE 8 | ||
|
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| /* 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__)); | ||
|
|
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| #define EXT4_ENCRYPTION_CONTEXT_FORMAT_V1 1 | ||
| #define EXT4_KEY_DERIVATION_NONCE_SIZE 16 | ||
|
|
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| /** | ||
| * 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 */ |
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