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b30ab0e034
On encrypt, we will re-assign the buffer_heads to point to a bounce page rather than the control_page (which is the original page to write that contains the plaintext). The block I/O occurs against the bounce page. On write completion, we re-assign the buffer_heads to the original plaintext page. On decrypt, we will attach a read completion callback to the bio struct. This read completion will decrypt the read contents in-place prior to setting the page up-to-date. The current encryption mode, AES-256-XTS, lacks cryptographic integrity. AES-256-GCM is in-plan, but we will need to devise a mechanism for handling the integrity data. Signed-off-by: Michael Halcrow <mhalcrow@google.com> Signed-off-by: Ildar Muslukhov <ildarm@google.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
105 lines
2.8 KiB
C
105 lines
2.8 KiB
C
/*
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* linux/fs/ext4/ext4_crypto.h
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*
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* Copyright (C) 2015, Google, Inc.
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*
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* This contains encryption header content for ext4
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*
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* Written by Michael Halcrow, 2015.
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*/
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#ifndef _EXT4_CRYPTO_H
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#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 */
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struct ext4_encryption_policy {
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char version;
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char contents_encryption_mode;
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char filenames_encryption_mode;
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char master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE];
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} __attribute__((__packed__));
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#define EXT4_ENCRYPTION_CONTEXT_FORMAT_V1 1
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#define EXT4_KEY_DERIVATION_NONCE_SIZE 16
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/**
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* Encryption context for inode
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*
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* Protector format:
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* 1 byte: Protector format (1 = this version)
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* 1 byte: File contents encryption mode
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* 1 byte: File names encryption mode
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* 1 byte: Reserved
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* 8 bytes: Master Key descriptor
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* 16 bytes: Encryption Key derivation nonce
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*/
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struct ext4_encryption_context {
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char format;
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char contents_encryption_mode;
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char filenames_encryption_mode;
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char reserved;
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char master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE];
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char nonce[EXT4_KEY_DERIVATION_NONCE_SIZE];
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} __attribute__((__packed__));
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/* Encryption parameters */
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#define EXT4_XTS_TWEAK_SIZE 16
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#define EXT4_AES_128_ECB_KEY_SIZE 16
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#define EXT4_AES_256_GCM_KEY_SIZE 32
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#define EXT4_AES_256_CBC_KEY_SIZE 32
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#define EXT4_AES_256_CTS_KEY_SIZE 32
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#define EXT4_AES_256_XTS_KEY_SIZE 64
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#define EXT4_MAX_KEY_SIZE 64
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struct ext4_encryption_key {
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uint32_t mode;
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char raw[EXT4_MAX_KEY_SIZE];
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uint32_t size;
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};
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#define EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL 0x00000001
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#define EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL 0x00000002
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struct ext4_crypto_ctx {
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struct crypto_tfm *tfm; /* Crypto API context */
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struct page *bounce_page; /* Ciphertext page on write path */
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struct page *control_page; /* Original page on write path */
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struct bio *bio; /* The bio for this context */
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struct work_struct work; /* Work queue for read complete path */
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struct list_head free_list; /* Free list */
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int flags; /* Flags */
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int mode; /* Encryption mode for tfm */
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};
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struct ext4_completion_result {
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struct completion completion;
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int res;
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};
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#define DECLARE_EXT4_COMPLETION_RESULT(ecr) \
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struct ext4_completion_result ecr = { \
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COMPLETION_INITIALIZER((ecr).completion), 0 }
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static inline int ext4_encryption_key_size(int mode)
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{
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switch (mode) {
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case EXT4_ENCRYPTION_MODE_AES_256_XTS:
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return EXT4_AES_256_XTS_KEY_SIZE;
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case EXT4_ENCRYPTION_MODE_AES_256_GCM:
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return EXT4_AES_256_GCM_KEY_SIZE;
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case EXT4_ENCRYPTION_MODE_AES_256_CBC:
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return EXT4_AES_256_CBC_KEY_SIZE;
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case EXT4_ENCRYPTION_MODE_AES_256_CTS:
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return EXT4_AES_256_CTS_KEY_SIZE;
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default:
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BUG();
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}
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return 0;
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}
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#endif /* _EXT4_CRYPTO_H */
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