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[common] Refactor Protected Files slightly #1841

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[common] Refactor Protected Files slightly #1841

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c17f4ce
[common] Refactor Protected Files slightly
dimakuv Apr 11, 2024
6c008a3
fixup! [common] Refactor Protected Files slightly
dimakuv Apr 24, 2024
a14eaa0
fixup! [common] Refactor Protected Files slightly
dimakuv Apr 25, 2024
0c5d260
fixup! [common] Refactor Protected Files slightly
dimakuv Apr 25, 2024
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744 changes: 343 additions & 401 deletions common/src/protected_files/protected_files.c
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54 changes: 21 additions & 33 deletions common/src/protected_files/protected_files.h
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Original file line number Diff line number Diff line change
Expand Up @@ -12,24 +12,24 @@
#include <stddef.h>
#include <stdint.h>

/*! Size of the AES-GCM encryption key */
#define PF_KEY_SIZE 16
#define PF_NODE_SIZE 4096U

/*! Size of IV for AES-GCM */
#define PF_IV_SIZE 12

/*! Size of MAC fields */
#define PF_MAC_SIZE 16
/*! Size of tag fields */
#define PF_TAG_SIZE 16

/*! Size of the AES-GCM encryption key */
#define PF_KEY_SIZE 16

/*! Size of the salt used in KDF (Key Derivation Function) */
#define PF_SALT_SIZE 32

typedef uint8_t pf_iv_t[PF_IV_SIZE];
typedef uint8_t pf_mac_t[PF_MAC_SIZE];
typedef uint8_t pf_tag_t[PF_TAG_SIZE];
typedef uint8_t pf_key_t[PF_KEY_SIZE];
typedef uint8_t pf_keyid_t[32]; /* key derivation material */

extern pf_key_t g_pf_mrenclave_key;
extern pf_key_t g_pf_mrsigner_key;
extern pf_key_t g_pf_wrap_key;
extern bool g_pf_wrap_key_set;
typedef uint8_t pf_salt_t[PF_SALT_SIZE];

typedef enum _pf_status_t {
PF_STATUS_SUCCESS = 0,
Expand All @@ -41,7 +41,7 @@ typedef enum _pf_status_t {
PF_STATUS_INVALID_VERSION = -6,
PF_STATUS_INVALID_HEADER = -7,
PF_STATUS_INVALID_PATH = -8,
PF_STATUS_MAC_MISMATCH = -9,
PF_STATUS_TAG_MISMATCH = -9,
PF_STATUS_NOT_IMPLEMENTED = -10,
PF_STATUS_CALLBACK_FAILED = -11,
PF_STATUS_PATH_TOO_LONG = -12,
Expand All @@ -55,8 +55,6 @@ typedef enum _pf_status_t {
#define PF_SUCCESS(status) ((status) == PF_STATUS_SUCCESS)
#define PF_FAILURE(status) ((status) != PF_STATUS_SUCCESS)

#define PF_NODE_SIZE 4096U

/*! PF open modes */
typedef enum _pf_file_mode_t {
PF_FILE_MODE_READ = 1,
Expand All @@ -66,6 +64,9 @@ typedef enum _pf_file_mode_t {
/*! Opaque file handle type, interpreted by callbacks as necessary */
typedef void* pf_handle_t;

/*! Context representing an open protected file */
typedef struct pf_context pf_context_t;

/*!
* \brief File read callback.
*
Expand Down Expand Up @@ -123,12 +124,12 @@ typedef void (*pf_debug_f)(const char* msg);
* \param key AES-GCM key.
* \param input Plaintext data.
* \param input_size Size of \p input in bytes.
* \param[out] mac MAC computed for \p input.
* \param[out] tag Authentication tag computed for \p input.
*
* \returns PF status.
*/
typedef pf_status_t (*pf_aes_cmac_f)(const pf_key_t* key, const void* input, size_t input_size,
pf_mac_t* mac);
pf_tag_t* tag);

/*!
* \brief AES-GCM encrypt callback.
Expand All @@ -140,13 +141,13 @@ typedef pf_status_t (*pf_aes_cmac_f)(const pf_key_t* key, const void* input, siz
* \param input Plaintext data.
* \param input_size Size of \p input in bytes.
* \param[out] output Buffer for encrypted data (size: \p input_size).
* \param[out] mac MAC computed for \p input and \p aad.
* \param[out] tag Authentication tag computed for \p input and \p aad.
*
* \returns PF status.
*/
typedef pf_status_t (*pf_aes_gcm_encrypt_f)(const pf_key_t* key, const pf_iv_t* iv, const void* aad,
size_t aad_size, const void* input, size_t input_size,
void* output, pf_mac_t* mac);
void* output, pf_tag_t* tag);

/*!
* \brief AES-GCM decrypt callback.
Expand All @@ -158,13 +159,13 @@ typedef pf_status_t (*pf_aes_gcm_encrypt_f)(const pf_key_t* key, const pf_iv_t*
* \param input Encrypted data.
* \param input_size Size of \p input in bytes.
* \param[out] output Buffer for decrypted data (size: \p input_size).
* \param mac Expected MAC.
* \param tag Expected authentication tag.
*
* \returns PF status.
*/
typedef pf_status_t (*pf_aes_gcm_decrypt_f)(const pf_key_t* key, const pf_iv_t* iv, const void* aad,
size_t aad_size, const void* input, size_t input_size,
void* output, const pf_mac_t* mac);
void* output, const pf_tag_t* tag);

/*!
* \brief Cryptographic random number generator callback.
Expand Down Expand Up @@ -197,9 +198,6 @@ void pf_set_callbacks(pf_read_f read_f, pf_write_f write_f, pf_fsync_f fsync_f,
pf_aes_gcm_decrypt_f aes_gcm_decrypt_f, pf_random_f random_f,
pf_debug_f debug_f);

/*! Context representing an open protected file */
typedef struct pf_context pf_context_t;

/* Public API */

/*!
Expand Down Expand Up @@ -296,16 +294,6 @@ pf_status_t pf_set_size(pf_context_t* pf, uint64_t size);
*/
pf_status_t pf_rename(pf_context_t* pf, const char* new_path);

/*!
* \brief Get underlying handle of a PF.
*
* \param pf PF context.
* \param[out] handle Handle to the backing file.
*
* \returns PF status.
*/
pf_status_t pf_get_handle(pf_context_t* pf, pf_handle_t* handle);

/*!
* \brief Flush any pending data of a protected file to disk.
*
Expand Down
130 changes: 58 additions & 72 deletions common/src/protected_files/protected_files_format.h
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,8 @@

#pragma once

#pragma pack(push, 1)

#ifdef USE_STDLIB
#include <assert.h>
#else
Expand All @@ -14,7 +16,6 @@

#include <limits.h>

#include "list.h"
#include "protected_files.h"

#define PF_FILE_ID 0x46505f5346415247 /* GRAFS_PF */
Expand All @@ -23,117 +24,102 @@

#define METADATA_KEY_NAME "SGX-PROTECTED-FS-METADATA-KEY"
#define MAX_LABEL_SIZE 64

static_assert(sizeof(METADATA_KEY_NAME) <= MAX_LABEL_SIZE, "label too long");

#pragma pack(push, 1)

typedef struct _metadata_plain {
uint64_t file_id;
uint8_t major_version;
uint8_t minor_version;
pf_keyid_t metadata_key_id;
pf_mac_t metadata_gmac; /* GCM mac */
} metadata_plain_t;

#define PATH_MAX_SIZE (260 + 512)

// these are all defined as relative to node size, so we can decrease node size in tests
// and have deeper tree
#define MD_USER_DATA_SIZE (PF_NODE_SIZE * 3 / 4) // 3072
#define MD_USER_DATA_SIZE (PF_NODE_SIZE * 3 / 4)
static_assert(MD_USER_DATA_SIZE == 3072, "bad struct size");

typedef struct _metadata_encrypted {
char path[PATH_MAX_SIZE];
uint64_t size;
pf_key_t mht_key;
pf_mac_t mht_gmac;
uint8_t data[MD_USER_DATA_SIZE];
} metadata_encrypted_t;

typedef uint8_t metadata_encrypted_blob_t[sizeof(metadata_encrypted_t)];

#define METADATA_NODE_SIZE PF_NODE_SIZE

typedef uint8_t metadata_padding_t[METADATA_NODE_SIZE -
(sizeof(metadata_plain_t) + sizeof(metadata_encrypted_blob_t))];

typedef struct _metadata_node {
metadata_plain_t plain_part;
metadata_encrypted_blob_t encrypted_part;
metadata_padding_t padding;
} metadata_node_t;
#define MAX_PAGES_IN_CACHE 48

static_assert(sizeof(metadata_node_t) == PF_NODE_SIZE, "sizeof(metadata_node_t)");
enum {
FILE_MHT_NODE_TYPE = 1,
FILE_DATA_NODE_TYPE = 2,
};

typedef struct _data_node_crypto {
typedef struct _gcm_crypto_data {
pf_key_t key;
pf_mac_t gmac;
pf_tag_t tag;
} gcm_crypto_data_t;

// for PF_NODE_SIZE == 4096, we have 96 attached data nodes and 32 mht child nodes
// for PF_NODE_SIZE == 2048, we have 48 attached data nodes and 16 mht child nodes
// for PF_NODE_SIZE == 1024, we have 24 attached data nodes and 8 mht child nodes
// 3/4 of the node size is dedicated to data nodes
// for PF_NODE_SIZE == 4096, we have 96 attached data nodes and 32 MHT child nodes
// 3/4 of the node is dedicated to data nodes, 1/4 to MHT nodes
#define ATTACHED_DATA_NODES_COUNT ((PF_NODE_SIZE / sizeof(gcm_crypto_data_t)) * 3 / 4)
#define CHILD_MHT_NODES_COUNT ((PF_NODE_SIZE / sizeof(gcm_crypto_data_t)) * 1 / 4)
static_assert(ATTACHED_DATA_NODES_COUNT == 96, "ATTACHED_DATA_NODES_COUNT");
// 1/4 of the node size is dedicated to child mht nodes
#define CHILD_MHT_NODES_COUNT ((PF_NODE_SIZE / sizeof(gcm_crypto_data_t)) * 1 / 4)
static_assert(CHILD_MHT_NODES_COUNT == 32, "CHILD_MHT_NODES_COUNT");

typedef struct _metadata_plaintext_header {
uint64_t file_id;
uint8_t major_version;
uint8_t minor_version;
pf_salt_t metadata_key_salt;
pf_tag_t metadata_tag; /* GCM MAC aka Authentication Tag */
} metadata_plaintext_header_t;

typedef struct _metadata_decrypted_header {
char file_path[PATH_MAX_SIZE];
uint64_t file_size;
pf_key_t root_mht_node_key;
pf_tag_t root_mht_node_tag;
uint8_t file_data[MD_USER_DATA_SIZE];
} metadata_decrypted_header_t;

typedef uint8_t metadata_encrypted_blob_t[sizeof(metadata_decrypted_header_t)];

typedef uint8_t metadata_padding_t[PF_NODE_SIZE -
(sizeof(metadata_plaintext_header_t) +
sizeof(metadata_encrypted_blob_t))];

typedef struct _metadata_node {
metadata_plaintext_header_t plaintext_header;
metadata_encrypted_blob_t encrypted_blob;
metadata_padding_t padding;
} metadata_node_t;
static_assert(sizeof(metadata_node_t) == PF_NODE_SIZE, "sizeof(metadata_node_t)");

typedef struct _mht_node {
gcm_crypto_data_t data_nodes_crypto[ATTACHED_DATA_NODES_COUNT];
gcm_crypto_data_t mht_nodes_crypto[CHILD_MHT_NODES_COUNT];
} mht_node_t;

static_assert(sizeof(mht_node_t) == PF_NODE_SIZE, "sizeof(mht_node_t)");

typedef struct _data_node {
uint8_t data[PF_NODE_SIZE];
uint8_t bytes[PF_NODE_SIZE];
} data_node_t;

static_assert(sizeof(data_node_t) == PF_NODE_SIZE, "sizeof(data_node_t)");

typedef struct _encrypted_node {
uint8_t cipher[PF_NODE_SIZE];
uint8_t bytes[PF_NODE_SIZE];
} encrypted_node_t;

static_assert(sizeof(encrypted_node_t) == PF_NODE_SIZE, "sizeof(encrypted_node_t)");

#define MAX_PAGES_IN_CACHE 48

typedef enum {
FILE_MHT_NODE_TYPE = 1,
FILE_DATA_NODE_TYPE = 2,
} mht_node_type_e;

// make sure these are the same size
static_assert(sizeof(mht_node_t) == sizeof(data_node_t),
"sizeof(mht_node_t) == sizeof(data_node_t)");
static_assert(sizeof(mht_node_t) == sizeof(data_node_t), "sizes of MHT and data nodes differ");

DEFINE_LIST(_file_node);
// Data struct that wraps the 4KB encrypted-node buffer (bounce buffer) and the corresponding 4KB
// decrypted-data buffer (plain buffer), plus additional fields. This data struct is used for both
// Data and MHT nodes (but not for Metadata node).
typedef struct _file_node {
LIST_TYPE(_file_node) list;
uint8_t type;
uint64_t node_number;
struct _file_node* parent;
bool need_writing;
struct {
uint64_t physical_node_number;
encrypted_node_t encrypted; // the actual data from the disk
};
union { // decrypted data
struct _file_node* parent;

uint64_t logical_node_number;
uint64_t physical_node_number;

encrypted_node_t encrypted; // encrypted data from storage (bounce buffer)
union { // decrypted data in private memory (plain buffer)
mht_node_t mht;
data_node_t data;
} decrypted;
} file_node_t;
DEFINE_LISTP(_file_node);

typedef struct {
uint32_t index;
uint32_t index; // always "1"; FIXME: what's the point of this?
char label[MAX_LABEL_SIZE]; // must be NULL terminated
pf_keyid_t nonce;
uint32_t output_len; // in bits
pf_salt_t key_salt; // salt for key derivation from KDK, stored in metadata node
uint32_t output_len; // in bits; always 128; FIXME: what's the point of this?
} kdf_input_t;

#pragma pack(pop)
27 changes: 16 additions & 11 deletions common/src/protected_files/protected_files_internal.h
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Original file line number Diff line number Diff line change
Expand Up @@ -14,17 +14,22 @@
#include "protected_files_format.h"

struct pf_context {
metadata_node_t file_metadata; // actual data from disk's meta data node
pf_status_t last_error;
metadata_encrypted_t encrypted_part_plain; // encrypted part of metadata node, decrypted
file_node_t root_mht; // the root of the mht is always needed (for files bigger than 3KB)
pf_handle_t file;
pf_file_mode_t mode;
bool need_writing;
pf_status_t file_status;
pf_key_t user_kdk_key;
lruc_context_t* cache;
pf_handle_t host_file_handle; // opaque file handle (e.g. PAL handle) used by callbacks
pf_file_mode_t mode; // read-only, write-only or read-write
bool need_writing; // whether file was modified and thus needs writing to storage

pf_status_t file_status; // PF_STATUS_SUCCESS, PF_STATUS_CRYPTO_ERROR, etc.
pf_status_t last_error; // FIXME: unclear why this is needed

pf_key_t kdk; // KDK installed by user of PF (e.g. from Gramine manifest)

metadata_node_t metadata_node; // plaintext and encrypted metadata from storage (bounce buffer)
metadata_decrypted_header_t metadata_decrypted_header; // contains file path, size, etc.

file_node_t root_mht_node; // root MHT node is always needed (for files bigger than 3KB)

lruc_context_t* cache; // up to MAX_PAGES_IN_CACHE nodes are cached for each file
#ifdef DEBUG
char* debug_buffer; // buffer for debug output
char* debug_buffer; // buffer for debug output
#endif
};
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