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[PATCH v2 02/14] qcrypto/luks: implement encryption key management
|
From: |
Maxim Levitsky |
|
Subject: |
[PATCH v2 02/14] qcrypto/luks: implement encryption key management |
|
Date: |
Sun, 8 Mar 2020 17:18:51 +0200 |
Next few patches will expose that functionality
to the user.
Signed-off-by: Maxim Levitsky <address@hidden>
---
crypto/block-luks.c | 398 +++++++++++++++++++++++++++++++++++++++++++-
qapi/crypto.json | 61 ++++++-
2 files changed, 455 insertions(+), 4 deletions(-)
diff --git a/crypto/block-luks.c b/crypto/block-luks.c
index 4861db810c..b11ee08c6d 100644
--- a/crypto/block-luks.c
+++ b/crypto/block-luks.c
@@ -32,6 +32,7 @@
#include "qemu/uuid.h"
#include "qemu/coroutine.h"
+#include "qemu/bitmap.h"
/*
* Reference for the LUKS format implemented here is
@@ -70,6 +71,9 @@ typedef struct QCryptoBlockLUKSKeySlot
QCryptoBlockLUKSKeySlot;
#define QCRYPTO_BLOCK_LUKS_SECTOR_SIZE 512LL
+#define QCRYPTO_BLOCK_LUKS_DEFAULT_ITER_TIME_MS 2000
+#define QCRYPTO_BLOCK_LUKS_ERASE_ITERATIONS 40
+
static const char qcrypto_block_luks_magic[QCRYPTO_BLOCK_LUKS_MAGIC_LEN] = {
'L', 'U', 'K', 'S', 0xBA, 0xBE
};
@@ -219,6 +223,9 @@ struct QCryptoBlockLUKS {
/* Hash algorithm used in pbkdf2 function */
QCryptoHashAlgorithm hash_alg;
+
+ /* Name of the secret that was used to open the image */
+ char *secret;
};
@@ -1069,6 +1076,108 @@ qcrypto_block_luks_find_key(QCryptoBlock *block,
return -1;
}
+/*
+ * Returns true if a slot i is marked as active
+ * (contains encrypted copy of the master key)
+ */
+static bool
+qcrypto_block_luks_slot_active(const QCryptoBlockLUKS *luks,
+ unsigned int slot_idx)
+{
+ uint32_t val = luks->header.key_slots[slot_idx].active;
+ return val == QCRYPTO_BLOCK_LUKS_KEY_SLOT_ENABLED;
+}
+
+/*
+ * Returns the number of slots that are marked as active
+ * (slots that contain encrypted copy of the master key)
+ */
+static unsigned int
+qcrypto_block_luks_count_active_slots(const QCryptoBlockLUKS *luks)
+{
+ size_t i = 0;
+ unsigned int ret = 0;
+
+ for (i = 0; i < QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS; i++) {
+ if (qcrypto_block_luks_slot_active(luks, i)) {
+ ret++;
+ }
+ }
+ return ret;
+}
+
+/*
+ * Finds first key slot which is not active
+ * Returns the key slot index, or -1 if it doesn't exist
+ */
+static int
+qcrypto_block_luks_find_free_keyslot(const QCryptoBlockLUKS *luks)
+{
+ size_t i;
+
+ for (i = 0; i < QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS; i++) {
+ if (!qcrypto_block_luks_slot_active(luks, i)) {
+ return i;
+ }
+ }
+ return -1;
+}
+
+/*
+ * Erases an keyslot given its index
+ * Returns:
+ * 0 if the keyslot was erased successfully
+ * -1 if a error occurred while erasing the keyslot
+ *
+ */
+static int
+qcrypto_block_luks_erase_key(QCryptoBlock *block,
+ unsigned int slot_idx,
+ QCryptoBlockWriteFunc writefunc,
+ void *opaque,
+ Error **errp)
+{
+ QCryptoBlockLUKS *luks = block->opaque;
+ QCryptoBlockLUKSKeySlot *slot = &luks->header.key_slots[slot_idx];
+ g_autofree uint8_t *garbagesplitkey = NULL;
+ size_t splitkeylen = luks->header.master_key_len * slot->stripes;
+ size_t i;
+
+ assert(slot_idx < QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS);
+ assert(splitkeylen > 0);
+ garbagesplitkey = g_new0(uint8_t, splitkeylen);
+
+ /* Reset the key slot header */
+ memset(slot->salt, 0, QCRYPTO_BLOCK_LUKS_SALT_LEN);
+ slot->iterations = 0;
+ slot->active = QCRYPTO_BLOCK_LUKS_KEY_SLOT_DISABLED;
+
+ qcrypto_block_luks_store_header(block, writefunc, opaque, errp);
+ /*
+ * Now try to erase the key material, even if the header
+ * update failed
+ */
+ for (i = 0; i < QCRYPTO_BLOCK_LUKS_ERASE_ITERATIONS; i++) {
+ if (qcrypto_random_bytes(garbagesplitkey, splitkeylen, errp) < 0) {
+ /*
+ * If we failed to get the random data, still write
+ * at least zeros to the key slot at least once
+ */
+ if (i > 0) {
+ return -1;
+ }
+ }
+ if (writefunc(block,
+ slot->key_offset_sector * QCRYPTO_BLOCK_LUKS_SECTOR_SIZE,
+ garbagesplitkey,
+ splitkeylen,
+ opaque,
+ errp) != splitkeylen) {
+ return -1;
+ }
+ }
+ return 0;
+}
static int
qcrypto_block_luks_open(QCryptoBlock *block,
@@ -1099,6 +1208,7 @@ qcrypto_block_luks_open(QCryptoBlock *block,
luks = g_new0(QCryptoBlockLUKS, 1);
block->opaque = luks;
+ luks->secret = g_strdup(options->u.luks.key_secret);
if (qcrypto_block_luks_load_header(block, readfunc, opaque, errp) < 0) {
goto fail;
@@ -1164,6 +1274,7 @@ qcrypto_block_luks_open(QCryptoBlock *block,
fail:
qcrypto_block_free_cipher(block);
qcrypto_ivgen_free(block->ivgen);
+ g_free(luks->secret);
g_free(luks);
return -1;
}
@@ -1204,7 +1315,7 @@ qcrypto_block_luks_create(QCryptoBlock *block,
memcpy(&luks_opts, &options->u.luks, sizeof(luks_opts));
if (!luks_opts.has_iter_time) {
- luks_opts.iter_time = 2000;
+ luks_opts.iter_time = QCRYPTO_BLOCK_LUKS_DEFAULT_ITER_TIME_MS;
}
if (!luks_opts.has_cipher_alg) {
luks_opts.cipher_alg = QCRYPTO_CIPHER_ALG_AES_256;
@@ -1244,6 +1355,8 @@ qcrypto_block_luks_create(QCryptoBlock *block,
optprefix ? optprefix : "");
goto error;
}
+ luks->secret = g_strdup(options->u.luks.key_secret);
+
password = qcrypto_secret_lookup_as_utf8(luks_opts.key_secret, errp);
if (!password) {
goto error;
@@ -1471,10 +1584,286 @@ qcrypto_block_luks_create(QCryptoBlock *block,
qcrypto_block_free_cipher(block);
qcrypto_ivgen_free(block->ivgen);
+ g_free(luks->secret);
g_free(luks);
return -1;
}
+/*
+ * Given LUKSKeyslotUpdate command, set @slots_bitmap with all slots
+ * that will be updated with new password (or erased)
+ * returns 0 on success, and -1 on failure
+ */
+static int
+qcrypto_block_luks_get_update_bitmap(QCryptoBlock *block,
+ QCryptoBlockReadFunc readfunc,
+ void *opaque,
+ const QCryptoBlockAmendOptionsLUKS *opts,
+ unsigned long *slots_bitmap,
+ Error **errp)
+{
+ const QCryptoBlockLUKS *luks = block->opaque;
+ size_t i;
+
+ bitmap_zero(slots_bitmap, QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS);
+
+ if (opts->has_keyslot) {
+ /* keyslot set, select only this keyslot */
+ int keyslot = opts->keyslot;
+
+ if (keyslot < 0 || keyslot >= QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS) {
+ error_setg(errp,
+ "Invalid slot %u specified, must be between 0 and %u",
+ keyslot, QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS - 1);
+ return -1;
+ }
+ bitmap_set(slots_bitmap, keyslot, 1);
+
+ } else if (opts->has_old_secret) {
+ /* initially select all active keyslots */
+ for (i = 0; i < QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS; i++) {
+ if (qcrypto_block_luks_slot_active(luks, i)) {
+ bitmap_set(slots_bitmap, i, 1);
+ }
+ }
+ } else {
+ /* find a free keyslot */
+ int slot = qcrypto_block_luks_find_free_keyslot(luks);
+
+ if (slot == -1) {
+ error_setg(errp,
+ "Can't add a keyslot - all key slots are in use");
+ return -1;
+ }
+ bitmap_set(slots_bitmap, slot, 1);
+ }
+
+ if (opts->has_old_secret) {
+ /* now deselect all keyslots that don't contain the password */
+ g_autofree uint8_t *tmpkey = g_new0(uint8_t,
+ luks->header.master_key_len);
+
+ for (i = 0; i < QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS; i++) {
+ g_autofree char *old_password = NULL;
+ int rv;
+
+ if (!test_bit(i, slots_bitmap)) {
+ continue;
+ }
+
+ old_password = qcrypto_secret_lookup_as_utf8(opts->old_secret,
+ errp);
+ if (!old_password) {
+ return -1;
+ }
+
+ rv = qcrypto_block_luks_load_key(block,
+ i,
+ old_password,
+ tmpkey,
+ readfunc,
+ opaque,
+ errp);
+ if (rv == -1) {
+ return -1;
+ } else if (rv == 0) {
+ bitmap_clear(slots_bitmap, i, 1);
+ }
+ }
+ }
+ return 0;
+}
+
+/*
+ * Erase a set of keyslots given in @slots_bitmap
+ */
+static int qcrypto_block_luks_erase_keys(QCryptoBlock *block,
+ QCryptoBlockReadFunc readfunc,
+ QCryptoBlockWriteFunc writefunc,
+ void *opaque,
+ unsigned long *slots_bitmap,
+ bool force,
+ Error **errp)
+{
+ QCryptoBlockLUKS *luks = block->opaque;
+ long slot_count = bitmap_count_one(slots_bitmap,
+ QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS);
+ size_t i;
+
+ /* safety checks */
+ if (!force && slot_count == qcrypto_block_luks_count_active_slots(luks)) {
+ error_setg(errp,
+ "Requested operation will erase all active keyslots"
+ " which will erase all the data in the image"
+ " irreversibly - refusing operation");
+ return -EINVAL;
+ }
+
+ /* new apply the update */
+ for (i = 0; i < QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS; i++) {
+ if (!test_bit(i, slots_bitmap)) {
+ continue;
+ }
+ if (qcrypto_block_luks_erase_key(block, i, writefunc, opaque, errp)) {
+ error_append_hint(errp, "Failed to erase keyslot %zu", i);
+ return -EINVAL;
+ }
+ }
+ return 0;
+}
+
+/*
+ * Set a set of keyslots to @master_key encrypted by @new_secret
+ */
+static int qcrypto_block_luks_set_keys(QCryptoBlock *block,
+ QCryptoBlockReadFunc readfunc,
+ QCryptoBlockWriteFunc writefunc,
+ void *opaque,
+ unsigned long *slots_bitmap,
+ uint8_t *master_key,
+ uint64_t iter_time,
+ char *new_secret,
+ bool force,
+ Error **errp)
+{
+ QCryptoBlockLUKS *luks = block->opaque;
+ g_autofree char *new_password = NULL;
+ size_t i;
+
+ /* safety checks */
+ if (!force) {
+ for (i = 0; i < QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS; i++) {
+ if (!test_bit(i, slots_bitmap)) {
+ continue;
+ }
+ if (qcrypto_block_luks_slot_active(luks, i)) {
+ error_setg(errp,
+ "Refusing to overwrite active slot %zu - "
+ "please erase it first", i);
+ return -EINVAL;
+ }
+ }
+ }
+
+ /* Load the new password */
+ new_password = qcrypto_secret_lookup_as_utf8(new_secret, errp);
+ if (!new_password) {
+ return -EINVAL;
+ }
+
+ /* Apply the update */
+ for (i = 0; i < QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS; i++) {
+ if (!test_bit(i, slots_bitmap)) {
+ continue;
+ }
+ if (qcrypto_block_luks_store_key(block, i, new_password, master_key,
+ iter_time, writefunc, opaque, errp)) {
+ error_append_hint(errp, "Failed to write to keyslot %zu", i);
+ return -EINVAL;
+ }
+ }
+ return 0;
+}
+
+static int
+qcrypto_block_luks_amend_options(QCryptoBlock *block,
+ QCryptoBlockReadFunc readfunc,
+ QCryptoBlockWriteFunc writefunc,
+ void *opaque,
+ QCryptoBlockAmendOptions *options,
+ bool force,
+ Error **errp)
+{
+ QCryptoBlockLUKS *luks = block->opaque;
+ QCryptoBlockAmendOptionsLUKS *opts_luks = &options->u.luks;
+ g_autofree uint8_t *master_key = NULL;
+ g_autofree unsigned long *update_bitmap = NULL;
+ char *unlock_secret = NULL;
+ long slot_count;
+
+ unlock_secret = opts_luks->has_unlock_secret ? opts_luks->unlock_secret :
+ luks->secret;
+
+ /* Retrieve set of slots that we need to update */
+ update_bitmap = bitmap_new(QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS);
+ if (qcrypto_block_luks_get_update_bitmap(block, readfunc, opaque,
opts_luks,
+ update_bitmap, errp) != 0) {
+ return -1;
+ }
+
+ slot_count = bitmap_count_one(update_bitmap,
+ QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS);
+
+ /* no matching slots, so nothing to do */
+ if (slot_count == 0) {
+ error_setg(errp, "Requested operation didn't match any slots");
+ return -1;
+ }
+
+ if (opts_luks->state == LUKS_KEYSLOT_STATE_ACTIVE) {
+
+ uint64_t iter_time = opts_luks->has_iter_time ?
+ opts_luks->iter_time :
+ QCRYPTO_BLOCK_LUKS_DEFAULT_ITER_TIME_MS;
+
+ if (!opts_luks->has_new_secret) {
+ error_setg(errp, "'new-secret' is required to activate a keyslot");
+ return -EINVAL;
+ }
+ if (opts_luks->has_old_secret) {
+ error_setg(errp,
+ "'old-secret' must not be given when activating
keyslots");
+ return -EINVAL;
+ }
+
+ /* Locate the password that will be used to retrieve the master key */
+ g_autofree char *old_password;
+ old_password = qcrypto_secret_lookup_as_utf8(unlock_secret, errp);
+ if (!old_password) {
+ return -EINVAL;
+ }
+
+ /* Try to retrieve the master key */
+ master_key = g_new0(uint8_t, luks->header.master_key_len);
+ if (qcrypto_block_luks_find_key(block, old_password, master_key,
+ readfunc, opaque, errp) < 0) {
+ error_append_hint(errp, "Failed to retrieve the master key");
+ return -EINVAL;
+ }
+
+ /* Now set the new keyslots */
+ if (qcrypto_block_luks_set_keys(block, readfunc, writefunc,
+ opaque, update_bitmap, master_key,
+ iter_time,
+ opts_luks->new_secret,
+ force, errp) != 0) {
+ return -1;
+ }
+ } else {
+ if (opts_luks->has_new_secret) {
+ error_setg(errp,
+ "'new-secret' must not be given when erasing keyslots");
+ return -EINVAL;
+ }
+ if (opts_luks->has_iter_time) {
+ error_setg(errp,
+ "'iter-time' must not be given when erasing keyslots");
+ return -EINVAL;
+ }
+ if (opts_luks->has_unlock_secret) {
+ error_setg(errp,
+ "'unlock_secret' must not be given when erasing
keyslots");
+ return -EINVAL;
+ }
+
+ if (qcrypto_block_luks_erase_keys(block, readfunc, writefunc,
+ opaque, update_bitmap, force,
+ errp) != 0) {
+ return -1;
+ }
+ }
+ return 0;
+}
static int qcrypto_block_luks_get_info(QCryptoBlock *block,
QCryptoBlockInfo *info,
@@ -1523,7 +1912,11 @@ static int qcrypto_block_luks_get_info(QCryptoBlock
*block,
static void qcrypto_block_luks_cleanup(QCryptoBlock *block)
{
- g_free(block->opaque);
+ QCryptoBlockLUKS *luks = block->opaque;
+ if (luks) {
+ g_free(luks->secret);
+ g_free(luks);
+ }
}
@@ -1560,6 +1953,7 @@ qcrypto_block_luks_encrypt(QCryptoBlock *block,
const QCryptoBlockDriver qcrypto_block_driver_luks = {
.open = qcrypto_block_luks_open,
.create = qcrypto_block_luks_create,
+ .amend = qcrypto_block_luks_amend_options,
.get_info = qcrypto_block_luks_get_info,
.cleanup = qcrypto_block_luks_cleanup,
.decrypt = qcrypto_block_luks_decrypt,
diff --git a/qapi/crypto.json b/qapi/crypto.json
index 3fd0ce177e..fe600fc608 100644
--- a/qapi/crypto.json
+++ b/qapi/crypto.json
@@ -1,6 +1,8 @@
# -*- Mode: Python -*-
#
+{ 'include': 'common.json' }
+
##
# = Cryptography
##
@@ -297,7 +299,6 @@
'uuid': 'str',
'slots': [ 'QCryptoBlockInfoLUKSSlot' ] }}
-
##
# @QCryptoBlockInfo:
#
@@ -310,7 +311,63 @@
'discriminator': 'format',
'data': { 'luks': 'QCryptoBlockInfoLUKS' } }
+##
+# @LUKSKeyslotState:
+#
+# Defines state of keyslots that are affected by the update
+#
+# @active: The slots contain the given password and marked as active
+# @inactive: The slots are erased (contain garbage) and marked as inactive
+#
+# Since: 5.0
+##
+{ 'enum': 'LUKSKeyslotState',
+ 'data': [ 'active', 'inactive' ] }
+
+##
+# @QCryptoBlockAmendOptionsLUKS:
+#
+# This struct defines the update parameters that activate/de-activate set
+# of keyslots
+#
+# @state: the desired state of the keyslots
+#
+# @new-secret: The ID of a QCryptoSecret object providing the password to be
+# written into added active keyslots
+#
+# @old-secret: Optional (for deactivation only)
+# If given will deactive all keyslots that
+# match password located in QCryptoSecret with this ID
+#
+# @iter-time: Optional (for activation only)
+# Number of milliseconds to spend in
+# PBKDF passphrase processing for the newly activated keyslot.
+# Currently defaults to 2000.
+#
+# @keyslot: Optional. ID of the keyslot to activate/deactivate.
+# For keyslot activation, keyslot should not be active already
+# (this is unsafe to update an active keyslot),
+# but possible if 'force' parameter is given.
+# If keyslot is not given, first free keyslot will be written.
+#
+# For keyslot deactivation, this parameter specifies the exact
+# keyslot to deactivate
+#
+# @unlock-secret: Optional. The ID of a QCryptoSecret object providing the
+# password to use to retrive current master key.
+# Defaults to the same secret that was used to open the image
+#
+#
+# Since 5.0
+##
+{ 'struct': 'QCryptoBlockAmendOptionsLUKS',
+ 'data': { 'state': 'LUKSKeyslotState',
+ '*new-secret': 'str',
+ '*old-secret': 'str',
+ '*keyslot': 'int',
+ '*iter-time': 'int',
+ '*unlock-secret': 'str' } }
##
# @QCryptoBlockAmendOptions:
@@ -324,4 +381,4 @@
'base': 'QCryptoBlockOptionsBase',
'discriminator': 'format',
'data': {
- } }
+ 'luks': 'QCryptoBlockAmendOptionsLUKS' } }
--
2.17.2
[PATCH v2 03/14] block/amend: add 'force' option, Maxim Levitsky, 2020/03/08
[PATCH v2 04/14] block/amend: separate amend and create options for qemu-img, Maxim Levitsky, 2020/03/08
[PATCH v2 06/14] block/crypto: rename two functions, Maxim Levitsky, 2020/03/08
[PATCH v2 07/14] block/crypto: implement the encryption key management, Maxim Levitsky, 2020/03/08
[PATCH v2 08/14] block/qcow2: extend qemu-img amend interface with crypto options, Maxim Levitsky, 2020/03/08