[PATCH v3 02/14] qcrypto/luks: implement encryption key management

[Maxim Levitsky <mlevitsk@redhat.com>]

Next few patches will expose that functionality
to the user.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
 crypto/block-luks.c | 406 +++++++++++++++++++++++++++++++++++++++++++-
 qapi/crypto.json    |  61 ++++++-
 2 files changed, 463 insertions(+), 4 deletions(-)

diff --git a/crypto/block-luks.c b/crypto/block-luks.c
index 4861db810c..26a05d30d4 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 +1076,119 @@ 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;
+    Error *local_err = NULL;
+    int ret;
+
+    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;
+
+    ret = qcrypto_block_luks_store_header(block,  writefunc,
+                                          opaque, &local_err);
+
+    if (ret) {
+        error_propagate(errp, local_err);
+    }
+    /*
+     * 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, &local_err) < 0) {
+            /*
+             * If we failed to get the random data, still write
+             * at least zeros to the key slot at least once
+             */
+            error_propagate(errp, local_err);
+
+            if (i > 0) {
+                return -1;
+            }
+        }
+        if (writefunc(block,
+                      slot->key_offset_sector * QCRYPTO_BLOCK_LUKS_SECTOR_SIZE,
+                      garbagesplitkey,
+                      splitkeylen,
+                      opaque,
+                      &local_err) != splitkeylen) {
+            error_propagate(errp, local_err);
+            return -1;
+        }
+    }
+    return 0;
+}
 
 static int
 qcrypto_block_luks_open(QCryptoBlock *block,
@@ -1099,6 +1219,7 @@ 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 +1285,7 @@ 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 +1326,7 @@ 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 +1366,8 @@ 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 +1595,283 @@ 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 *secret = opts_luks->has_secret ? opts_luks->secret : luks->secret;
+    long slot_count;
+
+    /* 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 == Q_CRYPTO_BLOCKLUKS_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 -1;
+        }
+        if (opts_luks->has_old_secret) {
+            error_setg(errp,
+                       "'old-secret' must not be given when activating keyslots");
+            return -1;
+        }
+
+        /* Locate the password that will be used to retrieve the master key */
+        g_autofree char *old_password;
+        old_password = qcrypto_secret_lookup_as_utf8(secret,  errp);
+        if (!old_password) {
+            return -1;
+        }
+
+        /* 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 -1;
+        }
+
+        /* 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 -1;
+        }
+        if (opts_luks->has_iter_time) {
+            error_setg(errp,
+                       "'iter-time' must not be given when erasing keyslots");
+            return -1;
+        }
+        if (opts_luks->has_secret) {
+            error_setg(errp,
+                       "'secret' must not be given when erasing keyslots");
+            return -1;
+        }
+
+        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 +1920,11 @@ 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 +1961,7 @@ 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..a076b3b938 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' } }
 
+##
+# @QCryptoBlockLUKSKeyslotState:
+#
+# 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': 'QCryptoBlockLUKSKeyslotState',
+  '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
+#
+# @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': 'QCryptoBlockLUKSKeyslotState',
+            '*new-secret': 'str',
+            '*old-secret': 'str',
+            '*keyslot': 'int',
+            '*iter-time': 'int',
+            '*secret': 'str' } }
 
 ##
 # @QCryptoBlockAmendOptions:
@@ -324,4 +381,4 @@
   'base': 'QCryptoBlockOptionsBase',
   'discriminator': 'format',
   'data': {
-            } }
+          'luks': 'QCryptoBlockAmendOptionsLUKS' } }
-- 
2.17.2