[Qemu-devel] [PATCH 02/13] qcrypto-luks: misc refactoring

[Maxim Levitsky <mlevitsk@redhat.com>]

This is also a preparation for key read/write/erase functions

* use master key len from the header
* prefer to use crypto params in the QCryptoBlockLUKS
  over passing them as function arguments
* define QCRYPTO_BLOCK_LUKS_DEFAULT_ITER_TIME
* Add comments to various crypto parameters in the QCryptoBlockLUKS

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
 crypto/block-luks.c | 213 ++++++++++++++++++++++----------------------
 1 file changed, 105 insertions(+), 108 deletions(-)

diff --git a/crypto/block-luks.c b/crypto/block-luks.c
index 409ab50f20..48213abde7 100644
--- a/crypto/block-luks.c
+++ b/crypto/block-luks.c
@@ -70,6 +70,8 @@ typedef struct QCryptoBlockLUKSKeySlot QCryptoBlockLUKSKeySlot;
 
 #define QCRYPTO_BLOCK_LUKS_SECTOR_SIZE 512LL
 
+#define QCRYPTO_BLOCK_LUKS_DEFAULT_ITER_TIME 2000
+
 static const char qcrypto_block_luks_magic[QCRYPTO_BLOCK_LUKS_MAGIC_LEN] = {
     'L', 'U', 'K', 'S', 0xBA, 0xBE
 };
@@ -199,13 +201,25 @@ QEMU_BUILD_BUG_ON(sizeof(struct QCryptoBlockLUKSHeader) != 592);
 struct QCryptoBlockLUKS {
     QCryptoBlockLUKSHeader header;
 
-    /* Cache parsed versions of what's in header fields,
-     * as we can't rely on QCryptoBlock.cipher being
-     * non-NULL */
+    /* Main encryption algorithm used for encryption*/
     QCryptoCipherAlgorithm cipher_alg;
+
+    /* Mode of encryption for the selected encryption algorithm */
     QCryptoCipherMode cipher_mode;
+
+    /* Initialization vector generation algorithm */
     QCryptoIVGenAlgorithm ivgen_alg;
+
+    /* Hash algorithm used for IV generation*/
     QCryptoHashAlgorithm ivgen_hash_alg;
+
+    /*
+     * Encryption algorithm used for IV generation.
+     * Usually the same as main encryption algorithm
+     */
+    QCryptoCipherAlgorithm ivgen_cipher_alg;
+
+    /* Hash algorithm used in pbkdf2 function */
     QCryptoHashAlgorithm hash_alg;
 };
 
@@ -397,6 +411,12 @@ qcrypto_block_luks_essiv_cipher(QCryptoCipherAlgorithm cipher,
     }
 }
 
+static int masterkeylen(QCryptoBlockLUKS *luks)
+{
+    return luks->header.key_bytes;
+}
+
+
 /*
  * Given a key slot, and user password, this will attempt to unlock
  * the master encryption key from the key slot.
@@ -410,21 +430,15 @@ qcrypto_block_luks_essiv_cipher(QCryptoCipherAlgorithm cipher,
  */
 static int
 qcrypto_block_luks_load_key(QCryptoBlock *block,
-                            QCryptoBlockLUKSKeySlot *slot,
+                            uint slot_idx,
                             const char *password,
-                            QCryptoCipherAlgorithm cipheralg,
-                            QCryptoCipherMode ciphermode,
-                            QCryptoHashAlgorithm hash,
-                            QCryptoIVGenAlgorithm ivalg,
-                            QCryptoCipherAlgorithm ivcipheralg,
-                            QCryptoHashAlgorithm ivhash,
                             uint8_t *masterkey,
-                            size_t masterkeylen,
                             QCryptoBlockReadFunc readfunc,
                             void *opaque,
                             Error **errp)
 {
     QCryptoBlockLUKS *luks = block->opaque;
+    QCryptoBlockLUKSKeySlot *slot = &luks->header.key_slots[slot_idx];
     uint8_t *splitkey;
     size_t splitkeylen;
     uint8_t *possiblekey;
@@ -439,9 +453,9 @@ qcrypto_block_luks_load_key(QCryptoBlock *block,
         return 0;
     }
 
-    splitkeylen = masterkeylen * slot->stripes;
+    splitkeylen = masterkeylen(luks) * slot->stripes;
     splitkey = g_new0(uint8_t, splitkeylen);
-    possiblekey = g_new0(uint8_t, masterkeylen);
+    possiblekey = g_new0(uint8_t, masterkeylen(luks));
 
     /*
      * The user password is used to generate a (possible)
@@ -450,11 +464,11 @@ qcrypto_block_luks_load_key(QCryptoBlock *block,
      * the key is correct and validate the results of
      * decryption later.
      */
-    if (qcrypto_pbkdf2(hash,
+    if (qcrypto_pbkdf2(luks->hash_alg,
                        (const uint8_t *)password, strlen(password),
                        slot->salt, QCRYPTO_BLOCK_LUKS_SALT_LEN,
                        slot->iterations,
-                       possiblekey, masterkeylen,
+                       possiblekey, masterkeylen(luks),
                        errp) < 0) {
         goto cleanup;
     }
@@ -478,19 +492,19 @@ qcrypto_block_luks_load_key(QCryptoBlock *block,
 
     /* Setup the cipher/ivgen that we'll use to try to decrypt
      * the split master key material */
-    cipher = qcrypto_cipher_new(cipheralg, ciphermode,
-                                possiblekey, masterkeylen,
+    cipher = qcrypto_cipher_new(luks->cipher_alg, luks->cipher_mode,
+                                possiblekey, masterkeylen(luks),
                                 errp);
     if (!cipher) {
         goto cleanup;
     }
 
-    niv = qcrypto_cipher_get_iv_len(cipheralg,
-                                    ciphermode);
-    ivgen = qcrypto_ivgen_new(ivalg,
-                              ivcipheralg,
-                              ivhash,
-                              possiblekey, masterkeylen,
+    niv = qcrypto_cipher_get_iv_len(luks->cipher_alg,
+                                    luks->cipher_mode);
+    ivgen = qcrypto_ivgen_new(luks->ivgen_alg,
+                              luks->ivgen_cipher_alg,
+                              luks->ivgen_hash_alg,
+                              possiblekey, masterkeylen(luks),
                               errp);
     if (!ivgen) {
         goto cleanup;
@@ -519,8 +533,8 @@ qcrypto_block_luks_load_key(QCryptoBlock *block,
      * Now we've decrypted the split master key, join
      * it back together to get the actual master key.
      */
-    if (qcrypto_afsplit_decode(hash,
-                               masterkeylen,
+    if (qcrypto_afsplit_decode(luks->hash_alg,
+                               masterkeylen(luks),
                                slot->stripes,
                                splitkey,
                                masterkey,
@@ -537,8 +551,8 @@ qcrypto_block_luks_load_key(QCryptoBlock *block,
      * then comparing that to the hash stored in the key slot
      * header
      */
-    if (qcrypto_pbkdf2(hash,
-                       masterkey, masterkeylen,
+    if (qcrypto_pbkdf2(luks->hash_alg,
+                       masterkey, masterkeylen(luks),
                        luks->header.master_key_salt,
                        QCRYPTO_BLOCK_LUKS_SALT_LEN,
                        luks->header.master_key_iterations,
@@ -577,37 +591,19 @@ qcrypto_block_luks_load_key(QCryptoBlock *block,
 static int
 qcrypto_block_luks_find_key(QCryptoBlock *block,
                             const char *password,
-                            QCryptoCipherAlgorithm cipheralg,
-                            QCryptoCipherMode ciphermode,
-                            QCryptoHashAlgorithm hash,
-                            QCryptoIVGenAlgorithm ivalg,
-                            QCryptoCipherAlgorithm ivcipheralg,
-                            QCryptoHashAlgorithm ivhash,
-                            uint8_t **masterkey,
-                            size_t *masterkeylen,
+                            uint8_t *masterkey,
                             QCryptoBlockReadFunc readfunc,
                             void *opaque,
                             Error **errp)
 {
-    QCryptoBlockLUKS *luks = block->opaque;
     size_t i;
     int rv;
 
-    *masterkey = g_new0(uint8_t, luks->header.key_bytes);
-    *masterkeylen = luks->header.key_bytes;
-
     for (i = 0; i < QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS; i++) {
         rv = qcrypto_block_luks_load_key(block,
-                                         &luks->header.key_slots[i],
+                                         i,
                                          password,
-                                         cipheralg,
-                                         ciphermode,
-                                         hash,
-                                         ivalg,
-                                         ivcipheralg,
-                                         ivhash,
-                                         *masterkey,
-                                         *masterkeylen,
+                                         masterkey,
                                          readfunc,
                                          opaque,
                                          errp);
@@ -620,11 +616,7 @@ qcrypto_block_luks_find_key(QCryptoBlock *block,
     }
 
     error_setg(errp, "Invalid password, cannot unlock any keyslot");
-
  error:
-    g_free(*masterkey);
-    *masterkey = NULL;
-    *masterkeylen = 0;
     return -1;
 }
 
@@ -639,21 +631,15 @@ qcrypto_block_luks_open(QCryptoBlock *block,
                         size_t n_threads,
                         Error **errp)
 {
-    QCryptoBlockLUKS *luks;
+    QCryptoBlockLUKS *luks = NULL;
     Error *local_err = NULL;
     int ret = 0;
     size_t i;
     ssize_t rv;
     uint8_t *masterkey = NULL;
-    size_t masterkeylen;
     char *ivgen_name, *ivhash_name;
-    QCryptoCipherMode ciphermode;
-    QCryptoCipherAlgorithm cipheralg;
-    QCryptoIVGenAlgorithm ivalg;
-    QCryptoCipherAlgorithm ivcipheralg;
-    QCryptoHashAlgorithm hash;
-    QCryptoHashAlgorithm ivhash;
     char *password = NULL;
+    char *cipher_mode = NULL;
 
     if (!(flags & QCRYPTO_BLOCK_OPEN_NO_IO)) {
         if (!options->u.luks.key_secret) {
@@ -710,6 +696,8 @@ qcrypto_block_luks_open(QCryptoBlock *block,
         goto fail;
     }
 
+    cipher_mode = g_strdup(luks->header.cipher_mode);
+
     /*
      * The cipher_mode header contains a string that we have
      * to further parse, of the format
@@ -718,7 +706,7 @@ qcrypto_block_luks_open(QCryptoBlock *block,
      *
      * eg  cbc-essiv:sha256, cbc-plain64
      */
-    ivgen_name = strchr(luks->header.cipher_mode, '-');
+    ivgen_name = strchr(cipher_mode, '-');
     if (!ivgen_name) {
         ret = -EINVAL;
         error_setg(errp, "Unexpected cipher mode string format %s",
@@ -730,13 +718,13 @@ qcrypto_block_luks_open(QCryptoBlock *block,
 
     ivhash_name = strchr(ivgen_name, ':');
     if (!ivhash_name) {
-        ivhash = 0;
+        luks->ivgen_hash_alg = 0;
     } else {
         *ivhash_name = '\0';
         ivhash_name++;
 
-        ivhash = qcrypto_block_luks_hash_name_lookup(ivhash_name,
-                                                     &local_err);
+        luks->ivgen_hash_alg = qcrypto_block_luks_hash_name_lookup(ivhash_name,
+                                                                   &local_err);
         if (local_err) {
             ret = -ENOTSUP;
             error_propagate(errp, local_err);
@@ -744,25 +732,27 @@ qcrypto_block_luks_open(QCryptoBlock *block,
         }
     }
 
-    ciphermode = qcrypto_block_luks_cipher_mode_lookup(luks->header.cipher_mode,
-                                                       &local_err);
+    luks->cipher_mode = qcrypto_block_luks_cipher_mode_lookup(cipher_mode,
+                                                              &local_err);
     if (local_err) {
         ret = -ENOTSUP;
         error_propagate(errp, local_err);
         goto fail;
     }
 
-    cipheralg = qcrypto_block_luks_cipher_name_lookup(luks->header.cipher_name,
-                                                      ciphermode,
-                                                      luks->header.key_bytes,
-                                                      &local_err);
+    luks->cipher_alg =
+            qcrypto_block_luks_cipher_name_lookup(luks->header.cipher_name,
+                                                  luks->cipher_mode,
+                                                  luks->header.key_bytes,
+                                                  &local_err);
     if (local_err) {
         ret = -ENOTSUP;
         error_propagate(errp, local_err);
         goto fail;
     }
 
-    hash = qcrypto_block_luks_hash_name_lookup(luks->header.hash_spec,
+    luks->hash_alg =
+            qcrypto_block_luks_hash_name_lookup(luks->header.hash_spec,
                                                &local_err);
     if (local_err) {
         ret = -ENOTSUP;
@@ -770,23 +760,24 @@ qcrypto_block_luks_open(QCryptoBlock *block,
         goto fail;
     }
 
-    ivalg = qcrypto_block_luks_ivgen_name_lookup(ivgen_name,
-                                                 &local_err);
+    luks->ivgen_alg = qcrypto_block_luks_ivgen_name_lookup(ivgen_name,
+                                                           &local_err);
     if (local_err) {
         ret = -ENOTSUP;
         error_propagate(errp, local_err);
         goto fail;
     }
 
-    if (ivalg == QCRYPTO_IVGEN_ALG_ESSIV) {
+    if (luks->ivgen_alg == QCRYPTO_IVGEN_ALG_ESSIV) {
         if (!ivhash_name) {
             ret = -EINVAL;
             error_setg(errp, "Missing IV generator hash specification");
             goto fail;
         }
-        ivcipheralg = qcrypto_block_luks_essiv_cipher(cipheralg,
-                                                      ivhash,
-                                                      &local_err);
+        luks->ivgen_cipher_alg =
+                qcrypto_block_luks_essiv_cipher(luks->cipher_alg,
+                                                luks->ivgen_hash_alg,
+                                                &local_err);
         if (local_err) {
             ret = -ENOTSUP;
             error_propagate(errp, local_err);
@@ -800,21 +791,25 @@ qcrypto_block_luks_open(QCryptoBlock *block,
          * ignore hash names with these ivgens rather than report
          * an error about the invalid usage
          */
-        ivcipheralg = cipheralg;
+        luks->ivgen_cipher_alg = luks->cipher_alg;
     }
 
+
+    g_free(cipher_mode);
+    cipher_mode = NULL;
+    ivgen_name = NULL;
+    ivhash_name = NULL;
+
     if (!(flags & QCRYPTO_BLOCK_OPEN_NO_IO)) {
         /* Try to find which key slot our password is valid for
          * and unlock the master key from that slot.
          */
+
+        masterkey = g_new0(uint8_t, masterkeylen(luks));
+
         if (qcrypto_block_luks_find_key(block,
                                         password,
-                                        cipheralg, ciphermode,
-                                        hash,
-                                        ivalg,
-                                        ivcipheralg,
-                                        ivhash,
-                                        &masterkey, &masterkeylen,
+                                        masterkey,
                                         readfunc, opaque,
                                         errp) < 0) {
             ret = -EACCES;
@@ -824,21 +819,24 @@ qcrypto_block_luks_open(QCryptoBlock *block,
         /* We have a valid master key now, so can setup the
          * block device payload decryption objects
          */
-        block->kdfhash = hash;
-        block->niv = qcrypto_cipher_get_iv_len(cipheralg,
-                                               ciphermode);
-        block->ivgen = qcrypto_ivgen_new(ivalg,
-                                         ivcipheralg,
-                                         ivhash,
-                                         masterkey, masterkeylen,
+        block->kdfhash = luks->hash_alg;
+        block->niv = qcrypto_cipher_get_iv_len(luks->cipher_alg,
+                                               luks->cipher_mode);
+
+        block->ivgen = qcrypto_ivgen_new(luks->ivgen_alg,
+                                         luks->ivgen_cipher_alg,
+                                         luks->ivgen_hash_alg,
+                                         masterkey, masterkeylen(luks),
                                          errp);
         if (!block->ivgen) {
             ret = -ENOTSUP;
             goto fail;
         }
 
-        ret = qcrypto_block_init_cipher(block, cipheralg, ciphermode,
-                                        masterkey, masterkeylen, n_threads,
+        ret = qcrypto_block_init_cipher(block, luks->cipher_alg,
+                                        luks->cipher_mode,
+                                        masterkey, masterkeylen(luks),
+                                        n_threads,
                                         errp);
         if (ret < 0) {
             ret = -ENOTSUP;
@@ -850,12 +848,6 @@ qcrypto_block_luks_open(QCryptoBlock *block,
     block->payload_offset = luks->header.payload_offset *
         block->sector_size;
 
-    luks->cipher_alg = cipheralg;
-    luks->cipher_mode = ciphermode;
-    luks->ivgen_alg = ivalg;
-    luks->ivgen_hash_alg = ivhash;
-    luks->hash_alg = hash;
-
     g_free(masterkey);
     g_free(password);
 
@@ -910,7 +902,7 @@ 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;
     }
     if (!luks_opts.has_cipher_alg) {
         luks_opts.cipher_alg = QCRYPTO_CIPHER_ALG_AES_256;
@@ -930,6 +922,17 @@ qcrypto_block_luks_create(QCryptoBlock *block,
             luks_opts.has_ivgen_hash_alg = true;
         }
     }
+
+    luks = g_new0(QCryptoBlockLUKS, 1);
+    block->opaque = luks;
+
+    luks->cipher_alg = luks_opts.cipher_alg;
+    luks->cipher_mode = luks_opts.cipher_mode;
+    luks->ivgen_alg = luks_opts.ivgen_alg;
+    luks->ivgen_hash_alg = luks_opts.ivgen_hash_alg;
+    luks->hash_alg = luks_opts.hash_alg;
+
+
     /* Note we're allowing ivgen_hash_alg to be set even for
      * non-essiv iv generators that don't need a hash. It will
      * be silently ignored, for compatibility with dm-crypt */
@@ -944,8 +947,6 @@ qcrypto_block_luks_create(QCryptoBlock *block,
         return -1;
     }
 
-    luks = g_new0(QCryptoBlockLUKS, 1);
-    block->opaque = luks;
 
     memcpy(luks->header.magic, qcrypto_block_luks_magic,
            QCRYPTO_BLOCK_LUKS_MAGIC_LEN);
@@ -1003,6 +1004,8 @@ qcrypto_block_luks_create(QCryptoBlock *block,
         ivcipheralg = luks_opts.cipher_alg;
     }
 
+    luks->ivgen_cipher_alg = ivcipheralg;
+
     strcpy(luks->header.cipher_name, cipher_alg);
     strcpy(luks->header.cipher_mode, cipher_mode_spec);
     strcpy(luks->header.hash_spec, hash_alg);
@@ -1304,12 +1307,6 @@ qcrypto_block_luks_create(QCryptoBlock *block,
         goto error;
     }
 
-    luks->cipher_alg = luks_opts.cipher_alg;
-    luks->cipher_mode = luks_opts.cipher_mode;
-    luks->ivgen_alg = luks_opts.ivgen_alg;
-    luks->ivgen_hash_alg = luks_opts.ivgen_hash_alg;
-    luks->hash_alg = luks_opts.hash_alg;
-
     memset(masterkey, 0, luks->header.key_bytes);
     g_free(masterkey);
     memset(slotkey, 0, luks->header.key_bytes);
-- 
2.17.2