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authorDaniel P. Berrange <berrange@redhat.com>2016-09-07 12:43:29 +0100
committerDaniel P. Berrange <berrange@redhat.com>2016-09-19 16:30:45 +0100
commite74aabcffb74e6c15de05255480d43771ec63d8b (patch)
treeafe834d8b8f613b933bcc20e2c2f88e712d58564
parent8813800b7d995d8b54ef0a1e16d41fc13d8b5f3a (diff)
crypto: use correct derived key size when timing pbkdf
Currently when timing the pbkdf algorithm a fixed key size of 32 bytes is used. This results in inaccurate timings for certain hashes depending on their digest size. For example when using sha1 with aes-256, this causes us to measure time for the master key digest doing 2 sha1 operations per iteration, instead of 1. Instead we should pass in the desired key size to the timing routine that matches the key size that will be used for real later. Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
-rw-r--r--crypto/block-luks.c2
-rw-r--r--crypto/pbkdf.c10
-rw-r--r--include/crypto/pbkdf.h6
-rw-r--r--tests/test-crypto-pbkdf.c1
4 files changed, 15 insertions, 4 deletions
diff --git a/crypto/block-luks.c b/crypto/block-luks.c
index 91a4172287..9269aaf488 100644
--- a/crypto/block-luks.c
+++ b/crypto/block-luks.c
@@ -1072,6 +1072,7 @@ qcrypto_block_luks_create(QCryptoBlock *block,
masterkey, luks->header.key_bytes,
luks->header.master_key_salt,
QCRYPTO_BLOCK_LUKS_SALT_LEN,
+ QCRYPTO_BLOCK_LUKS_DIGEST_LEN,
&local_err);
if (local_err) {
error_propagate(errp, local_err);
@@ -1152,6 +1153,7 @@ qcrypto_block_luks_create(QCryptoBlock *block,
(uint8_t *)password, strlen(password),
luks->header.key_slots[0].salt,
QCRYPTO_BLOCK_LUKS_SALT_LEN,
+ luks->header.key_bytes,
&local_err);
if (local_err) {
error_propagate(errp, local_err);
diff --git a/crypto/pbkdf.c b/crypto/pbkdf.c
index e3915058fb..f22e71d183 100644
--- a/crypto/pbkdf.c
+++ b/crypto/pbkdf.c
@@ -65,13 +65,16 @@ static int qcrypto_pbkdf2_get_thread_cpu(unsigned long long *val_ms,
uint64_t qcrypto_pbkdf2_count_iters(QCryptoHashAlgorithm hash,
const uint8_t *key, size_t nkey,
const uint8_t *salt, size_t nsalt,
+ size_t nout,
Error **errp)
{
uint64_t ret = -1;
- uint8_t out[32];
+ uint8_t *out;
uint64_t iterations = (1 << 15);
unsigned long long delta_ms, start_ms, end_ms;
+ out = g_new(uint8_t, nout);
+
while (1) {
if (qcrypto_pbkdf2_get_thread_cpu(&start_ms, errp) < 0) {
goto cleanup;
@@ -80,7 +83,7 @@ uint64_t qcrypto_pbkdf2_count_iters(QCryptoHashAlgorithm hash,
key, nkey,
salt, nsalt,
iterations,
- out, sizeof(out),
+ out, nout,
errp) < 0) {
goto cleanup;
}
@@ -104,6 +107,7 @@ uint64_t qcrypto_pbkdf2_count_iters(QCryptoHashAlgorithm hash,
ret = iterations;
cleanup:
- memset(out, 0, sizeof(out));
+ memset(out, 0, nout);
+ g_free(out);
return ret;
}
diff --git a/include/crypto/pbkdf.h b/include/crypto/pbkdf.h
index 6f4ac85b5c..ef209b3e03 100644
--- a/include/crypto/pbkdf.h
+++ b/include/crypto/pbkdf.h
@@ -133,6 +133,7 @@ int qcrypto_pbkdf2(QCryptoHashAlgorithm hash,
* @nkey: the length of @key in bytes
* @salt: a random salt
* @nsalt: length of @salt in bytes
+ * @nout: size of desired derived key
* @errp: pointer to a NULL-initialized error object
*
* Time the PBKDF2 algorithm to determine how many
@@ -140,13 +141,16 @@ int qcrypto_pbkdf2(QCryptoHashAlgorithm hash,
* key from a user password provided in @key in 1
* second of compute time. The result of this can
* be used as a the @iterations parameter of a later
- * call to qcrypto_pbkdf2().
+ * call to qcrypto_pbkdf2(). The value of @nout should
+ * match that value that will later be provided with
+ * a call to qcrypto_pbkdf2().
*
* Returns: number of iterations in 1 second, -1 on error
*/
uint64_t qcrypto_pbkdf2_count_iters(QCryptoHashAlgorithm hash,
const uint8_t *key, size_t nkey,
const uint8_t *salt, size_t nsalt,
+ size_t nout,
Error **errp);
#endif /* QCRYPTO_PBKDF_H */
diff --git a/tests/test-crypto-pbkdf.c b/tests/test-crypto-pbkdf.c
index 8ceceb1827..a651dc50a3 100644
--- a/tests/test-crypto-pbkdf.c
+++ b/tests/test-crypto-pbkdf.c
@@ -358,6 +358,7 @@ static void test_pbkdf_timing(void)
iters = qcrypto_pbkdf2_count_iters(QCRYPTO_HASH_ALG_SHA256,
key, sizeof(key),
salt, sizeof(salt),
+ 32,
&error_abort);
g_assert(iters >= (1 << 15));