crypto: add support for PBKDF2 algorithm

The LUKS data format includes use of PBKDF2 (Password-Based
Key Derivation Function). The Nettle library can provide
an implementation of this, but we don't want code directly
depending on a specific crypto library backend. Introduce
a new include/crypto/pbkdf.h header which defines a QEMU
API for invoking PBKDK2. The initial implementations are
backed by nettle & gcrypt, which are commonly available
with distros shipping GNUTLS.

The test suite data is taken from the cryptsetup codebase
under the LGPLv2.1+ license. This merely aims to verify
that whatever backend we provide for this function in QEMU
will comply with the spec.

Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

1 files changed, 109 insertions, 0 deletions

diff --git a/crypto/pbkdf.c b/crypto/pbkdf.c
new file mode 100644
index 0000000000..90721d85d6
--- /dev/null
+++ b/crypto/pbkdf.c
@@ -0,0 +1,109 @@
+/*
+ * QEMU Crypto PBKDF support (Password-Based Key Derivation Function)
+ *
+ * Copyright (c) 2015-2016 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "crypto/pbkdf.h"
+#ifndef _WIN32
+#include <sys/resource.h>
+#endif
+
+
+static int qcrypto_pbkdf2_get_thread_cpu(unsigned long long *val_ms,
+                                         Error **errp)
+{
+#ifdef _WIN32
+    FILETIME creation_time, exit_time, kernel_time, user_time;
+    ULARGE_INTEGER thread_time;
+
+    if (!GetThreadTimes(GetCurrentThread(), &creation_time, &exit_time,
+                        &kernel_time, &user_time)) {
+        error_setg(errp, "Unable to get thread CPU usage");
+        return -1;
+    }
+
+    thread_time.LowPart = user_time.dwLowDateTime;
+    thread_time.HighPart = user_time.dwHighDateTime;
+
+    /* QuadPart is units of 100ns and we want ms as unit */
+    *val_ms = thread_time.QuadPart / 10000ll;
+    return 0;
+#elif defined(RUSAGE_THREAD)
+    struct rusage ru;
+    if (getrusage(RUSAGE_THREAD, &ru) < 0) {
+        error_setg_errno(errp, errno, "Unable to get thread CPU usage");
+        return -1;
+    }
+
+    *val_ms = ((ru.ru_utime.tv_sec * 1000ll) +
+               (ru.ru_utime.tv_usec / 1000));
+    return 0;
+#else
+    *val_ms = 0;
+    error_setg(errp, "Unable to calculate thread CPU usage on this platform");
+    return -1;
+#endif
+}
+
+int qcrypto_pbkdf2_count_iters(QCryptoHashAlgorithm hash,
+                               const uint8_t *key, size_t nkey,
+                               const uint8_t *salt, size_t nsalt,
+                               Error **errp)
+{
+    uint8_t out[32];
+    long long int iterations = (1 << 15);
+    unsigned long long delta_ms, start_ms, end_ms;
+
+    while (1) {
+        if (qcrypto_pbkdf2_get_thread_cpu(&start_ms, errp) < 0) {
+            return -1;
+        }
+        if (qcrypto_pbkdf2(hash,
+                           key, nkey,
+                           salt, nsalt,
+                           iterations,
+                           out, sizeof(out),
+                           errp) < 0) {
+            return -1;
+        }
+        if (qcrypto_pbkdf2_get_thread_cpu(&end_ms, errp) < 0) {
+            return -1;
+        }
+
+        delta_ms = end_ms - start_ms;
+
+        if (delta_ms > 500) {
+            break;
+        } else if (delta_ms < 100) {
+            iterations = iterations * 10;
+        } else {
+            iterations = (iterations * 1000 / delta_ms);
+        }
+    }
+
+    iterations = iterations * 1000 / delta_ms;
+
+    if (iterations > INT32_MAX) {
+        error_setg(errp, "Iterations %lld too large for a 32-bit int",
+                   iterations);
+        return -1;
+    }
+
+    return iterations;
+}