Implement master key for wrapping keys in the keystore.

The KEK (Key Encryption Key) is first fetched from the FPGA that gets it
from the volatile Master Key Memory (that in theory has tamper*kek_len =
len protection with wiping), and secondly from flash.

The flash option is meant for development/evaluation use using an Alpha
board where the Master Key Memory is not battery backed. For any serious
use of an Alpha, an option is to enter the master key into the volatile
MKM on each power-on as a way to unlock the keystore.

4 files changed, 282 insertions, 4 deletions

diff --git a/GNUmakefile b/GNUmakefile
index 14e94c6..151ce5c 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -118,7 +118,7 @@ ifeq "${KS}" "mmap"
 else ifeq "${KS}" "volatile"
   KS_OBJ += ks_volatile.o
 else ifeq "${KS}" "flash"
-  KS_OBJ += ks_flash.o
+  KS_OBJ += ks_flash.o masterkey.o
 endif
 
 # RPC_MODE = none | server | client-simple | client-mixed
diff --git a/ks_flash.c b/ks_flash.c
index 09a9847..036e72e 100644
--- a/ks_flash.c
+++ b/ks_flash.c
@@ -40,6 +40,7 @@
 
 #define HAL_OK CMIS_HAL_OK
 #include "stm-keystore.h"
+#include "masterkey.h"
 #undef HAL_OK
 
 #include <string.h>
@@ -323,10 +324,16 @@ hal_error_t hal_ks_get_kek(uint8_t *kek,
                       (kek_max < bitsToBytes(256)) ? bitsToBytes(192) :
                       bitsToBytes(256));
 
-  #warning Faking the Key Encryption Key
-  memset(kek, 4, len);
+  if (masterkey_volatile_read(kek, len) == HSM_MASTERKEY_SET) {
+      *kek_len = len;
+      return LIBHAL_OK;
+  }
+  if (masterkey_flash_read(kek, len) == HSM_MASTERKEY_SET) {
+      *kek_len = len;
+      return LIBHAL_OK;
+  }
 
-  return LIBHAL_OK;
+  return HAL_ERROR_KEYSTORE_ACCESS;
 }
 
 
diff --git a/masterkey.c b/masterkey.c
new file mode 100644
index 0000000..cc9a62f
--- /dev/null
+++ b/masterkey.c
@@ -0,0 +1,218 @@
+/*
+ * masterkey.c
+ * -----------
+ * Masterkey set/get functions.
+ *
+ * Copyright (c) 2016, NORDUnet A/S All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ * - Redistributions of source code must retain the above copyright notice,
+ *   this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the distribution.
+ *
+ * - Neither the name of the NORDUnet nor the names of its contributors may
+ *   be used to endorse or promote products derived from this software
+ *   without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+ * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+ * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
+ * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define HAL_OK CMIS_HAL_OK
+#include "stm-init.h"
+#include "stm-keystore.h"
+#undef HAL_OK
+
+#define HAL_OK LIBHAL_OK
+#include "hal.h"
+#include "masterkey.h"
+#undef HAL_OK
+
+#include <string.h>
+
+
+static int volatile_init = 0, flash_init = 0;
+static const hal_core_t *core = NULL;
+
+#define MKM_VOLATILE_STATUS_ADDRESS	0
+#define SCLK_DIV			0x20
+#define MKM_FLASH_STATUS_ADDRESS	(KEYSTORE_SECTOR_SIZE * (KEYSTORE_NUM_SECTORS - 1))
+#define MKM_FLASH_STATUS_IN_USE		0x0000ffff
+#define KEK_LENGTH (256 / 8)
+
+
+hal_error_t masterkey_volatile_init()
+{
+    hal_error_t err;
+    uint32_t status;
+
+    if (! volatile_init) {
+	if ((core = hal_core_find(MKMIF_NAME, NULL)) == NULL) {
+	    return HAL_ERROR_CORE_NOT_FOUND;
+	}
+
+	err =
+	    hal_mkmif_set_clockspeed(core, SCLK_DIV) ||
+	    hal_mkmif_init(core) ||
+	    hal_mkmif_read_word(core, MKM_VOLATILE_STATUS_ADDRESS, &status);
+
+	if (err != LIBHAL_OK) return err;
+
+	if (status != HSM_MASTERKEY_SET &&
+	    status != HSM_MASTERKEY_NOT_SET) {
+	    if ((err = hal_mkmif_write_word(core, MKM_VOLATILE_STATUS_ADDRESS, HSM_MASTERKEY_NOT_SET)) != LIBHAL_OK) {
+		return err;
+	    }
+	}
+
+	volatile_init = 1;
+    }
+    return LIBHAL_OK;
+}
+
+masterkey_status_t masterkey_volatile_read(uint8_t *buf, size_t len)
+{
+    hal_error_t err;
+    uint32_t status;
+
+    err =
+	masterkey_volatile_init() ||
+	hal_mkmif_read_word(core, MKM_VOLATILE_STATUS_ADDRESS, &status);
+
+    if (err != LIBHAL_OK) return HSM_MASTERKEY_FAIL;
+
+    if (buf != NULL && status == HSM_MASTERKEY_SET) {
+	if ((err = hal_mkmif_read(core, MKM_VOLATILE_STATUS_ADDRESS + 4, buf, len)) == LIBHAL_OK) {
+	    return HSM_MASTERKEY_SET;
+	}
+    }
+
+    if (status == HSM_MASTERKEY_SET || status == HSM_MASTERKEY_NOT_SET) {
+	return (masterkey_status_t) status;
+    }
+
+    return HSM_MASTERKEY_FAIL;
+}
+
+masterkey_status_t masterkey_volatile_write(uint8_t *buf, size_t len)
+{
+    hal_error_t err;
+
+    if (len != KEK_LENGTH) return HSM_MASTERKEY_FAIL;
+    if (! buf) return HSM_MASTERKEY_FAIL;
+
+    err =
+	masterkey_volatile_init() ||
+	hal_mkmif_write(core, MKM_VOLATILE_STATUS_ADDRESS + 4, buf, len) ||
+	hal_mkmif_write_word(core, MKM_VOLATILE_STATUS_ADDRESS, HSM_MASTERKEY_SET);
+
+    if (err != LIBHAL_OK) return HSM_MASTERKEY_FAIL;
+
+    return HSM_MASTERKEY_OK;
+}
+
+masterkey_status_t masterkey_volatile_erase(size_t len)
+{
+    uint8_t buf[KEK_LENGTH] = {0};
+    hal_error_t err;
+
+    if (len != KEK_LENGTH) return HSM_MASTERKEY_FAIL;
+
+    err =
+	masterkey_volatile_init() ||
+	hal_mkmif_write(core, MKM_VOLATILE_STATUS_ADDRESS + 4, buf, sizeof(buf)) ||
+	hal_mkmif_write_word(core, MKM_VOLATILE_STATUS_ADDRESS, HSM_MASTERKEY_NOT_SET);
+
+    if (err != LIBHAL_OK) return HSM_MASTERKEY_FAIL;
+
+    return HSM_MASTERKEY_OK;
+}
+
+/* Storing the master key in flash is a pretty Bad Idea, but since the Alpha board
+ * doesn't have a battery mounted (only pin headers for attaching one), it might
+ * help in non-production use where one doesn't have tamper protection anyways.
+ *
+ * For production use on the Alpha, one option is to have the Master Key on paper
+ * and enter it into volatile RAM after each power on.
+ */
+hal_error_t masterkey_flash_init()
+{
+    if (! flash_init) {
+	if (! keystore_check_id()) return HAL_ERROR_IO_UNEXPECTED;
+	flash_init = 1;
+    }
+    return LIBHAL_OK;
+}
+
+masterkey_status_t masterkey_flash_read(uint8_t *buf, size_t len)
+{
+    uint8_t page[KEYSTORE_PAGE_SIZE];
+    uint32_t *status = (uint32_t *) page;
+
+    if (len > sizeof(page) - 4) return HSM_MASTERKEY_FAIL;
+
+    if (masterkey_flash_init() != LIBHAL_OK) return HSM_MASTERKEY_FAIL;
+
+    if (! keystore_read_data(MKM_FLASH_STATUS_ADDRESS, page, sizeof(page))) {
+	memset(page, 0, sizeof(page));
+	return HSM_MASTERKEY_FAIL;
+    }
+
+    if (buf != NULL && len) memcpy(buf, page + 4, len);
+
+    memset(page + 4, 0, sizeof(page) - 4);
+
+    if (*status == MKM_FLASH_STATUS_IN_USE) return HSM_MASTERKEY_SET;
+    if (*status == 0x0 || *status == 0xffffffff) return HSM_MASTERKEY_NOT_SET;
+
+    return HSM_MASTERKEY_FAIL;
+}
+
+masterkey_status_t masterkey_flash_write(uint8_t *buf, size_t len)
+{
+    uint8_t page[KEYSTORE_PAGE_SIZE] = {0xff};
+    uint32_t *status = (uint32_t *) page;
+    int res;
+
+    if (len > sizeof(page) - 4) return HSM_MASTERKEY_FAIL;
+    if (buf == NULL) return HSM_MASTERKEY_FAIL;
+
+    if (masterkey_flash_init() != LIBHAL_OK) return HSM_MASTERKEY_FAIL;
+
+    *status = MKM_FLASH_STATUS_IN_USE;
+    memcpy(page + 4, buf, len);
+
+    res = keystore_write_data(MKM_FLASH_STATUS_ADDRESS, page, sizeof(page));
+    memset(page, 0, sizeof(page));
+    if (res != 1) {
+	return HSM_MASTERKEY_FAIL;
+    }
+
+    return HSM_MASTERKEY_OK;
+}
+
+masterkey_status_t masterkey_flash_erase(size_t len)
+{
+    if (len > KEYSTORE_PAGE_SIZE - 4) return HSM_MASTERKEY_FAIL;
+
+    if (keystore_erase_sectors(MKM_FLASH_STATUS_ADDRESS / KEYSTORE_SECTOR_SIZE,
+			       MKM_FLASH_STATUS_ADDRESS / KEYSTORE_SECTOR_SIZE) != 1) {
+	return HSM_MASTERKEY_FAIL;
+    }
+
+    return HSM_MASTERKEY_OK;
+}
diff --git a/masterkey.h b/masterkey.h
new file mode 100644
index 0000000..8b47409
--- /dev/null
+++ b/masterkey.h
@@ -0,0 +1,53 @@
+/*
+ * masterkey.h
+ * -----------
+ * Code to handle the Master Key that wraps all the keys in the keystore.
+ *
+ * Copyright (c) 2016, NORDUnet A/S All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ * - Redistributions of source code must retain the above copyright notice,
+ *   this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the distribution.
+ *
+ * - Neither the name of the NORDUnet nor the names of its contributors may
+ *   be used to endorse or promote products derived from this software
+ *   without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
+ * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+ * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
+ * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef __STM32_HSM_MASTERKEY_H
+#define __STM32_HSM_MASTERKEY_H
+
+typedef enum {
+    HSM_MASTERKEY_FAIL,
+    HSM_MASTERKEY_OK,
+    HSM_MASTERKEY_SET,
+    HSM_MASTERKEY_NOT_SET,
+} masterkey_status_t;
+
+extern masterkey_status_t masterkey_volatile_read(uint8_t *buf, size_t len);
+extern masterkey_status_t masterkey_volatile_write(uint8_t *buf, size_t len);
+extern masterkey_status_t masterkey_volatile_erase(size_t len);
+
+extern masterkey_status_t masterkey_flash_read(uint8_t *buf, size_t len);
+extern masterkey_status_t masterkey_flash_write(uint8_t *buf, size_t len);
+extern masterkey_status_t masterkey_flash_erase(size_t len);
+
+#endif /* __STM32_HSM_MASTERKEY_H */