stm32/mboot: Add support for signed and encrypted firmware updates.

This commit adds support to stm32's mboot for signe, encrypted and
compressed DFU updates.  It is based on inital work done by Andrew Leech.

The feature is enabled by setting MBOOT_ENABLE_PACKING to 1 in the board's
mpconfigboard.mk file, and by providing a header file in the board folder
(usually called mboot_keys.h) with a set of signing and encryption keys
(which can be generated by mboot_pack_dfu.py).  The signing and encryption
is provided by libhydrogen.  Compression is provided by uzlib.  Enabling
packing costs about 3k of flash.

The included mboot_pack_dfu.py script converts a .dfu file to a .pack.dfu
file which can be subsequently deployed to a board with mboot in packing
mode.  This .pack.dfu file is created as follows:
- the firmware from the original .dfu is split into chunks (so the
  decryption can fit in RAM)
- each chunk is compressed, encrypted, a header added, then signed
- a special final chunk is added with a signature of the entire firmware
- all chunks are concatenated to make the final .pack.dfu file

The .pack.dfu file can be deployed over USB or from the internal filesystem
on the device (if MBOOT_FSLOAD is enabled).

See #5267 and #5309 for additional discussion.
Signed-off-by: Damien George <damien@micropython.org>

ports/stm32/Makefile

@@ -30,7 +30,7 @@ FROZEN_MANIFEST ?= boards/manifest.py
 # include py core make definitions
 include $(TOP)/py/py.mk
 
-GIT_SUBMODULES = lib/lwip lib/mbedtls lib/mynewt-nimble lib/stm32lib
+GIT_SUBMODULES = lib/libhydrogen lib/lwip lib/mbedtls lib/mynewt-nimble lib/stm32lib
 
 MCU_SERIES_UPPER = $(shell echo $(MCU_SERIES) | tr '[:lower:]' '[:upper:]')
 CMSIS_MCU_LOWER = $(shell echo $(CMSIS_MCU) | tr '[:upper:]' '[:lower:]')
@@ -41,6 +41,7 @@ HAL_DIR=lib/stm32lib/STM32$(MCU_SERIES_UPPER)xx_HAL_Driver
 USBDEV_DIR=usbdev
 #USBHOST_DIR=usbhost
 DFU=$(TOP)/tools/dfu.py
+MBOOT_PACK_DFU = mboot/mboot_pack_dfu.py
 # may need to prefix dfu-util with sudo
 USE_PYDFU ?= 1
 PYDFU ?= $(TOP)/tools/pydfu.py
@@ -546,7 +547,13 @@ $(PY_BUILD)/formatfloat.o: COPT += -Os
 $(PY_BUILD)/parsenum.o: COPT += -Os
 $(PY_BUILD)/mpprint.o: COPT += -Os
 
-all: $(TOP)/lib/stm32lib/README.md $(BUILD)/firmware.dfu $(BUILD)/firmware.hex
+all: $(TOP)/lib/stm32lib/README.md all_main $(BUILD)/firmware.hex
+
+ifeq ($(MBOOT_ENABLE_PACKING),1)
+all_main: $(BUILD)/firmware.pack.dfu
+else
+all_main: $(BUILD)/firmware.dfu
+endif
 
 # For convenience, automatically fetch required submodules if they don't exist
 $(TOP)/lib/stm32lib/README.md:
@@ -607,6 +614,11 @@ define GENERATE_DFU
 	$(1)
 endef
 
+define GENERATE_PACK_DFU
+	$(ECHO) "GEN $(1)"
+	$(Q)$(PYTHON) $(MBOOT_PACK_DFU) --keys $(MBOOT_PACK_KEYS_FILE) pack-dfu --gzip $(MBOOT_PACK_CHUNKSIZE) $(2) $(1)
+endef
+
 define GENERATE_HEX
 	$(ECHO) "GEN $(1)"
 	$(Q)$(OBJCOPY) -O ihex $(2) $(1)
@@ -614,8 +626,13 @@ endef
 
 .PHONY: deploy deploy-stlink deploy-openocd
 
+ifeq ($(MBOOT_ENABLE_PACKING),1)
+deploy: $(BUILD)/firmware.pack.dfu
+	$(call RUN_DFU,$^)
+else
 deploy: $(BUILD)/firmware.dfu
 	$(call RUN_DFU,$^)
+endif
 
 # A board should specify TEXT0_ADDR if to use a different location than the
 # default for the firmware memory location.  A board can also optionally define
@@ -662,6 +679,9 @@ $(BUILD)/firmware.dfu: $(BUILD)/firmware0.bin $(BUILD)/firmware1.bin
 	$(call GENERATE_DFU,$@,$(word 1,$^),$(TEXT0_ADDR),$(word 2,$^),$(TEXT1_ADDR))
 endif
 
+$(BUILD)/firmware.pack.dfu: $(BUILD)/firmware.dfu $(BOARD_DIR)/mboot_keys.h
+	$(call GENERATE_PACK_DFU,$@,$<)
+
 $(BUILD)/firmware.hex: $(BUILD)/firmware.elf
 	$(call GENERATE_HEX,$@,$^)
 

ports/stm32/mboot/Makefile

@@ -12,6 +12,12 @@ BOARD_DIR ?= $(abspath ../boards/$(BOARD))
 # that can be built with or without mboot.
 USE_MBOOT ?= 1
 
+# Set MBOOT_ENABLE_PACKING to 1 to enable DFU packing with encryption and signing.
+# Ensure the MBOOT_PACK_xxx values match stm32/Makefile, to build matching application firmware.
+MBOOT_ENABLE_PACKING ?= 0
+MBOOT_PACK_CHUNKSIZE ?= 16384
+MBOOT_PACK_KEYS_FILE ?= $(BOARD_DIR)/mboot_keys.h
+
 # Sanity check that the board configuration directory exists
 ifeq ($(wildcard $(BOARD_DIR)/.),)
 $(error Invalid BOARD specified: $(BOARD_DIR))
@@ -110,6 +116,7 @@ SRC_C = \
 	elem.c \
 	fsload.c \
 	gzstream.c \
+	pack.c \
 	vfs_fat.c \
 	vfs_lfs.c \
 	drivers/bus/softspi.c \
@@ -129,6 +136,15 @@ SRC_O = \
 	$(SYSTEM_FILE) \
 	ports/stm32/resethandler.o \
 
+ifeq ($(MBOOT_ENABLE_PACKING), 1)
+
+SRC_C += lib/libhydrogen/hydrogen.c
+
+CFLAGS += -DMBOOT_ENABLE_PACKING=1 -DPARTICLE -DPLATFORM_ID=3
+CFLAGS += -DMBOOT_PACK_CHUNKSIZE=$(MBOOT_PACK_CHUNKSIZE)
+CFLAGS += -DMBOOT_PACK_KEYS_FILE=\"$(MBOOT_PACK_KEYS_FILE)\"
+endif
+
 $(BUILD)/$(HAL_DIR)/Src/stm32$(MCU_SERIES)xx_ll_usb.o: CFLAGS += -Wno-attributes
 SRC_HAL = $(addprefix $(HAL_DIR)/Src/stm32$(MCU_SERIES)xx_,\
 	hal_cortex.c \

ports/stm32/mboot/Particle.h

+// Header for libhydrogen use only.  Act like a Particle board for the random
+// implementation.  This code is not actually called when just decrypting and
+// verifying a signature, but a correct implementation is provided anyway.
+
+#include "py/mphal.h"
+#include "rng.h"
+
+static inline uint32_t HAL_RNG_GetRandomNumber(void) {
+    return rng_get();
+}

ports/stm32/mboot/README.md

@@ -155,6 +155,34 @@ firmware.dfu.gz stored on the default FAT filesystem:
 The 0x80000000 value is the address understood by Mboot as the location of
 the external SPI flash, configured via `MBOOT_SPIFLASH_ADDR`.
 
+Signed and encrypted DFU support
+--------------------------------
+
+Mboot optionally supports signing and encrypting the binary firmware in the DFU file.
+In general this is refered to as a packed DFU file.  This requires additional settings
+in the board config and requires the `pyhy` Python module to be installed for `python3`
+to be used when building packed firmware, eg:
+
+    $ pip3 install pyhy
+
+In addition to the changes made to mpconfigboard.mk earlier, for encrypted
+support you also need to add:
+
+    MBOOT_ENABLE_PACKING = 1
+
+You will also need to generate signing and encryption keys which will be built into
+mboot and used for all subsequent installations of firmware.  This can be done via:
+
+    $ python3 ports/stm32/mboot/mboot_pack_dfu.py generate-keys
+
+This command generates a `mboot_keys.h` file which should be stored in the board
+definition folder (next to mpconfigboard.mk).
+
+Once you build the firmware, the `firmware.pack.dfu` file will contain the encrypted
+and signed firmware, and can be deployed via USB DFU, or by copying it to the device's
+internal filesystem (if `MBOOT_FSLOAD` is enabled). `firmware.dfu` is still unencrypted
+and can be directly flashed with jtag etc.
+
 Example: Mboot on PYBv1.x
 -------------------------
 

ports/stm32/mboot/dfu.h

@@ -39,6 +39,14 @@
 #define MBOOT_ERROR_STR_INVALID_ADDRESS_IDX 0x11
 #define MBOOT_ERROR_STR_INVALID_ADDRESS "Address out of range"
 
+#if MBOOT_ENABLE_PACKING
+#define MBOOT_ERROR_STR_INVALID_SIG_IDX 0x12
+#define MBOOT_ERROR_STR_INVALID_SIG "Invalid signature in file"
+
+#define MBOOT_ERROR_STR_INVALID_READ_IDX 0x13
+#define MBOOT_ERROR_STR_INVALID_READ "Read support disabled on encrypted bootloader"
+#endif
+
 // DFU class requests
 enum {
     DFU_DETACH = 0,
@@ -104,6 +112,6 @@ typedef struct _dfu_state_t {
     uint8_t buf[DFU_XFER_SIZE] __attribute__((aligned(4)));
 } dfu_context_t;
 
-static dfu_context_t dfu_context SECTION_NOZERO_BSS;
+extern dfu_context_t dfu_context;
 
 #endif // MICROPY_INCLUDED_STM32_MBOOT_DFU_H

ports/stm32/mboot/fsload.c

@@ -28,6 +28,7 @@
 
 #include "py/mphal.h"
 #include "mboot.h"
+#include "pack.h"
 #include "vfs.h"
 
 #if MBOOT_FSLOAD
@@ -36,13 +37,43 @@
 #error Must enable at least one VFS component
 #endif
 
+#if MBOOT_ENABLE_PACKING
+// Packed DFU files are gzip'd internally, not on the outside, so reads of the file
+// just read the file directly.
+
+static void *input_stream_data;
+static stream_read_t input_stream_read_meth;
+
+static inline int input_stream_init(void *stream_data, stream_read_t stream_read) {
+    input_stream_data = stream_data;
+    input_stream_read_meth = stream_read;
+    return 0;
+}
+
+static inline int input_stream_read(size_t len, uint8_t *buf) {
+    return input_stream_read_meth(input_stream_data, buf, len);
+}
+
+#else
+// Standard (non-packed) DFU files must be gzip'd externally / on the outside, so
+// reads of the file go through gz_stream.
+
+static inline int input_stream_init(void *stream_data, stream_read_t stream_read) {
+    return gz_stream_init_from_stream(stream_data, stream_read);
+}
+
+static inline int input_stream_read(size_t len, uint8_t *buf) {
+    return gz_stream_read(len, buf);
+}
+#endif
+
 static int fsload_program_file(bool write_to_flash) {
     // Parse DFU
     uint8_t buf[512];
     size_t file_offset;
 
     // Read file header, <5sBIB
-    int res = gz_stream_read(11, buf);
+    int res = input_stream_read(11, buf);
     if (res != 11) {
         return -1;
     }
@@ -62,7 +93,7 @@ static int fsload_program_file(bool write_to_flash) {
     uint32_t total_size = get_le32(buf + 6);
 
     // Read target header, <6sBi255sII
-    res = gz_stream_read(274, buf);
+    res = input_stream_read(274, buf);
     if (res != 274) {
         return -1;
     }
@@ -82,7 +113,7 @@ static int fsload_program_file(bool write_to_flash) {
     // Parse each element
     for (size_t elem = 0; elem < num_elems; ++elem) {
         // Read element header, <II
-        res = gz_stream_read(8, buf);
+        res = input_stream_read(8, buf);
         if (res != 8) {
             return -1;
         }
@@ -92,6 +123,7 @@ static int fsload_program_file(bool write_to_flash) {
         uint32_t elem_addr = get_le32(buf);
         uint32_t elem_size = get_le32(buf + 4);
 
+        #if !MBOOT_ENABLE_PACKING
         // Erase flash before writing
         if (write_to_flash) {
             uint32_t addr = elem_addr;
@@ -102,6 +134,7 @@ static int fsload_program_file(bool write_to_flash) {
                 }
             }
         }
+        #endif
 
         // Read element data and possibly write to flash
         for (uint32_t s = elem_size; s;) {
@@ -109,7 +142,7 @@ static int fsload_program_file(bool write_to_flash) {
             if (l > sizeof(buf)) {
                 l = sizeof(buf);
             }
-            res = gz_stream_read(l, buf);
+            res = input_stream_read(l, buf);
             if (res != l) {
                 return -1;
             }
@@ -135,7 +168,7 @@ static int fsload_program_file(bool write_to_flash) {
     }
 
     // Read trailing info
-    res = gz_stream_read(16, buf);
+    res = input_stream_read(16, buf);
     if (res != 16) {
         return -1;
     }
@@ -151,7 +184,7 @@ static int fsload_validate_and_program_file(void *stream, const stream_methods_t
         led_state_all(pass == 0 ? 2 : 4);
         int res = meth->open(stream, fname);
         if (res == 0) {
-            res = gz_stream_init(stream, meth->read);
+            res = input_stream_init(stream, meth->read);
             if (res == 0) {
                 res = fsload_program_file(pass == 0 ? false : true);
             }

ports/stm32/mboot/fwupdate.py

@@ -157,14 +157,15 @@ def update_mboot(filename):
 
 
 def update_mpy(filename, fs_base, fs_len, fs_type=VFS_FAT):
-    # Check firmware is of .dfu.gz type
+    # Check firmware is of .dfu or .dfu.gz type
     try:
         with open(filename, "rb") as f:
             hdr = uzlib.DecompIO(f, 16 + 15).read(6)
     except Exception:
-        hdr = None
+        with open(filename, "rb") as f:
+            hdr = f.read(6)
     if hdr != b"DfuSe\x01":
-        print("Firmware must be a .dfu.gz file.")
+        print("Firmware must be a .dfu(.gz) file.")
         return
 
     ELEM_TYPE_END = 1

ports/stm32/mboot/gzstream.c

@@ -31,7 +31,7 @@
 #include "gzstream.h"
 #include "mboot.h"
 
-#if MBOOT_FSLOAD
+#if MBOOT_FSLOAD || MBOOT_ENABLE_PACKING
 
 #define DICT_SIZE (1 << 15)
 
@@ -61,7 +61,17 @@ static int gz_stream_read_src(TINF_DATA *tinf) {
     return gz_stream.buf[0];
 }
 
-int gz_stream_init(void *stream_data, stream_read_t stream_read) {
+int gz_stream_init_from_raw_data(const uint8_t *data, size_t len) {
+    memset(&gz_stream.tinf, 0, sizeof(gz_stream.tinf));
+    gz_stream.tinf.source = data;
+    gz_stream.tinf.source_limit = data + len;
+
+    uzlib_uncompress_init(&gz_stream.tinf, gz_stream.dict, DICT_SIZE);
+
+    return 0;
+}
+
+int gz_stream_init_from_stream(void *stream_data, stream_read_t stream_read) {
     gz_stream.stream_data = stream_data;
     gz_stream.stream_read = stream_read;
 
@@ -97,4 +107,4 @@ int gz_stream_read(size_t len, uint8_t *buf) {
     return gz_stream.tinf.dest - buf;
 }
 
-#endif // MBOOT_FSLOAD
+#endif // MBOOT_FSLOAD || MBOOT_ENABLE_PACKING

ports/stm32/mboot/gzstream.h

@@ -39,7 +39,8 @@ typedef struct _stream_methods_t {
     stream_read_t read;
 } stream_methods_t;
 
-int gz_stream_init(void *stream_data, stream_read_t stream_read);
+int gz_stream_init_from_raw_data(const uint8_t *data, size_t len);
+int gz_stream_init_from_stream(void *stream_data, stream_read_t stream_read);
 int gz_stream_read(size_t len, uint8_t *buf);
 
 #endif // MICROPY_INCLUDED_STM32_MBOOT_GZSTREAM_H

ports/stm32/mboot/main.c

@@ -37,6 +37,7 @@
 #include "mboot.h"
 #include "powerctrl.h"
 #include "dfu.h"
+#include "pack.h"
 
 // This option selects whether to use explicit polling or IRQs for USB events.
 // In some test cases polling mode can run slightly faster, but it uses more power.
@@ -56,11 +57,17 @@
 // Configure PLL to give the desired CPU freq
 #undef MICROPY_HW_FLASH_LATENCY
 #if defined(STM32F4) || defined(STM32F7)
-#define CORE_PLL_FREQ (48000000)
-#define MICROPY_HW_FLASH_LATENCY FLASH_LATENCY_1
+  #if MBOOT_ENABLE_PACKING
+    // With encryption/signing/compression, a faster CPU makes processing much faster.
+    #define CORE_PLL_FREQ (96000000)
+    #define MICROPY_HW_FLASH_LATENCY FLASH_LATENCY_3
+  #else
+    #define CORE_PLL_FREQ (48000000)
+    #define MICROPY_HW_FLASH_LATENCY FLASH_LATENCY_1
+  #endif
 #elif defined(STM32H7)
-#define CORE_PLL_FREQ (96000000)
-#define MICROPY_HW_FLASH_LATENCY FLASH_LATENCY_2
+  #define CORE_PLL_FREQ (96000000)
+  #define MICROPY_HW_FLASH_LATENCY FLASH_LATENCY_2
 #endif
 #undef MICROPY_HW_CLK_PLLM
 #undef MICROPY_HW_CLK_PLLN
@@ -87,7 +94,8 @@
 // These bits are used to detect valid application firmware at APPLICATION_ADDR
 #define APP_VALIDITY_BITS (0x00000003)
 
-#define MP_ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
+// Global dfu state
+dfu_context_t dfu_context SECTION_NOZERO_BSS;
 
 static void do_reset(void);
 
@@ -140,7 +148,7 @@ void HAL_Delay(uint32_t ms) {
     mp_hal_delay_ms(ms);
 }
 
-static void __fatal_error(const char *msg) {
+NORETURN static void __fatal_error(const char *msg) {
     NVIC_SystemReset();
     for (;;) {
     }
@@ -547,7 +555,7 @@ static int spiflash_page_erase(mp_spiflash_t *spif, uint32_t addr, uint32_t n_bl
 }
 #endif
 
-int do_page_erase(uint32_t addr, uint32_t *next_addr) {
+int hw_page_erase(uint32_t addr, uint32_t *next_addr) {
     int ret = -1;
     led0_state(LED0_STATE_ON);
 
@@ -573,7 +581,7 @@ int do_page_erase(uint32_t addr, uint32_t *next_addr) {
     return ret;
 }
 
-void do_read(uint32_t addr, int len, uint8_t *buf) {
+void hw_read(uint32_t addr, int len, uint8_t *buf) {
     led0_state(LED0_STATE_FAST_FLASH);
     #if defined(MBOOT_SPIFLASH_ADDR)
     if (MBOOT_SPIFLASH_ADDR <= addr && addr < MBOOT_SPIFLASH_ADDR + MBOOT_SPIFLASH_BYTE_SIZE) {
@@ -592,7 +600,7 @@ void do_read(uint32_t addr, int len, uint8_t *buf) {
     led0_state(LED0_STATE_SLOW_FLASH);
 }
 
-int do_write(uint32_t addr, const uint8_t *src8, size_t len) {
+int hw_write(uint32_t addr, const uint8_t *src8, size_t len) {
     int ret = -1;
     led0_state(LED0_STATE_FAST_FLASH);
     #if defined(MBOOT_SPIFLASH_ADDR)
@@ -616,6 +624,34 @@ int do_write(uint32_t addr, const uint8_t *src8, size_t len) {
     return ret;
 }
 
+int do_page_erase(uint32_t addr, uint32_t *next_addr) {
+    #if MBOOT_ENABLE_PACKING
+    // Erase handled automatically for packed mode.
+    return 0;
+    #else
+    return hw_page_erase(addr, next_addr);
+    #endif
+}
+
+void do_read(uint32_t addr, int len, uint8_t *buf) {
+    #if MBOOT_ENABLE_PACKING
+    // Read disabled on packed (encrypted) mode.
+    dfu_context.status = DFU_STATUS_ERROR_FILE;
+    dfu_context.error = MBOOT_ERROR_STR_INVALID_READ_IDX;
+    led0_state(LED0_STATE_SLOW_INVERTED_FLASH);
+    #else
+    hw_read(addr, len, buf);
+    #endif
+}
+
+int do_write(uint32_t addr, const uint8_t *src8, size_t len) {
+    #if MBOOT_ENABLE_PACKING
+    return mboot_pack_write(addr, src8, len);
+    #else
+    return hw_write(addr, src8, len);
+    #endif
+}
+
 /******************************************************************************/
 // I2C slave interface
 
@@ -1068,6 +1104,16 @@ static uint8_t *pyb_usbdd_StrDescriptor(USBD_HandleTypeDef *pdev, uint8_t idx, u
             USBD_GetString((uint8_t*)MBOOT_ERROR_STR_INVALID_ADDRESS, str_desc, length);
             return str_desc;
 
+        #if MBOOT_ENABLE_PACKING
+        case MBOOT_ERROR_STR_INVALID_SIG_IDX:
+            USBD_GetString((uint8_t*)MBOOT_ERROR_STR_INVALID_SIG, str_desc, length);
+            return str_desc;
+
+        case MBOOT_ERROR_STR_INVALID_READ_IDX:
+            USBD_GetString((uint8_t*)MBOOT_ERROR_STR_INVALID_READ, str_desc, length);
+            return str_desc;
+        #endif
+
         default:
             return NULL;
     }
@@ -1388,6 +1434,10 @@ enter_bootloader:
     mp_spiflash_init(MBOOT_SPIFLASH2_SPIFLASH);
     #endif
 
+    #if MBOOT_ENABLE_PACKING
+    mboot_pack_init();
+    #endif
+
     #if MBOOT_FSLOAD
     if ((initial_r0 & 0xffffff80) == 0x70ad0080) {
         // Application passed through elements, validate then process them

ports/stm32/mboot/mboot.h

@@ -36,6 +36,9 @@
 #define ELEM_DATA_START (&_estack[0])
 #define ELEM_DATA_MAX (&_estack[ELEM_DATA_SIZE])
 
+#define NORETURN __attribute__((noreturn))
+#define MP_ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
+
 enum {
     ELEM_TYPE_END = 1,
     ELEM_TYPE_MOUNT,
@@ -53,6 +56,10 @@ extern uint8_t _estack[ELEM_DATA_SIZE];
 uint32_t get_le32(const uint8_t *b);
 void led_state_all(unsigned int mask);
 
+int hw_page_erase(uint32_t addr, uint32_t *next_addr);
+void hw_read(uint32_t addr, int len, uint8_t *buf);
+int hw_write(uint32_t addr, const uint8_t *src8, size_t len);
+
 int do_page_erase(uint32_t addr, uint32_t *next_addr);
 void do_read(uint32_t addr, int len, uint8_t *buf);
 int do_write(uint32_t addr, const uint8_t *src8, size_t len);

ports/stm32/mboot/mboot_pack_dfu.py

+# This file is part of the MicroPython project, http://micropython.org/
+#
+# The MIT License (MIT)
+#
+# Copyright (c) 2020-2021 Damien P. George
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+"""
+Utility to create compressed, encrypted and signed DFU files.
+"""
+
+import argparse
+import os
+import re
+import struct
+import sys
+import zlib
+
+sys.path.append(os.path.dirname(__file__) + "/../../../tools")
+import dfu
+
+try:
+    import pyhy
+except ImportError:
+    raise SystemExit(
+        "ERROR: pyhy not found. Please install python pyhy for encrypted mboot support: pip3 install pyhy"
+    )
+
+
+# Currenty supported version of a packed DFU file.
+MBOOT_PACK_HEADER_VERSION = 1
+
+# Must match MBOOT_PACK_HYDRO_CONTEXT in mboot/pack.h
+MBOOT_PACK_HYDRO_CONTEXT = "mbootenc"
+
+# Must match enum in mboot/pack.h.
+MBOOT_PACK_CHUNK_META = 0
+MBOOT_PACK_CHUNK_FULL_SIG = 1
+MBOOT_PACK_CHUNK_FW_RAW = 2
+MBOOT_PACK_CHUNK_FW_GZIP = 3
+
+
+class Keys:
+    def __init__(self, filename):
+        self.filename = filename
+
+    def generate(self):
+        kp = pyhy.hydro_sign_keygen()
+        self.sign_sk = kp.sk
+        self.sign_pk = kp.pk
+        self.secretbox = pyhy.hydro_secretbox_keygen()
+
+    def _save_data(self, name, data, file_, hide=False):
+        prefix = "//" if hide else ""
+        data = ",".join("0x{:02x}".format(b) for b in data)
+        file_.write("{}const uint8_t {}[] = {{{}}};\n".format(prefix, name, data))
+
+    def _load_data(self, name, line):
+        line = line.split(name + "[] = ")
+        if len(line) != 2:
+            raise Exception("malformed input keys: {}".format(line))
+        data = line[1].strip()
+        return bytes(int(value, 16) for value in data[1:-2].split(","))
+
+    def save(self):
+        with open(self.filename, "w") as f:
+            self._save_data("mboot_pack_sign_secret_key", self.sign_sk, f, hide=True)
+            self._save_data("mboot_pack_sign_public_key", self.sign_pk, f)
+            self._save_data("mboot_pack_secretbox_key", self.secretbox, f)
+
+    def load(self):
+        with open(self.filename) as f:
+            self.sign_sk = self._load_data("mboot_pack_sign_secret_key", f.readline())
+            self.sign_pk = self._load_data("mboot_pack_sign_public_key", f.readline())
+            self.secretbox = self._load_data("mboot_pack_secretbox_key", f.readline())
+
+
+def dfu_read(filename):
+    elems = []
+
+    with open(filename, "rb") as f:
+        hdr = f.read(11)
+        sig, ver, size, num_targ = struct.unpack("<5sBIB", hdr)
+        file_offset = 11
+
+        for i in range(num_targ):
+            hdr = f.read(274)
+            sig, alt, has_name, name, t_size, num_elem = struct.unpack("<6sBi255sII", hdr)
+
+            file_offset += 274
+            file_offset_t = file_offset
+            for j in range(num_elem):
+                hdr = f.read(8)
+                addr, e_size = struct.unpack("<II", hdr)
+                data = f.read(e_size)
+                elems.append((addr, data))
+                file_offset += 8 + e_size
+
+            if t_size != file_offset - file_offset_t:
+                raise Exception("corrupt DFU {} {}".format(t_size, file_offset - file_offset_t))
+
+        if size != file_offset:
+            raise Exception("corrupt DFU {} {}".format(size, file_offset))
+
+        hdr = f.read(16)
+        hdr = struct.unpack("<HHHH3sBI", hdr)
+        vid_pid = "0x{:04x}:0x{:04x}".format(hdr[2], hdr[1])
+
+    return vid_pid, elems
+
+
+def compress(data):
+    c = zlib.compressobj(level=9, memLevel=9, wbits=-15)  # wsize=15, no header
+    return c.compress(data) + c.flush()
+
+
+def encrypt(keys, data):
+    return pyhy.hydro_secretbox_encrypt(data, 0, MBOOT_PACK_HYDRO_CONTEXT, keys.secretbox)
+
+
+def sign(keys, data):
+    return pyhy.hydro_sign_create(data, MBOOT_PACK_HYDRO_CONTEXT, keys.sign_sk)
+
+
+def pack_chunk(keys, format_, chunk_addr, chunk_payload):
+    header = struct.pack(
+        "<BBBBII", MBOOT_PACK_HEADER_VERSION, format_, 0, 0, chunk_addr, len(chunk_payload)
+    )
+    chunk = header + chunk_payload
+    sig = sign(keys, chunk)
+    chunk = chunk + sig
+    return chunk
+
+
+def data_chunks(data, n):
+    for i in range(0, len(data), n):
+        yield data[i : i + n]
+
+
+def generate_keys(keys, args):
+    keys.generate()
+    keys.save()
+
+
+def pack_dfu(keys, args):
+    chunk_size = int(args.chunk_size[0])
+
+    # Load previously generated keys.
+    keys.load()
+
+    # Read the input DFU file.
+    vid_pid, elems = dfu_read(args.infile[0])
+
+    # Ensure firmware sections are processed in order of destination memory address.
+    elems = sorted(elems, key=lambda e: e[0])
+
+    # Build list of packed chunks.
+    target = []
+    full_fw = b""
+    full_signature_payload = b""
+    for address, fw in elems:
+        # Update full firmware and full signature chunk.
+        full_fw += fw
+        full_signature_payload += struct.pack("<II", address, len(fw))
+
+        # Split the firmware into chunks, encrypt and sign the chunks
+        # then register them as individual DFU targets.
+        for i, chunk in enumerate(data_chunks(fw, chunk_size)):
+            chunk_addr = address + i * chunk_size
+            if args.gzip:
+                chunk = compress(chunk)
+            chunk = encrypt(keys, chunk)
+            chunk = pack_chunk(
+                keys,
+                MBOOT_PACK_CHUNK_FW_GZIP if args.gzip else MBOOT_PACK_CHUNK_FW_RAW,
+                chunk_addr,
+                chunk,
+            )
+            target.append({"address": chunk_addr, "data": chunk})
+
+    # Add full signature to targets, at location following the last chunk.
+    chunk_addr += chunk_size
+    sig = sign(keys, full_fw)
+    full_signature_payload += sig
+    full_signature_chunk = pack_chunk(
+        keys, MBOOT_PACK_CHUNK_FULL_SIG, chunk_addr, full_signature_payload
+    )
+    target.append({"address": chunk_addr, "data": full_signature_chunk})
+
+    # Build the packed DFU file of all the encrypted and signed chunks.
+    dfu.build(args.outfile[0], [target], vid_pid)
+
+    # Verify the packed DFU file.
+    verify_pack_dfu(keys, args.outfile[0])
+
+
+def verify_pack_dfu(keys, filename):
+    full_sig = pyhy.hydro_sign(MBOOT_PACK_HYDRO_CONTEXT)
+    _, elems = dfu_read(filename)
+    for addr, data in elems:
+        header = struct.unpack("<BBBBII", data[:12])
+        chunk = data[12 : 12 + header[5]]
+        sig = data[12 + header[5] :]
+        sig_pass = pyhy.hydro_sign_verify(
+            sig, data[:12] + chunk, MBOOT_PACK_HYDRO_CONTEXT, keys.sign_pk
+        )
+        assert sig_pass
+        if header[1] == MBOOT_PACK_CHUNK_FULL_SIG:
+            actual_sig = chunk[-64:]
+        else:
+            chunk = pyhy.hydro_secretbox_decrypt(
+                chunk, 0, MBOOT_PACK_HYDRO_CONTEXT, keys.secretbox
+            )
+            assert chunk is not None
+            if header[1] == MBOOT_PACK_CHUNK_FW_GZIP:
+                chunk = zlib.decompress(chunk, wbits=-15)
+            full_sig.update(chunk)
+    full_sig_pass = full_sig.final_verify(actual_sig, keys.sign_pk)
+    assert full_sig_pass
+
+
+def main():
+    cmd_parser = argparse.ArgumentParser(description="Build signed/encrypted DFU files")
+    cmd_parser.add_argument("-k", "--keys", default="mboot_keys.h", help="filename for keys")
+    subparsers = cmd_parser.add_subparsers()
+
+    parser_gk = subparsers.add_parser("generate-keys", help="generate keys")
+    parser_gk.set_defaults(func=generate_keys)
+
+    parser_ed = subparsers.add_parser("pack-dfu", help="encrypt and sign a DFU file")
+    parser_ed.add_argument("-z", "--gzip", action="store_true", help="compress chunks")
+    parser_ed.add_argument("chunk_size", nargs=1, help="maximum size in bytes of each chunk")
+    parser_ed.add_argument("infile", nargs=1, help="input DFU file")
+    parser_ed.add_argument("outfile", nargs=1, help="output DFU file")
+    parser_ed.set_defaults(func=pack_dfu)
+
+    args = cmd_parser.parse_args()
+
+    keys = Keys(args.keys)
+    args.func(keys, args)
+
+
+if __name__ == "__main__":
+    main()

ports/stm32/mboot/pack.h

+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017-2019 Damien P. George
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+#ifndef MICROPY_INCLUDED_STM32_MBOOT_PACK_H
+#define MICROPY_INCLUDED_STM32_MBOOT_PACK_H
+
+#include <stdint.h>
+#include "py/mphal.h"
+
+#if MBOOT_ENABLE_PACKING
+
+#include "lib/libhydrogen/hydrogen.h"
+
+// Encrypted & signed bootloader support
+
+/******************************************************************************/
+// Interface
+
+#define MBOOT_PACK_HEADER_VERSION (1)
+
+// Used by libhydrogen for signing and secretbox context.
+#define MBOOT_PACK_HYDRO_CONTEXT "mbootenc"
+
+// Maximum size of the firmware payload.
+#define MBOOT_PACK_DFU_CHUNK_BUF_SIZE (MBOOT_PACK_CHUNKSIZE + hydro_secretbox_HEADERBYTES)
+
+enum mboot_pack_chunk_format {
+    MBOOT_PACK_CHUNK_META = 0,
+    MBOOT_PACK_CHUNK_FULL_SIG = 1,
+    MBOOT_PACK_CHUNK_FW_RAW = 2,
+    MBOOT_PACK_CHUNK_FW_GZIP = 3,
+};
+
+// Each DFU chunk transfered has this header to validate it.
+
+typedef struct _mboot_pack_chunk_buf_t {
+    struct {
+        uint8_t header_vers;
+        uint8_t format;  // enum mboot_pack_chunk_format
+        uint8_t _pad[2];
+        uint32_t address;
+        uint32_t length; // number of bytes in following "data" payload, excluding "signature"
+    } header;
+    uint8_t data[MBOOT_PACK_DFU_CHUNK_BUF_SIZE];
+    uint8_t signature[hydro_sign_BYTES];
+} mboot_pack_chunk_buf_t;
+
+// Signing and encryption keys, stored in mboot flash, provided externally.
+extern const uint8_t mboot_pack_sign_public_key[hydro_sign_PUBLICKEYBYTES];
+extern const uint8_t mboot_pack_secretbox_key[hydro_secretbox_KEYBYTES];
+
+/******************************************************************************/
+// Implementation
+
+void mboot_pack_init(void);
+int mboot_pack_write(uint32_t addr, const uint8_t *src8, size_t len);
+
+#endif // MBOOT_ENABLE_PACKING
+
+#endif // MICROPY_INCLUDED_STM32_MBOOT_PACK_H

ports/stm32/mboot/stm32_generic.ld

@@ -6,11 +6,11 @@
 MEMORY
 {
     FLASH_BL (rx)   : ORIGIN = 0x08000000, LENGTH = 32K /* sector 0 (can be 32K) */
-    RAM (xrw)       : ORIGIN = 0x20000000, LENGTH = 96K
+    RAM (xrw)       : ORIGIN = 0x20000000, LENGTH = 120K
 }
 
 /* produce a link error if there is not this amount of RAM for these sections */
-_minimum_stack_size = 2K;
+_minimum_stack_size = 8K;
 
 /* Define tho top end of the stack.  The stack is full descending so begins just
    above last byte of RAM.  Note that EABI requires the stack to be 8-byte

ports/stm32/mboot/vfs_fat.c

@@ -42,7 +42,7 @@ DRESULT disk_read(void *pdrv, BYTE *buf, DWORD sector, UINT count) {
     vfs_fat_context_t *ctx = pdrv;
 
     if (0 <= sector && sector < ctx->bdev_byte_len / 512) {
-        do_read(ctx->bdev_base_addr + sector * SECSIZE, count * SECSIZE, buf);
+        hw_read(ctx->bdev_base_addr + sector * SECSIZE, count * SECSIZE, buf);
         return RES_OK;
     }
 

ports/stm32/mboot/vfs_lfs.c

@@ -72,7 +72,7 @@ static uint8_t lfs_lookahead_buffer[LFS_LOOKAHEAD_SIZE];
 static int dev_read(const struct LFSx_API (config) * c, LFSx_API(block_t) block, LFSx_API(off_t) off, void *buffer, LFSx_API(size_t) size) {
     VFS_LFSx_CONTEXT_T *ctx = c->context;
     if (0 <= block && block < ctx->config.block_count) {
-        do_read(ctx->bdev_base_addr + block * ctx->config.block_size + off, size, buffer);
+        hw_read(ctx->bdev_base_addr + block * ctx->config.block_size + off, size, buffer);
         return LFSx_MACRO(_ERR_OK);
     }
     return LFSx_MACRO(_ERR_IO);
@@ -93,7 +93,7 @@ static int dev_sync(const struct LFSx_API (config) * c) {
 int VFS_LFSx_MOUNT(VFS_LFSx_CONTEXT_T *ctx, uint32_t base_addr, uint32_t byte_len) {
     // Read start of superblock.
     uint8_t buf[48];
-    do_read(base_addr, sizeof(buf), buf);
+    hw_read(base_addr, sizeof(buf), buf);
 
     // Verify littlefs and detect block size.
     if (memcmp(&buf[SUPERBLOCK_MAGIC_OFFSET], "littlefs", 8) != 0) {

ports/stm32/mpconfigport.mk

-# Enable/disable extra modules
+# Enable/disable extra modules and features
 
 # wiznet5k module for ethernet support; valid values are:
 #   0    : no Wiznet support
@@ -11,3 +11,8 @@ MICROPY_PY_CC3K ?= 0
 
 # VFS FAT FS support
 MICROPY_VFS_FAT ?= 1
+
+# Encrypted/signed bootloader support (ensure the MBOOT_PACK_xxx values match stm32/mboot/Makefile)
+MBOOT_ENABLE_PACKING ?= 0
+MBOOT_PACK_CHUNKSIZE ?= 16384
+MBOOT_PACK_KEYS_FILE ?= $(BOARD_DIR)/mboot_keys.h