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Improve on bootloader security when Security Bit is set #592

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Improve on bootloader security when Security Bit is set #592

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277a965
When Secure Bit is set: Prevent tries of partial flashing using Write…
ksmith3036 Jan 3, 2021
ae22762
Combine full version information into one const string in source code…
ksmith3036 Jan 3, 2021
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56 changes: 45 additions & 11 deletions bootloaders/zero/sam_ba_monitor.c
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Original file line number Diff line number Diff line change
Expand Up @@ -29,9 +29,9 @@
#include "board_driver_led.h"
#include <stdlib.h>

const char RomBOOT_Version[] = SAM_BA_VERSION;
// X = Chip Erase, Y = Write Buffer, Z = Checksum Buffer, P = Secure Bit Aware
const char RomBOOT_ExtendedCapabilities[] = "[Arduino:XYZP]";
#define ROMBOOT_EXTENDEDCAPABILITIES "[Arduino:XYZP]"
const char ROMBoot_VersionInformation[] = "v" SAM_BA_VERSION " " ROMBOOT_EXTENDEDCAPABILITIES " " __DATE__ " " __TIME__ "\n\r";

/* Provides one common interface to handle both USART and USB-CDC */
typedef struct
Expand Down Expand Up @@ -362,15 +362,54 @@ static void sam_ba_monitor_loop(void)
}
else if (command == 'O') // write byte
{
*ptr_data = (char) current_number;
if (b_security_enabled && (uint16_t *)ptr_data == &NVMCTRL->CTRLA.reg && (current_number & NVMCTRL_CTRLA_CMD_Msk) == NVMCTRL_CTRLA_CMD_ER)
{
// NVM Erase Row command received in secure mode.
// To mitigate that an attacker might not use the ordinary BOSSA method of erasing flash before programming,
// always erase flash, if it hasn't been done already.
if (erased_from != 0x2000)
{
eraseFlash(0x2000);
}
}
else
{
*ptr_data = (char) current_number;
}
}
else if (command == 'H') // Write half word
{
*((uint16_t *) ptr_data) = (uint16_t) current_number;
if (b_security_enabled && (uint16_t *)ptr_data == &NVMCTRL->CTRLA.reg && (current_number & NVMCTRL_CTRLA_CMD_Msk) == NVMCTRL_CTRLA_CMD_ER)
{
// NVM Erase Row command received in secure mode.
// To mitigate that an attacker might not use the ordinary BOSSA method of erasing flash before programming,
// always erase flash, if it hasn't been done already.
if (erased_from != 0x2000)
{
eraseFlash(0x2000);
}
}
else
{
*((uint16_t *) ptr_data) = (uint16_t) current_number;
}
}
else if (command == 'W') // Write word
{
*((int *) ptr_data) = current_number;
if (b_security_enabled && (uint16_t *)ptr_data == &NVMCTRL->CTRLA.reg && (current_number & NVMCTRL_CTRLA_CMD_Msk) == NVMCTRL_CTRLA_CMD_ER)
{
// NVM Erase Row command received in secure mode.
// To mitigate that an attacker might not use the ordinary BOSSA method of erasing flash before programming,
// always erase flash, if it hasn't been done already.
if (erased_from != 0x2000)
{
eraseFlash(0x2000);
}
}
else
{
*((int *) ptr_data) = current_number;
}
}
else if (command == 'o') // Read byte
{
Expand Down Expand Up @@ -446,12 +485,7 @@ static void sam_ba_monitor_loop(void)
}
else if (command == 'V') // Read version information
{
sam_ba_putdata( ptr_monitor_if, "v", 1);
sam_ba_putdata( ptr_monitor_if, (uint8_t *) RomBOOT_Version, strlen(RomBOOT_Version));
sam_ba_putdata( ptr_monitor_if, " ", 1);
sam_ba_putdata( ptr_monitor_if, (uint8_t *) RomBOOT_ExtendedCapabilities, strlen(RomBOOT_ExtendedCapabilities));
ptr = (uint8_t*) &(" " __DATE__ " " __TIME__ "\n\r");
sam_ba_putdata( ptr_monitor_if, ptr, strlen(ptr));
sam_ba_putdata( ptr_monitor_if, ROMBoot_VersionInformation, sizeof(ROMBoot_VersionInformation) - 1);
}
else if (command == 'X') // Erase flash
{
Expand Down