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AP_CheckFirmware: allow for boot if no public keys 

this will allow for SECURE_UPDATE command to unlock bootloader
This commit is contained in:
Andrew Tridgell 2022-09-02 12:25:57 +10:00
parent ae55d7d902
commit 029947efc7
1 changed files with 18 additions and 2 deletions
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20
libraries/AP_CheckFirmware/AP_CheckFirmware.cpp
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@ -14,11 +14,14 @@
#include <string.h>
#include "monocypher.h"
#define AP_PUBLIC_KEY_LEN 32
#define AP_PUBLIC_KEY_MAX_KEYS 10
struct PACKED secure_data {
uint8_t sig[8] = {0x4e, 0xcf, 0x4e, 0xa5, 0xa6, 0xb6, 0xf7, 0x29};
struct PACKED {
uint8_t key[32] = {};
} public_key[10];
uint8_t key[AP_PUBLIC_KEY_LEN] = {};
} public_key[AP_PUBLIC_KEY_MAX_KEYS];
};
const struct secure_data public_keys __attribute__((section(".ecc_raw")));
@ -32,6 +35,7 @@ static check_fw_result_t check_firmware_signature(const app_descriptor *ad,
{
// 8 byte signature version
static const uint64_t sig_version = 30437LLU;
const uint8_t zero_key[AP_PUBLIC_KEY_LEN] {};
if (ad->signature_length != 72) {
return check_fw_result_t::FAIL_REASON_BAD_FIRMWARE_SIGNATURE;
@ -40,10 +44,16 @@ static check_fw_result_t check_firmware_signature(const app_descriptor *ad,
return check_fw_result_t::FAIL_REASON_BAD_FIRMWARE_SIGNATURE;
}
bool all_zero_keys = true;
/*
look over all public keys, if one matches then we are OK
*/
for (const auto &public_key : public_keys.public_key) {
if (memcmp(public_key.key, zero_key, AP_PUBLIC_KEY_LEN) == 0) {
continue;
}
all_zero_keys = false;
crypto_check_ctx ctx {};
crypto_check_ctx_abstract *actx = (crypto_check_ctx_abstract*)&ctx;
crypto_check_init(actx, &ad->signature[sizeof(sig_version)], public_key.key);
@ -55,6 +65,12 @@ static check_fw_result_t check_firmware_signature(const app_descriptor *ad,
return check_fw_result_t::CHECK_FW_OK;
}
}
if (all_zero_keys) {
// bootloader is unlocked if it has no public keys
return check_fw_result_t::CHECK_FW_OK;
}
// none of the public keys matched
return check_fw_result_t::FAIL_REASON_VERIFICATION;
}