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sept: elide context save for safety.

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This commit is contained in:
Michael Scire 2019-06-19 00:20:42 -07:00
parent 11d8021435
commit 6829572556
1 changed files with 7 additions and 53 deletions
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60
sept/sept-secondary/key_derivation/src/key_derivation.c
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@ -58,68 +58,24 @@ void derive_keys(void) {
const uint32_t derivation_id = *((volatile uint32_t *)0x4003E800);
if (derivation_id < DERIVATION_ID_MAX) {
uint8_t *partial_se_state = (uint8_t *)0x4000FFC0;
uint8_t *enc_se_state = (uint8_t *)0x4003E000;
volatile tegra_pmc_t *pmc = pmc_get_regs();
uint32_t AL16 work_buffer[4];
/* Save a partial context, only the keyslots we want. */
/* We can't avoid touching memory, but save to a location that the bootrom will overwrite during init. */
se_set_in_context_save_mode(true);
se_save_partial_context(KEYSLOT_SWITCH_SRKGENKEY, KEYSLOT_SWITCH_RNGKEY, partial_se_state);
se_set_in_context_save_mode(false);
/* Clear the copy of the root key still inside the SE. */
clear_aes_keyslot(0xD);
/* Copy SRK into keyslot 0xE, clear it. */
{
work_buffer[0] = pmc->secure_scratch4;
pmc->secure_scratch4 = 0xCCCCCCCC;
work_buffer[1] = pmc->secure_scratch5;
pmc->secure_scratch5 = 0xCCCCCCCC;
work_buffer[2] = pmc->secure_scratch6;
pmc->secure_scratch6 = 0xCCCCCCCC;
work_buffer[3] = pmc->secure_scratch7;
pmc->secure_scratch7 = 0xCCCCCCCC;
set_aes_keyslot(0xE, work_buffer, 0x10);
for (size_t i = 0; i < 4; i++) {
work_buffer[i] = 0xCCCCCCCC;
}
}
/* Decrypt SE state. */
se_aes_128_cbc_decrypt(0xE, partial_se_state, 0x40, partial_se_state, 0x40);
/* Clear keyslots to wipe IVs. */
clear_aes_keyslot(0xE);
clear_aes_keyslot(0xF);
/* Mov root key into keyslot 0xE. */
set_aes_keyslot(0xE, partial_se_state + 0x30, 0x10);
for (size_t i = 0; i < 4; i++) {
*((volatile uint32_t *)(partial_se_state + 0x30)) = 0xCCCCCCCC;
}
/* Derive Keyblob Key 00. */
se_aes_ecb_decrypt_block(0xC, work_buffer, 0x10, keyblob_seed_00, 0x10);
decrypt_data_into_keyslot(0xF, 0xE, work_buffer, 0x10);
/* Derive master kek. */
decrypt_data_into_keyslot(0xE, 0xE, master_kek_seeds[derivation_id], 0x10);
decrypt_data_into_keyslot(0xE, 0xD, master_kek_seeds[derivation_id], 0x10);
/* Clear the copy of the root key inside the SE. */
clear_aes_keyslot(0xD);
/* Derive master key, device master key. */
decrypt_data_into_keyslot(0xC, 0xE, masterkey_seed, 0x10);
decrypt_data_into_keyslot(0xE, 0xE, masterkey_4x_seed, 0x10);
/* Derive Keyblob Key 00. */
set_aes_keyslot(0xF, partial_se_state + 0x20, 0x10);
se_aes_ecb_decrypt_block(0xF, work_buffer, 0x10, keyblob_seed_00, 0x10);
set_aes_keyslot(0xF, partial_se_state + 0x10, 0x10);
decrypt_data_into_keyslot(0xF, 0xF, work_buffer, 0x10);
/* Clear TSEC key + SBK. */
for (size_t i = 0; i < 8; i++) {
*((volatile uint32_t *)(partial_se_state + 0x10)) = 0xCCCCCCCC;
}
/* Derive device keys. */
decrypt_data_into_keyslot(0xA, 0xF, devicekey_4x_seed, 0x10);
decrypt_data_into_keyslot(0xF, 0xF, devicekey_seed, 0x10);
@ -144,8 +100,6 @@ void derive_keys(void) {
clear_aes_keyslot(i);
}
*(volatile uint32_t *)(0x4003FFC0) = 0xCACACACA;
*mailbox = 7;
while (1) { /* Wait for sept to handle the rest. */ }
}