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warmboot: add code for decrypting/restoring tzram.

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This commit is contained in:
Michael Scire
2018-12-18 15:55:16 -08:00
parent 3924a2ef76
commit 95a9e1e215
4 changed files with 63 additions and 1 deletions
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44
exosphere/lp0fw/src/secmon.c
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@@ -25,6 +25,7 @@
/* "private" functions. */
static bool secmon_should_clear_aes_keyslot(unsigned int keyslot);
static void secmon_clear_unused_keyslots(void);
static void secmon_decrypt_saved_image(void *dst, const void *src, size_t size);
void secmon_restore_to_tzram(const uint32_t target_firmware) {
/* Newer warmboot binaries clear the untouched keyslots for safety. */
@@ -32,10 +33,51 @@ void secmon_restore_to_tzram(const uint32_t target_firmware) {
secmon_clear_unused_keyslots();
}
/* Decrypt Secure Monitor from DRAM into TZRAM. */
void *tzram_src = (void *)(0x80010000);
void *tzram_dst = (void *)(target_firmware >= ATMOSPHERE_TARGET_FIRMWARE_500 ? 0x7C012000 : 0x7C010000);
const size_t tzram_size = 0xE000;
secmon_decrypt_saved_image(tzram_dst, tzram_src, tzram_size);
/* Nintendo clears DRAM, but I'm not sure why, given they lock out BPMP access to DRAM. */
for (size_t i = 0; i < tzram_size/sizeof(uint32_t); i++) {
((volatile uint32_t *)tzram_src)[i] = 0;
}
/* Make security engine require secure busmaster. */
se_get_regs()->_0x4 = 0;
/* TODO: stuff */
}
void secmon_decrypt_saved_image(void *dst, const void *src, size_t size) {
/* First, AES-256-CBC decrypt the image into TZRAM. */
se_aes_256_cbc_decrypt(KEYSLOT_SWITCH_LP0TZRAMKEY, dst, size, src, size);
/* Next, calculate CMAC. */
uint32_t tzram_cmac[4] = {0, 0, 0, 0};
se_compute_aes_256_cmac(KEYSLOT_SWITCH_LP0TZRAMKEY, tzram_cmac, sizeof(tzram_cmac), dst, size);
/* Validate the MAC against saved one in PMC scratch. */
if (tzram_cmac[0] != APBDEV_PMC_SECURE_SCRATCH112_0 ||
tzram_cmac[1] != APBDEV_PMC_SECURE_SCRATCH113_0 ||
tzram_cmac[2] != APBDEV_PMC_SECURE_SCRATCH114_0 ||
tzram_cmac[3] != APBDEV_PMC_SECURE_SCRATCH115_0) {
reboot();
}
/* Clear the PMC scratch registers that hold the CMAC. */
APBDEV_PMC_SECURE_SCRATCH112_0 = 0;
APBDEV_PMC_SECURE_SCRATCH113_0 = 0;
APBDEV_PMC_SECURE_SCRATCH114_0 = 0;
APBDEV_PMC_SECURE_SCRATCH115_0 = 0;
/* Clear keyslot now that we're done with it. */
clear_aes_keyslot(KEYSLOT_SWITCH_LP0TZRAMKEY);
}
bool secmon_should_clear_aes_keyslot(unsigned int keyslot) {
/* We'll just compare keyslot against a hardcoded list of keys. */
static const uint8_t saved_keyslots[6] = {
KEYSLOT_SWITCH_LP0TZRAMKEY,
KEYSLOT_SWITCH_SESSIONKEY,
@@ -64,4 +106,4 @@ void secmon_clear_unused_keyslots(void) {
for (unsigned int i = 0; i < KEYSLOT_RSA_MAX; i++) {
clear_rsa_keyslot(i);
}
}
}