Changes

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| Security Engine keyslots vulnerable to partial overwrite attack

| Security Engine keyslots vulnerable to partial overwrite attack

| The Tegra X1 security engine supports writing keyslot data to the engine with syntax as follows: SECURITY_ENGINE->AES_KEYTABLE_ADDR = (keyslot << 24) | (dword_index_in_keyslot); SECURITY_ENGINE->AES_KEYTABLE_DATA = readle32(key, dword_index_in_keyslot * 4);  

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The Tegra X1 security engine supports writing keyslot data to the engine with syntax as follows:  

 

SECURITY_ENGINE->AES_KEYTABLE_ADDR = (keyslot << 24) | (dword_index_in_keyslot);  

 

SECURITY_ENGINE->AES_KEYTABLE_DATA = readle32(key, dword_index_in_keyslot * 4);  

However, the Security Engine flushes writes to the internal key tables immediately when AES_KEYTABLE_DATA is written -- this allows one to overwrite a single dword of a key at a time, and thus brute force the contents of keyslots in time (2^32 * 8) = 2^35 instead of 2^256.

However, the Security Engine flushes writes to the internal key tables immediately when AES_KEYTABLE_DATA is written -- this allows one to overwrite a single dword of a key at a time, and thus brute force the contents of keyslots in time (2^32 * 8) = 2^35 instead of 2^256.