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1,545 bytes added ,  04:09, 1 June 2020
Note: keys removed.
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== SNVS ==
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For security reasons, sensitive Ernie commands packets are encrypted with a per-session key. This key is generated and shared at second_loader stage through a '''handshake''' between cMeP and Ernie. SNVS (Secure NVS) is a part of NVS that is XTS encrypted and can only be accessed using Ernie secure command 0xD2. eMMC is also XTS encrypted and is accessed with the same command.
   −
The syscon provides raw storage. Kermit partitions some of this storage for encrypted data. The keys to encrypt/decrypt this data is from slots 0x502-0x504. They are derived by second_loader by encrypting a constant buffer with key slot 0x216 using AES-256-CBC, which is console unique. Consoles with factory firmware < 0.996 use a set of static keys found in second_loader. Factory firmware comes from idstorage.
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= Ernie Secure Packets =
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== Shared Secrets ==
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Packets sent/received with Ernie command 0xD2 are AES-128-ECB encrypted with the Ernie communication session key (stored in [[Bigmac]] keyslot 0x511).
   −
{| class="wikitable sortable"
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There is a 4 byte command field, 4 byte counter (from Bigmac keyslot 0x512) that increments per send, 6 bytes of zeros, optional data, and a 2 byte checksum. The checksum is the sum of all previous bytes and then negated.
|-
  −
! Class !! Shared Key A !! Shared Key B !! Shared Key C !! Shared Data A !! Shared Data B
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|-
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| 0xB || <code>BB644721CB4C55072E83177BEB3BBEE9</code> || <code>DC6B6EE0F457DF0E7BAD1C5EA338027F</code> || <code>00000000000000000000000000000000</code> || <code>CF2E93E9F94E28CCA48026134C7C77CE</code> ||
  −
|-
  −
| 0xF || <code>50E4C3A77264167C409C72A9B57A8609</code> || <code>9E34087C48985B4B351A63572D9B481B</code> || <code>EBE3460D84A41754AC441368CF0200D8</code> || <code>C86B51FB019A207F32118E55462D5008</code> || <code>457798C6D9B8390DDCA49745746F65A000000000000000000000000000000000</code>
  −
|-
  −
|}
     −
== Syscon four part key exchange ==
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<source lang="C">
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// 30 02 00 0F (step 2, keyset 0xF)
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typedef struct ernie_packet_handshake_step_2_data_plain { // size is 0x20
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    char cmep_challenge[8]; // random from Bigmac PRNG
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    char ernie_challenge[8]; // random from Ernie during step 1
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    char step2_passphrase[0x10]; // hardcoded
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} ernie_packet_handshake_step_2_data_plain;
   −
The <code>0F</code> here appears to be a class id. Only <code>0F</code> and <code>0B</code> has been seen but only <code>0F</code> seems to be supported by the update sm using the command [[F00D_Commands#0xD0002|0xD0002]] (with different sequence number for each part).
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// 30 04 00 0F (step 4, keyset 0xF)
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typedef struct ernie_packet_handshake_step_4_data_plain { // size is 0x20
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    char step4_5_passphrase[0x10]; // hardcoded
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    char padding[0x10];
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} ernie_packet_handshake_step_4_data_plain;
   −
=== Part 1: Ernie challenges Kermit ===
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typedef struct ernie_secure_packet { // size is 0x28
# Generate an empty buffer <code>30 00 00 0F 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00</code> and send it to Syscon.
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    char unk_0; // 0x30 for commands 0xA0, 0xD0
# Syscon returns header <code>30 01 00 0F 00 00 00 00</code> + 8 byte challenge.
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    char step; // 0-5 for command 0xD0
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    char unk_2; // usually 0, 0x20 (command 0xD2)
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    char keyset; // 6 (SNVS), 0xB (command 0xA0), 0xE (SNVS), 0xF (command 0xD0)
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    SceUInt32 unk_4; // zeroed or not
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    char enc_data[0x20]; // AES128ECB with key = Bigmac keyslot 0x511, or with the corresponding Step Key for commands 0xA0 and 0xD0
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} ernie_secure_packet;
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</source>
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=== Part 2: Kermit responds and challenges Ernie ===
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= Ernie Secure Commands =
# F00D composes a data buffer that is 8 bytes of RNG value, 8 bytes copied from challenge in part 1.2, and 16 bytes of '''Shared Data A'''.
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# This data is encrypted using AES-128-CBC with all zero IV and '''Shared Key A''' as the key.
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# A header is prepended <code>30 02 00 0F 01 00 00 00</code> to the data and sent to Syscon
     −
=== Part 3: Session Key Establishment ===
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== Command 0xA0 ==
# Gets a 0x28 byte response from Syscon with a header <code>30 03 00 0F 00 00 00 00</code> and 0x20 buffer.
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# Decrypt with AES-128-CBC with all zero IV and the key '''Shared Key B'''.
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# Check that first 8 byte matches the challenge from part 1.2 and next 8 byte matches the F00D nonce generated in part 2.1. The remaining 16 bytes are zero.
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# Encrypt the same buffer back using '''Shared Key C''' for 16 bytes. The IV will be the last 16 bytes from the encrypted input buffer.
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# This is now the session key!
     −
=== Part 4: Verification ===
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This command uses keyset 0xB and is only seen in second_loader. No data transfer is seen. The Ernie communication session key derived here is actually not used. The hypothesis is that this handshake serves as a checkpoint for Ernie to know that cMeP has successfully decrypted ConsoleId and OpenPsId since in between the handshake each decryption happens. The decryption does not use any data from this handshake.
# Using the session key, encrypt a known value, '''Shared Data B'''.
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# Append the header <code>30 04 00 0F 00 00 00 00</code> and send to Syscon
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# Get a response back from Syscon (header <code>30 05 00 0F 00 00 00 00</code>), decrypt the buffer with the session, and check that it matches the known value. Both the plaintext and ciphertext should match.
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This part is only seen used with command 0xD0 and not 0xA0.
     −
=== Channel Protocol ===
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== Command 0xD0 ==
   −
Packets sent/received with command 0xD2 are encrypted with the session key and IV = 0. There is a 4 byte command field, 4 byte counter (from keyslot 0x512) that increments per send, 6 bytes of zeros, optional data, and a 2 byte checksum. The checksum is the sum of all previous bytes and then negated.
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This command establishes a handshake with keyset 0xF. It is used by updater_service_sm command 0xD0002 as well as second_loader.
   −
== Syscon 0xA0 ==
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After handshake:
This command uses class 0xB and is only seen in secure_loader. No data transfer is seen. The session key derived here is actually not used. The hypothesis is that this handshake serves as a checkpoint for the Syscon to know that F00D has successfully decrypted IDPS and OpenPSID since in between the handshake each decryption happens. The decryption does not use any data from this handshake.
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* Bigmac keyslot 0x511 is programmed with the Ernie communication session key.
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* Bigmac keyslot 0x512 is programmed with a 32 bit random number from Bigmac PRNG.
   −
== Syscon 0xD0 ==
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== Command 0xD2 ==
Establishes a secure channel for class 0xF used by updater 0xD0002 as well as second_loader.
     −
After handshake:
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Command for SNVS read/write and eMMC read/write.
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=== Boot dumps ===
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First transaction (Mgmt Data read):
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cMeP => Ernie: <code>00 00 20 00 47 D3 65 F4 00 00 00 00 00 00 6C FD</code>
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cMeP <= Ernie: <code>00 00 20 00 47 D3 65 F4 00 00 00 00 00 00 01 DD C7 AB 57 AD 28 9E 00 93 51 F8 D3 D2 29 2E 78 B6 8C 63 5A 26 7A A9 6B C8 E3 AC F3 3D 61 77 F0 EC</code>
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SNVS sector is decrypted using a bigmac keyslot in 0x502-0x504 and result (Mgmt Data) is written to Bigmac keyslot 0x50B (8 bytes).
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Second transaction (Current firmware version read):
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cMeP => Ernie:  <code>20 00 20 00 48 D3 65 F4 00 00 00 00 00 00 4B FD</code>
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cMeP <= Ernie:  <code>20 00 20 00 48 D3 65 F4 00 00 00 00 00 00 95 AD 79 D1 FE 5E 96 4B 3F 66 7D 47 04 28 05 E9 EB D1 26 86 E2 C1 9B 7B 53 B6 D3 11 76 8F 2D 3F 80 ED</code>
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Decrypted is a list of versions, two are read using some information from the MBR. On a default 3.60 retail system, the two offsets used are at 0x4 and 0x8. Those are both checked to be 0x03600000 on 3.60 (hard coded). If they are 0xDEADBEEF, the check is skipped. Additionally, in the decrypted buffer from the previous command (written to Bigmac keysslot 0x50B), if bit 1 at byte offset 0x4 is set, then the version check is skipped. Then, if boot is not resume the version from kernel_boot_loader.self is also checked. Finally slot 0x50E and 0x518 are written with these two version codes.
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= Ernie Secure Handshake =
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This handshake is used totally or partially by Ernie secure commands 0xA0 and 0xD0.
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== Step 0: cMeP challenges Ernie ==
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# cMeP generates an empty buffer <code>30 00 00 0F 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00</code> and sends it to Ernie.
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== Step 1: Ernie returns Ernie Challenge ==
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# Ernie returns header <code>30 01 00 0F 00 00 00 00</code> + 8 byte Ernie Challenge.
   −
Keyslot 0x511 is programmed with the session key.
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== Step 2: cMeP sends cMeP Challenge ==
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Keyslot 0x512 is programmed with a 32 bit random number from Bigmac.
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# cMeP composes a data buffer that is 8 bytes of RNG value, 8 byte Ernie Challenge from step 1, and 16 bytes of '''Step 2 Passphrase'''.
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# cMeP encrypts this data using AES-128-ECB and '''Step 2 Key'''.
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# cMeP appends the header <code>30 02 00 0F 01 00 00 00</code> and sends to Ernie.
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== Syscon 0xD2 ==
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== Step 3: Ernie confirms it has received cMeP Challenge ==
Data transfer for class 0xF.
     −
=== Seen at boot ===
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# Ernie returns header <code>30 03 00 0F 00 00 00 00</code> and a 0x20 byte encrypted buffer.
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# cMeP decrypts it with AES-128-ECB and '''Step 3 Key'''.
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# cMeP checks that first 8 byte matches the Ernie Challenge from step 2 and next 8 byte matches the cMeP Challenge generated in step 2. The remaining 16 bytes are zero.
   −
First transaction
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== Step 3 bis: cMeP registers the Ernie Communication Session Key ==
   −
F00D => Syscon: <code>00 00 20 00 47 D3 65 F4 00 00 00 00 00 00 6C FD</code>
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# The following operations are only done with Ernie command 0xD0 as it is the only one that registers the Ernie communication session key, once for all.
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# cMeP AES-128-ECB encrypts the same 16 byte challenge buffer using '''Ernie Communication Session Key Master Key'''.
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# This is the '''Ernie Communication Session Key'''. cMeP registers it into Bigmac keyslot 0x511.
   −
F00D <= Syscon: <code>00 00 20 00 47 D3 65 F4 00 00 00 00 00 00 01 DD C7 AB 57 AD 28 9E 00 93 51 F8 D3 D2 29 2E 78 B6 8C 63 5A 26 7A A9 6B C8 E3 AC F3 3D 61 77 F0 EC</code>
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== Step 4: cMeP tells Ernie to register the Ernie Communication Session Key ==
   −
Data decrypted using a slot in 0x502-0x504 and result is written to slot 0x50B (8 bytes).
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# Using the Ernie communication session key, cMeP encrypts a known value, '''Step 4-5 Passphrase'''.
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# cMeP appends the header <code>30 04 00 0F 00 00 00 00</code> and sends to Ernie.
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# Ernie decrypts the received data and checks that the passphrase is valid.
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# Ernie generates the '''Ernie Communication Session Key''' the same way as cMeP and registers it in its memory.
   −
Second transaction
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== Step 5: cMeP receives Ernie encrypted packet for Ernie Communication Session Key verification ==
   −
F00D => Syscon:  <code>20 00 20 00 48 D3 65 F4 00 00 00 00 00 00 4B FD</code>
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# cMeP gets a response back from Ernie (header <code>30 05 00 0F 00 00 00 00</code>), decrypts the encrypted data with the '''Ernie communication session key''', and checks that it matches the '''Step 4-5 Passphrase'''.
   −
F00D <= Syscon:  <code>20 00 20 00 48 D3 65 F4 00 00 00 00 00 00 95 AD 79 D1 FE 5E 96 4B 3F 66 7D 47 04 28 05 E9 EB D1 26 86 E2 C1 9B 7B 53 B6 D3 11 76 8F 2D 3F 80 ED</code>
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= SNVS =
   −
Decrypted is a list of versions, two are read using some information from the MBR. On a default 3.60 retail system, the two offsets used are at 0x4 and 0x8. Those are both checked to be 0x03600000 on 3.60 (hard coded). If they are 0xDEADBEEF, the check is skipped. Additionally, in the decrypted buffer from the previous command (written to slot 0x50B), if bit 1 at byte offset 0x4 is set, then the version check is skipped. Then, if boot is not resume the version from kernel_boot_loader.self is also checked. Finally slot 0x50E and 0x518 are written with these two version codes.
+
Ernie provides raw storage in its EEPROM, named NVS (Non-Volatile Storage). The OS partitions some of this storage for encrypted data. The keys to encrypt/decrypt this data is from slots 0x502-0x504. They are derived by second_loader by encrypting using AES-256-CBC a seed with keyslot 0x216, which is console unique. Consoles with minimum firmware < 0.996 use a set of static keys found in second_loader. Minimum firmware comes from IdStorage SMI leaf.
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