Difference between revisions of "Ernie Secure"

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== Syscon 0xD0 four part key exchange ==
+
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 <code>0F</code> here appears to be a context 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 0xD0002 (with different sequence number for each part).
+
= Ernie Secure Packets =
  
=== Part 1 ===
+
Packets sent/received with Ernie command 0xD2 are AES-128-ECB encrypted with the Ernie communication session key (stored in [[Bigmac]] keyslot 0x511).
# 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.
 
# Syscon returns header <code>30 01 00 0F 00 00 00 00</code> + 8 byte challenge.
 
  
=== Part 2 ===
+
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.
# F00D composes a data buffer that is 8 bytes of RNG value, 8 bytes copied from challenge, and 16 bytes of shared data. On 1.69, the shared data is <code>C86B51FB019A207F32118E55462D5008</code>
 
# This data is encrypted using AES-128-CBC with all zero IV and a shared key. On 1.69, it is <code>50E4C3A77264167C409C72A9B57A8609</code>
 
# A header is prepended <code>30 02 00 0F 01 00 00 00</code> to the data and sent to Syscon
 
  
=== Part 3 ===
+
<source lang="C">
# Gets a 0x28 byte response from Syscon with a header <code>30 03 00 0F 00 00 00 00</code> and 0x20 buffer.
+
// 30 02 00 0F (step 2, keyset 0xF)
# Decrypt with AES-128-CBC with IV from part 2 (it is the last ciphertext generated, or the last 16 bytes of the ciphertext sent from F00D) and a shared key. On 1.69 it is <code>9E34087C48985B4B351A63572D9B481B</code>
+
typedef struct ernie_packet_handshake_step_2_data_plain { // size is 0x20
# Check that first 8 byte matches unknown and next 8 byte matches the F00D nonce generated in part 1.
+
    char cmep_challenge[8]; // random from Bigmac PRNG
# Encrypt the same buffer back using a shared key for 16 bytes. On 1.69 it is <code>EBE3460D84A41754AC441368CF0200D8</code> and the IV will be the last 16 bytes from the encrypted input buffer.
+
    char ernie_challenge[8]; // random from Ernie during step 1
# This is now the session key!
+
    char step2_passphrase[0x10]; // hardcoded
 +
} ernie_packet_handshake_step_2_data_plain;
  
=== Part 4 ===
+
// 30 04 00 0F (step 4, keyset 0xF)
# Using the session key, encrypt a known value. On 1.69 it is <code>457798C6D9B8390DDCA49745746F65A000000000000000000000000000000000</code>
+
typedef struct ernie_packet_handshake_step_4_data_plain { // size is 0x20
# Append the header <code>30 04 00 0F 00 00 00 00</code> and send to Syscon
+
    char step4_5_passphrase[0x10]; // hardcoded
# 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.
+
    char padding[0x10];
# Keyslot 0x511 is programmed with the session key.
+
} ernie_packet_handshake_step_4_data_plain;
# Keyslot 0x512 is programmed with a 32 bit random number from Bigmac.
 
  
== Syscon 0xD2 ==
+
typedef struct ernie_secure_packet { // size is 0x28
Packets sent/received with syscon 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.
+
    char unk_0; // 0x30 for commands 0xA0, 0xD0
 +
    char step; // 0-5 for command 0xD0
 +
    char unk_2; // usually 0, 0x20 (command 0xD2)
 +
    char keyset; // 6 (SNVS), 0xB (command 0xA0), 0xE (SNVS), 0xF (command 0xD0)
 +
    SceUInt32 unk_4; // zeroed or not
 +
    char enc_data[0x20]; // AES128ECB with key = Bigmac keyslot 0x511, or with the corresponding Step Key for commands 0xA0 and 0xD0
 +
} ernie_secure_packet;
 +
</source>
 +
 
 +
= Ernie Secure Commands =
 +
 
 +
== Command 0xA0 ==
 +
 
 +
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.
 +
 
 +
== Command 0xD0 ==
 +
 
 +
This command establishes a handshake with keyset 0xF. It is used by updater_service_sm command 0xD0002 as well as second_loader.
 +
 
 +
After handshake:
 +
* Bigmac keyslot 0x511 is programmed with the Ernie communication session key.
 +
* Bigmac keyslot 0x512 is programmed with a 32 bit random number from Bigmac PRNG.
 +
 
 +
== Command 0xD2 ==
 +
 
 +
Command for SNVS read/write and maybe also eMMC read/write.
 +
 
 +
=== Boot dumps ===
 +
 
 +
First transaction (Mgmt Data read):
 +
 
 +
cMeP => Ernie: <code>00 00 20 00 47 D3 65 F4 00 00 00 00 00 00 6C FD</code>
 +
 
 +
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>
 +
 
 +
SNVS sector is decrypted using a bigmac keyslot in 0x502-0x504 and result (Mgmt Data) is written to Bigmac keyslot 0x50B (8 bytes).
 +
 
 +
Second transaction (Current firmware version read):
 +
 
 +
cMeP => Ernie:  <code>20 00 20 00 48 D3 65 F4 00 00 00 00 00 00 4B FD</code>
 +
 
 +
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>
 +
 
 +
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.
 +
 
 +
= Ernie Secure Handshake =
 +
 
 +
This handshake is used totally or partially by Ernie secure commands 0xA0 and 0xD0.
 +
 
 +
== Step 0: cMeP challenges Ernie ==
 +
 
 +
# 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.
 +
 
 +
== Step 1: Ernie returns Ernie Challenge ==
 +
 
 +
# Ernie returns header <code>30 01 00 0F 00 00 00 00</code> + 8 byte Ernie Challenge.
 +
 
 +
== Step 2: cMeP sends cMeP Challenge ==
 +
 
 +
# 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'''.
 +
# cMeP encrypts this data using AES-128-ECB and '''Step 2 Key'''.
 +
# cMeP appends the header <code>30 02 00 0F 01 00 00 00</code> and sends to Ernie.
 +
 
 +
== Step 3: Ernie confirms it has received cMeP Challenge ==
 +
 
 +
# Ernie returns header <code>30 03 00 0F 00 00 00 00</code> and a 0x20 byte encrypted buffer.
 +
# cMeP decrypts it with AES-128-ECB and '''Step 3 Key'''.
 +
# 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.
 +
 
 +
== Step 3 bis: cMeP registers the Ernie Communication Session Key ==
 +
 
 +
# 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.
 +
# cMeP AES-128-ECB encrypts the same 16 byte challenge buffer using '''Ernie Communication Session Key Master Key'''.
 +
# This is the '''Ernie Communication Session Key'''. cMeP registers it into Bigmac keyslot 0x511.
 +
 
 +
== Step 4: cMeP tells Ernie to register the Ernie Communication Session Key ==
 +
 
 +
# Using the Ernie communication session key, cMeP encrypts a known value, '''Step 4-5 Passphrase'''.
 +
# cMeP appends the header <code>30 04 00 0F 00 00 00 00</code> and sends to Ernie.
 +
# Ernie decrypts the received data and checks that the passphrase is valid.
 +
# Ernie generates the '''Ernie Communication Session Key''' the same way as cMeP and registers it in its memory.
 +
 
 +
== Step 5: cMeP receives Ernie encrypted packet for Ernie Communication Session Key verification ==
 +
 
 +
# 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'''.
 +
 
 +
= SNVS =
 +
 
 +
Ernie provides raw storage in its Data Flash memory, named NVS (Non-Volatile Storage) by SCE. The PS Vita OS partitions some of this storage for encrypted data. The keys to encrypt/decrypt these data are from cMeP keyslots 0x502-0x504. They are derived by second_loader by encrypting using AES-256-CBC a seed with cMeP 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.
 +
 
 +
Sectors where data is written are encrypted with AES-XTS.
 +
 
 +
1 sector is 0x20 bytes.
 +
 
 +
<source lang="C">
 +
typedef struct SceMgmtData { // size is 0x20-bytes. for SNVS sector 0.
 +
SceUInt32 magic;
 +
SceUInt32 version;
 +
SceUInt32 status; // ((status & 1) != 0): manu mode/((status & 2) != 0): sd mode
 +
SceUInt32 flags; // ((flags & 1) == 0): SNVS inited/((flags & 2) == 0): QAF inited
 +
SceUInt8 cmac[0x10];
 +
} SceMgmtData;
 +
</source>
 +
 
 +
{| class="wikitable"
 +
|-
 +
! Sector pos !! nSector !! Comment !! Used by
 +
|-
 +
| 0 || 1 || A special SNVS sector called "Mgmt Data". Embeds SNVS flags and ProductMode. Used for Update, PM and QAF. || "sceSblQafManagerSetFlag" (sub_81001610 on FW 0.990), "SpkgInfoUtilGetSNVSFlagStatus" and "SpkgInfoUtilSetSNVSFlagStatus" (on FW 0.931), setProductMode
 +
|-
 +
| 1 || 1 || System Software version info. || ?SceSblUpdateMgr when updating any component?
 +
|-
 +
| 2 || 1 || Processor version info. (Current System Software version, Syscon version, unknown processor, CP version) || ?SceSblUpdateMgr when updating any component?
 +
|-
 +
| 3 || 2 || Some flags. ||
 +
|-
 +
| 5 || 1 || Active SLB2 sha256. || SceSblUpdateMgr when updating SLB2.
 +
|-
 +
| 6 || 1 || Inactive SLB2 sha256. || SceSblUpdateMgr when updating SLB2.
 +
|-
 +
| 7 || 3 || Unknown sectors. ||
 +
|-
 +
| 0xA || 1 || Battery HW info, Battery FW info, unknown info. || SceSblUpdateMgr when updating Battery IC firmware.
 +
|-
 +
| 0xB || 0xA || Unknown sectors. Filled by 0xDEADBEEF. ||
 +
|-
 +
| 0x15 || 1 || QA Flag Version. 0x10 bytes data + 0x10 bytes AES256CMAC. If not QA Flagged unit, 0xFFed with non XTS encrypted. || "sceSblQafManagerSetQaFlagVersion" on FW 0.940
 +
|-
 +
| 0x16 || 0xA || Unknown. 0xFFed. ||
 +
|}
 +
 
 +
= Firmware =
 +
 
 +
See [[Ernie Firmware]].
 +
 
 +
 
 +
[[Category:Syscon]]

Latest revision as of 05:10, 10 September 2022

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.

Ernie Secure Packets

Packets sent/received with Ernie command 0xD2 are AES-128-ECB encrypted with the Ernie communication session key (stored in Bigmac keyslot 0x511).

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.

// 30 02 00 0F (step 2, keyset 0xF)
typedef struct ernie_packet_handshake_step_2_data_plain { // size is 0x20
    char cmep_challenge[8]; // random from Bigmac PRNG
    char ernie_challenge[8]; // random from Ernie during step 1
    char step2_passphrase[0x10]; // hardcoded
} ernie_packet_handshake_step_2_data_plain;

// 30 04 00 0F (step 4, keyset 0xF)
typedef struct ernie_packet_handshake_step_4_data_plain { // size is 0x20
    char step4_5_passphrase[0x10]; // hardcoded
    char padding[0x10];
} ernie_packet_handshake_step_4_data_plain;

typedef struct ernie_secure_packet { // size is 0x28
    char unk_0; // 0x30 for commands 0xA0, 0xD0
    char step; // 0-5 for command 0xD0
    char unk_2; // usually 0, 0x20 (command 0xD2)
    char keyset; // 6 (SNVS), 0xB (command 0xA0), 0xE (SNVS), 0xF (command 0xD0)
    SceUInt32 unk_4; // zeroed or not
    char enc_data[0x20]; // AES128ECB with key = Bigmac keyslot 0x511, or with the corresponding Step Key for commands 0xA0 and 0xD0
} ernie_secure_packet;

Ernie Secure Commands

Command 0xA0

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.

Command 0xD0

This command establishes a handshake with keyset 0xF. It is used by updater_service_sm command 0xD0002 as well as second_loader.

After handshake:

  • Bigmac keyslot 0x511 is programmed with the Ernie communication session key.
  • Bigmac keyslot 0x512 is programmed with a 32 bit random number from Bigmac PRNG.

Command 0xD2

Command for SNVS read/write and maybe also eMMC read/write.

Boot dumps

First transaction (Mgmt Data read):

cMeP => Ernie: 00 00 20 00 47 D3 65 F4 00 00 00 00 00 00 6C FD

cMeP <= Ernie: 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

SNVS sector is decrypted using a bigmac keyslot in 0x502-0x504 and result (Mgmt Data) is written to Bigmac keyslot 0x50B (8 bytes).

Second transaction (Current firmware version read):

cMeP => Ernie: 20 00 20 00 48 D3 65 F4 00 00 00 00 00 00 4B FD

cMeP <= Ernie: 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

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.

Ernie Secure Handshake

This handshake is used totally or partially by Ernie secure commands 0xA0 and 0xD0.

Step 0: cMeP challenges Ernie

  1. cMeP generates an empty buffer 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 and sends it to Ernie.

Step 1: Ernie returns Ernie Challenge

  1. Ernie returns header 30 01 00 0F 00 00 00 00 + 8 byte Ernie Challenge.

Step 2: cMeP sends cMeP Challenge

  1. 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.
  2. cMeP encrypts this data using AES-128-ECB and Step 2 Key.
  3. cMeP appends the header 30 02 00 0F 01 00 00 00 and sends to Ernie.

Step 3: Ernie confirms it has received cMeP Challenge

  1. Ernie returns header 30 03 00 0F 00 00 00 00 and a 0x20 byte encrypted buffer.
  2. cMeP decrypts it with AES-128-ECB and Step 3 Key.
  3. 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.

Step 3 bis: cMeP registers the Ernie Communication Session Key

  1. 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.
  2. cMeP AES-128-ECB encrypts the same 16 byte challenge buffer using Ernie Communication Session Key Master Key.
  3. This is the Ernie Communication Session Key. cMeP registers it into Bigmac keyslot 0x511.

Step 4: cMeP tells Ernie to register the Ernie Communication Session Key

  1. Using the Ernie communication session key, cMeP encrypts a known value, Step 4-5 Passphrase.
  2. cMeP appends the header 30 04 00 0F 00 00 00 00 and sends to Ernie.
  3. Ernie decrypts the received data and checks that the passphrase is valid.
  4. Ernie generates the Ernie Communication Session Key the same way as cMeP and registers it in its memory.

Step 5: cMeP receives Ernie encrypted packet for Ernie Communication Session Key verification

  1. cMeP gets a response back from Ernie (header 30 05 00 0F 00 00 00 00), decrypts the encrypted data with the Ernie communication session key, and checks that it matches the Step 4-5 Passphrase.

SNVS

Ernie provides raw storage in its Data Flash memory, named NVS (Non-Volatile Storage) by SCE. The PS Vita OS partitions some of this storage for encrypted data. The keys to encrypt/decrypt these data are from cMeP keyslots 0x502-0x504. They are derived by second_loader by encrypting using AES-256-CBC a seed with cMeP 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.

Sectors where data is written are encrypted with AES-XTS.

1 sector is 0x20 bytes.

typedef struct SceMgmtData { // size is 0x20-bytes. for SNVS sector 0.
	SceUInt32 magic;
	SceUInt32 version;
	SceUInt32 status; // ((status & 1) != 0): manu mode/((status & 2) != 0): sd mode
	SceUInt32 flags; // ((flags & 1) == 0): SNVS inited/((flags & 2) == 0): QAF inited
	SceUInt8 cmac[0x10];
} SceMgmtData;
Sector pos nSector Comment Used by
0 1 A special SNVS sector called "Mgmt Data". Embeds SNVS flags and ProductMode. Used for Update, PM and QAF. "sceSblQafManagerSetFlag" (sub_81001610 on FW 0.990), "SpkgInfoUtilGetSNVSFlagStatus" and "SpkgInfoUtilSetSNVSFlagStatus" (on FW 0.931), setProductMode
1 1 System Software version info. ?SceSblUpdateMgr when updating any component?
2 1 Processor version info. (Current System Software version, Syscon version, unknown processor, CP version) ?SceSblUpdateMgr when updating any component?
3 2 Some flags.
5 1 Active SLB2 sha256. SceSblUpdateMgr when updating SLB2.
6 1 Inactive SLB2 sha256. SceSblUpdateMgr when updating SLB2.
7 3 Unknown sectors.
0xA 1 Battery HW info, Battery FW info, unknown info. SceSblUpdateMgr when updating Battery IC firmware.
0xB 0xA Unknown sectors. Filled by 0xDEADBEEF.
0x15 1 QA Flag Version. 0x10 bytes data + 0x10 bytes AES256CMAC. If not QA Flagged unit, 0xFFed with non XTS encrypted. "sceSblQafManagerSetQaFlagVersion" on FW 0.940
0x16 0xA Unknown. 0xFFed.

Firmware

See Ernie Firmware.