Editing SC Communication

[[Category:Software]]
=Introduction=

* The following information was reverse engineered from lv0ldr, lv0, lv1, and sc_iso.self.
* Big thanks to graf_chokolo for a large part of the basis of this page, and to Jestero for Syscon Authentication info!

=Overview of Syscon Communication=

*Syscon lives at the mmio space of 0x24000080000.
*Communication occurs through mmio read/writes.

List of known offsets in Syscon:

{| class="wikitable FCK__ShowTableBorders"
|-
! Offset (from start of address space) !! Size !! Description
|-
|0xC000 || 0xFF0 || Syscon packet send area
|-
|0xCFF0 || 0x4   || Syscon sent packet counter
|-
|0xCFF4 || 0x4   || Syscon sent packet acknowledge counter
|-
|0xD000 || 0xFF0 || Syscon packet receive area
|-
|0xDFF0 || 0x4   || Syscon received packet counter
|-
|0xDFF4 || 0x4   || Syscon received packet acknowledge counter
|-
|0xE100 || 0x4   || Tells syscon there is a packet to be received
|}

Quick explanation of the packet counters:
* There are two counters that are incremented by each side (Cell / Syscon).
* 0xCFF0 and 0xDFF0 are incremented by the sending side (Syscon for 0xCFF0, Cell for 0xDFF0)
* 0xCFF4 and 0xDFF4 are incremented by the receiving side (Cell for 0xCFF4, Syscon for 0xDFF4)

=Syscon Services=
* To be completed...

{| class="wikitable FCK__ShowTableBorders"
|-
! Service ID !! Description
|-
| 0x14 || NVS Service - Used for eeprom read/write (Non-Volatile Storage?)
|-
| 0x18 || Livelock(?) Service - Checks for permission to use other services
|-
| 0x20 || Syscon Debug Output(?) - Used to send a string to syscon.
|-
| 0x1F || Authenticated Services
|-
| 0xFF || Syscon Init (Seen in lv0ldr init sequence to syscon: http://www.ps3devwiki.com/wiki/User_talk:JuanNadie)
|}

=Syscon Packet Headers=
* Some useful packet headers...
* If the header is shorter than 0x10, you must add your own size.

{| class="wikitable FCK__ShowTableBorders"
|-
! What? !! Description || Data || Notes
|-
| AUTH1 || AUTH1 Header || 0x1F, 0x01, 0x00, 0x00, 0x00, 0x00, 0x80, 0x20, 0x00, 0x00, 0x00, 0x00,<br>0x00, 0x30, 0x00, 0x30 ||
|-
| AUTH2 || AUTH2 Header || 0x1F, 0x01, 0x00, 0x01, 0x00, 0x00, 0x80, 0x21, 0x00, 0x00, 0x00, 0x00,<br>0x00, 0x30, 0x00, 0x30 ||
|-
| Debug Output || Sends string to Syscon TTY || 0x20, 0x01, 0x00, 0x07, 0x00, 0x00, 0x80, 0x28, 0x00, 0x00, 0x00, 0x00<br>|| Start message with 0x00. Will print as much as packet length.
|}

=Syscon Authentication=
 - An IV of 0x00 is used for most AES steps.

== Step 1 - Generate Individual Seeds ==
Encrypt sc_iso metadata seeds w/ eid root key / iv.

<pre>aes256cbc_enc(eid_root_erk, eid_root_riv, sc_module_seeds, 0x40, sc_module_seeds);</pre>

== Step 2 - Generate SC_ISO encrypted keys ==
Encrypt the sc_key_seeds.

<pre>
indiv_key = sc_module_seeds + 0x20;
for (int i = 0; i < 0x100; i += 0x10)
    aes256cbc_enc(indiv_key, zero_iv, key_seeds + i, 0x10, enc_key_seeds + i);
</pre>

== Step 3 - Authenticate with Syscon ==
Pick a session_id. Must be <= 7.

=== Step 3a - Secure Packet Header ===
<pre>
struct secure_payload_header {
    u8 session_id;
    u8 seq_service_id;  //service_ID (Unsecure uses 0xFF, AUTH1 = 0x02, AUTH2 = 0x03, READ/WRITE = 0x04)
    u8 packet_type;     //0xFF for BE->SC, 0x00 for SC->BE (if success)
    u8 magic[0x2];      //0xAD1A
    u8 prng_random[0xB] //Random shit for padding
};
</pre>

=== Step 3b - AUTH 1 to SC ===
<pre>
uint8_t random_shit[0x10];
auth_key_1_0x01 = enc_key_seeds + (session_id * (0x10*2));
auth_key_2_0x01 = enc_key_seeds + (session_id * (0x10*2) + 0x10);

//generating random payload for auth1
rnd_gen(random_shit, 0x10);

//create auth1 random data
aes128cbc_enc(auth_key_1_0x01, zero_iv, random_shit, 0x10, secure_payload_buf + 0x10);

//length = 0x20
//Create secure header/footer
// create header: 5 bytes + random stuff (0xb)
payload_header->session_id = session_id;
payload_header->seq_service_id = seq_service_id++; // starts at 0
payload_header->packet_type = 0xFF;
payload_header->magic[0] = 0xAD;
payload_header->magic[1] = 0x1A;
rnd_gen((u8*) &payload_header->prng_random, 0x0B);
    
//encrypt payload
aes128cbc_enc(be2sc_key, zero_iv, secure_payload_buf, length, secure_payload_buf);

// create footer: omac1 of the whole packet
aesOmac1Mode(secure_payload_buf + length, secure_payload_buf, length, be2sc_key, sizeof(be2sc_key)*8);

//Set regular header
memcpy(sc_packet, auth1_pkt_header, 0x10);

//Send packet. 0x40 Bytes
</pre>

=== Step 3c - Validate AUTH1 ===
First, check the header/footer.
* Calulcate aesOmac over the packet length and compare to omac from syscon. Use sc2be key.
* Decrypt internal packet with sc2be key. Use AES128-CBC
* Compare returned session_id and seq_service_id.
* Check secure_payload_buf[0x2] == 0.

Then check the AUTH1 response
<pre>
// decrypt secure_payload
for (i = 0x0; i < 0x20; i += 0x10)
    aes128cbc(auth_key_2_0x01, zero_iv, secure_payload_buf + 0x10 + i, 0x10, secure_payload_buf + 0x10 + i);
    
// check if challange returned from syscon is correct
res = memcmp(secure_payload_buf + 0x10, random_shit, 0x10);
if (res != 0)
    return -1;
    
// save the new challange needed for AUTH2
memcpy(auth_challenge, secure_payload_buf + 0x20, 0x10);
</pre>

=== Step 3d - AUTH2 to SC ===
<pre>
//AUTH2 Challenge Payload
aes128cbc_enc(auth_key_1_0x01, zero_iv, auth_challenge, 0x10, secure_payload_buf + 0x10);

//length = 0x20
//Create secure header/footer
// create header: 5 bytes + random stuff (0xb)
payload_header->session_id = session_id;
payload_header->seq_service_id = seq_service_id++; // starts at 0
payload_header->packet_type = 0xFF;
payload_header->magic[0] = 0xAD;
payload_header->magic[1] = 0x1A;
rnd_gen((u8*) &payload_header->prng_random, 0x0B);
    
//encrypt payload
aes128cbc_enc(be2sc_key, zero_iv, secure_payload_buf, length, secure_payload_buf);

// create footer: omac1 of the whole packet
aesOmac1Mode(secure_payload_buf + length, secure_payload_buf, length, be2sc_key, sizeof(be2sc_key)*8);

//Set regular header
memcpy(sc_packet, auth2_pkt_header, 0x10);

//Put packet - 0x40 packet length
</pre>

=== Step 3e - Validate AUTH2 ===
Again, check the header/footer.
* Calulcate aesOmac over the packet length and compare to omac from syscon. Use sc2be key.
* Decrypt internal packet with sc2be key. Use AES128-CBC
* Compare returned session_id and seq_service_id.
* Check secure_payload_buf[0x2] == 0.

<pre>
// encrypt random_shit using auth_challenge (returned from AUTH1 reply) as key and 0 IV
aes128cbc_enc(auth_challenge, zero_iv, random_shit, 0x10, session_key);

// encrypt result in place with session_key_create[0x10 * sess_id] and IV 0 (result will be the session_key)
aes128cbc_enc(session_key_create + (session_id * 0x10), zero_iv, session_key, 0x10, session_key);

// use the session_key to decrypt auth2_payload in place (0x10)
aes128cbc(session_key, zero_iv, secure_payload_buf + 0x10, 0x10, secure_payload_buf + 0x10);
    
// compare the result with a 0x10 zero string
res = memcmp(secure_payload_buf + 0x10, zero_iv, 0x10);

//res == 0x0 is good.
</pre>

== Step 4 - Profit? ==
You are now authenticated with syscon, and can use privileged commands. Just use the session_key calculated from the AUTH2 reply to encrypt/decrypt responses.