Difference between revisions of "User:Master-bob/MACS"
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The online key is stored in an encrypted form on the Xbox's [[EEPROM]]. The key is decrypted using: | The online key is stored in an encrypted form on the Xbox's [[EEPROM]]. The key is decrypted using: | ||
| − | rc4_key = HMAC | + | // decrypt the EEPROM to get the correct hdd key |
| + | rc4_key = SHA1-HMAC of the hdd_key using "60 59 E8 2E DF BF 7F D3 23 35 74 2A 64 8B B1 2C" | ||
decrypted_online_key = rc4 of online_key using rc4_key | decrypted_online_key = rc4 of online_key using rc4_key | ||
| Line 27: | Line 28: | ||
PA-DATA TYPE 131 | PA-DATA TYPE 131 | ||
| − | This is an Xbox modification to custom Microsoft (PA-PAC-REQUEST) addition to Kerberos, used to define what the client expects in the response. This is encoded in ASN.1 (method of packing data structures into bytes, used by Kerberos). All AS-REQs contain the following data in this section: | + | This is an Xbox modification to a custom Microsoft (PA-PAC-REQUEST) addition to Kerberos, used to define what the client expects in the response. This is encoded in ASN.1 (method of packing data structures into bytes, used by Kerberos). All AS-REQs contain the following data in this section: |
SEQUENCE (2 elem) | SEQUENCE (2 elem) | ||
| Line 37: | Line 38: | ||
INTEGER 14 | INTEGER 14 | ||
| − | 13 and 14 | + | 13 and 14 correlate to PAC_CLIENT_IDENTITY and PAC_COMPOUND_IDENTITY, respectively, and are used to tell the server to include a PUID PAC (20) in the response. Not sure if it's actually needed for AS-REP. |
====PA-XBOX-PRE-PRE-AUTH==== | ====PA-XBOX-PRE-PRE-AUTH==== | ||
| Line 46: | Line 47: | ||
* currentTime - the current time, sent as a FILETIME | * currentTime - the current time, sent as a FILETIME | ||
* PPA1 - SHA1-HMAC of the principal name (the Xbox serial number) using the principal key (the online key) | * PPA1 - SHA1-HMAC of the principal name (the Xbox serial number) using the principal key (the online key) | ||
| − | * SPPA2atT | + | * SPPA2atT |
| − | ** SPPA1 - SHA1 | + | ** SPPA1 - SHA1 of PPA1 |
| − | ** PPA2 - First 8 bytes of SHA1-HMAC of | + | ** PPA2 - First 8 bytes of SHA1-HMAC of ths serial number appended to the serial number using the principal key |
** SPPA2atT - SHA1 of PPA2 appended to the current time | ** SPPA2atT - SHA1 of PPA2 appended to the current time | ||
| Line 58: | Line 59: | ||
* signature - a 20 byte array used to verify the encryption key generated for the response | * signature - a 20 byte array used to verify the encryption key generated for the response | ||
* version - null terminated string with information about the application sending the request | * version - null terminated string with information about the application sending the request | ||
| − | ** XboxVersion=1.00.5849.3 Title=0xFFFE0000 TitleVersion=408857856 | + | ** Xbox Live Dashboard 5849 - XboxVersion=1.00.5849.3 Title=0xFFFE0000 TitleVersion=408857856 |
| + | |||
===REQ-BODY=== | ===REQ-BODY=== | ||
| − | The remainder of the Kerberos | + | The remainder of the Kerberos request. '''Bold''' indicates the data are used for response building. |
* Padding - 0 | * Padding - 0 | ||
| Line 68: | Line 70: | ||
* sname - krbtgt@MACS.XBOX.COM | * sname - krbtgt@MACS.XBOX.COM | ||
* till - 2037-09-13 02:48:05 (UTC) | * till - 2037-09-13 02:48:05 (UTC) | ||
| − | * | + | * nonce - a randomly generated number |
* '''etype - RC4-HMAC-MD5''' | * '''etype - RC4-HMAC-MD5''' | ||
| Line 75: | Line 77: | ||
===The Machine Account=== | ===The Machine Account=== | ||
| + | The following is how the machine account is built ''for transfer''. It is stored in a different fashion. | ||
| + | |||
| + | ULONGLONG uniqueID; | ||
| + | CHAR gamertag[16]; // SN.XXXXXXXXXXXX (the console serial number) | ||
| + | CHAR domain[20]; // xbox.com | ||
| + | CHAR realm[24]; // passport.net | ||
| + | BYTE key[16]; | ||
===Nonce HMAC Key=== | ===Nonce HMAC Key=== | ||
| Line 80: | Line 89: | ||
temp_key = MD5-HMAC of the null terminated string "signaturekey" using the online key | temp_key = MD5-HMAC of the null terminated string "signaturekey" using the online key | ||
| − | + | salted_nonce = "5F F3 28 92 13 8C 9C 4B 05 84 9A 3C 10 1A DB 5D" // MD5 of "02 04 00 00 00 00 00 00" | |
| − | nonce_hmac_key = MD5-HMAC of | + | nonce_hmac_key = MD5-HMAC of salted_nonce using temp_key |
The key can be verified using the PA-XBOX-CLIENT-VERSION preauth: | The key can be verified using the PA-XBOX-CLIENT-VERSION preauth: | ||
| Line 87: | Line 96: | ||
test_signature = SHA1-HMAC of the version_string using the nonce_hmac_key | test_signature = SHA1-HMAC of the version_string using the nonce_hmac_key | ||
// if both signatures match, the key was generated correctly | // if both signatures match, the key was generated correctly | ||
| + | |||
| + | ===Encryption=== | ||
| + | The machine account is encrypted with the nonce HMAC key and salt 1203 using RC4-HMAC-MD5. The encrypted bytes are packed as a Kerberos EncryptedData object into a PA-DATA TYPE 203 preauthentication header in the AS-REP. | ||
==AS-REP== | ==AS-REP== | ||
Latest revision as of 16:23, 23 January 2019
The first step of Xbox Live authentication is connecting to the Machine Account Creation Service, located at MACS.XBOXLIVE.COM.
The Xbox would only connect to MACS once, the first time the console ever connected to Xbox Live. MACS was presumably used to keep banned consoles off of Xbox Live, and is still used to this day for Xbox 360s.
The MACS exchange, like the majority of Xbox Live authentication, is done using the Kerberos system.
Contents
AS-REQ
The first step of MACS authentication is sending an AS-REQ to MACS.XBOXLIVE.COM on UDP port 88. The AS-REQ is composed of several components.
- PVNO and MSG TYPE - These have default values of 5 (Kerberos version 5) and 10 (krb-as-req), respectively.
PADATA
Pre authentication data (PADATA) contains most of what makes this request unique from other Kerberos systems.
PA-ENC-TIMESTAMP
PA-DATA TYPE 2
An official part of the Kerberos standard, this is a Unix timestamp encrypted with the later defined encryption standard (in Xbox's case, RC4-HMAC-MD5). The server attempts to decrypt this to confirm that the client is using the correct password. For MACS, the password is the console's Online Key, which Microsoft stored server side on a very well guarded database.
Online Key
The online key is stored in an encrypted form on the Xbox's EEPROM. The key is decrypted using:
// decrypt the EEPROM to get the correct hdd key rc4_key = SHA1-HMAC of the hdd_key using "60 59 E8 2E DF BF 7F D3 23 35 74 2A 64 8B B1 2C" decrypted_online_key = rc4 of online_key using rc4_key
PA-PAC-REQUEST-EX
PA-DATA TYPE 131
This is an Xbox modification to a custom Microsoft (PA-PAC-REQUEST) addition to Kerberos, used to define what the client expects in the response. This is encoded in ASN.1 (method of packing data structures into bytes, used by Kerberos). All AS-REQs contain the following data in this section:
SEQUENCE (2 elem)
[0] (1 elem)
BOOLEAN true
[1] (1 elem)
SEQUENCE (2 elem)
INTEGER 13
INTEGER 14
13 and 14 correlate to PAC_CLIENT_IDENTITY and PAC_COMPOUND_IDENTITY, respectively, and are used to tell the server to include a PUID PAC (20) in the response. Not sure if it's actually needed for AS-REP.
PA-XBOX-PRE-PRE-AUTH
PA-DATA TYPE 204
This is a custom preauthentication header that was used by Microsoft to quickly look up Xbox information from their database and is probably not needed. Contains the following:
- currentTime - the current time, sent as a FILETIME
- PPA1 - SHA1-HMAC of the principal name (the Xbox serial number) using the principal key (the online key)
- SPPA2atT
- SPPA1 - SHA1 of PPA1
- PPA2 - First 8 bytes of SHA1-HMAC of ths serial number appended to the serial number using the principal key
- SPPA2atT - SHA1 of PPA2 appended to the current time
PA-XBOX-CLIENT-VERSION
PA-DATA TYPE 206
This is a custom preauthentication header and arguably the most important for MACS authentication from a homebrew perspective. Contains the following:
- signature - a 20 byte array used to verify the encryption key generated for the response
- version - null terminated string with information about the application sending the request
- Xbox Live Dashboard 5849 - XboxVersion=1.00.5849.3 Title=0xFFFE0000 TitleVersion=408857856
REQ-BODY
The remainder of the Kerberos request. Bold indicates the data are used for response building.
- Padding - 0
- KDC-Options - 0b00010000 (canonicalize)
- cname - the serial number of the Xbox
- realm - MACS.XBOX.COM
- sname - krbtgt@MACS.XBOX.COM
- till - 2037-09-13 02:48:05 (UTC)
- nonce - a randomly generated number
- etype - RC4-HMAC-MD5
Building the Response
The server must generate a valid machine account and encrypt it using the correct key.
The Machine Account
The following is how the machine account is built for transfer. It is stored in a different fashion.
ULONGLONG uniqueID; CHAR gamertag[16]; // SN.XXXXXXXXXXXX (the console serial number) CHAR domain[20]; // xbox.com CHAR realm[24]; // passport.net BYTE key[16];
Nonce HMAC Key
The nonce HMAC key, used to encrypt the machine account, is computed as follows:
temp_key = MD5-HMAC of the null terminated string "signaturekey" using the online key salted_nonce = "5F F3 28 92 13 8C 9C 4B 05 84 9A 3C 10 1A DB 5D" // MD5 of "02 04 00 00 00 00 00 00" nonce_hmac_key = MD5-HMAC of salted_nonce using temp_key
The key can be verified using the PA-XBOX-CLIENT-VERSION preauth:
test_signature = SHA1-HMAC of the version_string using the nonce_hmac_key // if both signatures match, the key was generated correctly
Encryption
The machine account is encrypted with the nonce HMAC key and salt 1203 using RC4-HMAC-MD5. The encrypted bytes are packed as a Kerberos EncryptedData object into a PA-DATA TYPE 203 preauthentication header in the AS-REP.
