Difference between revisions of "Authentication"

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Minecraft 1.6 introduced a new authentication scheme called '''Yggdrasil''' which completely replaces the [[Legacy Authentication|previous authentication system]]. Mojang's other game, Scrolls, uses this method of authentication as well. Mojang has said that [https://twitter.com/KrisJelbring/status/453573406341206016 this authentication system should be used by everyone for custom logins], but [https://twitter.com/KrisJelbring/status/461390585086361600 credentials should never be collected from users].
+
Minecraft 1.6 introduced a new authentication scheme called '''Yggdrasil''' which completely replaces the [[Legacy Authentication|previous authentication system]]. Mojang's other game, Scrolls, uses this method of authentication as well. Mojang has said that [https://twitter.com/KrisJelbring/status/453573406341206016 this authentication system should be used by everyone for custom logins], but [https://twitter.com/KrisJelbring/status/461390585086361600 credentials should never be collected from users].  For newer Microsoft accounts, see [[Microsoft Authentication Scheme]].
  
 
== Request format ==
 
== Request format ==
Line 54: Line 54:
 
  | <code>ForbiddenOperationException</code>
 
  | <code>ForbiddenOperationException</code>
 
  | <code>UserMigratedException</code>
 
  | <code>UserMigratedException</code>
  | Invalid credentials. Account migrated, use e-mail as username.
+
  | Invalid credentials. Account migrated, use email as username.
 
  |  
 
  |  
 
  |-
 
  |-
Line 61: Line 61:
 
  | Invalid credentials. Invalid username or password.
 
  | Invalid credentials. Invalid username or password.
 
  |  
 
  |  
 +
|-
 +
| <code>ForbiddenOperationException</code>
 +
|
 +
| Invalid credentials.
 +
| Too many login attempts with this username recently (see <code>/authenticate</code>). Note that username and password may still be valid!
 
  |-
 
  |-
 
  | <code>ForbiddenOperationException</code>
 
  | <code>ForbiddenOperationException</code>
Line 66: Line 71:
 
  | Invalid token.
 
  | Invalid token.
 
  | <code>accessToken</code> was invalid.
 
  | <code>accessToken</code> was invalid.
 +
|-
 +
| <code>ForbiddenOperationException</code>
 +
|
 +
| Token does not exist.
 +
| <code>accessToken</code> was used in another session that was issued AFTER this session.
 
  |-
 
  |-
 
  | <code>IllegalArgumentException</code>
 
  | <code>IllegalArgumentException</code>
Line 74: Line 84:
 
  | <code>IllegalArgumentException</code>
 
  | <code>IllegalArgumentException</code>
 
  |  
 
  |  
  | credentials can not be null.
+
  | credentials is null
 
  | Username/password was not submitted.
 
  | Username/password was not submitted.
 +
|-
 +
| <code>IllegalArgumentException</code>
 +
|
 +
| Invalid salt version
 +
| ???
 
  |-
 
  |-
 
  | <code>Unsupported Media Type</code>
 
  | <code>Unsupported Media Type</code>
Line 103: Line 118:
 
                                             // unmigrated accounts
 
                                             // unmigrated accounts
 
     "password": "mojang account password",
 
     "password": "mojang account password",
     "clientToken": "client identifier"     // optional
+
     "clientToken": "client identifier",    // optional
 +
    "requestUser": true                    // optional; default: false; true adds the user object to the response
 
}
 
}
 
</syntaxhighlight>
 
</syntaxhighlight>
  
The <code>clientToken</code> should be a randomly generated identifier and must be identical for each request. In case it is omitted the server will generate a random token based on Java's [http://docs.oracle.com/javase/7/docs/api/java/util/UUID.html#toString() <code>UUID.toString()</code>] which should then be stored by the client. This will however also invalidate all previously acquired <code>accessToken</code>s for this user across all clients.
+
The <code>clientToken</code> should be a randomly generated identifier and must be identical for each request. The vanilla launcher generates a random (version 4) UUID on first run and saves it, reusing it for every subsequent request. In case it is omitted the server will generate a random token based on Java's [http://docs.oracle.com/javase/7/docs/api/java/util/UUID.html#toString() <code>UUID.toString()</code>] which should then be stored by the client. This will however also invalidate all previously acquired <code>accessToken</code>s for this user across all clients.
  
 
=== Response ===
 
=== Response ===
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<syntaxhighlight lang="javascript">
 
<syntaxhighlight lang="javascript">
 
{
 
{
     "accessToken": "random access token", // hexadecimal
+
     "user": {
     "clientToken": "client identifier",   // identical to the one received
+
        "username": "user@email.example", // will be account username for legacy accounts
     "availableProfiles": [                 // only present if the agent field was received
+
        "properties": [
 +
            {
 +
                "name": "preferredLanguage",
 +
                "value": "en-us"
 +
            },
 +
            {
 +
                "name": "registrationCountry",
 +
                "value": "country" // 2L country (e.g. US)
 +
            }
 +
        ],
 +
        "id": "hexadecimal string" // Different from the UUID, not sure what it is?
 +
    },
 +
     "clientToken": "client identifier",
 +
    "accessToken": "random access token", // hexadecimal or JSON-Web-Token (unconfirmed) [The normal accessToken can be found in the payload of the JWT (second by '.' separated part as Base64 encoded JSON object), in key "yggt"]
 +
     "availableProfiles": [
 
         {
 
         {
             "id": "profile identifier",   // hexadecimal
+
             "name": "player username",
             "name": "player name",
+
             "id": "hexadecimal string" // UUID of the account
            "legacy": true or false        // In practice, this field only appears in the response if true. Default to false.
 
 
         }
 
         }
 
     ],
 
     ],
     "selectedProfile": {                   // only present if the agent field was received
+
     "selectedProfile": {
         "id": "profile identifier",
+
         "name": "player username",
         "name": "player name",
+
         "id": "hexadecimal string" // UUID of the account
        "legacy": true or false
 
 
     }
 
     }
 
}
 
}
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Some instances in the wild have been observed of Mojang returning a flat <code>null</code> for failed refresh attempts against legacy accounts. It's not clear what the actual error tied to the null response is and it is extremely rare, but implementations should be wary of null output from the response.
 
Some instances in the wild have been observed of Mojang returning a flat <code>null</code> for failed refresh attempts against legacy accounts. It's not clear what the actual error tied to the null response is and it is extremely rare, but implementations should be wary of null output from the response.
 +
 +
This endpoint is severely rate-limited: multiple <code>/authenticate</code> requests for the same account in a short amount of time (think 3 requests in a few seconds), even with the correct password, will eventually lead to an <code>Invalid credentials.</code> response. This error clears up a few seconds later.
  
 
== Refresh ==
 
== Refresh ==
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         "id": "profile identifier",      // hexadecimal
 
         "id": "profile identifier",      // hexadecimal
 
         "name": "player name"
 
         "name": "player name"
     }
+
     },
 +
    "requestUser": true                  // optional; default: false; true adds the user object to the response
 
}
 
}
 
</syntaxhighlight>
 
</syntaxhighlight>
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<syntaxhighlight lang="javascript">
 
<syntaxhighlight lang="javascript">
 
{
 
{
     "accessToken": "random access token", // hexadecimal
+
     "accessToken": "random access token",     // hexadecimal
     "clientToken": "client identifier",   // identical to the one received
+
     "clientToken": "client identifier",       // identical to the one received
 
     "selectedProfile": {
 
     "selectedProfile": {
         "id": "profile identifier",       // hexadecimal
+
         "id": "profile identifier",           // hexadecimal
 
         "name": "player name"
 
         "name": "player name"
 +
    },
 +
    "user": {                                  // only present if requestUser was true in the request payload
 +
        "id": "user identifier",              // hexadecimal
 +
        "properties": [
 +
            {
 +
                "name": "preferredLanguage",  // might not be present for all accounts
 +
                "value": "en"                  // Java locale format (https://docs.oracle.com/javase/8/docs/api/java/util/Locale.html#toString--)
 +
            },
 +
            {
 +
                "name": "twitch_access_token", // only present if a twitch account is associated (see https://account.mojang.com/me/settings)
 +
                "value": "twitch oauth token"  // OAuth 2.0 Token; alphanumerical; e.g. https://api.twitch.tv/kraken?oauth_token=[...]
 +
                                              // the Twitch API is documented here: https://github.com/justintv/Twitch-API
 +
            }
 +
        ]
 
     }
 
     }
 
}
 
}
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== Validate ==
 
== Validate ==
  
Checks if an <code>accessToken</code> is a valid session token with a currently-active session. Note: this method will not respond successfully to all currently-logged-in sessions, just the most recently-logged-in for each user.  It is intended to be used by servers to validate that a user should be connecting (and reject users who have logged in elsewhere since starting Minecraft), ''not'' to auth that a particular session token is valid for authentication purposes. To authenticate a user by session token, use the refresh verb and catch resulting errors.
+
Checks if an <code>accessToken</code> is usable for authentication with a Minecraft server. The Minecraft Launcher (as of version 1.6.13) calls this endpoint on startup to verify that its saved token is still usable, and calls <code>/refresh</code> if this returns an error.
 +
 
 +
Note that an <code>accessToken</code> may be unusable for authentication with a Minecraft server, but still be good enough for <code>/refresh</code>. This mainly happens when one has used another client (e.g. played Minecraft on another PC with the same account). It seems only the most recently obtained <code>accessToken</code> for a given account can reliably be used for authentication (the next-to-last token also seems to remain valid, but don't rely on it).
 +
 
 +
<code>/validate</code> may be called with or without a <code>clientToken</code>. If a <code>clientToken</code> is provided, it should match the one used to obtain the <code>accessToken</code>. The Minecraft Launcher does send a <code>clientToken</code> to <code>/validate</code>.
  
 
=== Endpoint ===
 
=== Endpoint ===
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<syntaxhighlight lang="javascript">
 
<syntaxhighlight lang="javascript">
 
{
 
{
     "accessToken": "valid accessToken"
+
     "accessToken": "valid accessToken",
 +
    "clientToken": "associated clientToken" // optional, see above
 
}
 
}
 
</syntaxhighlight>
 
</syntaxhighlight>
Line 190: Line 240:
 
=== Response ===
 
=== Response ===
  
Returns an empty payload if successful.
+
Returns an empty payload (<code>204 No Content</code>) if successful, an error JSON with status <code>403 Forbidden</code> otherwise.
  
 
== Signout ==
 
== Signout ==
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See [[Protocol Encryption#Authentication]]
 
See [[Protocol Encryption#Authentication]]
 +
 +
== Examples ==
 +
 +
[https://github.com/iBuyMountainDew/yggdrasil Kotlin] | Full Yggdrasil wrapper in Kotlin.
 +
 +
[https://github.com/Kronos666/mclaunch-util-lib Java] | Legacy full Yggdrasil wrapper in Java.
  
 
[[Category:Protocol Details]]
 
[[Category:Protocol Details]]
 
[[Category:Minecraft Modern]]
 
[[Category:Minecraft Modern]]

Latest revision as of 22:22, 3 April 2021

Minecraft 1.6 introduced a new authentication scheme called Yggdrasil which completely replaces the previous authentication system. Mojang's other game, Scrolls, uses this method of authentication as well. Mojang has said that this authentication system should be used by everyone for custom logins, but credentials should never be collected from users. For newer Microsoft accounts, see Microsoft Authentication Scheme.

Request format

All requests to Yggdrasil are made to the following server:

https://authserver.mojang.com

Further, they are expected to fulfill the following rules:

  • Are POST requests
  • Have the Content-Type header set to application/json
  • Contain a JSON-encoded dictionary as payload

If a request was successful the server will respond with:

  • Status code 200
  • A JSON-encoded dictionary according to the specifications below

If however a request fails, the server will respond with:

{
    "error": "Short description of the error",
    "errorMessage": "Longer description which can be shown to the user",
    "cause": "Cause of the error" // optional
}

Errors

These are some of the errors that can be encountered:

Error Cause Error message Notes
Method Not Allowed The method specified in the request is not allowed for the resource identified by the request URI Something other than a POST request was received.
Not Found The server has not found anything matching the request URI Non-existing endpoint was called.
ForbiddenOperationException UserMigratedException Invalid credentials. Account migrated, use email as username.
ForbiddenOperationException Invalid credentials. Invalid username or password.
ForbiddenOperationException Invalid credentials. Too many login attempts with this username recently (see /authenticate). Note that username and password may still be valid!
ForbiddenOperationException Invalid token. accessToken was invalid.
ForbiddenOperationException Token does not exist. accessToken was used in another session that was issued AFTER this session.
IllegalArgumentException Access token already has a profile assigned. Selecting profiles isn't implemented yet.
IllegalArgumentException credentials is null Username/password was not submitted.
IllegalArgumentException Invalid salt version ???
Unsupported Media Type The server is refusing to service the request because the entity of the request is in a format not supported by the requested resource for the requested method Data was not submitted as application/json

Authenticate

Authenticates a user using their password.

Endpoint

/authenticate

Payload

{
    "agent": {                              // defaults to Minecraft
        "name": "Minecraft",                // For Mojang's other game Scrolls, "Scrolls" should be used
        "version": 1                        // This number might be increased
                                            // by the vanilla client in the future
    },
    "username": "mojang account name",      // Can be an email address or player name for
                                            // unmigrated accounts
    "password": "mojang account password",
    "clientToken": "client identifier",     // optional
    "requestUser": true                     // optional; default: false; true adds the user object to the response
}

The clientToken should be a randomly generated identifier and must be identical for each request. The vanilla launcher generates a random (version 4) UUID on first run and saves it, reusing it for every subsequent request. In case it is omitted the server will generate a random token based on Java's UUID.toString() which should then be stored by the client. This will however also invalidate all previously acquired accessTokens for this user across all clients.

Response

{
    "user": {
        "username": "user@email.example", // will be account username for legacy accounts
        "properties": [
            {
                "name": "preferredLanguage",
                "value": "en-us"
            },
            {
                "name": "registrationCountry",
                "value": "country" // 2L country (e.g. US)
            }
        ],
        "id": "hexadecimal string" // Different from the UUID, not sure what it is?
    },
    "clientToken": "client identifier",
    "accessToken": "random access token", // hexadecimal or JSON-Web-Token (unconfirmed) [The normal accessToken can be found in the payload of the JWT (second by '.' separated part as Base64 encoded JSON object), in key "yggt"]
    "availableProfiles": [
        {
            "name": "player username",
            "id": "hexadecimal string" // UUID of the account
        }
    ],
    "selectedProfile": {
        "name": "player username",
        "id": "hexadecimal string" // UUID of the account
    }
}

Note: If a user wishes to stay logged in on their computer you are strongly advised to store the received accessToken instead of the password itself.

Currently each account will only have one single profile, multiple profiles per account are however planned in the future. If a user attempts to log into a valid Mojang account with no attached Minecraft license, the authentication will be successful, but the response will not contain a selectedProfile field, and the availableProfiles array will be empty.

Some instances in the wild have been observed of Mojang returning a flat null for failed refresh attempts against legacy accounts. It's not clear what the actual error tied to the null response is and it is extremely rare, but implementations should be wary of null output from the response.

This endpoint is severely rate-limited: multiple /authenticate requests for the same account in a short amount of time (think 3 requests in a few seconds), even with the correct password, will eventually lead to an Invalid credentials. response. This error clears up a few seconds later.

Refresh

Refreshes a valid accessToken. It can be used to keep a user logged in between gaming sessions and is preferred over storing the user's password in a file (see lastlogin).

Endpoint

/refresh

Payload

{
    "accessToken": "valid accessToken",
    "clientToken": "client identifier",  // This needs to be identical to the one used
                                         // to obtain the accessToken in the first place
    "selectedProfile": {                 // optional; sending it will result in an error
        "id": "profile identifier",      // hexadecimal
        "name": "player name"
    },
    "requestUser": true                  // optional; default: false; true adds the user object to the response
}

Note: The provided accessToken gets invalidated.

Response

{
    "accessToken": "random access token",      // hexadecimal
    "clientToken": "client identifier",        // identical to the one received
    "selectedProfile": {
        "id": "profile identifier",            // hexadecimal
        "name": "player name"
    },
    "user": {                                  // only present if requestUser was true in the request payload
        "id": "user identifier",               // hexadecimal
        "properties": [
            {
                "name": "preferredLanguage",   // might not be present for all accounts
                "value": "en"                  // Java locale format (https://docs.oracle.com/javase/8/docs/api/java/util/Locale.html#toString--)
            },
            {
                "name": "twitch_access_token", // only present if a twitch account is associated (see https://account.mojang.com/me/settings)
                "value": "twitch oauth token"  // OAuth 2.0 Token; alphanumerical; e.g. https://api.twitch.tv/kraken?oauth_token=[...]
                                               // the Twitch API is documented here: https://github.com/justintv/Twitch-API
            }
        ]
    }
}

Validate

Checks if an accessToken is usable for authentication with a Minecraft server. The Minecraft Launcher (as of version 1.6.13) calls this endpoint on startup to verify that its saved token is still usable, and calls /refresh if this returns an error.

Note that an accessToken may be unusable for authentication with a Minecraft server, but still be good enough for /refresh. This mainly happens when one has used another client (e.g. played Minecraft on another PC with the same account). It seems only the most recently obtained accessToken for a given account can reliably be used for authentication (the next-to-last token also seems to remain valid, but don't rely on it).

/validate may be called with or without a clientToken. If a clientToken is provided, it should match the one used to obtain the accessToken. The Minecraft Launcher does send a clientToken to /validate.

Endpoint

/validate

Payload

{
    "accessToken": "valid accessToken",
    "clientToken": "associated clientToken" // optional, see above
}

Response

Returns an empty payload (204 No Content) if successful, an error JSON with status 403 Forbidden otherwise.

Signout

Invalidates accessTokens using an account's username and password.

Endpoint

/signout

Payload

{
    "username": "mojang account name",
    "password": "mojang account password"
}

Response

Returns an empty payload if successful.

Invalidate

Invalidates accessTokens using a client/access token pair.

Endpoint

/invalidate

Payload

{
    "accessToken": "valid accessToken",
    "clientToken": "client identifier"   // This needs to be identical to the one used
                                         // to obtain the accessToken in the first place
}

Response

Returns an empty payload if successful.

Joining a Server

See Protocol Encryption#Authentication

Examples

Kotlin | Full Yggdrasil wrapper in Kotlin.

Java | Legacy full Yggdrasil wrapper in Java.