Difference between revisions of "Legacy Mojang Authentication"

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The minecraft client and server communicate with Mojang to validate player sessions. This page describes some of the operations.
+
With the release of Minecraft 1.6, Mojang introduced a new authentication system called '''Yggdrasil''', which replaced the previous [[Legacy Authentication|Legacy authentication system]]. This authentication system is also used in Mojang's other game, Scrolls. According to Mojang, the Yggdrasil authentication system should be adopted by developers for custom login implementation, but they strongly advise against collecting credentials from users. For those utilizing newer Microsoft accounts, there is an alternative authentication scheme available called the [[Microsoft Authentication Scheme|Microsoft authentication scheme]].
  
== Authentication ==
+
== Requests ==
 +
The Yggdrasil authentication system requests are made to the following server:
  
Minecraft 1.6 introduced a new authentication scheme called Yggdrasil which completely replaces the [[Legacy_Authentication|previous authentication system]].
+
https://authserver.mojang.com
  
=== Request format ===
+
To ensure successful requests, they must adhere to the following guidelines:
 +
* Use a <code>POST</code> request method
 +
* Include a <code>Content-Type</code> header set to <code>application/json</code>
 +
* Contain a [[wikipedia:JSON|JSON]]-encoded dictionary as payload
  
All requests to Yggdrasil are made to the following server:
+
In the event of a successful request, the server will return:
 +
* A <code>2XX</code> [[wikipedia:List of HTTP status codes|HTTP status code]] to indicate success
 +
* An empty payload or a [[wikipedia:JSON|JSON]]-encoded dictionary as specified in the API documentation
  
  https://authserver.mojang.com
+
In the case of a failed request, the server will respond with:
 +
* An [[wikipedia:List of HTTP status codes|HTTP status code]] other than <code>2XX</code> to indicate failure
 +
* A [[wikipedia:JSON|JSON]]-encoded dictionary following the format below:
 +
<syntaxhighlight lang="javascript">
 +
{
 +
    "error": "Short description of the error",
 +
    "cause": "Cause of the error" // optional
 +
    "errorMessage": "Longer description which can be shown to the user",
 +
}
 +
</syntaxhighlight>
 +
 
 +
== Errors ==
 +
The following are examples of error scenarios that may occur during the use of the Yggdrasil authentication system:
 +
 
 +
{| class="wikitable"
 +
|-
 +
! STATUS
 +
! error
 +
! cause
 +
! errorMessage
 +
! NOTES
 +
|-
 +
| <code>415 Unsupported Media Type</code>
 +
| <code>Unsupported Media Type</code>
 +
|
 +
| 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
 +
| An attempt to send a POST request with incorrect request headers to any endpoint.
 +
|-
 +
| <code>405 Method Not Allowed</code>
 +
| <code>Method Not Allowed</code>
 +
|
 +
| The method specified in the request is not allowed for the resource identified by the request URI
 +
| An attempt to use a request method other than <code>POST</code> to access any of the endpoints.
 +
|-
 +
| <code>404 Not Found</code>
 +
| <code>Not Found</code>
 +
|
 +
| The server has not found anything matching the request URI
 +
| An attempt to send a request to a non-existent endpoint.
 +
|-
 +
| <code>410 Gone</code>
 +
| <code>GoneException</code>
 +
|
 +
| Migrated
 +
| A successful attempt to sign in using a migrated Mojang account.
 +
|-
 +
| <code>403 Forbidden</code>
 +
| <code>ForbiddenOperationException</code>
 +
|
 +
| Forbidden
 +
| An attempt to sign in using empty or insufficiently short credentials.
 +
|-
 +
| <code>403 Forbidden</code>
 +
| <code>ForbiddenOperationException</code>
 +
|
 +
| Invalid credentials. Invalid username or password.
 +
| Either a successful attempt to sign in using an account with excessive login attempts or an unsuccessful attempt to sign in using a non-existent account.
 +
|-
 +
| <code>403 Forbidden</code>
 +
| <code>ForbiddenOperationException</code>
 +
|
 +
| Invalid credentials. Legacy account is non-premium account.
 +
| An unsuccessful attempt to sign in using a Legacy account without a valid Minecraft purchase.
 +
|-
 +
| <code>403 Forbidden</code>
 +
| <code>ForbiddenOperationException</code>
 +
| <code>UserMigratedException</code>
 +
| Invalid credentials. Account migrated, use email as username.
 +
| An unsuccessful attempt to sign in using a migrated Legacy account.
 +
|-
 +
| <code>403 Forbidden</code>
 +
| <code>TooManyRequestsException</code>
 +
|
 +
| Token does not exist
 +
| An attempt to refresh an access token that has been invalidated, no longer exists, or has been erased.
 +
|-
 +
| <code>403 Forbidden</code>
 +
| <code>ForbiddenOperationException</code>
 +
|
 +
| Invalid token
 +
| An attempt to validate an access token obtained from the <code>/authenticate</code> endpoint that has expired or become invalid.
 +
|-
 +
| <code>429 Too Many Requests</code>
 +
| <code>ForbiddenOperationException</code>
 +
|
 +
| Invalid token.
 +
| An attempt to validate an access token obtained from the <code>/authenticate</code> endpoint that has expired or become invalid while under rate-limiting conditions.
 +
|}
  
Further, they are expected to fulfill the following rules:
+
== Authenticate ==
  
* Are <code>POST</code> requests
+
Authenticates a user using their password.
* Have the <code>Content-Type</code> header set to <code>application/json</code>
 
* Contain a [http://json.org JSON]-encoded dictionary as payload
 
  
If a request was successful the server will respond with:
+
=== Endpoint ===
  
* Status code <code>200</code>
+
/authenticate
* A [http://json.org JSON]-encoded dictionary according to the specifications below
 
  
If however a request fails, the server will respond with:
+
=== Payload ===
  
* An appropriate, non-200 [http://en.wikipedia.org/wiki/List_of_HTTP_status_codes HTTP status code]
 
* A [http://json.org JSON]-encoded dictionary following this format:
 
 
<syntaxhighlight lang="javascript">
 
<syntaxhighlight lang="javascript">
 
{
 
{
  "error": "Short description of the error",
+
    "agent": {                              // defaults to Minecraft
  "errorMessage": "Longer description which can be shown to the user",
+
        "name": "Minecraft",                // For Mojang's other game Scrolls, "Scrolls" should be used
  "cause": "Cause of the error"       // optional
+
        "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
 
}
 
}
 
</syntaxhighlight>
 
</syntaxhighlight>
  
=== Session ID ===
+
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 ===
  
Whenever a Mojang service requires a session ID, you can simply combine a valid <code>accessToken</code> with a profile identifier as follows:
+
<syntaxhighlight lang="javascript">
 +
{
 +
    "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" // This is the remoteID for the user
 +
    },
 +
    "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
 +
    }
 +
}
 +
</syntaxhighlight>
  
  token:<accessToken>:<profile ID>
+
'''Note:''' If a user wishes to stay logged in on their computer you are strongly advised to store the received <code>accessToken</code> instead of the password itself.
  
=== Authenticate ===
+
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 <code>selectedProfile</code> field, and the <code>availableProfiles</code> array will be empty.
  
This method is used whenever a user tries to log in using his password.
+
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.
  
==== Endpoint ====
+
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.
  /authenticate
 
  
==== Payload ====
+
== Refresh ==
 +
 
 +
Refreshes a valid <code>accessToken</code>. 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 ===
 
<syntaxhighlight lang="javascript">
 
<syntaxhighlight lang="javascript">
 
{
 
{
  "agent": {                            // optional
+
     "accessToken": "valid accessToken",
     "name": "Minecraft",                 // So far this is the only encountered value
+
     "clientToken": "client identifier",  // This needs to be identical to the one used
     "version": 1                        // This number might be increased
+
                                         // to obtain the accessToken in the first place
                                         // by the vanilla client in the future
+
    "selectedProfile": {                // optional; sending it will result in an error
  },
+
        "id": "profile identifier",     // hexadecimal
  "username": "mojang account name",     // Can be an email address or player name for
+
        "name": "player name"
                                        // unmigrated accounts
+
    },
  "password": "mojang account password",
+
    "requestUser": true                  // optional; default: false; true adds the user object to the response
  "clientToken": "client identifier"    // optional
 
 
}
 
}
 
</syntaxhighlight>
 
</syntaxhighlight>
  
The <code>clientToken</code> should be a randomly generated identifier and must be identical for each request.
+
Note: The provided <code>accessToken</code> gets invalidated.
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() UUID.toString()] 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 ====
 
 
<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
  "availableProfiles": [                // only present if the agent field was received
+
    "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
 +
        "username": "user@email.example",      // email for Mojang accounts or account username for legacy Minecraft accounts
 +
        "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
 +
            }
 +
        ]
 
     }
 
     }
  ],
+
}
  "selectedProfile": {                  // only present if the agent field was received
+
</syntaxhighlight>
     "id": "profile identifier",
+
 
     "name": "player name"
+
== Validate ==
  }
+
 
}
+
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 ===
 +
 
 +
/validate
 +
 
 +
=== Payload ===
 +
 
 +
<syntaxhighlight lang="javascript">
 +
{
 +
     "accessToken": "valid accessToken",
 +
     "clientToken": "associated clientToken" // optional, see above
 +
}
 
</syntaxhighlight>
 
</syntaxhighlight>
'''Note:''' If a user wishes to stay logged in on his computer you are strongly advised to store the received <code>accessToken</code> instead of the password itself.
 
  
Currently each account will only have one single profile, multiple profiles per account are however planned in the future.
+
=== Response ===
 +
 
 +
Returns an empty payload (<code>204 No Content</code>) if successful, an error JSON with status <code>403 Forbidden</code> otherwise.
 +
 
 +
== Signout ==
  
=== Refresh ===
+
Invalidates <code>accessToken</code>s using an account's username and password.
  
This method is used to refresh an expired but valid <code>accessToken</code>. It can be uses to keep a user logged in between gaming sessions and is preferred over storing the user's password in a file (see [[lastlogin]]).
+
=== Endpoint ===
  
==== Endpoint ====
+
/signout
  /refresh
+
 
 +
=== Payload ===
  
==== Payload ====
 
 
<syntaxhighlight lang="javascript">
 
<syntaxhighlight lang="javascript">
 
{
 
{
  "accessToken": "valid accessToken",
+
    "username": "mojang account name",
  "clientToken": "client identifier"     // This needs to be identical to the one used
+
    "password": "mojang account password"
                                        // to obtain the accessToken in the first place
 
 
}
 
}
 
</syntaxhighlight>
 
</syntaxhighlight>
  
Note: The provided <code>accessToken</code> gets invalidated.
+
=== Response ===
 +
 
 +
Returns an empty payload if successful.
 +
 
 +
== Invalidate ==
 +
 
 +
Invalidates <code>accessToken</code>s using a client/access token pair.
 +
 
 +
=== Endpoint ===
 +
 
 +
/invalidate
 +
 
 +
=== Payload ===
  
==== Response ====
 
 
<syntaxhighlight lang="javascript">
 
<syntaxhighlight lang="javascript">
 
{
 
{
  "accessToken": "random access token", // hexadecimal
+
    "accessToken": "valid accessToken",
  "clientToken": "client identifier",    // identical to the one received
+
    "clientToken": "client identifier"   // This needs to be identical to the one used
  "selectedProfile": {
+
                                        // to obtain the accessToken in the first place
    "id": "profile identifier",          // hexadecimal
+
}
    "name": "player name"
 
  }
 
}
 
 
</syntaxhighlight>
 
</syntaxhighlight>
  
 +
=== Response ===
 +
 +
Returns an empty payload if successful.
  
 
== Joining a Server ==
 
== Joining a Server ==
  
See [[Protocol Encryption]] for details on encrypting connections.
+
See [[Protocol Encryption#Authentication]]
 
 
=== Client operation ===
 
  
# Client connects to server
+
== Examples ==
# Client sends a [[Protocol#0x02|0x02 handshake]] containing the current player name
 
# Client receives an [[Protocol#0xFD|0xFD encryption request]] with the server's public key and four verification bytes.
 
# Client generates a symmetric key.
 
# Client sends a HTTP request to
 
#:<pre>http://session.minecraft.net/game/joinserver.jsp?user=<player name>&sessionId=<session id>&serverId=<server hash></pre>
 
#:Note: See the [[#Session ID|Session ID]] section on how the <code>&lt;session id&gt;</code> is generated.
 
#:If the response is '''OK''' then continue, otherwise stop
 
# Client sends [[Protocol#0xFC|0xFC encryption response]] - client encrypts shared secret and verification token with the server's public key
 
# Server checks validity and sends [[Protocol#0xFC|0xFC encryption response]] with two empty arrays
 
# Both sides enable AES/CFB2 encryption using the shared secret generated by the client
 
# Client sends [[Protocol#0xCD|0xCD client status]] with a payload of 0 (ready to spawn)
 
# Server sends [[Protocol#0x01|0x01 login]]
 
# ... receive map chunks, etc...
 
  
=== Server operation ===
+
[https://github.com/iBuyMountainDew/yggdrasil Kotlin] | Full Yggdrasil wrapper in Kotlin.
  
# Server generates a 1024-bit RSA keypair.
+
[https://github.com/Kronos666/mclaunch-util-lib Java] | Legacy full Yggdrasil wrapper in Java.
# ...
 
# Server answers TCP connection request and receives a [[Protocol#0x02|0x02 handshake]] from the client.
 
# Server sends [[Protocol#0xFD|0xFD encryption request]] with its public key and a verification token.
 
# Server receives [[Protocol#0xFC|0xFC encryption response]] from client and decrypts the shared secret.
 
# Server verifies the validity of the verification token. If this isn't verified, it kicks the client.
 
# Server sends a HTTP request to
 
#:<pre>http://session.minecraft.net/game/checkserver.jsp?user=<username>&serverId=<server hash></pre>
 
#:If it returns '''YES''' then the client is authenticated and allowed to join. Otherwise the client will/should be [[Protocol#0xFF|kicked]] with “Failed to verify username!”
 
# Server sends a [[Protocol#0xFC|0xFC encryption response]] packet with two empty arrays.
 
# Both sides enable AES/CFB2 encryption.
 
# Server receives [[Protocol#0xCD|0xCD client status]] with a payload of , indicating "ready to spawn"
 
# Server sends [[Protocol#0x01|0x01 login]]
 
# ... send map chunks, etc...
 
  
[[Category:Protocol Details]]
 
 
[[Category:Minecraft Modern]]
 
[[Category:Minecraft Modern]]

Latest revision as of 18:56, 26 February 2024

With the release of Minecraft 1.6, Mojang introduced a new authentication system called Yggdrasil, which replaced the previous Legacy authentication system. This authentication system is also used in Mojang's other game, Scrolls. According to Mojang, the Yggdrasil authentication system should be adopted by developers for custom login implementation, but they strongly advise against collecting credentials from users. For those utilizing newer Microsoft accounts, there is an alternative authentication scheme available called the Microsoft authentication scheme.

Requests

The Yggdrasil authentication system requests are made to the following server:

https://authserver.mojang.com

To ensure successful requests, they must adhere to the following guidelines:

  • Use a POST request method
  • Include a Content-Type header set to application/json
  • Contain a JSON-encoded dictionary as payload

In the event of a successful request, the server will return:

  • A 2XX HTTP status code to indicate success
  • An empty payload or a JSON-encoded dictionary as specified in the API documentation

In the case of a failed request, the server will respond with:

  • An HTTP status code other than 2XX to indicate failure
  • A JSON-encoded dictionary following the format below:
{
    "error": "Short description of the error",
    "cause": "Cause of the error" // optional
    "errorMessage": "Longer description which can be shown to the user",
}

Errors

The following are examples of error scenarios that may occur during the use of the Yggdrasil authentication system:

STATUS error cause errorMessage NOTES
415 Unsupported Media Type 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 An attempt to send a POST request with incorrect request headers to any endpoint.
405 Method Not Allowed Method Not Allowed The method specified in the request is not allowed for the resource identified by the request URI An attempt to use a request method other than POST to access any of the endpoints.
404 Not Found Not Found The server has not found anything matching the request URI An attempt to send a request to a non-existent endpoint.
410 Gone GoneException Migrated A successful attempt to sign in using a migrated Mojang account.
403 Forbidden ForbiddenOperationException Forbidden An attempt to sign in using empty or insufficiently short credentials.
403 Forbidden ForbiddenOperationException Invalid credentials. Invalid username or password. Either a successful attempt to sign in using an account with excessive login attempts or an unsuccessful attempt to sign in using a non-existent account.
403 Forbidden ForbiddenOperationException Invalid credentials. Legacy account is non-premium account. An unsuccessful attempt to sign in using a Legacy account without a valid Minecraft purchase.
403 Forbidden ForbiddenOperationException UserMigratedException Invalid credentials. Account migrated, use email as username. An unsuccessful attempt to sign in using a migrated Legacy account.
403 Forbidden TooManyRequestsException Token does not exist An attempt to refresh an access token that has been invalidated, no longer exists, or has been erased.
403 Forbidden ForbiddenOperationException Invalid token An attempt to validate an access token obtained from the /authenticate endpoint that has expired or become invalid.
429 Too Many Requests ForbiddenOperationException Invalid token. An attempt to validate an access token obtained from the /authenticate endpoint that has expired or become invalid while under rate-limiting conditions.

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" // This is the remoteID for the user
    },
    "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
        "username": "user@email.example",      // email for Mojang accounts or account username for legacy Minecraft accounts
        "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.