Unfortunately, there is no proper documentation across the REST API and the way that you can get the Space Admin Permission via this. However, I believe you are able to use the old JSON-RPC API to get the list of the space permissions. It's accessible via:
http://<confluence-url>/rpc/json-rpc/confluenceservice-v2/getSpacePermissionSets
It technically returns the response like following:
[
{
"type": "SETSPACEPERMISSIONS",
"spacePermissions": [
{
"type": "SETSPACEPERMISSIONS",
"userName": null,
"groupName": "confluence-administrators"
}
]
},
{
"type": "EXPORTSPACE",
"spacePermissions": [
{
"type": "EXPORTSPACE",
"userName": null,
"groupName": null
},
{
"type": "EXPORTSPACE",
"userName": null,
"groupName": "confluence-users"
},
{
"type": "EXPORTSPACE",
"userName": null,
"groupName": "confluence-administrators"
}
]
},
{
"type": "SETPAGEPERMISSIONS",
"spacePermissions": [
{
"type": "SETPAGEPERMISSIONS",
"userName": null,
"groupName": "confluence-users"
},
{
"type": "SETPAGEPERMISSIONS",
"userName": null,
"groupName": "confluence-administrators"
}
]
},
{
"type": "REMOVEMAIL",
"spacePermissions": [
{
"type": "REMOVEMAIL",
"userName": null,
"groupName": "confluence-users"
},
{
"type": "REMOVEMAIL",
"userName": null,
"groupName": "confluence-administrators"
},
{
"type": "REMOVEMAIL",
"userName": null,
"groupName": null
}
]
},
{
"type": "REMOVEBLOG",
"spacePermissions": [
{
"type": "REMOVEBLOG",
"userName": null,
"groupName": null
},
{
"type": "REMOVEBLOG",
"userName": null,
"groupName": "confluence-users"
},
{
"type": "REMOVEBLOG",
"userName": null,
"groupName": "confluence-administrators"
}
]
},
{
"type": "EXPORTPAGE",
"spacePermissions": [
{
"type": "EXPORTPAGE",
"userName": null,
"groupName": null
},
{
"type": "EXPORTPAGE",
"userName": null,
"groupName": "confluence-administrators"
},
{
"type": "EXPORTPAGE",
"userName": null,
"groupName": "confluence-users"
}
]
},
{
"type": "REMOVEATTACHMENT",
"spacePermissions": [
{
"type": "REMOVEATTACHMENT",
"userName": null,
"groupName": null
},
{
"type": "REMOVEATTACHMENT",
"userName": null,
"groupName": "confluence-administrators"
},
{
"type": "REMOVEATTACHMENT",
"userName": null,
"groupName": "confluence-users"
}
]
},
{
"type": "CREATEATTACHMENT",
"spacePermissions": [
{
"type": "CREATEATTACHMENT",
"userName": null,
"groupName": "confluence-users"
},
{
"type": "CREATEATTACHMENT",
"userName": null,
"groupName": null
},
{
"type": "CREATEATTACHMENT",
"userName": null,
"groupName": "confluence-administrators"
}
]
},
{
"type": "VIEWSPACE",
"spacePermissions": [
{
"type": "VIEWSPACE",
"userName": null,
"groupName": "confluence-administrators"
},
{
"type": "VIEWSPACE",
"userName": null,
"groupName": null
},
{
"type": "VIEWSPACE",
"userName": null,
"groupName": "confluence-users"
}
]
},
{
"type": "EDITBLOG",
"spacePermissions": [
{
"type": "EDITBLOG",
"userName": null,
"groupName": null
},
{
"type": "EDITBLOG",
"userName": null,
"groupName": "confluence-users"
},
{
"type": "EDITBLOG",
"userName": null,
"groupName": "confluence-administrators"
}
]
},
{
"type": "REMOVEPAGE",
"spacePermissions": [
{
"type": "REMOVEPAGE",
"userName": null,
"groupName": "confluence-administrators"
},
{
"type": "REMOVEPAGE",
"userName": null,
"groupName": null
},
{
"type": "REMOVEPAGE",
"userName": null,
"groupName": "confluence-users"
}
]
},
{
"type": "REMOVECOMMENT",
"spacePermissions": [
{
"type": "REMOVECOMMENT",
"userName": null,
"groupName": null
},
{
"type": "REMOVECOMMENT",
"userName": null,
"groupName": "confluence-users"
},
{
"type": "REMOVECOMMENT",
"userName": null,
"groupName": "confluence-administrators"
}
]
},
{
"type": "EDITSPACE",
"spacePermissions": [
{
"type": "EDITSPACE",
"userName": null,
"groupName": "confluence-users"
},
{
"type": "EDITSPACE",
"userName": null,
"groupName": "confluence-administrators"
},
{
"type": "EDITSPACE",
"userName": null,
"groupName": null
}
]
},
{
"type": "COMMENT",
"spacePermissions": [
{
"type": "COMMENT",
"userName": null,
"groupName": "confluence-users"
},
{
"type": "COMMENT",
"userName": null,
"groupName": "confluence-administrators"
},
{
"type": "COMMENT",
"userName": null,
"groupName": null
}
]
}
]
If you don't have any limitation and you are able to run the query against the database, you can also use following Query:
SELECT s.SPACENAME, u.username FROM SPACES s
JOIN SPACEPERMISSIONS p ON s.SPACEID = p.SPACEID
JOIN user_mapping u ON p.PERMUSERNAME = u.user_key
WHERE p.PERMTYPE = 'SETSPACEPERMISSIONS';
Above query returns the list of the space administrators for all spaces across your instance.