package chat import ( "encoding/hex" "fmt" "sync" "golang.org/x/crypto/argon2" ) // UserID uniquely identifies an individual user who has posted a message in a // Room. type UserID struct { // Name will be the user's chosen display name. Name string `json:"name"` // Hash will be a hex string generated from a secret only the user knows. Hash string `json:"id"` } // UserIDCalculator is used to calculate UserIDs. type UserIDCalculator struct { // Secret is used when calculating UserID Hash salts. Secret []byte // TimeCost, MemoryCost, and Threads are used as inputs to the Argon2id // algorithm which is used to generate the Hash. TimeCost, MemoryCost uint32 Threads uint8 // HashLen specifies the number of bytes the Hash should be. HashLen uint32 // Lock, if set, forces concurrent Calculate calls to occur sequentially. Lock *sync.Mutex } // NewUserIDCalculator returns a UserIDCalculator with sane defaults. func NewUserIDCalculator(secret []byte) UserIDCalculator { return UserIDCalculator{ Secret: secret, TimeCost: 15, MemoryCost: 128 * 1024, Threads: 2, HashLen: 16, Lock: new(sync.Mutex), } } // Calculate accepts a name and password and returns the calculated UserID. func (c UserIDCalculator) Calculate(name, password string) UserID { input := fmt.Sprintf("%q:%q", name, password) hashB := argon2.IDKey( []byte(input), c.Secret, // salt c.TimeCost, c.MemoryCost, c.Threads, c.HashLen, ) return UserID{ Name: name, Hash: hex.EncodeToString(hashB), } }