112 lines
3.7 KiB
Go
112 lines
3.7 KiB
Go
package auth
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import (
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"crypto/rand"
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"encoding/hex"
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"fmt"
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"time"
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"golang.org/x/crypto/scrypt"
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)
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type UserId int32
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type Email string
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type DeviceId string
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type Password string
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type KDFKey string // KDF output
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type ClientSaltSeed string // part of client-side KDF input along with root password
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type ServerSalt string // server-side KDF input for accounts
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type TokenString string
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type AuthScope string
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const ScopeFull = AuthScope("*")
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// For test stubs
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type AuthInterface interface {
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// TODO maybe have a "refresh token" thing if the client won't have email available all the time?
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NewToken(UserId, DeviceId, AuthScope) (*AuthToken, error)
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}
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type Auth struct{}
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// Note that everything here is given to anybody who presents a valid
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// downloadKey and associated email. Currently these fields are safe to give
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// at that low security level, but keep this in mind as we change this struct.
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type AuthToken struct {
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Token TokenString `json:"token"`
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DeviceId DeviceId `json:"deviceId"`
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Scope AuthScope `json:"scope"`
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UserId UserId `json:"userId"`
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Expiration *time.Time `json:"expiration"`
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}
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const AuthTokenLength = 32
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func (a *Auth) NewToken(userId UserId, deviceId DeviceId, scope AuthScope) (*AuthToken, error) {
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b := make([]byte, AuthTokenLength)
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// TODO - Is this is a secure random function? (Maybe audit)
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if _, err := rand.Read(b); err != nil {
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return nil, fmt.Errorf("Error generating token: %+v", err)
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}
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return &AuthToken{
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Token: TokenString(hex.EncodeToString(b)),
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DeviceId: deviceId,
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Scope: scope,
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UserId: userId,
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// TODO add Expiration here instead of putting it in store.go. and thus redo store.go. d'oh.
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}, nil
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}
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// NOTE - not stubbing methods of structs like this. more convoluted than it's worth right now
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func (at *AuthToken) ScopeValid(required AuthScope) bool {
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// So far * is the only scope issued. Used to have more, didn't want to
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// delete this feature yet in case we add more again. We'll delete it if it's
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// of no use and ends up complicating anything.
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return at.Scope == ScopeFull || at.Scope == required
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}
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const ServerSaltLength = 16
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const ClientSaltSeedLength = 32
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// https://words.filippo.io/the-scrypt-parameters/
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func passwordScrypt(p Password, saltBytes []byte) ([]byte, error) {
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scryptN := 32768
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scryptR := 8
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scryptP := 1
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keyLen := 32
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return scrypt.Key([]byte(p), saltBytes, scryptN, scryptR, scryptP, keyLen)
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}
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// Given a password (in the same format submitted via request), generate a
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// random salt, run the password and salt thorugh the KDF, and return the salt
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// and kdf output. The result generally goes into a database.
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func (p Password) Create() (key KDFKey, salt ServerSalt, err error) {
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saltBytes := make([]byte, ServerSaltLength)
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if _, err := rand.Read(saltBytes); err != nil {
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return "", "", fmt.Errorf("Error generating salt: %+v", err)
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}
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keyBytes, err := passwordScrypt(p, saltBytes)
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if err == nil {
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key = KDFKey(hex.EncodeToString(keyBytes[:]))
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salt = ServerSalt(hex.EncodeToString(saltBytes[:]))
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}
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return
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}
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// Given a password (in the same format submitted via request), a salt, and an
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// expected kdf output, run the password and salt thorugh the KDF, and return
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// whether the result kdf output matches the kdf test output.
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// The salt and test kdf output generally come out of the database, and is used
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// to check a submitted password.
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func (p Password) Check(checkKey KDFKey, salt ServerSalt) (match bool, err error) {
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saltBytes, err := hex.DecodeString(string(salt))
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if err != nil {
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return false, fmt.Errorf("Error decoding salt from hex: %+v", err)
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}
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keyBytes, err := passwordScrypt(p, saltBytes)
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if err == nil {
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match = KDFKey(hex.EncodeToString(keyBytes[:])) == checkKey
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}
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return
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}
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