117 lines
3.7 KiB
Go
117 lines
3.7 KiB
Go
// Copyright (c) 2026 Probo Inc <hello@probo.com>.
|
|
//
|
|
// Permission to use, copy, modify, and/or distribute this software for any
|
|
// purpose with or without fee is hereby granted, provided that the above
|
|
// copyright notice and this permission notice appear in all copies.
|
|
//
|
|
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
|
|
// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
|
|
// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
|
|
// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
|
|
// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
|
|
// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
|
|
// PERFORMANCE OF THIS SOFTWARE.
|
|
|
|
package authn
|
|
|
|
import (
|
|
"crypto/hmac"
|
|
"crypto/sha256"
|
|
"encoding/base64"
|
|
"errors"
|
|
"fmt"
|
|
"strconv"
|
|
"strings"
|
|
"time"
|
|
)
|
|
|
|
const sessionTransferTTL = 60 * time.Second
|
|
|
|
var (
|
|
ErrInvalidSessionTransferToken = errors.New("invalid session transfer token")
|
|
ErrSessionTransferTokenExpired = errors.New("session transfer token expired")
|
|
)
|
|
|
|
// SignSessionTransfer creates a signed, time-limited token containing a
|
|
// session ID and the intended redirect URL. The token format is
|
|
// base64(sessionID:continueURL:timestamp).signature.
|
|
func SignSessionTransfer(sessionID string, continueURL string, secret string) (string, error) {
|
|
if secret == "" {
|
|
return "", fmt.Errorf("cannot sign session transfer token: secret is empty")
|
|
}
|
|
|
|
payload := sessionID + ":" + continueURL + ":" + strconv.FormatInt(time.Now().Unix(), 10)
|
|
encoded := base64.RawURLEncoding.EncodeToString([]byte(payload))
|
|
|
|
mac := hmac.New(sha256.New, []byte(secret))
|
|
mac.Write([]byte(encoded))
|
|
sig := base64.RawURLEncoding.EncodeToString(mac.Sum(nil))
|
|
|
|
return encoded + "." + sig, nil
|
|
}
|
|
|
|
// SessionTransferClaims holds the verified claims from a session transfer
|
|
// token.
|
|
type SessionTransferClaims struct {
|
|
SessionID string
|
|
ContinueURL string
|
|
}
|
|
|
|
// VerifySessionTransfer verifies a session transfer token and returns
|
|
// the session ID and continue URL if the token is valid and not expired.
|
|
func VerifySessionTransfer(token string, secret string) (SessionTransferClaims, error) {
|
|
if secret == "" {
|
|
return SessionTransferClaims{}, fmt.Errorf("cannot verify session transfer token: secret is empty")
|
|
}
|
|
|
|
parts := strings.SplitN(token, ".", 2)
|
|
if len(parts) != 2 {
|
|
return SessionTransferClaims{}, ErrInvalidSessionTransferToken
|
|
}
|
|
|
|
encoded, sig := parts[0], parts[1]
|
|
|
|
mac := hmac.New(sha256.New, []byte(secret))
|
|
mac.Write([]byte(encoded))
|
|
expectedSig := base64.RawURLEncoding.EncodeToString(mac.Sum(nil))
|
|
|
|
if !hmac.Equal([]byte(sig), []byte(expectedSig)) {
|
|
return SessionTransferClaims{}, ErrInvalidSessionTransferToken
|
|
}
|
|
|
|
payload, err := base64.RawURLEncoding.DecodeString(encoded)
|
|
if err != nil {
|
|
return SessionTransferClaims{}, ErrInvalidSessionTransferToken
|
|
}
|
|
|
|
// Payload format: sessionID:continueURL:timestamp
|
|
// Use LastIndex to find the timestamp separator (timestamp is always last).
|
|
idx := strings.LastIndex(string(payload), ":")
|
|
if idx < 0 {
|
|
return SessionTransferClaims{}, ErrInvalidSessionTransferToken
|
|
}
|
|
|
|
tsStr := string(payload[idx+1:])
|
|
rest := string(payload[:idx])
|
|
|
|
ts, err := strconv.ParseInt(tsStr, 10, 64)
|
|
if err != nil {
|
|
return SessionTransferClaims{}, ErrInvalidSessionTransferToken
|
|
}
|
|
|
|
if time.Since(time.Unix(ts, 0)) > sessionTransferTTL {
|
|
return SessionTransferClaims{}, ErrSessionTransferTokenExpired
|
|
}
|
|
|
|
// Split rest into sessionID and continueURL.
|
|
before, after, ok := strings.Cut(rest, ":")
|
|
if !ok {
|
|
return SessionTransferClaims{}, ErrInvalidSessionTransferToken
|
|
}
|
|
|
|
return SessionTransferClaims{
|
|
SessionID: before,
|
|
ContinueURL: after,
|
|
}, nil
|
|
}
|