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package handlers
import (
"context"
"crypto/hmac"
"crypto/sha256"
"encoding/base64"
"errors"
"net/http"
)
func (h *Handlers) GetSession(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
cookieName := "session_token"
sessionCookie, err := r.Cookie(cookieName)
if err != nil {
msg := "auth failed; failed to get session token from cookies"
h.log.Debug(msg, "error", err)
next.ServeHTTP(w, r)
return
}
cookieValueB, err := base64.URLEncoding.
DecodeString(sessionCookie.Value)
if err != nil {
msg := "auth failed; failed to decode b64 cookie"
h.log.Debug(msg, "error", err)
next.ServeHTTP(w, r)
return
}
cookieValue := string(cookieValueB)
if len(cookieValue) < sha256.Size {
h.log.Warn("small cookie", "size", len(cookieValue))
next.ServeHTTP(w, r)
return
}
// Split apart the signature and original cookie value.
signature := cookieValue[:sha256.Size]
sessionToken := cookieValue[sha256.Size:]
//verify signature
mac := hmac.New(sha256.New, []byte(h.cfg.CookieSecret))
mac.Write([]byte(cookieName))
mac.Write([]byte(sessionToken))
expectedSignature := mac.Sum(nil)
if !hmac.Equal([]byte(signature), expectedSignature) {
h.log.Debug("cookie with an invalid sign")
next.ServeHTTP(w, r)
return
}
userSession, err := h.cacheGetSession(sessionToken)
if err != nil {
msg := "auth failed; session does not exists"
err = errors.New(msg)
h.log.Debug(msg, "error", err)
next.ServeHTTP(w, r)
return
}
if userSession.IsExpired() {
h.mc.RemoveKey(sessionToken)
msg := "session is expired"
h.log.Debug(msg, "error", err, "token", sessionToken)
next.ServeHTTP(w, r)
return
}
ctx := context.WithValue(r.Context(),
"username", userSession.Username)
if err := h.cacheSetSession(sessionToken,
userSession); err != nil {
msg := "failed to marshal user session"
h.log.Warn(msg, "error", err)
next.ServeHTTP(w, r)
return
}
next.ServeHTTP(w, r.WithContext(ctx))
})
}
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