+ // Recover the filename from the cookie and the key
+ digest_t *digest = digest_open_by_name("sha256", 18);
+ if(!digest)
+ abort();
+ char *fingerprint = ecdsa_get_base64_public_key(invitation_key);
+ char hashbuf[18 + strlen(fingerprint)];
+ char cookie[25];
+ memcpy(hashbuf, data, 18);
+ memcpy(hashbuf + 18, fingerprint, sizeof hashbuf - 18);
+ digest_create(digest, hashbuf, sizeof hashbuf, cookie);
+ b64encode_urlsafe(cookie, cookie, 18);
+ digest_close(digest);
+ free(fingerprint);
+
+ char filename[PATH_MAX], usedname[PATH_MAX];
+ snprintf(filename, sizeof filename, "%s" SLASH "invitations" SLASH "%s", confbase, cookie);
+ snprintf(usedname, sizeof usedname, "%s" SLASH "invitations" SLASH "%s.used", confbase, cookie);
+
+ // Atomically rename the invitation file
+ if(rename(filename, usedname)) {
+ if(errno == ENOENT)
+ logger(DEBUG_ALWAYS, LOG_ERR, "Peer %s tried to use non-existing invitation %s\n", c->hostname, cookie);
+ else
+ logger(DEBUG_ALWAYS, LOG_ERR, "Error trying to rename invitation %s\n", cookie);