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libudev: monitor - ignore messages from unusual sources

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For added protection, ignore any unicast message received on the
netlink socket or any multicast message on the kernel group not
received from the kernel.

Signed-off-by: Scott James Remnant <scott@ubuntu.com>
This commit is contained in:
Scott James Remnant 2009-04-08 16:16:14 -07:00 committed by Kay Sievers
parent e2b362d9f2
commit e86a923d50
1 changed files with 23 additions and 6 deletions
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29
udev/lib/libudev-monitor.c
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@ -260,6 +260,7 @@ struct udev_device *udev_monitor_receive_device(struct udev_monitor *udev_monito
struct iovec iov;
char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
struct cmsghdr *cmsg;
struct sockaddr_nl snl;
struct ucred *cred;
char buf[4096];
size_t bufpos;
@ -280,34 +281,50 @@ struct udev_device *udev_monitor_receive_device(struct udev_monitor *udev_monito
smsg.msg_control = cred_msg;
smsg.msg_controllen = sizeof(cred_msg);
if (udev_monitor->snl.nl_family != 0) {
smsg.msg_name = &snl;
smsg.msg_namelen = sizeof snl;
}
if (recvmsg(udev_monitor->sock, &smsg, 0) < 0) {
if (errno != EINTR)
info(udev_monitor->udev, "unable to receive message");
info(udev_monitor->udev, "unable to receive message\n");
return NULL;
}
if (udev_monitor->snl.nl_family != 0) {
if (snl.nl_groups == 0) {
info(udev_monitor->udev, "unicast netlink message ignored\n");
return NULL;
}
if ((snl.nl_groups == UDEV_MONITOR_KERNEL) && (snl.nl_pid > 0)) {
info(udev_monitor->udev, "multicast kernel netlink message from pid %d ignored\n", snl.nl_pid);
return NULL;
}
}
cmsg = CMSG_FIRSTHDR(&smsg);
if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
info(udev_monitor->udev, "no sender credentials received, message ignored");
info(udev_monitor->udev, "no sender credentials received, message ignored\n");
return NULL;
}
cred = (struct ucred *)CMSG_DATA(cmsg);
if (cred->uid != 0) {
info(udev_monitor->udev, "sender uid=%d, message ignored", cred->uid);
info(udev_monitor->udev, "sender uid=%d, message ignored\n", cred->uid);
return NULL;
}
/* skip header */
bufpos = strlen(buf) + 1;
if (bufpos < sizeof("a@/d") || bufpos >= sizeof(buf)) {
info(udev_monitor->udev, "invalid message length");
info(udev_monitor->udev, "invalid message length\n");
return NULL;
}
/* check message header */
if (strstr(buf, "@/") == NULL) {
info(udev_monitor->udev, "unrecognized message header");
info(udev_monitor->udev, "unrecognized message header\n");
return NULL;
}
@ -414,6 +431,6 @@ int udev_monitor_send_device(struct udev_monitor *udev_monitor, struct udev_devi
else
return -1;
info(udev_monitor->udev, "passed %zi bytes to monitor %p, \n", count, udev_monitor);
info(udev_monitor->udev, "passed %zi bytes to monitor %p\n", count, udev_monitor);
return count;
}