X-Git-Url: http://git.meshlink.io/?a=blobdiff_plain;f=avahi-core%2Fnetlink.c;h=acea6968a88592e1b7f34ad069252ba341998280;hb=9c0f9c65093cfa53d45f9b68782321eb8063a032;hp=c5afde90df5b1b15978993f0e3ca68bf17543293;hpb=fcc9b0efe1accdb0edcb3143a8e15782e69383db;p=catta

diff --git a/avahi-core/netlink.c b/avahi-core/netlink.c
index c5afde9..acea696 100644
--- a/avahi-core/netlink.c
+++ b/avahi-core/netlink.c
@@ -1,18 +1,16 @@
-/* $Id$ */
-
 /***
   This file is part of avahi.
- 
+
   avahi is free software; you can redistribute it and/or modify it
   under the terms of the GNU Lesser General Public License as
   published by the Free Software Foundation; either version 2.1 of the
   License, or (at your option) any later version.
- 
+
   avahi is distributed in the hope that it will be useful, but WITHOUT
   ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
   or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General
   Public License for more details.
- 
+
   You should have received a copy of the GNU Lesser General Public
   License along with avahi; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
@@ -46,44 +44,64 @@ struct AvahiNetlink {
 };
 
 int avahi_netlink_work(AvahiNetlink *nl, int block) {
+    ssize_t bytes;
+    struct msghdr smsg;
+    struct cmsghdr *cmsg;
+    struct ucred *cred;
+    struct iovec iov;
+    struct nlmsghdr *p;
+    char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
+
     assert(nl);
 
-    for (;;) {
-        ssize_t bytes;
-        struct nlmsghdr *p;
+    iov.iov_base = nl->buffer;
+    iov.iov_len = nl->buffer_length;
 
-        for (;;) {
-            if ((bytes = recv(nl->fd, nl->buffer, nl->buffer_length, block ? 0 : MSG_DONTWAIT)) < 0) {
+    smsg.msg_name = NULL;
+    smsg.msg_namelen = 0;
+    smsg.msg_iov = &iov;
+    smsg.msg_iovlen = 1;
+    smsg.msg_control = cred_msg;
+    smsg.msg_controllen = sizeof(cred_msg);
+    smsg.msg_flags = (block ? 0 : MSG_DONTWAIT);
 
-                if (errno == EAGAIN || errno == EINTR)
-                    return 1;
-                
-                avahi_log_error(__FILE__": recv() failed: %s", strerror(errno));
-                return 0;
-            }
+    if ((bytes = recvmsg(nl->fd, &smsg, 0)) < 0) {
+        if (errno == EAGAIN || errno == EINTR)
+            return 0;
 
-            break;
-        }
+        avahi_log_error(__FILE__": recvmsg() failed: %s", strerror(errno));
+        return -1;
+    }
+
+    cmsg = CMSG_FIRSTHDR(&smsg);
+
+    if (!cmsg || cmsg->cmsg_type != SCM_CREDENTIALS) {
+        avahi_log_warn("No sender credentials received, ignoring data.");
+        return -1;
+    }
+
+    cred = (struct ucred*) CMSG_DATA(cmsg);
 
-        p = (struct nlmsghdr *) nl->buffer;
-        
-        if (nl->callback) {
-            for (; bytes > 0; p = NLMSG_NEXT(p, bytes)) {
-                if (!NLMSG_OK(p, (size_t) bytes)) {
-                    avahi_log_warn(__FILE__": packet truncated");
-                    return 0;
-                }
-
-                nl->callback(nl, p, nl->userdata);
-            }
+    if (cred->uid != 0)
+        return -1;
+
+    p = (struct nlmsghdr *) nl->buffer;
+
+    assert(nl->callback);
+
+    for (; bytes > 0; p = NLMSG_NEXT(p, bytes)) {
+        if (!NLMSG_OK(p, (size_t) bytes)) {
+            avahi_log_warn(__FILE__": packet truncated");
+            return -1;
         }
 
-        if (block)
-            return 1;
+        nl->callback(nl, p, nl->userdata);
     }
+
+    return 0;
 }
 
-static void socket_event(AvahiWatch *w, int fd, AvahiWatchEvent event, void *userdata) {
+static void socket_event(AvahiWatch *w, int fd, AVAHI_GCC_UNUSED AvahiWatchEvent event, void *userdata) {
     AvahiNetlink *nl = userdata;
 
     assert(w);
@@ -95,6 +113,7 @@ static void socket_event(AvahiWatch *w, int fd, AvahiWatchEvent event, void *use
 
 AvahiNetlink *avahi_netlink_new(const AvahiPoll *poll_api, uint32_t groups, void (*cb) (AvahiNetlink *nl, struct nlmsghdr *n, void* userdata), void* userdata) {
     int fd = -1;
+    const int on = 1;
     struct sockaddr_nl addr;
     AvahiNetlink *nl = NULL;
 
@@ -105,17 +124,22 @@ AvahiNetlink *avahi_netlink_new(const AvahiPoll *poll_api, uint32_t groups, void
         avahi_log_error(__FILE__": socket(PF_NETLINK): %s", strerror(errno));
         return NULL;
     }
-    
+
     memset(&addr, 0, sizeof(addr));
     addr.nl_family = AF_NETLINK;
     addr.nl_groups = groups;
-    addr.nl_pid = getpid();
+    addr.nl_pid = 0; // use 0 instead of getpid() to allow multiple instances of avahi in one process
 
     if (bind(fd, (struct sockaddr *) &addr, sizeof(addr)) < 0) {
         avahi_log_error(__FILE__": bind(): %s", strerror(errno));
         goto fail;
     }
 
+    if (setsockopt(fd, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on)) < 0) {
+        avahi_log_error(__FILE__": SO_PASSCRED: %s", strerror(errno));
+        goto fail;
+    }
+
     if (!(nl = avahi_new(AvahiNetlink, 1))) {
         avahi_log_error(__FILE__": avahi_new() failed.");
         goto fail;
@@ -136,7 +160,7 @@ AvahiNetlink *avahi_netlink_new(const AvahiPoll *poll_api, uint32_t groups, void
         avahi_log_error(__FILE__": Failed to create watch.");
         goto fail;
     }
-    
+
     return nl;
 
 fail:
@@ -145,9 +169,7 @@ fail:
         close(fd);
 
     if (nl) {
-        if (nl->buffer)
-            avahi_free(nl);
-        
+        avahi_free(nl->buffer);
         avahi_free(nl);
     }
 
@@ -162,7 +184,7 @@ void avahi_netlink_free(AvahiNetlink *nl) {
 
     if (nl->fd >= 0)
         close(nl->fd);
-    
+
     avahi_free(nl->buffer);
     avahi_free(nl);
 }
@@ -170,12 +192,12 @@ void avahi_netlink_free(AvahiNetlink *nl) {
 int avahi_netlink_send(AvahiNetlink *nl, struct nlmsghdr *m, unsigned *ret_seq) {
     assert(nl);
     assert(m);
-    
+
     m->nlmsg_seq = nl->seq++;
     m->nlmsg_flags |= NLM_F_ACK;
 
     if (send(nl->fd, m, m->nlmsg_len, 0) < 0) {
-        avahi_log_error(__FILE__": send(): %s\n", strerror(errno));
+        avahi_log_error(__FILE__": send(): %s", strerror(errno));
         return -1;
     }