netfilter: Set /proc/net entries owner to root in namespace

Various files are owned by root with 0440 permission. Reading them is
impossible in an unprivileged user namespace, interfering with firewall
tools. For instance, iptables-save relies on /proc/net/ip_tables_names
contents to dump only loaded tables.

This patch assigned ownership of the following files to root in the
current namespace:

- /proc/net/*_tables_names
- /proc/net/*_tables_matches
- /proc/net/*_tables_targets
- /proc/net/nf_conntrack
- /proc/net/nf_conntrack_expect
- /proc/net/netfilter/nfnetlink_log

A mapping for root must be available, so this order should be followed:

unshare(CLONE_NEWUSER);
/* Setup the mapping */
unshare(CLONE_NEWNET);

Signed-off-by: Philip Whineray <phil@firehol.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/netfilter/nf_conntrack_expect.c b/net/netfilter/nf_conntrack_expect.c
index acf5c7b..278927a 100644 (file)
--- a/net/netfilter/nf_conntrack_expect.c
+++ b/net/netfilter/nf_conntrack_expect.c
@@ -596,11 +596,18 @@ static int exp_proc_init(struct net *net)
 {
 #ifdef CONFIG_NF_CONNTRACK_PROCFS
        struct proc_dir_entry *proc;
+       kuid_t root_uid;
+       kgid_t root_gid;
 
        proc = proc_create("nf_conntrack_expect", 0440, net->proc_net,
                           &exp_file_ops);
        if (!proc)
                return -ENOMEM;
+
+       root_uid = make_kuid(net->user_ns, 0);
+       root_gid = make_kgid(net->user_ns, 0);
+       if (uid_valid(root_uid) && gid_valid(root_gid))
+               proc_set_user(proc, root_uid, root_gid);
 #endif /* CONFIG_NF_CONNTRACK_PROCFS */
        return 0;
 }

diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c
index 1fb3cac..0f1a45b 100644 (file)
--- a/net/netfilter/nf_conntrack_standalone.c
+++ b/net/netfilter/nf_conntrack_standalone.c
@@ -392,11 +392,18 @@ static const struct file_operations ct_cpu_seq_fops = {
 static int nf_conntrack_standalone_init_proc(struct net *net)
 {
        struct proc_dir_entry *pde;
+       kuid_t root_uid;
+       kgid_t root_gid;
 
        pde = proc_create("nf_conntrack", 0440, net->proc_net, &ct_file_ops);
        if (!pde)
                goto out_nf_conntrack;
 
+       root_uid = make_kuid(net->user_ns, 0);
+       root_gid = make_kgid(net->user_ns, 0);
+       if (uid_valid(root_uid) && gid_valid(root_gid))
+               proc_set_user(pde, root_uid, root_gid);
+
        pde = proc_create("nf_conntrack", S_IRUGO, net->proc_net_stat,
                          &ct_cpu_seq_fops);
        if (!pde)

diff --git a/net/netfilter/nfnetlink_log.c b/net/netfilter/nfnetlink_log.c
index 740cce4..dea4676 100644 (file)
--- a/net/netfilter/nfnetlink_log.c
+++ b/net/netfilter/nfnetlink_log.c
@@ -1064,15 +1064,26 @@ static int __net_init nfnl_log_net_init(struct net *net)
 {
        unsigned int i;
        struct nfnl_log_net *log = nfnl_log_pernet(net);
+#ifdef CONFIG_PROC_FS
+       struct proc_dir_entry *proc;
+       kuid_t root_uid;
+       kgid_t root_gid;
+#endif
 
        for (i = 0; i < INSTANCE_BUCKETS; i++)
                INIT_HLIST_HEAD(&log->instance_table[i]);
        spin_lock_init(&log->instances_lock);
 
 #ifdef CONFIG_PROC_FS
-       if (!proc_create("nfnetlink_log", 0440,
-                        net->nf.proc_netfilter, &nful_file_ops))
+       proc = proc_create("nfnetlink_log", 0440,
+                          net->nf.proc_netfilter, &nful_file_ops);
+       if (!proc)
                return -ENOMEM;
+
+       root_uid = make_kuid(net->user_ns, 0);
+       root_gid = make_kgid(net->user_ns, 0);
+       if (uid_valid(root_uid) && gid_valid(root_gid))
+               proc_set_user(proc, root_uid, root_gid);
 #endif
        return 0;
 }

diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index d4aaad7..c8a0b7d 100644 (file)
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -26,6 +26,7 @@
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/audit.h>
+#include <linux/user_namespace.h>
 #include <net/net_namespace.h>
 
 #include <linux/netfilter/x_tables.h>
@@ -1226,6 +1227,8 @@ int xt_proto_init(struct net *net, u_int8_t af)
 #ifdef CONFIG_PROC_FS
        char buf[XT_FUNCTION_MAXNAMELEN];
        struct proc_dir_entry *proc;
+       kuid_t root_uid;
+       kgid_t root_gid;
 #endif
 
        if (af >= ARRAY_SIZE(xt_prefix))
@@ -1233,12 +1236,17 @@ int xt_proto_init(struct net *net, u_int8_t af)
 
 
 #ifdef CONFIG_PROC_FS
+       root_uid = make_kuid(net->user_ns, 0);
+       root_gid = make_kgid(net->user_ns, 0);
+
        strlcpy(buf, xt_prefix[af], sizeof(buf));
        strlcat(buf, FORMAT_TABLES, sizeof(buf));
        proc = proc_create_data(buf, 0440, net->proc_net, &xt_table_ops,
                                (void *)(unsigned long)af);
        if (!proc)
                goto out;
+       if (uid_valid(root_uid) && gid_valid(root_gid))
+               proc_set_user(proc, root_uid, root_gid);
 
        strlcpy(buf, xt_prefix[af], sizeof(buf));
        strlcat(buf, FORMAT_MATCHES, sizeof(buf));
@@ -1246,6 +1254,8 @@ int xt_proto_init(struct net *net, u_int8_t af)
                                (void *)(unsigned long)af);
        if (!proc)
                goto out_remove_tables;
+       if (uid_valid(root_uid) && gid_valid(root_gid))
+               proc_set_user(proc, root_uid, root_gid);
 
        strlcpy(buf, xt_prefix[af], sizeof(buf));
        strlcat(buf, FORMAT_TARGETS, sizeof(buf));
@@ -1253,6 +1263,8 @@ int xt_proto_init(struct net *net, u_int8_t af)
                                (void *)(unsigned long)af);
        if (!proc)
                goto out_remove_matches;
+       if (uid_valid(root_uid) && gid_valid(root_gid))
+               proc_set_user(proc, root_uid, root_gid);
 #endif
 
        return 0;