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

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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>
This commit is contained in:
Philip Whineray 2015-11-22 11:35:07 +00:00 committed by Pablo Neira Ayuso
parent daaa7d647f
commit f13f2aeed1
4 changed files with 39 additions and 2 deletions
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7
net/netfilter/nf_conntrack_expect.c
View File

@ -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;
}

7
net/netfilter/nf_conntrack_standalone.c
View File

@ -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)

15
net/netfilter/nfnetlink_log.c
View File

@ -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;
}

12
net/netfilter/x_tables.c
View File

@ -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;