This patch allows for a user to disable the requirement to meet the
CAP_NET_BIND_SERVICE capability for a non-superuser. It is toggled by
the net.ipv4.allow_lowport_bind_nonsuperuser sysctl value.
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index e4b1a4d..c3f7c3c 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -411,6 +411,7 @@ enum
NET_IPV4_TCP_WORKAROUND_SIGNED_WINDOWS=115,
NET_TCP_DMA_COPYBREAK=116,
NET_TCP_SLOW_START_AFTER_IDLE=117,
+ NET_IPV4_ALLOW_LOWPORT_BIND_NONSUPERUSER=118,
};
enum {
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index c84a320..a2ea829 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -394,6 +394,11 @@ int inet_release(struct socket *sock)
/* It is off by default, see below. */
int sysctl_ip_nonlocal_bind;
+/* When this is enabled, it allows normal users to bind to ports <=
1023.
+ * This is set by the net.ipv4.allow_lowport_bind_nonsuperuser
sysctl value.
+ */
+int sysctl_ip_allow_lowport_bind_nonsuperuser;
+
int inet_bind(struct socket *sock, struct sockaddr *uaddr, int
addr_len)
{
struct sockaddr_in *addr = (struct sockaddr_in *)uaddr;
@@ -432,7 +437,8 @@ int inet_bind(struct socket *sock, struc
snum = ntohs(addr->sin_port);
err = -EACCES;
- if (snum && snum < PROT_SOCK && !capable(CAP_NET_BIND_SERVICE))
+ if (!sysctl_ip_allow_lowport_bind_nonsuperuser && snum && snum <
PROT_SOCK &&
+ !capable(CAP_NET_BIND_SERVICE))
goto out;
/* We keep a pair of addresses. rcv_saddr is the one
@@ -1412,3 +1418,4 @@ EXPORT_SYMBOL(inet_stream_ops);
EXPORT_SYMBOL(inet_unregister_protosw);
EXPORT_SYMBOL(net_statistics);
EXPORT_SYMBOL(sysctl_ip_nonlocal_bind);
+EXPORT_SYMBOL(sysctl_ip_allow_lowport_bind_nonsuperuser);
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 70cea9d..c57ef3a 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -20,6 +20,7 @@ #include <net/tcp.h>
/* From af_inet.c */
extern int sysctl_ip_nonlocal_bind;
+extern int sysctl_ip_allow_lowport_bind_nonsuperuser;
#ifdef CONFIG_SYSCTL
static int zero;
@@ -197,6 +198,14 @@ ctl_table ipv4_table[] = {
.proc_handler = &proc_dointvec
},
{
+ .ctl_name = NET_IPV4_ALLOW_LOWPORT_BIND_NONSUPERUSER,
+ .procname = "allow_lowport_bind_nonsuperuser",
+ .data = &sysctl_ip_allow_lowport_bind_nonsuperuser,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec
+ },
+ {
.ctl_name = NET_IPV4_TCP_SYN_RETRIES,
.procname = "tcp_syn_retries",
.data = &sysctl_tcp_syn_retries,
Signed-off-by: William Pitcock <[email protected]>
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