linux-kernel - CAP_NET_BIND_SERVICE checking in inet_bind vs socket

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Date:	Sat, 17 Feb 2007 01:33:28 +0000
From:	Simon Arlott <simon@...ott.org>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: CAP_NET_BIND_SERVICE checking in inet_bind vs socket_bind

Why does inet_bind (instead of socket_bind) check that ports below 1024 require CAP_NET_BIND_SERVICE?
Couldn't this check be moved to the dummy socket_bind so that the behaviour can be changed by a security module?

---

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index cf358c8..d75a2c5 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -431,9 +431,11 @@ int inet_bind(struct socket *sock, struc
 		goto out;
 
 	snum = ntohs(addr->sin_port);
+#ifndef CONFIG_SECURITY_NETWORK
 	err = -EACCES;
 	if (snum && snum < PROT_SOCK && !capable(CAP_NET_BIND_SERVICE))
 		goto out;
+#endif
 
 	/*      We keep a pair of addresses. rcv_saddr is the one
 	 *      used by hash lookups, and saddr is used for transmit.
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index 3585d8f..768989d 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -262,8 +262,10 @@ int inet6_bind(struct socket *sock, stru
 		return -EINVAL;
 
 	snum = ntohs(addr->sin6_port);
+#ifndef CONFIG_SECURITY_NETWORK
 	if (snum && snum < PROT_SOCK && !capable(CAP_NET_BIND_SERVICE))
 		return -EACCES;
+#endif
 
 	lock_sock(sk);
 
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
diff --git a/security/dummy.c b/security/dummy.c
index 558795b..1315b19 100644
--- a/security/dummy.c
+++ b/security/dummy.c
@@ -29,6 +29,8 @@ #include <linux/hugetlb.h>
 #include <linux/ptrace.h>
 #include <linux/file.h>
 
+#include <linux/in.h>
+
 static int dummy_ptrace (struct task_struct *parent, struct task_struct *child)
 {
 	return 0;
@@ -718,6 +720,26 @@ static int dummy_socket_post_create (str
 static int dummy_socket_bind (struct socket *sock, struct sockaddr *address,
 			      int addrlen)
 {
+	switch (address->sa_family) {
+#ifdef INET
+	case PF_INET: {
+			struct sockaddr_in *addr = (struct sockaddr_in *)address;
+			unsigned short snum;
+			snum = ntohs((addr->sin_port));
+			if (snum && snum < PROT_SOCK && !capable(CAP_NET_BIND_SERVICE))
+				return -EACCES;
+			break;
+		}
+	case PF_INET6: {
+			struct sockaddr_in6 *addr = (struct sockaddr_in6 *)address;
+			unsigned short snum;
+			snum = ntohs(addr->sin6_port);
+			if (snum && snum < PROT_SOCK && !capable(CAP_NET_BIND_SERVICE))
+				return -EACCES;
+			break;
+		}
+#endif
+	}
 	return 0;
 }
 

-- 
Simon Arlott


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