apparmor: Allow filtering based on secmark policy

Add support for dropping or accepting packets based on their secmark
tags.
Signed-off-by: Matthew Garrett <mjg59@google.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>

security/apparmor/lsm.c

@@ -23,6 +23,8 @@
 #include <linux/sysctl.h>
 #include <linux/audit.h>
 #include <linux/user_namespace.h>
+#include <linux/netfilter_ipv4.h>
+#include <linux/netfilter_ipv6.h>
 #include <net/sock.h>
 
 #include "include/apparmor.h"
@@ -1030,7 +1032,13 @@ static int apparmor_socket_shutdown(struct socket *sock, int how)
  */
 static int apparmor_socket_sock_rcv_skb(struct sock *sk, struct sk_buff *skb)
 {
-	return 0;
+	struct aa_sk_ctx *ctx = SK_CTX(sk);
+
+	if (!skb->secmark)
+		return 0;
+
+	return apparmor_secmark_check(ctx->label, OP_RECVMSG, AA_MAY_RECEIVE,
+				      skb->secmark, sk);
 }
 
 
@@ -1126,6 +1134,18 @@ static void apparmor_sock_graft(struct sock *sk, struct socket *parent)
 		ctx->label = aa_get_current_label();
 }
 
+static int apparmor_inet_conn_request(struct sock *sk, struct sk_buff *skb,
+				      struct request_sock *req)
+{
+	struct aa_sk_ctx *ctx = SK_CTX(sk);
+
+	if (!skb->secmark)
+		return 0;
+
+	return apparmor_secmark_check(ctx->label, OP_CONNECT, AA_MAY_CONNECT,
+				      skb->secmark, sk);
+}
+
 static struct security_hook_list apparmor_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(ptrace_access_check, apparmor_ptrace_access_check),
 	LSM_HOOK_INIT(ptrace_traceme, apparmor_ptrace_traceme),
@@ -1183,6 +1203,7 @@ static struct security_hook_list apparmor_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(socket_getpeersec_dgram,
 		      apparmor_socket_getpeersec_dgram),
 	LSM_HOOK_INIT(sock_graft, apparmor_sock_graft),
+	LSM_HOOK_INIT(inet_conn_request, apparmor_inet_conn_request),
 
 	LSM_HOOK_INIT(cred_alloc_blank, apparmor_cred_alloc_blank),
 	LSM_HOOK_INIT(cred_free, apparmor_cred_free),
@@ -1538,6 +1559,95 @@ static inline int apparmor_init_sysctl(void)
 }
 #endif /* CONFIG_SYSCTL */
 
+static unsigned int apparmor_ip_postroute(void *priv,
+					  struct sk_buff *skb,
+					  const struct nf_hook_state *state)
+{
+	struct aa_sk_ctx *ctx;
+	struct sock *sk;
+
+	if (!skb->secmark)
+		return NF_ACCEPT;
+
+	sk = skb_to_full_sk(skb);
+	if (sk == NULL)
+		return NF_ACCEPT;
+
+	ctx = SK_CTX(sk);
+	if (!apparmor_secmark_check(ctx->label, OP_SENDMSG, AA_MAY_SEND,
+				    skb->secmark, sk))
+		return NF_ACCEPT;
+
+	return NF_DROP_ERR(-ECONNREFUSED);
+
+}
+
+static unsigned int apparmor_ipv4_postroute(void *priv,
+					    struct sk_buff *skb,
+					    const struct nf_hook_state *state)
+{
+	return apparmor_ip_postroute(priv, skb, state);
+}
+
+static unsigned int apparmor_ipv6_postroute(void *priv,
+					    struct sk_buff *skb,
+					    const struct nf_hook_state *state)
+{
+	return apparmor_ip_postroute(priv, skb, state);
+}
+
+static const struct nf_hook_ops apparmor_nf_ops[] = {
+	{
+		.hook =         apparmor_ipv4_postroute,
+		.pf =           NFPROTO_IPV4,
+		.hooknum =      NF_INET_POST_ROUTING,
+		.priority =     NF_IP_PRI_SELINUX_FIRST,
+	},
+#if IS_ENABLED(CONFIG_IPV6)
+	{
+		.hook =         apparmor_ipv6_postroute,
+		.pf =           NFPROTO_IPV6,
+		.hooknum =      NF_INET_POST_ROUTING,
+		.priority =     NF_IP6_PRI_SELINUX_FIRST,
+	},
+#endif
+};
+
+static int __net_init apparmor_nf_register(struct net *net)
+{
+	int ret;
+
+	ret = nf_register_net_hooks(net, apparmor_nf_ops,
+				    ARRAY_SIZE(apparmor_nf_ops));
+	return ret;
+}
+
+static void __net_exit apparmor_nf_unregister(struct net *net)
+{
+	nf_unregister_net_hooks(net, apparmor_nf_ops,
+				ARRAY_SIZE(apparmor_nf_ops));
+}
+
+static struct pernet_operations apparmor_net_ops = {
+	.init = apparmor_nf_register,
+	.exit = apparmor_nf_unregister,
+};
+
+static int __init apparmor_nf_ip_init(void)
+{
+	int err;
+
+	if (!apparmor_enabled)
+		return 0;
+
+	err = register_pernet_subsys(&apparmor_net_ops);
+	if (err)
+		panic("Apparmor: register_pernet_subsys: error %d\n", err);
+
+	return 0;
+}
+__initcall(apparmor_nf_ip_init);
+
 static int __init apparmor_init(void)
 {
 	int error;

security/apparmor/net.c

@@ -18,6 +18,7 @@
 #include "include/label.h"
 #include "include/net.h"
 #include "include/policy.h"
+#include "include/secid.h"
 
 #include "net_names.h"
 
@@ -188,3 +189,68 @@ int aa_sock_file_perm(struct aa_label *label, const char *op, u32 request,
 
 	return aa_label_sk_perm(label, op, request, sock->sk);
 }
+
+static int apparmor_secmark_init(struct aa_secmark *secmark)
+{
+	struct aa_label *label;
+
+	if (secmark->label[0] == '*') {
+		secmark->secid = AA_SECID_WILDCARD;
+		return 0;
+	}
+
+	label = aa_label_strn_parse(&root_ns->unconfined->label,
+				    secmark->label, strlen(secmark->label),
+				    GFP_ATOMIC, false, false);
+
+	if (IS_ERR(label))
+		return PTR_ERR(label);
+
+	secmark->secid = label->secid;
+
+	return 0;
+}
+
+static int aa_secmark_perm(struct aa_profile *profile, u32 request, u32 secid,
+			   struct common_audit_data *sa, struct sock *sk)
+{
+	int i, ret;
+	struct aa_perms perms = { };
+
+	if (profile->secmark_count == 0)
+		return 0;
+
+	for (i = 0; i < profile->secmark_count; i++) {
+		if (!profile->secmark[i].secid) {
+			ret = apparmor_secmark_init(&profile->secmark[i]);
+			if (ret)
+				return ret;
+		}
+
+		if (profile->secmark[i].secid == secid ||
+		    profile->secmark[i].secid == AA_SECID_WILDCARD) {
+			if (profile->secmark[i].deny)
+				perms.deny = ALL_PERMS_MASK;
+			else
+				perms.allow = ALL_PERMS_MASK;
+
+			if (profile->secmark[i].audit)
+				perms.audit = ALL_PERMS_MASK;
+		}
+	}
+
+	aa_apply_modes_to_perms(profile, &perms);
+
+	return aa_check_perms(profile, &perms, request, sa, audit_net_cb);
+}
+
+int apparmor_secmark_check(struct aa_label *label, char *op, u32 request,
+			   u32 secid, struct sock *sk)
+{
+	struct aa_profile *profile;
+	DEFINE_AUDIT_SK(sa, op, sk);
+
+	return fn_for_each_confined(label, profile,
+				    aa_secmark_perm(profile, request, secid,
+						    &sa, sk));
+}