xfrm: Add possibility to set the default to block if we have no policy

As the default we assume the traffic to pass, if we have no
matching IPsec policy. With this patch, we have a possibility to
change this default from allow to block. It can be configured
via netlink. Each direction (input/output/forward) can be
configured separately. With the default to block configuered,
we need allow policies for all packet flows we accept.
We do not use default policy lookup for the loopback device.

v1->v2
 - fix compiling when XFRM is disabled
 - Reported-by: kernel test robot <lkp@intel.com>

Co-developed-by: Christian Langrock <christian.langrock@secunet.com>
Signed-off-by: Christian Langrock <christian.langrock@secunet.com>
Co-developed-by: Antony Antony <antony.antony@secunet.com>
Signed-off-by: Antony Antony <antony.antony@secunet.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

diff --git a/include/net/netns/xfrm.h b/include/net/netns/xfrm.h
index e946366e8ba5f2aef8b39a56c79ce8a1000129b9..88c647302977a2ef4b3410c2abf110e543d4a0b7 100644 (file)
--- a/include/net/netns/xfrm.h
+++ b/include/net/netns/xfrm.h
@@ -65,6 +65,13 @@ struct netns_xfrm {
        u32                     sysctl_aevent_rseqth;
        int                     sysctl_larval_drop;
        u32                     sysctl_acq_expires;
+
+       u8                      policy_default;
+#define XFRM_POL_DEFAULT_IN    1
+#define XFRM_POL_DEFAULT_OUT   2
+#define XFRM_POL_DEFAULT_FWD   4
+#define XFRM_POL_DEFAULT_MASK  7
+
 #ifdef CONFIG_SYSCTL
        struct ctl_table_header *sysctl_hdr;
 #endif

diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index cbff7c2a97246a3ca80d300be5bcc06548f804cc..2308210793a016b82803ef0c6143a5725ea9f7ea 100644 (file)
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -1075,6 +1075,22 @@ xfrm_state_addr_cmp(const struct xfrm_tmpl *tmpl, const struct xfrm_state *x, un
 }
 
 #ifdef CONFIG_XFRM
+static inline bool
+xfrm_default_allow(struct net *net, int dir)
+{
+       u8 def = net->xfrm.policy_default;
+
+       switch (dir) {
+       case XFRM_POLICY_IN:
+               return def & XFRM_POL_DEFAULT_IN ? false : true;
+       case XFRM_POLICY_OUT:
+               return def & XFRM_POL_DEFAULT_OUT ? false : true;
+       case XFRM_POLICY_FWD:
+               return def & XFRM_POL_DEFAULT_FWD ? false : true;
+       }
+       return false;
+}
+
 int __xfrm_policy_check(struct sock *, int dir, struct sk_buff *skb,
                        unsigned short family);
 
@@ -1088,9 +1104,13 @@ static inline int __xfrm_policy_check2(struct sock *sk, int dir,
        if (sk && sk->sk_policy[XFRM_POLICY_IN])
                return __xfrm_policy_check(sk, ndir, skb, family);
 
-       return  (!net->xfrm.policy_count[dir] && !secpath_exists(skb)) ||
-               (skb_dst(skb) && (skb_dst(skb)->flags & DST_NOPOLICY)) ||
-               __xfrm_policy_check(sk, ndir, skb, family);
+       if (xfrm_default_allow(net, dir))
+               return (!net->xfrm.policy_count[dir] && !secpath_exists(skb)) ||
+                      (skb_dst(skb) && (skb_dst(skb)->flags & DST_NOPOLICY)) ||
+                      __xfrm_policy_check(sk, ndir, skb, family);
+       else
+               return (skb_dst(skb) && (skb_dst(skb)->flags & DST_NOPOLICY)) ||
+                      __xfrm_policy_check(sk, ndir, skb, family);
 }
 
 static inline int xfrm_policy_check(struct sock *sk, int dir, struct sk_buff *skb, unsigned short family)
@@ -1142,9 +1162,13 @@ static inline int xfrm_route_forward(struct sk_buff *skb, unsigned short family)
 {
        struct net *net = dev_net(skb->dev);
 
-       return  !net->xfrm.policy_count[XFRM_POLICY_OUT] ||
-               (skb_dst(skb)->flags & DST_NOXFRM) ||
-               __xfrm_route_forward(skb, family);
+       if (xfrm_default_allow(net, XFRM_POLICY_FWD))
+               return !net->xfrm.policy_count[XFRM_POLICY_OUT] ||
+                       (skb_dst(skb)->flags & DST_NOXFRM) ||
+                       __xfrm_route_forward(skb, family);
+       else
+               return (skb_dst(skb)->flags & DST_NOXFRM) ||
+                       __xfrm_route_forward(skb, family);
 }
 
 static inline int xfrm4_route_forward(struct sk_buff *skb)

diff --git a/include/uapi/linux/xfrm.h b/include/uapi/linux/xfrm.h
index ffc6a5391bb7bb8f7543cb36fb16487596fd3255..6e809510619251c114cd69cd853a8ce4dafc36c9 100644 (file)
--- a/include/uapi/linux/xfrm.h
+++ b/include/uapi/linux/xfrm.h
@@ -213,6 +213,11 @@ enum {
        XFRM_MSG_GETSPDINFO,
 #define XFRM_MSG_GETSPDINFO XFRM_MSG_GETSPDINFO
 
+       XFRM_MSG_SETDEFAULT,
+#define XFRM_MSG_SETDEFAULT XFRM_MSG_SETDEFAULT
+       XFRM_MSG_GETDEFAULT,
+#define XFRM_MSG_GETDEFAULT XFRM_MSG_GETDEFAULT
+
        XFRM_MSG_MAPPING,
 #define XFRM_MSG_MAPPING XFRM_MSG_MAPPING
        __XFRM_MSG_MAX
@@ -508,6 +513,11 @@ struct xfrm_user_offload {
 #define XFRM_OFFLOAD_IPV6      1
 #define XFRM_OFFLOAD_INBOUND   2
 
+struct xfrm_userpolicy_default {
+       __u8                            dirmask;
+       __u8                            action;
+};
+
 #ifndef __KERNEL__
 /* backwards compatibility for userspace */
 #define XFRMGRP_ACQUIRE                1

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 827d842550217fd521f154b1111d94d75ca9e59e..d5cb082e11fc31edd2734ee40413fed931dcd178 100644 (file)
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -3165,6 +3165,11 @@ ok:
        return dst;
 
 nopol:
+       if (!(dst_orig->dev->flags & IFF_LOOPBACK) &&
+           !xfrm_default_allow(net, dir)) {
+               err = -EPERM;
+               goto error;
+       }
        if (!(flags & XFRM_LOOKUP_ICMP)) {
                dst = dst_orig;
                goto ok;
@@ -3553,6 +3558,11 @@ int __xfrm_policy_check(struct sock *sk, int dir, struct sk_buff *skb,
        }
 
        if (!pol) {
+               if (!xfrm_default_allow(net, dir)) {
+                       XFRM_INC_STATS(net, LINUX_MIB_XFRMINNOPOLS);
+                       return 0;
+               }
+
                if (sp && secpath_has_nontransport(sp, 0, &xerr_idx)) {
                        xfrm_secpath_reject(xerr_idx, skb, &fl);
                        XFRM_INC_STATS(net, LINUX_MIB_XFRMINNOPOLS);
@@ -3607,6 +3617,12 @@ int __xfrm_policy_check(struct sock *sk, int dir, struct sk_buff *skb,
                                tpp[ti++] = &pols[pi]->xfrm_vec[i];
                }
                xfrm_nr = ti;
+
+               if (!xfrm_default_allow(net, dir) && !xfrm_nr) {
+                       XFRM_INC_STATS(net, LINUX_MIB_XFRMINNOSTATES);
+                       goto reject;
+               }
+
                if (npols > 1) {
                        xfrm_tmpl_sort(stp, tpp, xfrm_nr, family);
                        tpp = stp;

diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index b47d613409b70ad2c290c8542474ea2ea7e8b678..4eafd1130c3e2f6c3821a16f7c59d811d37d6633 100644 (file)
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -1961,6 +1961,54 @@ static struct sk_buff *xfrm_policy_netlink(struct sk_buff *in_skb,
        return skb;
 }
 
+static int xfrm_set_default(struct sk_buff *skb, struct nlmsghdr *nlh,
+                           struct nlattr **attrs)
+{
+       struct net *net = sock_net(skb->sk);
+       struct xfrm_userpolicy_default *up = nlmsg_data(nlh);
+       u8 dirmask = (1 << up->dirmask) & XFRM_POL_DEFAULT_MASK;
+       u8 old_default = net->xfrm.policy_default;
+
+       net->xfrm.policy_default = (old_default & (0xff ^ dirmask))
+                                   | (up->action << up->dirmask);
+
+       rt_genid_bump_all(net);
+
+       return 0;
+}
+
+static int xfrm_get_default(struct sk_buff *skb, struct nlmsghdr *nlh,
+                           struct nlattr **attrs)
+{
+       struct sk_buff *r_skb;
+       struct nlmsghdr *r_nlh;
+       struct net *net = sock_net(skb->sk);
+       struct xfrm_userpolicy_default *r_up, *up;
+       int len = NLMSG_ALIGN(sizeof(struct xfrm_userpolicy_default));
+       u32 portid = NETLINK_CB(skb).portid;
+       u32 seq = nlh->nlmsg_seq;
+
+       up = nlmsg_data(nlh);
+
+       r_skb = nlmsg_new(len, GFP_ATOMIC);
+       if (!r_skb)
+               return -ENOMEM;
+
+       r_nlh = nlmsg_put(r_skb, portid, seq, XFRM_MSG_GETDEFAULT, sizeof(*r_up), 0);
+       if (!r_nlh) {
+               kfree_skb(r_skb);
+               return -EMSGSIZE;
+       }
+
+       r_up = nlmsg_data(r_nlh);
+
+       r_up->action = ((net->xfrm.policy_default & (1 << up->dirmask)) >> up->dirmask);
+       r_up->dirmask = up->dirmask;
+       nlmsg_end(r_skb, r_nlh);
+
+       return nlmsg_unicast(net->xfrm.nlsk, r_skb, portid);
+}
+
 static int xfrm_get_policy(struct sk_buff *skb, struct nlmsghdr *nlh,
                struct nlattr **attrs)
 {
@@ -2664,6 +2712,8 @@ const int xfrm_msg_min[XFRM_NR_MSGTYPES] = {
        [XFRM_MSG_GETSADINFO  - XFRM_MSG_BASE] = sizeof(u32),
        [XFRM_MSG_NEWSPDINFO  - XFRM_MSG_BASE] = sizeof(u32),
        [XFRM_MSG_GETSPDINFO  - XFRM_MSG_BASE] = sizeof(u32),
+       [XFRM_MSG_SETDEFAULT  - XFRM_MSG_BASE] = XMSGSIZE(xfrm_userpolicy_default),
+       [XFRM_MSG_GETDEFAULT  - XFRM_MSG_BASE] = XMSGSIZE(xfrm_userpolicy_default),
 };
 EXPORT_SYMBOL_GPL(xfrm_msg_min);
 
@@ -2743,6 +2793,8 @@ static const struct xfrm_link {
                                                   .nla_pol = xfrma_spd_policy,
                                                   .nla_max = XFRMA_SPD_MAX },
        [XFRM_MSG_GETSPDINFO  - XFRM_MSG_BASE] = { .doit = xfrm_get_spdinfo   },
+       [XFRM_MSG_SETDEFAULT  - XFRM_MSG_BASE] = { .doit = xfrm_set_default   },
+       [XFRM_MSG_GETDEFAULT  - XFRM_MSG_BASE] = { .doit = xfrm_get_default   },
 };
 
 static int xfrm_user_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,