2d7a85f4b0
It was possible to get a setuid root or setcap executable to write to
it's stdout or stderr (which has been set made a netlink socket) and
inadvertently reconfigure the networking stack.
To prevent this we check that both the creator of the socket and
the currentl applications has permission to reconfigure the network
stack.
Unfortunately this breaks Zebra which always uses sendto/sendmsg
and creates it's socket without any privileges.
To keep Zebra working don't bother checking if the creator of the
socket has privilege when a destination address is specified. Instead
rely exclusively on the privileges of the sender of the socket.
Note from Andy: This is exactly Eric's code except for some comment
clarifications and formatting fixes. Neither I nor, I think, anyone
else is thrilled with this approach, but I'm hesitant to wait on a
better fix since 3.15 is almost here.
Note to stable maintainers: This is a mess. An earlier series of
patches in 3.15 fix a rather serious security issue (CVE-2014-0181),
but they did so in a way that breaks Zebra. The offending series
includes:
commit aa4cf9452f
Author: Eric W. Biederman <ebiederm@xmission.com>
Date: Wed Apr 23 14:28:03 2014 -0700
net: Add variants of capable for use on netlink messages
If a given kernel version is missing that series of fixes, it's
probably worth backporting it and this patch. if that series is
present, then this fix is critical if you care about Zebra.
Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
180 lines
5.5 KiB
C
180 lines
5.5 KiB
C
#ifndef __LINUX_NETLINK_H
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#define __LINUX_NETLINK_H
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#include <linux/capability.h>
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#include <linux/skbuff.h>
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#include <linux/export.h>
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#include <net/scm.h>
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#include <uapi/linux/netlink.h>
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struct net;
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static inline struct nlmsghdr *nlmsg_hdr(const struct sk_buff *skb)
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{
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return (struct nlmsghdr *)skb->data;
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}
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enum netlink_skb_flags {
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NETLINK_SKB_MMAPED = 0x1, /* Packet data is mmaped */
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NETLINK_SKB_TX = 0x2, /* Packet was sent by userspace */
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NETLINK_SKB_DELIVERED = 0x4, /* Packet was delivered */
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NETLINK_SKB_DST = 0x8, /* Dst set in sendto or sendmsg */
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};
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struct netlink_skb_parms {
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struct scm_creds creds; /* Skb credentials */
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__u32 portid;
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__u32 dst_group;
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__u32 flags;
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struct sock *sk;
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};
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#define NETLINK_CB(skb) (*(struct netlink_skb_parms*)&((skb)->cb))
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#define NETLINK_CREDS(skb) (&NETLINK_CB((skb)).creds)
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extern void netlink_table_grab(void);
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extern void netlink_table_ungrab(void);
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#define NL_CFG_F_NONROOT_RECV (1 << 0)
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#define NL_CFG_F_NONROOT_SEND (1 << 1)
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/* optional Netlink kernel configuration parameters */
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struct netlink_kernel_cfg {
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unsigned int groups;
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unsigned int flags;
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void (*input)(struct sk_buff *skb);
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struct mutex *cb_mutex;
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void (*bind)(int group);
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bool (*compare)(struct net *net, struct sock *sk);
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};
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extern struct sock *__netlink_kernel_create(struct net *net, int unit,
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struct module *module,
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struct netlink_kernel_cfg *cfg);
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static inline struct sock *
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netlink_kernel_create(struct net *net, int unit, struct netlink_kernel_cfg *cfg)
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{
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return __netlink_kernel_create(net, unit, THIS_MODULE, cfg);
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}
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extern void netlink_kernel_release(struct sock *sk);
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extern int __netlink_change_ngroups(struct sock *sk, unsigned int groups);
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extern int netlink_change_ngroups(struct sock *sk, unsigned int groups);
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extern void __netlink_clear_multicast_users(struct sock *sk, unsigned int group);
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extern void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err);
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extern int netlink_has_listeners(struct sock *sk, unsigned int group);
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extern struct sk_buff *netlink_alloc_skb(struct sock *ssk, unsigned int size,
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u32 dst_portid, gfp_t gfp_mask);
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extern int netlink_unicast(struct sock *ssk, struct sk_buff *skb, __u32 portid, int nonblock);
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extern int netlink_broadcast(struct sock *ssk, struct sk_buff *skb, __u32 portid,
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__u32 group, gfp_t allocation);
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extern int netlink_broadcast_filtered(struct sock *ssk, struct sk_buff *skb,
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__u32 portid, __u32 group, gfp_t allocation,
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int (*filter)(struct sock *dsk, struct sk_buff *skb, void *data),
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void *filter_data);
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extern int netlink_set_err(struct sock *ssk, __u32 portid, __u32 group, int code);
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extern int netlink_register_notifier(struct notifier_block *nb);
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extern int netlink_unregister_notifier(struct notifier_block *nb);
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/* finegrained unicast helpers: */
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struct sock *netlink_getsockbyfilp(struct file *filp);
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int netlink_attachskb(struct sock *sk, struct sk_buff *skb,
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long *timeo, struct sock *ssk);
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void netlink_detachskb(struct sock *sk, struct sk_buff *skb);
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int netlink_sendskb(struct sock *sk, struct sk_buff *skb);
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static inline struct sk_buff *
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netlink_skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
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{
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struct sk_buff *nskb;
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nskb = skb_clone(skb, gfp_mask);
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if (!nskb)
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return NULL;
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/* This is a large skb, set destructor callback to release head */
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if (is_vmalloc_addr(skb->head))
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nskb->destructor = skb->destructor;
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return nskb;
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}
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/*
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* skb should fit one page. This choice is good for headerless malloc.
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* But we should limit to 8K so that userspace does not have to
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* use enormous buffer sizes on recvmsg() calls just to avoid
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* MSG_TRUNC when PAGE_SIZE is very large.
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*/
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#if PAGE_SIZE < 8192UL
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#define NLMSG_GOODSIZE SKB_WITH_OVERHEAD(PAGE_SIZE)
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#else
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#define NLMSG_GOODSIZE SKB_WITH_OVERHEAD(8192UL)
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#endif
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#define NLMSG_DEFAULT_SIZE (NLMSG_GOODSIZE - NLMSG_HDRLEN)
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struct netlink_callback {
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struct sk_buff *skb;
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const struct nlmsghdr *nlh;
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int (*dump)(struct sk_buff * skb,
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struct netlink_callback *cb);
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int (*done)(struct netlink_callback *cb);
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void *data;
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/* the module that dump function belong to */
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struct module *module;
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u16 family;
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u16 min_dump_alloc;
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unsigned int prev_seq, seq;
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long args[6];
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};
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struct netlink_notify {
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struct net *net;
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int portid;
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int protocol;
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};
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struct nlmsghdr *
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__nlmsg_put(struct sk_buff *skb, u32 portid, u32 seq, int type, int len, int flags);
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struct netlink_dump_control {
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int (*dump)(struct sk_buff *skb, struct netlink_callback *);
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int (*done)(struct netlink_callback *);
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void *data;
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struct module *module;
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u16 min_dump_alloc;
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};
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extern int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
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const struct nlmsghdr *nlh,
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struct netlink_dump_control *control);
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static inline int netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
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const struct nlmsghdr *nlh,
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struct netlink_dump_control *control)
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{
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if (!control->module)
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control->module = THIS_MODULE;
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return __netlink_dump_start(ssk, skb, nlh, control);
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}
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struct netlink_tap {
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struct net_device *dev;
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struct module *module;
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struct list_head list;
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};
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extern int netlink_add_tap(struct netlink_tap *nt);
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extern int netlink_remove_tap(struct netlink_tap *nt);
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bool __netlink_ns_capable(const struct netlink_skb_parms *nsp,
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struct user_namespace *ns, int cap);
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bool netlink_ns_capable(const struct sk_buff *skb,
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struct user_namespace *ns, int cap);
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bool netlink_capable(const struct sk_buff *skb, int cap);
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bool netlink_net_capable(const struct sk_buff *skb, int cap);
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#endif /* __LINUX_NETLINK_H */
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