Subject: Re: [PATCH v2 7/8] net: Use netlink_ns_capable to verify the permisions of netlink messages

From: wangyufen <[email-masked]>
Date: Fri, 15 Aug 2014 15:38:17 +0800

On 2014/8/1 6:06, Jonathan Toppins wrote:
> On 7/25/14, 4:22 AM, Wangyufen wrote:
>> From: "Eric W. Biederman" <[email-masked]>
>>
>> It is possible by passing a netlink socket to a more privileged
>> executable and then to fool that executable into writing to the socket
>> data that happens to be valid netlink message to do something that
>> privileged executable did not intend to do.
>>
>> To keep this from happening replace bare capable and ns_capable calls
>> with netlink_capable, netlink_net_calls and netlink_ns_capable calls.
>> Which act the same as the previous calls except they verify that the
>> opener of the socket had the desired permissions as well.
>>
>> Reported-by: Andy Lutomirski <[email-masked]>
>> Signed-off-by: "Eric W. Biederman" <[email-masked]>
>> Signed-off-by: David S. Miller <[email-masked]>
>> Signed-off-by: Wang Yufen <[email-masked]>
>> ---
>>  crypto/crypto_user.c            | 2 +-
>>  drivers/connector/cn_proc.c     | 2 +-
>>  drivers/scsi/scsi_netlink.c     | 2 +-
>>  kernel/audit.c                  | 4 ++--
>>  net/core/rtnetlink.c            | 2 +-
>>  net/decnet/dn_dev.c             | 2 +-
>>  net/decnet/netfilter/dn_rtmsg.c | 2 +-
>>  net/netfilter/nfnetlink.c       | 2 +-
>>  net/netlink/genetlink.c         | 2 +-
>>  net/phonet/pn_netlink.c         | 4 ++--
>>  net/tipc/netlink.c              | 2 +-
>>  net/xfrm/xfrm_user.c            | 2 +-
>>  12 files changed, 14 insertions(+), 14 deletions(-)
>>
>> diff --git a/crypto/crypto_user.c b/crypto/crypto_user.c
>> index 910497b..c86969e 100644
>> --- a/crypto/crypto_user.c
>> +++ b/crypto/crypto_user.c
>> @@ -452,7 +452,7 @@ static int crypto_user_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
>>  	type -= CRYPTO_MSG_BASE;
>>  	link = &crypto_dispatch[type];
>>  
>> -	if (!capable(CAP_NET_ADMIN))
>> +	if (!netlink_capable(skb, CAP_NET_ADMIN))
>>  		return -EPERM;
>>  
>>  	if ((type == (CRYPTO_MSG_GETALG - CRYPTO_MSG_BASE) &&
>> diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c
>> index 094a710..46856ae 100644
>> --- a/drivers/connector/cn_proc.c
>> +++ b/drivers/connector/cn_proc.c
>> @@ -332,7 +332,7 @@ static void cn_proc_mcast_ctl(struct cn_msg *msg,
>>  		return;
>>  
>>  	/* Can only change if privileged. */
>> -	if (!capable(CAP_NET_ADMIN)) {
>> +	if (!__netlink_ns_capable(nsp, &init_user_ns, CAP_NET_ADMIN)) {
>>  		err = EPERM;
>>  		goto out;
>>  	}
>> diff --git a/drivers/scsi/scsi_netlink.c b/drivers/scsi/scsi_netlink.c
>> index c77628a..a930b66 100644
>> --- a/drivers/scsi/scsi_netlink.c
>> +++ b/drivers/scsi/scsi_netlink.c
>> @@ -112,7 +112,7 @@ scsi_nl_rcv_msg(struct sk_buff *skb)
>>  			goto next_msg;
>>  		}
>>  
>> -		if (!capable(CAP_SYS_ADMIN)) {
>> +		if (!netlink_capable(skb, CAP_SYS_ADMIN)) {
>>  			err = -EPERM;
>>  			goto next_msg;
>>  		}
>> diff --git a/kernel/audit.c b/kernel/audit.c
>> index b4efae8..3c3a31c 100644
>> --- a/kernel/audit.c
>> +++ b/kernel/audit.c
>> @@ -601,13 +601,13 @@ static int audit_netlink_ok(struct sk_buff *skb, u16 msg_type)
>>  	case AUDIT_TTY_SET:
>>  	case AUDIT_TRIM:
>>  	case AUDIT_MAKE_EQUIV:
>> -		if (!capable(CAP_AUDIT_CONTROL))
>> +		if (!netlink_capable(skb, CAP_AUDIT_CONTROL))
>>  			err = -EPERM;
>>  		break;
>>  	case AUDIT_USER:
>>  	case AUDIT_FIRST_USER_MSG ... AUDIT_LAST_USER_MSG:
>>  	case AUDIT_FIRST_USER_MSG2 ... AUDIT_LAST_USER_MSG2:
>> -		if (!capable(CAP_AUDIT_WRITE))
>> +		if (!netlink_capable(skb, CAP_AUDIT_WRITE))
>>  			err = -EPERM;
>>  		break;
>>  	default:  /* bad msg */
>> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
>> index a133427..d3ac150 100644
>> --- a/net/core/rtnetlink.c
>> +++ b/net/core/rtnetlink.c
>> @@ -2010,7 +2010,7 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
>>  	sz_idx = type>>2;
>>  	kind = type&3;
>>  
>> -	if (kind != 2 && !capable(CAP_NET_ADMIN))
>> +	if (kind != 2 && !netlink_net_capable(skb, CAP_NET_ADMIN))
>>  		return -EPERM;
>>  
>>  	if (kind == 2 && nlh->nlmsg_flags&NLM_F_DUMP) {
>> diff --git a/net/decnet/dn_dev.c b/net/decnet/dn_dev.c
>> index c00e307..b79ce1e 100644
>> --- a/net/decnet/dn_dev.c
>> +++ b/net/decnet/dn_dev.c
>> @@ -440,7 +440,7 @@ int dn_dev_ioctl(unsigned int cmd, void __user *arg)
>>  	case SIOCGIFADDR:
>>  		break;
>>  	case SIOCSIFADDR:
>> -		if (!capable(CAP_NET_ADMIN))
>> +		if (!netlink_capable(skb, CAP_NET_ADMIN))
> 
> Hello,
> 
> I am working on the 3.2 backport based off of these patches and am
> getting a compile error here. It appears even the 3.4 series doesn't
> compile, snippet of compile log for 3.4 series below:
> 
> net/decnet/dn_dev.c: In function ‘dn_dev_ioctl’:
> net/decnet/dn_dev.c:443:24: error: ‘skb’ undeclared (first use in this
> function)
> net/decnet/dn_dev.c:443:24: note: each undeclared identifier is reported
> only once for each function it appears in
> make[2]: *** [net/decnet/dn_dev.o] Error 1
> make[1]: *** [net/decnet] Error 2
> 
> jtoppins@debian-devel:~/linux/linux-stable$ git log --oneline -10
> a926d22 netlink: Only check file credentials for implicit destinations
> 070d4a0 net: Use netlink_ns_capable to verify the permisions of netlink
> messages
> 31393c4 net: Add variants of capable for use on netlink messages
> 45a1d1f net: Add variants of capable for use on on sockets
> 9f2effc netlink: Rename netlink_capable netlink_allowed
> f4d5163 Add file_ns_capable() helper function for open-time capability
> checking
> 3e8d4ac userns: make each net (net_ns) belong to a user_ns
> 9087c45 netlink: Make the sending netlink socket availabe in NETLINK_CB
> 82f9c4a Linux 3.4.100
> 21870a3 iommu/vt-d: Disable translation if already enabled
> 
> Am I missing something?
> 
> Thanks,
> -Jon
> 
> 

sorry for that, I made a big mistake.  
I used the wrong .config file and net/decnet/dn_dev.c did't compiled in. 
I checked the patch, there is no need to change net/decnet/dn_dev.c, it's ioctl not netlink.

>>  			return -EACCES;
>>  		if (sdn->sdn_family != AF_DECnet)
>>  			return -EINVAL;
>> diff --git a/net/decnet/netfilter/dn_rtmsg.c b/net/decnet/netfilter/dn_rtmsg.c
>> index 1531135..dc750e2 100644
>> --- a/net/decnet/netfilter/dn_rtmsg.c
>> +++ b/net/decnet/netfilter/dn_rtmsg.c
>> @@ -108,7 +108,7 @@ static inline void dnrmg_receive_user_skb(struct sk_buff *skb)
>>  	if (nlh->nlmsg_len < sizeof(*nlh) || skb->len < nlh->nlmsg_len)
>>  		return;
>>  
>> -	if (!capable(CAP_NET_ADMIN))
>> +	if (!netlink_capable(skb, CAP_NET_ADMIN))
>>  		RCV_SKB_FAIL(-EPERM);
>>  
>>  	/* Eventually we might send routing messages too */
>> diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c
>> index e6ddde1..5cfc865 100644
>> --- a/net/netfilter/nfnetlink.c
>> +++ b/net/netfilter/nfnetlink.c
>> @@ -129,7 +129,7 @@ static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
>>  	const struct nfnetlink_subsystem *ss;
>>  	int type, err;
>>  
>> -	if (!capable(CAP_NET_ADMIN))
>> +	if (!netlink_net_capable(skb, CAP_NET_ADMIN))
>>  		return -EPERM;
>>  
>>  	/* All the messages must at least contain nfgenmsg */
>> diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
>> index 73d3f0c..dff8562 100644
>> --- a/net/netlink/genetlink.c
>> +++ b/net/netlink/genetlink.c
>> @@ -556,7 +556,7 @@ static int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
>>  		return -EOPNOTSUPP;
>>  
>>  	if ((ops->flags & GENL_ADMIN_PERM) &&
>> -	    !capable(CAP_NET_ADMIN))
>> +	    !netlink_capable(skb, CAP_NET_ADMIN))
>>  		return -EPERM;
>>  
>>  	if (nlh->nlmsg_flags & NLM_F_DUMP) {
>> diff --git a/net/phonet/pn_netlink.c b/net/phonet/pn_netlink.c
>> index d61f676..18485cd 100644
>> --- a/net/phonet/pn_netlink.c
>> +++ b/net/phonet/pn_netlink.c
>> @@ -70,7 +70,7 @@ static int addr_doit(struct sk_buff *skb, struct nlmsghdr *nlh, void *attr)
>>  	int err;
>>  	u8 pnaddr;
>>  
>> -	if (!capable(CAP_SYS_ADMIN))
>> +	if (!netlink_capable(skb, CAP_SYS_ADMIN))
>>  		return -EPERM;
>>  
>>  	ASSERT_RTNL();
>> @@ -228,7 +228,7 @@ static int route_doit(struct sk_buff *skb, struct nlmsghdr *nlh, void *attr)
>>  	int err;
>>  	u8 dst;
>>  
>> -	if (!capable(CAP_SYS_ADMIN))
>> +	if (!netlink_capable(skb, CAP_SYS_ADMIN))
>>  		return -EPERM;
>>  
>>  	ASSERT_RTNL();
>> diff --git a/net/tipc/netlink.c b/net/tipc/netlink.c
>> index 7bda8e3..0b4cf4f 100644
>> --- a/net/tipc/netlink.c
>> +++ b/net/tipc/netlink.c
>> @@ -47,7 +47,7 @@ static int handle_cmd(struct sk_buff *skb, struct genl_info *info)
>>  	int hdr_space = NLMSG_SPACE(GENL_HDRLEN + TIPC_GENL_HDRLEN);
>>  	u16 cmd;
>>  
>> -	if ((req_userhdr->cmd & 0xC000) && (!capable(CAP_NET_ADMIN)))
>> +	if ((req_userhdr->cmd & 0xC000) && (!netlink_capable(skb, CAP_NET_ADMIN)))
>>  		cmd = TIPC_CMD_NOT_NET_ADMIN;
>>  	else
>>  		cmd = req_userhdr->cmd;
>> diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
>> index c8b903d..ce16eba 100644
>> --- a/net/xfrm/xfrm_user.c
>> +++ b/net/xfrm/xfrm_user.c
>> @@ -2317,7 +2317,7 @@ static int xfrm_user_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
>>  	link = &xfrm_dispatch[type];
>>  
>>  	/* All operations require privileges, even GET */
>> -	if (!capable(CAP_NET_ADMIN))
>> +	if (!netlink_net_capable(skb, CAP_NET_ADMIN))
>>  		return -EPERM;
>>  
>>  	if ((type == (XFRM_MSG_GETSA - XFRM_MSG_BASE) ||
>>
> 
>