| Message ID | 7d845623366ba0d435d5c82bf318455871929e90.1387815795.git.dborkman@redhat.com |
|---|---|
| State | Changes Requested |
| Headers | show |
On 2013/12/24 1:41, Daniel Borkmann wrote: > It would be useful e.g. in a server or desktop environment to have > a facility in the notion of fine-grained "per application" or "per > application group" firewall policies. Probably, users in the mobile, > embedded area (e.g. Android based) with different security policy > requirements for application groups could have great benefit from > that as well. For example, with a little bit of configuration effort, > an admin could whitelist well-known applications, and thus block > otherwise unwanted "hard-to-track" applications like [1] from a > user's machine. Blocking is just one example, but it is not limited > to that, meaning we can have much different scenarios/policies that > netfilter allows us than just blocking, e.g. fine grained settings > where applications are allowed to connect/send traffic to, application > traffic marking/conntracking, application-specific packet mangling, > and so on. > > Implementation of PID-based matching would not be appropriate > as they frequently change, and child tracking would make that > even more complex and ugly. Cgroups would be a perfect candidate > for accomplishing that as they associate a set of tasks with a > set of parameters for one or more subsystems, in our case the > netfilter subsystem, which, of course, can be combined with other > cgroup subsystems into something more complex if needed. > > As mentioned, to overcome this constraint, such processes could > be placed into one or multiple cgroups where different fine-grained > rules can be defined depending on the application scenario, while > e.g. everything else that is not part of that could be dropped (or > vice versa), thus making life harder for unwanted processes to > communicate to the outside world. So, we make use of cgroups here > to track jobs and limit their resources in terms of iptables > policies; in other words, limiting, tracking, etc what they are > allowed to communicate. > > In our case we're working on outgoing traffic based on which local > socket that originated from. Also, one doesn't even need to have > an a-prio knowledge of the application internals regarding their > particular use of ports or protocols. Matching is *extremly* > lightweight as we just test for the sk_classid marker of sockets, > originating from net_cls. net_cls and netfilter do not contradict > each other; in fact, each construct can live as standalone or they > can be used in combination with each other, which is perfectly fine, > plus it serves Tejun's requirement to not introduce a new cgroups > subsystem. Through this, we result in a very minimal and efficient > module, and don't add anything except netfilter code. > I'd suggest splitting cls_cgroup code into 2 parts. The first part is to manage cgroupfs and classid, and should be put into net/core/ and add a new config like NET_CGROUP_CLASSID for it. The second part is specific cls_cgroup code. -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 12/27/2013 04:13 AM, Li Zefan wrote: > On 2013/12/24 1:41, Daniel Borkmann wrote: >> It would be useful e.g. in a server or desktop environment to have >> a facility in the notion of fine-grained "per application" or "per >> application group" firewall policies. Probably, users in the mobile, >> embedded area (e.g. Android based) with different security policy >> requirements for application groups could have great benefit from >> that as well. For example, with a little bit of configuration effort, >> an admin could whitelist well-known applications, and thus block >> otherwise unwanted "hard-to-track" applications like [1] from a >> user's machine. Blocking is just one example, but it is not limited >> to that, meaning we can have much different scenarios/policies that >> netfilter allows us than just blocking, e.g. fine grained settings >> where applications are allowed to connect/send traffic to, application >> traffic marking/conntracking, application-specific packet mangling, >> and so on. >> >> Implementation of PID-based matching would not be appropriate >> as they frequently change, and child tracking would make that >> even more complex and ugly. Cgroups would be a perfect candidate >> for accomplishing that as they associate a set of tasks with a >> set of parameters for one or more subsystems, in our case the >> netfilter subsystem, which, of course, can be combined with other >> cgroup subsystems into something more complex if needed. >> >> As mentioned, to overcome this constraint, such processes could >> be placed into one or multiple cgroups where different fine-grained >> rules can be defined depending on the application scenario, while >> e.g. everything else that is not part of that could be dropped (or >> vice versa), thus making life harder for unwanted processes to >> communicate to the outside world. So, we make use of cgroups here >> to track jobs and limit their resources in terms of iptables >> policies; in other words, limiting, tracking, etc what they are >> allowed to communicate. >> >> In our case we're working on outgoing traffic based on which local >> socket that originated from. Also, one doesn't even need to have >> an a-prio knowledge of the application internals regarding their >> particular use of ports or protocols. Matching is *extremly* >> lightweight as we just test for the sk_classid marker of sockets, >> originating from net_cls. net_cls and netfilter do not contradict >> each other; in fact, each construct can live as standalone or they >> can be used in combination with each other, which is perfectly fine, >> plus it serves Tejun's requirement to not introduce a new cgroups >> subsystem. Through this, we result in a very minimal and efficient >> module, and don't add anything except netfilter code. >> > > I'd suggest splitting cls_cgroup code into 2 parts. The first part > is to manage cgroupfs and classid, and should be put into net/core/ > and add a new config like NET_CGROUP_CLASSID for it. The second part > is specific cls_cgroup code. Sure, if this is wished, I'd do this as a follow-up as it doesn't affect any of this code in netfilter here. Thanks, Daniel -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 2013/12/27 16:05, Daniel Borkmann wrote: > On 12/27/2013 04:13 AM, Li Zefan wrote: >> On 2013/12/24 1:41, Daniel Borkmann wrote: >>> It would be useful e.g. in a server or desktop environment to have >>> a facility in the notion of fine-grained "per application" or "per >>> application group" firewall policies. Probably, users in the mobile, >>> embedded area (e.g. Android based) with different security policy >>> requirements for application groups could have great benefit from >>> that as well. For example, with a little bit of configuration effort, >>> an admin could whitelist well-known applications, and thus block >>> otherwise unwanted "hard-to-track" applications like [1] from a >>> user's machine. Blocking is just one example, but it is not limited >>> to that, meaning we can have much different scenarios/policies that >>> netfilter allows us than just blocking, e.g. fine grained settings >>> where applications are allowed to connect/send traffic to, application >>> traffic marking/conntracking, application-specific packet mangling, >>> and so on. >>> >>> Implementation of PID-based matching would not be appropriate >>> as they frequently change, and child tracking would make that >>> even more complex and ugly. Cgroups would be a perfect candidate >>> for accomplishing that as they associate a set of tasks with a >>> set of parameters for one or more subsystems, in our case the >>> netfilter subsystem, which, of course, can be combined with other >>> cgroup subsystems into something more complex if needed. >>> >>> As mentioned, to overcome this constraint, such processes could >>> be placed into one or multiple cgroups where different fine-grained >>> rules can be defined depending on the application scenario, while >>> e.g. everything else that is not part of that could be dropped (or >>> vice versa), thus making life harder for unwanted processes to >>> communicate to the outside world. So, we make use of cgroups here >>> to track jobs and limit their resources in terms of iptables >>> policies; in other words, limiting, tracking, etc what they are >>> allowed to communicate. >>> >>> In our case we're working on outgoing traffic based on which local >>> socket that originated from. Also, one doesn't even need to have >>> an a-prio knowledge of the application internals regarding their >>> particular use of ports or protocols. Matching is *extremly* >>> lightweight as we just test for the sk_classid marker of sockets, >>> originating from net_cls. net_cls and netfilter do not contradict >>> each other; in fact, each construct can live as standalone or they >>> can be used in combination with each other, which is perfectly fine, >>> plus it serves Tejun's requirement to not introduce a new cgroups >>> subsystem. Through this, we result in a very minimal and efficient >>> module, and don't add anything except netfilter code. >>> >> >> I'd suggest splitting cls_cgroup code into 2 parts. The first part >> is to manage cgroupfs and classid, and should be put into net/core/ >> and add a new config like NET_CGROUP_CLASSID for it. The second part >> is specific cls_cgroup code. > > Sure, if this is wished, I'd do this as a follow-up as it doesn't affect > any of this code in netfilter here. > We should clean up the code before introducing a new feature, not the other way. And I wish by touching the code outside netfilter we'll get more eyes on whether it's ok to reuse cls cgroup for netfilter. -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 12/28/2013 02:33 AM, Li Zefan wrote: > On 2013/12/27 16:05, Daniel Borkmann wrote: >> On 12/27/2013 04:13 AM, Li Zefan wrote: ... >>> I'd suggest splitting cls_cgroup code into 2 parts. The first part >>> is to manage cgroupfs and classid, and should be put into net/core/ >>> and add a new config like NET_CGROUP_CLASSID for it. The second part >>> is specific cls_cgroup code. >> >> Sure, if this is wished, I'd do this as a follow-up as it doesn't affect >> any of this code in netfilter here. > > We should clean up the code before introducing a new feature, not the > other way. Hehe, quite honestly, I think this is YOUR opinion of a "cleanup", which makes the code actually more complicated, and it's not strictly needed. If you are so desperate about this separation, fine, I will do this, but again, I don't think it's *strictly* required for this. -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 12/28/2013 09:17 AM, Daniel Borkmann wrote: > On 12/28/2013 02:33 AM, Li Zefan wrote: >> On 2013/12/27 16:05, Daniel Borkmann wrote: >>> On 12/27/2013 04:13 AM, Li Zefan wrote: > ... >>>> I'd suggest splitting cls_cgroup code into 2 parts. The first part >>>> is to manage cgroupfs and classid, and should be put into net/core/ >>>> and add a new config like NET_CGROUP_CLASSID for it. The second part >>>> is specific cls_cgroup code. >>> >>> Sure, if this is wished, I'd do this as a follow-up as it doesn't affect >>> any of this code in netfilter here. >> >> We should clean up the code before introducing a new feature, not the >> other way. > > Hehe, quite honestly, I think this is YOUR opinion of a "cleanup", which > makes the code actually more complicated, and it's not strictly needed. > > If you are so desperate about this separation, fine, I will do this, but > again, I don't think it's *strictly* required for this. Thinking about this further a bit, with this separation into net/core/, you would need another Kconfig, where people choose between built-in or module (or none). With built-in you would disallow people to load/unload the cgroup part during runtime. With the module, you would introduce a module dependency _for each_, even if you only want to use net_cls, which sort of is not what we want from a simple "cleanup". -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 2013/12/28 16:44, Daniel Borkmann wrote: > On 12/28/2013 09:17 AM, Daniel Borkmann wrote: >> On 12/28/2013 02:33 AM, Li Zefan wrote: >>> On 2013/12/27 16:05, Daniel Borkmann wrote: >>>> On 12/27/2013 04:13 AM, Li Zefan wrote: >> ... >>>>> I'd suggest splitting cls_cgroup code into 2 parts. The first part >>>>> is to manage cgroupfs and classid, and should be put into net/core/ >>>>> and add a new config like NET_CGROUP_CLASSID for it. The second part >>>>> is specific cls_cgroup code. >>>> >>>> Sure, if this is wished, I'd do this as a follow-up as it doesn't affect >>>> any of this code in netfilter here. >>> >>> We should clean up the code before introducing a new feature, not the >>> other way. >> >> Hehe, quite honestly, I think this is YOUR opinion of a "cleanup", which >> makes the code actually more complicated, and it's not strictly needed. >> >> If you are so desperate about this separation, fine, I will do this, but >> again, I don't think it's *strictly* required for this. > Currently we have: cls_cgroup With your patch, it's changed to: __ cls_cgroup / net_cgroup_classid - \ __ netfilter_cgroup The code should be re-organized. > Thinking about this further a bit, with this separation into net/core/, you > would need another Kconfig, where people choose between built-in or > module (or none). Just disable module support for net_cgroup_classid. I never like the cgroup feature that allows modular subsystems. It will be just about 100 lines of code, so we gain little by making it modular. Futhermore with this change, we can simplify include/linux/cls_cgroup.h Moreoever cls_cgroup is the only modular cgroup subsystem, so I may even remove this feature from cgroup core after the change to cls_cgroup. > With built-in you would disallow people to load/unload the > cgroup part during runtime. With the module, you would introduce a module > dependency _for each_, even if you only want to use net_cls, which sort of > is not what we want from a simple "cleanup". > -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
>> Thinking about this further a bit, with this separation into net/core/, you >> would need another Kconfig, where people choose between built-in or >> module (or none). > > Just disable module support for net_cgroup_classid. I never like the cgroup > feature that allows modular subsystems. It will be just about 100 lines of > code, so we gain little by making it modular. Futhermore with this change, > we can simplify include/linux/cls_cgroup.h > > Moreoever cls_cgroup is the only modular cgroup subsystem, so I may even remove > this feature from cgroup core after the change to cls_cgroup. > >> With built-in you would disallow people to load/unload the >> cgroup part during runtime. With the module, you would introduce a module >> dependency _for each_, even if you only want to use net_cls, which sort of >> is not what we want from a simple "cleanup". >> Even if it's a module, I don't think there's any dependency here, as the only interface that cls_cgroup and netfilter_cgroup need is task_cls_classid(), which is an inline function and doesn't involve any EXPORT symbol. Therefore it works even if CONFIG_CLS_CGROUP doesn't depend of CONFIG_NET_CGROUP_CLASSID. -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 12/28/2013 10:20 AM, Li Zefan wrote: > On 2013/12/28 16:44, Daniel Borkmann wrote: >> On 12/28/2013 09:17 AM, Daniel Borkmann wrote: >>> On 12/28/2013 02:33 AM, Li Zefan wrote: >>>> On 2013/12/27 16:05, Daniel Borkmann wrote: >>>>> On 12/27/2013 04:13 AM, Li Zefan wrote: >>> ... >>>>>> I'd suggest splitting cls_cgroup code into 2 parts. The first part >>>>>> is to manage cgroupfs and classid, and should be put into net/core/ >>>>>> and add a new config like NET_CGROUP_CLASSID for it. The second part >>>>>> is specific cls_cgroup code. >>>>> >>>>> Sure, if this is wished, I'd do this as a follow-up as it doesn't affect >>>>> any of this code in netfilter here. >>>> >>>> We should clean up the code before introducing a new feature, not the >>>> other way. >>> >>> Hehe, quite honestly, I think this is YOUR opinion of a "cleanup", which >>> makes the code actually more complicated, and it's not strictly needed. >>> >>> If you are so desperate about this separation, fine, I will do this, but >>> again, I don't think it's *strictly* required for this. >> > > Currently we have: > > cls_cgroup > > With your patch, it's changed to: > > __ cls_cgroup > / > net_cgroup_classid - > \ __ netfilter_cgroup > > The code should be re-organized. > >> Thinking about this further a bit, with this separation into net/core/, you >> would need another Kconfig, where people choose between built-in or >> module (or none). > > Just disable module support for net_cgroup_classid. I never like the cgroup > feature that allows modular subsystems. It will be just about 100 lines of > code, so we gain little by making it modular. Futhermore with this change, > we can simplify include/linux/cls_cgroup.h > > Moreoever cls_cgroup is the only modular cgroup subsystem, so I may even remove > this feature from cgroup core after the change to cls_cgroup. Ok, will send a v4 with this change included, thanks. >> With built-in you would disallow people to load/unload the >> cgroup part during runtime. With the module, you would introduce a module >> dependency _for each_, even if you only want to use net_cls, which sort of >> is not what we want from a simple "cleanup". -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 12/28/2013 07:04 PM, Daniel Borkmann wrote: > On 12/28/2013 10:20 AM, Li Zefan wrote: >> On 2013/12/28 16:44, Daniel Borkmann wrote: >>> On 12/28/2013 09:17 AM, Daniel Borkmann wrote: >>>> On 12/28/2013 02:33 AM, Li Zefan wrote: >>>>> On 2013/12/27 16:05, Daniel Borkmann wrote: >>>>>> On 12/27/2013 04:13 AM, Li Zefan wrote: >>>> ... >>>>>>> I'd suggest splitting cls_cgroup code into 2 parts. The first part >>>>>>> is to manage cgroupfs and classid, and should be put into net/core/ >>>>>>> and add a new config like NET_CGROUP_CLASSID for it. The second part >>>>>>> is specific cls_cgroup code. >>>>>> >>>>>> Sure, if this is wished, I'd do this as a follow-up as it doesn't affect >>>>>> any of this code in netfilter here. >>>>> >>>>> We should clean up the code before introducing a new feature, not the >>>>> other way. >>>> >>>> Hehe, quite honestly, I think this is YOUR opinion of a "cleanup", which >>>> makes the code actually more complicated, and it's not strictly needed. >>>> >>>> If you are so desperate about this separation, fine, I will do this, but >>>> again, I don't think it's *strictly* required for this. >>> >> >> Currently we have: >> >> cls_cgroup >> >> With your patch, it's changed to: >> >> __ cls_cgroup >> / >> net_cgroup_classid - >> \ __ netfilter_cgroup >> >> The code should be re-organized. >> >>> Thinking about this further a bit, with this separation into net/core/, you >>> would need another Kconfig, where people choose between built-in or >>> module (or none). >> >> Just disable module support for net_cgroup_classid. I never like the cgroup >> feature that allows modular subsystems. It will be just about 100 lines of >> code, so we gain little by making it modular. Futhermore with this change, >> we can simplify include/linux/cls_cgroup.h >> >> Moreoever cls_cgroup is the only modular cgroup subsystem, so I may even remove >> this feature from cgroup core after the change to cls_cgroup. Btw, if you plan to remove modular support at some point in time, there's still netprio_cgroup on todo. > Ok, will send a v4 with this change included, thanks. > >>> With built-in you would disallow people to load/unload the >>> cgroup part during runtime. With the module, you would introduce a module >>> dependency _for each_, even if you only want to use net_cls, which sort of >>> is not what we want from a simple "cleanup". > -- > To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/Documentation/cgroups/net_cls.txt b/Documentation/cgroups/net_cls.txt index 9face6b..ec18234 100644 --- a/Documentation/cgroups/net_cls.txt +++ b/Documentation/cgroups/net_cls.txt @@ -6,6 +6,8 @@ tag network packets with a class identifier (classid). The Traffic Controller (tc) can be used to assign different priorities to packets from different cgroups. +Also, Netfilter (iptables) can use this tag to perform +actions on such packets. Creating a net_cls cgroups instance creates a net_cls.classid file. This net_cls.classid value is initialized to 0. @@ -32,3 +34,6 @@ tc class add dev eth0 parent 10: classid 10:1 htb rate 40mbit - creating traffic class 10:1 tc filter add dev eth0 parent 10: protocol ip prio 10 handle 1: cgroup + +configuring iptables, basic example: +iptables -A OUTPUT -m cgroup ! --cgroup 0x100001 -j DROP diff --git a/include/uapi/linux/netfilter/Kbuild b/include/uapi/linux/netfilter/Kbuild index 17c3af2..2e6b9e4 100644 --- a/include/uapi/linux/netfilter/Kbuild +++ b/include/uapi/linux/netfilter/Kbuild @@ -39,6 +39,7 @@ header-y += xt_TEE.h header-y += xt_TPROXY.h header-y += xt_addrtype.h header-y += xt_bpf.h +header-y += xt_cgroup.h header-y += xt_cluster.h header-y += xt_comment.h header-y += xt_connbytes.h diff --git a/include/uapi/linux/netfilter/xt_cgroup.h b/include/uapi/linux/netfilter/xt_cgroup.h new file mode 100644 index 0000000..43acb7e --- /dev/null +++ b/include/uapi/linux/netfilter/xt_cgroup.h @@ -0,0 +1,11 @@ +#ifndef _UAPI_XT_CGROUP_H +#define _UAPI_XT_CGROUP_H + +#include <linux/types.h> + +struct xt_cgroup_info { + __u32 id; + __u32 invert; +}; + +#endif /* _UAPI_XT_CGROUP_H */ diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig index c3398cd..bbdab88 100644 --- a/net/netfilter/Kconfig +++ b/net/netfilter/Kconfig @@ -858,6 +858,16 @@ config NETFILTER_XT_MATCH_BPF To compile it as a module, choose M here. If unsure, say N. +config NETFILTER_XT_MATCH_CGROUP + tristate '"control group" match support' + depends on NETFILTER_ADVANCED + depends on CGROUPS + select NET_CLS_CGROUP + ---help--- + Socket/process control group matching allows you to match locally + generated packets based on which net_cls control group processes + belong to. + config NETFILTER_XT_MATCH_CLUSTER tristate '"cluster" match support' depends on NF_CONNTRACK diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile index 394483b..9345365 100644 --- a/net/netfilter/Makefile +++ b/net/netfilter/Makefile @@ -142,6 +142,7 @@ obj-$(CONFIG_NETFILTER_XT_MATCH_MULTIPORT) += xt_multiport.o obj-$(CONFIG_NETFILTER_XT_MATCH_NFACCT) += xt_nfacct.o obj-$(CONFIG_NETFILTER_XT_MATCH_OSF) += xt_osf.o obj-$(CONFIG_NETFILTER_XT_MATCH_OWNER) += xt_owner.o +obj-$(CONFIG_NETFILTER_XT_MATCH_CGROUP) += xt_cgroup.o obj-$(CONFIG_NETFILTER_XT_MATCH_PHYSDEV) += xt_physdev.o obj-$(CONFIG_NETFILTER_XT_MATCH_PKTTYPE) += xt_pkttype.o obj-$(CONFIG_NETFILTER_XT_MATCH_POLICY) += xt_policy.o diff --git a/net/netfilter/xt_cgroup.c b/net/netfilter/xt_cgroup.c new file mode 100644 index 0000000..66107a7 --- /dev/null +++ b/net/netfilter/xt_cgroup.c @@ -0,0 +1,71 @@ +/* + * Xtables module to match the process control group. + * + * Might be used to implement individual "per-application" firewall + * policies in contrast to global policies based on control groups. + * Matching is based upon processes tagged to net_cls' classid marker. + * + * (C) 2013 Daniel Borkmann <dborkman@redhat.com> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + */ + +#include <linux/skbuff.h> +#include <linux/module.h> +#include <linux/netfilter/x_tables.h> +#include <linux/netfilter/xt_cgroup.h> +#include <net/sock.h> + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Daniel Borkmann <dborkman@redhat.com>"); +MODULE_DESCRIPTION("Xtables: process control group matching"); +MODULE_ALIAS("ipt_cgroup"); +MODULE_ALIAS("ip6t_cgroup"); + +static int cgroup_mt_check(const struct xt_mtchk_param *par) +{ + struct xt_cgroup_info *info = par->matchinfo; + + if (info->invert & ~1) + return -EINVAL; + + return info->id ? 0 : -EINVAL; +} + +static bool +cgroup_mt(const struct sk_buff *skb, struct xt_action_param *par) +{ + const struct xt_cgroup_info *info = par->matchinfo; + + if (skb->sk == NULL) + return false; + + return (info->id == skb->sk->sk_classid) ^ info->invert; +} + +static struct xt_match cgroup_mt_reg __read_mostly = { + .name = "cgroup", + .revision = 0, + .family = NFPROTO_UNSPEC, + .checkentry = cgroup_mt_check, + .match = cgroup_mt, + .matchsize = sizeof(struct xt_cgroup_info), + .me = THIS_MODULE, + .hooks = (1 << NF_INET_LOCAL_OUT) | + (1 << NF_INET_POST_ROUTING), +}; + +static int __init cgroup_mt_init(void) +{ + return xt_register_match(&cgroup_mt_reg); +} + +static void __exit cgroup_mt_exit(void) +{ + xt_unregister_match(&cgroup_mt_reg); +} + +module_init(cgroup_mt_init); +module_exit(cgroup_mt_exit);
It would be useful e.g. in a server or desktop environment to have a facility in the notion of fine-grained "per application" or "per application group" firewall policies. Probably, users in the mobile, embedded area (e.g. Android based) with different security policy requirements for application groups could have great benefit from that as well. For example, with a little bit of configuration effort, an admin could whitelist well-known applications, and thus block otherwise unwanted "hard-to-track" applications like [1] from a user's machine. Blocking is just one example, but it is not limited to that, meaning we can have much different scenarios/policies that netfilter allows us than just blocking, e.g. fine grained settings where applications are allowed to connect/send traffic to, application traffic marking/conntracking, application-specific packet mangling, and so on. Implementation of PID-based matching would not be appropriate as they frequently change, and child tracking would make that even more complex and ugly. Cgroups would be a perfect candidate for accomplishing that as they associate a set of tasks with a set of parameters for one or more subsystems, in our case the netfilter subsystem, which, of course, can be combined with other cgroup subsystems into something more complex if needed. As mentioned, to overcome this constraint, such processes could be placed into one or multiple cgroups where different fine-grained rules can be defined depending on the application scenario, while e.g. everything else that is not part of that could be dropped (or vice versa), thus making life harder for unwanted processes to communicate to the outside world. So, we make use of cgroups here to track jobs and limit their resources in terms of iptables policies; in other words, limiting, tracking, etc what they are allowed to communicate. In our case we're working on outgoing traffic based on which local socket that originated from. Also, one doesn't even need to have an a-prio knowledge of the application internals regarding their particular use of ports or protocols. Matching is *extremly* lightweight as we just test for the sk_classid marker of sockets, originating from net_cls. net_cls and netfilter do not contradict each other; in fact, each construct can live as standalone or they can be used in combination with each other, which is perfectly fine, plus it serves Tejun's requirement to not introduce a new cgroups subsystem. Through this, we result in a very minimal and efficient module, and don't add anything except netfilter code. One possible, minimal usage example (many other iptables options can be applied obviously): 1) Configuring cgroups if not already done, e.g.: mkdir /sys/fs/cgroup/net_cls mount -t cgroup -o net_cls net_cls /sys/fs/cgroup/net_cls mkdir /sys/fs/cgroup/net_cls/0 echo 1 > /sys/fs/cgroup/net_cls/0/net_cls.classid (resp. a real flow handle id for tc) 2) Configuring netfilter (iptables-nftables), e.g.: iptables -A OUTPUT -m cgroup ! --cgroup 1 -j DROP 3) Running applications, e.g.: ping 208.67.222.222 <pid:1799> echo 1799 > /sys/fs/cgroup/net_cls/0/tasks 64 bytes from 208.67.222.222: icmp_seq=44 ttl=49 time=11.9 ms [...] ping 208.67.220.220 <pid:1804> ping: sendmsg: Operation not permitted [...] echo 1804 > /sys/fs/cgroup/net_cls/0/tasks 64 bytes from 208.67.220.220: icmp_seq=89 ttl=56 time=19.0 ms [...] Of course, real-world deployments would make use of cgroups user space toolsuite, or own custom policy daemons dynamically moving applications from/to various cgroups. [1] http://www.blackhat.com/presentations/bh-europe-06/bh-eu-06-biondi/bh-eu-06-biondi-up.pdf Signed-off-by: Daniel Borkmann <dborkman@redhat.com> Cc: Tejun Heo <tj@kernel.org> Cc: cgroups@vger.kernel.org --- Previous discussions, design considerations etc can be found in: - v1: http://patchwork.ozlabs.org/patch/280687/ - v1/alt: http://patchwork.ozlabs.org/patch/282477/ - v2: http://patchwork.ozlabs.org/patch/284582/ v1->v2: - Updated commit message, rebased - Applied Gao Feng's feedback v2->v3: - After discussions w/ Tejun, let's not add any cgroups code here, thus we _only_ add code in netfilter area, nowhere else, that's even more simple and cleaner than proposed. Documentation/cgroups/net_cls.txt | 5 +++ include/uapi/linux/netfilter/Kbuild | 1 + include/uapi/linux/netfilter/xt_cgroup.h | 11 +++++ net/netfilter/Kconfig | 10 +++++ net/netfilter/Makefile | 1 + net/netfilter/xt_cgroup.c | 71 ++++++++++++++++++++++++++++++++ 6 files changed, 99 insertions(+) create mode 100644 include/uapi/linux/netfilter/xt_cgroup.h create mode 100644 net/netfilter/xt_cgroup.c