On Wed, Oct 11, 2023 at 04:53:57AM +0300, Konstantin Meskhidze (A) wrote: > > > 10/2/2023 11:26 PM, Mickaël Salaün пишет: > > Thanks for this new version Konstantin. I pushed this series, with minor > > changes, to -next. So far, no warning. But it needs some changes, mostly > > kernel-only, but also one with the handling of port 0 with bind (see my > > review below). > > > > On Wed, Sep 20, 2023 at 05:26:36PM +0800, Konstantin Meskhidze wrote: > > > This commit adds network rules support in the ruleset management > > > helpers and the landlock_create_ruleset syscall. > > > Refactor user space API to support network actions. Add new network > > > access flags, network rule and network attributes. Increment Landlock > > > ABI version. Expand access_masks_t to u32 to be sure network access > > > rights can be stored. Implement socket_bind() and socket_connect() > > > LSM hooks, which enables to restrict TCP socket binding and connection > > > to specific ports. > > > The new landlock_net_port_attr structure has two fields. The allowed_access > > > field contains the LANDLOCK_ACCESS_NET_* rights. The port field contains > > > the port value according to the allowed protocol. This field can > > > take up to a 64-bit value [1] but the maximum value depends on the related > > > protocol (e.g. 16-bit for TCP). > > > > > > [1] > > > https://lore.kernel.org/r/278ab07f-7583-a4e0-3d37-1bacd091531d@xxxxxxxxxxx > > > > > > Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxx> > > > Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@xxxxxxxxxx> > > > --- > > > > > > +int add_rule_net_service(struct landlock_ruleset *ruleset, > > > > We should only export functions with a "landlock_" prefix, and "service" > > is now replaced with "port", which gives landlock_add_rule_net_port(). > > > > For consistency, we should also rename add_rule_path_beneath() into > > landlock_add_rule_path_beneath(), move it into fs.c, and merge > > landlock_append_fs_rule() into it (being careful to not move the related > > code to ease review). This change should be part of the "landlock: > > Refactor landlock_add_rule() syscall" patch. Please be careful to keep > > the other changes happening in other patches. > > > > > > > + const void __user *const rule_attr) > > > +{ > > > + struct landlock_net_port_attr net_port_attr; > > > + int res; > > > + access_mask_t mask, bind_access_mask; > > > + > > > + /* Copies raw user space buffer. */ > > > + res = copy_from_user(&net_port_attr, rule_attr, sizeof(net_port_attr)); > > > > We should include <linux/uaccess.h> because of copy_from_user(). > > > > Same for landlock_add_rule_path_beneath(). > > > > > + if (res) > > > + return -EFAULT; > > > + > > > + /* > > > + * Informs about useless rule: empty allowed_access (i.e. deny rules) > > > + * are ignored by network actions. > > > + */ > > > + if (!net_port_attr.allowed_access) > > > + return -ENOMSG; > > > + > > > + /* > > > + * Checks that allowed_access matches the @ruleset constraints > > > + * (ruleset->access_masks[0] is automatically upgraded to 64-bits). > > > + */ > > > + mask = landlock_get_net_access_mask(ruleset, 0); > > > + if ((net_port_attr.allowed_access | mask) != mask) > > > + return -EINVAL; > > > + > > > + /* > > > + * Denies inserting a rule with port 0 (for bind action) or > > > + * higher than 65535. > > > + */ > > > + bind_access_mask = net_port_attr.allowed_access & > > > + LANDLOCK_ACCESS_NET_BIND_TCP; > > > + if (((net_port_attr.port == 0) && > > > + (bind_access_mask == LANDLOCK_ACCESS_NET_BIND_TCP)) || > > > > For context about "port 0 binding" see > > https://lore.kernel.org/all/7cb458f1-7aff-ccf3-abfd-b563bfc65b84@xxxxxxxxxx/ > > > > I previously said: > > > > > To say it another way, we should not allow to add a rule with port > > > > > 0 for > > > > > LANDLOCK_ACCESS_NET_BIND_TCP, but return -EINVAL in this case. This > > > > > limitation should be explained, documented and tested. > > > > Thinking more about this port 0 for bind (and after an interesting > > discussion with Eric), it would be a mistake to forbid a rule to bind on > > port 0 because this is very useful for some network services, and > > because it would not be reasonable to have an LSM hook to control such > > "random ports". Instead we should document what using this value means > > (i.e. pick a dynamic available port in a range defined by the sysadmin) > > and highlight the fact that it is controlled with the > > /proc/sys/net/ipv4/ip_local_port_range sysctl, which is also used by > > IPv6. > > Hi Mickaёl. > I also wonder which part of documentation (landlock.rst) we should include > zero port description in? This documentation should be in the struct landlock_net_port_attr's @port description, which will then be part of the generated documentation. > > > > We then need to test binding on port zero by getting the binded port > > (cf. getsockopt/getsockname) and checking that we can indeed connect to > > it. > > > > > + (net_port_attr.port > U16_MAX)) > > > + return -EINVAL; > > > + > > > + /* Imports the new rule. */ > > > + return landlock_append_net_rule(ruleset, net_port_attr.port, > > > + net_port_attr.allowed_access); > > > +}
