Subject: [PATCH v14 0/6] LSM: Multiple concurrent LSMs
Date: Thursday 25th July 2013 18:22:51 UTC (over 4 years ago)
Subject: [PATCH v14 0/6] LSM: Multiple concurrent LSMs Version 14 of this patchset is based on v3.10. It required significant change from version 13 due to changes in the audit code. It came out cleaner, especially in the changes to NetLabel. This version supports all existing LSMs running together at the same time. The combinations tested most completely are: apparmor,tomoyo,smack,yama - Ubuntu apparmor,selinux,smack,yama - Fedora I have been unable to figure out how to configure SELinux on Ubuntu and TOMOYO on Fedora. That's the only reason the list does not include all five LSMs at once. Combining LSMs that use networking is tricky, but can be done. There are changes coming from AppArmor that might make it even trickier, but that's a problem for the future. Change the infrastructure for Linux Security Modules (LSM)s from a single vector of hook handlers to a list based method for handling multiple concurrent modules. All combinations of existing LSMs are supported. The "security=" boot option takes a comma separated list of LSMs, registering them in the order presented. The LSM hooks will be executed in the order registered. Hooks that return errors are not short circuited. All hooks are called even if one of the LSM hooks fails. The result returned will be that of the last LSM hook that failed. All behavior from security/capability.c has been moved into the hook handling. The security/commoncap functions used to get called from the LSM specific code. The handling of the capability functions has been moved out of the LSMs and into the hook handling. A level of indirection has been introduced in the handling of security blobs. LSMs no longer access ->security fields directly, instead they use an abstraction provided by lsm_[gs]et field functions. The notion that "the security context" can be represented as a single u32 "secid" does not scale to the case where multiple LSMs want to provide "the security context". The XFRM and secmark facilities appear unlikely to ever allow for more than the existing 32 bit values. The NetLabel scheme might possibly be used to represent more than one labeling scheme (CIPSO does allow for multiple tags) although there is no plan to do so at this time. The SO_PEERSEC scheme is capable of providing information from multiple LSMs. Auditing can deal with multiple secids. The NetLabel, XFRM and secmark facilities are restricted to use by one LSM at a time. The SO_PEERSEC facility can provide information from multiple LSMs, but existing user space tools don't understand that. The default behavior is to assign each of these facilities to the first registered LSM that uses them. They can be configured for use by any of the LSMs that provide hooks for them. SO_PEERSEC can be configured to provide information from all of the LSMs that provide hooks. The /proc/*/attr interfaces are given to one LSM. This can be done by setting CONFIG_SECURITY_PRESENT. Additional interfaces have been created in /proc/*/attr so that each LSM has its own named interfaces. The name of the presenting LSM can be read from /sys/kernel/security/present. The list of LSMs being used can be read from /sys/kernel/security/lsm. A "security context" may now contrain information processed by more than one LSM. The proper form of a security context identifies the information it contains by LSM: smack='Pop'selinux='system_u:object_r:etc_r:s0' A security context without the LSM identifying lsm='