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path: root/security/safesetid/securityfs.c
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2019-10-30security/safesetid: Replace rcu_swap_protected() with rcu_replace_pointer()Paul E. McKenney
This commit replaces the use of rcu_swap_protected() with the more intuitively appealing rcu_replace_pointer() as a step towards removing rcu_swap_protected(). Link: https://lore.kernel.org/lkml/CAHk-=wiAsJLw1egFEE=Z7-GGtM6wcvtyytXZA1+BHqta4gg6Hw@mail.gmail.com/ Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Reported-by: Reported-by: kbuild test robot <lkp@intel.com> [ paulmck: From rcu_replace() to rcu_replace_pointer() per Ingo Molnar. ] Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Cc: Micah Morton <mortonm@chromium.org> Cc: James Morris <jmorris@namei.org> Cc: "Serge E. Hallyn" <serge@hallyn.com> Cc: <linux-security-module@vger.kernel.org>
2019-09-17LSM: SafeSetID: Stop releasing uninitialized rulesetMicah Morton
The first time a rule set is configured for SafeSetID, we shouldn't be trying to release the previously configured ruleset, since there isn't one. Currently, the pointer that would point to a previously configured ruleset is uninitialized on first rule set configuration, leading to a crash when we try to call release_ruleset with that pointer. Acked-by: Jann Horn <jannh@google.com> Signed-off-by: Micah Morton <mortonm@chromium.org>
2019-07-15LSM: SafeSetID: verify transitive constrainednessJann Horn
Someone might write a ruleset like the following, expecting that it securely constrains UID 1 to UIDs 1, 2 and 3: 1:2 1:3 However, because no constraints are applied to UIDs 2 and 3, an attacker with UID 1 can simply first switch to UID 2, then switch to any UID from there. The secure way to write this ruleset would be: 1:2 1:3 2:2 3:3 , which uses "transition to self" as a way to inhibit the default-allow policy without allowing anything specific. This is somewhat unintuitive. To make sure that policy authors don't accidentally write insecure policies because of this, let the kernel verify that a new ruleset does not contain any entries that are constrained, but transitively unconstrained. Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Micah Morton <mortonm@chromium.org>
2019-07-15LSM: SafeSetID: add read handlerJann Horn
For debugging a running system, it is very helpful to be able to see what policy the system is using. Add a read handler that can dump out a copy of the loaded policy. Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Micah Morton <mortonm@chromium.org>
2019-07-15LSM: SafeSetID: rewrite userspace API to atomic updatesJann Horn
The current API of the SafeSetID LSM uses one write() per rule, and applies each written rule instantly. This has several downsides: - While a policy is being loaded, once a single parent-child pair has been loaded, the parent is restricted to that specific child, even if subsequent rules would allow transitions to other child UIDs. This means that during policy loading, set*uid() can randomly fail. - To replace the policy without rebooting, it is necessary to first flush all old rules. This creates a time window in which no constraints are placed on the use of CAP_SETUID. - If we want to perform sanity checks on the final policy, this requires that the policy isn't constructed in a piecemeal fashion without telling the kernel when it's done. Other kernel APIs - including things like the userns code and netfilter - avoid this problem by performing updates atomically. Luckily, SafeSetID hasn't landed in a stable (upstream) release yet, so maybe it's not too late to completely change the API. The new API for SafeSetID is: If you want to change the policy, open "safesetid/whitelist_policy" and write the entire policy, newline-delimited, in there. Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Micah Morton <mortonm@chromium.org>
2019-07-15LSM: SafeSetID: fix userns handling in securityfsJann Horn
Looking at current_cred() in write handlers is bad form, stop doing that. Also, let's just require that the write is coming from the initial user namespace. Especially SAFESETID_WHITELIST_FLUSH requires privilege over all namespaces, and SAFESETID_WHITELIST_ADD should probably require it as well. Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Micah Morton <mortonm@chromium.org>
2019-07-15LSM: SafeSetID: refactor policy parsingJann Horn
In preparation for changing the policy parsing logic, refactor the line parsing logic to be less verbose and move it into a separate function. Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Micah Morton <mortonm@chromium.org>
2019-02-12LSM: fix return value check in safesetid_init_securityfs()Wei Yongjun
In case of error, the function securityfs_create_dir() returns ERR_PTR() and never returns NULL. The NULL test in the return value check should be replaced with IS_ERR(). Fixes: aeca4e2ca65c ("LSM: add SafeSetID module that gates setid calls") Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com> Acked-by: Kees Cook <keescook@chromium.org> Signed-off-by: James Morris <james.morris@microsoft.com>
2019-01-25LSM: add SafeSetID module that gates setid callsMicah Morton
SafeSetID gates the setid family of syscalls to restrict UID/GID transitions from a given UID/GID to only those approved by a system-wide whitelist. These restrictions also prohibit the given UIDs/GIDs from obtaining auxiliary privileges associated with CAP_SET{U/G}ID, such as allowing a user to set up user namespace UID mappings. For now, only gating the set*uid family of syscalls is supported, with support for set*gid coming in a future patch set. Signed-off-by: Micah Morton <mortonm@chromium.org> Acked-by: Kees Cook <keescook@chromium.org> Signed-off-by: James Morris <james.morris@microsoft.com>