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2019-09-17LSM: SafeSetID: Stop releasing uninitialized rulesetMicah Morton1-1/+2
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: fix use of literal -1 in capable hookJann Horn1-1/+1
The capable() hook returns an error number. -EPERM is actually the same as -1, so this doesn't make a difference in behavior. Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Micah Morton <mortonm@chromium.org>
2019-07-15LSM: SafeSetID: verify transitive constrainednessJann Horn1-1/+37
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 Horn2-4/+32
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 Horn3-158/+144
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 Horn1-3/+3
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 Horn1-51/+33
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>
2019-07-15LSM: SafeSetID: refactor safesetid_security_capable()Jann Horn1-15/+26
At the moment, safesetid_security_capable() has two nested conditional blocks, and one big comment for all the logic. Chop it up and reduce the amount of indentation. Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Micah Morton <mortonm@chromium.org>
2019-07-15LSM: SafeSetID: refactor policy hash tableJann Horn2-44/+37
parent_kuid and child_kuid are kuids, there is no reason to make them uint64_t. (And anyway, in the kernel, the normal name for that would be u64, not uint64_t.) check_setuid_policy_hashtable_key() and check_setuid_policy_hashtable_key_value() are basically the same thing, merge them. Also fix the comment that claimed that (1<<8)==128. Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Micah Morton <mortonm@chromium.org>
2019-07-15LSM: SafeSetID: fix check for setresuid(new1, new2, new3)Jann Horn1-90/+35
With the old code, when a process with the (real,effective,saved) UID set (1,1,1) calls setresuid(2,3,4), safesetid_task_fix_setuid() only checks whether the transition 1->2 is permitted; the transitions 1->3 and 1->4 are not checked. Fix this. This is also a good opportunity to refactor safesetid_task_fix_setuid() to be less verbose - having one branch per set*uid() syscall is unnecessary. Note that this slightly changes semantics: The UID transition check for UIDs that were not in the old cred struct is now always performed against the policy of the RUID. I think that's more consistent anyway, since the RUID is also the one that decides whether any policy is enforced at all. Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Micah Morton <mortonm@chromium.org>
2019-07-15LSM: SafeSetID: fix pr_warn() to include newlineJann Horn1-2/+2
Fix the pr_warn() calls in the SafeSetID LSM to have newlines at the end. Without this, denial messages will be buffered as incomplete lines in log_output(), and will then only show up once something else prints into dmesg. Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Micah Morton <mortonm@chromium.org>
2019-07-09Merge branch 'siginfo-linus' of ↵Linus Torvalds1-2/+2
git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace Pull force_sig() argument change from Eric Biederman: "A source of error over the years has been that force_sig has taken a task parameter when it is only safe to use force_sig with the current task. The force_sig function is built for delivering synchronous signals such as SIGSEGV where the userspace application caused a synchronous fault (such as a page fault) and the kernel responded with a signal. Because the name force_sig does not make this clear, and because the force_sig takes a task parameter the function force_sig has been abused for sending other kinds of signals over the years. Slowly those have been fixed when the oopses have been tracked down. This set of changes fixes the remaining abusers of force_sig and carefully rips out the task parameter from force_sig and friends making this kind of error almost impossible in the future" * 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (27 commits) signal/x86: Move tsk inside of CONFIG_MEMORY_FAILURE in do_sigbus signal: Remove the signal number and task parameters from force_sig_info signal: Factor force_sig_info_to_task out of force_sig_info signal: Generate the siginfo in force_sig signal: Move the computation of force into send_signal and correct it. signal: Properly set TRACE_SIGNAL_LOSE_INFO in __send_signal signal: Remove the task parameter from force_sig_fault signal: Use force_sig_fault_to_task for the two calls that don't deliver to current signal: Explicitly call force_sig_fault on current signal/unicore32: Remove tsk parameter from __do_user_fault signal/arm: Remove tsk parameter from __do_user_fault signal/arm: Remove tsk parameter from ptrace_break signal/nds32: Remove tsk parameter from send_sigtrap signal/riscv: Remove tsk parameter from do_trap signal/sh: Remove tsk parameter from force_sig_info_fault signal/um: Remove task parameter from send_sigtrap signal/x86: Remove task parameter from send_sigtrap signal: Remove task parameter from force_sig_mceerr signal: Remove task parameter from force_sig signal: Remove task parameter from force_sigsegv ...
2019-05-27signal: Remove task parameter from force_sigEric W. Biederman1-2/+2
All of the remaining callers pass current into force_sig so remove the task parameter to make this obvious and to make misuse more difficult in the future. This also makes it clear force_sig passes current into force_sig_info. Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2019-05-21treewide: Add SPDX license identifier - Makefile/KconfigThomas Gleixner1-0/+1
Add SPDX license identifiers to all Make/Kconfig files which: - Have no license information of any form These files fall under the project license, GPL v2 only. The resulting SPDX license identifier is: GPL-2.0-only Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-02-12LSM: fix return value check in safesetid_init_securityfs()Wei Yongjun1-1/+1
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>
2019-01-30LSM: SafeSetID: remove unused includeMicah Morton1-1/+0
The include for asm/syscall.h was needed in a prior version of lsm.c that checked return values of syscall_get_nr, but since we did away with that part of the code this include is no longer necessary. Take out this include since it breaks builds for certain architectures. We no longer have any arch-specific code in SafeSetID. Signed-off-by: Micah Morton <mortonm@chromium.org> Signed-off-by: James Morris <james.morris@microsoft.com>
2019-01-29LSM: SafeSetID: 'depend' on CONFIG_SECURITYMicah Morton1-0/+2
This patch changes the Kconfig file for the SafeSetID LSM to depend on CONFIG_SECURITY as well as select CONFIG_SECURITYFS, since the policies for the LSM are configured through writing to securityfs. Signed-off-by: Micah Morton <mortonm@chromium.org> Signed-off-by: James Morris <james.morris@microsoft.com>
2019-01-29LSM: Add 'name' field for SafeSetID in DEFINE_LSMMicah Morton1-0/+1
Without this, system boot was crashing with: [0.174285] LSM: Security Framework initializing [0.175277] BUG: unable to handle kernel NULL pointer dereference ... [0.176272] Call Trace: [0.176272] ordered_lsm_parse+0x112/0x20b [0.176272] security_init+0x9b/0x3ab [0.176272] start_kernel+0x413/0x479 [0.176272] secondary_startup_64+0xa4/0xb0 Signed-off-by: Micah Morton <mortonm@chromium.org> Fixed-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 Morton5-0/+522
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>
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