On 2021-03-18 16:42, Paul Moore wrote:
> Of the three LSMs that implement the security_task_getsecid() LSM
> hook, all three LSMs provide the task's objective security
> credentials. This turns out to be unfortunate as most of the hook's
> callers seem to expect the task's subjective credentials, although
> a small handful of callers do correctly expect the objective
> credentials.
>
> This patch is the first step towards fixing the problem: it splits
> the existing security_task_getsecid() hook into two variants, one
> for the subjective creds, one for the objective creds.
>
> void security_task_getsecid_subj(struct task_struct *p,
> u32 *secid);
> void security_task_getsecid_obj(struct task_struct *p,
> u32 *secid);
>
> While this patch does fix all of the callers to use the correct
> variant, in order to keep this patch focused on the callers and to
> ease review, the LSMs continue to use the same implementation for
> both hooks. The net effect is that this patch should not change
> the behavior of the kernel in any way, it will be up to the latter
> LSM specific patches in this series to change the hook
> implementations and return the correct credentials.
>
> Acked-by: Mimi Zohar <zohar@xxxxxxxxxxxxx> (IMA)
> Signed-off-by: Paul Moore <paul@xxxxxxxxxxxxxx>
Audit: Acked-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
Reviewed-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
> ---
> drivers/android/binder.c | 11 ++++++++++-
> include/linux/cred.h | 2 +-
> include/linux/lsm_hook_defs.h | 5 ++++-
> include/linux/lsm_hooks.h | 12 +++++++++---
> include/linux/security.h | 10 ++++++++--
> kernel/audit.c | 4 ++--
> kernel/auditfilter.c | 3 ++-
> kernel/auditsc.c | 8 ++++----
> kernel/bpf/bpf_lsm.c | 3 ++-
> net/netlabel/netlabel_unlabeled.c | 2 +-
> net/netlabel/netlabel_user.h | 2 +-
> security/apparmor/lsm.c | 3 ++-
> security/integrity/ima/ima_appraise.c | 2 +-
> security/integrity/ima/ima_main.c | 14 +++++++-------
> security/security.c | 13 ++++++++++---
> security/selinux/hooks.c | 3 ++-
> security/smack/smack_lsm.c | 3 ++-
> 17 files changed, 68 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index c119736ca56a..61d235b6ccd8 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -2700,7 +2700,16 @@ static void binder_transaction(struct binder_proc *proc,
> u32 secid;
> size_t added_size;
>
> - security_task_getsecid(proc->tsk, &secid);
> + /*
> + * Arguably this should be the task's subjective LSM secid but
> + * we can't reliably access the subjective creds of a task
> + * other than our own so we must use the objective creds, which
> + * are safe to access. The downside is that if a task is
> + * temporarily overriding it's creds it will not be reflected
> + * here; however, it isn't clear that binder would handle that
> + * case well anyway.
> + */
> + security_task_getsecid_obj(proc->tsk, &secid);
> ret = security_secid_to_secctx(secid, &secctx, &secctx_sz);
> if (ret) {
> return_error = BR_FAILED_REPLY;
> diff --git a/include/linux/cred.h b/include/linux/cred.h
> index 4c6350503697..ac0e5f97d7d8 100644
> --- a/include/linux/cred.h
> +++ b/include/linux/cred.h
> @@ -140,7 +140,7 @@ struct cred {
> struct key *request_key_auth; /* assumed request_key authority */
> #endif
> #ifdef CONFIG_SECURITY
> - void *security; /* subjective LSM security */
> + void *security; /* LSM security */
> #endif
> struct user_struct *user; /* real user ID subscription */
> struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index 477a597db013..3ad8085e85e1 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -203,7 +203,10 @@ LSM_HOOK(int, 0, task_fix_setgid, struct cred *new, const struct cred * old,
> LSM_HOOK(int, 0, task_setpgid, struct task_struct *p, pid_t pgid)
> LSM_HOOK(int, 0, task_getpgid, struct task_struct *p)
> LSM_HOOK(int, 0, task_getsid, struct task_struct *p)
> -LSM_HOOK(void, LSM_RET_VOID, task_getsecid, struct task_struct *p, u32 *secid)
> +LSM_HOOK(void, LSM_RET_VOID, task_getsecid_subj,
> + struct task_struct *p, u32 *secid)
> +LSM_HOOK(void, LSM_RET_VOID, task_getsecid_obj,
> + struct task_struct *p, u32 *secid)
> LSM_HOOK(int, 0, task_setnice, struct task_struct *p, int nice)
> LSM_HOOK(int, 0, task_setioprio, struct task_struct *p, int ioprio)
> LSM_HOOK(int, 0, task_getioprio, struct task_struct *p)
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index fb7f3193753d..e25d31fe787e 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -707,9 +707,15 @@
> * @p.
> * @p contains the task_struct for the process.
> * Return 0 if permission is granted.
> - * @task_getsecid:
> - * Retrieve the security identifier of the process @p.
> - * @p contains the task_struct for the process and place is into @secid.
> + * @task_getsecid_subj:
> + * Retrieve the subjective security identifier of the task_struct in @p
> + * and return it in @secid. Special care must be taken to ensure that @p
> + * is the either the "current" task, or the caller has exclusive access
> + * to @p.
> + * In case of failure, @secid will be set to zero.
> + * @task_getsecid_obj:
> + * Retrieve the objective security identifier of the task_struct in @p
> + * and return it in @secid.
> * In case of failure, @secid will be set to zero.
> *
> * @task_setnice:
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 8aeebd6646dc..9c490bc437f5 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -414,7 +414,8 @@ int security_task_fix_setgid(struct cred *new, const struct cred *old,
> int security_task_setpgid(struct task_struct *p, pid_t pgid);
> int security_task_getpgid(struct task_struct *p);
> int security_task_getsid(struct task_struct *p);
> -void security_task_getsecid(struct task_struct *p, u32 *secid);
> +void security_task_getsecid_subj(struct task_struct *p, u32 *secid);
> +void security_task_getsecid_obj(struct task_struct *p, u32 *secid);
> int security_task_setnice(struct task_struct *p, int nice);
> int security_task_setioprio(struct task_struct *p, int ioprio);
> int security_task_getioprio(struct task_struct *p);
> @@ -1098,7 +1099,12 @@ static inline int security_task_getsid(struct task_struct *p)
> return 0;
> }
>
> -static inline void security_task_getsecid(struct task_struct *p, u32 *secid)
> +static inline void security_task_getsecid_subj(struct task_struct *p, u32 *secid)
> +{
> + *secid = 0;
> +}
> +
> +static inline void security_task_getsecid_obj(struct task_struct *p, u32 *secid)
> {
> *secid = 0;
> }
> diff --git a/kernel/audit.c b/kernel/audit.c
> index 551a394bc8f4..121d37e700a6 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -2132,7 +2132,7 @@ int audit_log_task_context(struct audit_buffer *ab)
> int error;
> u32 sid;
>
> - security_task_getsecid(current, &sid);
> + security_task_getsecid_subj(current, &sid);
> if (!sid)
> return 0;
>
> @@ -2353,7 +2353,7 @@ int audit_signal_info(int sig, struct task_struct *t)
> audit_sig_uid = auid;
> else
> audit_sig_uid = uid;
> - security_task_getsecid(current, &audit_sig_sid);
> + security_task_getsecid_subj(current, &audit_sig_sid);
> }
>
> return audit_signal_info_syscall(t);
> diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
> index 333b3bcfc545..db2c6b59dfc3 100644
> --- a/kernel/auditfilter.c
> +++ b/kernel/auditfilter.c
> @@ -1359,7 +1359,8 @@ int audit_filter(int msgtype, unsigned int listtype)
> case AUDIT_SUBJ_SEN:
> case AUDIT_SUBJ_CLR:
> if (f->lsm_rule) {
> - security_task_getsecid(current, &sid);
> + security_task_getsecid_subj(current,
> + &sid);
> result = security_audit_rule_match(sid,
> f->type, f->op, f->lsm_rule);
> }
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index 47fb48f42c93..9973865cbf13 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -667,7 +667,7 @@ static int audit_filter_rules(struct task_struct *tsk,
> logged upon error */
> if (f->lsm_rule) {
> if (need_sid) {
> - security_task_getsecid(tsk, &sid);
> + security_task_getsecid_subj(tsk, &sid);
> need_sid = 0;
> }
> result = security_audit_rule_match(sid, f->type,
> @@ -2400,7 +2400,7 @@ void __audit_ptrace(struct task_struct *t)
> context->target_auid = audit_get_loginuid(t);
> context->target_uid = task_uid(t);
> context->target_sessionid = audit_get_sessionid(t);
> - security_task_getsecid(t, &context->target_sid);
> + security_task_getsecid_obj(t, &context->target_sid);
> memcpy(context->target_comm, t->comm, TASK_COMM_LEN);
> }
>
> @@ -2427,7 +2427,7 @@ int audit_signal_info_syscall(struct task_struct *t)
> ctx->target_auid = audit_get_loginuid(t);
> ctx->target_uid = t_uid;
> ctx->target_sessionid = audit_get_sessionid(t);
> - security_task_getsecid(t, &ctx->target_sid);
> + security_task_getsecid_obj(t, &ctx->target_sid);
> memcpy(ctx->target_comm, t->comm, TASK_COMM_LEN);
> return 0;
> }
> @@ -2448,7 +2448,7 @@ int audit_signal_info_syscall(struct task_struct *t)
> axp->target_auid[axp->pid_count] = audit_get_loginuid(t);
> axp->target_uid[axp->pid_count] = t_uid;
> axp->target_sessionid[axp->pid_count] = audit_get_sessionid(t);
> - security_task_getsecid(t, &axp->target_sid[axp->pid_count]);
> + security_task_getsecid_obj(t, &axp->target_sid[axp->pid_count]);
> memcpy(axp->target_comm[axp->pid_count], t->comm, TASK_COMM_LEN);
> axp->pid_count++;
>
> diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c
> index 1622a44d1617..0ff58259ccf8 100644
> --- a/kernel/bpf/bpf_lsm.c
> +++ b/kernel/bpf/bpf_lsm.c
> @@ -209,7 +209,8 @@ BTF_ID(func, bpf_lsm_socket_socketpair)
>
> BTF_ID(func, bpf_lsm_syslog)
> BTF_ID(func, bpf_lsm_task_alloc)
> -BTF_ID(func, bpf_lsm_task_getsecid)
> +BTF_ID(func, bpf_lsm_task_getsecid_subj)
> +BTF_ID(func, bpf_lsm_task_getsecid_obj)
> BTF_ID(func, bpf_lsm_task_prctl)
> BTF_ID(func, bpf_lsm_task_setscheduler)
> BTF_ID(func, bpf_lsm_task_to_inode)
> diff --git a/net/netlabel/netlabel_unlabeled.c b/net/netlabel/netlabel_unlabeled.c
> index ccb491642811..3e6ac9b790b1 100644
> --- a/net/netlabel/netlabel_unlabeled.c
> +++ b/net/netlabel/netlabel_unlabeled.c
> @@ -1539,7 +1539,7 @@ int __init netlbl_unlabel_defconf(void)
> /* Only the kernel is allowed to call this function and the only time
> * it is called is at bootup before the audit subsystem is reporting
> * messages so don't worry to much about these values. */
> - security_task_getsecid(current, &audit_info.secid);
> + security_task_getsecid_subj(current, &audit_info.secid);
> audit_info.loginuid = GLOBAL_ROOT_UID;
> audit_info.sessionid = 0;
>
> diff --git a/net/netlabel/netlabel_user.h b/net/netlabel/netlabel_user.h
> index 3c67afce64f1..b9ba8112b3c5 100644
> --- a/net/netlabel/netlabel_user.h
> +++ b/net/netlabel/netlabel_user.h
> @@ -34,7 +34,7 @@
> static inline void netlbl_netlink_auditinfo(struct sk_buff *skb,
> struct netlbl_audit *audit_info)
> {
> - security_task_getsecid(current, &audit_info->secid);
> + security_task_getsecid_subj(current, &audit_info->secid);
> audit_info->loginuid = audit_get_loginuid(current);
> audit_info->sessionid = audit_get_sessionid(current);
> }
> diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
> index 240a53387e6b..f72406fe1bf2 100644
> --- a/security/apparmor/lsm.c
> +++ b/security/apparmor/lsm.c
> @@ -1252,7 +1252,8 @@ static struct security_hook_list apparmor_hooks[] __lsm_ro_after_init = {
>
> LSM_HOOK_INIT(task_free, apparmor_task_free),
> LSM_HOOK_INIT(task_alloc, apparmor_task_alloc),
> - LSM_HOOK_INIT(task_getsecid, apparmor_task_getsecid),
> + LSM_HOOK_INIT(task_getsecid_subj, apparmor_task_getsecid),
> + LSM_HOOK_INIT(task_getsecid_obj, apparmor_task_getsecid),
> LSM_HOOK_INIT(task_setrlimit, apparmor_task_setrlimit),
> LSM_HOOK_INIT(task_kill, apparmor_task_kill),
>
> diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
> index 565e33ff19d0..4e5eb0236278 100644
> --- a/security/integrity/ima/ima_appraise.c
> +++ b/security/integrity/ima/ima_appraise.c
> @@ -76,7 +76,7 @@ int ima_must_appraise(struct user_namespace *mnt_userns, struct inode *inode,
> if (!ima_appraise)
> return 0;
>
> - security_task_getsecid(current, &secid);
> + security_task_getsecid_subj(current, &secid);
> return ima_match_policy(mnt_userns, inode, current_cred(), secid, func,
> mask, IMA_APPRAISE | IMA_HASH, NULL, NULL, NULL);
> }
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index 9ef748ea829f..b85d9e429426 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -391,7 +391,7 @@ int ima_file_mmap(struct file *file, unsigned long prot)
> u32 secid;
>
> if (file && (prot & PROT_EXEC)) {
> - security_task_getsecid(current, &secid);
> + security_task_getsecid_subj(current, &secid);
> return process_measurement(file, current_cred(), secid, NULL,
> 0, MAY_EXEC, MMAP_CHECK);
> }
> @@ -429,7 +429,7 @@ int ima_file_mprotect(struct vm_area_struct *vma, unsigned long prot)
> !(prot & PROT_EXEC) || (vma->vm_flags & VM_EXEC))
> return 0;
>
> - security_task_getsecid(current, &secid);
> + security_task_getsecid_subj(current, &secid);
> inode = file_inode(vma->vm_file);
> action = ima_get_action(file_mnt_user_ns(vma->vm_file), inode,
> current_cred(), secid, MAY_EXEC, MMAP_CHECK,
> @@ -470,7 +470,7 @@ int ima_bprm_check(struct linux_binprm *bprm)
> int ret;
> u32 secid;
>
> - security_task_getsecid(current, &secid);
> + security_task_getsecid_subj(current, &secid);
> ret = process_measurement(bprm->file, current_cred(), secid, NULL, 0,
> MAY_EXEC, BPRM_CHECK);
> if (ret)
> @@ -495,7 +495,7 @@ int ima_file_check(struct file *file, int mask)
> {
> u32 secid;
>
> - security_task_getsecid(current, &secid);
> + security_task_getsecid_subj(current, &secid);
> return process_measurement(file, current_cred(), secid, NULL, 0,
> mask & (MAY_READ | MAY_WRITE | MAY_EXEC |
> MAY_APPEND), FILE_CHECK);
> @@ -686,7 +686,7 @@ int ima_read_file(struct file *file, enum kernel_read_file_id read_id,
>
> /* Read entire file for all partial reads. */
> func = read_idmap[read_id] ?: FILE_CHECK;
> - security_task_getsecid(current, &secid);
> + security_task_getsecid_subj(current, &secid);
> return process_measurement(file, current_cred(), secid, NULL,
> 0, MAY_READ, func);
> }
> @@ -729,7 +729,7 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size,
> }
>
> func = read_idmap[read_id] ?: FILE_CHECK;
> - security_task_getsecid(current, &secid);
> + security_task_getsecid_subj(current, &secid);
> return process_measurement(file, current_cred(), secid, buf, size,
> MAY_READ, func);
> }
> @@ -872,7 +872,7 @@ void process_buffer_measurement(struct user_namespace *mnt_userns,
> * buffer measurements.
> */
> if (func) {
> - security_task_getsecid(current, &secid);
> + security_task_getsecid_subj(current, &secid);
> action = ima_get_action(mnt_userns, inode, current_cred(),
> secid, 0, func, &pcr, &template,
> func_data);
> diff --git a/security/security.c b/security/security.c
> index 5ac96b16f8fa..ee76d6c2f852 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -1762,12 +1762,19 @@ int security_task_getsid(struct task_struct *p)
> return call_int_hook(task_getsid, 0, p);
> }
>
> -void security_task_getsecid(struct task_struct *p, u32 *secid)
> +void security_task_getsecid_subj(struct task_struct *p, u32 *secid)
> {
> *secid = 0;
> - call_void_hook(task_getsecid, p, secid);
> + call_void_hook(task_getsecid_subj, p, secid);
> }
> -EXPORT_SYMBOL(security_task_getsecid);
> +EXPORT_SYMBOL(security_task_getsecid_subj);
> +
> +void security_task_getsecid_obj(struct task_struct *p, u32 *secid)
> +{
> + *secid = 0;
> + call_void_hook(task_getsecid_obj, p, secid);
> +}
> +EXPORT_SYMBOL(security_task_getsecid_obj);
>
> int security_task_setnice(struct task_struct *p, int nice)
> {
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index eca9fc0ba764..24ca545c6e1b 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -7149,7 +7149,8 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = {
> LSM_HOOK_INIT(task_setpgid, selinux_task_setpgid),
> LSM_HOOK_INIT(task_getpgid, selinux_task_getpgid),
> LSM_HOOK_INIT(task_getsid, selinux_task_getsid),
> - LSM_HOOK_INIT(task_getsecid, selinux_task_getsecid),
> + LSM_HOOK_INIT(task_getsecid_subj, selinux_task_getsecid),
> + LSM_HOOK_INIT(task_getsecid_obj, selinux_task_getsecid),
> LSM_HOOK_INIT(task_setnice, selinux_task_setnice),
> LSM_HOOK_INIT(task_setioprio, selinux_task_setioprio),
> LSM_HOOK_INIT(task_getioprio, selinux_task_getioprio),
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 12a45e61c1a5..f546fb832f30 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -4759,7 +4759,8 @@ static struct security_hook_list smack_hooks[] __lsm_ro_after_init = {
> LSM_HOOK_INIT(task_setpgid, smack_task_setpgid),
> LSM_HOOK_INIT(task_getpgid, smack_task_getpgid),
> LSM_HOOK_INIT(task_getsid, smack_task_getsid),
> - LSM_HOOK_INIT(task_getsecid, smack_task_getsecid),
> + LSM_HOOK_INIT(task_getsecid_subj, smack_task_getsecid),
> + LSM_HOOK_INIT(task_getsecid_obj, smack_task_getsecid),
> LSM_HOOK_INIT(task_setnice, smack_task_setnice),
> LSM_HOOK_INIT(task_setioprio, smack_task_setioprio),
> LSM_HOOK_INIT(task_getioprio, smack_task_getioprio),
>
> --
> Linux-audit mailing list
> Linux-audit@xxxxxxxxxx
> https://listman.redhat.com/mailman/listinfo/linux-audit
- RGB
--
Richard Guy Briggs <rgb@xxxxxxxxxx>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635
