LSM: generalize flag passing to security_capable

This patch provides a general mechanism for passing flags to the
security_capable LSM hook. It replaces the specific 'audit' flag that is
used to tell security_capable whether it should log an audit message for
the given capability check. The reason for generalizing this flag
passing is so we can add an additional flag that signifies whether
security_capable is being called by a setid syscall (which is needed by
the proposed SafeSetID LSM).

Signed-off-by: Micah Morton <mortonm@chromium.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: James Morris <james.morris@microsoft.com>

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 40511a8a5ae63a87383f8be4790965c21fa85c3b..195707210975e11cc7b2876630413acea20f20c5 100644 (file)
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1270,7 +1270,7 @@
  *     @cred contains the credentials to use.
  *     @ns contains the user namespace we want the capability in
  *     @cap contains the capability <include/linux/capability.h>.
- *     @audit contains whether to write an audit message or not
+ *     @opts contains options for the capable check <include/linux/security.h>
  *     Return 0 if the capability is granted for @tsk.
  * @syslog:
  *     Check permission before accessing the kernel message ring or changing
@@ -1446,8 +1446,10 @@ union security_list_options {
                        const kernel_cap_t *effective,
                        const kernel_cap_t *inheritable,
                        const kernel_cap_t *permitted);
-       int (*capable)(const struct cred *cred, struct user_namespace *ns,
-                       int cap, int audit);
+       int (*capable)(const struct cred *cred,
+                       struct user_namespace *ns,
+                       int cap,
+                       unsigned int opts);
        int (*quotactl)(int cmds, int type, int id, struct super_block *sb);
        int (*quota_on)(struct dentry *dentry);
        int (*syslog)(int type);

diff --git a/include/linux/security.h b/include/linux/security.h
index b2c5333ed4b5a658b54cf1519083619790913fb0..13537a49ae97258f46065f809443c7dc5f44e59f 100644 (file)
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -54,9 +54,12 @@ struct xattr;
 struct xfrm_sec_ctx;
 struct mm_struct;
 
+/* Default (no) options for the capable function */
+#define CAP_OPT_NONE 0x0
 /* If capable should audit the security request */
-#define SECURITY_CAP_NOAUDIT 0
-#define SECURITY_CAP_AUDIT 1
+#define CAP_OPT_NOAUDIT BIT(1)
+/* If capable is being called by a setid function */
+#define CAP_OPT_INSETID BIT(2)
 
 /* LSM Agnostic defines for sb_set_mnt_opts */
 #define SECURITY_LSM_NATIVE_LABELS     1
@@ -72,7 +75,7 @@ enum lsm_event {
 
 /* These functions are in security/commoncap.c */
 extern int cap_capable(const struct cred *cred, struct user_namespace *ns,
-                      int cap, int audit);
+                      int cap, unsigned int opts);
 extern int cap_settime(const struct timespec64 *ts, const struct timezone *tz);
 extern int cap_ptrace_access_check(struct task_struct *child, unsigned int mode);
 extern int cap_ptrace_traceme(struct task_struct *parent);
@@ -207,10 +210,10 @@ int security_capset(struct cred *new, const struct cred *old,
                    const kernel_cap_t *effective,
                    const kernel_cap_t *inheritable,
                    const kernel_cap_t *permitted);
-int security_capable(const struct cred *cred, struct user_namespace *ns,
-                       int cap);
-int security_capable_noaudit(const struct cred *cred, struct user_namespace *ns,
-                            int cap);
+int security_capable(const struct cred *cred,
+                      struct user_namespace *ns,
+                      int cap,
+                      unsigned int opts);
 int security_quotactl(int cmds, int type, int id, struct super_block *sb);
 int security_quota_on(struct dentry *dentry);
 int security_syslog(int type);
@@ -464,14 +467,11 @@ static inline int security_capset(struct cred *new,
 }
 
 static inline int security_capable(const struct cred *cred,
-                                  struct user_namespace *ns, int cap)
+                                  struct user_namespace *ns,
+                                  int cap,
+                                  unsigned int opts)
 {
-       return cap_capable(cred, ns, cap, SECURITY_CAP_AUDIT);
-}
-
-static inline int security_capable_noaudit(const struct cred *cred,
-                                          struct user_namespace *ns, int cap) {
-       return cap_capable(cred, ns, cap, SECURITY_CAP_NOAUDIT);
+       return cap_capable(cred, ns, cap, opts);
 }
 
 static inline int security_quotactl(int cmds, int type, int id,

diff --git a/kernel/capability.c b/kernel/capability.c
index 1e1c0236f55b5b05b54caa49dca62c1b7e2d5819..7718d7dcadc7abf9d2bd62cf5e7b84aeba351ea3 100644 (file)
--- a/kernel/capability.c
+++ b/kernel/capability.c
@@ -299,7 +299,7 @@ bool has_ns_capability(struct task_struct *t,
        int ret;
 
        rcu_read_lock();
-       ret = security_capable(__task_cred(t), ns, cap);
+       ret = security_capable(__task_cred(t), ns, cap, CAP_OPT_NONE);
        rcu_read_unlock();
 
        return (ret == 0);
@@ -340,7 +340,7 @@ bool has_ns_capability_noaudit(struct task_struct *t,
        int ret;
 
        rcu_read_lock();
-       ret = security_capable_noaudit(__task_cred(t), ns, cap);
+       ret = security_capable(__task_cred(t), ns, cap, CAP_OPT_NOAUDIT);
        rcu_read_unlock();
 
        return (ret == 0);
@@ -363,7 +363,9 @@ bool has_capability_noaudit(struct task_struct *t, int cap)
        return has_ns_capability_noaudit(t, &init_user_ns, cap);
 }
 
-static bool ns_capable_common(struct user_namespace *ns, int cap, bool audit)
+static bool ns_capable_common(struct user_namespace *ns,
+                             int cap,
+                             unsigned int opts)
 {
        int capable;
 
@@ -372,8 +374,7 @@ static bool ns_capable_common(struct user_namespace *ns, int cap, bool audit)
                BUG();
        }
 
-       capable = audit ? security_capable(current_cred(), ns, cap) :
-                         security_capable_noaudit(current_cred(), ns, cap);
+       capable = security_capable(current_cred(), ns, cap, opts);
        if (capable == 0) {
                current->flags |= PF_SUPERPRIV;
                return true;
@@ -394,7 +395,7 @@ static bool ns_capable_common(struct user_namespace *ns, int cap, bool audit)
  */
 bool ns_capable(struct user_namespace *ns, int cap)
 {
-       return ns_capable_common(ns, cap, true);
+       return ns_capable_common(ns, cap, CAP_OPT_NONE);
 }
 EXPORT_SYMBOL(ns_capable);
 
@@ -412,7 +413,7 @@ EXPORT_SYMBOL(ns_capable);
  */
 bool ns_capable_noaudit(struct user_namespace *ns, int cap)
 {
-       return ns_capable_common(ns, cap, false);
+       return ns_capable_common(ns, cap, CAP_OPT_NOAUDIT);
 }
 EXPORT_SYMBOL(ns_capable_noaudit);
 
@@ -448,10 +449,11 @@ EXPORT_SYMBOL(capable);
 bool file_ns_capable(const struct file *file, struct user_namespace *ns,
                     int cap)
 {
+
        if (WARN_ON_ONCE(!cap_valid(cap)))
                return false;
 
-       if (security_capable(file->f_cred, ns, cap) == 0)
+       if (security_capable(file->f_cred, ns, cap, CAP_OPT_NONE) == 0)
                return true;
 
        return false;
@@ -500,10 +502,12 @@ bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns)
 {
        int ret = 0;  /* An absent tracer adds no restrictions */
        const struct cred *cred;
+
        rcu_read_lock();
        cred = rcu_dereference(tsk->ptracer_cred);
        if (cred)
-               ret = security_capable_noaudit(cred, ns, CAP_SYS_PTRACE);
+               ret = security_capable(cred, ns, CAP_SYS_PTRACE,
+                                      CAP_OPT_NOAUDIT);
        rcu_read_unlock();
        return (ret == 0);
 }

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index d7f538847b8413eca4c91112f26a563623a59904..38a77800def68dd5762312274f15cf274499d057 100644 (file)
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -443,8 +443,8 @@ static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
         * behavior of privileged children.
         */
        if (!task_no_new_privs(current) &&
-           security_capable_noaudit(current_cred(), current_user_ns(),
-                                    CAP_SYS_ADMIN) != 0)
+           security_capable(current_cred(), current_user_ns(),
+                                    CAP_SYS_ADMIN, CAP_OPT_NOAUDIT) != 0)
                return ERR_PTR(-EACCES);
 
        /* Allocate a new seccomp_filter */

diff --git a/security/apparmor/capability.c b/security/apparmor/capability.c
index 253ef6e9d445355c0f1d3379d319a8e052541032..752f73980e3085e81daceccc269f45e09b812b3c 100644 (file)
--- a/security/apparmor/capability.c
+++ b/security/apparmor/capability.c
@@ -110,13 +110,13 @@ static int audit_caps(struct common_audit_data *sa, struct aa_profile *profile,
  * profile_capable - test if profile allows use of capability @cap
  * @profile: profile being enforced    (NOT NULL, NOT unconfined)
  * @cap: capability to test if allowed
- * @audit: whether an audit record should be generated
+ * @opts: CAP_OPT_NOAUDIT bit determines whether audit record is generated
  * @sa: audit data (MAY BE NULL indicating no auditing)
  *
  * Returns: 0 if allowed else -EPERM
  */
-static int profile_capable(struct aa_profile *profile, int cap, int audit,
-                          struct common_audit_data *sa)
+static int profile_capable(struct aa_profile *profile, int cap,
+                          unsigned int opts, struct common_audit_data *sa)
 {
        int error;
 
@@ -126,7 +126,7 @@ static int profile_capable(struct aa_profile *profile, int cap, int audit,
        else
                error = -EPERM;
 
-       if (audit == SECURITY_CAP_NOAUDIT) {
+       if (opts & CAP_OPT_NOAUDIT) {
                if (!COMPLAIN_MODE(profile))
                        return error;
                /* audit the cap request in complain mode but note that it
@@ -142,13 +142,13 @@ static int profile_capable(struct aa_profile *profile, int cap, int audit,
  * aa_capable - test permission to use capability
  * @label: label being tested for capability (NOT NULL)
  * @cap: capability to be tested
- * @audit: whether an audit record should be generated
+ * @opts: CAP_OPT_NOAUDIT bit determines whether audit record is generated
  *
  * Look up capability in profile capability set.
  *
  * Returns: 0 on success, or else an error code.
  */
-int aa_capable(struct aa_label *label, int cap, int audit)
+int aa_capable(struct aa_label *label, int cap, unsigned int opts)
 {
        struct aa_profile *profile;
        int error = 0;
@@ -156,7 +156,7 @@ int aa_capable(struct aa_label *label, int cap, int audit)
 
        sa.u.cap = cap;
        error = fn_for_each_confined(label, profile,
-                       profile_capable(profile, cap, audit, &sa));
+                       profile_capable(profile, cap, opts, &sa));
 
        return error;
 }

diff --git a/security/apparmor/include/capability.h b/security/apparmor/include/capability.h
index e0304e2aeb7ffda8fe6862c235526c22dd10db20..1b3663b6ab129d649cd7d9604ae4e4cb2a51ef7b 100644 (file)
--- a/security/apparmor/include/capability.h
+++ b/security/apparmor/include/capability.h
@@ -40,7 +40,7 @@ struct aa_caps {
 
 extern struct aa_sfs_entry aa_sfs_entry_caps[];
 
-int aa_capable(struct aa_label *label, int cap, int audit);
+int aa_capable(struct aa_label *label, int cap, unsigned int opts);
 
 static inline void aa_free_cap_rules(struct aa_caps *caps)
 {

diff --git a/security/apparmor/ipc.c b/security/apparmor/ipc.c
index 527ea1557120ece44aa0c04d901bfa3e8d9b9422..aacd1e95cb596888fec63a00de1124092c11a188 100644 (file)
--- a/security/apparmor/ipc.c
+++ b/security/apparmor/ipc.c
@@ -107,7 +107,8 @@ static int profile_tracer_perm(struct aa_profile *tracer,
        aad(sa)->label = &tracer->label;
        aad(sa)->peer = tracee;
        aad(sa)->request = 0;
-       aad(sa)->error = aa_capable(&tracer->label, CAP_SYS_PTRACE, 1);
+       aad(sa)->error = aa_capable(&tracer->label, CAP_SYS_PTRACE,
+                                   CAP_OPT_NONE);
 
        return aa_audit(AUDIT_APPARMOR_AUTO, tracer, sa, audit_ptrace_cb);
 }

diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index 60ef71268ccf96ea49b7e08b7b8a5c72c8b314fb..b6c395e2acd05f59fbd8edd11dce19e99ba7ef47 100644 (file)
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -172,14 +172,14 @@ static int apparmor_capget(struct task_struct *target, kernel_cap_t *effective,
 }
 
 static int apparmor_capable(const struct cred *cred, struct user_namespace *ns,
-                           int cap, int audit)
+                           int cap, unsigned int opts)
 {
        struct aa_label *label;
        int error = 0;
 
        label = aa_get_newest_cred_label(cred);
        if (!unconfined(label))
-               error = aa_capable(label, cap, audit);
+               error = aa_capable(label, cap, opts);
        aa_put_label(label);
 
        return error;

diff --git a/security/apparmor/resource.c b/security/apparmor/resource.c
index 95fd26d09757f2c7fb7b39d541e1aa6fdc923a5d..552ed09cb47e75829a60e202b3a9465cecefe246 100644 (file)
--- a/security/apparmor/resource.c
+++ b/security/apparmor/resource.c
@@ -124,7 +124,7 @@ int aa_task_setrlimit(struct aa_label *label, struct task_struct *task,
         */
 
        if (label != peer &&
-           aa_capable(label, CAP_SYS_RESOURCE, SECURITY_CAP_NOAUDIT) != 0)
+           aa_capable(label, CAP_SYS_RESOURCE, CAP_OPT_NOAUDIT) != 0)
                error = fn_for_each(label, profile,
                                audit_resource(profile, resource,
                                               new_rlim->rlim_max, peer,

diff --git a/security/commoncap.c b/security/commoncap.c
index 52e04136bfa81aa4af70a5e32a8ab41bb9bc8ee4..188eaf59f82f26b52c7540981d6ae71f022b6840 100644 (file)
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -68,7 +68,7 @@ static void warn_setuid_and_fcaps_mixed(const char *fname)
  * kernel's capable() and has_capability() returns 1 for this case.
  */
 int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
-               int cap, int audit)
+               int cap, unsigned int opts)
 {
        struct user_namespace *ns = targ_ns;
 
@@ -222,12 +222,11 @@ int cap_capget(struct task_struct *target, kernel_cap_t *effective,
  */
 static inline int cap_inh_is_capped(void)
 {
-
        /* they are so limited unless the current task has the CAP_SETPCAP
         * capability
         */
        if (cap_capable(current_cred(), current_cred()->user_ns,
-                       CAP_SETPCAP, SECURITY_CAP_AUDIT) == 0)
+                       CAP_SETPCAP, CAP_OPT_NONE) == 0)
                return 0;
        return 1;
 }
@@ -1208,8 +1207,9 @@ int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
                    || ((old->securebits & SECURE_ALL_LOCKS & ~arg2))   /*[2]*/
                    || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS))   /*[3]*/
                    || (cap_capable(current_cred(),
-                                   current_cred()->user_ns, CAP_SETPCAP,
-                                   SECURITY_CAP_AUDIT) != 0)           /*[4]*/
+                                   current_cred()->user_ns,
+                                   CAP_SETPCAP,
+                                   CAP_OPT_NONE) != 0)                 /*[4]*/
                        /*
                         * [1] no changing of bits that are locked
                         * [2] no unlocking of locks
@@ -1304,9 +1304,10 @@ int cap_vm_enough_memory(struct mm_struct *mm, long pages)
 {
        int cap_sys_admin = 0;
 
-       if (cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN,
-                       SECURITY_CAP_NOAUDIT) == 0)
+       if (cap_capable(current_cred(), &init_user_ns,
+                               CAP_SYS_ADMIN, CAP_OPT_NOAUDIT) == 0)
                cap_sys_admin = 1;
+
        return cap_sys_admin;
 }
 
@@ -1325,7 +1326,7 @@ int cap_mmap_addr(unsigned long addr)
 
        if (addr < dac_mmap_min_addr) {
                ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
-                                 SECURITY_CAP_AUDIT);
+                                 CAP_OPT_NONE);
                /* set PF_SUPERPRIV if it turns out we allow the low mmap */
                if (ret == 0)
                        current->flags |= PF_SUPERPRIV;

diff --git a/security/security.c b/security/security.c
index 953fc3ea18a95909ca6f5b7ada985470864a9453..a618e22df5c64d2f90e024b8878fcd5eb4179572 100644 (file)
--- a/security/security.c
+++ b/security/security.c
@@ -689,16 +689,12 @@ int security_capset(struct cred *new, const struct cred *old,
                                effective, inheritable, permitted);
 }
 
-int security_capable(const struct cred *cred, struct user_namespace *ns,
-                    int cap)
+int security_capable(const struct cred *cred,
+                    struct user_namespace *ns,
+                    int cap,
+                    unsigned int opts)
 {
-       return call_int_hook(capable, 0, cred, ns, cap, SECURITY_CAP_AUDIT);
-}
-
-int security_capable_noaudit(const struct cred *cred, struct user_namespace *ns,
-                            int cap)
-{
-       return call_int_hook(capable, 0, cred, ns, cap, SECURITY_CAP_NOAUDIT);
+       return call_int_hook(capable, 0, cred, ns, cap, opts);
 }
 
 int security_quotactl(int cmds, int type, int id, struct super_block *sb)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index d98e1d8d18f6d8f4a13f562d2189ff5b7e409a05..b2ee49f938f1977b7944c2c3b9071b178e9d5b20 100644 (file)
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1578,7 +1578,7 @@ static inline u32 signal_to_av(int sig)
 
 /* Check whether a task is allowed to use a capability. */
 static int cred_has_capability(const struct cred *cred,
-                              int cap, int audit, bool initns)
+                              int cap, unsigned int opts, bool initns)
 {
        struct common_audit_data ad;
        struct av_decision avd;
@@ -1605,7 +1605,7 @@ static int cred_has_capability(const struct cred *cred,
 
        rc = avc_has_perm_noaudit(&selinux_state,
                                  sid, sid, sclass, av, 0, &avd);
-       if (audit == SECURITY_CAP_AUDIT) {
+       if (!(opts & CAP_OPT_NOAUDIT)) {
                int rc2 = avc_audit(&selinux_state,
                                    sid, sid, sclass, av, &avd, rc, &ad, 0);
                if (rc2)
@@ -2125,9 +2125,9 @@ static int selinux_capset(struct cred *new, const struct cred *old,
  */
 
 static int selinux_capable(const struct cred *cred, struct user_namespace *ns,
-                          int cap, int audit)
+                          int cap, unsigned int opts)
 {
-       return cred_has_capability(cred, cap, audit, ns == &init_user_ns);
+       return cred_has_capability(cred, cap, opts, ns == &init_user_ns);
 }
 
 static int selinux_quotactl(int cmds, int type, int id, struct super_block *sb)
@@ -2201,7 +2201,7 @@ static int selinux_vm_enough_memory(struct mm_struct *mm, long pages)
        int rc, cap_sys_admin = 0;
 
        rc = cred_has_capability(current_cred(), CAP_SYS_ADMIN,
-                                SECURITY_CAP_NOAUDIT, true);
+                                CAP_OPT_NOAUDIT, true);
        if (rc == 0)
                cap_sys_admin = 1;
 
@@ -2988,11 +2988,11 @@ static int selinux_inode_getattr(const struct path *path)
 static bool has_cap_mac_admin(bool audit)
 {
        const struct cred *cred = current_cred();
-       int cap_audit = audit ? SECURITY_CAP_AUDIT : SECURITY_CAP_NOAUDIT;
+       unsigned int opts = audit ? CAP_OPT_NONE : CAP_OPT_NOAUDIT;
 
-       if (cap_capable(cred, &init_user_ns, CAP_MAC_ADMIN, cap_audit))
+       if (cap_capable(cred, &init_user_ns, CAP_MAC_ADMIN, opts))
                return false;
-       if (cred_has_capability(cred, CAP_MAC_ADMIN, cap_audit, true))
+       if (cred_has_capability(cred, CAP_MAC_ADMIN, opts, true))
                return false;
        return true;
 }
@@ -3387,7 +3387,7 @@ static int selinux_file_ioctl(struct file *file, unsigned int cmd,
        case KDSKBENT:
        case KDSKBSENT:
                error = cred_has_capability(cred, CAP_SYS_TTY_CONFIG,
-                                           SECURITY_CAP_AUDIT, true);
+                                           CAP_OPT_NONE, true);
                break;
 
        /* default case assumes that the command will go

diff --git a/security/smack/smack_access.c b/security/smack/smack_access.c
index 489d49a20b470e694d6047e43d24246049f8afaf..fe2ce3a658220b6ba5810ef11952960667eac1ce 100644 (file)
--- a/security/smack/smack_access.c
+++ b/security/smack/smack_access.c
@@ -640,7 +640,7 @@ bool smack_privileged_cred(int cap, const struct cred *cred)
        struct smack_known_list_elem *sklep;
        int rc;
 
-       rc = cap_capable(cred, &init_user_ns, cap, SECURITY_CAP_AUDIT);
+       rc = cap_capable(cred, &init_user_ns, cap, CAP_OPT_NONE);
        if (rc)
                return false;