[PATCH v2] LSM: generalize flag passing to security_capable
Casey Schaufler
casey at schaufler-ca.com
Mon Jan 7 18:16:44 UTC 2019
On 1/7/2019 9:55 AM, Micah Morton wrote:
> Checking in to see if there are any further comments on this patch now
> that the holidays are passed? It seems like a straightforward change
> to me, but let me know if there is anything I can clarify that isn't
> explained by the commit message.
>
> On Tue, Dec 18, 2018 at 2:37 PM <mortonm at chromium.org> wrote:
>> From: Micah Morton <mortonm at chromium.org>
>>
>> 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 at chromium.org>
>> ---
>> Changes since the last patch: Changed the code to use a bitmask instead
>> of a struct to represent the options passed to security_capable.
>>
>> include/linux/lsm_hooks.h | 8 +++++---
>> include/linux/security.h | 28 +++++++++++++-------------
>> kernel/capability.c | 22 +++++++++++---------
>> kernel/seccomp.c | 4 ++--
>> security/apparmor/capability.c | 14 ++++++-------
>> security/apparmor/include/capability.h | 2 +-
>> security/apparmor/ipc.c | 3 ++-
>> security/apparmor/lsm.c | 4 ++--
>> security/commoncap.c | 17 ++++++++--------
>> security/security.c | 14 +++++--------
>> security/selinux/hooks.c | 16 +++++++--------
>> security/smack/smack_access.c | 2 +-
>> 12 files changed, 69 insertions(+), 65 deletions(-)
>>
>> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
>> index aaeb7fa24dc4..ef955a44a782 100644
>> --- 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 d170a5b031f3..038e6779948c 100644
>> --- 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 SECURITY_CAP_DEFAULT 0x0
>> /* If capable should audit the security request */
>> -#define SECURITY_CAP_NOAUDIT 0
>> -#define SECURITY_CAP_AUDIT 1
>> +#define SECURITY_CAP_NOAUDIT 0x01
>> +/* If capable is being called by a setid function */
>> +#define SECURITY_CAP_INSETID 0x02
>>
>> /* 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);
>> @@ -233,10 +236,10 @@ 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);
>> @@ -492,14 +495,11 @@ 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);
>> }
Why get rid of security_capable_noaudit()?
>>
>> static inline int security_quotactl(int cmds, int type, int id,
>> diff --git a/kernel/capability.c b/kernel/capability.c
>> index 1e1c0236f55b..454576743b1b 100644
>> --- 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, SECURITY_CAP_DEFAULT);
>> 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, SECURITY_CAP_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, SECURITY_CAP_DEFAULT);
>> }
>> 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, SECURITY_CAP_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, SECURITY_CAP_DEFAULT) == 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,
>> + SECURITY_CAP_NOAUDIT);
>> rcu_read_unlock();
>> return (ret == 0);
>> }
>> diff --git a/kernel/seccomp.c b/kernel/seccomp.c
>> index f2ae2324c232..ddf615eb1bf7 100644
>> --- a/kernel/seccomp.c
>> +++ b/kernel/seccomp.c
>> @@ -383,8 +383,8 @@ 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, SECURITY_CAP_NOAUDIT) != 0)
>> return ERR_PTR(-EACCES);
>>
>> /* Allocate a new seccomp_filter */
>> diff --git a/security/apparmor/capability.c b/security/apparmor/capability.c
>> index 253ef6e9d445..0f6dca54b66e 100644
>> --- 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: SECURITY_CAP_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 & SECURITY_CAP_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: SECURITY_CAP_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 e0304e2aeb7f..1b3663b6ab12 100644
>> --- 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 527ea1557120..4a1da2313162 100644
>> --- 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,
>> + SECURITY_CAP_DEFAULT);
>>
>> return aa_audit(AUDIT_APPARMOR_AUTO, tracer, sa, audit_ptrace_cb);
>> }
>> diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
>> index 42446a216f3b..0bd817084fc1 100644
>> --- a/security/apparmor/lsm.c
>> +++ b/security/apparmor/lsm.c
>> @@ -176,14 +176,14 @@ 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/commoncap.c b/security/commoncap.c
>> index 232db019f051..3d8609192e17 100644
>> --- 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, SECURITY_CAP_DEFAULT) == 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,
>> + SECURITY_CAP_DEFAULT) != 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, SECURITY_CAP_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);
>> + SECURITY_CAP_DEFAULT);
>> /* 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 d670136dda2c..d2334697797a 100644
>> --- a/security/security.c
>> +++ b/security/security.c
>> @@ -294,16 +294,12 @@ 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 a67459eb62d5..a4b2e49213de 100644
>> --- a/security/selinux/hooks.c
>> +++ b/security/selinux/hooks.c
>> @@ -1769,7 +1769,7 @@ 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;
>> @@ -1796,7 +1796,7 @@ 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 & SECURITY_CAP_NOAUDIT)) {
>> int rc2 = avc_audit(&selinux_state,
>> sid, sid, sclass, av, &avd, rc, &ad, 0);
>> if (rc2)
>> @@ -2316,9 +2316,9 @@ 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)
>> @@ -3245,11 +3245,11 @@ 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 ? SECURITY_CAP_DEFAULT : SECURITY_CAP_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;
>> }
>> @@ -3649,7 +3649,7 @@ 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);
>> + SECURITY_CAP_DEFAULT, 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 9a4c0ad46518..fac2a21aa7d4 100644
>> --- 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, SECURITY_CAP_DEFAULT);
>> if (rc)
>> return false;
>>
>> --
>> 2.20.0.405.gbc1bbc6f85-goog
>>
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