diff options
Diffstat (limited to 'security/commoncap.c')
| -rw-r--r-- | security/commoncap.c | 111 |
1 files changed, 73 insertions, 38 deletions
diff --git a/security/commoncap.c b/security/commoncap.c index cefad323a0b1..6bd4adeb4795 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -27,6 +27,9 @@ #include <linux/mnt_idmapping.h> #include <uapi/linux/lsm.h> +#define CREATE_TRACE_POINTS +#include <trace/events/capability.h> + /* * If a non-root user executes a setuid-root binary in * !secure(SECURE_NOROOT) mode, then we raise capabilities. @@ -50,24 +53,24 @@ static void warn_setuid_and_fcaps_mixed(const char *fname) } /** - * cap_capable - Determine whether a task has a particular effective capability + * cap_capable_helper - Determine whether a task has a particular effective + * capability. * @cred: The credentials to use - * @targ_ns: The user namespace in which we need the capability + * @target_ns: The user namespace of the resource being accessed + * @cred_ns: The user namespace of the credentials * @cap: The capability to check for - * @opts: Bitmask of options defined in include/linux/security.h * * Determine whether the nominated task has the specified capability amongst * its effective set, returning 0 if it does, -ve if it does not. * - * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable() - * and has_capability() functions. That is, it has the reverse semantics: - * cap_has_capability() returns 0 when a task has a capability, but the - * kernel's capable() and has_capability() returns 1 for this case. + * See cap_capable for more details. */ -int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, - int cap, unsigned int opts) +static inline int cap_capable_helper(const struct cred *cred, + struct user_namespace *target_ns, + const struct user_namespace *cred_ns, + int cap) { - struct user_namespace *ns = targ_ns; + struct user_namespace *ns = target_ns; /* See if cred has the capability in the target user namespace * by examining the target user namespace and all of the target @@ -75,21 +78,21 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, */ for (;;) { /* Do we have the necessary capabilities? */ - if (ns == cred->user_ns) + if (likely(ns == cred_ns)) return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; /* * If we're already at a lower level than we're looking for, * we're done searching. */ - if (ns->level <= cred->user_ns->level) + if (ns->level <= cred_ns->level) return -EPERM; /* * The owner of the user namespace in the parent of the * user namespace has all caps. */ - if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid)) + if ((ns->parent == cred_ns) && uid_eq(ns->owner, cred->euid)) return 0; /* @@ -103,6 +106,32 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, } /** + * cap_capable - Determine whether a task has a particular effective capability + * @cred: The credentials to use + * @target_ns: The user namespace of the resource being accessed + * @cap: The capability to check for + * @opts: Bitmask of options defined in include/linux/security.h (unused) + * + * Determine whether the nominated task has the specified capability amongst + * its effective set, returning 0 if it does, -ve if it does not. + * + * NOTE WELL: cap_capable() has reverse semantics to the capable() call + * and friends. That is cap_capable() returns an int 0 when a task has + * a capability, while the kernel's capable(), has_ns_capability(), + * has_ns_capability_noaudit(), and has_capability_noaudit() return a + * bool true (1) for this case. + */ +int cap_capable(const struct cred *cred, struct user_namespace *target_ns, + int cap, unsigned int opts) +{ + const struct user_namespace *cred_ns = cred->user_ns; + int ret = cap_capable_helper(cred, target_ns, cred_ns, cap); + + trace_cap_capable(cred, target_ns, cred_ns, cap, ret); + return ret; +} + +/** * cap_settime - Determine whether the current process may set the system clock * @ts: The time to set * @tz: The timezone to set @@ -827,12 +856,6 @@ static void handle_privileged_root(struct linux_binprm *bprm, bool has_fcap, #define __cap_full(field, cred) \ cap_issubset(CAP_FULL_SET, cred->cap_##field) -static inline bool __is_setuid(struct cred *new, const struct cred *old) -{ return !uid_eq(new->euid, old->uid); } - -static inline bool __is_setgid(struct cred *new, const struct cred *old) -{ return !gid_eq(new->egid, old->gid); } - /* * 1) Audit candidate if current->cap_effective is set * @@ -862,7 +885,7 @@ static inline bool nonroot_raised_pE(struct cred *new, const struct cred *old, (root_privileged() && __is_suid(root, new) && !__cap_full(effective, new)) || - (!__is_setuid(new, old) && + (uid_eq(new->euid, old->euid) && ((has_fcap && __cap_gained(permitted, new, old)) || __cap_gained(ambient, new, old)))) @@ -888,7 +911,7 @@ int cap_bprm_creds_from_file(struct linux_binprm *bprm, const struct file *file) /* Process setpcap binaries and capabilities for uid 0 */ const struct cred *old = current_cred(); struct cred *new = bprm->cred; - bool effective = false, has_fcap = false, is_setid; + bool effective = false, has_fcap = false, id_changed; int ret; kuid_t root_uid; @@ -912,9 +935,9 @@ int cap_bprm_creds_from_file(struct linux_binprm *bprm, const struct file *file) * * In addition, if NO_NEW_PRIVS, then ensure we get no new privs. */ - is_setid = __is_setuid(new, old) || __is_setgid(new, old); + id_changed = !uid_eq(new->euid, old->euid) || !in_group_p(new->egid); - if ((is_setid || __cap_gained(permitted, new, old)) && + if ((id_changed || __cap_gained(permitted, new, old)) && ((bprm->unsafe & ~LSM_UNSAFE_PTRACE) || !ptracer_capable(current, new->user_ns))) { /* downgrade; they get no more than they had, and maybe less */ @@ -931,7 +954,7 @@ int cap_bprm_creds_from_file(struct linux_binprm *bprm, const struct file *file) new->sgid = new->fsgid = new->egid; /* File caps or setid cancels ambient. */ - if (has_fcap || is_setid) + if (has_fcap || id_changed) cap_clear(new->cap_ambient); /* @@ -964,7 +987,9 @@ int cap_bprm_creds_from_file(struct linux_binprm *bprm, const struct file *file) return -EPERM; /* Check for privilege-elevated exec. */ - if (is_setid || + if (id_changed || + !uid_eq(new->euid, old->uid) || + !gid_eq(new->egid, old->gid) || (!__is_real(root_uid, new) && (effective || __cap_grew(permitted, ambient, new)))) @@ -1302,21 +1327,38 @@ int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, & (old->securebits ^ arg2)) /*[1]*/ || ((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, - CAP_OPT_NONE) != 0) /*[4]*/ /* * [1] no changing of bits that are locked * [2] no unlocking of locks * [3] no setting of unsupported bits - * [4] doing anything requires privilege (go read about - * the "sendmail capabilities bug") */ ) /* cannot change a locked bit */ return -EPERM; + /* + * Doing anything requires privilege (go read about the + * "sendmail capabilities bug"), except for unprivileged bits. + * Indeed, the SECURE_ALL_UNPRIVILEGED bits are not + * restrictions enforced by the kernel but by user space on + * itself. + */ + if (cap_capable(current_cred(), current_cred()->user_ns, + CAP_SETPCAP, CAP_OPT_NONE) != 0) { + const unsigned long unpriv_and_locks = + SECURE_ALL_UNPRIVILEGED | + SECURE_ALL_UNPRIVILEGED << 1; + const unsigned long changed = old->securebits ^ arg2; + + /* For legacy reason, denies non-change. */ + if (!changed) + return -EPERM; + + /* Denies privileged changes. */ + if (changed & ~unpriv_and_locks) + return -EPERM; + } + new = prepare_creds(); if (!new) return -ENOMEM; @@ -1428,12 +1470,6 @@ int cap_mmap_addr(unsigned long addr) return ret; } -int cap_mmap_file(struct file *file, unsigned long reqprot, - unsigned long prot, unsigned long flags) -{ - return 0; -} - #ifdef CONFIG_SECURITY static const struct lsm_id capability_lsmid = { @@ -1453,7 +1489,6 @@ static struct security_hook_list capability_hooks[] __ro_after_init = { LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv), LSM_HOOK_INIT(inode_getsecurity, cap_inode_getsecurity), LSM_HOOK_INIT(mmap_addr, cap_mmap_addr), - LSM_HOOK_INIT(mmap_file, cap_mmap_file), LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid), LSM_HOOK_INIT(task_prctl, cap_task_prctl), LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler), |