On Mon, Apr 06, 2020 at 05:01:49PM -0700, Casey Schaufler wrote: > Create a new entry "display" in the procfs attr directory for > controlling which LSM security information is displayed for a > process. A process can only read or write its own display value. > > The name of an active LSM that supplies hooks for > human readable data may be written to "display" to set the > value. The name of the LSM currently in use can be read from > "display". At this point there can only be one LSM capable > of display active. A helper function lsm_task_display() is > provided to get the display slot for a task_struct. > > Setting the "display" requires that all security modules using > setprocattr hooks allow the action. Each security module is > responsible for defining its policy. > > AppArmor hook provided by John Johansen <[email protected]> > SELinux hook provided by Stephen Smalley <[email protected]> > > Acked-by: Stephen Smalley <[email protected]> > Acked-by: Paul Moore <[email protected]> > Signed-off-by: Casey Schaufler <[email protected]>
Reviewed-by: Kees Cook <[email protected]> -Kees > --- > fs/proc/base.c | 1 + > include/linux/lsm_hooks.h | 15 +++ > security/apparmor/include/apparmor.h | 3 +- > security/apparmor/lsm.c | 32 +++++ > security/security.c | 167 ++++++++++++++++++++++++--- > security/selinux/hooks.c | 11 ++ > security/selinux/include/classmap.h | 2 +- > security/smack/smack_lsm.c | 7 ++ > 8 files changed, 219 insertions(+), 19 deletions(-) > > diff --git a/fs/proc/base.c b/fs/proc/base.c > index c7c64272b0fa..505331ab7a14 100644 > --- a/fs/proc/base.c > +++ b/fs/proc/base.c > @@ -2743,6 +2743,7 @@ static const struct pid_entry attr_dir_stuff[] = { > ATTR(NULL, "fscreate", 0666), > ATTR(NULL, "keycreate", 0666), > ATTR(NULL, "sockcreate", 0666), > + ATTR(NULL, "display", 0666), > #ifdef CONFIG_SECURITY_SMACK > DIR("smack", 0555, > proc_smack_attr_dir_inode_ops, proc_smack_attr_dir_ops), > diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h > index 7eb808cde051..2bf82e1cf347 100644 > --- a/include/linux/lsm_hooks.h > +++ b/include/linux/lsm_hooks.h > @@ -2186,4 +2186,19 @@ static inline void security_delete_hooks(struct > security_hook_list *hooks, > > extern int lsm_inode_alloc(struct inode *inode); > > +/** > + * lsm_task_display - the "display" LSM for this task > + * @task: The task to report on > + * > + * Returns the task's display LSM slot. > + */ > +static inline int lsm_task_display(struct task_struct *task) > +{ > + int *display = task->security; > + > + if (display) > + return *display; > + return LSMBLOB_INVALID; > +} > + > #endif /* ! __LINUX_LSM_HOOKS_H */ > diff --git a/security/apparmor/include/apparmor.h > b/security/apparmor/include/apparmor.h > index 1fbabdb565a8..b1622fcb4394 100644 > --- a/security/apparmor/include/apparmor.h > +++ b/security/apparmor/include/apparmor.h > @@ -28,8 +28,9 @@ > #define AA_CLASS_SIGNAL 10 > #define AA_CLASS_NET 14 > #define AA_CLASS_LABEL 16 > +#define AA_CLASS_DISPLAY_LSM 17 > > -#define AA_CLASS_LAST AA_CLASS_LABEL > +#define AA_CLASS_LAST AA_CLASS_DISPLAY_LSM > > /* Control parameters settable through module/boot flags */ > extern enum audit_mode aa_g_audit; > diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c > index 146d75e5e021..16b992235c11 100644 > --- a/security/apparmor/lsm.c > +++ b/security/apparmor/lsm.c > @@ -612,6 +612,25 @@ static int apparmor_getprocattr(struct task_struct > *task, char *name, > return error; > } > > + > +static int profile_display_lsm(struct aa_profile *profile, > + struct common_audit_data *sa) > +{ > + struct aa_perms perms = { }; > + unsigned int state; > + > + state = PROFILE_MEDIATES(profile, AA_CLASS_DISPLAY_LSM); > + if (state) { > + aa_compute_perms(profile->policy.dfa, state, &perms); > + aa_apply_modes_to_perms(profile, &perms); > + aad(sa)->label = &profile->label; > + > + return aa_check_perms(profile, &perms, AA_MAY_WRITE, sa, NULL); > + } > + > + return 0; > +} > + > static int apparmor_setprocattr(const char *name, void *value, > size_t size) > { > @@ -623,6 +642,19 @@ static int apparmor_setprocattr(const char *name, void > *value, > if (size == 0) > return -EINVAL; > > + /* LSM infrastructure does actual setting of display if allowed */ > + if (!strcmp(name, "display")) { > + struct aa_profile *profile; > + struct aa_label *label; > + > + aad(&sa)->info = "set display lsm"; > + label = begin_current_label_crit_section(); > + error = fn_for_each_confined(label, profile, > + profile_display_lsm(profile, &sa)); > + end_current_label_crit_section(label); > + return error; > + } > + > /* AppArmor requires that the buffer must be null terminated atm */ > if (args[size - 1] != '\0') { > /* null terminate */ > diff --git a/security/security.c b/security/security.c > index bf71066ea19b..0208652ad53a 100644 > --- a/security/security.c > +++ b/security/security.c > @@ -75,7 +75,14 @@ static struct kmem_cache *lsm_file_cache; > static struct kmem_cache *lsm_inode_cache; > > char *lsm_names; > -static struct lsm_blob_sizes blob_sizes __lsm_ro_after_init; > + > +/* > + * The task blob includes the "display" slot used for > + * chosing which module presents contexts. > + */ > +static struct lsm_blob_sizes blob_sizes __lsm_ro_after_init = { > + .lbs_task = sizeof(int), > +}; > > /* Boot-time LSM user choice */ > static __initdata const char *chosen_lsm_order; > @@ -470,8 +477,10 @@ static int lsm_append(const char *new, char **result) > > /* > * Current index to use while initializing the lsmblob secid list. > + * Pointers to the LSM id structures for local use. > */ > static int lsm_slot __lsm_ro_after_init; > +static struct lsm_id *lsm_slotlist[LSMBLOB_ENTRIES]; > > /** > * security_add_hooks - Add a modules hooks to the hook lists. > @@ -491,6 +500,7 @@ void __init security_add_hooks(struct security_hook_list > *hooks, int count, > if (lsmid->slot == LSMBLOB_NEEDED) { > if (lsm_slot >= LSMBLOB_ENTRIES) > panic("%s Too many LSMs registered.\n", __func__); > + lsm_slotlist[lsm_slot] = lsmid; > lsmid->slot = lsm_slot++; > init_debug("%s assigned lsmblob slot %d\n", lsmid->lsm, > lsmid->slot); > @@ -620,6 +630,8 @@ int lsm_inode_alloc(struct inode *inode) > */ > static int lsm_task_alloc(struct task_struct *task) > { > + int *display; > + > if (blob_sizes.lbs_task == 0) { > task->security = NULL; > return 0; > @@ -628,6 +640,15 @@ static int lsm_task_alloc(struct task_struct *task) > task->security = kzalloc(blob_sizes.lbs_task, GFP_KERNEL); > if (task->security == NULL) > return -ENOMEM; > + > + /* > + * The start of the task blob contains the "display" LSM slot number. > + * Start with it set to the invalid slot number, indicating that the > + * default first registered LSM be displayed. > + */ > + display = task->security; > + *display = LSMBLOB_INVALID; > + > return 0; > } > > @@ -1583,14 +1604,26 @@ int security_file_open(struct file *file) > > int security_task_alloc(struct task_struct *task, unsigned long clone_flags) > { > + int *odisplay = current->security; > + int *ndisplay; > int rc = lsm_task_alloc(task); > > - if (rc) > + if (unlikely(rc)) > return rc; > + > rc = call_int_hook(task_alloc, 0, task, clone_flags); > - if (unlikely(rc)) > + if (unlikely(rc)) { > security_task_free(task); > - return rc; > + return rc; > + } > + > + if (odisplay) { > + ndisplay = task->security; > + if (ndisplay) > + *ndisplay = *odisplay; > + } > + > + return 0; > } > > void security_task_free(struct task_struct *task) > @@ -1987,23 +2020,110 @@ int security_getprocattr(struct task_struct *p, > const char *lsm, char *name, > char **value) > { > struct security_hook_list *hp; > + int display = lsm_task_display(current); > + int slot = 0; > + > + if (!strcmp(name, "display")) { > + /* > + * lsm_slot will be 0 if there are no displaying modules. > + */ > + if (lsm_slot == 0) > + return -EINVAL; > + > + /* > + * Only allow getting the current process' display. > + * There are too few reasons to get another process' > + * display and too many LSM policy issues. > + */ > + if (current != p) > + return -EINVAL; > + > + display = lsm_task_display(p); > + if (display != LSMBLOB_INVALID) > + slot = display; > + *value = kstrdup(lsm_slotlist[slot]->lsm, GFP_KERNEL); > + if (*value) > + return strlen(*value); > + return -ENOMEM; > + } > > hlist_for_each_entry(hp, &security_hook_heads.getprocattr, list) { > if (lsm != NULL && strcmp(lsm, hp->lsmid->lsm)) > continue; > + if (lsm == NULL && display != LSMBLOB_INVALID && > + display != hp->lsmid->slot) > + continue; > return hp->hook.getprocattr(p, name, value); > } > return -EINVAL; > } > > +/** > + * security_setprocattr - Set process attributes via /proc > + * @lsm: name of module involved, or NULL > + * @name: name of the attribute > + * @value: value to set the attribute to > + * @size: size of the value > + * > + * Set the process attribute for the specified security module > + * to the specified value. Note that this can only be used to set > + * the process attributes for the current, or "self" process. > + * The /proc code has already done this check. > + * > + * Returns 0 on success, an appropriate code otherwise. > + */ > int security_setprocattr(const char *lsm, const char *name, void *value, > size_t size) > { > struct security_hook_list *hp; > + char *termed; > + char *copy; > + int *display = current->security; > + int rc = -EINVAL; > + int slot = 0; > + > + if (!strcmp(name, "display")) { > + /* > + * Change the "display" value only if all the security > + * modules that support setting a procattr allow it. > + * It is assumed that all such security modules will be > + * cooperative. > + */ > + if (size == 0) > + return -EINVAL; > + > + hlist_for_each_entry(hp, &security_hook_heads.setprocattr, > + list) { > + rc = hp->hook.setprocattr(name, value, size); > + if (rc < 0) > + return rc; > + } > + > + rc = -EINVAL; > + > + copy = kmemdup_nul(value, size, GFP_KERNEL); > + if (copy == NULL) > + return -ENOMEM; > + > + termed = strsep(©, " \n"); > + > + for (slot = 0; slot < lsm_slot; slot++) > + if (!strcmp(termed, lsm_slotlist[slot]->lsm)) { > + *display = lsm_slotlist[slot]->slot; > + rc = size; > + break; > + } > + > + kfree(termed); > + return rc; > + } > > hlist_for_each_entry(hp, &security_hook_heads.setprocattr, list) { > if (lsm != NULL && strcmp(lsm, hp->lsmid->lsm)) > continue; > + if (lsm == NULL && *display != LSMBLOB_INVALID && > + *display != hp->lsmid->slot) > + continue; > return hp->hook.setprocattr(name, value, size); > } > return -EINVAL; > @@ -2023,15 +2143,15 @@ EXPORT_SYMBOL(security_ismaclabel); > int security_secid_to_secctx(struct lsmblob *blob, char **secdata, u32 > *seclen) > { > struct security_hook_list *hp; > - int rc; > + int display = lsm_task_display(current); > > hlist_for_each_entry(hp, &security_hook_heads.secid_to_secctx, list) { > if (WARN_ON(hp->lsmid->slot < 0 || hp->lsmid->slot >= lsm_slot)) > continue; > - rc = hp->hook.secid_to_secctx(blob->secid[hp->lsmid->slot], > - secdata, seclen); > - if (rc != 0) > - return rc; > + if (display == LSMBLOB_INVALID || display == hp->lsmid->slot) > + return hp->hook.secid_to_secctx( > + blob->secid[hp->lsmid->slot], > + secdata, seclen); > } > return 0; > } > @@ -2041,16 +2161,15 @@ int security_secctx_to_secid(const char *secdata, u32 > seclen, > struct lsmblob *blob) > { > struct security_hook_list *hp; > - int rc; > + int display = lsm_task_display(current); > > lsmblob_init(blob, 0); > hlist_for_each_entry(hp, &security_hook_heads.secctx_to_secid, list) { > if (WARN_ON(hp->lsmid->slot < 0 || hp->lsmid->slot >= lsm_slot)) > continue; > - rc = hp->hook.secctx_to_secid(secdata, seclen, > - &blob->secid[hp->lsmid->slot]); > - if (rc != 0) > - return rc; > + if (display == LSMBLOB_INVALID || display == hp->lsmid->slot) > + return hp->hook.secctx_to_secid(secdata, seclen, > + &blob->secid[hp->lsmid->slot]); > } > return 0; > } > @@ -2058,7 +2177,14 @@ EXPORT_SYMBOL(security_secctx_to_secid); > > void security_release_secctx(char *secdata, u32 seclen) > { > - call_void_hook(release_secctx, secdata, seclen); > + struct security_hook_list *hp; > + int display = lsm_task_display(current); > + > + hlist_for_each_entry(hp, &security_hook_heads.release_secctx, list) > + if (display == LSMBLOB_INVALID || display == hp->lsmid->slot) { > + hp->hook.release_secctx(secdata, seclen); > + return; > + } > } > EXPORT_SYMBOL(security_release_secctx); > > @@ -2183,8 +2309,15 @@ EXPORT_SYMBOL(security_sock_rcv_skb); > int security_socket_getpeersec_stream(struct socket *sock, char __user > *optval, > int __user *optlen, unsigned len) > { > - return call_int_hook(socket_getpeersec_stream, -ENOPROTOOPT, sock, > - optval, optlen, len); > + int display = lsm_task_display(current); > + struct security_hook_list *hp; > + > + hlist_for_each_entry(hp, &security_hook_heads.socket_getpeersec_stream, > + list) > + if (display == LSMBLOB_INVALID || display == hp->lsmid->slot) > + return hp->hook.socket_getpeersec_stream(sock, optval, > + optlen, len); > + return -ENOPROTOOPT; > } > > int security_socket_getpeersec_dgram(struct socket *sock, struct sk_buff > *skb, > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c > index 84eef6af53e7..dc5e3bd2b770 100644 > --- a/security/selinux/hooks.c > +++ b/security/selinux/hooks.c > @@ -6299,6 +6299,17 @@ static int selinux_setprocattr(const char *name, void > *value, size_t size) > /* > * Basic control over ability to set these attributes at all. > */ > + > + /* > + * For setting display, we only perform a permission check; > + * the actual update to the display value is handled by the > + * LSM framework. > + */ > + if (!strcmp(name, "display")) > + return avc_has_perm(&selinux_state, > + mysid, mysid, SECCLASS_PROCESS2, > + PROCESS2__SETDISPLAY, NULL); > + > if (!strcmp(name, "exec")) > error = avc_has_perm(&selinux_state, > mysid, mysid, SECCLASS_PROCESS, > diff --git a/security/selinux/include/classmap.h > b/security/selinux/include/classmap.h > index 986f3ac14282..ba36a55b5ea4 100644 > --- a/security/selinux/include/classmap.h > +++ b/security/selinux/include/classmap.h > @@ -52,7 +52,7 @@ struct security_class_mapping secclass_map[] = { > "execmem", "execstack", "execheap", "setkeycreate", > "setsockcreate", "getrlimit", NULL } }, > { "process2", > - { "nnp_transition", "nosuid_transition", NULL } }, > + { "nnp_transition", "nosuid_transition", "setdisplay", NULL } }, > { "system", > { "ipc_info", "syslog_read", "syslog_mod", > "syslog_console", "module_request", "module_load", NULL } }, > diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c > index 12e01d450dd4..00a304861657 100644 > --- a/security/smack/smack_lsm.c > +++ b/security/smack/smack_lsm.c > @@ -3510,6 +3510,13 @@ static int smack_setprocattr(const char *name, void > *value, size_t size) > struct smack_known_list_elem *sklep; > int rc; > > + /* > + * Allow the /proc/.../attr/current and SO_PEERSEC "display" > + * to be reset at will. > + */ > + if (strcmp(name, "display") == 0) > + return 0; > + > if (!smack_privileged(CAP_MAC_ADMIN) && list_empty(&tsp->smk_relabel)) > return -EPERM; > > -- > 2.24.1 > -- Kees Cook -- Linux-audit mailing list [email protected] https://www.redhat.com/mailman/listinfo/linux-audit
