From a8478a602913dc89a7cd2060e613edecd07e1dbd Mon Sep 17 00:00:00 2001 From: David Howells Date: Tue, 14 Jan 2020 17:07:13 +0000 Subject: [PATCH] smack: Implement the watch_key and post_notification hooks Implement the watch_key security hook in Smack to make sure that a key grants the caller Read permission in order to set a watch on a key. Also implement the post_notification security hook to make sure that the notification source is granted Write permission by the watch queue. For the moment, the watch_devices security hook is left unimplemented as it's not obvious what the object should be since the queue is global and didn't previously exist. Signed-off-by: David Howells Acked-by: Casey Schaufler --- include/linux/lsm_audit.h | 1 + security/smack/smack_lsm.c | 83 +++++++++++++++++++++++++++++++++++++- 2 files changed, 83 insertions(+), 1 deletion(-) diff --git a/include/linux/lsm_audit.h b/include/linux/lsm_audit.h index 99d629fd9944..28f23b341c1c 100644 --- a/include/linux/lsm_audit.h +++ b/include/linux/lsm_audit.h @@ -75,6 +75,7 @@ struct common_audit_data { #define LSM_AUDIT_DATA_IBPKEY 13 #define LSM_AUDIT_DATA_IBENDPORT 14 #define LSM_AUDIT_DATA_LOCKDOWN 15 +#define LSM_AUDIT_DATA_NOTIFICATION 16 union { struct path path; struct dentry *dentry; diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index 0d6bb53efe74..3c4d4836da4a 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -41,6 +41,7 @@ #include #include #include +#include #include "smack.h" #define TRANS_TRUE "TRUE" @@ -4284,7 +4285,7 @@ static int smack_key_permission(key_ref_t key_ref, if (tkp == NULL) return -EACCES; - if (smack_privileged_cred(CAP_MAC_OVERRIDE, cred)) + if (smack_privileged(CAP_MAC_OVERRIDE)) return 0; #ifdef CONFIG_AUDIT @@ -4326,8 +4327,81 @@ static int smack_key_getsecurity(struct key *key, char **_buffer) return length; } + +#ifdef CONFIG_KEY_NOTIFICATIONS +/** + * smack_watch_key - Smack access to watch a key for notifications. + * @key: The key to be watched + * + * Return 0 if the @watch->cred has permission to read from the key object and + * an error otherwise. + */ +static int smack_watch_key(struct key *key) +{ + struct smk_audit_info ad; + struct smack_known *tkp = smk_of_current(); + int rc; + + if (key == NULL) + return -EINVAL; + /* + * If the key hasn't been initialized give it access so that + * it may do so. + */ + if (key->security == NULL) + return 0; + /* + * This should not occur + */ + if (tkp == NULL) + return -EACCES; + + if (smack_privileged_cred(CAP_MAC_OVERRIDE, current_cred())) + return 0; + +#ifdef CONFIG_AUDIT + smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_KEY); + ad.a.u.key_struct.key = key->serial; + ad.a.u.key_struct.key_desc = key->description; +#endif + rc = smk_access(tkp, key->security, MAY_READ, &ad); + rc = smk_bu_note("key watch", tkp, key->security, MAY_READ, rc); + return rc; +} +#endif /* CONFIG_KEY_NOTIFICATIONS */ #endif /* CONFIG_KEYS */ +#ifdef CONFIG_WATCH_QUEUE +/** + * smack_post_notification - Smack access to post a notification to a queue + * @w_cred: The credentials of the watcher. + * @cred: The credentials of the event source (may be NULL). + * @n: The notification message to be posted. + */ +static int smack_post_notification(const struct cred *w_cred, + const struct cred *cred, + struct watch_notification *n) +{ + struct smk_audit_info ad; + struct smack_known *subj, *obj; + int rc; + + /* Always let maintenance notifications through. */ + if (n->type == WATCH_TYPE_META) + return 0; + + if (!cred) + return 0; + subj = smk_of_task(smack_cred(cred)); + obj = smk_of_task(smack_cred(w_cred)); + + smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_NOTIFICATION); + rc = smk_access(subj, obj, MAY_WRITE, &ad); + rc = smk_bu_note("notification", subj, obj, MAY_WRITE, rc); + return rc; +} +#endif /* CONFIG_WATCH_QUEUE */ + /* * Smack Audit hooks * @@ -4716,8 +4790,15 @@ static struct security_hook_list smack_hooks[] __lsm_ro_after_init = { LSM_HOOK_INIT(key_free, smack_key_free), LSM_HOOK_INIT(key_permission, smack_key_permission), LSM_HOOK_INIT(key_getsecurity, smack_key_getsecurity), +#ifdef CONFIG_KEY_NOTIFICATIONS + LSM_HOOK_INIT(watch_key, smack_watch_key), +#endif #endif /* CONFIG_KEYS */ +#ifdef CONFIG_WATCH_QUEUE + LSM_HOOK_INIT(post_notification, smack_post_notification), +#endif + /* Audit hooks */ #ifdef CONFIG_AUDIT LSM_HOOK_INIT(audit_rule_init, smack_audit_rule_init),