/* * Copyright (C) 2007 Casey Schaufler <casey@schaufler-ca.com> * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, version 2. * * Author: * Casey Schaufler <casey@schaufler-ca.com> * */ #include <linux/types.h> #include <linux/slab.h> #include <linux/fs.h> #include <linux/sched.h> #include "smack.h" struct smack_known smack_known_huh = { .smk_known = "?", .smk_secid = 2, }; struct smack_known smack_known_hat = { .smk_known = "^", .smk_secid = 3, }; struct smack_known smack_known_star = { .smk_known = "*", .smk_secid = 4, }; struct smack_known smack_known_floor = { .smk_known = "_", .smk_secid = 5, }; struct smack_known smack_known_web = { .smk_known = "@", .smk_secid = 7, }; LIST_HEAD(smack_known_list); /* * The initial value needs to be bigger than any of the * known values above. */ static u32 smack_next_secid = 10; /* * what events do we log * can be overwritten at run-time by /smack/logging */ int log_policy = SMACK_AUDIT_DENIED; /** * smk_access_entry - look up matching access rule * @subject_label: a pointer to the subject's Smack label * @object_label: a pointer to the object's Smack label * @rule_list: the list of rules to search * * This function looks up the subject/object pair in the * access rule list and returns the access mode. If no * entry is found returns -ENOENT. * * NOTE: * * Earlier versions of this function allowed for labels that * were not on the label list. This was done to allow for * labels to come over the network that had never been seen * before on this host. Unless the receiving socket has the * star label this will always result in a failure check. The * star labeled socket case is now handled in the networking * hooks so there is no case where the label is not on the * label list. Checking to see if the address of two labels * is the same is now a reliable test. * * Do the object check first because that is more * likely to differ. * * Allowing write access implies allowing locking. */ int smk_access_entry(char *subject_label, char *object_label, struct list_head *rule_list) { int may = -ENOENT; struct smack_rule *srp; list_for_each_entry_rcu(srp, rule_list, list) { if (srp->smk_object->smk_known == object_label && srp->smk_subject->smk_known == subject_label) { may = srp->smk_access; break; } } /* * MAY_WRITE implies MAY_LOCK. */ if ((may & MAY_WRITE) == MAY_WRITE) may |= MAY_LOCK; return may; } /** * smk_access - determine if a subject has a specific access to an object * @subject: a pointer to the subject's Smack label entry * @object: a pointer to the object's Smack label entry * @request: the access requested, in "MAY" format * @a : a pointer to the audit data * * This function looks up the subject/object pair in the * access rule list and returns 0 if the access is permitted, * non zero otherwise. * * Smack labels are shared on smack_list */ int smk_access(struct smack_known *subject, struct smack_known *object, int request, struct smk_audit_info *a) { int may = MAY_NOT; int rc = 0; /* * Hardcoded comparisons. */ /* * A star subject can't access any object. */ if (subject == &smack_known_star) { rc = -EACCES; goto out_audit; } /* * An internet object can be accessed by any subject. * Tasks cannot be assigned the internet label. * An internet subject can access any object. */ if (object == &smack_known_web || subject == &smack_known_web) goto out_audit; /* * A star object can be accessed by any subject. */ if (object == &smack_known_star) goto out_audit; /* * An object can be accessed in any way by a subject * with the same label. */ if (subject->smk_known == object->smk_known) goto out_audit; /* * A hat subject can read or lock any object. * A floor object can be read or locked by any subject. */ if ((request & MAY_ANYREAD) == request || (request & MAY_LOCK) == request) { if (object == &smack_known_floor) goto out_audit; if (subject == &smack_known_hat) goto out_audit; } /* * Beyond here an explicit relationship is required. * If the requested access is contained in the available * access (e.g. read is included in readwrite) it's * good. A negative response from smk_access_entry() * indicates there is no entry for this pair. */ rcu_read_lock(); may = smk_access_entry(subject->smk_known, object->smk_known, &subject->smk_rules); rcu_read_unlock(); if (may <= 0 || (request & may) != request) { rc = -EACCES; goto out_audit; } #ifdef CONFIG_SECURITY_SMACK_BRINGUP /* * Return a positive value if using bringup mode. * This allows the hooks to identify checks that * succeed because of "b" rules. */ if (may & MAY_BRINGUP) rc = SMACK_BRINGUP_ALLOW; #endif out_audit: #ifdef CONFIG_SECURITY_SMACK_BRINGUP if (rc < 0) { if (object == smack_unconfined) rc = SMACK_UNCONFINED_OBJECT; if (subject == smack_unconfined) rc = SMACK_UNCONFINED_SUBJECT; } #endif #ifdef CONFIG_AUDIT if (a) smack_log(subject->smk_known, object->smk_known, request, rc, a); #endif return rc; } /** * smk_tskacc - determine if a task has a specific access to an object * @tsp: a pointer to the subject's task * @obj_known: a pointer to the object's label entry * @mode: the access requested, in "MAY" format * @a : common audit data * * This function checks the subject task's label/object label pair * in the access rule list and returns 0 if the access is permitted, * non zero otherwise. It allows that the task may have the capability * to override the rules. */ int smk_tskacc(struct task_smack *tsp, struct smack_known *obj_known, u32 mode, struct smk_audit_info *a) { struct smack_known *sbj_known = smk_of_task(tsp); int may; int rc; /* * Check the global rule list */ rc = smk_access(sbj_known, obj_known, mode, NULL); if (rc >= 0) { /* * If there is an entry in the task's rule list * it can further restrict access. */ may = smk_access_entry(sbj_known->smk_known, obj_known->smk_known, &tsp->smk_rules); if (may < 0) goto out_audit; if ((mode & may) == mode) goto out_audit; rc = -EACCES; } /* * Allow for priviliged to override policy. */ if (rc != 0 && smack_privileged(CAP_MAC_OVERRIDE)) rc = 0; out_audit: #ifdef CONFIG_AUDIT if (a) smack_log(sbj_known->smk_known, obj_known->smk_known, mode, rc, a); #endif return rc; } /** * smk_curacc - determine if current has a specific access to an object * @obj_known: a pointer to the object's Smack label entry * @mode: the access requested, in "MAY" format * @a : common audit data * * This function checks the current subject label/object label pair * in the access rule list and returns 0 if the access is permitted, * non zero otherwise. It allows that current may have the capability * to override the rules. */ int smk_curacc(struct smack_known *obj_known, u32 mode, struct smk_audit_info *a) { struct task_smack *tsp = current_security(); return smk_tskacc(tsp, obj_known, mode, a); } #ifdef CONFIG_AUDIT /** * smack_str_from_perm : helper to transalate an int to a * readable string * @string : the string to fill * @access : the int * */ static inline void smack_str_from_perm(char *string, int access) { int i = 0; if (access & MAY_READ) string[i++] = 'r'; if (access & MAY_WRITE) string[i++] = 'w'; if (access & MAY_EXEC) string[i++] = 'x'; if (access & MAY_APPEND) string[i++] = 'a'; if (access & MAY_TRANSMUTE) string[i++] = 't'; if (access & MAY_LOCK) string[i++] = 'l'; string[i] = '\0'; } /** * smack_log_callback - SMACK specific information * will be called by generic audit code * @ab : the audit_buffer * @a : audit_data * */ static void smack_log_callback(struct audit_buffer *ab, void *a) { struct common_audit_data *ad = a; struct smack_audit_data *sad = ad->smack_audit_data; audit_log_format(ab, "lsm=SMACK fn=%s action=%s", ad->smack_audit_data->function, sad->result ? "denied" : "granted"); audit_log_format(ab, " subject="); audit_log_untrustedstring(ab, sad->subject); audit_log_format(ab, " object="); audit_log_untrustedstring(ab, sad->object); if (sad->request[0] == '\0') audit_log_format(ab, " labels_differ"); else audit_log_format(ab, " requested=%s", sad->request); } /** * smack_log - Audit the granting or denial of permissions. * @subject_label : smack label of the requester * @object_label : smack label of the object being accessed * @request: requested permissions * @result: result from smk_access * @a: auxiliary audit data * * Audit the granting or denial of permissions in accordance * with the policy. */ void smack_log(char *subject_label, char *object_label, int request, int result, struct smk_audit_info *ad) { #ifdef CONFIG_SECURITY_SMACK_BRINGUP char request_buffer[SMK_NUM_ACCESS_TYPE + 5]; #else char request_buffer[SMK_NUM_ACCESS_TYPE + 1]; #endif struct smack_audit_data *sad; struct common_audit_data *a = &ad->a; /* check if we have to log the current event */ if (result < 0 && (log_policy & SMACK_AUDIT_DENIED) == 0) return; if (result == 0 && (log_policy & SMACK_AUDIT_ACCEPT) == 0) return; sad = a->smack_audit_data; if (sad->function == NULL) sad->function = "unknown"; /* end preparing the audit data */ smack_str_from_perm(request_buffer, request); sad->subject = subject_label; sad->object = object_label; #ifdef CONFIG_SECURITY_SMACK_BRINGUP /* * The result may be positive in bringup mode. * A positive result is an allow, but not for normal reasons. * Mark it as successful, but don't filter it out even if * the logging policy says to do so. */ if (result == SMACK_UNCONFINED_SUBJECT) strcat(request_buffer, "(US)"); else if (result == SMACK_UNCONFINED_OBJECT) strcat(request_buffer, "(UO)"); if (result > 0) result = 0; #endif sad->request = request_buffer; sad->result = result; common_lsm_audit(a, smack_log_callback, NULL); } #else /* #ifdef CONFIG_AUDIT */ void smack_log(char *subject_label, char *object_label, int request, int result, struct smk_audit_info *ad) { } #endif DEFINE_MUTEX(smack_known_lock); struct hlist_head smack_known_hash[SMACK_HASH_SLOTS]; /** * smk_insert_entry - insert a smack label into a hash map, * * this function must be called under smack_known_lock */ void smk_insert_entry(struct smack_known *skp) { unsigned int hash; struct hlist_head *head; hash = full_name_hash(NULL, skp->smk_known, strlen(skp->smk_known)); head = &smack_known_hash[hash & (SMACK_HASH_SLOTS - 1)]; hlist_add_head_rcu(&skp->smk_hashed, head); list_add_rcu(&skp->list, &smack_known_list); } /** * smk_find_entry - find a label on the list, return the list entry * @string: a text string that might be a Smack label * * Returns a pointer to the entry in the label list that * matches the passed string or NULL if not found. */ struct smack_known *smk_find_entry(const char *string) { unsigned int hash; struct hlist_head *head; struct smack_known *skp; hash = full_name_hash(NULL, string, strlen(string)); head = &smack_known_hash[hash & (SMACK_HASH_SLOTS - 1)]; hlist_for_each_entry_rcu(skp, head, smk_hashed) if (strcmp(skp->smk_known, string) == 0) return skp; return NULL; } /** * smk_parse_smack - parse smack label from a text string * @string: a text string that might contain a Smack label * @len: the maximum size, or zero if it is NULL terminated. * * Returns a pointer to the clean label or an error code. */ char *smk_parse_smack(const char *string, int len) { char *smack; int i; if (len <= 0) len = strlen(string) + 1; /* * Reserve a leading '-' as an indicator that * this isn't a label, but an option to interfaces * including /smack/cipso and /smack/cipso2 */ if (string[0] == '-') return ERR_PTR(-EINVAL); for (i = 0; i < len; i++) if (string[i] > '~' || string[i] <= ' ' || string[i] == '/' || string[i] == '"' || string[i] == '\\' || string[i] == '\'') break; if (i == 0 || i >= SMK_LONGLABEL) return ERR_PTR(-EINVAL); smack = kzalloc(i + 1, GFP_KERNEL); if (smack == NULL) return ERR_PTR(-ENOMEM); strncpy(smack, string, i); return smack; } /** * smk_netlbl_mls - convert a catset to netlabel mls categories * @catset: the Smack categories * @sap: where to put the netlabel categories * * Allocates and fills attr.mls * Returns 0 on success, error code on failure. */ int smk_netlbl_mls(int level, char *catset, struct netlbl_lsm_secattr *sap, int len) { unsigned char *cp; unsigned char m; int cat; int rc; int byte; sap->flags |= NETLBL_SECATTR_MLS_CAT; sap->attr.mls.lvl = level; sap->attr.mls.cat = NULL; for (cat = 1, cp = catset, byte = 0; byte < len; cp++, byte++) for (m = 0x80; m != 0; m >>= 1, cat++) { if ((m & *cp) == 0) continue; rc = netlbl_catmap_setbit(&sap->attr.mls.cat, cat, GFP_ATOMIC); if (rc < 0) { netlbl_catmap_free(sap->attr.mls.cat); return rc; } } return 0; } /** * smk_import_entry - import a label, return the list entry * @string: a text string that might be a Smack label * @len: the maximum size, or zero if it is NULL terminated. * * Returns a pointer to the entry in the label list that * matches the passed string, adding it if necessary, * or an error code. */ struct smack_known *smk_import_entry(const char *string, int len) { struct smack_known *skp; char *smack; int slen; int rc; smack = smk_parse_smack(string, len); if (IS_ERR(smack)) return ERR_CAST(smack); mutex_lock(&smack_known_lock); skp = smk_find_entry(smack); if (skp != NULL) goto freeout; skp = kzalloc(sizeof(*skp), GFP_KERNEL); if (skp == NULL) { skp = ERR_PTR(-ENOMEM); goto freeout; } skp->smk_known = smack; skp->smk_secid = smack_next_secid++; skp->smk_netlabel.domain = skp->smk_known; skp->smk_netlabel.flags = NETLBL_SECATTR_DOMAIN | NETLBL_SECATTR_MLS_LVL; /* * If direct labeling works use it. * Otherwise use mapped labeling. */ slen = strlen(smack); if (slen < SMK_CIPSOLEN) rc = smk_netlbl_mls(smack_cipso_direct, skp->smk_known, &skp->smk_netlabel, slen); else rc = smk_netlbl_mls(smack_cipso_mapped, (char *)&skp->smk_secid, &skp->smk_netlabel, sizeof(skp->smk_secid)); if (rc >= 0) { INIT_LIST_HEAD(&skp->smk_rules); mutex_init(&skp->smk_rules_lock); /* * Make sure that the entry is actually * filled before putting it on the list. */ smk_insert_entry(skp); goto unlockout; } /* * smk_netlbl_mls failed. */ kfree(skp); skp = ERR_PTR(rc); freeout: kfree(smack); unlockout: mutex_unlock(&smack_known_lock); return skp; } /** * smack_from_secid - find the Smack label associated with a secid * @secid: an integer that might be associated with a Smack label * * Returns a pointer to the appropriate Smack label entry if there is one, * otherwise a pointer to the invalid Smack label. */ struct smack_known *smack_from_secid(const u32 secid) { struct smack_known *skp; rcu_read_lock(); list_for_each_entry_rcu(skp, &smack_known_list, list) { if (skp->smk_secid == secid) { rcu_read_unlock(); return skp; } } /* * If we got this far someone asked for the translation * of a secid that is not on the list. */ rcu_read_unlock(); return &smack_known_huh; } /* * Unless a process is running with one of these labels * even having CAP_MAC_OVERRIDE isn't enough to grant * privilege to violate MAC policy. If no labels are * designated (the empty list case) capabilities apply to * everyone. */ LIST_HEAD(smack_onlycap_list); DEFINE_MUTEX(smack_onlycap_lock); /* * Is the task privileged and allowed to be privileged * by the onlycap rule. * * Returns 1 if the task is allowed to be privileged, 0 if it's not. */ int smack_privileged(int cap) { struct smack_known *skp = smk_of_current(); struct smack_known_list_elem *sklep; /* * All kernel tasks are privileged */ if (unlikely(current->flags & PF_KTHREAD)) return 1; if (!capable(cap)) return 0; rcu_read_lock(); if (list_empty(&smack_onlycap_list)) { rcu_read_unlock(); return 1; } list_for_each_entry_rcu(sklep, &smack_onlycap_list, list) { if (sklep->smk_label == skp) { rcu_read_unlock(); return 1; } } rcu_read_unlock(); return 0; }