diff options
Diffstat (limited to 'kernel/auditfilter.c')
| -rw-r--r-- | kernel/auditfilter.c | 630 |
1 files changed, 630 insertions, 0 deletions
diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c new file mode 100644 index 00000000000..d3a8539f3a8 --- /dev/null +++ b/kernel/auditfilter.c @@ -0,0 +1,630 @@ +/* auditfilter.c -- filtering of audit events + * + * Copyright 2003-2004 Red Hat, Inc. + * Copyright 2005 Hewlett-Packard Development Company, L.P. + * Copyright 2005 IBM Corporation + * + * 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; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + */ + +#include <linux/kernel.h> +#include <linux/audit.h> +#include <linux/kthread.h> +#include <linux/netlink.h> +#include "audit.h" + +/* There are three lists of rules -- one to search at task creation + * time, one to search at syscall entry time, and another to search at + * syscall exit time. */ +struct list_head audit_filter_list[AUDIT_NR_FILTERS] = { + LIST_HEAD_INIT(audit_filter_list[0]), + LIST_HEAD_INIT(audit_filter_list[1]), + LIST_HEAD_INIT(audit_filter_list[2]), + LIST_HEAD_INIT(audit_filter_list[3]), + LIST_HEAD_INIT(audit_filter_list[4]), + LIST_HEAD_INIT(audit_filter_list[5]), +#if AUDIT_NR_FILTERS != 6 +#error Fix audit_filter_list initialiser +#endif +}; + +static inline void audit_free_rule(struct audit_entry *e) +{ + kfree(e->rule.fields); + kfree(e); +} + +static inline void audit_free_rule_rcu(struct rcu_head *head) +{ + struct audit_entry *e = container_of(head, struct audit_entry, rcu); + audit_free_rule(e); +} + +/* Unpack a filter field's string representation from user-space + * buffer. */ +static __attribute__((unused)) char *audit_unpack_string(void **bufp, size_t *remain, size_t len) +{ + char *str; + + if (!*bufp || (len == 0) || (len > *remain)) + return ERR_PTR(-EINVAL); + + /* Of the currently implemented string fields, PATH_MAX + * defines the longest valid length. + */ + if (len > PATH_MAX) + return ERR_PTR(-ENAMETOOLONG); + + str = kmalloc(len + 1, GFP_KERNEL); + if (unlikely(!str)) + return ERR_PTR(-ENOMEM); + + memcpy(str, *bufp, len); + str[len] = 0; + *bufp += len; + *remain -= len; + + return str; +} + +/* Common user-space to kernel rule translation. */ +static inline struct audit_entry *audit_to_entry_common(struct audit_rule *rule) +{ + unsigned listnr; + struct audit_entry *entry; + struct audit_field *fields; + int i, err; + + err = -EINVAL; + listnr = rule->flags & ~AUDIT_FILTER_PREPEND; + switch(listnr) { + default: + goto exit_err; + case AUDIT_FILTER_USER: + case AUDIT_FILTER_TYPE: +#ifdef CONFIG_AUDITSYSCALL + case AUDIT_FILTER_ENTRY: + case AUDIT_FILTER_EXIT: + case AUDIT_FILTER_TASK: +#endif + ; + } + if (rule->action != AUDIT_NEVER && rule->action != AUDIT_POSSIBLE && + rule->action != AUDIT_ALWAYS) + goto exit_err; + if (rule->field_count > AUDIT_MAX_FIELDS) + goto exit_err; + + err = -ENOMEM; + entry = kmalloc(sizeof(*entry), GFP_KERNEL); + if (unlikely(!entry)) + goto exit_err; + fields = kmalloc(sizeof(*fields) * rule->field_count, GFP_KERNEL); + if (unlikely(!fields)) { + kfree(entry); + goto exit_err; + } + + memset(&entry->rule, 0, sizeof(struct audit_krule)); + memset(fields, 0, sizeof(struct audit_field)); + + entry->rule.flags = rule->flags & AUDIT_FILTER_PREPEND; + entry->rule.listnr = listnr; + entry->rule.action = rule->action; + entry->rule.field_count = rule->field_count; + entry->rule.fields = fields; + + for (i = 0; i < AUDIT_BITMASK_SIZE; i++) + entry->rule.mask[i] = rule->mask[i]; + + return entry; + +exit_err: + return ERR_PTR(err); +} + +/* Translate struct audit_rule to kernel's rule respresentation. + * Exists for backward compatibility with userspace. */ +static struct audit_entry *audit_rule_to_entry(struct audit_rule *rule) +{ + struct audit_entry *entry; + int err = 0; + int i; + + entry = audit_to_entry_common(rule); + if (IS_ERR(entry)) + goto exit_nofree; + + for (i = 0; i < rule->field_count; i++) { + struct audit_field *f = &entry->rule.fields[i]; + + if (rule->fields[i] & AUDIT_UNUSED_BITS) { + err = -EINVAL; + goto exit_free; + } + + f->op = rule->fields[i] & (AUDIT_NEGATE|AUDIT_OPERATORS); + f->type = rule->fields[i] & ~(AUDIT_NEGATE|AUDIT_OPERATORS); + f->val = rule->values[i]; + + entry->rule.vers_ops = (f->op & AUDIT_OPERATORS) ? 2 : 1; + + /* Support for legacy operators where + * AUDIT_NEGATE bit signifies != and otherwise assumes == */ + if (f->op & AUDIT_NEGATE) + f->op = AUDIT_NOT_EQUAL; + else if (!f->op) + f->op = AUDIT_EQUAL; + else if (f->op == AUDIT_OPERATORS) { + err = -EINVAL; + goto exit_free; + } + } + +exit_nofree: + return entry; + +exit_free: + audit_free_rule(entry); + return ERR_PTR(err); +} + +/* Translate struct audit_rule_data to kernel's rule respresentation. */ +static struct audit_entry *audit_data_to_entry(struct audit_rule_data *data, + size_t datasz) +{ + int err = 0; + struct audit_entry *entry; + void *bufp; + /* size_t remain = datasz - sizeof(struct audit_rule_data); */ + int i; + + entry = audit_to_entry_common((struct audit_rule *)data); + if (IS_ERR(entry)) + goto exit_nofree; + + bufp = data->buf; + entry->rule.vers_ops = 2; + for (i = 0; i < data->field_count; i++) { + struct audit_field *f = &entry->rule.fields[i]; + + err = -EINVAL; + if (!(data->fieldflags[i] & AUDIT_OPERATORS) || + data->fieldflags[i] & ~AUDIT_OPERATORS) + goto exit_free; + + f->op = data->fieldflags[i] & AUDIT_OPERATORS; + f->type = data->fields[i]; + switch(f->type) { + /* call type-specific conversion routines here */ + default: + f->val = data->values[i]; + } + } + +exit_nofree: + return entry; + +exit_free: + audit_free_rule(entry); + return ERR_PTR(err); +} + +/* Pack a filter field's string representation into data block. */ +static inline size_t audit_pack_string(void **bufp, char *str) +{ + size_t len = strlen(str); + + memcpy(*bufp, str, len); + *bufp += len; + + return len; +} + +/* Translate kernel rule respresentation to struct audit_rule. + * Exists for backward compatibility with userspace. */ +static struct audit_rule *audit_krule_to_rule(struct audit_krule *krule) +{ + struct audit_rule *rule; + int i; + + rule = kmalloc(sizeof(*rule), GFP_KERNEL); + if (unlikely(!rule)) + return ERR_PTR(-ENOMEM); + memset(rule, 0, sizeof(*rule)); + + rule->flags = krule->flags | krule->listnr; + rule->action = krule->action; + rule->field_count = krule->field_count; + for (i = 0; i < rule->field_count; i++) { + rule->values[i] = krule->fields[i].val; + rule->fields[i] = krule->fields[i].type; + + if (krule->vers_ops == 1) { + if (krule->fields[i].op & AUDIT_NOT_EQUAL) + rule->fields[i] |= AUDIT_NEGATE; + } else { + rule->fields[i] |= krule->fields[i].op; + } + } + for (i = 0; i < AUDIT_BITMASK_SIZE; i++) rule->mask[i] = krule->mask[i]; + + return rule; +} + +/* Translate kernel rule respresentation to struct audit_rule_data. */ +static struct audit_rule_data *audit_krule_to_data(struct audit_krule *krule) +{ + struct audit_rule_data *data; + void *bufp; + int i; + + data = kmalloc(sizeof(*data) + krule->buflen, GFP_KERNEL); + if (unlikely(!data)) + return ERR_PTR(-ENOMEM); + memset(data, 0, sizeof(*data)); + + data->flags = krule->flags | krule->listnr; + data->action = krule->action; + data->field_count = krule->field_count; + bufp = data->buf; + for (i = 0; i < data->field_count; i++) { + struct audit_field *f = &krule->fields[i]; + + data->fields[i] = f->type; + data->fieldflags[i] = f->op; + switch(f->type) { + /* call type-specific conversion routines here */ + default: + data->values[i] = f->val; + } + } + for (i = 0; i < AUDIT_BITMASK_SIZE; i++) data->mask[i] = krule->mask[i]; + + return data; +} + +/* Compare two rules in kernel format. Considered success if rules + * don't match. */ +static int audit_compare_rule(struct audit_krule *a, struct audit_krule *b) +{ + int i; + + if (a->flags != b->flags || + a->listnr != b->listnr || + a->action != b->action || + a->field_count != b->field_count) + return 1; + + for (i = 0; i < a->field_count; i++) { + if (a->fields[i].type != b->fields[i].type || + a->fields[i].op != b->fields[i].op) + return 1; + + switch(a->fields[i].type) { + /* call type-specific comparison routines here */ + default: + if (a->fields[i].val != b->fields[i].val) + return 1; + } + } + + for (i = 0; i < AUDIT_BITMASK_SIZE; i++) + if (a->mask[i] != b->mask[i]) + return 1; + + return 0; +} + +/* Add rule to given filterlist if not a duplicate. Protected by + * audit_netlink_mutex. */ +static inline int audit_add_rule(struct audit_entry *entry, + struct list_head *list) +{ + struct audit_entry *e; + + /* Do not use the _rcu iterator here, since this is the only + * addition routine. */ + list_for_each_entry(e, list, list) { + if (!audit_compare_rule(&entry->rule, &e->rule)) + return -EEXIST; + } + + if (entry->rule.flags & AUDIT_FILTER_PREPEND) { + list_add_rcu(&entry->list, list); + } else { + list_add_tail_rcu(&entry->list, list); + } + + return 0; +} + +/* Remove an existing rule from filterlist. Protected by + * audit_netlink_mutex. */ +static inline int audit_del_rule(struct audit_entry *entry, + struct list_head *list) +{ + struct audit_entry *e; + + /* Do not use the _rcu iterator here, since this is the only + * deletion routine. */ + list_for_each_entry(e, list, list) { + if (!audit_compare_rule(&entry->rule, &e->rule)) { + list_del_rcu(&e->list); + call_rcu(&e->rcu, audit_free_rule_rcu); + return 0; + } + } + return -ENOENT; /* No matching rule */ +} + +/* List rules using struct audit_rule. Exists for backward + * compatibility with userspace. */ +static int audit_list(void *_dest) +{ + int pid, seq; + int *dest = _dest; + struct audit_entry *entry; + int i; + + pid = dest[0]; + seq = dest[1]; + kfree(dest); + + mutex_lock(&audit_netlink_mutex); + + /* The *_rcu iterators not needed here because we are + always called with audit_netlink_mutex held. */ + for (i=0; i<AUDIT_NR_FILTERS; i++) { + list_for_each_entry(entry, &audit_filter_list[i], list) { + struct audit_rule *rule; + + rule = audit_krule_to_rule(&entry->rule); + if (unlikely(!rule)) + break; + audit_send_reply(pid, seq, AUDIT_LIST, 0, 1, + rule, sizeof(*rule)); + kfree(rule); + } + } + audit_send_reply(pid, seq, AUDIT_LIST, 1, 1, NULL, 0); + + mutex_unlock(&audit_netlink_mutex); + return 0; +} + +/* List rules using struct audit_rule_data. */ +static int audit_list_rules(void *_dest) +{ + int pid, seq; + int *dest = _dest; + struct audit_entry *e; + int i; + + pid = dest[0]; + seq = dest[1]; + kfree(dest); + + mutex_lock(&audit_netlink_mutex); + + /* The *_rcu iterators not needed here because we are + always called with audit_netlink_mutex held. */ + for (i=0; i<AUDIT_NR_FILTERS; i++) { + list_for_each_entry(e, &audit_filter_list[i], list) { + struct audit_rule_data *data; + + data = audit_krule_to_data(&e->rule); + if (unlikely(!data)) + break; + audit_send_reply(pid, seq, AUDIT_LIST_RULES, 0, 1, + data, sizeof(*data)); + kfree(data); + } + } + audit_send_reply(pid, seq, AUDIT_LIST_RULES, 1, 1, NULL, 0); + + mutex_unlock(&audit_netlink_mutex); + return 0; +} + +/** + * audit_receive_filter - apply all rules to the specified message type + * @type: audit message type + * @pid: target pid for netlink audit messages + * @uid: target uid for netlink audit messages + * @seq: netlink audit message sequence (serial) number + * @data: payload data + * @datasz: size of payload data + * @loginuid: loginuid of sender + */ +int audit_receive_filter(int type, int pid, int uid, int seq, void *data, + size_t datasz, uid_t loginuid) +{ + struct task_struct *tsk; + int *dest; + int err = 0; + struct audit_entry *entry; + + switch (type) { + case AUDIT_LIST: + case AUDIT_LIST_RULES: + /* We can't just spew out the rules here because we might fill + * the available socket buffer space and deadlock waiting for + * auditctl to read from it... which isn't ever going to + * happen if we're actually running in the context of auditctl + * trying to _send_ the stuff */ + + dest = kmalloc(2 * sizeof(int), GFP_KERNEL); + if (!dest) + return -ENOMEM; + dest[0] = pid; + dest[1] = seq; + + if (type == AUDIT_LIST) + tsk = kthread_run(audit_list, dest, "audit_list"); + else + tsk = kthread_run(audit_list_rules, dest, + "audit_list_rules"); + if (IS_ERR(tsk)) { + kfree(dest); + err = PTR_ERR(tsk); + } + break; + case AUDIT_ADD: + case AUDIT_ADD_RULE: + if (type == AUDIT_ADD) + entry = audit_rule_to_entry(data); + else + entry = audit_data_to_entry(data, datasz); + if (IS_ERR(entry)) + return PTR_ERR(entry); + + err = audit_add_rule(entry, + &audit_filter_list[entry->rule.listnr]); + audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE, + "auid=%u add rule to list=%d res=%d\n", + loginuid, entry->rule.listnr, !err); + + if (err) + audit_free_rule(entry); + break; + case AUDIT_DEL: + case AUDIT_DEL_RULE: + if (type == AUDIT_DEL) + entry = audit_rule_to_entry(data); + else + entry = audit_data_to_entry(data, datasz); + if (IS_ERR(entry)) + return PTR_ERR(entry); + + err = audit_del_rule(entry, + &audit_filter_list[entry->rule.listnr]); + audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE, + "auid=%u remove rule from list=%d res=%d\n", + loginuid, entry->rule.listnr, !err); + + audit_free_rule(entry); + break; + default: + return -EINVAL; + } + + return err; +} + +int audit_comparator(const u32 left, const u32 op, const u32 right) +{ + switch (op) { + case AUDIT_EQUAL: + return (left == right); + case AUDIT_NOT_EQUAL: + return (left != right); + case AUDIT_LESS_THAN: + return (left < right); + case AUDIT_LESS_THAN_OR_EQUAL: + return (left <= right); + case AUDIT_GREATER_THAN: + return (left > right); + case AUDIT_GREATER_THAN_OR_EQUAL: + return (left >= right); + } + BUG(); + return 0; +} + + + +static int audit_filter_user_rules(struct netlink_skb_parms *cb, + struct audit_krule *rule, + enum audit_state *state) +{ + int i; + + for (i = 0; i < rule->field_count; i++) { + struct audit_field *f = &rule->fields[i]; + int result = 0; + + switch (f->type) { + case AUDIT_PID: + result = audit_comparator(cb->creds.pid, f->op, f->val); + break; + case AUDIT_UID: + result = audit_comparator(cb->creds.uid, f->op, f->val); + break; + case AUDIT_GID: + result = audit_comparator(cb->creds.gid, f->op, f->val); + break; + case AUDIT_LOGINUID: + result = audit_comparator(cb->loginuid, f->op, f->val); + break; + } + + if (!result) + return 0; + } + switch (rule->action) { + case AUDIT_NEVER: *state = AUDIT_DISABLED; break; + case AUDIT_POSSIBLE: *state = AUDIT_BUILD_CONTEXT; break; + case AUDIT_ALWAYS: *state = AUDIT_RECORD_CONTEXT; break; + } + return 1; +} + +int audit_filter_user(struct netlink_skb_parms *cb, int type) +{ + struct audit_entry *e; + enum audit_state state; + int ret = 1; + + rcu_read_lock(); + list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_USER], list) { + if (audit_filter_user_rules(cb, &e->rule, &state)) { + if (state == AUDIT_DISABLED) + ret = 0; + break; + } + } + rcu_read_unlock(); + + return ret; /* Audit by default */ +} + +int audit_filter_type(int type) +{ + struct audit_entry *e; + int result = 0; + + rcu_read_lock(); + if (list_empty(&audit_filter_list[AUDIT_FILTER_TYPE])) + goto unlock_and_return; + + list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_TYPE], + list) { + int i; + for (i = 0; i < e->rule.field_count; i++) { + struct audit_field *f = &e->rule.fields[i]; + if (f->type == AUDIT_MSGTYPE) { + result = audit_comparator(type, f->op, f->val); + if (!result) + break; + } + } + if (result) + goto unlock_and_return; + } +unlock_and_return: + rcu_read_unlock(); + return result; +} |