5:05 p.m.
Hi Steve,
Thanks for reviewing.
On Tue, Jan 03, 2006 at 03:46:42PM -0500, Steve Grubb wrote:
On Wednesday 21 December 2005 19:08, Amy Griffis wrote:
Thanks Amy for sending this. We at least have the beginnings of the new file
system audit patch to chew on. :) I only have a couple issues listed below.
They basically revolve around length checking of the netlink packet.
> ????????case AUDIT_ADD:
> ????????case AUDIT_DEL:
> -???????????????if (nlh->nlmsg_len < sizeof(struct audit_rule))
> +???????????????if (nlmsg_len(nlh) < sizeof(struct audit_rule))
This checks the lower size bound, is there a check for the upper bound? Or
that the strings after buf[0] are in fact correctly sized? Does all the
lengths + struct add up to be equal to the payload length?
These message types use struct audit_rule, which doesn't support an
additional buffer.
> ????????????????????????return -EINVAL;
> ????????????????/* fallthrough */
> ????????case AUDIT_LIST:
> ????????????????err = audit_receive_filter(nlh->nlmsg_type,
> NETLINK_CB(skb).pid, -??????????????????????????????????????? ? uid, seq,
> data, loginuid); +??????????????????????????????????????? ? uid, seq, data,
> nlmsg_len(nlh), +??????????????????????????????????????? ? loginuid);
> +???????????????break;
> +???????case AUDIT_ADD_RULE:
> +???????case AUDIT_DEL_RULE:
> +???????????????if (nlmsg_len(nlh) < sizeof(struct audit_rule_xprt))
Same.
The netlink packet length is passed along through
audit_receive_filter() to audit_xprt_to_entry(), where it can be
referenced while processing the buffer. audit_xprt_to_entry() keeps
track of the bytes in the buffer yet to be consumed and provides this
value to audit_unpack_string(), which both checks that sufficient
space remains, and updates the 'remaining' value accordingly. I see
audit_unpack_string() as being called by this patch's consumers in the
per-field-type switch statement in audit_xprt_to_entry().
> +???????????????????????return -EINVAL;
> +???????????????/* fallthrough */
> +???????case AUDIT_LIST_RULES:
> +???????????????err = audit_receive_filter(nlh->nlmsg_type,
> NETLINK_CB(skb).pid, +??????????????????????????????????????? ? uid, seq,
> data, nlmsg_len(nlh), +??????????????????????????????????????? ? loginuid);
> ????????????????break;
> ????????case AUDIT_SIGNAL_INFO:
> ????????????????sig_data.uid = audit_sig_uid;
> right); diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
> index a3a3275..1fd4b2a 100644
> --- a/kernel/auditfilter.c
> +++ b/kernel/auditfilter.c
> @@ -40,52 +40,253 @@ struct list_head audit_filter_list[AUDIT
> ?#endif
> ?};
> ?
> -/* Copy rule from user-space to kernel-space. ?Called from
> - * audit_add_rule during AUDIT_ADD. */
> -static inline int audit_copy_rule(struct audit_rule *d, struct audit_rule
> *s) +/* Unpack a filter field's string representation from user-space
> + * buffer. */
> +static inline char *audit_unpack_string(void **bufp, int *remaining, int
> len) {
I couldn't find callers for this.
Correct. I intended for this to be called by consumers from the
switch in audit_xprt_to_entry(). I clearly didn't provide enough
comments. :-/
Is there any chance that len or remaining could be negative? If not,
lets make them unsigned.
I'll do that, thanks.
> +???????char *str;
> +
> +???????if (!*bufp || (len > *remaining))
> +???????????????return ERR_PTR(-EINVAL);
len should always be <= PATH_MAX*2. That must be checked for as well or there
could be wrapping.
I'm confused about the significance of the value PATH_MAX*2 and how
that relates here. Could you clarify?
> +/* Common user-space to kernel rule translation. */
> +static struct audit_entry *audit_to_entry_common(struct audit_rule *rule)
> +{
> +???????unsigned listnr;
> +???????struct audit_entry *entry;
> +???????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 < 0 || rule->field_count >
AUDIT_MAX_FIELDS)
> +???????????????goto exit_err;
field_count is u32 & cannot be less than 0. It should be checked to make sure
its not 0, though.
I thought it was okay to specify a rule with no fields, i.e.
auditctl -a entry,always -S swapon
> +
> +???????err = -ENOMEM;
> +???????entry = kmalloc(sizeof(*entry), GFP_KERNEL);
> +???????if (!entry)
> +???????????????goto exit_err;
> +???????memset(&entry->rule, 0, sizeof(struct audit_krule));
> +
> +???????entry->rule.flags = rule->flags & AUDIT_FILTER_PREPEND;
> +???????entry->rule.listnr = listnr;
> +???????entry->rule.action = rule->action;
> +???????entry->rule.field_count = rule->field_count;
> +
> +???????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;
> ?
> -???????if (s->action != AUDIT_NEVER
> -??????? ? ?&& s->action != AUDIT_POSSIBLE
> -??????? ? ?&& s->action != AUDIT_ALWAYS)
> -???????????????return -1;
> -???????if (s->field_count < 0 || s->field_count > AUDIT_MAX_FIELDS)
> -???????????????return -1;
Same as above. sb == 0 rather than < 0.
I'm not sure what you mean. I don't see a variable 'sb' and this is
code that was removed.
> -???????if ((s->flags & ~AUDIT_FILTER_PREPEND) >= AUDIT_NR_FILTERS)
> -???????????????return -1;
> -
> -???????d->flags????????= s->flags;
> -???????d->action???????= s->action;
> -???????d->field_count??= s->field_count;
> -???????for (i = 0; i < d->field_count; i++) {
> -???????????????d->fields[i] = s->fields[i];
> -???????????????d->values[i] = s->values[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;
> +???????????????if (f->op & AUDIT_NEGATE)
> +???????????????????????f->op |= AUDIT_NOT_EQUAL;
> +???????????????else if (!(f->op & AUDIT_OPERATORS))
> +???????????????????????f->op |= AUDIT_EQUAL;
> +???????????????f->op &= ~AUDIT_NEGATE;
> ????????}
> -???????for (i = 0; i < AUDIT_BITMASK_SIZE; i++) d->mask[i] = s->mask[i];
> -???????return 0;
> +
> +exit_nofree:
> +???????return entry;
> +
> +exit_free:
> +???????kfree(entry);
> +???????return ERR_PTR(err);
> ?}
> ?
> -/* Check to see if two rules are identical. ?It is called from
> - * audit_add_rule during AUDIT_ADD and
> - * audit_del_rule during AUDIT_DEL. */
> -static int audit_compare_rule(struct audit_rule *a, struct audit_rule *b)
> +/* Translate struct audit_rule_xprt to kernel's rule respresentation. */
> +static struct audit_entry *audit_xprt_to_entry(struct audit_rule_xprt
> *xprt, +??????????????????????????????????????? ? ? ? int dlen)
> ?{
> +???????int err = 0;
> +???????struct audit_entry *entry;
> +???????void *bufp;
> +???????/* int remaining = dlen - sizeof(struct audit_rule_xprt); */
> ????????int i;
> ?
> -???????if (a->flags != b->flags)
> -???????????????return 1;
> +???????entry = audit_to_entry_common((struct audit_rule *)xprt);
> +???????if (IS_ERR(entry))
> +???????????????goto exit_nofree;
> +
> +???????bufp = xprt->buf;
What uses bufp?
Nothing right now, but it should be used by a consumer adding code to
the switch statement.
> +/* Pack a filter field's string representation into data block. */
> +static inline int audit_pack_string(void **bufp, char *str)
What calls this?
This should be called by a consumer from the switch in
audit_krule_to_xprt().
> +{
> +???????int len = strlen(str);
Why use int? size_t is natural size.
Sure, will fix.
> +???????memcpy(*bufp, str, len);
> +???????*bufp += len;
> +
> +???????return len;
> +}
> +
-Steve