AppArmor: Update dfa matching routines.
Update aa_dfa_match so that it doesn't result in an input string being
walked twice (once to get its length and another time to match)
Add a single step functions
aa_dfa_next
Signed-off-by: John Johansen <john.johansen@canonical.com>
Acked-by: Kees Cook <kees@ubuntu.com>
diff --git a/security/apparmor/match.c b/security/apparmor/match.c
index 94de6b4..90971a8 100644
--- a/security/apparmor/match.c
+++ b/security/apparmor/match.c
@@ -335,12 +335,12 @@
}
/**
- * aa_dfa_next_state - traverse @dfa to find state @str stops at
+ * aa_dfa_match - traverse @dfa to find state @str stops at
* @dfa: the dfa to match @str against (NOT NULL)
* @start: the state of the dfa to start matching in
* @str: the null terminated string of bytes to match against the dfa (NOT NULL)
*
- * aa_dfa_next_state will match @str against the dfa and return the state it
+ * aa_dfa_match will match @str against the dfa and return the state it
* finished matching in. The final state can be used to look up the accepting
* label, or as the start state of a continuing match.
*
@@ -349,5 +349,79 @@
unsigned int aa_dfa_match(struct aa_dfa *dfa, unsigned int start,
const char *str)
{
- return aa_dfa_match_len(dfa, start, str, strlen(str));
+ u16 *def = DEFAULT_TABLE(dfa);
+ u32 *base = BASE_TABLE(dfa);
+ u16 *next = NEXT_TABLE(dfa);
+ u16 *check = CHECK_TABLE(dfa);
+ unsigned int state = start, pos;
+
+ if (state == 0)
+ return 0;
+
+ /* current state is <state>, matching character *str */
+ if (dfa->tables[YYTD_ID_EC]) {
+ /* Equivalence class table defined */
+ u8 *equiv = EQUIV_TABLE(dfa);
+ /* default is direct to next state */
+ while (*str) {
+ pos = base[state] + equiv[(u8) *str++];
+ if (check[pos] == state)
+ state = next[pos];
+ else
+ state = def[state];
+ }
+ } else {
+ /* default is direct to next state */
+ while (*str) {
+ pos = base[state] + (u8) *str++;
+ if (check[pos] == state)
+ state = next[pos];
+ else
+ state = def[state];
+ }
+ }
+
+ return state;
+}
+
+/**
+ * aa_dfa_next - step one character to the next state in the dfa
+ * @dfa: the dfa to tranverse (NOT NULL)
+ * @state: the state to start in
+ * @c: the input character to transition on
+ *
+ * aa_dfa_match will step through the dfa by one input character @c
+ *
+ * Returns: state reach after input @c
+ */
+unsigned int aa_dfa_next(struct aa_dfa *dfa, unsigned int state,
+ const char c)
+{
+ u16 *def = DEFAULT_TABLE(dfa);
+ u32 *base = BASE_TABLE(dfa);
+ u16 *next = NEXT_TABLE(dfa);
+ u16 *check = CHECK_TABLE(dfa);
+ unsigned int pos;
+
+ /* current state is <state>, matching character *str */
+ if (dfa->tables[YYTD_ID_EC]) {
+ /* Equivalence class table defined */
+ u8 *equiv = EQUIV_TABLE(dfa);
+ /* default is direct to next state */
+
+ pos = base[state] + equiv[(u8) c];
+ if (check[pos] == state)
+ state = next[pos];
+ else
+ state = def[state];
+ } else {
+ /* default is direct to next state */
+ pos = base[state] + (u8) c;
+ if (check[pos] == state)
+ state = next[pos];
+ else
+ state = def[state];
+ }
+
+ return state;
}