apparmor: add first substr match to dfa

Signed-off-by: John Johansen <john.johansen@canonical.com>
Acked-by: Seth Arnold <seth.arnold@canonical.com>

security/apparmor/include/match.h

@@ -129,6 +129,10 @@ unsigned int aa_dfa_match(struct aa_dfa *dfa, unsigned int start,
 			  const char *str);
 unsigned int aa_dfa_next(struct aa_dfa *dfa, unsigned int state,
 			 const char c);
+unsigned int aa_dfa_match_until(struct aa_dfa *dfa, unsigned int start,
+				const char *str, const char **retpos);
+unsigned int aa_dfa_matchn_until(struct aa_dfa *dfa, unsigned int start,
+				 const char *str, int n, const char **retpos);
 
 void aa_dfa_free_kref(struct kref *kref);
 

security/apparmor/match.c

@@ -457,3 +457,123 @@ unsigned int aa_dfa_next(struct aa_dfa *dfa, unsigned int state,
 
 	return state;
 }
+
+/**
+ * aa_dfa_match_until - traverse @dfa until accept state or end of input
+ * @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)
+ * @retpos: first character in str after match OR end of string
+ *
+ * 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.
+ *
+ * Returns: final state reached after input is consumed
+ */
+unsigned int aa_dfa_match_until(struct aa_dfa *dfa, unsigned int start,
+				const char *str, const char **retpos)
+{
+	u16 *def = DEFAULT_TABLE(dfa);
+	u32 *base = BASE_TABLE(dfa);
+	u16 *next = NEXT_TABLE(dfa);
+	u16 *check = CHECK_TABLE(dfa);
+	u32 *accept = ACCEPT_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_idx(base[state]) + equiv[(u8) *str++];
+			if (check[pos] == state)
+				state = next[pos];
+			else
+				state = def[state];
+			if (accept[state])
+				break;
+		}
+	} else {
+		/* default is direct to next state */
+		while (*str) {
+			pos = base_idx(base[state]) + (u8) *str++;
+			if (check[pos] == state)
+				state = next[pos];
+			else
+				state = def[state];
+			if (accept[state])
+				break;
+		}
+	}
+
+	*retpos = str;
+	return state;
+}
+
+
+/**
+ * aa_dfa_matchn_until - traverse @dfa until accept or @n bytes consumed
+ * @dfa: the dfa to match @str against  (NOT NULL)
+ * @start: the state of the dfa to start matching in
+ * @str: the string of bytes to match against the dfa  (NOT NULL)
+ * @n: length of the string of bytes to match
+ * @retpos: first character in str after match OR str + n
+ *
+ * aa_dfa_match_len 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.
+ *
+ * This function will happily match again the 0 byte and only finishes
+ * when @n input is consumed.
+ *
+ * Returns: final state reached after input is consumed
+ */
+unsigned int aa_dfa_matchn_until(struct aa_dfa *dfa, unsigned int start,
+				 const char *str, int n, const char **retpos)
+{
+	u16 *def = DEFAULT_TABLE(dfa);
+	u32 *base = BASE_TABLE(dfa);
+	u16 *next = NEXT_TABLE(dfa);
+	u16 *check = CHECK_TABLE(dfa);
+	u32 *accept = ACCEPT_TABLE(dfa);
+	unsigned int state = start, pos;
+
+	*retpos = NULL;
+	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 */
+		for (; n; n--) {
+			pos = base_idx(base[state]) + equiv[(u8) *str++];
+			if (check[pos] == state)
+				state = next[pos];
+			else
+				state = def[state];
+			if (accept[state])
+				break;
+		}
+	} else {
+		/* default is direct to next state */
+		for (; n; n--) {
+			pos = base_idx(base[state]) + (u8) *str++;
+			if (check[pos] == state)
+				state = next[pos];
+			else
+				state = def[state];
+			if (accept[state])
+				break;
+		}
+	}
+
+	*retpos = str;
+	return state;
+}