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Subject[PATCH 3/7] AppArmor: Update dfa matching routines.
Date
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>
---
security/apparmor/include/apparmor.h | 2 +-
security/apparmor/include/match.h | 3 +
security/apparmor/match.c | 80 ++++++++++++++++++++++++++++++++-
3 files changed, 81 insertions(+), 4 deletions(-)

diff --git a/security/apparmor/include/apparmor.h b/security/apparmor/include/apparmor.h
index df36495..248c408 100644
--- a/security/apparmor/include/apparmor.h
+++ b/security/apparmor/include/apparmor.h
@@ -81,7 +81,7 @@ static inline unsigned int aa_dfa_null_transition(struct aa_dfa *dfa,
unsigned int start)
{
/* the null transition only needs the string's null terminator byte */
- return aa_dfa_match_len(dfa, start, "", 1);
+ return aa_dfa_next(dfa, start, 0);
}

static inline bool mediated_filesystem(struct inode *inode)
diff --git a/security/apparmor/include/match.h b/security/apparmor/include/match.h
index a4a8639..775843e 100644
--- a/security/apparmor/include/match.h
+++ b/security/apparmor/include/match.h
@@ -116,6 +116,9 @@ unsigned int aa_dfa_match_len(struct aa_dfa *dfa, unsigned int start,
const char *str, int len);
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);
+
void aa_dfa_free_kref(struct kref *kref);

/**
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 @@ unsigned int aa_dfa_match_len(struct aa_dfa *dfa, unsigned int start,
}

/**
- * 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_len(struct aa_dfa *dfa, unsigned int start,
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;
}
--
1.7.9


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