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AppArmor: Update dfa matching routines.

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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>
This commit is contained in:
John Johansen 2012-02-16 06:20:26 -08:00
parent 3372b68a3c
commit 0fe1212d05
3 changed files with 81 additions and 4 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
security/apparmor/include/apparmor.h
View file

@ -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)

3
security/apparmor/include/match.h
View file

@ -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);
/**

80
security/apparmor/match.c
View file

@ -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;
}