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match time limit defined by variable 'string.pattlimit'

This commit is contained in:
Roberto Ierusalimschy 2016-04-19 09:34:08 -03:00
parent 48baa5e89c
commit 89c09c8e40
1 changed files with 36 additions and 16 deletions
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52
lstrlib.c
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@ -1,5 +1,5 @@
/*
** $Id: lstrlib.c,v 1.244 2016/04/07 15:40:07 roberto Exp roberto $
** $Id: lstrlib.c,v 1.245 2016/04/08 21:15:02 roberto Exp roberto $
** Standard library for string operations and pattern-matching
** See Copyright Notice in lua.h
*/
@ -26,7 +26,8 @@
/*
** maximum number of captures that a pattern can do during
** pattern-matching. This limit is arbitrary.
** pattern-matching. This limit is arbitrary, but must fit in
** an unsigned char.
*/
#if !defined(LUA_MAXCAPTURES)
#define LUA_MAXCAPTURES 32
@ -214,9 +215,10 @@ typedef struct MatchState {
const char *src_end; /* end ('\0') of source string */
const char *p_end; /* end ('\0') of pattern */
lua_State *L;
size_t nrep; /* limit to avoid non-linear complexity */
lua_Unsigned nrep; /* limit to avoid non-linear complexity */
int matchdepth; /* control for recursive depth (to avoid C stack overflow) */
int level; /* total number of captures (finished or unfinished) */
unsigned char level; /* total number of captures (finished or unfinished) */
unsigned char usedlimit; /* true if real limit for 'nrep' was used */
struct {
const char *init;
ptrdiff_t len;
@ -235,13 +237,12 @@ static const char *match (MatchState *ms, const char *s, const char *p);
/*
** parameters to control the maximum number of operators handled in
** a match (to avoid non-linear complexity). The maximum will be:
** (subject length) * A_REPS + B_REPS
** Maximum number of operators handled in a match before consulting
** 'string.pattlimit'. (This lower limit is only to avoid wasting time
** consulting 'string.pattlimit' in simple matches.)
*/
#if !defined(A_REPS)
#define A_REPS 4
#define B_REPS 100000
#if !defined(PREPATTLIMIT)
#define PREPATTLIMIT 200
#endif
@ -421,6 +422,27 @@ static const char *end_capture (MatchState *ms, const char *s,
}
static void checklimit (MatchState *ms) {
lua_State *L = ms->L;
lua_assert(ms->nrep == 0);
if (!ms->usedlimit) { /* have not used 'string.pattlimit' yet? */
int top = lua_gettop(L);
if (lua_getglobal(L, "string") == LUA_TTABLE &&
lua_getfield(L, -1, "pattlimit") != LUA_TNIL) { /* is it defined? */
lua_Unsigned limit = (lua_Unsigned)lua_tointeger(L, -1); /* get it */
if (limit > PREPATTLIMIT) /* discount cycles already used */
ms->nrep = limit - PREPATTLIMIT;
ms->usedlimit = 1; /* do not use 'pattlimit' again */
}
else /* no limit defined; set no limit */
ms->nrep = ~(lua_Unsigned)0;
lua_settop(L, top); /* pop 'string' table and (maybe) 'pattlimit' */
}
if (ms->nrep == 0)
luaL_error(L, "pattern too complex");
}
static const char *match_capture (MatchState *ms, const char *s, int l) {
size_t len;
l = check_capture(ms, l);
@ -502,8 +524,8 @@ static const char *match (MatchState *ms, const char *s, const char *p) {
s = NULL; /* fail */
}
else { /* matched once */
if (ms->nrep-- == 0)
luaL_error(ms->L, "pattern too complex");
if (--ms->nrep == 0)
checklimit(ms);
switch (*ep) { /* handle optional suffix */
case '?': { /* optional */
const char *res;
@ -607,10 +629,8 @@ static void prepstate (MatchState *ms, lua_State *L,
ms->src_init = s;
ms->src_end = s + ls;
ms->p_end = p + lp;
if (ls < (MAX_SIZET - B_REPS) / A_REPS)
ms->nrep = A_REPS * ls + B_REPS;
else /* overflow (very long subject) */
ms->nrep = MAX_SIZET; /* no limit */
ms->nrep = PREPATTLIMIT;
ms->usedlimit = 0;
}