Fix assorted security-grade bugs in the regex engine. All of these problems

are shared with Tcl, since it's their code to begin with, and the patches
have been copied from Tcl 8.5.0.  Problems:

CVE-2007-4769: Inadequate check on the range of backref numbers allows
crash due to out-of-bounds read.
CVE-2007-4772: Infinite loop in regex optimizer for pattern '($|^)*'.
CVE-2007-6067: Very slow optimizer cleanup for regex with a large NFA
representation, as well as crash if we encounter an out-of-memory condition
during NFA construction.

Part of the response to CVE-2007-6067 is to put a limit on the number of
states in the NFA representation of a regex.  This seems needed even though
the within-the-code problems have been corrected, since otherwise the code
could try to use very large amounts of memory for a suitably-crafted regex,
leading to potential DOS by driving the system into swap, activating a kernel
OOM killer, etc.

Although there are certainly plenty of ways to drive the system into effective
DOS with poorly-written SQL queries, these problems seem worth treating as
security issues because many applications might accept regex search patterns
from untrustworthy sources.

Thanks to Will Drewry of Google for reporting these problems.  Patches by Will
Drewry and Tom Lane.

Security: CVE-2007-4769, CVE-2007-4772, CVE-2007-6067

diff --git a/src/backend/regex/regc_color.c b/src/backend/regex/regc_color.c
index 4e5a776ee5f6f9d0726f5e742658dc5589f37a4e..3b5bfa93a46c28cac04bd0fa998658ffe572c95d 100644 (file)
--- a/src/backend/regex/regc_color.c
+++ b/src/backend/regex/regc_color.c
@@ -569,12 +569,9 @@ okcolors(struct nfa * nfa,
                        while ((a = cd->arcs) != NULL)
                        {
                                assert(a->co == co);
-                               /* uncolorchain(cm, a); */
-                               cd->arcs = a->colorchain;
+                               uncolorchain(cm, a);
                                a->co = sco;
-                               /* colorchain(cm, a); */
-                               a->colorchain = scd->arcs;
-                               scd->arcs = a;
+                               colorchain(cm, a);
                        }
                        freecolor(cm, co);
                }
@@ -604,7 +601,10 @@ colorchain(struct colormap * cm,
 {
        struct colordesc *cd = &cm->cd[a->co];
 
+       if (cd->arcs != NULL)
+               cd->arcs->colorchainRev = a;
        a->colorchain = cd->arcs;
+       a->colorchainRev = NULL;
        cd->arcs = a;
 }
 
@@ -616,19 +616,22 @@ uncolorchain(struct colormap * cm,
                         struct arc * a)
 {
        struct colordesc *cd = &cm->cd[a->co];
-       struct arc *aa;
+       struct arc *aa = a->colorchainRev;
 
-       aa = cd->arcs;
-       if (aa == a)                            /* easy case */
+       if (aa == NULL)
+       {
+               assert(cd->arcs == a);
                cd->arcs = a->colorchain;
+       }
        else
        {
-               for (; aa != NULL && aa->colorchain != a; aa = aa->colorchain)
-                       continue;
-               assert(aa != NULL);
+               assert(aa->colorchain == a);
                aa->colorchain = a->colorchain;
        }
+       if (a->colorchain != NULL)
+               a->colorchain->colorchainRev = aa;
        a->colorchain = NULL;           /* paranoia */
+       a->colorchainRev = NULL;
 }
 
 /*

diff --git a/src/backend/regex/regc_lex.c b/src/backend/regex/regc_lex.c
index b65a82c938851645f98f21c160bc997a47b882cb..76cc025a73a080d3ce1e04753a7c4346c37db205 100644 (file)
--- a/src/backend/regex/regc_lex.c
+++ b/src/backend/regex/regc_lex.c
@@ -846,7 +846,7 @@ lexescape(struct vars * v)
                        if (ISERR())
                                FAILW(REG_EESCAPE);
                        /* ugly heuristic (first test is "exactly 1 digit?") */
-                       if (v->now - save == 0 || (int) c <= v->nsubexp)
+                       if (v->now - save == 0 || ((int) c > 0 && (int) c <= v->nsubexp))
                        {
                                NOTE(REG_UBACKREF);
                                RETV(BACKREF, (chr) c);

diff --git a/src/backend/regex/regc_nfa.c b/src/backend/regex/regc_nfa.c
index 9704e5f839b66085dcda05df0d47534a6ba270a6..21798c0642681242e5038edff4586140f386aee2 100644 (file)
--- a/src/backend/regex/regc_nfa.c
+++ b/src/backend/regex/regc_nfa.c
@@ -60,11 +60,12 @@ newnfa(struct vars * v,
        nfa->nstates = 0;
        nfa->cm = cm;
        nfa->v = v;
+       nfa->size = 0;
        nfa->bos[0] = nfa->bos[1] = COLORLESS;
        nfa->eos[0] = nfa->eos[1] = COLORLESS;
+       nfa->parent = parent;           /* Precedes newfstate so parent is valid. */
        nfa->post = newfstate(nfa, '@');        /* number 0 */
        nfa->pre = newfstate(nfa, '>');         /* number 1 */
-       nfa->parent = parent;
 
        nfa->init = newstate(nfa);      /* may become invalid later */
        nfa->final = newstate(nfa);
@@ -88,6 +89,57 @@ newnfa(struct vars * v,
        return nfa;
 }
 
+/*
+ * TooManyStates - checks if the max states exceeds the compile-time value
+ */
+static int
+TooManyStates(struct nfa *nfa)
+{
+       struct nfa *parent = nfa->parent;
+       size_t          sz = nfa->size;
+
+       while (parent != NULL)
+       {
+               sz = parent->size;
+               parent = parent->parent;
+       }
+       if (sz > REG_MAX_STATES)
+               return 1;
+       return 0;
+}
+
+/*
+ * IncrementSize - increases the tracked size of the NFA and its parents.
+ */
+static void
+IncrementSize(struct nfa *nfa)
+{
+       struct nfa *parent = nfa->parent;
+
+       nfa->size++;
+       while (parent != NULL)
+       {
+               parent->size++;
+               parent = parent->parent;
+       }
+}
+
+/*
+ * DecrementSize - decreases the tracked size of the NFA and its parents.
+ */
+static void
+DecrementSize(struct nfa *nfa)
+{
+       struct nfa *parent = nfa->parent;
+
+       nfa->size--;
+       while (parent != NULL)
+       {
+               parent->size--;
+               parent = parent->parent;
+       }
+}
+
 /*
  * freenfa - free an entire NFA
  */
@@ -122,6 +174,11 @@ newstate(struct nfa * nfa)
 {
        struct state *s;
 
+       if (TooManyStates(nfa))
+       {
+               NERR(REG_ETOOBIG);
+               return NULL;
+       }
        if (nfa->free != NULL)
        {
                s = nfa->free;
@@ -158,6 +215,8 @@ newstate(struct nfa * nfa)
        }
        s->prev = nfa->slast;
        nfa->slast = s;
+       /* track the current size and the parent size */
+       IncrementSize(nfa);
        return s;
 }
 
@@ -220,6 +279,7 @@ freestate(struct nfa * nfa,
        s->prev = NULL;
        s->next = nfa->free;            /* don't delete it, put it on the free list */
        nfa->free = s;
+       DecrementSize(nfa);
 }
 
 /*
@@ -633,6 +693,8 @@ duptraverse(struct nfa * nfa,
        for (a = s->outs; a != NULL && !NISERR(); a = a->outchain)
        {
                duptraverse(nfa, a->to, (struct state *) NULL);
+               if (NISERR())
+                       break;
                assert(a->to->tmp != NULL);
                cparc(nfa, a, s->tmp, a->to->tmp);
        }
@@ -793,6 +855,25 @@ pull(struct nfa * nfa,
                return 1;
        }
 
+       /*
+        * DGP 2007-11-15: Cloning a state with a circular constraint on its list
+        * of outs can lead to trouble [Tcl Bug 1810038], so get rid of them first.
+        */
+       for (a = from->outs; a != NULL; a = nexta)
+       {
+               nexta = a->outchain;
+               switch (a->type)
+               {
+                       case '^':
+                       case '$':
+                       case BEHIND:
+                       case AHEAD:
+                               if (from == a->to)
+                                       freearc(nfa, a);
+                               break;
+               }
+       }
+
        /* first, clone from state if necessary to avoid other outarcs */
        if (from->nouts > 1)
        {
@@ -917,6 +998,29 @@ push(struct nfa * nfa,
                return 1;
        }
 
+       /*
+        * DGP 2007-11-15: Here we duplicate the same protections as appear
+        * in pull() above to avoid troubles with cloning a state with a
+        * circular constraint on its list of ins.  It is not clear whether
+        * this is necessary, or is protecting against a "can't happen".
+        * Any test case that actually leads to a freearc() call here would
+        * be a welcome addition to the test suite.
+        */
+       for (a = to->ins; a != NULL; a = nexta)
+       {
+               nexta = a->inchain;
+               switch (a->type)
+               {
+                       case '^':
+                       case '$':
+                       case BEHIND:
+                       case AHEAD:
+                               if (a->from == to)
+                                       freearc(nfa, a);
+                               break;
+               }
+       }
+
        /* first, clone to state if necessary to avoid other inarcs */
        if (to->nins > 1)
        {
@@ -1039,7 +1143,8 @@ fixempties(struct nfa * nfa,
        do
        {
                progress = 0;
-               for (s = nfa->states; s != NULL && !NISERR(); s = nexts)
+               for (s = nfa->states; s != NULL && !NISERR() &&
+                                s->no != FREESTATE; s = nexts)
                {
                        nexts = s->next;
                        for (a = s->outs; a != NULL && !NISERR(); a = nexta)

diff --git a/src/include/regex/regerrs.h b/src/include/regex/regerrs.h
index aeec9878a47e0bb6ecef664fef8406635db42feb..75c8909bbd0a432b8166cc79d9718f6153267c91 100644 (file)
--- a/src/include/regex/regerrs.h
+++ b/src/include/regex/regerrs.h
@@ -73,3 +73,7 @@
 {
        REG_BADOPT, "REG_BADOPT", "invalid embedded option"
 },
+
+{
+       REG_ETOOBIG, "REG_ETOOBIG", "nfa has too many states"
+},

diff --git a/src/include/regex/regex.h b/src/include/regex/regex.h
index 7cb26dfe634ae6b840c0622cb54c18f8cca380a0..524d2cba113e611ed8756bf417265d80441f9949 100644 (file)
--- a/src/include/regex/regex.h
+++ b/src/include/regex/regex.h
@@ -151,6 +151,7 @@ typedef struct
 #define REG_INVARG     16                      /* invalid argument to regex function */
 #define REG_MIXED      17                      /* character widths of regex and string differ */
 #define REG_BADOPT     18                      /* invalid embedded option */
+#define REG_ETOOBIG    19                      /* nfa has too many states */
 /* two specials for debugging and testing */
 #define REG_ATOI       101                     /* convert error-code name to number */
 #define REG_ITOA       102                     /* convert error-code number to name */

diff --git a/src/include/regex/regguts.h b/src/include/regex/regguts.h
index 2238a3d99a1f3519fdf6896166d479acd00eea41..d71f942e4a5ec694b7cff04b3c70a4f909c65b4d 100644 (file)
--- a/src/include/regex/regguts.h
+++ b/src/include/regex/regguts.h
@@ -272,6 +272,7 @@ struct arc
 #define  freechain      outchain
        struct arc *inchain;            /* *to's ins chain */
        struct arc *colorchain;         /* color's arc chain */
+       struct arc *colorchainRev;      /* back-link in color's arc chain */
 };
 
 struct arcbatch
@@ -311,6 +312,9 @@ struct nfa
        struct colormap *cm;            /* the color map */
        color           bos[2];                 /* colors, if any, assigned to BOS and BOL */
        color           eos[2];                 /* colors, if any, assigned to EOS and EOL */
+       size_t          size;                   /* Current NFA size; differs from nstates as
+                                                                * it also counts the number of states created
+                                                                * by children of this state. */
        struct vars *v;                         /* simplifies compile error reporting */
        struct nfa *parent;                     /* parent NFA, if any */
 };
@@ -343,7 +347,12 @@ struct cnfa
 #define ZAPCNFA(cnfa)  ((cnfa).nstates = 0)
 #define NULLCNFA(cnfa) ((cnfa).nstates == 0)
 
-
+/*
+ * Used to limit the maximum NFA size to something sane. [Tcl Bug 1810264]
+ */
+#ifndef REG_MAX_STATES
+#define REG_MAX_STATES 100000
+#endif
 
 /*
  * subexpression tree