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 05f1d462ee71e91475bcfd4afeefcdb18639358a..2eb4cfa1eb1d97ab868e1ad5953398ae5a1036da 100644 (file)
--- a/src/backend/regex/regc_color.c
+++ b/src/backend/regex/regc_color.c
@@ -28,7 +28,7 @@
  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
- * $Header: /cvsroot/pgsql/src/backend/regex/regc_color.c,v 1.3 2003/08/08 21:41:56 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/regex/regc_color.c,v 1.3.4.1 2008/01/03 20:49:15 tgl Exp $
  *
  *
  * Note that there are some incestuous relationships between this code and
@@ -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 18dff7ec34d501ea5c45ff427fc18b7454396958..22878efa5cd75dcb5f78a932f7597cb828954f28 100644 (file)
--- a/src/backend/regex/regc_lex.c
+++ b/src/backend/regex/regc_lex.c
@@ -28,7 +28,7 @@
  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
- * $Header: /cvsroot/pgsql/src/backend/regex/regc_lex.c,v 1.3 2003/08/08 21:41:56 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/regex/regc_lex.c,v 1.3.4.1 2008/01/03 20:49:15 tgl Exp $
  *
  */
 
@@ -849,7 +849,7 @@ 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 51fd8bfb8596e8ffd2d93673487809af067c589c..e6a454fd8e0dda67881e3e8921bfddd717ed9f41 100644 (file)
--- a/src/backend/regex/regc_nfa.c
+++ b/src/backend/regex/regc_nfa.c
@@ -28,7 +28,7 @@
  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
- * $Header: /cvsroot/pgsql/src/backend/regex/regc_nfa.c,v 1.2 2003/08/04 00:43:21 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/regex/regc_nfa.c,v 1.2.4.1 2008/01/03 20:49:15 tgl Exp $
  *
  *
  * One or two things that technically ought to be in here
@@ -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;
 }
 
@@ -221,6 +280,7 @@ freestate(struct nfa * nfa,
        s->next = nfa->free;            /* don't delete it, put it on the free
                                                                 * list */
        nfa->free = s;
+       DecrementSize(nfa);
 }
 
 /*
@@ -634,6 +694,8 @@ 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);
        }
@@ -794,6 +856,25 @@ 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)
        {
@@ -918,6 +999,29 @@ 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)
        {
@@ -1040,7 +1144,8 @@ 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 fbf911fdf2af930ce64d82747dcef94097505fc2..aee85a383c16a65c426fe5e43b022a78a09815f3 100644 (file)
--- a/src/include/regex/regerrs.h
+++ b/src/include/regex/regerrs.h
@@ -1,5 +1,5 @@
 /*
- * $Id: regerrs.h,v 1.2 2003/08/04 00:43:32 momjian Exp $
+ * $Id: regerrs.h,v 1.2.4.1 2008/01/03 20:49:15 tgl Exp $
  */
 
 {
@@ -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 2f8c9946036da93f26eabaaae85d4de40c732b6f..610fab9d18444446e6fcba2a1e597e77ef08de5e 100644 (file)
--- a/src/include/regex/regex.h
+++ b/src/include/regex/regex.h
@@ -29,7 +29,7 @@
  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
- * $Id: regex.h,v 1.25 2003/08/08 21:42:51 momjian Exp $
+ * $Id: regex.h,v 1.25.4.1 2008/01/03 20:49:15 tgl Exp $
  */
 
 /*
@@ -153,6 +153,7 @@ typedef struct
 #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 dfbd392d0929fb02a057c058f7c38c7e2971258a..cff9101a654b07c04037225e2e03722893849833 100644 (file)
--- a/src/include/regex/regguts.h
+++ b/src/include/regex/regguts.h
@@ -27,7 +27,7 @@
  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
- * $Id: regguts.h,v 1.2 2003/08/04 00:43:32 momjian Exp $
+ * $Id: regguts.h,v 1.2.4.1 2008/01/03 20:49:15 tgl Exp $
  */
 
 
@@ -273,6 +273,7 @@ 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
@@ -313,6 +314,9 @@ 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 */
 };
@@ -345,7 +349,12 @@ 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