Fix some regex issues with out-of-range characters and large char ranges.

Previously, our regex code defined CHR_MAX as 0xfffffffe, which is a
bad choice because it is outside the range of type "celt" (int32).
Characters approaching that limit could lead to infinite loops in logic
such as "for (c = a; c <= b; c++)" where c is of type celt but the
range bounds are chr.  Such loops will work safely only if CHR_MAX+1
is representable in celt, since c must advance to beyond b before the
loop will exit.

Fortunately, there seems no reason not to restrict CHR_MAX to 0x7ffffffe.
It's highly unlikely that Unicode will ever assign codes that high, and
none of our other backend encodings need characters beyond that either.

In addition to modifying the macro, we have to explicitly enforce character
range restrictions on the values of \u, \U, and \x escape sequences, else
the limit is trivially bypassed.

Also, the code for expanding case-independent character ranges in bracket
expressions had a potential integer overflow in its calculation of the
number of characters it could generate, which could lead to allocating too
small a character vector and then overwriting memory.  An attacker with the
ability to supply arbitrary regex patterns could easily cause transient DOS
via server crashes, and the possibility for privilege escalation has not
been ruled out.

Quite aside from the integer-overflow problem, the range expansion code was
unnecessarily inefficient in that it always produced a result consisting of
individual characters, abandoning the knowledge that we had a range to
start with.  If the input range is large, this requires excessive memory.
Change it so that the original range is reported as-is, and then we add on
any case-equivalent characters that are outside that range.  With this
approach, we can bound the number of individual characters allowed without
sacrificing much.  This patch allows at most 100000 individual characters,
which I believe to be more than the number of case pairs existing in
Unicode, so that the restriction will never be hit in practice.

It's still possible for range() to take awhile given a large character code
range, so also add statement-cancel detection to its loop.  The downstream
function dovec() also lacked cancel detection, and could take a long time
given a large output from range().

Per fuzz testing by Greg Stark.  Back-patch to all supported branches.

Security: CVE-2016-0773

diff --git a/src/backend/regex/regc_lex.c b/src/backend/regex/regc_lex.c
index bfd9dcd2a492b25142d9f932bf74c00b6324dfc1..962cb230bb75a8e2d7dd56c66c4a9fc7940cd033 100644 (file)
--- a/src/backend/regex/regc_lex.c
+++ b/src/backend/regex/regc_lex.c
@@ -813,13 +813,13 @@ lexescape(struct vars * v)
            break;
        case CHR('u'):
            c = lexdigits(v, 16, 4, 4);
-           if (ISERR())
+           if (ISERR() || c < CHR_MIN || c > CHR_MAX)
                FAILW(REG_EESCAPE);
            RETV(PLAIN, c);
            break;
        case CHR('U'):
            c = lexdigits(v, 16, 8, 8);
-           if (ISERR())
+           if (ISERR() || c < CHR_MIN || c > CHR_MAX)
                FAILW(REG_EESCAPE);
            RETV(PLAIN, c);
            break;
@@ -837,7 +837,7 @@ lexescape(struct vars * v)
        case CHR('x'):
            NOTE(REG_UUNPORT);
            c = lexdigits(v, 16, 1, 255);       /* REs >255 long outside spec */
-           if (ISERR())
+           if (ISERR() || c < CHR_MIN || c > CHR_MAX)
                FAILW(REG_EESCAPE);
            RETV(PLAIN, c);
            break;
@@ -899,6 +899,9 @@ lexescape(struct vars * v)
 
 /*
  * lexdigits - slurp up digits and return chr value
+ *
+ * This does not account for overflow; callers should range-check the result
+ * if maxlen is large enough to make that possible.
  */
 static chr                     /* chr value; errors signalled via ERR */
 lexdigits(struct vars * v,

diff --git a/src/backend/regex/regc_locale.c b/src/backend/regex/regc_locale.c
index e7bbb50ef46680d01b8ac254dccb217495410645..4fe62921e3b438d92d4e7d4d85ff673f8882b74c 100644 (file)
--- a/src/backend/regex/regc_locale.c
+++ b/src/backend/regex/regc_locale.c
@@ -408,8 +408,7 @@ range(struct vars * v,          /* context */
    int         nchrs;
    struct cvec *cv;
    celt        c,
-               lc,
-               uc;
+               cc;
 
    if (a != b && !before(a, b))
    {
@@ -427,24 +426,51 @@ range(struct vars * v,            /* context */
 
    /*
     * When case-independent, it's hard to decide when cvec ranges are usable,
-    * so for now at least, we won't try.  We allocate enough space for two
-    * case variants plus a little extra for the two title case variants.
+    * so for now at least, we won't try.  We use a range for the originally
+    * specified chrs and then add on any case-equivalents that are outside
+    * that range as individual chrs.
+    *
+    * To ensure sane behavior if someone specifies a very large range, limit
+    * the allocation size to 100000 chrs (arbitrary) and check for overrun
+    * inside the loop below.
     */
+   nchrs = b - a + 1;
+   if (nchrs <= 0 || nchrs > 100000)
+       nchrs = 100000;
 
-   nchrs = (b - a + 1) * 2 + 4;
-
-   cv = getcvec(v, nchrs, 0);
+   cv = getcvec(v, nchrs, 1);
    NOERRN();
+   addrange(cv, a, b);
 
    for (c = a; c <= b; c++)
    {
-       addchr(cv, c);
-       lc = pg_wc_tolower((chr) c);
-       if (c != lc)
-           addchr(cv, lc);
-       uc = pg_wc_toupper((chr) c);
-       if (c != uc)
-           addchr(cv, uc);
+       cc = pg_wc_tolower((chr) c);
+       if (cc != c &&
+           (before(cc, a) || before(b, cc)))
+       {
+           if (cv->nchrs >= cv->chrspace)
+           {
+               ERR(REG_ETOOBIG);
+               return NULL;
+           }
+           addchr(cv, cc);
+       }
+       cc = pg_wc_toupper((chr) c);
+       if (cc != c &&
+           (before(cc, a) || before(b, cc)))
+       {
+           if (cv->nchrs >= cv->chrspace)
+           {
+               ERR(REG_ETOOBIG);
+               return NULL;
+           }
+           addchr(cv, cc);
+       }
+       if (CANCEL_REQUESTED(v->re))
+       {
+           ERR(REG_CANCEL);
+           return NULL;
+       }
    }
 
    return cv;

diff --git a/src/backend/regex/regcomp.c b/src/backend/regex/regcomp.c
index a165b3b1ca5676973376c13c0ef84f067b5135ec..cc589b0930101da518ab8e117070d2d71df51a30 100644 (file)
--- a/src/backend/regex/regcomp.c
+++ b/src/backend/regex/regcomp.c
@@ -1593,6 +1593,7 @@ dovec(struct vars * v,
    {
        ch = *p;
        newarc(v->nfa, PLAIN, subcolor(v->cm, ch), lp, rp);
+       NOERR();
    }
 
    /* and the ranges */
@@ -1602,6 +1603,7 @@ dovec(struct vars * v,
        to = *(p + 1);
        if (from <= to)
            subrange(v, from, to, lp, rp);
+       NOERR();
    }
 }
 

diff --git a/src/include/regex/regcustom.h b/src/include/regex/regcustom.h
index dbb461a0ce70fd928953270d2cbfa4c724802e05..3f1d14e19082097833a880d9291a8746562d6548 100644 (file)
--- a/src/include/regex/regcustom.h
+++ b/src/include/regex/regcustom.h
@@ -65,7 +65,8 @@ typedef int celt;             /* type to hold chr, or NOCELT */
 #define DIGITVAL(c) ((c)-'0')  /* turn chr digit into its value */
 #define CHRBITS 32             /* bits in a chr; must not use sizeof */
 #define CHR_MIN 0x00000000     /* smallest and largest chr; the value */
-#define CHR_MAX 0xfffffffe     /* CHR_MAX-CHR_MIN+1 should fit in uchr */
+#define CHR_MAX 0x7ffffffe     /* CHR_MAX-CHR_MIN+1 must fit in an int, and
+                                * CHR_MAX+1 must fit in both chr and celt */
 
 /* functions operating on chr */
 #define iscalnum(x) pg_wc_isalnum(x)

diff --git a/src/test/regress/expected/regex.out b/src/test/regress/expected/regex.out
index 07fb023534fa576e2b1a0357542c5acc5ce36a63..af097193c52dee740033f31db4e8a76b79af8a55 100644 (file)
--- a/src/test/regress/expected/regex.out
+++ b/src/test/regress/expected/regex.out
@@ -495,3 +495,5 @@ select 'xyz' ~ 'x(\w)(?=\1)';  -- no backrefs in LACONs
 ERROR:  invalid regular expression: invalid backreference number
 select 'xyz' ~ 'x(\w)(?=(\1))';
 ERROR:  invalid regular expression: invalid backreference number
+select 'a' ~ '\x7fffffff';  -- invalid chr code
+ERROR:  invalid regular expression: invalid escape \ sequence

diff --git a/src/test/regress/sql/regex.sql b/src/test/regress/sql/regex.sql
index c45bdc91d853419e2fd094adb4a18f9de1ab8e5e..1028ca6dcdcd0e8cae17c13ce4281af678c45708 100644 (file)
--- a/src/test/regress/sql/regex.sql
+++ b/src/test/regress/sql/regex.sql
@@ -121,3 +121,4 @@ select 'a' ~ '()+\1';
 -- Error conditions
 select 'xyz' ~ 'x(\w)(?=\1)';  -- no backrefs in LACONs
 select 'xyz' ~ 'x(\w)(?=(\1))';
+select 'a' ~ '\x7fffffff';  -- invalid chr code