Protect against DoS attacks, such as being described in CVE-2010-2632.

The changes were derived from what has been committed to NetBSD, with
modifications. These are:
1.  Preserve the existsing GLOB_LIMIT behaviour by including the number
    of matches to the set of parameters to limit.
2.  Change some of the limits to avoid impacting normal use cases:
    GLOB_LIMIT_STRING - change from 65536 to ARG_MAX so that glob(3)
	can still provide a full command line of expanded names.
    GLOB_LIMIT_STAT - change from 128 to 1024 for no other reason than
	that 128 feels too low (it's not a limit that impacts the
	behaviour of the test program listed in CVE-2010-2632).
    GLOB_LIMIT_PATH - change from 1024 to 65536 so that glob(3) can
	still provide a fill command line of expanded names.
3.  Protect against buffer overruns when we hit the GLOB_LIMIT_STAT or
    GLOB_LIMIT_READDIR limits. We append SEP and EOS to pathend in
    those cases. Return GLOB_ABORTED instead of GLOB_NOSPACE when we
    would otherwise overrun the buffer.

This change also modifies the existing behaviour of glob(3) in case
GLOB_LIMIT is specifies by limiting the *new* matches and not all
matches. This is an important distinction when GLOB_APPEND is set or
when the caller uses a non-zero gl_offs. Previously pre-existing
matches or the value of gl_offs would be counted in the number of
matches even though the man page states that glob(3) would return
GLOB_NOSPACE when gl_matchc or more matches were found.

The limits that cannot be circumvented are GLOB_LIMIT_STRING and
GLOB_LIMIT_PATH all others can be crossed by simply calling glob(3)
again and with GLOB_APPEND set.

The entire description above applies only when GLOB_LIMIT has been
specified of course. No limits apply when this flag isn't set!

Obtained from: Juniper Networks, Inc

1 files changed, 79 insertions, 22 deletions

diff --git a/lib/libc/gen/glob.c b/lib/libc/gen/glob.c
index 3c5020c..832dc8d 100644
--- a/lib/libc/gen/glob.c
+++ b/lib/libc/gen/glob.c
@@ -94,6 +94,25 @@ __FBSDID("$FreeBSD$");
 
 #include "collate.h"
 
+/*
+ * glob(3) expansion limits. Stop the expansion if any of these limits
+ * is reached. This caps the runtime in the face of DoS attacks. See
+ * also CVE-2010-2632
+ */
+#define	GLOB_LIMIT_BRACE	128	/* number of brace calls */
+#define	GLOB_LIMIT_PATH		65536	/* number of path elements */
+#define	GLOB_LIMIT_READDIR	16384	/* number of readdirs */
+#define	GLOB_LIMIT_STAT		1024	/* number of stat system calls */
+#define	GLOB_LIMIT_STRING	ARG_MAX	/* maximum total size for paths */
+
+struct glob_limit {
+	size_t	l_brace_cnt;
+	size_t	l_path_lim;
+	size_t	l_readdir_cnt;	
+	size_t	l_stat_cnt;	
+	size_t	l_string_cnt;
+};
+
 #define	DOLLAR		'$'
 #define	DOT		'.'
 #define	EOS		'\0'
@@ -153,15 +172,18 @@ static const Char *g_strchr(const Char *, wchar_t);
 static Char	*g_strcat(Char *, const Char *);
 #endif
 static int	 g_stat(Char *, struct stat *, glob_t *);
-static int	 glob0(const Char *, glob_t *, size_t *);
-static int	 glob1(Char *, glob_t *, size_t *);
-static int	 glob2(Char *, Char *, Char *, Char *, glob_t *, size_t *);
-static int	 glob3(Char *, Char *, Char *, Char *, Char *, glob_t *, size_t *);
-static int	 globextend(const Char *, glob_t *, size_t *);
-static const Char *	
+static int	 glob0(const Char *, glob_t *, struct glob_limit *);
+static int	 glob1(Char *, glob_t *, struct glob_limit *);
+static int	 glob2(Char *, Char *, Char *, Char *, glob_t *,
+    struct glob_limit *);
+static int	 glob3(Char *, Char *, Char *, Char *, Char *, glob_t *,
+    struct glob_limit *);
+static int	 globextend(const Char *, glob_t *, struct glob_limit *);
+static const Char *
 		 globtilde(const Char *, Char *, size_t, glob_t *);
-static int	 globexp1(const Char *, glob_t *, size_t *);
-static int	 globexp2(const Char *, const Char *, glob_t *, int *, size_t *);
+static int	 globexp1(const Char *, glob_t *, struct glob_limit *);
+static int	 globexp2(const Char *, const Char *, glob_t *, int *,
+    struct glob_limit *);
 static int	 match(Char *, Char *, Char *);
 #ifdef DEBUG
 static void	 qprintf(const char *, Char *);
@@ -171,8 +193,8 @@ int
 glob(const char * __restrict pattern, int flags,
 	 int (*errfunc)(const char *, int), glob_t * __restrict pglob)
 {
+	struct glob_limit limit = { 0, 0, 0, 0, 0 };
 	const char *patnext;
-	size_t limit;
 	Char *bufnext, *bufend, patbuf[MAXPATHLEN], prot;
 	mbstate_t mbs;
 	wchar_t wc;
@@ -186,11 +208,10 @@ glob(const char * __restrict pattern, int flags,
 			pglob->gl_offs = 0;
 	}
 	if (flags & GLOB_LIMIT) {
-		limit = pglob->gl_matchc;
-		if (limit == 0)
-			limit = ARG_MAX;
-	} else
-		limit = 0;
+		limit.l_path_lim = pglob->gl_matchc;
+		if (limit.l_path_lim == 0)
+			limit.l_path_lim = GLOB_LIMIT_PATH;
+	}
 	pglob->gl_flags = flags & ~GLOB_MAGCHAR;
 	pglob->gl_errfunc = errfunc;
 	pglob->gl_matchc = 0;
@@ -243,11 +264,17 @@ glob(const char * __restrict pattern, int flags,
  * characters
  */
 static int
-globexp1(const Char *pattern, glob_t *pglob, size_t *limit)
+globexp1(const Char *pattern, glob_t *pglob, struct glob_limit *limit)
 {
 	const Char* ptr = pattern;
 	int rv;
 
+	if ((pglob->gl_flags & GLOB_LIMIT) &&
+	    limit->l_brace_cnt++ >= GLOB_LIMIT_BRACE) {
+		errno = 0;
+		return (GLOB_NOSPACE);
+	}
+
 	/* Protect a single {}, for find(1), like csh */
 	if (pattern[0] == LBRACE && pattern[1] == RBRACE && pattern[2] == EOS)
 		return glob0(pattern, pglob, limit);
@@ -266,7 +293,8 @@ globexp1(const Char *pattern, glob_t *pglob, size_t *limit)
  * If it fails then it tries to glob the rest of the pattern and returns.
  */
 static int
-globexp2(const Char *ptr, const Char *pattern, glob_t *pglob, int *rv, size_t *limit)
+globexp2(const Char *ptr, const Char *pattern, glob_t *pglob, int *rv,
+    struct glob_limit *limit)
 {
 	int     i;
 	Char   *lm, *ls;
@@ -436,7 +464,7 @@ globtilde(const Char *pattern, Char *patbuf, size_t patbuf_len, glob_t *pglob)
  * if things went well, nonzero if errors occurred.
  */
 static int
-glob0(const Char *pattern, glob_t *pglob, size_t *limit)
+glob0(const Char *pattern, glob_t *pglob, struct glob_limit *limit)
 {
 	const Char *qpatnext;
 	int err;
@@ -529,7 +557,7 @@ compare(const void *p, const void *q)
 }
 
 static int
-glob1(Char *pattern, glob_t *pglob, size_t *limit)
+glob1(Char *pattern, glob_t *pglob, struct glob_limit *limit)
 {
 	Char pathbuf[MAXPATHLEN];
 
@@ -547,7 +575,7 @@ glob1(Char *pattern, glob_t *pglob, size_t *limit)
  */
 static int
 glob2(Char *pathbuf, Char *pathend, Char *pathend_last, Char *pattern,
-      glob_t *pglob, size_t *limit)
+      glob_t *pglob, struct glob_limit *limit)
 {
 	struct stat sb;
 	Char *p, *q;
@@ -563,6 +591,15 @@ glob2(Char *pathbuf, Char *pathend, Char *pathend_last, Char *pattern,
 			if (g_lstat(pathbuf, &sb, pglob))
 				return (0);
 
+			if ((pglob->gl_flags & GLOB_LIMIT) &&
+			    limit->l_stat_cnt++ >= GLOB_LIMIT_STAT) {
+				errno = 0;
+				if (pathend + 1 > pathend_last)
+					return (GLOB_ABORTED);
+				*pathend++ = SEP;
+				*pathend = EOS;
+				return (GLOB_NOSPACE);
+			}
 			if (((pglob->gl_flags & GLOB_MARK) &&
 			    pathend[-1] != SEP) && (S_ISDIR(sb.st_mode)
 			    || (S_ISLNK(sb.st_mode) &&
@@ -606,7 +643,7 @@ glob2(Char *pathbuf, Char *pathend, Char *pathend_last, Char *pattern,
 static int
 glob3(Char *pathbuf, Char *pathend, Char *pathend_last,
       Char *pattern, Char *restpattern,
-      glob_t *pglob, size_t *limit)
+      glob_t *pglob, struct glob_limit *limit)
 {
 	struct dirent *dp;
 	DIR *dirp;
@@ -652,6 +689,19 @@ glob3(Char *pathbuf, Char *pathend, Char *pathend_last,
 		size_t clen;
 		mbstate_t mbs;
 
+		if ((pglob->gl_flags & GLOB_LIMIT) &&
+		    limit->l_readdir_cnt++ >= GLOB_LIMIT_READDIR) {
+			errno = 0;
+			if (pathend + 1 > pathend_last)
+				err = GLOB_ABORTED;
+			else {
+				*pathend++ = SEP;
+				*pathend = EOS;
+				err = GLOB_NOSPACE;
+			}
+			break;
+		}
+
 		/* Initial DOT must be matched literally. */
 		if (dp->d_name[0] == DOT && *pattern != DOT)
 			continue;
@@ -702,14 +752,15 @@ glob3(Char *pathbuf, Char *pathend, Char *pathend_last,
  *	gl_pathv points to (gl_offs + gl_pathc + 1) items.
  */
 static int
-globextend(const Char *path, glob_t *pglob, size_t *limit)
+globextend(const Char *path, glob_t *pglob, struct glob_limit *limit)
 {
 	char **pathv;
 	size_t i, newsize, len;
 	char *copy;
 	const Char *p;
 
-	if (*limit && pglob->gl_pathc > *limit) {
+	if ((pglob->gl_flags & GLOB_LIMIT) &&
+	    pglob->gl_matchc > limit->l_path_lim) {
 		errno = 0;
 		return (GLOB_NOSPACE);
 	}
@@ -731,6 +782,12 @@ globextend(const Char *path, glob_t *pglob, size_t *limit)
 	for (p = path; *p++;)
 		continue;
 	len = MB_CUR_MAX * (size_t)(p - path);	/* XXX overallocation */
+	limit->l_string_cnt += len;
+	if ((pglob->gl_flags & GLOB_LIMIT) &&
+	    limit->l_string_cnt >= GLOB_LIMIT_STRING) {
+		errno = 0;
+		return (GLOB_NOSPACE);
+	}
 	if ((copy = malloc(len)) != NULL) {
 		if (g_Ctoc(path, copy, len)) {
 			free(copy);