Fix significant security holes with "use chroot = no" in an rsync daemon:

    1. The file paths being sent and received were not "sanitized" to
	ensure that there weren't any ".." components that would escape the
	top level directory.  This can't happen with the standard rsync
	client, but it could be exploited on both read and write if someone
	modified an rsync client.  This fix sanitizes all incoming and
	outgoing paths when "use chroot = no".

    2. If a module is also "read only = no", clients could have created
	symbolic links with ".." components that would allow writing
	outside of the module.  This could happen with the standard rsync
	client.  This fix sanitizes all incoming symbolic link targets
	when "use chroot = no".

Previously, only top-level paths (anything passed in command line arguments)
were sanitized.  Sorry, I didn't think about the individual file paths
before now.

1 files changed, 59 insertions, 31 deletions

diff --git a/util.c b/util.c
index 86ee3f0c..974e8651 100644
--- a/util.c
+++ b/util.c
@@ -477,7 +477,7 @@ int lock_range(int fd, int offset, int len)
 }
 
 
-static void glob_expand_one(char *s, char **argv, int *argc, int maxargs, int sanitize_paths)
+static void glob_expand_one(char *s, char **argv, int *argc, int maxargs)
 {
 #if !(defined(HAVE_GLOB) && defined(HAVE_GLOB_H))
 	if (!*s) s = ".";
@@ -485,14 +485,16 @@ static void glob_expand_one(char *s, char **argv, int *argc, int maxargs, int sa
 	(*argc)++;
 	return;
 #else
+	extern int sanitize_paths;
 	glob_t globbuf;
 	int i;
 
 	if (!*s) s = ".";
 
-	s = strdup(s);
-	sanitize_path(s);
-	argv[*argc] = s;
+	argv[*argc] = strdup(s);
+	if (sanitize_paths) {
+		sanitize_path(argv[*argc], NULL);
+	}
 
 	memset(&globbuf, 0, sizeof(globbuf));
 	glob(argv[*argc], 0, NULL, &globbuf);
@@ -511,7 +513,7 @@ static void glob_expand_one(char *s, char **argv, int *argc, int maxargs, int sa
 #endif
 }
 
-void glob_expand(char *base1, char **argv, int *argc, int maxargs, int sanitize_paths)
+void glob_expand(char *base1, char **argv, int *argc, int maxargs)
 {
 	char *s = argv[*argc];
 	char *p, *q;
@@ -535,11 +537,11 @@ void glob_expand(char *base1, char **argv, int *argc, int maxargs, int sanitize_
 	while ((p = strstr(q,base)) && ((*argc) < maxargs)) {
 		/* split it at this point */
 		*p = 0;
-		glob_expand_one(q, argv, argc, maxargs, sanitize_paths);
+		glob_expand_one(q, argv, argc, maxargs);
 		q = p+strlen(base);
 	}
 
-	if (*q && (*argc < maxargs)) glob_expand_one(q, argv, argc, maxargs, sanitize_paths);
+	if (*q && (*argc < maxargs)) glob_expand_one(q, argv, argc, maxargs);
 
 	free(s);
 	free(base);
@@ -635,8 +637,11 @@ void clean_fname(char *name)
 /*
  * Make path appear as if a chroot had occurred:
  *    1. remove leading "/" (or replace with "." if at end)
- *    2. remove leading ".." components
+ *    2. remove leading ".." components (except those allowed by "reldir")
  *    3. delete any other "<dir>/.." (recursively)
+ * If "reldir" is non-null, it is a sanitized directory that the path will be
+ *    relative to, so allow as many ".." at the beginning of the path as
+ *    there are components in reldir.
  * While we're at it, remove double slashes and "." components like
  *   clean_fname does(), but DON'T remove a trailing slash because that
  *   is sometimes significant on command line arguments.
@@ -644,10 +649,20 @@ void clean_fname(char *name)
  * Contributed by Dave Dykstra <dwd@bell-labs.com>
  */
 
-void sanitize_path(char *p)
+void sanitize_path(char *p, char *reldir)
 {
 	char *start, *sanp;
+	int depth = 0;
+	int allowdotdot = 0;
 
+	if (reldir) {
+		depth++;
+		while (*reldir) {
+			if (*reldir++ == '/') {
+				depth++;
+			}
+		}
+	}
 	start = p;
 	sanp = p;
 	while (*p == '/') {
@@ -665,35 +680,48 @@ void sanitize_path(char *p)
 				/* skip following slashes */
 				;
 			}
-		} else if ((*p == '.') && (*(p+1) == '.') &&
+			continue;
+		}
+		allowdotdot = 0;
+		if ((*p == '.') && (*(p+1) == '.') &&
 			    ((*(p+2) == '/') || (*(p+2) == '\0'))) {
-			/* skip ".." component followed by slash or end */
-			p += 2;
-			if (*p == '/')
-				p++;
-			if (sanp != start) {
-				/* back up sanp one level */
-				--sanp; /* now pointing at slash */
-				while ((sanp > start) && (*(sanp - 1) != '/')) {
-					/* skip back up to slash */
-					sanp--;
+			/* ".." component followed by slash or end */
+			if ((depth > 0) && (sanp == start)) {
+				/* allow depth levels of .. at the beginning */
+				--depth;
+				allowdotdot = 1;
+			} else {
+				p += 2;
+				if (*p == '/')
+					p++;
+				if (sanp != start) {
+					/* back up sanp one level */
+					--sanp; /* now pointing at slash */
+					while ((sanp > start) && (*(sanp - 1) != '/')) {
+						/* skip back up to slash */
+						sanp--;
+					}
 				}
+				continue;
 			}
-		} else {
-			while (1) {
-				/* copy one component through next slash */
-				*sanp++ = *p++;
-				if ((*p == '\0') || (*(p-1) == '/')) {
-					while (*p == '/') {
-						/* skip multiple slashes */
-						p++;
-					}
-					break;
+		}
+		while (1) {
+			/* copy one component through next slash */
+			*sanp++ = *p++;
+			if ((*p == '\0') || (*(p-1) == '/')) {
+				while (*p == '/') {
+					/* skip multiple slashes */
+					p++;
 				}
+				break;
 			}
 		}
+		if (allowdotdot) {
+			/* move the virtual beginning to leave the .. alone */
+			start = sanp;
+		}
 	}
-	if (sanp == start) {
+	if ((sanp == start) && !allowdotdot) {
 		/* ended up with nothing, so put in "." component */
 		*sanp++ = '.';
 	}