main: Allow escaped colons in directory paths

Allow directory paths specified for lowerdir, upperdir and workdir to
contain colon characters.

Previously, colons were unconditionally treated as separators,
making it impossible to use directories with colons in their names.

Closes: https://github.com/containers/fuse-overlayfs/issues/440

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

main.c

@@ -1924,6 +1924,58 @@ cleanup_layerp (struct ovl_layer **p)
 
 #define cleanup_layer __attribute__ ((cleanup (cleanup_layerp)))
 
+static void
+unescape (char *input)
+{
+  char *dest = input;
+
+  if (input == NULL)
+    return;
+
+  for (; *input; input++)
+    {
+      if (*input == '\\')
+        continue;
+
+      *dest++ = *input;
+    }
+  *dest = '\0';
+}
+
+static char *
+get_next_path (char *it, char **saveptr)
+{
+  char *ret;
+
+  if (*saveptr == NULL)
+    *saveptr = it;
+
+  ret = *saveptr;
+
+  if (*ret == '\0')
+    return NULL;
+
+  while (1)
+    {
+      if (**saveptr == '\0')
+        break;
+
+      if (**saveptr == ':')
+        {
+          **saveptr = '\0';
+          (*saveptr)++;
+          break;
+        }
+      else if (**saveptr == '\\')
+        {
+          memmove (*saveptr, *saveptr + 1, strlen (*saveptr) + 1);
+        }
+
+      (*saveptr)++;
+    }
+  return ret;
+}
+
 static struct ovl_layer *
 read_dirs (struct ovl_data *lo, char *path, bool low, struct ovl_layer *layers)
 {
@@ -1942,7 +1994,7 @@ read_dirs (struct ovl_data *lo, char *path, bool low, struct ovl_layer *layers)
   while (last && last->next)
     last = last->next;
 
-  for (it = strtok_r (buf, ":", &saveptr); it; it = strtok_r (NULL, ":", &saveptr))
+  for (it = get_next_path (buf, &saveptr); it; it = get_next_path (NULL, &saveptr))
     {
       char *name, *data;
       char *it_path = it;
@@ -5755,6 +5807,7 @@ main (int argc, char *argv[])
   if (lo.mountpoint == NULL)
     error (EXIT_FAILURE, 0, "no mountpoint specified");
 
+  unescape (lo.workdir);
 
   set_limits ();
   check_can_mknod (&lo);

tests/fedora-installs.sh

@@ -2,17 +2,17 @@
 
 set -xeuo pipefail
 
-mkdir lower upper workdir merged
+mkdir lower:1 upper:2 workdir:3 merged
 
-fuse-overlayfs -o sync=0,lowerdir=lower,upperdir=upper,workdir=workdir,suid,dev merged
+fuse-overlayfs -o 'sync=0,lowerdir=lower\\:1,upperdir=upper\\:2,workdir=workdir\\:3,suid,dev' merged
 
 docker run --rm -v $(pwd)/merged:/merged fedora dnf --use-host-config --installroot /merged --releasever 41 install -y glibc-common gedit
 
 umount merged
 
 # Make sure workdir is empty, and move the upper layer down
-rm -rf workdir lower
-mv upper lower
+rm -rf lower:1 workdir:3
+mv upper:2 lower
 mkdir upper workdir
 
 gcc -static -o suid-test $(dirname $0)/suid-test.c