/**
* Get the binding for the given @path (relatively to the given
* binding @side).
*/
static const Binding *get_binding(Tracee *tracee, Side side, const char path[PATH_MAX])
{
const Binding *binding;
size_t path_length = strlen(path);
/* Sanity checks. */
assert(path != NULL && path[0] == '/');
CIRCLEQ_FOREACH_(tracee, binding, side) {
Comparison comparison;
const Path *ref;
switch (side) {
case GUEST:
ref = &binding->guest;
break;
case HOST:
ref = &binding->host;
break;
default:
assert(0);
return NULL;
}
comparison = compare_paths2(ref->path, ref->length, path, path_length);
if ( comparison != PATHS_ARE_EQUAL
&& comparison != PATH1_IS_PREFIX)
continue;
/* Avoid false positive when a prefix of the rootfs is
* used as an asymmetric binding, ex.:
*
* proot -m /usr:/location /usr/local/slackware
*/
if ( side == HOST
&& compare_paths(get_root(tracee), "/") != PATHS_ARE_EQUAL
&& belongs_to_guestfs(tracee, path))
continue;
return binding;
}
/**
* Remove/substitute the leading part of a "translated" @path. It
* returns 0 if no transformation is required (ie. symmetric binding),
* otherwise it returns the size in bytes of the updated @path,
* including the end-of-string terminator. On error it returns
* -errno.
*/
int detranslate_path(Tracee *tracee, char path[PATH_MAX], const char t_referrer[PATH_MAX])
{
size_t prefix_length;
ssize_t new_length;
bool sanity_check;
bool follow_binding;
/* Sanity check. */
if (strnlen(path, PATH_MAX) >= PATH_MAX)
return -ENAMETOOLONG;
/* Don't try to detranslate relative paths (typically the
* target of a relative symbolic link). */
if (path[0] != '/')
return 0;
/* Is it a symlink? */
if (t_referrer != NULL) {
Comparison comparison;
sanity_check = false;
follow_binding = false;
/* In some cases bindings have to be resolved. */
comparison = compare_paths("/proc", t_referrer);
if (comparison == PATH1_IS_PREFIX) {
/* Some links in "/proc" are generated
* dynamically by the kernel. PRoot has to
* emulate some of them. */
char proc_path[PATH_MAX];
strcpy(proc_path, path);
new_length = readlink_proc2(tracee, proc_path, t_referrer);
if (new_length < 0)
return new_length;
if (new_length != 0) {
strcpy(path, proc_path);
return new_length + 1;
}
/* Always resolve bindings for symlinks in
* "/proc", they always point to the emulated
* file-system namespace by design. */
follow_binding = true;
}
else if (!belongs_to_guestfs(tracee, t_referrer)) {
const char *binding_referree;
const char *binding_referrer;
binding_referree = get_path_binding(tracee, HOST, path);
binding_referrer = get_path_binding(tracee, HOST, t_referrer);
assert(binding_referrer != NULL);
/* Resolve bindings for symlinks that belong
* to a binding and point to the same binding.
* For example, if "-b /lib:/foo" is specified
* and the symlink "/lib/a -> /lib/b" exists
* in the host rootfs namespace, then it
* should appear as "/foo/a -> /foo/b" in the
* guest rootfs namespace for consistency
* reasons. */
if (binding_referree != NULL) {
comparison = compare_paths(binding_referree, binding_referrer);
follow_binding = (comparison == PATHS_ARE_EQUAL);
}
}
}
else {
sanity_check = true;
follow_binding = true;
}
if (follow_binding) {
switch (substitute_binding(tracee, HOST, path)) {
case 0:
return 0;
case 1:
return strlen(path) + 1;
default:
break;
}
}
switch (compare_paths(get_root(tracee), path)) {
case PATH1_IS_PREFIX:
/* Remove the leading part, that is, the "root". */
prefix_length = strlen(get_root(tracee));
/* Special case when path to the guest rootfs == "/". */
if (prefix_length == 1)
prefix_length = 0;
new_length = strlen(path) - prefix_length;
memmove(path, path + prefix_length, new_length);
path[new_length] = '\0';
break;
case PATHS_ARE_EQUAL:
/* Special case when path == root. */
new_length = 1;
strcpy(path, "/");
break;
default:
/* Ensure the path is within the new root. */
if (sanity_check)
return -EPERM;
else
return 0;
}
return new_length + 1;
}
