/**
* Resolve bindings (if any) in @guest_path and copy the translated
* path into @host_path. Also, this function checks that a non-final
* component is either a directory (returned value is 0) or a symlink
* (returned value is 1), otherwise it returns -errno (-ENOENT or
* -ENOTDIR).
*/
static inline int substitute_binding_stat(Tracee *tracee, Finality finality, unsigned int recursion_level,
const char guest_path[PATH_MAX], char host_path[PATH_MAX])
{
struct stat statl;
int status;
strcpy(host_path, guest_path);
status = substitute_binding(tracee, GUEST, host_path);
if (status < 0)
return status;
/* Don't notify extensions during the initialization of a binding. */
if (tracee->glue_type == 0) {
status = notify_extensions(tracee, HOST_PATH, (intptr_t)host_path,
IS_FINAL(finality) && recursion_level == 0);
if (status < 0)
return status;
}
statl.st_mode = 0;
status = lstat(host_path, &statl);
/* Build the glue between the hostfs and the guestfs during
* the initialization of a binding. */
if (status < 0 && tracee->glue_type != 0) {
statl.st_mode = build_glue(tracee, guest_path, host_path, finality);
if (statl.st_mode == 0)
status = -1;
}
/* Return an error if a non-final component isn't a
* directory nor a symlink. The error is "No such
* file or directory" if this component doesn't exist,
* otherwise the error is "Not a directory". */
if (!IS_FINAL(finality) && !S_ISDIR(statl.st_mode) && !S_ISLNK(statl.st_mode))
return (status < 0 ? -ENOENT : -ENOTDIR);
return (S_ISLNK(statl.st_mode) ? 1 : 0);
}
/**
* Copy in @result the equivalent of "@tracee->root + canon(@dir_fd +
* @user_path)". If @user_path is not absolute then it is relative to
* the directory referred by the descriptor @dir_fd (AT_FDCWD is for
* the current working directory). See the documentation of
* canonicalize() for the meaning of @deref_final. This function
* returns -errno if an error occured, otherwise 0.
*/
int translate_path(Tracee *tracee, char result[PATH_MAX], int dir_fd,
const char *user_path, bool deref_final)
{
char guest_path[PATH_MAX];
int status;
/* Use "/" as the base if it is an absolute guest path. */
if (user_path[0] == '/') {
strcpy(result, "/");
}
/* It is relative to a directory referred by a descriptor, see
* openat(2) for details. */
else if (dir_fd != AT_FDCWD) {
/* /proc/@tracee->pid/fd/@dir_fd -> result. */
status = readlink_proc_pid_fd(tracee->pid, dir_fd, result);
if (status < 0)
return status;
/* Named file descriptors may reference special
* objects like pipes, sockets, inodes, ... Such
* objects do not belong to the file-system. */
if (result[0] != '/')
return -ENOTDIR;
/* Remove the leading "root" part of the base
* (required!). */
status = detranslate_path(tracee, result, NULL);
if (status < 0)
return status;
}
/* It is relative to the current working directory. */
else {
status = getcwd2(tracee, result);
if (status < 0)
return status;
}
VERBOSE(tracee, 2, "pid %d: translate(\"%s\" + \"%s\")",
tracee != NULL ? tracee->pid : 0, result, user_path);
status = notify_extensions(tracee, GUEST_PATH, (intptr_t) result, (intptr_t) user_path);
if (status < 0)
return status;
if (status > 0)
goto skip;
/* So far "result" was used as a base path, it's time to join
* it to the user path. */
assert(result[0] == '/');
status = join_paths(2, guest_path, result, user_path);
if (status < 0)
return status;
strcpy(result, "/");
/* Canonicalize regarding the new root. */
status = canonicalize(tracee, guest_path, deref_final, result, 0);
if (status < 0)
return status;
/* Final binding substitution to convert "result" into a host
* path, since canonicalize() works from the guest
* point-of-view. */
status = substitute_binding(tracee, GUEST, result);
if (status < 0)
return status;
skip:
VERBOSE(tracee, 2, "pid %d: -> \"%s\"",
tracee != NULL ? tracee->pid : 0, result);
return 0;
}
/**
* 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;
}
/**
* Copy in @host_path the equivalent of "@tracee->root +
* canonicalize(@dir_fd + @guest_path)". If @guest_path is not
* absolute then it is relative to the directory referred by the
* descriptor @dir_fd (AT_FDCWD is for the current working directory).
* See the documentation of canonicalize() for the meaning of
* @deref_final. This function returns -errno if an error occured,
* otherwise 0.
*/
int translate_path(Tracee *tracee, char host_path[PATH_MAX],
int dir_fd, const char *guest_path, bool deref_final)
{
int status;
/* Use "/" as the base if it is an absolute guest path. */
if (guest_path[0] == '/') {
strcpy(host_path, "/");
}
/* It is relative to the current working directory or to a
* directory referred by a descriptors, see openat(2) for
* details. */
else if (dir_fd == AT_FDCWD) {
status = getcwd2(tracee, host_path);
if (status < 0)
return status;
}
else {
struct stat statl;
/* /proc/@tracee->pid/fd/@dir_fd -> host_path. */
status = readlink_proc_pid_fd(tracee->pid, dir_fd, host_path);
if (status < 0)
return status;
/* Ensure it points to a directory. */
status = stat(host_path, &statl);
if (status < 0)
return -errno;
if (!S_ISDIR(statl.st_mode))
return -ENOTDIR;
/* Remove the leading "root" part of the base
* (required!). */
status = detranslate_path(tracee, host_path, NULL);
if (status < 0)
return status;
}
VERBOSE(tracee, 2, "pid %d: translate(\"%s\" + \"%s\")",
tracee != NULL ? tracee->pid : 0, host_path, guest_path);
status = notify_extensions(tracee, GUEST_PATH, (intptr_t)host_path, (intptr_t)guest_path);
if (status < 0)
return status;
if (status > 0)
goto skip;
/* Canonicalize regarding the new root. */
status = canonicalize(tracee, guest_path, deref_final, host_path, 0);
if (status < 0)
return status;
/* Final binding substitution to convert "host_path" into a host
* path, since canonicalize() works from the guest
* point-of-view. */
status = substitute_binding(tracee, GUEST, host_path);
if (status < 0)
return status;
skip:
VERBOSE(tracee, 2, "pid %d: -> \"%s\"",
tracee != NULL ? tracee->pid : 0, host_path);
return 0;
}
