static bool next_component_filter(struct bootloader_hdr *bootl_hdr,
struct component_hdr **c_hdr, unsigned sz,
const char* filter)
{
printf("Looking for %s\n", filter);
while (next_component(bootl_hdr, c_hdr, sz))
if (!strncmp((*c_hdr)->magic, filter, strlen(filter)) &&
(*c_hdr)->flags & FLAG_FLASH)
return true;
return false;
}
/**
* Copy in @guest_path the canonicalization (see `man 3 realpath`) of
* @user_path regarding to @tracee->root. The path to canonicalize
* could be either absolute or relative to @guest_path. When the last
* component of @user_path is a link, it is dereferenced only if
* @deref_final is true -- it is useful for syscalls like lstat(2).
* The parameter @recursion_level should be set to 0 unless you know
* what you are doing. This function returns -errno if an error
* occured, otherwise it returns 0.
*/
int canonicalize(Tracee *tracee, const char *user_path, bool deref_final,
char guest_path[PATH_MAX], unsigned int recursion_level)
{
char scratch_path[PATH_MAX];
Finality finality;
const char *cursor;
int status;
/* Avoid infinite loop on circular links. */
if (recursion_level > MAXSYMLINKS)
return -ELOOP;
/* Sanity checks. */
assert(user_path != NULL);
assert(guest_path != NULL);
assert(user_path != guest_path);
if (strnlen(guest_path, PATH_MAX) >= PATH_MAX)
return -ENAMETOOLONG;
if (user_path[0] != '/') {
/* Ensure 'guest_path' contains an absolute base of
* the relative `user_path`. */
if (guest_path[0] != '/')
return -EINVAL;
}
else
strcpy(guest_path, "/");
/* Canonicalize recursely 'user_path' into 'guest_path'. */
cursor = user_path;
finality = NOT_FINAL;
while (!IS_FINAL(finality)) {
Comparison comparison;
char component[NAME_MAX];
char host_path[PATH_MAX];
finality = next_component(component, &cursor);
status = (int) finality;
if (status < 0)
return status;
if (strcmp(component, ".") == 0) {
if (IS_FINAL(finality))
finality = FINAL_DOT;
continue;
}
if (strcmp(component, "..") == 0) {
pop_component(guest_path);
if (IS_FINAL(finality))
finality = FINAL_SLASH;
continue;
}
status = join_paths(2, scratch_path, guest_path, component);
if (status < 0)
return status;
/* Resolve bindings and check that a non-final
* component exists and either is a directory or is a
* symlink. For this latter case, we check that the
* symlink points to a directory once it is
* canonicalized, at the end of this loop. */
status = substitute_binding_stat(tracee, finality, recursion_level, scratch_path, host_path);
if (status < 0)
return status;
/* Nothing special to do if it's not a link or if we
* explicitly ask to not dereference 'user_path', as
* required by syscalls like lstat(2). Obviously, this
* later condition does not apply to intermediate path
* components. Errors are explicitly ignored since
* they should be handled by the caller. */
if (status <= 0 || (finality == FINAL_NORMAL && !deref_final)) {
strcpy(scratch_path, guest_path);
status = join_paths(2, guest_path, scratch_path, component);
if (status < 0)
return status;
continue;
}
/* It's a link, so we have to dereference *and*
* canonicalize to ensure we are not going outside the
* new root. */
comparison = compare_paths("/proc", guest_path);
switch (comparison) {
case PATHS_ARE_EQUAL:
case PATH1_IS_PREFIX:
/* Some links in "/proc" are generated
* dynamically by the kernel. PRoot has to
* emulate some of them. */
status = readlink_proc(tracee, scratch_path,
guest_path, component, comparison);
switch (status) {
case CANONICALIZE:
/* The symlink is already dereferenced,
* now canonicalize it. */
goto canon;
case DONT_CANONICALIZE:
/* If and only very final, this symlink
* shouldn't be dereferenced nor canonicalized. */
if (finality == FINAL_NORMAL) {
strcpy(guest_path, scratch_path);
return 0;
}
break;
default:
if (status < 0)
return status;
}
default:
break;
}
status = readlink(host_path, scratch_path, sizeof(scratch_path));
if (status < 0)
return status;
else if (status == sizeof(scratch_path))
return -ENAMETOOLONG;
scratch_path[status] = '\0';
/* Remove the leading "root" part if needed, it's
* useful for "/proc/self/cwd/" for instance. */
status = detranslate_path(tracee, scratch_path, host_path);
if (status < 0)
return status;
canon:
/* Canonicalize recursively the referee in case it
* is/contains a link, moreover if it is not an
* absolute link then it is relative to
* 'guest_path'. */
status = canonicalize(tracee, scratch_path, true, guest_path, recursion_level + 1);
if (status < 0)
return status;
/* Check that a non-final canonicalized/dereferenced
* symlink exists and is a directory. */
status = substitute_binding_stat(tracee, finality, recursion_level, guest_path, host_path);
if (status < 0)
return status;
/* Here, 'guest_path' shouldn't be a symlink anymore,
* unless it is a named file descriptor. */
assert(status != 1 || sscanf(guest_path, "/proc/%*d/fd/%d", &status) == 1);
}
/* At the exit stage of the first level of recursion,
* `guest_path` is fully canonicalized but a terminating '/'
* or a terminating '.' may be required to keep the initial
* semantic of `user_path`. */
if (recursion_level == 0) {
switch (finality) {
case FINAL_NORMAL:
break;
case FINAL_SLASH:
strcpy(scratch_path, guest_path);
status = join_paths(2, guest_path, scratch_path, "");
if (status < 0)
return status;
break;
case FINAL_DOT:
strcpy(scratch_path, guest_path);
status = join_paths(2, guest_path, scratch_path, ".");
if (status < 0)
return status;
break;
default:
assert(0);
}
}
return 0;
}
