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/*
* Copyright (c) 1997-8,2019,2021 Andrew G Morgan <morgan@kernel.org>
*
* This file deals with allocation and deallocation of internal
* capability sets as specified by POSIX.1e (formerlly, POSIX 6).
*/
#include "libcap.h"
/*
* This gets set via the pre-main() executed constructor function below it.
*/
static cap_value_t _cap_max_bits;
__attribute__((constructor (300))) static void _initialize_libcap(void) {
if (_cap_max_bits) {
return;
}
cap_set_syscall(NULL, NULL);
_binary_search(_cap_max_bits, cap_get_bound, 0, __CAP_MAXBITS, __CAP_BITS);
}
cap_value_t cap_max_bits(void) {
return _cap_max_bits;
}
/*
* capability allocation is all done in terms of this structure.
*/
struct _cap_alloc_s {
__u32 magic;
__u32 size;
union {
char string_start; /* enough memory is allocated for string */
struct _cap_struct set;
struct cap_iab_s iab;
struct cap_launch_s launcher;
} u;
};
/*
* Obtain a blank set of capabilities
*/
cap_t cap_init(void)
{
struct _cap_alloc_s *raw_data;
cap_t result;
raw_data = calloc(1, sizeof(struct _cap_alloc_s));
if (raw_data == NULL) {
_cap_debug("out of memory");
errno = ENOMEM;
return NULL;
}
raw_data->magic = CAP_T_MAGIC;
raw_data->size = sizeof(struct _cap_alloc_s);
result = &raw_data->u.set;
result->head.version = _LIBCAP_CAPABILITY_VERSION;
capget(&result->head, NULL); /* load the kernel-capability version */
switch (result->head.version) {
#ifdef _LINUX_CAPABILITY_VERSION_1
case _LINUX_CAPABILITY_VERSION_1:
break;
#endif
#ifdef _LINUX_CAPABILITY_VERSION_2
case _LINUX_CAPABILITY_VERSION_2:
break;
#endif
#ifdef _LINUX_CAPABILITY_VERSION_3
case _LINUX_CAPABILITY_VERSION_3:
break;
#endif
default: /* No idea what to do */
cap_free(result);
result = NULL;
break;
}
return result;
}
/*
* This is an internal library function to duplicate a string and
* tag the result as something cap_free can handle.
*/
char *_libcap_strdup(const char *old)
{
struct _cap_alloc_s *raw_data;
size_t len;
if (old == NULL) {
errno = EINVAL;
return NULL;
}
len = strlen(old) + 1 + 2*sizeof(__u32);
if ((len & 0xffffffff) != len) {
errno = EINVAL;
return NULL;
}
raw_data = calloc(1, len);
if (raw_data == NULL) {
errno = ENOMEM;
return NULL;
}
raw_data->magic = CAP_S_MAGIC;
raw_data->size = (__u32) len;
strcpy(&raw_data->u.string_start, old);
return &raw_data->u.string_start;
}
/*
* This function duplicates an internal capability set with
* malloc()'d memory. It is the responsibility of the user to call
* cap_free() to liberate it.
*/
cap_t cap_dup(cap_t cap_d)
{
cap_t result;
__u32 *magic_p = -2 + (__u32 *) cap_d;
if (*magic_p != CAP_T_MAGIC) {
_cap_debug("bad argument");
errno = EINVAL;
return NULL;
}
result = cap_init();
if (result == NULL) {
_cap_debug("out of memory");
return NULL;
}
memcpy(result, cap_d, sizeof(*cap_d));
return result;
}
cap_iab_t cap_iab_init(void)
{
struct _cap_alloc_s *base = calloc(1, sizeof(struct _cap_alloc_s));
if (base == NULL) {
_cap_debug("out of memory");
return NULL;
}
base->magic = CAP_IAB_MAGIC;
base->size = sizeof(struct _cap_alloc_s);
return &base->u.iab;
}
/*
* cap_new_launcher allocates some memory for a launcher and
* initializes it. To actually launch a program with this launcher,
* use cap_launch(). By default, the launcher is a no-op from a
* security perspective and will act just as fork()/execve()
* would. Use cap_launcher_setuid() etc to override this.
*/
cap_launch_t cap_new_launcher(const char *arg0, const char * const *argv,
const char * const *envp)
{
struct _cap_alloc_s *data = calloc(1, sizeof(struct _cap_alloc_s));
if (data == NULL) {
_cap_debug("out of memory");
return NULL;
}
data->magic = CAP_LAUNCH_MAGIC;
data->size = sizeof(struct _cap_alloc_s);
struct cap_launch_s *attr = &data->u.launcher;
attr->arg0 = arg0;
attr->argv = argv;
attr->envp = envp;
return attr;
}
/*
* cap_func_launcher allocates some memory for a launcher and
* initializes it. The purpose of this launcher, unlike one created
* with cap_new_launcher(), is to execute some function code from a
* forked copy of the program. The forked process will exit when the
* callback function, func, returns.
*/
cap_launch_t cap_func_launcher(int (callback_fn)(void *detail))
{
struct _cap_alloc_s *data = calloc(1, sizeof(struct _cap_alloc_s));
if (data == NULL) {
_cap_debug("out of memory");
return NULL;
}
data->magic = CAP_LAUNCH_MAGIC;
data->size = sizeof(struct _cap_alloc_s);
struct cap_launch_s *attr = &data->u.launcher;
attr->custom_setup_fn = callback_fn;
return attr;
}
/*
* Scrub and then liberate the recognized allocated object.
*/
int cap_free(void *data_p)
{
if (!data_p) {
return 0;
}
/* confirm alignment */
if ((sizeof(uintptr_t)-1) & (uintptr_t) data_p) {
_cap_debug("whatever we're cap_free()ing it isn't aligned right: %p",
data_p);
errno = EINVAL;
return -1;
}
struct _cap_alloc_s *data = (void *) (-2 + (__u32 *) data_p);
switch (data->magic) {
case CAP_T_MAGIC:
case CAP_IAB_MAGIC:
case CAP_S_MAGIC:
break;
case CAP_LAUNCH_MAGIC:
(void) cap_free(&data->u.launcher.iab);
(void) cap_free(&data->u.launcher.chroot);
break;
default:
_cap_debug("don't recognize what we're supposed to liberate");
errno = EINVAL;
return -1;
}
memset(data, 0, data->size);
free(data);
data_p = NULL;
data = NULL;
return 0;
}
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