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/*
* Copyright (c) 1997-8,2019 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;
}
/*
* Obtain a blank set of capabilities
*/
cap_t cap_init(void)
{
__u32 *raw_data;
cap_t result;
raw_data = calloc(1, sizeof(__u32) + sizeof(*result));
if (raw_data == NULL) {
_cap_debug("out of memory");
errno = ENOMEM;
return NULL;
}
*raw_data = CAP_T_MAGIC;
result = (cap_t) (raw_data + 1);
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)
{
__u32 *raw_data;
if (old == NULL) {
errno = EINVAL;
return NULL;
}
raw_data = malloc( sizeof(__u32) + strlen(old) + 1 );
if (raw_data == NULL) {
errno = ENOMEM;
return NULL;
}
*(raw_data++) = CAP_S_MAGIC;
strcpy((char *) raw_data, old);
return ((char *) raw_data);
}
/*
* 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;
if (!good_cap_t(cap_d)) {
_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) {
__u32 *base = calloc(1, sizeof(__u32) + sizeof(struct cap_iab_s));
*(base++) = CAP_IAB_MAGIC;
return (cap_iab_t) base;
}
/*
* 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)
{
__u32 *data = calloc(1, sizeof(__u32) + sizeof(struct cap_launch_s));
*(data++) = CAP_LAUNCH_MAGIC;
struct cap_launch_s *attr = (struct cap_launch_s *) data;
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))
{
__u32 *data = calloc(1, sizeof(__u32) + sizeof(struct cap_launch_s));
*(data++) = CAP_LAUNCH_MAGIC;
struct cap_launch_s *attr = (struct cap_launch_s *) data;
attr->custom_setup_fn = callback_fn;
return attr;
}
/*
* Scrub and then liberate an internal capability set.
*/
int cap_free(void *data_p)
{
if (!data_p)
return 0;
if (good_cap_t(data_p)) {
data_p = -1 + (__u32 *) data_p;
memset(data_p, 0, sizeof(__u32) + sizeof(struct _cap_struct));
free(data_p);
data_p = NULL;
return 0;
}
if (good_cap_string(data_p)) {
size_t length = strlen(data_p) + sizeof(__u32);
data_p = -1 + (__u32 *) data_p;
memset(data_p, 0, length);
free(data_p);
data_p = NULL;
return 0;
}
if (good_cap_iab_t(data_p)) {
size_t length = sizeof(struct cap_iab_s) + sizeof(__u32);
data_p = -1 + (__u32 *) data_p;
memset(data_p, 0, length);
free(data_p);
data_p = NULL;
return 0;
}
if (good_cap_launch_t(data_p)) {
cap_launch_t launcher = data_p;
if (launcher->iab) {
cap_free(launcher->iab);
}
if (launcher->chroot) {
cap_free(launcher->chroot);
}
size_t length = sizeof(struct cap_iab_s) + sizeof(__u32);
data_p = -1 + (__u32 *) data_p;
memset(data_p, 0, length);
free(data_p);
data_p = NULL;
return 0;
}
_cap_debug("don't recognize what we're supposed to liberate");
errno = EINVAL;
return -1;
}
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