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cap-ng.c
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cap-ng.c
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/* libcap-ng.c --
* Copyright 2009-10, 2013, 2017, 2020-21 Red Hat Inc.
* All Rights Reserved.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* Authors:
* Steve Grubb <sgrubb@redhat.com>
*/
#include "config.h"
#include "cap-ng.h"
#include <string.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdio_ext.h>
#include <stdlib.h>
#include <sys/prctl.h>
#include <pwd.h>
#include <grp.h>
#include <sys/stat.h>
#include <errno.h>
#include <fcntl.h>
#include <endian.h>
#include <byteswap.h>
#ifdef HAVE_PTHREAD_H
#include <pthread.h> // For pthread_atfork
#endif
#ifdef HAVE_SYSCALL_H
#include <sys/syscall.h>
#endif
#ifdef HAVE_LINUX_SECUREBITS_H
#include <linux/securebits.h>
#endif
#ifdef HAVE_LINUX_MAGIC_H
#include <sys/vfs.h>
#include <linux/magic.h>
#endif
# define hidden __attribute__ ((visibility ("hidden")))
unsigned int last_cap hidden = 0;
/*
* Some milestones of when things became available:
* 2.6.24 kernel XATTR_NAME_CAPS
* 2.6.25 kernel PR_CAPBSET_DROP, CAPABILITY_VERSION_2
* 2.6.26 kernel PR_SET_SECUREBITS, SECURE_*_LOCKED, VERSION_3
* 3.5 kernel PR_SET_NO_NEW_PRIVS
* 4.3 kernel PR_CAP_AMBIENT
* 4.14 kernel VFS_CAP_REVISION_3
*/
#ifdef PR_CAPBSET_DROP
static int HAVE_PR_CAPBSET_DROP = 0;
#endif
#ifdef PR_SET_SECUREBITS
static int HAVE_PR_SET_SECUREBITS = 0;
#endif
#ifdef PR_SET_NO_NEW_PRIVS
static int HAVE_PR_SET_NO_NEW_PRIVS = 0;
#endif
#ifdef PR_CAP_AMBIENT
static int HAVE_PR_CAP_AMBIENT = 0;
#endif
/* External syscall prototypes */
extern int capset(cap_user_header_t header, cap_user_data_t data);
extern int capget(cap_user_header_t header, const cap_user_data_t data);
// Local functions
static void update_bounding_set(capng_act_t action, unsigned int capability,
unsigned int idx);
static void update_ambient_set(capng_act_t action, unsigned int capability,
unsigned int idx);
// Local defines
#define MASK(x) (1U << (x))
#ifdef PR_CAPBSET_DROP
#define UPPER_MASK ~((~0U)<<(last_cap-31))
#else
// For v1 systems UPPER_MASK will never be used
#define UPPER_MASK (unsigned)(~0U)
#endif
// Re-define cap_valid so its uniform between V1 and V3
#undef cap_valid
#define cap_valid(x) ((x) <= last_cap)
// If we don't have the xattr library, then we can't
// compile-in file system capabilities
#if !defined(HAVE_ATTR_XATTR_H) && !defined (HAVE_SYS_XATTR_H)
#undef VFS_CAP_U32
#endif
#ifdef VFS_CAP_U32
#ifdef HAVE_SYS_XATTR_H
#include <sys/xattr.h>
#else
#ifdef HAVE_ATTR_XATTR_H
#include <attr/xattr.h>
#endif
#endif
#if __BYTE_ORDER == __BIG_ENDIAN
#define FIXUP(x) bswap_32(x)
#else
#define FIXUP(x) (x)
#endif
#endif
#ifndef _LINUX_CAPABILITY_VERSION_1
#define _LINUX_CAPABILITY_VERSION_1 0x19980330
#endif
#ifndef _LINUX_CAPABILITY_VERSION_2
#define _LINUX_CAPABILITY_VERSION_2 0x20071026
#endif
#ifndef _LINUX_CAPABILITY_VERSION_3
#define _LINUX_CAPABILITY_VERSION_3 0x20080522
#endif
// This public API went private in the 2.6.36 kernel - hope it never changes
#ifndef XATTR_CAPS_SUFFIX
#define XATTR_CAPS_SUFFIX "capability"
#endif
#ifndef XATTR_SECURITY_PREFIX
#define XATTR_SECURITY_PREFIX "security."
#endif
#ifndef XATTR_NAME_CAPS
#define XATTR_NAME_CAPS XATTR_SECURITY_PREFIX XATTR_CAPS_SUFFIX
#endif
/* Child processes can't get caps back */
#ifndef SECURE_NOROOT
#define SECURE_NOROOT 0
#endif
#ifndef SECURE_NOROOT_LOCKED
#define SECURE_NOROOT_LOCKED 1 /* make bit-0 immutable */
#endif
/* Setuid apps run by uid 0 don't get caps back */
#ifndef SECURE_NO_SETUID_FIXUP
#define SECURE_NO_SETUID_FIXUP 2
#endif
#ifndef SECURE_NO_SETUID_FIXUP_LOCKED
#define SECURE_NO_SETUID_FIXUP_LOCKED 3 /* make bit-2 immutable */
#endif
#ifndef VFS_CAP_U32
#define VFS_CAP_U32 2
#endif
#if (VFS_CAP_U32 != 2)
#error VFS_CAP_U32 does not match the library, you need a new version
#endif
// States: new, allocated, initted, updated, applied
typedef enum { CAPNG_NEW, CAPNG_ERROR, CAPNG_ALLOCATED, CAPNG_INIT,
CAPNG_UPDATED, CAPNG_APPLIED } capng_states_t;
// Create an easy data struct out of the kernel definitions
typedef union {
struct __user_cap_data_struct v1;
struct __user_cap_data_struct v3[VFS_CAP_U32];
} cap_data_t;
// This struct keeps all state info
struct cap_ng
{
int cap_ver;
int vfs_cap_ver;
struct __user_cap_header_struct hdr;
cap_data_t data;
capng_states_t state;
__le32 rootid;
__u32 bounds[VFS_CAP_U32];
__u32 ambient[VFS_CAP_U32];
};
// Global variables with per thread uniqueness
static __thread struct cap_ng m = { 1, 1,
{0, 0},
{ {0, 0, 0} },
CAPNG_NEW, CAPNG_UNSET_ROOTID,
{0, 0},
{0, 0} };
/*
* Reset the state so that init gets called to erase everything
*/
static void deinit(void)
{
m.state = CAPNG_NEW;
}
static inline int test_cap(unsigned int cap)
{
// prctl returns 0 or 1 for valid caps, -1 otherwise
return prctl(PR_CAPBSET_READ, cap) >= 0;
}
// The maximum cap value is determined by VFS_CAP_U32
#define MAX_CAP_VALUE (VFS_CAP_U32 * sizeof(__le32) * 8)
static void init_lib(void) __attribute__ ((constructor));
static void init_lib(void)
{
// This is so dynamic libraries don't re-init
static unsigned int run_once = 0;
if (run_once)
return;
run_once = 1;
#ifdef HAVE_PTHREAD_H
pthread_atfork(NULL, NULL, deinit);
#endif
// Detect last cap
if (last_cap == 0) {
int fd;
// Try to read last cap from procfs
fd = open("/proc/sys/kernel/cap_last_cap", O_RDONLY);
if (fd >= 0) {
#ifdef HAVE_LINUX_MAGIC_H
struct statfs st;
// Bail out if procfs is invalid or fstatfs fails
if (fstatfs(fd, &st) || st.f_type != PROC_SUPER_MAGIC)
goto fail;
#endif
char buf[8];
int num = read(fd, buf, sizeof(buf) - 1);
if (num > 0) {
buf[num] = 0;
errno = 0;
unsigned int val = strtoul(buf, NULL, 10);
if (errno == 0)
last_cap = val;
}
fail:
close(fd);
}
// Run a binary search over capabilities
if (last_cap == 0) {
// starting with last_cap=MAX_CAP_VALUE means we always know
// that cap1 is invalid after the first iteration
last_cap = MAX_CAP_VALUE;
unsigned int cap0 = 0, cap1 = MAX_CAP_VALUE;
while (cap0 < last_cap) {
if (test_cap(last_cap))
cap0 = last_cap;
else
cap1 = last_cap;
last_cap = (cap0 + cap1) / 2U;
}
}
}
// Detect prctl options at runtime
#ifdef PR_CAPBSET_DROP
errno = 0;
prctl(PR_CAPBSET_READ, 0, 0, 0, 0);
if (!errno)
HAVE_PR_CAPBSET_DROP = 1;
#endif
#ifdef PR_SET_SECUREBITS
errno = 0;
prctl(PR_GET_SECUREBITS, 0, 0, 0, 0);
if (!errno)
HAVE_PR_SET_SECUREBITS = 1;
#endif
#ifdef PR_SET_NO_NEW_PRIVS
errno = 0;
prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0);
if (!errno)
HAVE_PR_SET_NO_NEW_PRIVS = 1;
#endif
#ifdef PR_CAP_AMBIENT
errno = 0;
prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, 0, 0, 0);
if (!errno)
HAVE_PR_CAP_AMBIENT = 1;
#endif
}
static void init(void)
{
// This is so static libs get initialized
init_lib();
if (m.state != CAPNG_NEW)
return;
memset(&m.hdr, 0, sizeof(m.hdr));
(void)capget(&m.hdr, NULL); // Returns -EINVAL
if (m.hdr.version == _LINUX_CAPABILITY_VERSION_3 ||
m.hdr.version == _LINUX_CAPABILITY_VERSION_2) {
m.cap_ver = 3;
} else if (m.hdr.version == _LINUX_CAPABILITY_VERSION_1) {
m.cap_ver = 1;
} else {
m.state = CAPNG_ERROR;
return;
}
#if VFS_CAP_REVISION == VFS_CAP_REVISION_1
m.vfs_cap_ver = 1;
#else
m.vfs_cap_ver = 2; // Intentionally set to 2 for both 2 & 3
#endif
memset(&m.data, 0, sizeof(cap_data_t));
#ifdef HAVE_SYSCALL_H
m.hdr.pid = (unsigned)syscall(__NR_gettid);
#else
m.hdr.pid = (unsigned)getpid();
#endif
m.rootid = CAPNG_UNSET_ROOTID;
m.state = CAPNG_ALLOCATED;
}
void capng_clear(capng_select_t set)
{
if (m.state == CAPNG_NEW)
init();
if (m.state == CAPNG_ERROR)
return;
if (set & CAPNG_SELECT_CAPS)
memset(&m.data, 0, sizeof(cap_data_t));
#ifdef PR_CAPBSET_DROP
if (HAVE_PR_CAPBSET_DROP) {
if (set & CAPNG_SELECT_BOUNDS)
memset(m.bounds, 0, sizeof(m.bounds));
}
#endif
#ifdef PR_CAP_AMBIENT
if (HAVE_PR_CAP_AMBIENT) {
if (set & CAPNG_SELECT_AMBIENT)
memset(m.ambient, 0, sizeof(m.ambient));
}
#endif
m.state = CAPNG_INIT;
}
void capng_fill(capng_select_t set)
{
if (m.state == CAPNG_NEW)
init();
if (m.state == CAPNG_ERROR)
return;
if (set & CAPNG_SELECT_CAPS) {
if (m.cap_ver == 1) {
m.data.v1.effective = 0x7FFFFFFFU;
m.data.v1.permitted = 0x7FFFFFFFU;
m.data.v1.inheritable = 0;
} else {
m.data.v3[0].effective = 0xFFFFFFFFU;
m.data.v3[0].permitted = 0xFFFFFFFFU;
m.data.v3[0].inheritable = 0;
m.data.v3[1].effective = 0xFFFFFFFFU;
m.data.v3[1].permitted = 0xFFFFFFFFU;
m.data.v3[1].inheritable = 0;
}
}
#ifdef PR_CAPBSET_DROP
if (HAVE_PR_CAPBSET_DROP) {
if (set & CAPNG_SELECT_BOUNDS) {
unsigned i;
for (i=0; i<sizeof(m.bounds)/sizeof(__u32); i++)
m.bounds[i] = 0xFFFFFFFFU;
}
}
#endif
#ifdef PR_CAP_AMBIENT
if (HAVE_PR_CAP_AMBIENT) {
if (set & CAPNG_SELECT_AMBIENT) {
unsigned i;
for (i=0; i<sizeof(m.ambient)/sizeof(__u32); i++)
m.ambient[i] = 0xFFFFFFFFU;
}
}
#endif
m.state = CAPNG_INIT;
}
void capng_setpid(int pid)
{
if (m.state == CAPNG_NEW)
init();
if (m.state == CAPNG_ERROR)
return;
m.hdr.pid = pid;
}
int capng_get_rootid(void)
{
#ifdef VFS_CAP_REVISION_3
return m.rootid;
#else
return CAPNG_UNSET_ROOTID;
#endif
}
int capng_set_rootid(int rootid)
{
#ifdef VFS_CAP_REVISION_3
if (m.state == CAPNG_NEW)
init();
if (m.state == CAPNG_ERROR)
return -1;
if (rootid < 0)
return -1;
m.rootid = rootid;
m.vfs_cap_ver = 3;
return 0;
#else
return -1;
#endif
}
#ifdef PR_CAPBSET_DROP
static int get_bounding_set(void)
{
char buf[64];
FILE *f;
int rc;
snprintf(buf, sizeof(buf), "/proc/%d/status", m.hdr.pid ? m.hdr.pid :
#ifdef HAVE_SYSCALL_H
(int)syscall(__NR_gettid));
#else
(int)getpid();
#endif
f = fopen(buf, "re");
if (f) {
__fsetlocking(f, FSETLOCKING_BYCALLER);
while (fgets(buf, sizeof(buf), f)) {
if (strncmp(buf, "CapB", 4))
continue;
sscanf(buf, "CapBnd: %08x%08x",
&m.bounds[1], &m.bounds[0]);
fclose(f);
return 0;
}
// Didn't find bounding set, fall through and try prctl way
fclose(f);
}
// Might be in a container with no procfs - do it the hard way
memset(m.bounds, 0, sizeof(m.bounds));
unsigned int i = 0;
do {
rc = prctl(PR_CAPBSET_READ, i, 0, 0, 0);
if (rc < 0)
return -1;
// Just add set bits
if (rc)
update_bounding_set(CAPNG_ADD, i%32, i>>5);
i++;
} while (cap_valid(i));
return 0;
}
#endif
#ifdef PR_CAP_AMBIENT
static int get_ambient_set(void)
{
char buf[64];
FILE *f;
int rc;
snprintf(buf, sizeof(buf), "/proc/%d/status", m.hdr.pid ? m.hdr.pid :
#ifdef HAVE_SYSCALL_H
(int)syscall(__NR_gettid));
#else
(int)getpid();
#endif
f = fopen(buf, "re");
if (f) {
__fsetlocking(f, FSETLOCKING_BYCALLER);
while (fgets(buf, sizeof(buf), f)) {
if (strncmp(buf, "CapA", 4))
continue;
sscanf(buf, "CapAmb: %08x%08x",
&m.ambient[1], &m.ambient[0]);
fclose(f);
return 0;
}
fclose(f);
// Didn't find ambient set, fall through and try prctl way
}
// Might be in a container with no procfs - do it the hard way
memset(m.ambient, 0, sizeof(m.ambient));
unsigned int i = 0;
do {
rc = prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, i, 0, 0);
if (rc < 0)
return -1;
// Just add set bits
if (rc)
update_ambient_set(CAPNG_ADD, i%32, i>>5);
i++;
} while (cap_valid(i));
return 0;
}
#endif
int capng_get_caps_process(void)
{
int rc;
if (m.state == CAPNG_NEW)
init();
if (m.state == CAPNG_ERROR)
return -1;
rc = capget((cap_user_header_t)&m.hdr, (cap_user_data_t)&m.data);
if (rc == 0) {
m.state = CAPNG_INIT;
#ifdef PR_CAPBSET_DROP
if (HAVE_PR_CAPBSET_DROP) {
rc = get_bounding_set();
if (rc < 0)
m.state = CAPNG_ERROR;
}
#endif
#ifdef PR_CAP_AMBIENT
if (HAVE_PR_CAP_AMBIENT) {
rc = get_ambient_set();
if (rc < 0)
m.state = CAPNG_ERROR;
}
#endif
}
return rc;
}
#ifdef VFS_CAP_U32
#ifdef VFS_CAP_REVISION_3
static int load_data(const struct vfs_ns_cap_data *filedata, int size)
#else
static int load_data(const struct vfs_cap_data *filedata, int size)
#endif
{
unsigned int magic;
if (m.cap_ver == 1)
return -1; // Should never get here but just in case
magic = FIXUP(filedata->magic_etc);
switch (magic & VFS_CAP_REVISION_MASK)
{
case VFS_CAP_REVISION_1:
m.vfs_cap_ver = 1;
if (size != XATTR_CAPS_SZ_1)
return -1;
break;
case VFS_CAP_REVISION_2:
m.vfs_cap_ver = 2;
if (size != XATTR_CAPS_SZ_2)
return -1;
break;
#ifdef VFS_CAP_REVISION_3
case VFS_CAP_REVISION_3:
m.vfs_cap_ver = 3;
if (size != XATTR_CAPS_SZ_3)
return -1;
break;
#endif
default:
return -1;
}
// Now stuff the data structures
m.data.v3[0].permitted = FIXUP(filedata->data[0].permitted);
m.data.v3[1].permitted = FIXUP(filedata->data[1].permitted);
m.data.v3[0].inheritable = FIXUP(filedata->data[0].inheritable);
m.data.v3[1].inheritable = FIXUP(filedata->data[1].inheritable);
if (magic & VFS_CAP_FLAGS_EFFECTIVE) {
m.data.v3[0].effective =
m.data.v3[0].permitted | m.data.v3[0].inheritable;
m.data.v3[1].effective =
m.data.v3[1].permitted | m.data.v3[1].inheritable;
} else {
m.data.v3[0].effective = 0;
m.data.v3[1].effective = 0;
}
#ifdef VFS_CAP_REVISION_3
if (size == XATTR_CAPS_SZ_3) {
struct vfs_ns_cap_data *d = (struct vfs_ns_cap_data *)filedata;
m.rootid = FIXUP(d->rootid);
}
#endif
return 0;
}
#endif
int capng_get_caps_fd(int fd)
{
#ifndef VFS_CAP_U32
return -1;
#else
int rc;
#ifdef VFS_CAP_REVISION_3
struct vfs_ns_cap_data filedata;
#else
struct vfs_cap_data filedata;
#endif
if (m.state == CAPNG_NEW)
init();
if (m.state == CAPNG_ERROR)
return -1;
rc = fgetxattr(fd, XATTR_NAME_CAPS, &filedata, sizeof(filedata));
if (rc <= 0)
return -1;
rc = load_data(&filedata, rc);
if (rc == 0)
m.state = CAPNG_INIT;
return rc;
#endif
}
static void v1_update(capng_act_t action, unsigned int capability, __u32 *data)
{
if (action == CAPNG_ADD)
*data |= MASK(capability);
else
*data &= ~(MASK(capability));
}
static void update_effective(capng_act_t action, unsigned int capability,
unsigned int idx)
{
if (action == CAPNG_ADD)
m.data.v3[idx].effective |= MASK(capability);
else
m.data.v3[idx].effective &= ~(MASK(capability));
}
static void update_permitted(capng_act_t action, unsigned int capability,
unsigned int idx)
{
if (action == CAPNG_ADD)
m.data.v3[idx].permitted |= MASK(capability);
else
m.data.v3[idx].permitted &= ~(MASK(capability));
}
static void update_inheritable(capng_act_t action, unsigned int capability,
unsigned int idx)
{
if (action == CAPNG_ADD)
m.data.v3[idx].inheritable |= MASK(capability);
else
m.data.v3[idx].inheritable &= ~(MASK(capability));
}
static void update_bounding_set(capng_act_t action, unsigned int capability,
unsigned int idx)
{
#ifdef PR_CAPBSET_DROP
if (HAVE_PR_CAPBSET_DROP) {
if (action == CAPNG_ADD)
m.bounds[idx] |= MASK(capability);
else
m.bounds[idx] &= ~(MASK(capability));
}
#endif
}
static void update_ambient_set(capng_act_t action, unsigned int capability,
unsigned int idx)
{
#ifdef PR_CAP_AMBIENT
if (HAVE_PR_CAP_AMBIENT) {
if (action == CAPNG_ADD)
m.ambient[idx] |= MASK(capability);
else
m.ambient[idx] &= ~(MASK(capability));
}
#endif
}
int capng_update(capng_act_t action, capng_type_t type, unsigned int capability)
{
// Before updating, we expect that the data is initialized to something
if (m.state < CAPNG_INIT)
return -1;
if (!cap_valid(capability)) {
errno = EINVAL;
return -1;
}
if (m.cap_ver == 1) {
if (CAPNG_EFFECTIVE & type)
v1_update(action, capability, &m.data.v1.effective);
if (CAPNG_PERMITTED & type)
v1_update(action, capability, &m.data.v1.permitted);
if (CAPNG_INHERITABLE & type)
v1_update(action, capability, &m.data.v1.inheritable);
} else {
unsigned int idx;
if (capability > 31) {
idx = capability>>5;
capability %= 32;
} else
idx = 0;
if (CAPNG_EFFECTIVE & type)
update_effective(action, capability, idx);
if (CAPNG_PERMITTED & type)
update_permitted(action, capability, idx);
if (CAPNG_INHERITABLE & type)
update_inheritable(action, capability, idx);
if (CAPNG_BOUNDING_SET & type)
update_bounding_set(action, capability, idx);
if (CAPNG_AMBIENT & type)
update_ambient_set(action, capability, idx);
}
m.state = CAPNG_UPDATED;
return 0;
}
int capng_updatev(capng_act_t action, capng_type_t type,
unsigned int capability, ...)
{
int rc;
unsigned int cap;
va_list ap;
rc = capng_update(action, type, capability);
if (rc)
return rc;
va_start(ap, capability);
cap = va_arg(ap, unsigned int);
while (cap_valid(cap)) {
rc = capng_update(action, type, cap);
if (rc)
break;
cap = va_arg(ap, unsigned int);
}
va_end(ap);
// See if planned exit or invalid
if (cap == (unsigned)-1)
rc = 0;
else {
rc = -1;
errno = EINVAL;
}
return rc;
}
int capng_apply(capng_select_t set)
{
int rc = 0;
// Before updating, we expect that the data is initialized to something
if (m.state < CAPNG_INIT)
return -1;
if (set & CAPNG_SELECT_BOUNDS) {
#ifdef PR_CAPBSET_DROP
if (HAVE_PR_CAPBSET_DROP) {
struct cap_ng state;
memcpy(&state, &m, sizeof(state)); /* save state */
capng_get_caps_process();
if (capng_have_capability(CAPNG_EFFECTIVE, CAP_SETPCAP)) {
unsigned int i;
memcpy(&m, &state, sizeof(m)); /* restore state */
for (i=0; i <= last_cap; i++) {
if (capng_have_capability(CAPNG_BOUNDING_SET,
i) == 0) {
if (prctl(PR_CAPBSET_DROP, i, 0, 0, 0) <0) {
rc = -2;
goto try_caps;
}
}
}
m.state = CAPNG_APPLIED;
if (get_bounding_set() < 0) {
rc = -3;
goto try_caps;
}
} else {
memcpy(&m, &state, sizeof(m)); /* restore state */
rc = -4;
goto try_caps;
}
}
#endif
}
// Try caps is here so that if someone had SELECT_BOTH and we blew up
// doing the bounding set, we at least try to set any capabilities
// before returning in case the caller also doesn't bother checking
// the return code.
try_caps:
if (set & CAPNG_SELECT_CAPS) {
if (capset((cap_user_header_t)&m.hdr,
(cap_user_data_t)&m.data) == 0)
m.state = CAPNG_APPLIED;
else
rc = -5;
}
// Most programs do not and should not mess with ambient capabilities.
// Instead of returning here if rc is set, we'll let it try to
// do something with ambient capabilities in hopes that it's lowering
// capabilities. Again, this is for people that don't check their
// return codes.
//
// Do ambient last so that inheritable and permitted are set by the
// time we get here.
if (set & CAPNG_SELECT_AMBIENT) {
#ifdef PR_CAP_AMBIENT
if (HAVE_PR_CAP_AMBIENT) {
if (capng_have_capabilities(CAPNG_SELECT_AMBIENT) ==
CAPNG_NONE) {
if (prctl(PR_CAP_AMBIENT,
PR_CAP_AMBIENT_CLEAR_ALL, 0, 0, 0) < 0) {
rc = -6;
goto out;
}
} else {
unsigned int i;
// Clear them all
if (prctl(PR_CAP_AMBIENT,
PR_CAP_AMBIENT_CLEAR_ALL, 0, 0, 0) < 0) {
rc = -7;
goto out;
}
for (i=0; i <= last_cap; i++) {
if (capng_have_capability(CAPNG_AMBIENT, i))
if (prctl(PR_CAP_AMBIENT,
PR_CAP_AMBIENT_RAISE, i, 0, 0) < 0){
rc = -8;
goto out;
}
}
}
m.state = CAPNG_APPLIED;
}
#endif
}
out:
return rc;
}
#ifdef VFS_CAP_U32
#ifdef VFS_CAP_REVISION_3
static int save_data(struct vfs_ns_cap_data *filedata, int *size)
#else
static int save_data(struct vfs_cap_data *filedata, int *size)
#endif
{
// Now stuff the data structures
if (m.vfs_cap_ver == 1) {
filedata->data[0].permitted = FIXUP(m.data.v1.permitted);
filedata->data[0].inheritable = FIXUP(m.data.v1.inheritable);
filedata->magic_etc = FIXUP(VFS_CAP_REVISION_1);
*size = XATTR_CAPS_SZ_1;
} else if (m.vfs_cap_ver == 2 || m.vfs_cap_ver == 3) {
int eff;
if (m.data.v3[0].effective || m.data.v3[1].effective)
eff = VFS_CAP_FLAGS_EFFECTIVE;
else
eff = 0;
filedata->data[0].permitted = FIXUP(m.data.v3[0].permitted);
filedata->data[0].inheritable = FIXUP(m.data.v3[0].inheritable);
filedata->data[1].permitted = FIXUP(m.data.v3[1].permitted);
filedata->data[1].inheritable = FIXUP(m.data.v3[1].inheritable);
filedata->magic_etc = FIXUP(VFS_CAP_REVISION_2 | eff);
*size = XATTR_CAPS_SZ_2;
}
#ifdef VFS_CAP_REVISION_3
if (m.vfs_cap_ver == 3) {
// Kernel doesn't support namespaces with non-0 rootid
if (m.rootid!= 0)
return -1;
filedata->rootid = FIXUP(m.rootid);
*size = XATTR_CAPS_SZ_3;
}
#endif
return 0;
}
#endif
int capng_apply_caps_fd(int fd)
{
#ifndef VFS_CAP_U32
return -1;
#else
int rc, size = 0;
#ifdef VFS_CAP_REVISION_3
struct vfs_ns_cap_data filedata;
#else
struct vfs_cap_data filedata;
#endif
struct stat buf;
// Before updating, we expect that the data is initialized to something
if (m.state < CAPNG_INIT)
return -1;
if (fstat(fd, &buf) != 0)
return -1;
if (S_ISLNK(buf.st_mode) || !S_ISREG(buf.st_mode)) {
errno = EINVAL;
return -1;
}
if (capng_have_capabilities(CAPNG_SELECT_CAPS) == CAPNG_NONE)
rc = fremovexattr(fd, XATTR_NAME_CAPS);
else {
if (save_data(&filedata, &size)) {
m.state = CAPNG_ERROR;
errno = EINVAL;
return -2;
}
rc = fsetxattr(fd, XATTR_NAME_CAPS, &filedata, size, 0);
}
if (rc == 0)
m.state = CAPNG_APPLIED;
return rc;
#endif
}
// Change uids keeping/removing only certain capabilities
// flag to drop supp groups
int capng_change_id(int uid, int gid, capng_flags_t flag)
{
int rc, need_setgid, need_setuid;
// Before updating, we expect that the data is initialized to something
if (m.state < CAPNG_INIT)
return -1;
// Check the current capabilities
#ifdef PR_CAPBSET_DROP
if (HAVE_PR_CAPBSET_DROP) {
// If newer kernel, we need setpcap to change the bounding set
if (capng_have_capability(CAPNG_EFFECTIVE, CAP_SETPCAP) == 0 &&
flag & CAPNG_CLEAR_BOUNDING)
capng_update(CAPNG_ADD,
CAPNG_EFFECTIVE|CAPNG_PERMITTED, CAP_SETPCAP);
}
#endif
if (gid == -1 || capng_have_capability(CAPNG_EFFECTIVE, CAP_SETGID))
need_setgid = 0;
else {
need_setgid = 1;
capng_update(CAPNG_ADD, CAPNG_EFFECTIVE|CAPNG_PERMITTED,
CAP_SETGID);
}
if (uid == -1 || capng_have_capability(CAPNG_EFFECTIVE, CAP_SETUID))
need_setuid = 0;
else {
need_setuid = 1;
capng_update(CAPNG_ADD, CAPNG_EFFECTIVE|CAPNG_PERMITTED,
CAP_SETUID);
}
// Tell system we want to keep caps across uid change
if (prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0))
return -2;
// Change to the temp capabilities
rc = capng_apply(CAPNG_SELECT_CAPS);
if (rc < 0)
return -3;