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/*
* Copyright (C) 2015 Etienne CHAMPETIER <champetier.etienne@gmail.com>
* Copyright (C) 2020 Daniel Golle <daniel@makrotopia.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License version 2.1
* as published by the Free Software Foundation
*
* This program 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 General Public License for more details.
*/
#define _GNU_SOURCE 1
#include <syslog.h>
#include <sys/prctl.h>
#include <libubox/blobmsg.h>
#include <libubox/blobmsg_json.h>
#include "log.h"
#include "../capabilities-names.h"
#include "capabilities.h"
#define JAIL_CAP_ERROR (1LLU << (CAP_LAST_CAP+1))
#define JAIL_CAP_ALL (0xffffffffffffffffLLU)
static int find_capabilities(const char *name)
{
int i;
for (i = 0; i <= CAP_LAST_CAP; i++)
if (capabilities_names[i] && !strcasecmp(capabilities_names[i], name))
return i;
return -1;
}
enum {
OCI_CAPABILITIES_BOUNDING,
OCI_CAPABILITIES_EFFECTIVE,
OCI_CAPABILITIES_INHERITABLE,
OCI_CAPABILITIES_PERMITTED,
OCI_CAPABILITIES_AMBIENT,
__OCI_CAPABILITIES_MAX
};
static const struct blobmsg_policy oci_capabilities_policy[] = {
[OCI_CAPABILITIES_BOUNDING] = { "bounding", BLOBMSG_TYPE_ARRAY },
[OCI_CAPABILITIES_EFFECTIVE] = { "effective", BLOBMSG_TYPE_ARRAY },
[OCI_CAPABILITIES_INHERITABLE] = { "inheritable", BLOBMSG_TYPE_ARRAY },
[OCI_CAPABILITIES_PERMITTED] = { "permitted", BLOBMSG_TYPE_ARRAY },
[OCI_CAPABILITIES_AMBIENT] = { "ambient", BLOBMSG_TYPE_ARRAY },
};
static uint64_t parseOCIcap(struct blob_attr *msg)
{
struct blob_attr *cur;
int rem;
uint64_t caps = 0;
int capnum;
/* each capset is optional, set all-1 mask if absent */
if (!msg)
return JAIL_CAP_ALL;
blobmsg_for_each_attr(cur, msg, rem) {
capnum = find_capabilities(blobmsg_get_string(cur));
if (capnum < 0)
return JAIL_CAP_ERROR;
caps |= (1LLU << capnum);
}
return caps;
}
int parseOCIcapabilities(struct jail_capset *capset, struct blob_attr *msg)
{
struct blob_attr *tb[__OCI_CAPABILITIES_MAX];
uint64_t caps;
blobmsg_parse(oci_capabilities_policy, __OCI_CAPABILITIES_MAX, tb, blobmsg_data(msg), blobmsg_len(msg));
caps = parseOCIcap(tb[OCI_CAPABILITIES_BOUNDING]);
if (caps == JAIL_CAP_ERROR)
return EINVAL;
else
capset->bounding = caps;
caps = parseOCIcap(tb[OCI_CAPABILITIES_EFFECTIVE]);
if (caps == JAIL_CAP_ERROR)
return EINVAL;
else
capset->effective = caps;
caps = parseOCIcap(tb[OCI_CAPABILITIES_INHERITABLE]);
if (caps == JAIL_CAP_ERROR)
return EINVAL;
else
capset->inheritable = caps;
caps = parseOCIcap(tb[OCI_CAPABILITIES_PERMITTED]);
if (caps == JAIL_CAP_ERROR)
return EINVAL;
else
capset->permitted = caps;
caps = parseOCIcap(tb[OCI_CAPABILITIES_AMBIENT]);
if (caps == JAIL_CAP_ERROR)
return EINVAL;
else
capset->ambient = caps;
capset->apply = 1;
return 0;
}
int applyOCIcapabilities(struct jail_capset ocicapset, uint64_t retain)
{
struct __user_cap_header_struct uh = {};
struct __user_cap_data_struct ud[2];
int cap;
int is_set;
if (!ocicapset.apply)
return 0;
/* drop from bounding set */
if (ocicapset.bounding != JAIL_CAP_ALL) {
for (cap = 0; cap <= CAP_LAST_CAP; cap++) {
if (!prctl(PR_CAPBSET_READ, cap, 0, 0, 0)) {
/* can't raise */
if (ocicapset.bounding & (1LLU << cap))
ERROR("capability %s (%d) is not in bounding set\n", capabilities_names[cap], cap);
continue;
}
if ( ((ocicapset.bounding | retain) & (1LLU << cap)) == 0) {
DEBUG("dropping capability %s (%d) from bounding set\n", capabilities_names[cap], cap);
if (prctl(PR_CAPBSET_DROP, cap, 0, 0, 0)) {
ERROR("prctl(PR_CAPBSET_DROP, %d) failed: %m\n", cap);
return errno;
}
} else {
DEBUG("keeping capability %s (%d)\n", capabilities_names[cap], cap);
}
}
}
/* set effective, permitted and inheritable */
uh.version = _LINUX_CAPABILITY_VERSION_3;
uh.pid = getpid();
if (capget(&uh, ud)) {
ERROR("capget() failed\n");
return -1;
}
DEBUG("old capabilities: Pe=%016llx Pp=%016llx Pi=%016llx\n",
0LLU | ud[0].effective | (0LLU | ud[1].effective) << 32,
0LLU | ud[0].permitted | (0LLU | ud[1].permitted) << 32,
0LLU | ud[0].inheritable | (0LLU | ud[1].inheritable) << 32);
if (ocicapset.effective != JAIL_CAP_ALL) {
ud[0].effective = (ocicapset.effective | retain) & 0xFFFFFFFFU;
ud[1].effective = ((ocicapset.effective | retain) >> 32) & 0xFFFFFFFFU;
}
if (ocicapset.permitted != JAIL_CAP_ALL) {
ud[0].permitted = (ocicapset.permitted | retain) & 0xFFFFFFFFU;
ud[1].permitted = ((ocicapset.permitted | retain) >> 32) & 0xFFFFFFFFU;
}
if (ocicapset.inheritable != JAIL_CAP_ALL) {
ud[0].inheritable = (ocicapset.inheritable | retain) & 0xFFFFFFFFU;
ud[1].inheritable = ((ocicapset.inheritable | retain) >> 32) & 0xFFFFFFFFU;
}
DEBUG("new capabilities: Pe=%016llx Pp=%016llx Pi=%016llx\n",
0LLU | ud[0].effective | (0LLU | ud[1].effective) << 32,
0LLU | ud[0].permitted | (0LLU | ud[1].permitted) << 32,
0LLU | ud[0].inheritable | (0LLU | ud[1].inheritable) << 32);
if (capset(&uh, ud)) {
ERROR("capset() failed\n");
return -1;
}
/* edit ambient set */
if (ocicapset.ambient != JAIL_CAP_ALL) {
for (cap = 0; cap <= CAP_LAST_CAP; cap++) {
is_set = prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, cap, 0, 0);
if ( (ocicapset.ambient & (1LLU << cap)) == 0) {
if (is_set) {
DEBUG("dropping capability %s (%d) from ambient set\n", capabilities_names[cap], cap);
if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_LOWER, cap, 0, 0)) {
ERROR("prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_LOWER, %d, 0, 0) failed: %m\n", cap);
return errno;
}
}
} else {
if (!is_set) {
DEBUG("raising capability %s (%d) to ambient set\n", capabilities_names[cap], cap);
if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, cap, 0, 0)) {\
ERROR("prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, %d, 0, 0) failed: %m\n", cap);
return errno;
}
}
}
}
}
return 0;
}
int parseOCIcapabilities_from_file(struct jail_capset *capset, const char *file)
{
struct blob_buf b = { 0 };
int ret;
blob_buf_init(&b, 0);
ret = !blobmsg_add_json_from_file(&b, file);
if (ret) {
ERROR("failed to load %s\n", file);
goto err;
}
ret = parseOCIcapabilities(capset, b.head);
err:
blob_buf_free(&b);
return ret;
}
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