117 lines
2.9 KiB
C
117 lines
2.9 KiB
C
/*
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* Copyright (C) 2015 Etienne CHAMPETIER <champetier.etienne@gmail.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License version 2.1
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* as published by the Free Software Foundation
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#define _GNU_SOURCE 1
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#include <syslog.h>
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#include <sys/prctl.h>
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#include <libubox/blobmsg.h>
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#include <libubox/blobmsg_json.h>
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#include "log.h"
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#include "../capabilities-names.h"
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#include "capabilities.h"
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static int find_capabilities(const char *name)
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{
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int i;
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for (i = 0; i <= CAP_LAST_CAP; i++)
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if (capabilities_names[i] && !strcmp(capabilities_names[i], name))
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return i;
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return -1;
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}
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int drop_capabilities(const char *file)
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{
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enum {
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CAP_KEEP,
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CAP_DROP,
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__CAP_MAX
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};
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static const struct blobmsg_policy policy[__CAP_MAX] = {
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[CAP_KEEP] = { .name = "cap.keep", .type = BLOBMSG_TYPE_ARRAY },
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[CAP_DROP] = { .name = "cap.drop", .type = BLOBMSG_TYPE_ARRAY },
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};
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struct blob_buf b = { 0 };
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struct blob_attr *tb[__CAP_MAX];
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struct blob_attr *cur;
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int rem, cap;
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char *name;
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uint64_t capdrop = 0LLU;
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DEBUG("dropping capabilities\n");
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blob_buf_init(&b, 0);
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if (!blobmsg_add_json_from_file(&b, file)) {
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ERROR("failed to load %s\n", file);
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return -1;
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}
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blobmsg_parse(policy, __CAP_MAX, tb, blob_data(b.head), blob_len(b.head));
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if (!tb[CAP_KEEP] && !tb[CAP_DROP]) {
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ERROR("failed to parse %s\n", file);
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return -1;
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}
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blobmsg_for_each_attr(cur, tb[CAP_KEEP], rem) {
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name = blobmsg_get_string(cur);
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if (!name) {
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ERROR("invalid capability name in cap.keep\n");
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return -1;
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}
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cap = find_capabilities(name);
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if (cap == -1) {
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ERROR("unknown capability %s in cap.keep\n", name);
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return -1;
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}
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capdrop |= (1LLU << cap);
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}
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if (capdrop == 0LLU) {
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DEBUG("cap.keep empty -> only dropping capabilities from cap.drop (blacklist)\n");
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capdrop = 0xffffffffffffffffLLU;
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} else {
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DEBUG("cap.keep has at least one capability -> dropping every capabilities not in cap.keep (whitelist)\n");
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}
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blobmsg_for_each_attr(cur, tb[CAP_DROP], rem) {
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name = blobmsg_get_string(cur);
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if (!name) {
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ERROR("invalid capability name in cap.drop\n");
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return -1;
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}
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cap = find_capabilities(name);
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if (cap == -1) {
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ERROR("unknown capability %s in cap.drop\n", name);
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return -1;
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}
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capdrop &= ~(1LLU << cap);
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}
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for (cap = 0; cap <= CAP_LAST_CAP; cap++) {
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if ( (capdrop & (1LLU << cap)) == 0) {
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DEBUG("dropping capability %s (%d)\n", capabilities_names[cap], cap);
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if (prctl(PR_CAPBSET_DROP, cap, 0, 0, 0)) {
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ERROR("prctl(PR_CAPBSET_DROP, %d) failed: %s\n", cap, strerror(errno));
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return errno;
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}
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} else {
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DEBUG("keeping capability %s (%d)\n", capabilities_names[cap], cap);
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}
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}
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return 0;
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}
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