看来适合此工作的正确工具是fseccomp
基于sync-ignoring
Bastian Blank的f代码,我想到了一个相对较小的文件,该文件导致其所有子级无法打开文件进行写入:
/*
* Copyright (C) 2013 Joachim Breitner <mail@joachim-breitner.de>
*
* Based on code Copyright (C) 2013 Bastian Blank <waldi@debian.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#define _GNU_SOURCE 1
#include <errno.h>
#include <fcntl.h>
#include <seccomp.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#define filter_rule_add(action, syscall, count, ...) \
if (seccomp_rule_add(filter, action, syscall, count, ##__VA_ARGS__)) abort();
static int filter_init(void)
{
scmp_filter_ctx filter;
if (!(filter = seccomp_init(SCMP_ACT_ALLOW))) abort();
if (seccomp_attr_set(filter, SCMP_FLTATR_CTL_NNP, 1)) abort();
filter_rule_add(SCMP_ACT_ERRNO(EACCES), SCMP_SYS(open), 1, SCMP_A1(SCMP_CMP_MASKED_EQ, O_WRONLY, O_WRONLY));
filter_rule_add(SCMP_ACT_ERRNO(EACCES), SCMP_SYS(open), 1, SCMP_A1(SCMP_CMP_MASKED_EQ, O_RDWR, O_RDWR));
return seccomp_load(filter);
}
int main(__attribute__((unused)) int argc, char *argv[])
{
if (argc <= 1)
{
fprintf(stderr, "usage: %s COMMAND [ARG]...\n", argv[0]);
return 2;
}
if (filter_init())
{
fprintf(stderr, "%s: can't initialize seccomp filter\n", argv[0]);
return 1;
}
execvp(argv[1], &argv[1]);
if (errno == ENOENT)
{
fprintf(stderr, "%s: command not found: %s\n", argv[0], argv[1]);
return 127;
}
fprintf(stderr, "%s: failed to execute: %s: %s\n", argv[0], argv[1], strerror(errno));
return 1;
}
在这里您可以看到仍然可以读取文件:
[jojo@kirk:1] Wed, der 06.03.2013 um 12:58 Uhr Keep Smiling :-)
> ls test
ls: cannot access test: No such file or directory
> echo foo > test
bash: test: Permission denied
> ls test
ls: cannot access test: No such file or directory
> touch test
touch: cannot touch 'test': Permission denied
> head -n 1 no-writes.c # reading still works
/*
除了打开以外,它不会阻止删除文件,移动文件或其他文件操作,但是可以添加。
无需编写C代码即可启用此功能的工具是syscall_limiter。
strace
告诉您程序正在打开哪些文件。为什么要这样做?它是一个特定的程序,还是您想要对此进行测试或其他?您是否可以以无权在除当前目录之外几乎所有地方进行写操作的用户/组身份运行该程序?现代Linux发行版为每个用户使用组的概念,因此应该相对容易地进行设置。