我在用
Ubuntu 18.04 Desktop
。以下是我的问题的更多细节。
最近,我正在编写一些测试代码来实现这一点:当它以非特权用户身份运行时,测试代码会尝试绑定特权端口(在我的例子中是端口1),并期望绑定失败。
在我的主机上,我当前的非特权用户具有以下内容
capsh --print
输出:
Current: =
Bounding set =cap_chown,cap_dac_override,cap_dac_read_search,cap_fowner,cap_fsetid,cap_kill,cap_setgid,cap_setuid,cap_setpcap,cap_linux_immutable,cap_net_bind_service,cap_net_broadcast,cap_net_admin,cap_net_raw,cap_ipc_lock,cap_ipc_owner,cap_sys_module,cap_sys_rawio,cap_sys_chroot,cap_sys_ptrace,cap_sys_pacct,cap_sys_admin,cap_sys_boot,cap_sys_nice,cap_sys_resource,cap_sys_time,cap_sys_tty_config,cap_mknod,cap_lease,cap_audit_write,cap_audit_control,cap_setfcap,cap_mac_override,cap_mac_admin,cap_syslog,cap_wake_alarm,cap_block_suspend,cap_audit_read
Securebits: 00/0x0/1'b0
secure-noroot: no (unlocked)
secure-no-suid-fixup: no (unlocked)
secure-keep-caps: no (unlocked)
uid=1000(ywen)
gid=1000(ywen)
groups=4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),116(lpadmin),126(sambashare),999(docker),1000(ywen)
因此,当我尝试使用当前的非特权用户绑定端口1时,我可能会像预期的那样收到权限拒绝错误:
Python 3.6.9 (default, Oct 8 2020, 12:12:24)
[GCC 8.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import socket as s
>>> o = s.socket(s.AF_INET)
>>> o.bind(("127.0.0.1", 1))
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
PermissionError: [Errno 13] Permission denied
>>> exit()
因为我的测试代码最终将在Docker容器中运行,所以我使用以下方法构建了一个镜像
Dockerfile
:
ARG UBUNTU_VERSION=18.04
FROM ubuntu:${UBUNTU_VERSION}
ARG USER_NAME=ywen
ARG USER_ID=1000
ARG GROUP_ID=1000
RUN apt-get update
# Install the needed packages.
RUN DEBIAN_FRONTEND=noninteractive apt-get -y install \
bash-completion \
libcap2-bin \
openssh-server \
openssh-client \
sudo \
tree \
vim
# Add a non-privileged user.
RUN groupadd -g ${GROUP_ID} ${USER_NAME} && \
useradd -r --create-home -u ${USER_ID} -g ${USER_NAME} ${USER_NAME}
# Give the non-privileged user the privilege to run `sudo` without a password.
RUN echo "${USER_NAME} ALL=(ALL:ALL) NOPASSWD: ALL" > /etc/sudoers.d/${USER_NAME}
# Switch to the non-root user.
USER ${USER_NAME}
# The default command when the container is run.
CMD ["/bin/sleep", "infinity"]
通过运行以下命令
docker build
命令:
docker build -f ./Dockerfile.ubuntu --tag port-binding .
生成的图像被调用
port-binding:latest
.
然后我跑了,首先
with the default capabilities as listed here
:
docker run --rm -it --name binding port-binding /bin/bash
然后我登录到容器并跑
capsh--打印
。我得到:
Current: = cap_chown,cap_dac_override,cap_fowner,cap_fsetid,cap_kill,cap_setgid,cap_setuid,cap_setpcap,cap_net_bind_service,cap_net_raw,cap_sys_chroot,cap_mknod,cap_audit_write,cap_setfcap+i
Bounding set =cap_chown,cap_dac_override,cap_fowner,cap_fsetid,cap_kill,cap_setgid,cap_setuid,cap_setpcap,cap_net_bind_service,cap_net_raw,cap_sys_chroot,cap_mknod,cap_audit_write,cap_setfcap
Securebits: 00/0x0/1'b0
secure-noroot: no (unlocked)
secure-no-suid-fixup: no (unlocked)
secure-keep-caps: no (unlocked)
uid=1000(ywen)
gid=1000(ywen)
groups=
目前,我有
cap_net_bind_service
能力。因此,当我在本文开头运行测试代码时,端口绑定可以成功,我没有收到任何错误:
Python 3.6.9 (default, Oct 8 2020, 12:12:24)
[GCC 8.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import socket as s
>>> o = s.socket(s.AF_INET)
>>> o.bind(("127.0.0.1", 1)) # Succeeded here.
>>>
我认为成功是意料之中的,因为集装箱有
cap_net_bind_service
能力。所以我停了下来,开始了一个新的容器,它掉了
cap_net_bind_service
:
docker run --rm -it --cap-drop=NET_BIND_SERVICE --name binding port-binding /bin/bash
在新容器内,
capsh--打印
未显示
cap_net_bind_service
:
Current: = cap_chown,cap_dac_override,cap_fowner,cap_fsetid,cap_kill,cap_setgid,cap_setuid,cap_setpcap,cap_net_raw,cap_sys_chroot,cap_mknod,cap_audit_write,cap_setfcap+i
Bounding set =cap_chown,cap_dac_override,cap_fowner,cap_fsetid,cap_kill,cap_setgid,cap_setuid,cap_setpcap,cap_net_raw,cap_sys_chroot,cap_mknod,cap_audit_write,cap_setfcap
Securebits: 00/0x0/1'b0
secure-noroot: no (unlocked)
secure-no-suid-fixup: no (unlocked)
secure-keep-caps: no (unlocked)
uid=1000(ywen)
gid=1000(ywen)
groups=
但当我运行测试代码时,我发现我仍然可以成功绑定端口1:
Python 3.6.9 (default, Oct 8 2020, 12:12:24)
[GCC 8.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import socket as s
>>> o = s.socket(s.AF_INET)
>>> o.bind(("127.0.0.1", 1)) # Didn't raise an error. Still succeeded here.
>>>
然而,通过阅读以下帖子,我认为删除
NET_BIND_SERVICE
这应该是正确的做法。显然,我在某个地方犯了一个错误。
有人能告诉我我做错了什么吗?
