GDB in Docker for Debug - 如何在Docker容器内部使用gdb进行debug
文章目录
安全计算模式(secure computing mode,seccomp)是 Linux 内核功能,可以使用它来限制容器内可用的操作。
Docker 的默认 seccomp 配置文件是一个白名单,它指定了允许的调用。
下表列出了由于不在白名单而被有效阻止的重要(但不是全部)系统调用。该表包含每个系统调用被阻止的原因。
Syscall | Description |
---|---|
acct | Accounting syscall which could let containers disable their own resource limits or process accounting. Also gated by CAP_SYS_PACCT. |
add_key | Prevent containers from using the kernel keyring, which is not namespaced. |
adjtimex | Similar to clock_settime and settimeofday, time/date is not namespaced. Also gated by CAP_SYS_TIME. |
bpf | Deny loading potentially persistent bpf programs into kernel, already gated by CAP_SYS_ADMIN. |
clock_adjtime | Time/date is not namespaced. Also gated by CAP_SYS_TIME. |
clock_settime | Time/date is not namespaced. Also gated by CAP_SYS_TIME. |
clone | Deny cloning new namespaces. Also gated by CAP_SYSADMIN for CLONE* flags, except CLONE_USERNS. |
create_module | Deny manipulation and functions on kernel modules. Obsolete. Also gated by CAP_SYS_MODULE. |
delete_module | Deny manipulation and functions on kernel modules. Also gated by CAP_SYS_MODULE. |
finit_module | Deny manipulation and functions on kernel modules. Also gated by CAP_SYS_MODULE. |
get_kernel_syms | Deny retrieval of exported kernel and module symbols. Obsolete. |
get_mempolicy | Syscall that modifies kernel memory and NUMA settings. Already gated by CAP_SYS_NICE. |
init_module | Deny manipulation and functions on kernel modules. Also gated by CAP_SYS_MODULE. |
ioperm | Prevent containers from modifying kernel I/O privilege levels. Already gated by CAP_SYS_RAWIO. |
iopl | Prevent containers from modifying kernel I/O privilege levels. Already gated by CAP_SYS_RAWIO. |
kcmp | Restrict process inspection capabilities, already blocked by dropping CAP_PTRACE. |
kexec_file_load | Sister syscall of kexec_load that does the same thing, slightly different arguments. Also gated by CAP_SYS_BOOT. |
kexec_load | Deny loading a new kernel for later execution. Also gated by CAP_SYS_BOOT. |
keyctl | Prevent containers from using the kernel keyring, which is not namespaced. |
lookup_dcookie | Tracing/profiling syscall, which could leak a lot of information on the host. Also gated by CAP_SYS_ADMIN. |
mbind | Syscall that modifies kernel memory and NUMA settings. Already gated by CAP_SYS_NICE. |
mount | Deny mounting, already gated by CAP_SYS_ADMIN. |
move_pages | Syscall that modifies kernel memory and NUMA settings. |
name_to_handle_at | Sister syscall to open_by_handle_at. Already gated by CAP_SYS_NICE. |
nfsservctl | Deny interaction with the kernel nfs daemon. Obsolete since Linux 3.1. |
open_by_handle_at | Cause of an old container breakout. Also gated by CAP_DAC_READ_SEARCH. |
perf_event_open | Tracing/profiling syscall, which could leak a lot of information on the host. |
personality | Prevent container from enabling BSD emulation. Not inherently dangerous, but poorly tested, potential for a lot of kernel vulns. |
pivot_root | Deny pivot_root, should be privileged operation. |
process_vm_readv | Restrict process inspection capabilities, already blocked by dropping CAP_PTRACE. |
process_vm_writev | Restrict process inspection capabilities, already blocked by dropping CAP_PTRACE. |
ptrace | Tracing/profiling syscall, which could leak a lot of information on the host. Already blocked by dropping CAP_PTRACE. |
query_module | Deny manipulation and functions on kernel modules. Obsolete. |
quotactl | Quota syscall which could let containers disable their own resource limits or process accounting. Also gated by CAP_SYS_ADMIN. |
reboot | Don’t let containers reboot the host. Also gated by CAP_SYS_BOOT. |
request_key | Prevent containers from using the kernel keyring, which is not namespaced. |
set_mempolicy | Syscall that modifies kernel memory and NUMA settings. Already gated by CAP_SYS_NICE. |
setns | Deny associating a thread with a namespace. Also gated by CAP_SYS_ADMIN. |
settimeofday | Time/date is not namespaced. Also gated by CAP_SYS_TIME. |
socket, socketcall | Used to send or receive packets and for other socket operations. All socket and socketcall calls are blocked except communication domains AF_UNIX, AF_INET, AF_INET6, AF_NETLINK, and AF_PACKET. |
stime | Time/date is not namespaced. Also gated by CAP_SYS_TIME. |
swapon | Deny start/stop swapping to file/device. Also gated by CAP_SYS_ADMIN. |
swapoff | Deny start/stop swapping to file/device. Also gated by CAP_SYS_ADMIN. |
sysfs | Obsolete syscall. |
_sysctl | Obsolete, replaced by /proc/sys. |
umount | Should be a privileged operation. Also gated by CAP_SYS_ADMIN. |
umount2 | Should be a privileged operation. Also gated by CAP_SYS_ADMIN. |
unshare | Deny cloning new namespaces for processes. Also gated by CAP_SYS_ADMIN, with the exception of unshare –user. |
uselib | Older syscall related to shared libraries, unused for a long time. |
userfaultfd | Userspace page fault handling, largely needed for process migration. |
ustat | Obsolete syscall. |
vm86 | In kernel x86 real mode virtual machine. Also gated by CAP_SYS_ADMIN. |
vm86old | In kernel x86 real mode virtual machine. Also gated by CAP_SYS_ADMIN. |
其中gdb在进行进程debug时,会报错:
(gdb) attach 30721
Attaching to process 30721
ptrace: Operation not permitted.
原因就是因为ptrace被Docker默认禁止的问题。考虑到应用分析的需要,可以有以下几种方法解决:
1、关闭seccomp
docker run --security-opt seccomp=unconfined
2、采用超级权限模式
docker run --privileged
3、仅开放ptrace限制
docker run --cap-add sys_ptrace
4、server 、client 方式 (这种方式不需要设置docker本身的参数,所以更安全,更普遍,我记得android的真机调试也是server 、client方式的gdb)
使用方式可以参照:https://blog.csdn.net/zhanglianpin/article/details/80256028
当然从安全角度考虑,如只是想使用gdb进行debug的话,建议使用第三种或者第四种,第四种不需要设置任何东西。
小提示:
如果使用marathon进行docker的管理,应用JSON的修改在这里:
"parameters": [
{
"key": "cap-add",
"value": "SYS_PTRACE"
}
],