Solve the problem of not being able to enter breakpoints when using GDB in Docker

question

Running gdb in docker, hitting a breakpoint, but unable to enter the breakpoint

reason

In order to ensure the security of the host, Docker has enabled many security settings, including ASLR (Address space layout randomization), that is, the memory address in Docker is different from the memory address of the host.

ASLR will cause address-dependent programs such as GDB to not work properly.

Workaround

Use docker's super privileges, add --privileged (two dashes, markdown syntax

like:

docker run --privileged …

GDB will work normally

Super permissions will disable many security settings, allowing you to make full use of Docker capabilities

For example, you can open docker in docker, haha.

Additional knowledge: docker ptrace: Operation not permitted. How to deal with it

When gdb in docker is debugging a process, an error will be reported:

(gdb) attach 30721

Attaching to process 30721

ptrace: Operation not permitted.

The reason is that ptrace is disabled by default in Docker. Considering the needs of application analysis, there are several solutions:

1. Turn off seccomp

docker run --security-opt seccomp=unconfined

2. Use super permission mode

docker run --privileged

3. Only open ptrace restrictions

docker run --cap-add sys_ptrace

Of course, from a security perspective, if you just want to use gdb for debugging, it is recommended to use the third method.

Secure computing mode (seccomp) is a Linux kernel feature that can be used to restrict the operations available within a container.

The default seccomp profile for Docker is a whitelist that specifies the calls that are allowed.

The following table lists important (but not all) system calls that are effectively blocked because they are not on the whitelist. This table contains the reason why each system call was blocked.

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