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From Jiang Yan Xu <...@jxu.me>
Subject Re: Review Request 69615: Disable containerizer ptrace attach.
Date Thu, 14 Feb 2019 07:07:04 GMT

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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/69615/#review212822
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src/slave/containerizer/mesos/launch.cpp
Lines 556 (patched)
<https://reviews.apache.org/r/69615/#comment298707>

    The main thing I wanted to confirm is what we chatted about offline but I didn't write
down: the interpretation of this paragraph in http://man7.org/linux/man-pages/man2/prctl.2.html
    
    ```
    PR_SET_DUMPABLE
    ...
                  Normally, this flag is set to 1.  However, it is reset to the
                  current value contained in the file /proc/sys/fs/suid_dumpable
                  (which by default has the value 0), in the following
                  circumstances:
    
                  *  The process's effective user or group ID is changed.
    ...
    ```
    
    This reads to me like, in a typical setup which runs Mesos agent as uid 0 and the task
with another uid (hence the call `os::setuid(uid.get());` below does change uid):
    
    - If `/proc/sys/fs/suid_dumpable` is the default 0, then regardless of `--allow_ptrace`
the result is that the launcher process becomes undumpable.
    - If `/proc/sys/fs/suid_dumpable` is 1, then regardless of `--allow_ptrace` the result
is that the launcher process becomes dumpable.
    
    i.e., the `prctl()` call here is a noop.
    
    Maybe I misunderstood the doc but perhaps we can tweak the test to be a `ROOT_*` test
and change to a different task user in order to verify the behavior? If you have tested it
manually that's fine too just wanted to double check :) 
    
    FWIW, I checked a sample container that we run (without this patch) and see that
    
    ```
    # ls -l /proc/1/
    ```
    
    shows the files under it are all owned by root, which does appear to mean that the process'
dumpable flag is not 1 according to http://man7.org/linux/man-pages/man5/proc.5.html?


- Jiang Yan Xu


On Feb. 8, 2019, 1:09 p.m., James Peach wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/69615/
> -----------------------------------------------------------
> 
> (Updated Feb. 8, 2019, 1:09 p.m.)
> 
> 
> Review request for mesos, Xudong Ni, Gilbert Song, Jie Yu, and Jiang Yan Xu.
> 
> 
> Bugs: MESOS-9349
>     https://issues.apache.org/jira/browse/MESOS-9349
> 
> 
> Repository: mesos
> 
> 
> Description
> -------
> 
> Use `prctl(PR_SET_DUMPABLE)` to disable the ability to attach to
> the containerizer process(es) on Linux systems. This prevents
> unprivileged containerized processes from reading information
> about the containerizer process(es) from `/proc`. This gives an
> additional layer of protection against leaking information to
> untrusted container processes.
> 
> 
> Diffs
> -----
> 
>   docs/configuration/agent.md a4015c409d00a4c117df6c869d5ba5072bcfe58e 
>   src/launcher/default_executor.cpp 5837cfa4deba557cae43112092ff24b97137951f 
>   src/launcher/executor.cpp f962e800f23d5582b1bc04a263253893492a5054 
>   src/slave/containerizer/mesos/containerizer.cpp 35f51ad33da53b3e6a8eec275fbf3e77782b0fba

>   src/slave/containerizer/mesos/launch.hpp 0a6394d56321948ad760ac69c05456319a254842 
>   src/slave/containerizer/mesos/launch.cpp 7f401cdf481123b8c6cc500ac02bb7daf2613d2c 
>   src/slave/flags.hpp 7346ba5b711a8353a4bc1d7dcd2f6184b777ddd0 
>   src/slave/flags.cpp 066b84f528b4c888dde399e0b5d5fe5531934de6 
>   src/slave/slave.cpp 0182dd2ca326723e96eef8c072696ad3c873de0b 
>   src/tests/containerizer/mesos_containerizer_tests.cpp 449928c10b897061642af8ad267f8b70695940e6

>   src/tests/slave_tests.cpp 22a0295086ae4f4ec26df00a0e077eecfa27f1fb 
> 
> 
> Diff: https://reviews.apache.org/r/69615/diff/3/
> 
> 
> Testing
> -------
> 
> make check (Fedora 29)
> 
> 
> Thanks,
> 
> James Peach
> 
>


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