Hi Dominik! I don't know if you got what I replied on IRC, but basically I was wrong there as I only focused on init time capability setting and not on the runtime errors. Sorry. :) I can only agree with @algernon's statement I have found examples of capability mishandling too (although in some points we do check what kind of capability is needed, in affile/file-opener). Reflecting on your topics:
In my opinion, there are 2 bugs in syslog-ng: * if I tell a daemon to run as unprivileged user I do not expect it to write files as user root. What syslog-ng is doing basically is faking being an unprivileged user, while retaining capabilities which are equivalent to full root permissions. Syslog-ng should imho either run as root, with capabilities; OR as unprivileged user without capabilities (except those explicitly given in --caps) * syslog-ng drops to the capabilities it gets told in --caps, but later g_process_cap_modify() ignores what was specified.
1. creating files as root: I can confirm that files are created with root even if --user or --group is used. Although we call setuid() in gprocess at startup, during file opening we use file permissions explicitly from the global config, which defaults to root. I think this is a bug too and we should solve it. What you can do as **workaround** is to set file() options: owner() group() without a value in the configuration. We documented this too: https://syslog-ng.com/documents/html/syslog-ng-ose-latest-guides/en/syslog-n... 2. syslog-ng drops capabilities Syslog-ng sets capabilities given with options --caps at startup. I think the issue here is that some capabilities are hard-wired into syslog-ng (as you have found calls of g_process_cap_modify()). BR, Gabor On Wed, Apr 18, 2018 at 3:49 PM, Scheidler, Balázs <balazs.scheidler@balabit.com> wrote:
Also, you can tell it not to manage capabilities with the --no-caps command line option.
-- Bazsi
On Wed, Apr 18, 2018 at 3:18 PM, Gergely Nagy <algernon@balabit.com> wrote:
Hi!
> "Russenberger" == Russenberger Dominik > <dominik.russenberger@terreactive.ch> writes:
Russenberger> Hi List, Russenberger> I recently noticed something very strange: although I run syslog-ng as Russenberger> an unprivileged user (with -u log -g log), newly created logfiles were Russenberger> owned by root. syslog-ng shows up running as user log in ps, as expected.
Russenberger> In my opinion, there are 2 bugs in syslog-ng: Russenberger> * if I tell a daemon to run as unprivileged user I do not expect it to Russenberger> write files as user root. What syslog-ng is doing basically is faking Russenberger> being an unprivileged user, while retaining capabilities which are Russenberger> equivalent to full root permissions. Russenberger> Syslog-ng should imho either run as root, with capabilities; Russenberger> OR as unprivileged user without capabilities (except those Russenberger> explicitly given in --caps) Russenberger> * syslog-ng drops to the capabilities it gets told in --caps, Russenberger> but later g_process_cap_modify() ignores what was specified.
While I agree about your conclusion that syslog-ng should not use more capabilities than it is told - or what it needs to -, I'd like to shed some light on why it tries to raise its capabilities despite you telling it to run with less.
The reason is actually pretty simple: syslog-ng supports the `owner()` and `group()` options for some destinations, so that it can create output files as a different user than syslog-ng is running under. For this reason, whenever creating such files, it first tries to raise its capabilities, just to make sure it can create them. We currently do not keep track of whether this is required or not, we try to raise anyway.
We should probably change that, and only raise capabilities if we really need to. This should solve the issue you are seeing.
-- |8]
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