Let's store progname in the global variable, as it is handy to use it in
different parts of code to format messages sent to stdout.
This reduces the number of arguments, which we should pass to some functions.
This commit prepares the usage of the global progname variable.
prepare_caps_from_permitted_set() use progname value in warning messages. So,
let's rename program_name argument to progname.
If haproxy compiled with Linux capabilities support, let's show process
capabilities before applying the configuration and at runtime in 'show dev'
command output. This maybe useful for debugging purposes. Especially in
cases, when process changes its UID and GID to non-priviledged or it
has started and run under non-priviledged UID and needed capabilities are
set by admin on the haproxy binary.
To be able to show process capabilities before applying its configuration and
also at runtime in 'show dev' command output, we need to export the wrapper
around capget() syscall. It also seems more handy to place
__user_cap_header_struct in .data section and declare it as globally
accessible, as we always fill it with the same values. This avoids allocate
and fill these 8 bytes each time on the stack frame, when capget() or capset()
wrappers are called.
Expected arguments were not specified in the
prepare_caps_from_permitted_set() function declaration. It is an issue for
some compilers, for instance clang. But at the end, it is unexpected and
deprecated.
No backport needed, except if f0b6436f57 ("MEDIUM: capabilities: check
process capabilities sets") is backported.
Since the Linux capabilities support add-on (see the commit bd84387beb26
("MEDIUM: capabilities: enable support for Linux capabilities")), we can also
check haproxy process effective and permitted capabilities sets, when it
starts and runs as non-root.
Like this, if needed network capabilities are presented only in the process
permitted set, we can get this information with capget and put them in the
process effective set via capset. To do this properly, let's introduce
prepare_caps_from_permitted_set().
First, it checks if binary effective set has CAP_NET_ADMIN or CAP_NET_RAW. If
there is a match, LSTCHK_NETADM is removed from global.last_checks list to
avoid warning, because in the initialization sequence some last configuration
checks are based on LSTCHK_NETADM flag and haproxy process euid may stay
unpriviledged.
If there are no CAP_NET_ADMIN and CAP_NET_RAW in the effective set, permitted
set will be checked and only capabilities given in 'setcap' keyword will be
promoted in the process effective set. LSTCHK_NETADM will be also removed in
this case by the same reason. In order to be transparent, we promote from
permitted set only capabilities given by user in 'setcap' keyword. So, if
caplist doesn't include CAP_NET_ADMIN or CAP_NET_RAW, LSTCHK_NETADM would not
be unset and warning about missing priviledges will be emitted at
initialization.
Need to call it before protocol_bind_all() to allow binding to priviledged
ports under non-root and 'setcap cap_net_bind_service' must be set in the
global section in this case.
For a while there has been the constraint of having to run as root for
transparent proxying, and we're starting to see some cases where QUIC is
not running in socket-per-connection mode due to the missing capability
that would be needed to bind a privileged port. It's not realistic to
ask all QUIC users on port 443 to run as root, so instead let's provide
a basic support for capabilities at least on linux. The ones currently
supported are cap_net_raw, cap_net_admin and cap_net_bind_service. The
mechanism was made OS-specific with a dedicated file because it really
is. It can be easily refined later for other OSes if needed.
A new keyword "setcaps" is added to the global section, to enumerate the
capabilities that must be kept when switching from root to non-root. This
is ignored in other situations though. HAProxy has to be built with
USE_LINUX_CAP=1 for this to be supported, which is enabled by default
for linux-glibc, linux-glibc-legacy and linux-musl.
A good way to test this is to start haproxy with such a config:
global
uid 1000
setcap cap_net_bind_service
frontend test
mode http
timeout client 3s
bind quic4@:443 ssl crt rsa+dh2048.pem allow-0rtt
and run it under "sudo strace -e trace=bind,setuid", then connecting
there from an H3 client. The bind() syscall must succeed despite the
user id having been switched.
