Commit Graph

13 Commits

Author SHA1 Message Date
Denys Vlasenko
b0c0b6d5ba setpriv: remove dependency on libcap headers
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2017-07-07 17:59:40 +02:00
Denys Vlasenko
2bfe7838ab setpriv: factor out capability name printing
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2017-07-07 16:09:45 +02:00
Denys Vlasenko
cf5748cc89 setpriv: code shrink, and grouping capability code together
function                                             old     new   delta
static.versions                                        -       3      +3
getcaps                                              174     149     -25

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2017-07-07 16:00:07 +02:00
Patrick Steinhardt
6842d00ceb setpriv: allow modifying ambient capabilities
With Linux 4.3, a new set of capabilities has been introduced with the
ambient capabilities. These aim to solve the problem that it was
impossible to grant run programs with elevated privileges across
non-root users. Quoting from capabilities(7):

    This is a set of capabilities that are preserved across an execve(2)
    of a program that is not privileged.  The ambient capability set
    obeys the invariant that no capability can ever be ambient if it is
    not both permitted and inheritable.

With this new set of capabilities it is now possible to run an
executable with elevated privileges as a different user, making it much
easier to do proper privilege separation.

Note though that the `--ambient-caps` switch is not part of any released
version of util-linux, yet. It has been applied in 0c92194ee (setpriv:
support modifying the set of ambient capabilities, 2017-06-24) and will
probably be part of v2.31.

function                                             old     new   delta
parse_cap                                              -     174    +174
setpriv_main                                        1246    1301     +55
.rodata                                           146307  146347     +40
static.setpriv_longopts                               40      55     +15
packed_usage                                       32092   32079     -13

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2017-07-07 02:14:23 +02:00
Patrick Steinhardt
0f49f6f926 setpriv: allow modifying inheritable caps
The main use case of setpriv is to modify the current state of
privileges available to the calling process and spawn a new executable
with the modified, new state. Next to the already supported case of
modifying the no-new-privs flag, util-linux also supports to modify
capability sets.

This commit introduces to add or drop capabilities from the set of
inheritable capabilities. Quoting from capabilities(7):

    This is a set of capabilities preserved across an execve(2).
    Inheritable capabilities remain inheritable when executing any
    program, and inheritable capabilities are added to the permitted set
    when executing a program that has the corresponding bits set in the
    file inheritable set.

As such, inheritable capabilities enable executing files with certain
privileges if the file itself has these privileges set. Note though that
inheritable capabilities are dropped across execve when running as a
non-root user.

function                                             old     new   delta
getcaps                                                -     237    +237
setpriv_main                                        1129    1246    +117
.rodata                                           146198  146307    +109
static.setpriv_longopts                               29      40     +11
packed_usage                                       32107   32092     -15

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2017-07-07 01:59:45 +02:00
Patrick Steinhardt
5e0987405c setpriv: dump ambient capabilities
As with the previous commit, this commit introduces the ability to dump
the set of ambient capabilities.

function                                             old     new   delta
setpriv_main                                         982    1129    +147
.rodata                                           146148  146198     +50

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2017-07-06 23:02:33 +02:00
Patrick Steinhardt
f34c701fa8 setpriv: dump capability bounding set
As with the previous commit, this one implements the ability to dump the
capability bounding set.

function                                             old     new   delta
setpriv_main                                         838     982    +144
.rodata                                           146101  146148     +47

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2017-07-06 22:59:23 +02:00
Patrick Steinhardt
ad63102943 setpriv: dump inheritable capability set
The setpriv executable from util-linux also dumps out information on the
different capability sets known by the kernel. By default, these are the
inheritable capabilities, bounding capabilities and (not yet released)
the ambient capabilities, which have been introduced with Linux 4.3.
This patch introduces the ability to dump the set of inheritable
capabilities.

By default, setpriv(1) identifies capabilities by their human-readable
name, for example 'net_admin'. For unknown capabilities, though, it does
instead use the capability's value, for example 'cap_12', which is
equivalent to 'net_admin'. As there is no kernel interface to retrieve
capability names by their index, we have to declare these ourselves,
which adds to setpriv's size.

To counteract, using the human-readble name has been made configurable.
The following sizes are with the 'FEATURE_SETPRIV_CAPABILITY_NAMES'
enabled:

function                                             old     new   delta
.rodata                                           145969  146405    +436
setpriv_main                                         467     842    +375
capabilities                                           -     304    +304

And with 'FEATURE_SETPRIV_CAPABILITY_NAMES' disabled:

function                                             old     new   delta
setpriv_main                                         467     838    +371
.rodata                                           145969  146101    +132

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2017-07-06 22:47:16 +02:00
Patrick Steinhardt
10c53b85c9 setpriv: dump no-new-privs info
Introduce the ability to dump the state of the no-new-privs flag, which
states whethere it is allowed to grant new privileges.

function                                             old     new   delta
setpriv_main                                         419     467     +48
.rodata                                           145926  145969     +43

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2017-07-06 22:27:22 +02:00
Denys Vlasenko
6798486141 setpriv: dump user and group info
setpriv from util-linux has an option to dump the current state
regarding privilege settings via '--dump'. It prints out information on
the real and effective user and group IDs, supplementary groups, the
no-new-privs flag, the capability sets as well as secure bits.

This patch is the start of supporting this mode. To make introduction of
the '--dump' easier to reason about, its introduction has been split
into multiple patches. This particular one introduces the ability to
print out user and group information of the current process.

function                                             old     new   delta
setpriv_main                                          89     322    +233
getresuid                                              -      41     +41
getresgid                                              -      41     +41
static.setpriv_longopts                               22      29      +7
packed_usage                                       31675   31669      -6
------------------------------------------------------------------------------
(add/remove: 4/0 grow/shrink: 2/1 up/down: 322/-6)            Total: 316 bytes

Patch by Patrick Steinhardt <ps@pks.im>

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2017-07-04 18:59:11 +02:00
Patrick Steinhardt
6a3bcf340a setpriv: prepare option parsing logic for additional opts
The current option parsing logic of setpriv only supports the case where
we want to execute a sub-program and have at most one argument. Refactor
handling of options to solve these shortcomings to make it easy to
support 'setpriv --dump', which does not accept any additional
arguments, as well as the case where additional options are passed to
setpriv. This is done by handling 'argc' ourselves, throwing an error
when no program is specified, as well as introducing an enum for the
different option bitmasks.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2017-07-04 17:15:32 +02:00
Patrick Steinhardt
d253b557a3 setpriv: do not process remaining args
By default, the 'getopt32' call will continue parsing the command line
even after hitting a non-option string. But in setpriv, this should be
avoided, as all parameters following the initial non-option argument are
in fact arguments to the binary that is to be executed by setpriv.
Otherwise, calling e.g. 'busybox setpriv ls -l' would result in an error
due to the unknown parameter "-l".

Fix the issue by passing "+" as the first character in the options
string. This will cause 'getopt32' to stop processing after hitting the
first non-option.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2017-07-04 17:10:31 +02:00
Assaf Gordon
62d1e98fbd setpriv: new applet
Add a minimal 'setpriv' implementation supporting the NO_NEW_PRIVS bit.
Typical usage:

    $ busybox setpriv sudo uname
    Linux
    $ busybox setpriv --nnp sudo uname
    sudo: effective uid is not 0, is /usr/bin/sudo on a file system with
    the 'nosuid' option set or an NFS file system without root privileges?

function                                             old     new   delta
packed_usage                                       31580   31685    +105
setpriv_main                                           -      87     +87
prctl                                                  -      53     +53
static.setpriv_longopts                                -      22     +22
applet_names                                        2620    2628      +8
applet_main                                         1516    1520      +4
------------------------------------------------------------------------------
(add/remove: 5/0 grow/shrink: 3/0 up/down: 279/0)             Total: 279 bytes

Signed-off-by: Assaf Gordon <assafgordon@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2017-06-14 11:46:52 +02:00