How to change the permissions of a executable

[Wink Saville]

So as not to have to run an executable with sudo I need the owner

to be root and SUID so I've created a script:

$ cat tools/make.root.suid.sh 

#!/usr/bin/env bash

# Do two things:

#  1) Change user and group for the file to root

#  2) SUID the file (i.e. have it run with the permissions of the owner.)

# Parameters:

#   $1 is the file to execute

echo "param1=$1"

param1=$1

shift

sudo chown root:root $param1

sudo chmod u+s $param1

And then in my meson.build I tried this:

make_suid = find_program('@0@/tools/make.root.suid.sh'.format(meson.source_root()))

gen = generator(make_suid,

      output : '@PLAINNAME@',

      arguments : 'file_name',

      dependencies : test_posix_ac_inet_link)

generated = gen.process('test_posix_ac_inet_link')

run_target('run-test-posix-ac_inet_link', generated)

But I get an error:

$ ninja run-test-posix-ac_inet_link 

[0/1] Regenerating build files

The Meson build system

Version: 0.32.0

Source dir: /home/wink/prgs/sadie

Build dir: /home/wink/prgs/sadie/build-Posix

Build type: cross build

Host machine cpu family: x86

Host machine cpu: x86_64

Target machine cpu family: x86

Target machine cpu: x86_64

Build machine cpu family: x86_64

Build machine cpu: x86_64

Project name: sadie

Native c compiler: cc (gcc 6.1.1)

Cross c compiler: clang (clang 3.8.1)

Program /home/wink/prgs/sadie/tools/make.root.suid.sh found: YES (/home/wink/prgs/sadie/tools/make.root.suid.sh)

Meson encountered an error in file platform/Posix/components/ac_inet_link/tests/meson.build, line 41, column 4:

Invalid argument to run_target.

FAILED: build.ninja 

'/usr/bin/python' '/home/wink/opt/bin/meson.py' --internal regenerate '/home/wink/prgs/sadie' '/home/wink/prgs/sadie/build-Posix' --backend ninja

ninja: error: rebuilding 'build.ninja': subcommand failed

Thanks in advance!

[Jussi Pakkanen]

On Sat, Sep 3, 2016 at 7:58 PM, Wink Saville <wi...@saville.com> wrote:

> make_suid =
> find_program('@0@/tools/make.root.suid.sh'.format(meson.source_root()))
> gen = generator(make_suid,
> output : '@PLAINNAME@',
> arguments : 'file_name',
> dependencies : test_posix_ac_inet_link)
> generated = gen.process('test_posix_ac_inet_link')
> run_target('run-test-posix-ac_inet_link', generated)
>
> But I get an error:

You should probably use a custom_target instead of a generator. The
difference is subtle but think of files generated by a generator like
.o files from a C compiler. They do not do anything on their own, and
only come into existance when used in a top level target (i.e. are
linked). For creating one single output file a custom_target is
better.

An alternative is to have your runner script be set to run as root
with suid parameters and have it just invoke the result binary. This
is safer as you don't alter permission bits during build which is
always a bit dangerous.

[Wink Saville]

So I tried the following meson.build which has a custom_target :

incDirs = runtimeIncDirs + componentIncDirs

deps = [ component_dep, libruntime_dep ]

if Platform == 'Posix'

  srcFiles = firstSrcFiles + ['srcs/test.c']

  # Create test_posix_ac_inet_link executable

  test_posix_ac_inet_link = executable( 'test_posix_ac_inet_link', srcFiles,

    include_directories : incDirs,

    link_args : linkArgs,

    c_args : compilerArgs,

    dependencies : deps,

  )

  if true

    in_file = '@0@/test_posix_ac_inet_link'.format(meson.current_build_dir())

    out_file = '@0@/test_posix_ac_inet_link_x'.format(meson.current_build_dir())

    make_root_suid_file =  '@0@/tools/make_root_suid.sh'.format(meson.source_root())

    make_root_suid = find_program(make_root_suid_file)

    test_posix_ac_inet_link_x = custom_target('test_posix_ac_inet_link_x',

      input : [in_file],

      output : ['test_posix_ac_inet_link_x'],

      command : [make_root_suid, '@INPUT@', '@OUTPUT@'],

      depends : [test_posix_ac_inet_link])

    run_target('run-test-posix-ac_inet_link_x', test_posix_ac_inet_link_x)

  else

    run_target('run-test-posix-ac_inet_link', '@0@/tools/sudo.runner.sh'.format(meson.source_root()),

      test_posix_ac_inet_link)

  endif

endif

But I get the following error from meson:

$ ninja

[0/1] Regenerating build files

The Meson build system

Version: 0.32.0

Source dir: /home/wink/prgs/sadie

Build dir: /home/wink/prgs/sadie/build-Posix

Build type: cross build

Host machine cpu family: x86

Host machine cpu: x86_64

Target machine cpu family: x86

Target machine cpu: x86_64

Build machine cpu family: x86_64

Build machine cpu: x86_64

Project name: sadie

Native c compiler: cc (gcc 6.1.1)

Cross c compiler: clang (clang 3.8.1)

Program /home/wink/prgs/sadie/tools/make_root_suid.sh found: YES (/home/wink/prgs/sadie/tools/make_root_suid.sh)

Build targets in project: 61

Traceback (most recent call last):

  File "/home/wink/opt/lib/python3.5/site-packages/mesonbuild/mesonmain.py", line 265, in run

    app.generate()

  File "/home/wink/opt/lib/python3.5/site-packages/mesonbuild/mesonmain.py", line 160, in generate

    g.generate(intr)

  File "/home/wink/opt/lib/python3.5/site-packages/mesonbuild/backend/ninjabackend.py", line 178, in generate

    [self.generate_target(t, outfile) for t in self.build.get_targets().values()]

  File "/home/wink/opt/lib/python3.5/site-packages/mesonbuild/backend/ninjabackend.py", line 178, in <listcomp>

    [self.generate_target(t, outfile) for t in self.build.get_targets().values()]

  File "/home/wink/opt/lib/python3.5/site-packages/mesonbuild/backend/ninjabackend.py", line 225, in generate_target

    self.generate_run_target(target, outfile)

  File "/home/wink/opt/lib/python3.5/site-packages/mesonbuild/backend/ninjabackend.py", line 425, in generate_run_target

    elem.write(outfile)

  File "/home/wink/opt/lib/python3.5/site-packages/mesonbuild/backend/ninjabackend.py", line 112, in write

    i = i.replace('\\', '\\\\')

AttributeError: 'CustomTarget' object has no attribute 'replace'

FAILED: build.ninja 

'/usr/bin/python' '/home/wink/opt/bin/meson.py' --internal regenerate '/home/wink/prgs/sadie' '/home/wink/prgs/sadie/build-Posix' --backend ninja

ninja: error: rebuilding 'build.ninja': subcommand failed

Setting the suid bit for scripts didn't work, apparently scripts with suid are no longer supported.

Also, when I change the "if true" to "if false" and use the sudo.runner.sh that works.

What stupid thing am I doing???

[Jussi Pakkanen]

On Mon, Sep 5, 2016 at 4:42 AM, Wink Saville <wi...@saville.com> wrote:

> if true
> in_file =
> '@0@/test_posix_ac_inet_link'.format(meson.current_build_dir())
> out_file =
> '@0@/test_posix_ac_inet_link_x'.format(meson.current_build_dir())
> make_root_suid_file =
> '@0@/tools/make_root_suid.sh'.format(meson.source_root())

You should not do this. You can put the outputs of targets in command
lines and Meson will automatically make things work for you. As an
example this is not portable because a target file name is 'mytarget'
on Unix but 'mytarget.exe' on Windows. For files in the source
directory you should use make_root_suid_file =
files('make_root_suid.sh') and then put that in the command lines.

> test_posix_ac_inet_link_x = custom_target('test_posix_ac_inet_link_x',
> input : [in_file],

So here in_file should just be 'test_posix_ac_inet_link'.

> run_target('run-test-posix-ac_inet_link',
> '@0@/tools/sudo.runner.sh'.format(meson.source_root()),

And here instead of self-formatted string you should have the return
value of files() above.

> But I get the following error from meson:
>

> What stupid thing am I doing???

Nothing, this was a bug. Please test if this MR fixes it for you:

https://github.com/mesonbuild/meson/pull/768

[Wink Saville]

I've tried to clean it up:

incDirs = runtimeIncDirs + componentIncDirs

deps = [ component_dep, libruntime_dep ]

if Platform == 'Posix'

  srcFiles = firstSrcFiles + ['srcs/test.c']

  # Create test_posix_ac_inet_link_regular executable

  test_posix_ac_inet_link_regular = executable( 'test_posix_ac_inet_link_regular', srcFiles,

    include_directories : incDirs,

    link_args : linkArgs,

    c_args : compilerArgs,

    dependencies : deps,

  )

  if true

    make_root_suid_file =  '@0@/tools/make_root_suid.sh'.format(meson.source_root())

    make_root_suid = find_program(make_root_suid_file)

    test_posix_ac_inet_link = custom_target('test_posix_ac_inet_link',

      input : ['test_posix_ac_inet_link_regular'],

      output : ['test_posix_ac_inet_link'],

      command : ['make_root_suid', '@INPUT@', '@OUTPUT@'],

      depends : [test_posix_ac_inet_link_regular])

    run_target('run-test-posix-ac_inet_link', test_posix_ac_inet_link)

  else

    run_target('run-test-posix-ac_inet_link_regular', '@0@/tools/sudo.runner.sh'.format(meson.source_root()),

      test_posix_ac_inet_link_regular)

  endif

endif

I getting a DEPRECATION error about positional parameters on run_target

using 0.35-dev, but the documentation hasn't been updated.

More problematic is I don't have the dependencies and probably

something else :)

$ rm -rf * ; ~/foss/meson/meson.py -D Platform=Posix --cross-file ../cross-file-Posix-clang --buildtype=plain ..

The Meson build system

Version: 0.35.0.dev1

Source dir: /home/wink/prgs/sadie

Build dir: /home/wink/prgs/sadie/build-Posix

Build type: cross build

Host machine cpu family: x86

Host machine cpu: x86_64

Target machine cpu family: x86

Target machine cpu: x86_64

Build machine cpu family: x86_64

Build machine cpu: x86_64

Project name: sadie

Native c compiler: cc (gcc 6.1.1)

Cross c compiler: clang (clang 3.8.1)

DEPRECATION positional version of run_target is deprecated, use the keyword version instead.

Program /home/wink/prgs/sadie/tools/make_root_suid.sh found: YES (/home/wink/prgs/sadie/tools/make_root_suid.sh)

Build targets in project: 61

wink@wink-desktop:~/prgs/sadie/build-Posix

$ ninja

ninja: error: '../platform/Posix/components/ac_inet_link/tests/test_posix_ac_inet_link_regular', needed by 'platform/Posix/components/ac_inet_link/tests/test_posix_ac_inet_link', missing and no known rule to make it

[Wink Saville]

With the updates to 0.35.0-dev in #770 and additional cleanup I've done things

are look'n pretty good now.

On Wed, Sep 7, 2016 at 1:21 PM Jussi Pakkanen  wrote: