forked from mirrors/nixpkgs
159 lines
3.9 KiB
Ruby
Executable file
159 lines
3.9 KiB
Ruby
Executable file
#!/usr/bin/env ruby
|
|
|
|
# Bind mounts hierarchy: [from, to (relative)]
|
|
# If 'to' is nil, path will be the same
|
|
mounts = [ ['/nix/store', nil],
|
|
['/dev', nil],
|
|
['/proc', nil],
|
|
['/sys', nil],
|
|
['/etc', 'host-etc'],
|
|
['/tmp', 'host-tmp'],
|
|
['/home', nil],
|
|
['/var', nil],
|
|
['/run', nil],
|
|
['/root', nil],
|
|
]
|
|
|
|
# Propagate environment variables
|
|
envvars = [ 'TERM',
|
|
'DISPLAY',
|
|
'HOME',
|
|
'XDG_RUNTIME_DIR',
|
|
'LANG',
|
|
'SSL_CERT_FILE',
|
|
]
|
|
|
|
require 'tmpdir'
|
|
require 'fileutils'
|
|
require 'pathname'
|
|
require 'set'
|
|
require 'fiddle'
|
|
|
|
def write_file(path, str)
|
|
File.open(path, 'w') { |file| file.write str }
|
|
end
|
|
|
|
# Import C standard library and several needed calls
|
|
$libc = Fiddle.dlopen nil
|
|
|
|
def make_fcall(name, args, output)
|
|
c = Fiddle::Function.new $libc[name], args, output
|
|
lambda do |*args|
|
|
ret = c.call *args
|
|
raise SystemCallError.new Fiddle.last_error if ret < 0
|
|
return ret
|
|
end
|
|
end
|
|
|
|
$fork = make_fcall 'fork', [], Fiddle::TYPE_INT
|
|
|
|
CLONE_NEWNS = 0x00020000
|
|
CLONE_NEWUSER = 0x10000000
|
|
$unshare = make_fcall 'unshare', [Fiddle::TYPE_INT], Fiddle::TYPE_INT
|
|
|
|
MS_BIND = 0x1000
|
|
MS_REC = 0x4000
|
|
$mount = make_fcall 'mount', [Fiddle::TYPE_VOIDP,
|
|
Fiddle::TYPE_VOIDP,
|
|
Fiddle::TYPE_VOIDP,
|
|
Fiddle::TYPE_LONG,
|
|
Fiddle::TYPE_VOIDP],
|
|
Fiddle::TYPE_INT
|
|
|
|
# Read command line args
|
|
abort "Usage: chrootenv swdir program args..." unless ARGV.length >= 2
|
|
swdir = Pathname.new ARGV[0]
|
|
execp = ARGV.drop 1
|
|
|
|
# Set destination paths for mounts
|
|
mounts.map! { |x| [x[0], x[1].nil? ? x[0].sub(/^\/*/, '') : x[1]] }
|
|
|
|
# Create temporary directory for root and chdir
|
|
root = Dir.mktmpdir 'chrootenv'
|
|
|
|
# Fork process; we need this to do a proper cleanup because
|
|
# child process will chroot into temporary directory.
|
|
# We use imported 'fork' instead of native to overcome
|
|
# CRuby's meddling with threads; this should be safe because
|
|
# we don't use threads at all.
|
|
$cpid = $fork.call
|
|
if $cpid == 0
|
|
# Save user UID and GID
|
|
uid = Process.uid
|
|
gid = Process.gid
|
|
|
|
# Create new mount and user namespaces
|
|
# CLONE_NEWUSER requires a program to be non-threaded, hence
|
|
# native fork above.
|
|
$unshare.call CLONE_NEWNS | CLONE_NEWUSER
|
|
|
|
# Map users and groups to the parent namespace
|
|
begin
|
|
# setgroups is only available since Linux 3.19
|
|
write_file '/proc/self/setgroups', 'deny'
|
|
rescue
|
|
end
|
|
write_file '/proc/self/uid_map', "#{uid} #{uid} 1"
|
|
write_file '/proc/self/gid_map', "#{gid} #{gid} 1"
|
|
|
|
# Do rbind mounts.
|
|
mounts.each do |x|
|
|
to = "#{root}/#{x[1]}"
|
|
FileUtils.mkdir_p to
|
|
$mount.call x[0], to, nil, MS_BIND | MS_REC, nil
|
|
end
|
|
|
|
# Chroot!
|
|
Dir.chroot root
|
|
Dir.chdir '/'
|
|
|
|
# Symlink swdir hierarchy
|
|
mount_dirs = Set.new mounts.map { |x| Pathname.new x[1] }
|
|
link_swdir = lambda do |swdir, prefix|
|
|
swdir.find do |path|
|
|
rel = prefix.join path.relative_path_from(swdir)
|
|
# Don't symlink anything in binded or symlinked directories
|
|
Find.prune if mount_dirs.include? rel or rel.symlink?
|
|
if not rel.directory?
|
|
# File does not exist; make a symlink and bail out
|
|
rel.make_symlink path
|
|
Find.prune
|
|
end
|
|
# Recursively follow symlinks
|
|
link_swdir.call path.readlink, rel if path.symlink?
|
|
end
|
|
end
|
|
link_swdir.call swdir, Pathname.new('')
|
|
|
|
# New environment
|
|
ENV.replace(Hash[ envvars.map { |x| [x, ENV[x]] } ])
|
|
|
|
# Finally, exec!
|
|
exec *execp
|
|
end
|
|
|
|
# Wait for a child. If we catch a signal, resend it to child and continue
|
|
# waiting.
|
|
def wait_child
|
|
begin
|
|
Process.wait
|
|
|
|
# Return child's exit code
|
|
if $?.exited?
|
|
exit $?.exitstatus
|
|
else
|
|
exit 1
|
|
end
|
|
rescue SignalException => e
|
|
Process.kill e.signo, $cpid
|
|
wait_child
|
|
end
|
|
end
|
|
|
|
begin
|
|
wait_child
|
|
ensure
|
|
# Cleanup
|
|
FileUtils.rm_rf root, secure: true
|
|
end
|