#!/usr/bin/env python3
# SPDX-License-Identifier: GPL-2.0
#
# Test that truncation of bprm->buf doesn't cause unexpected execs paths, along
# with various other pathological cases.
import os, subprocess
# Relevant commits
#
# b5372fe5dc84 ("exec: load_script: Do not exec truncated interpreter path")
# 6eb3c3d0a52d ("exec: increase BINPRM_BUF_SIZE to 256")
# BINPRM_BUF_SIZE
SIZE=256
NAME_MAX=int(subprocess.check_output(["getconf", "NAME_MAX", "."]))
test_num=0
code='''#!/usr/bin/perl
print "Executed interpreter! Args:\n";
print "0 : '$0'\n";
$counter = 1;
foreach my $a (@ARGV) {
print "$counter : '$a'\n";
$counter++;
}
'''
##
# test - produce a binfmt_script hashbang line for testing
#
# @size: bytes for bprm->buf line, including hashbang but not newline
# @good: whether this script is expected to execute correctly
# @hashbang: the special 2 bytes for running binfmt_script
# @leading: any leading whitespace before the executable path
# @root: start of executable pathname
# @target: end of executable pathname
# @arg: bytes following the executable pathname
# @fill: character to fill between @root and @target to reach @size bytes
# @newline: character to use as newline, not counted towards @size
# ...
def test(name, size, good=True, leading="", root="./", target="/perl",
fill="A", arg="", newline="\n", hashbang="#!"):
global test_num, tests, NAME_MAX
test_num += 1
if test_num > tests:
raise ValueError("more binfmt_script tests than expected! (want %d, expected %d)"
% (test_num, tests))
middle = ""
remaining = size - len(hashbang) - len(leading) - len(root) - len(target) - len(arg)
# The middle of the pathname must not exceed NAME_MAX
while remaining >= NAME_MAX:
middle += fill * (NAME_MAX - 1)
middle += '/'
remaining -= NAME_MAX
middle += fill * remaining
dirpath = root + middle
binary = dirpath + target
if len(target):
os.makedirs(dirpath, mode=0o755, exist_ok=True)
open(binary, "w").write(code)
os.chmod(binary, 0o755)
buf=hashbang + leading + root + middle + target + arg + newline
if len(newline) > 0:
buf += 'echo this is not really perl\n'
script = "binfmt_script-%s" % (name)
open(script, "w").write(buf)
os.chmod(script, 0o755)
proc = subprocess.Popen(["./%s" % (script)], shell=True,
stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
stdout = proc.communicate()[0]
if proc.returncode == 0 and b'Executed interpreter' in stdout:
if good:
print("ok %d - binfmt_script %s (successful good exec)"
% (test_num, name))
else:
print("not ok %d - binfmt_script %s succeeded when it should have failed"
% (test_num, name))
else:
if good:
print("not ok %d - binfmt_script %s failed when it should have succeeded (rc:%d)"
% (test_num, name, proc.returncode))
else:
print("ok %d - binfmt_script %s (correctly failed bad exec)"
% (test_num, name))
# Clean up crazy binaries
os.unlink(script)
if len(target):
elements = binary.split('/')
os.unlink(binary)
elements.pop()
while len(elements) > 1:
os.rmdir("/".join(elements))
elements.pop()
tests=27
print("TAP version 1.3")
print("1..%d" % (tests))
### FAIL (8 tests)
# Entire path is well past the BINFMT_BUF_SIZE.
test(name="too-big", size=SIZE+80, good=False)
# Path is right at max size, making it impossible to tell if it was truncated.
test(name="exact", size=SIZE, good=False)
# Same as above, but with leading whitespace.
test(name="exact-space", size=SIZE, good=False, leading=" ")
# Huge buffer of only whitespace.
test(name="whitespace-too-big", size=SIZE+71, good=False, root="",
fill=" ", target="")
# A good path, but it gets truncated due to leading whitespace.
test(name="truncated", size=SIZE+17, good=False, leading=" " * 19)
# Entirely empty except for #!
test(name="empty", size=2, good=False, root="",
fill="", target="", newline="")
# Within size, but entirely spaces
test(name="spaces", size=SIZE-1, good=False, root="", fill=" ",
target="", newline="")
# Newline before binary.
test(name="newline-prefix", size=SIZE-1, good=False, leading="\n",
root="", fill=" ", target="")
### ok (19 tests)
# The original test case that was broken by commit:
# 8099b047ecc4 ("exec: load_script: don't blindly truncate shebang string")
test(name="test.pl", size=439, leading=" ",
root="./nix/store/bwav8kz8b3y471wjsybgzw84mrh4js9-perl-5.28.1/bin",
arg=" -I/nix/store/x6yyav38jgr924nkna62q3pkp0dgmzlx-perl5.28.1-File-Slurp-9999.25/lib/perl5/site_perl -I/nix/store/ha8v67sl8dac92r9z07vzr4gv1y9nwqz-perl5.28.1-Net-DBus-1.1.0/lib/perl5/site_perl -I/nix/store/dcrkvnjmwh69ljsvpbdjjdnqgwx90a9d-perl5.28.1-XML-Parser-2.44/lib/perl5/site_perl -I/nix/store/rmji88k2zz7h4zg97385bygcydrf2q8h-perl5.28.1-XML-Twig-3.52/lib/perl5/site_perl")
# One byte under size, leaving newline visible.
test(name="one-under", size=SIZE-1)
# Two bytes under size, leaving newline visible.
test(name="two-under", size=SIZE-2)
# Exact size, but trailing whitespace visible instead of newline
test(name="exact-trunc-whitespace", size=SIZE, arg=" ")
# Exact size, but trailing space and first arg char visible instead of newline.
test(name="exact-trunc-arg", size=SIZE, arg=" f")
# One bute under, with confirmed non-truncated arg since newline now visible.
test(name="one-under-full-arg", size=SIZE-1, arg=" f")
# Short read buffer by one byte.
test(name="one-under-no-nl", size=SIZE-1, newline="")
# Short read buffer by half buffer size.
test(name="half-under-no-nl", size=int(SIZE/2), newline="")
# One byte under with whitespace arg. leaving wenline visible.
test(name="one-under-trunc-arg", size=SIZE-1, arg=" ")
# One byte under with whitespace leading. leaving wenline visible.
test(name="one-under-leading", size=SIZE-1, leading=" ")
# One byte under with whitespace leading and as arg. leaving newline visible.
test(name="one-under-leading-trunc-arg", size=SIZE-1, leading=" ", arg=" ")
# Same as above, but with 2 bytes under
test(name="two-under-no-nl", size=SIZE-2, newline="")
test(name="two-under-trunc-arg", size=SIZE-2, arg=" ")
test(name="two-under-leading", size=SIZE-2, leading=" ")
test(name="two-under-leading-trunc-arg", size=SIZE-2, leading=" ", arg=" ")
# Same as above, but with buffer half filled
test(name="two-under-no-nl", size=int(SIZE/2), newline="")
test(name="two-under-trunc-arg", size=int(SIZE/2), arg=" ")
test(name="two-under-leading", size=int(SIZE/2), leading=" ")
test(name="two-under-lead-trunc-arg", size=int(SIZE/2), leading=" ", arg=" ")
if test_num != tests:
raise ValueError("fewer binfmt_script tests than expected! (ran %d, expected %d"
% (test_num, tests))