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b081320f06
While working on commitb5372fe5dc("exec: load_script: Do not exec truncated interpreter path"), I wrote a series of test scripts to verify corner cases. However, soon after, commit6eb3c3d0a5("exec: increase BINPRM_BUF_SIZE to 256") landed, resulting in the tests needing to be refactored for the larger BINPRM_BUF_SIZE, which got lost on my TODO list. During the recent exec refactoring work[1], the need for these tests resurfaced, so I've finished them up for addition to the kernel selftests. [1] https://lore.kernel.org/lkml/202005191144.E3112135@keescook/ Link: https://lkml.kernel.org/r/202005200204.D07DF079@keescook Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
172 lines
7.1 KiB
Python
Executable File
172 lines
7.1 KiB
Python
Executable File
#!/usr/bin/env python3
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# SPDX-License-Identifier: GPL-2.0
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#
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# Test that truncation of bprm->buf doesn't cause unexpected execs paths, along
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# with various other pathological cases.
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import os, subprocess
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# Relevant commits
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#
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# b5372fe5dc84 ("exec: load_script: Do not exec truncated interpreter path")
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# 6eb3c3d0a52d ("exec: increase BINPRM_BUF_SIZE to 256")
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# BINPRM_BUF_SIZE
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SIZE=256
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NAME_MAX=int(subprocess.check_output(["getconf", "NAME_MAX", "."]))
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test_num=0
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code='''#!/usr/bin/perl
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print "Executed interpreter! Args:\n";
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print "0 : '$0'\n";
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$counter = 1;
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foreach my $a (@ARGV) {
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print "$counter : '$a'\n";
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$counter++;
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}
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'''
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##
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# test - produce a binfmt_script hashbang line for testing
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#
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# @size: bytes for bprm->buf line, including hashbang but not newline
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# @good: whether this script is expected to execute correctly
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# @hashbang: the special 2 bytes for running binfmt_script
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# @leading: any leading whitespace before the executable path
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# @root: start of executable pathname
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# @target: end of executable pathname
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# @arg: bytes following the executable pathname
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# @fill: character to fill between @root and @target to reach @size bytes
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# @newline: character to use as newline, not counted towards @size
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# ...
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def test(name, size, good=True, leading="", root="./", target="/perl",
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fill="A", arg="", newline="\n", hashbang="#!"):
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global test_num, tests, NAME_MAX
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test_num += 1
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if test_num > tests:
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raise ValueError("more binfmt_script tests than expected! (want %d, expected %d)"
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% (test_num, tests))
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middle = ""
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remaining = size - len(hashbang) - len(leading) - len(root) - len(target) - len(arg)
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# The middle of the pathname must not exceed NAME_MAX
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while remaining >= NAME_MAX:
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middle += fill * (NAME_MAX - 1)
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middle += '/'
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remaining -= NAME_MAX
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middle += fill * remaining
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dirpath = root + middle
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binary = dirpath + target
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if len(target):
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os.makedirs(dirpath, mode=0o755, exist_ok=True)
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open(binary, "w").write(code)
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os.chmod(binary, 0o755)
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buf=hashbang + leading + root + middle + target + arg + newline
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if len(newline) > 0:
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buf += 'echo this is not really perl\n'
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script = "binfmt_script-%s" % (name)
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open(script, "w").write(buf)
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os.chmod(script, 0o755)
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proc = subprocess.Popen(["./%s" % (script)], shell=True,
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stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
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stdout = proc.communicate()[0]
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if proc.returncode == 0 and b'Executed interpreter' in stdout:
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if good:
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print("ok %d - binfmt_script %s (successful good exec)"
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% (test_num, name))
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else:
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print("not ok %d - binfmt_script %s succeeded when it should have failed"
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% (test_num, name))
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else:
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if good:
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print("not ok %d - binfmt_script %s failed when it should have succeeded (rc:%d)"
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% (test_num, name, proc.returncode))
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else:
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print("ok %d - binfmt_script %s (correctly failed bad exec)"
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% (test_num, name))
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# Clean up crazy binaries
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os.unlink(script)
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if len(target):
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elements = binary.split('/')
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os.unlink(binary)
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elements.pop()
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while len(elements) > 1:
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os.rmdir("/".join(elements))
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elements.pop()
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tests=27
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print("TAP version 1.3")
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print("1..%d" % (tests))
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### FAIL (8 tests)
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# Entire path is well past the BINFMT_BUF_SIZE.
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test(name="too-big", size=SIZE+80, good=False)
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# Path is right at max size, making it impossible to tell if it was truncated.
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test(name="exact", size=SIZE, good=False)
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# Same as above, but with leading whitespace.
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test(name="exact-space", size=SIZE, good=False, leading=" ")
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# Huge buffer of only whitespace.
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test(name="whitespace-too-big", size=SIZE+71, good=False, root="",
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fill=" ", target="")
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# A good path, but it gets truncated due to leading whitespace.
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test(name="truncated", size=SIZE+17, good=False, leading=" " * 19)
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# Entirely empty except for #!
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test(name="empty", size=2, good=False, root="",
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fill="", target="", newline="")
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# Within size, but entirely spaces
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test(name="spaces", size=SIZE-1, good=False, root="", fill=" ",
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target="", newline="")
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# Newline before binary.
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test(name="newline-prefix", size=SIZE-1, good=False, leading="\n",
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root="", fill=" ", target="")
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### ok (19 tests)
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# The original test case that was broken by commit:
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# 8099b047ecc4 ("exec: load_script: don't blindly truncate shebang string")
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test(name="test.pl", size=439, leading=" ",
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root="./nix/store/bwav8kz8b3y471wjsybgzw84mrh4js9-perl-5.28.1/bin",
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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")
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# One byte under size, leaving newline visible.
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test(name="one-under", size=SIZE-1)
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# Two bytes under size, leaving newline visible.
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test(name="two-under", size=SIZE-2)
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# Exact size, but trailing whitespace visible instead of newline
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test(name="exact-trunc-whitespace", size=SIZE, arg=" ")
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# Exact size, but trailing space and first arg char visible instead of newline.
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test(name="exact-trunc-arg", size=SIZE, arg=" f")
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# One bute under, with confirmed non-truncated arg since newline now visible.
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test(name="one-under-full-arg", size=SIZE-1, arg=" f")
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# Short read buffer by one byte.
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test(name="one-under-no-nl", size=SIZE-1, newline="")
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# Short read buffer by half buffer size.
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test(name="half-under-no-nl", size=int(SIZE/2), newline="")
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# One byte under with whitespace arg. leaving wenline visible.
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test(name="one-under-trunc-arg", size=SIZE-1, arg=" ")
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# One byte under with whitespace leading. leaving wenline visible.
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test(name="one-under-leading", size=SIZE-1, leading=" ")
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# One byte under with whitespace leading and as arg. leaving newline visible.
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test(name="one-under-leading-trunc-arg", size=SIZE-1, leading=" ", arg=" ")
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# Same as above, but with 2 bytes under
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test(name="two-under-no-nl", size=SIZE-2, newline="")
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test(name="two-under-trunc-arg", size=SIZE-2, arg=" ")
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test(name="two-under-leading", size=SIZE-2, leading=" ")
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test(name="two-under-leading-trunc-arg", size=SIZE-2, leading=" ", arg=" ")
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# Same as above, but with buffer half filled
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test(name="two-under-no-nl", size=int(SIZE/2), newline="")
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test(name="two-under-trunc-arg", size=int(SIZE/2), arg=" ")
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test(name="two-under-leading", size=int(SIZE/2), leading=" ")
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test(name="two-under-lead-trunc-arg", size=int(SIZE/2), leading=" ", arg=" ")
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if test_num != tests:
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raise ValueError("fewer binfmt_script tests than expected! (ran %d, expected %d"
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% (test_num, tests))
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