1 #!/usr/bin/env python3
2 # SPDX-License-Identifier: GPL-2.0
3 #
4 # Test that truncation of bprm->buf doesn't cause unexpected execs paths, along
5 # with various other pathological cases.
6 import os, subprocess
7
8 # Relevant commits
9 #
10 # b5372fe5dc84 ("exec: load_script: Do not exec truncated interpreter path")
11 # 6eb3c3d0a52d ("exec: increase BINPRM_BUF_SIZE to 256")
12
13 # BINPRM_BUF_SIZE
14 SIZE=256
15
16 NAME_MAX=int(subprocess.check_output(["getconf", "NAME_MAX", "."]))
17
18 test_num=0
19 pass_num=0
20 fail_num=0
21
22 code='''#!/usr/bin/perl
23 print "Executed interpreter! Args:\n";
24 print "0 : '$0'\n";
25 $counter = 1;
26 foreach my $a (@ARGV) {
27 print "$counter : '$a'\n";
28 $counter++;
29 }
30 '''
31
32 ##
33 # test - produce a binfmt_script hashbang line for testing
34 #
35 # @size: bytes for bprm->buf line, including hashbang but not newline
36 # @good: whether this script is expected to execute correctly
37 # @hashbang: the special 2 bytes for running binfmt_script
38 # @leading: any leading whitespace before the executable path
39 # @root: start of executable pathname
40 # @target: end of executable pathname
41 # @arg: bytes following the executable pathname
42 # @fill: character to fill between @root and @target to reach @size bytes
43 # @newline: character to use as newline, not counted towards @size
44 # ...
45 def test(name, size, good=True, leading="", root="./", target="/perl",
46 fill="A", arg="", newline="\n", hashbang="#!"):
47 global test_num, pass_num, fail_num, tests, NAME_MAX
48 test_num += 1
49 if test_num > tests:
50 raise ValueError("more binfmt_script tests than expected! (want %d, expected %d)"
51 % (test_num, tests))
52
53 middle = ""
54 remaining = size - len(hashbang) - len(leading) - len(root) - len(target) - len(arg)
55 # The middle of the pathname must not exceed NAME_MAX
56 while remaining >= NAME_MAX:
57 middle += fill * (NAME_MAX - 1)
58 middle += '/'
59 remaining -= NAME_MAX
60 middle += fill * remaining
61
62 dirpath = root + middle
63 binary = dirpath + target
64 if len(target):
65 os.makedirs(dirpath, mode=0o755, exist_ok=True)
66 open(binary, "w").write(code)
67 os.chmod(binary, 0o755)
68
69 buf=hashbang + leading + root + middle + target + arg + newline
70 if len(newline) > 0:
71 buf += 'echo this is not really perl\n'
72
73 script = "binfmt_script-%s" % (name)
74 open(script, "w").write(buf)
75 os.chmod(script, 0o755)
76
77 proc = subprocess.Popen(["./%s" % (script)], shell=True,
78 stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
79 stdout = proc.communicate()[0]
80
81 if proc.returncode == 0 and b'Executed interpreter' in stdout:
82 if good:
83 print("ok %d - binfmt_script %s (successful good exec)"
84 % (test_num, name))
85 pass_num += 1
86 else:
87 print("not ok %d - binfmt_script %s succeeded when it should have failed"
88 % (test_num, name))
89 fail_num = 1
90 else:
91 if good:
92 print("not ok %d - binfmt_script %s failed when it should have succeeded (rc:%d)"
93 % (test_num, name, proc.returncode))
94 fail_num = 1
95 else:
96 print("ok %d - binfmt_script %s (correctly failed bad exec)"
97 % (test_num, name))
98 pass_num += 1
99
100 # Clean up crazy binaries
101 os.unlink(script)
102 if len(target):
103 elements = binary.split('/')
104 os.unlink(binary)
105 elements.pop()
106 while len(elements) > 1:
107 os.rmdir("/".join(elements))
108 elements.pop()
109
110 tests=27
111 print("TAP version 1.3")
112 print("1..%d" % (tests))
113
114 ### FAIL (8 tests)
115
116 # Entire path is well past the BINFMT_BUF_SIZE.
117 test(name="too-big", size=SIZE+80, good=False)
118 # Path is right at max size, making it impossible to tell if it was truncated.
119 test(name="exact", size=SIZE, good=False)
120 # Same as above, but with leading whitespace.
121 test(name="exact-space", size=SIZE, good=False, leading=" ")
122 # Huge buffer of only whitespace.
123 test(name="whitespace-too-big", size=SIZE+71, good=False, root="",
124 fill=" ", target="")
125 # A good path, but it gets truncated due to leading whitespace.
126 test(name="truncated", size=SIZE+17, good=False, leading=" " * 19)
127 # Entirely empty except for #!
128 test(name="empty", size=2, good=False, root="",
129 fill="", target="", newline="")
130 # Within size, but entirely spaces
131 test(name="spaces", size=SIZE-1, good=False, root="", fill=" ",
132 target="", newline="")
133 # Newline before binary.
134 test(name="newline-prefix", size=SIZE-1, good=False, leading="\n",
135 root="", fill=" ", target="")
136
137 ### ok (19 tests)
138
139 # The original test case that was broken by commit:
140 # 8099b047ecc4 ("exec: load_script: don't blindly truncate shebang string")
141 test(name="test.pl", size=439, leading=" ",
142 root="./nix/store/bwav8kz8b3y471wjsybgzw84mrh4js9-perl-5.28.1/bin",
143 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")
144 # One byte under size, leaving newline visible.
145 test(name="one-under", size=SIZE-1)
146 # Two bytes under size, leaving newline visible.
147 test(name="two-under", size=SIZE-2)
148 # Exact size, but trailing whitespace visible instead of newline
149 test(name="exact-trunc-whitespace", size=SIZE, arg=" ")
150 # Exact size, but trailing space and first arg char visible instead of newline.
151 test(name="exact-trunc-arg", size=SIZE, arg=" f")
152 # One bute under, with confirmed non-truncated arg since newline now visible.
153 test(name="one-under-full-arg", size=SIZE-1, arg=" f")
154 # Short read buffer by one byte.
155 test(name="one-under-no-nl", size=SIZE-1, newline="")
156 # Short read buffer by half buffer size.
157 test(name="half-under-no-nl", size=int(SIZE/2), newline="")
158 # One byte under with whitespace arg. leaving wenline visible.
159 test(name="one-under-trunc-arg", size=SIZE-1, arg=" ")
160 # One byte under with whitespace leading. leaving wenline visible.
161 test(name="one-under-leading", size=SIZE-1, leading=" ")
162 # One byte under with whitespace leading and as arg. leaving newline visible.
163 test(name="one-under-leading-trunc-arg", size=SIZE-1, leading=" ", arg=" ")
164 # Same as above, but with 2 bytes under
165 test(name="two-under-no-nl", size=SIZE-2, newline="")
166 test(name="two-under-trunc-arg", size=SIZE-2, arg=" ")
167 test(name="two-under-leading", size=SIZE-2, leading=" ")
168 test(name="two-under-leading-trunc-arg", size=SIZE-2, leading=" ", arg=" ")
169 # Same as above, but with buffer half filled
170 test(name="two-under-no-nl", size=int(SIZE/2), newline="")
171 test(name="two-under-trunc-arg", size=int(SIZE/2), arg=" ")
172 test(name="two-under-leading", size=int(SIZE/2), leading=" ")
173 test(name="two-under-lead-trunc-arg", size=int(SIZE/2), leading=" ", arg=" ")
174
175 print("# Totals: pass:%d fail:%d xfail:0 xpass:0 skip:0 error:0" % (pass_num, fail_num))
176
177 if test_num != tests:
178 raise ValueError("fewer binfmt_script tests than expected! (ran %d, expected %d"
179 % (test_num, tests))
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