Enough research will tend to support your theory. | |
Murphy's Law of Research |
This is the platform dependent part of Scanners (i).
First a sample from file to show how the sed part is supposed to work.
Source: pre/sparc-debian2.2-linux/scanner/file.sh
#!/bin/bash
/usr/bin/file /bin/bash | /usr/bin/fmt |
Output: out/sparc-debian2.2-linux/scanner/file
/bin/bash: ELF 32-bit MSB executable, SPARC, version 1, dynamically linked
(uses shared libs), stripped |
And now the output of find_exec.sh for both the big and the small set of target executables. Typical Linux distributions have very few statically linked programs. On traditional system the number is much higher.
Output: out/sparc-debian2.2-linux/scanner/big.wc
[] /bin /sbin /usr/bin /usr/sbin /usr/lib
2 out/sparc-debian2.2-linux/scanner/big.static
628 out/sparc-debian2.2-linux/scanner/big.dynamic
630 total |
Output: out/sparc-debian2.2-linux/scanner/small.wc
[_infected] tmp/sparc-debian2.2-linux
0 out/sparc-debian2.2-linux/scanner/small.static
5 out/sparc-debian2.2-linux/scanner/small.dynamic
5 total |
See Sections for the illustrative description of a dumped ELF header.
Output: out/sparc-debian2.2-linux/scanner/entry_point/big.static
files=0002; detected=0000 |
Output: out/sparc-debian2.2-linux/scanner/entry_point/big.dynamic
files=0628; detected=0000 |
Well, on a clean system there are absolutely no deviations. Now we let the script oose on all infected executables produced from the sources of this document. Only a few are detected. Which means there is cure against this vulnerability (see The entry point). In the following output ep means "entry point" and sot is "start of .text".
Output: out/sparc-debian2.2-linux/scanner/entry_point/small.dynamic
segment_padding/e1i1/tcsh_infected ep=0x57500 sot=0x11d9c
segment_padding/e1i1/perl_infected ep=0x9fcd0 sot=0x1eed0
segment_padding/e1i1/mt_infected ep=0x14390 sot=0x10d78
segment_padding/e1i1/bash_infected ep=0x85770 sot=0x1f598
segment_padding/e1i1/strip_bash_infected ep=0x85770 sot=0x1f598
files=0005; detected=0005 |
Source: pre/sparc-debian2.2-linux/scanner/plain.sh
#!/bin/bash
src=$1
dst=$2
scanner=${3:-segment}
[ -s ${src} ] || exit 0
TEVWH_TMP=tmp/sparc-debian2.2-linux; export TEVWH_TMP
tmp/sparc-debian2.2-linux/scanner/${scanner} < ${src} 2>&1 \
| /usr/bin/tee ${dst}.full \
| /bin/grep -v ' Ok$' \
| /usr/bin/tail \
> ${dst} |
Note that only the last few lines of output are shown.
Output: out/sparc-debian2.2-linux/scanner/segment/big.static
CHECK: /usr/bin/ldd
CHECK: src/scanner/segment/action.inc#17
CHECK: (delta) > (0x10000)
CHECK: 65536 > 65536; 0x10000 > 0x10000
files=2; ok=2; det_page=0; det_align=1; min=0x10000; max=0x0000 |
Output: out/sparc-debian2.2-linux/scanner/segment/big.dynamic
CHECK: 65536 > 65536; 0x10000 > 0x10000
CHECK: /usr/lib/emacs/20.7/sparc-debian-linux-gnu/hexl
CHECK: src/scanner/segment/action.inc#17
CHECK: (delta) > (0x10000)
CHECK: 65536 > 65536; 0x10000 > 0x10000
CHECK: /usr/lib/postgresql/bin/postgres
CHECK: src/scanner/segment/action.inc#17
CHECK: (delta) > (0x10000)
CHECK: 65536 > 65536; 0x10000 > 0x10000
files=628; ok=628; det_page=0; det_align=59; min=0x10000; max=0x10005 |
On this installation at least 628 + 2 files are possible targets for Segment padding infection. So on to all infected executables created from the sources of this document. Again only the last few lines of output is shown. It's enough to see that all infected files are detected.
Output: out/sparc-debian2.2-linux/scanner/segment/small.dynamic
CHECK: 61441 > 65536; 0xf001 > 0x10000
CHECK: tmp/sparc-debian2.2-linux/segment_padding/e1i1/bash_infected
CHECK: src/scanner/segment/action.inc#17
CHECK: (delta) > (0x10000)
CHECK: 61445 > 65536; 0xf005 > 0x10000
CHECK: tmp/sparc-debian2.2-linux/segment_padding/e1i1/strip_bash_infected
CHECK: src/scanner/segment/action.inc#17
CHECK: (delta) > (0x10000)
CHECK: 61445 > 65536; 0xf005 > 0x10000
files=5; ok=5; det_page=0; det_align=5; min=0xf001; max=0xf005 |