http://bugzilla.opensuse.org/show_bug.cgi?id=1173396
Bug ID: 1173396
Summary: fonttosfnt writes nondeterministic .otb files from
ASLR
Classification: openSUSE
Product: openSUSE Tumbleweed
Version: Current
Hardware: x86-64
OS: openSUSE Factory
Status: NEW
Severity: Normal
Priority: P5 - None
Component: X.Org
Assignee: sndirsch@suse.com
Reporter: bwiedemann@suse.com
QA Contact: gfx-bugs@suse.de
CC: eich@suse.com
Blocks: 1061219
Found By: Development
Blocker: ---
While working on reproducible builds for openSUSE, I found that
when building the xorg-x11-fonts-converted package,
there were slight differences between each build
Steps to Reproduce:
fonttosfnt -b -c -g 2 -m 2 -o Adobe-Courier-Bold-Oblique.otb
/usr/share/fonts/75dpi/courBO08-ISO8859-1.pcf.gz ; md5sum
Adobe-Courier-Bold-Oblique.otb
filterdiff 'hexdump -C' {a,b}.otb
00000040 e3 43 7d a3 00 00 0a f0 00 00 00 36 63 6d 61 70 |.C}........6cmap|
00000050 00 ee 01 48 00 00 0b 28 00 00 00 3c 67 6c 79 66 |...H...(......d...6hhea|
00000080 10 69 05 40 00 00 0b 9c 00 00 00 24 68 6d 74 78 |.i.@.......$hmtx|
00000090 1c a0 fe 21 00 00 0b c0 00 00 03 00 6c 6f 63 61 |...!........loca|
000000a0 00 00 00 00 00 00 0e c0 00 00 01 82 6d 61 78 70 |............maxp|
@@ -180,9 +180,9 @@
00000b30 00 00 00 0c 00 04 00 30 00 00 00 08 00 04 00 02 |.......0........|
00000b40 00 04 00 00 00 7e 00 ff ff ff 00 00 00 00 00 20 |.....~......... |
00000b50 00 a0 ff ff 00 00 ff e1 ff c0 00 01 00 00 00 00 |................|
-00000b60 00 00 00 00 00 01 00 00 00 01 00 00 bd 55 7b 6c |.............U{l|
-00000b70 5f 0f 3c f5 00 01 08 00 00 00 0b 64 04 d1 29 50 |_.<........d..)P|
-00000b80 00 00 0b 64 04 d1 29 50 ff 00 ff 00 07 80 09 80 |...d..)P........|
+00000b60 00 00 00 00 00 01 00 00 00 01 00 00 70 82 c3 0c |............p...|
+00000b70 5f 0f 3c f5 00 01 08 00 00 00 0b 64 ab 3a 85 80 |_.<........d.:..|
+00000b80 00 00 0b 64 ab 3a 85 80 ff 00 ff 00 07 80 09 80 |...d.:..........|
00000b90 00 01 00 01 00 00 00 00 00 00 00 00 00 01 00 00 |................|
00000ba0 09 80 ff 00 00 66 06 80 ff 00 ff 00 07 80 00 01 |.....f..........|
The first chunk is just the checksum-adjustment
caused by diffs in the 2nd chunk.
I already tried to add a memset after all malloc and calloc calls,
but that did not make a difference.
https://github.com/bmwiedemann/theunreproduciblepackage/tree/master/aslr
has examples of how ASLR influenced outputs in the past.
Running fonttosfnt under setarch -R to disable ASLR does make the output
reproducible:
for i in $(seq 1 5) ; do
setarch -R fonttosfnt -b -c -g 2 -m 2 -o Adobe-Courier-Bold-Oblique.otb \
/usr/share/fonts/75dpi/courBO08-ISO8859-1.pcf.gz ;
md5sum Adobe-Courier-Bold-Oblique.otb ; done | sort | uniq -c
5 b320eb3a6f93fe19be575ad536fcba3e Adobe-Courier-Bold-Oblique.otb
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