bplist: teach the parser about unusual OffsetIntSize values #78
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Fixes DHowett#77. Notice that this is only a partial fix which works for the value of 3 and for any value < 8, but won't help in other cases. Supporting values < 16 should also be possible, but I didn't bother with it. Also this doesn't touch `bplist_generator` and hence won't make use of non-standard values for generating plists (while those values could probably give a benefit of slightly reduced plist size).
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WOW, excellent find! This might be annoying (and I am totally okay if you tell me "no" -- I'll happily do it myself), but would you be able to write a bplist deserialization test for this case? I quickly cross-referenced the behavior in CoreFoundation and it looks like offset int sizes that aren't powers of two are considered legal. Neat! |
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(Also, thanks so much!) |
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Okay, I got too excited about this and ended up writing a test bplist_test.gofunc TestBplistNonPowerOfTwoOffsetIntSizes(t *testing.T) {
bplist := []byte{
'b', 'p', 'l', 'i', 's', 't', '0', '0',
// Array (2 entries)
0xA2,
0x01, 0x02,
// 0xFFFFFFFFFFFFFF80 (MinInt8, sign extended)
0x13, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x80,
// 0x7F (MaxInt8)
0x10, 0x7f,
// Offset table (each entry is 3 bytes)
0x00, 0x00, 0x08,
0x00, 0x00, 0x0b,
0x00, 0x00, 0x14,
// Trailer
0x00, 0x00, 0x00, 0x00, 0x00,
0x00,
0x03, // Offset Int Size 3 (not a power of 2)
0x01,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x03,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x16,
}
buf := bytes.NewReader(bplist)
d := newBplistParser(buf)
_, err := d.parseDocument()
if err != nil {
t.Error("Unexpected error", err)
}
} |
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Thanks again for the fix! I added the test case from my most recent comment and squashed. |
chihqiang
pushed a commit
to pkg6/go-plist
that referenced
this pull request
May 20, 2025
This is only a partial fix which works for the value of 3 and for any value < 8, but won't help in other cases. Supporting values < 16 should also be possible, but I didn't bother with it. Also this doesn't touch `bplist_generator` and hence won't make use of non-standard values for generating plists (while those values could probably give a benefit of slightly reduced plist size). We confirmed that this is supported by the CoreFoundation bplist parser. Closes DHowett#77
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Fixes #77.
Notice that this is only a partial fix which works for the value of 3 and for any value < 8, but won't help in other cases. Supporting values < 16 should also be possible, but I didn't bother with it. Also this doesn't touch
bplist_generatorand hence won't make use of non-standard values for generating plists (while those values could probably give a benefit of slightly reduced plist size).