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28 lines
1.2 KiB
28 lines
1.2 KiB
5 years ago
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Protect against a fax VL(n) codeword commanding a move left. Without
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this, a malicious input file can generate an indefinitely large series
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of runs without a0 ever reaching the right margin, thus overrunning
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our buffer of run lengths. Per CVE-2011-0192. This is a modified
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version of a patch proposed by Drew Yao of Apple Product Security.
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It adds an unexpected() report, and disallows the equality case except
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for the first run of a line, since emitting a run without increasing a0
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still allows buffer overrun. (We have to allow it for the first run to
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cover the case of encoding a zero-length run at start of line using VL.)
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diff -Naur tiff-3.9.4.orig/libtiff/tif_fax3.h tiff-3.9.4/libtiff/tif_fax3.h
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--- tiff-3.9.4.orig/libtiff/tif_fax3.h 2010-06-08 14:50:42.000000000 -0400
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+++ tiff-3.9.4/libtiff/tif_fax3.h 2011-03-10 12:11:20.850839162 -0500
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@@ -478,6 +478,12 @@
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break; \
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case S_VL: \
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CHECK_b1; \
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+ if (b1 <= (int) (a0 + TabEnt->Param)) { \
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+ if (b1 < (int) (a0 + TabEnt->Param) || pa != thisrun) { \
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+ unexpected("VL", a0); \
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+ goto eol2d; \
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+ } \
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+ } \
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SETVALUE(b1 - a0 - TabEnt->Param); \
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b1 -= *--pb; \
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break; \
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