Bug 101501 - Reading outside bounds at Functions.cc:218
Summary: Reading outside bounds at Functions.cc:218
Alias: None
Product: poppler
Classification: Unclassified
Component: general (show other bugs)
Version: unspecified
Hardware: All All
: medium normal
Assignee: poppler-bugs
QA Contact:
Depends on:
Reported: 2017-06-19 17:32 UTC by foca@salesforce.com
Modified: 2018-08-20 21:35 UTC (History)
0 users

See Also:
i915 platform:
i915 features:

Proof of concept (2.17 KB, application/pdf)
2017-06-19 17:32 UTC, foca@salesforce.com

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Description foca@salesforce.com 2017-06-19 17:32:51 UTC
Created attachment 132065 [details]
Proof of concept

There is a bug reading outside bounds at Functions.cc:218

 212 }
 214 void IdentityFunction::transform(double *in, double *out) {
 215   int i;
 217   for (i = 0; i < funcMaxOutputs; ++i) {
 218     out[i] = in[i];
 219   }
 220 }

funcMacOutputs is defined in Functions.h:
#define funcMaxOutputs       32

Parsing the PoC.pdf, this function is called from GfxFunctionShading::getColor:

3957 void GfxFunctionShading::getColor(double x, double y, GfxColor *color) {
3958   double in[2], out[gfxColorMaxComps];
3959   int i;
3961   // NB: there can be one function with n outputs or n functions with
3962   // one output each (where n = number of color components)
3963   for (i = 0; i < gfxColorMaxComps; ++i) {
3964     out[i] = 0;
3965   }
3966   in[0] = x;
3967   in[1] = y;
3968   for (i = 0; i < nFuncs; ++i) {
3969     funcs[i]->transform(in, &out[i]);
3970   }
3971   for (i = 0; i < gfxColorMaxComps; ++i) {
3972     color->c[i] = dblToCol(out[i]);
3973   }
3974 }

Where the variable in has only 2 elements, instead of the 32 read at IdentityFunction::transform. So 30 elements are read after the in.

This could be fixed increasing the number of elements for the variable in:
3958   double in[gfxColorMaxComps], out[gfxColorMaxComps];

PoC is attached.

This vulnerability has been found by Offensive Research at Salesforce.com:
Alberto Garcia (@algillera), Francisco Oca (@francisco_oca) & Suleman Ali (@Salbei_)
Comment 1 Albert Astals Cid 2017-06-19 21:23:11 UTC
Nor valgrind nor asan find anynthing wrong in that file.

Which tool are you using?
Comment 2 foca@salesforce.com 2017-06-19 21:34:14 UTC
I'm using ASAN.

Sorry I didn't provide the command line, I used this:
pdftocairo -svg PoC.pdf

If still ASAN is not detecting it, try to put a breakpoint at Function.cc:218 and see how the variable in is accessed beyond the second element.
Comment 3 Albert Astals Cid 2017-06-19 21:53:12 UTC
yeah, the getColor functions are a bit evil, your suggested solution won't fix the problem in that function, out may need to go to gfxColorMaxComps * 2 too, i'd like to avoid that though
Comment 4 GitLab Migration User 2018-08-20 21:35:54 UTC
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