[cmake-developers] [PATCH] Fix infinite loop in file downloads if hash value not a match

[Alan W. Irwin]

I was caught by this infinite loop issue when attempting to build
Qt5.3.1 using ExternalProject.cmake.  I used an MD5 sum value given by
BLFS for the Qt5.3.1 tar.gz download which happened to be the wrong
value.  In my case the consequences were not too bad because I
was "downloading" from a local disk drive "URL".  However, this
infinite loop could be construed as a denial-of-service attack
on some open-source project if an actual download keeps getting
repeated indefinitely.  Note this bad retries logic in the downloads
was introduced after CMake-2.8.12.2, and a search of the bug tracker
for "infinite" shows nothing relevant.

See attached patch in "git format-patch" form that fixes the problem
for the CMake master branch.

Alan
__________________________
Alan W. Irwin

Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).

Programming affiliations with the FreeEOS equation-of-state
implementation for stellar interiors (freeeos.sf.net); the Time
Ephemerides project (timeephem.sf.net); PLplot scientific plotting
software package (plplot.sf.net); the libLASi project
(unifont.org/lasi); the Loads of Linux Links project (loll.sf.net);
and the Linux Brochure Project (lbproject.sf.net).
__________________________

Linux-powered Science
__________________________
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