MantisBT - CMake
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ID	Project	Category	View Status	Date Submitted	Last Update
0015976	CMake	CMake	public	2016-02-16 20:26	2016-06-10 14:21

Reporter	Cristian Rodríguez
Assigned To	Brad King
Priority	normal	Severity	minor	Reproducibility	always
Status	closed	Resolution	fixed
Platform	linux	OS	linux	OS Version	any
Product Version	CMake 3.4.3
Target Version	CMake 3.6	Fixed in Version	CMake 3.6

Summary	0015976: cmSystemTools::RandomSeed() requests excessive entropy per invocation
Description	cmSystemTools::RandomSeed() opens a buffered ifstream, the final result is that each invocation requests _IO_BUFSIZ -1 of entropy to the operating system instead of just sizeof(seed)
Steps To Reproduce	mkdir test_cmake echo "PROJECT(foo)" > CMakeLists.txt cd test_cmake strace -f -ocmake.trace cmake . open cmake.trace 10768 26289 open("/dev/urandom", O_RDONLY) = 4 10769 26289 read(4, "h\304j\vx\314\26\0042\250g\275\0014,\256\251\257T&\304\212\310\347q\201\263\324\330\273z8"..., 8191) = 8191 10770 26289 close(4) = 0 10771 26289 write(3, "cmake_minimum_required(VERSION 3"..., 795) = 795 10772 26289 close(3) = 0 10773 26289 stat("/home/crrodriguez/test_cmake/CMakeFiles/CMakeTmp", {st_mode=S_IFDIR\|0755, st_size=58, ...}) = 0 10774 26289 getcwd("/home/crrodriguez/test_cmake", 2048) = 29
Additional Information	git diff diff --git a/Source/cmSystemTools.cxx b/Source/cmSystemTools.cxx index 3ba7287..26bec34 100644 --- a/Source/cmSystemTools.cxx +++ b/Source/cmSystemTools.cxx @@ -2184,8 +2184,10 @@ unsigned int cmSystemTools::RandomSeed() } seed; // Try using a real random source. - cmsys::ifstream fin("/dev/urandom"); - if(fin && fin.read(seed.bytes, sizeof(seed)) && + cmsys::ifstream fin; + fin.rdbuf()->pubsetbuf(0, 0); + fin.open("/dev/urandom"); + if(fin.good() && fin.read(seed.bytes, sizeof(seed)) && fin.gcount() == sizeof(seed)) { return seed.integer;
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Issue History
Date Modified	Username	Field	Change
2016-02-16 20:26	Cristian Rodríguez	New Issue
2016-02-17 09:05	Brad King	Note Added: 0040496
2016-02-17 09:05	Brad King	Assigned To	=> Brad King
2016-02-17 09:05	Brad King	Status	new => resolved
2016-02-17 09:05	Brad King	Resolution	open => fixed
2016-02-17 09:05	Brad King	Fixed in Version	=> CMake 3.6
2016-02-17 09:05	Brad King	Target Version	=> CMake 3.6
2016-02-19 09:45	Brad King	Note Edited: 0040496	bug_revision_view_page.php?bugnote_id=40496#r2029
2016-06-10 14:21	Kitware Robot	Note Added: 0041244
2016-06-10 14:21	Kitware Robot	Status	resolved => closed

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