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<div class="moz-cite-prefix">Hi Max et al -<br>
<br>
In general, I'm not a big fan of silent failover in security
stuff. There ought to be a way - perhaps a system property - to
signal that if you don't get the originally desired entropy
source, you'll throw an error.<br>
<br>
Also, have you considered: <b><br>
<br>
<a class="moz-txt-link-freetext" href="https://software.intel.com/en-us/articles/intel-digital-random-number-generator-drng-software-implementation-guide?language=fr">https://software.intel.com/en-us/articles/intel-digital-random-number-generator-drng-software-implementation-guide?language=fr</a><br>
<br>
</b>If you're going into the raw libraries, it might actually be a
better idea to go straight to the chipset if RDSEED is available.<br>
<br>
(Hmm... also
<a class="moz-txt-link-freetext" href="http://stackoverflow.com/questions/29372893/rdrand-and-rdseed-intrinsics-gcc-and-intel-c">http://stackoverflow.com/questions/29372893/rdrand-and-rdseed-intrinsics-gcc-and-intel-c</a>)<br>
<br>
Mike<br>
<br>
<br>
On 11/8/2015 6:18 AM, Dmitry Samersoff wrote:<br>
</div>
<blockquote cite="mid:563F2F85.50706@oracle.com" type="cite">
<pre wrap="">Wang Weijun,
</pre>
<blockquote type="cite">
<pre wrap="">The function is rather new in the latest Solaris beta [1] and it's
preferred to reading from /dev/random. There are already people
suggest adding it to Linux. If I use simply using dlsym then it will
automatically work on all current and future platforms. In fact, I
was planning to write
</pre>
</blockquote>
<pre wrap="">
1. Please, check libc only not entire process image.
2. OS X random system is a different story: /dev/random never blocks and
returns the output of Yarrow PRNG. Also OS X uses SecurityServer
process to feed entropy pool.
So IMHO, it's better to don't attempt to use other functions on OS X
until it appears officially.
3. Please notice that:
/dev/random will block if you request more bits than entropy pool can
provide.
but (according to manual page) getentropy will return immediately
with error if less that requested bytes of entropy is available and you
can't request more than 256 bytes of entropy at once.
it might require changes in uplevel logic.
-Dmitry
On 2015-11-08 03:37, Wang Weijun wrote:
</pre>
<blockquote type="cite">
<pre wrap="">
</pre>
<blockquote type="cite">
<pre wrap="">On Nov 8, 2015, at 4:29 AM, Dmitry Samersoff
<a class="moz-txt-link-rfc2396E" href="mailto:dmitry.samersoff@oracle.com"><dmitry.samersoff@oracle.com></a> wrote:
Wang Weijun,
1. RTLD_DEFAUL call is expensive and dangerous because it cause
symbol search across all loaded images. So it can pick up something
absolutely irrelevant to your expectations at any time.
If you decide to play to this game, you have to use dladdr to check
the origin of a symbol and try to guess whether it is what you are
looking for or not.
Please dlopen(libSystem.dylib, RTLD_NOW) and search through it
only.
2. You shouldn't rely on return value of dlopen() or dlsym(). Call
dlerror() and check whether it returns error or NULL.
</pre>
</blockquote>
<pre wrap="">
I'll try.
</pre>
<blockquote type="cite">
<pre wrap="">
PS: What is the goal of using a get entropy ?
</pre>
</blockquote>
<pre wrap="">
The function is rather new in the latest Solaris beta [1] and it's
preferred to reading from /dev/random. There are already people
suggest adding it to Linux. If I use simply using dlsym then it will
automatically work on all current and future platforms. In fact, I
was planning to write
getentropy = (GETENTROPY_FN)dlsym(RTLD_DEFAULT, "getentropy"); if
(getentropy) { return 1; } else { getrandom =
(GETRANDOM_FN)dlsym(RTLD_DEFAULT, "getrandom"); if (getrandom) {
return 2; } else { return -1; // will read /dev/random } }
Thanks Max
[1]
<a class="moz-txt-link-freetext" href="https://blogs.oracle.com/darren/entry/solaris_new_system_calls_getentropy">https://blogs.oracle.com/darren/entry/solaris_new_system_calls_getentropy</a>
</pre>
<blockquote type="cite">
<pre wrap="">
-Dmitry
On 2015-11-07 05:51, Wang Weijun wrote:
</pre>
<blockquote type="cite">
<pre wrap="">I find something strange.
Background: a new method getentropy() is available on OpenBSD [1]
and Solaris and people are also proposing it on other OSes.
Therefore inside JDK I write a piece of native code to detect it,
something like
typedef int (*GETENTROPY_FN)(char* buffer, int len);
getentropy = (GETENTROPY_FN)dlsym(RTLD_DEFAULT, "getentropy"); if
(getentropy) { return 1; }
On Mac, it returns non-NULL, but a later call to
(*getentropy)(cbuffer, length) shows
# SIGBUS (0xa) at pc=0x0000000103bfa030, pid=22434, tid=5891
... # Problematic frame: # C [libj2rand.dylib+0x1030]
getentropy+0x0
However, "man getentropy" does not show anything, and the
following simple program also prints out 0x0
#include <dlfcn.h> #include <stdlib.h>
main() { void* g = dlsym(RTLD_DEFAULT, "getentropy");
printf("%p\n", g); }
What does this mean? Is the JDK code loading another getentropy()
somewhere else? How do I detect it and what shall I do to avoid
it?
Thanks Max
[1]
<a class="moz-txt-link-freetext" href="http://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man2/getentropy.2">http://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man2/getentropy.2</a>
</pre>
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</pre>
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<pre wrap="">
</pre>
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