Date: Tue, 22 Aug 2017 23:32:52 +0200 From: Solar Designer <solar@...nwall.com> To: announce@...ts.openwall.com Subject: [openwall-announce] php_mt_seed 4.0 adds PHP 7.1.0+ and 5.2.0- support Hi, php_mt_seed is a PHP mt_rand() seed cracker. A couple of weeks ago, I announced php_mt_seed 3.3, which expanded support for SIMD instruction sets from the previous range of SSE4.1 to AVX2/MIC to also include SSE2 on the lower end and AVX-512 on the high end: http://www.openwall.com/lists/announce/2017/08/06/1 Now I announce php_mt_seed 4.0, which expands the range of supported PHP versions from the previous 5.2.1 to 7.0.x to also include 3.0.7 to 5.2.0 on the legacy side and 7.1.0+ to current latest (7.2.0beta3 as of this writing) and hopefully beyond on the modern side. The new php_mt_seed 4.0 is downloadable at the usual location: http://www.openwall.com/php_mt_seed/ php_mt_seed 4.0 automatically checks for seeds for the 3 major revisions of PHP's mt_rand() algorithm. First it searches for seeds for the legacy PHP 3.0.7 to 5.2.0, which it typically completes in a fraction of a second. Then it proceeds to search for seeds for PHP 5.2.1 to 7.0.x and for PHP 7.1.0+ simultaneously, which takes a while. Curiously, in the simplest cases (such as when searching for seeds for the very first mt_rand() output after seeding) there's essentially no slowdown from supporting those 3 PHP version ranges at once. That's because the attack on legacy PHP 3.0.7 to 5.2.0 is so quick (due to precomputation of 69069 raised to the power 396 (mod 2**32), for the curious), and the attack on PHP 5.2.1+ has most of its processing common with the attack on PHP 7.1.0+. In more complex cases, the 3 algorithms deviate to a greater extent, so significant slowdown may be seen. In a future version of php_mt_seed, I might add a way to specify which PHP version(s) to target, but meanwhile php_mt_seed only outputs which PHP versions the found seeds are for, like this (on dual E5-2670 v1): $ time ./php_mt_seed 1871584565 Pattern: EXACT Version: 3.0.7 to 5.2.0 Found 0, trying 0x48000000 - 0x4bffffff, speed 24159.2 Mseeds/s seed = 0x4be01ac0 = 1272978112 (PHP 3.0.7 to 5.2.0) seed = 0x4be01ac1 = 1272978113 (PHP 3.0.7 to 5.2.0) Found 2, trying 0x5c000000 - 0x5fffffff, speed 25725.1 Mseeds/s seed = 0x5fe49e4e = 1608818254 (PHP 3.0.7 to 5.2.0) seed = 0x5fe49e4f = 1608818255 (PHP 3.0.7 to 5.2.0) Found 4, trying 0xfc000000 - 0xffffffff, speed 28185.7 Mseeds/s Version: 5.2.1+ Found 4, trying 0x86000000 - 0x87ffffff, speed 234.4 Mseeds/s seed = 0x86d2e002 = 2261966850 (PHP 7.1.0+) Found 5, trying 0xc2000000 - 0xc3ffffff, speed 234.5 Mseeds/s seed = 0xc24768d7 = 3259459799 (PHP 5.2.1 to 7.0.x; HHVM) seed = 0xc24768d7 = 3259459799 (PHP 7.1.0+) Found 7, trying 0xc6000000 - 0xc7ffffff, speed 234.4 Mseeds/s seed = 0xc6d8b812 = 3336091666 (PHP 5.2.1 to 7.0.x; HHVM) seed = 0xc6d8b812 = 3336091666 (PHP 7.1.0+) Found 9, trying 0xfe000000 - 0xffffffff, speed 234.5 Mseeds/s Found 9 real 0m18.478s user 9m48.751s sys 0m0.015s Besides the addition of support for more PHP versions, I've also cleaned up the code (so that the source file size increased only from 18 KB to 19 KB, despite of the major added functionality) and rewrote new/real documentation (the README file is now up to 29 KB, so larger than the source code). Like before, README is also viewable on the web, with HTML formatting: http://www.openwall.com/php_mt_seed/README Its table of contents is: What is php_mt_seed? Why crack mt_rand() seeds? How to build php_mt_seed How to use php_mt_seed Command-line syntax Complex usage example When extra tools or php_mt_seed changes are needed Xeon Phi specifics PHP version curiosities (mostly unimportant) Contact info The section on "PHP version curiosities" is quite lengthy and describes the history of PHP's mt_rand() since its introduction in PHP 3.0.6 to present day and even beyond, talking about two current bugs that are likely to get fixed. I discovered and reported one of those bugs during work on this version of php_mt_seed, and a PHP developer discovered the other while proposing a fix for the bug I reported. Finally, I've added to the php_mt_seed homepage many links to external web pages illustrating usage of php_mt_seed (including CTF writeups) and, separately, to other relevant external web pages and projects, which together cover PRNG seed cracking way beyond PHP's mt_rand() and provide a historical background. This took quite some effort, and I hope some of you find it useful. Alexander
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