Re: Automatically seeding rand() and mt_rand()

On Sun, 7 Oct 2001 mlwmohawk@mohawksoft.com wrote: > I have posted this before, but I will try again. > > We have once again seen people do silly stuff like this: > > srand ((double) microtime() * 1000000); > $new_id = md5(rand()); > session_id($new_id); > > It occurs to me that it is useless to have a rand() function in PHP that > is not automatically seeded. The rand() function is useless without a > fairly unique seed, and it is fairly difficult to get a good seed from > within PHP. Then you have to add more PHP code to test whether or not you > have seeded in a previous script. > > If, in ext/standard/rand.c one were to add a global variable: "rand_seed" > set to zero. In the function php_srand, keep it updated, and in php_rand > check if it is zero, if so call php_srand() with the results from: > GENERATE_SEED(); to update the random seed. A great deal of programming > atrocities can be avoided, and rand() will, in fact, be more random. > > This is the patch I want to commit: > Its not ts... I'll commit something similiar in a few minutes (also taking care of mt_* seeding. -Sterling > --- oldrand.c Sun Oct 7 07:12:59 2001 > +++ rand.c Sun Oct 7 07:11:58 2001 > @@ -38,6 +38,7 @@ > > #include "basic_functions.h" > > +long rand_seed = 0; > > /* SYSTEM RAND FUNCTIONS */ > > @@ -45,6 +46,7 @@ > */ > PHPAPI void php_srand(long seed TSRMLS_DC) > { > + rand_seed = seed; > #ifdef ZTS > BG(rand_seed) = (unsigned int) seed; > #else > @@ -328,6 +330,10 @@ > if (argc != 0 && zend_parse_parameters(argc TSRMLS_CC, "ll", > &min, > &max) == FAILURE) > return; > > + if(rand_seed == 0) { > + long seed = GENERATE_SEED(); > + php_srand(seed TSRMLS_CC); > + } > number = php_rand(TSRMLS_C); > > if (argc == 2) { > > > > >