git.distorted.org.uk Git - u/mdw/putty/blob - unix/uxnoise.c

   1 /*
   2  * Noise generation for PuTTY's cryptographic random number
   3  * generator.
   4  */
   5
   6 #include <stdio.h>
   7 #include <fcntl.h>
   8 #include <unistd.h>
   9 #include <sys/time.h>
  10
  11 #include "putty.h"
  12 #include "ssh.h"
  13 #include "storage.h"
  14
  15 /*
  16  * FIXME. This module currently depends critically on /dev/urandom,
  17  * because it has no fallback mechanism for doing anything else.
  18  */
  19
  20 static void read_dev_urandom(char *buf, int len)
  21 {
  22     int fd;
  23     int ngot, ret;
  24
  25     fd = open("/dev/urandom", O_RDONLY);
  26     if (fd < 0) {
  27         perror("/dev/urandom: open");
  28         exit(1);
  29     }
  30
  31     ngot = 0;
  32     while (ngot < len) {
  33         ret = read(fd, buf+ngot, len-ngot);
  34         if (ret < 0) {
  35             perror("/dev/urandom: read");
  36             exit(1);
  37         }
  38         ngot += ret;
  39     }
  40 }
  41
  42 /*
  43  * This function is called once, at PuTTY startup. Currently it
  44  * will read 32 bytes out of /dev/urandom and seed the internal
  45  * generator with them.
  46  */
  47
  48 void noise_get_heavy(void (*func) (void *, int))
  49 {
  50     char buf[32];
  51     read_dev_urandom(buf, sizeof(buf));
  52     func(buf, sizeof(buf));
  53 }
  54
  55 void random_save_seed(void)
  56 {
  57     /* Currently we do nothing here. FIXME? */
  58 }
  59
  60 /*
  61  * This function is called every time the urandom pool needs
  62  * stirring, and will acquire the system time.
  63  */
  64 void noise_get_light(void (*func) (void *, int))
  65 {
  66     struct timeval tv;
  67     gettimeofday(&tv, NULL);
  68     func(&tv, sizeof(tv));
  69 }
  70
  71 /*
  72  * This function is called on a timer, and it will just pull some
  73  * stuff out of /dev/urandom. FIXME: really I suspect we ought not
  74  * to deplete /dev/urandom like this. Better to grab something more
  75  * harmless.
  76  */
  77 void noise_regular(void)
  78 {
  79     char buf[4];
  80     read_dev_urandom(buf, sizeof(buf));
  81     random_add_noise(buf, sizeof(buf));
  82 }
  83
  84 /*
  85  * This function is called on every keypress or mouse move, and
  86  * will add the current time to the noise pool. It gets the scan
  87  * code or mouse position passed in, and adds that too.
  88  */
  89 void noise_ultralight(unsigned long data)
  90 {
  91     struct timeval tv;
  92     gettimeofday(&tv, NULL);
  93     random_add_noise(&tv, sizeof(tv));
  94     random_add_noise(&data, sizeof(data));
  95 }