sys/src/9/port/random.c

   1 #include        "u.h"
   2 #include        "../port/lib.h"
   3 #include        "mem.h"
   4 #include        "dat.h"
   5 #include        "fns.h"
   6 #include        "../port/error.h"
   7
   8 #include        <libsec.h>
   9
  10 /* machine specific hardware random number generator */
  11 void (*hwrandbuf)(void*, ulong) = nil;
  12
  13 static struct
  14 {
  15         QLock;
  16         Chachastate;
  17 } *rs;
  18
  19 typedef struct Seedbuf Seedbuf;
  20 struct Seedbuf
  21 {
  22         ulong           randomcount;
  23         uchar           buf[64];
  24         uchar           nbuf;
  25         uchar           next;
  26         ushort          bits;
  27
  28         SHA2_512state   ds;
  29 };
  30
  31 static void
  32 randomsample(Ureg*, Timer *t)
  33 {
  34         Seedbuf *s = t->ta;
  35
  36         if(s->randomcount == 0 || s->nbuf >= sizeof(s->buf))
  37                 return;
  38         s->bits = (s->bits<<2) ^ s->randomcount;
  39         s->randomcount = 0;
  40         if(++s->next < 8/2)
  41                 return;
  42         s->next = 0;
  43         s->buf[s->nbuf++] ^= s->bits;
  44 }
  45
  46 static void
  47 randomseed(void*)
  48 {
  49         Seedbuf *s;
  50
  51         s = secalloc(sizeof(Seedbuf));
  52
  53         if(hwrandbuf != nil)
  54                 (*hwrandbuf)(s->buf, sizeof(s->buf));
  55
  56         /* Frequency close but not equal to HZ */
  57         up->tns = (vlong)(MS2HZ+3)*1000000LL;
  58         up->tmode = Tperiodic;
  59         up->tt = nil;
  60         up->ta = s;
  61         up->tf = randomsample;
  62         timeradd(up);
  63         while(s->nbuf < sizeof(s->buf)){
  64                 if(++s->randomcount <= 100000)
  65                         continue;
  66                 if(anyhigher())
  67                         sched();
  68         }
  69         timerdel(up);
  70
  71         sha2_512(s->buf, sizeof(s->buf), s->buf, &s->ds);
  72         setupChachastate(rs, s->buf, 32, s->buf+32, 12, 20);
  73         qunlock(rs);
  74
  75         secfree(s);
  76
  77         pexit("", 1);
  78 }
  79
  80 void
  81 randominit(void)
  82 {
  83         rs = secalloc(sizeof(*rs));
  84         qlock(rs);      /* randomseed() unlocks once seeded */
  85         kproc("randomseed", randomseed, nil);
  86 }
  87
  88 ulong
  89 randomread(void *p, ulong n)
  90 {
  91         Chachastate c;
  92         ulong b;
  93
  94         if(n == 0)
  95                 return 0;
  96
  97         if(hwrandbuf != nil)
  98                 (*hwrandbuf)(p, n);
  99
 100         /* copy chacha state and advance block counter */
 101         qlock(rs);
 102         c = *rs;
 103         b = rs->input[12];
 104         rs->input[12] += (n + ChachaBsize-1)/ChachaBsize;
 105         if(rs->input[12] < b) rs->input[13]++;
 106         qunlock(rs);
 107
 108         /* encrypt the buffer, can fault */
 109         chacha_encrypt((uchar*)p, n, &c);
 110
 111         /* prevent state leakage */
 112         memset(&c, 0, sizeof(c));
 113
 114         return n;
 115 }
 116
 117 /* used by fastrand() */
 118 void
 119 genrandom(uchar *p, int n)
 120 {
 121         randomread(p, n);
 122 }