2 * cryptographic random number generator for PuTTY's ssh client
8 void noise_get_heavy(void (*func
) (void *, int));
9 void noise_get_light(void (*func
) (void *, int));
12 * `pool' itself is a pool of random data which we actually use: we
13 * return bytes from `pool', at position `poolpos', until `poolpos'
14 * reaches the end of the pool. At this point we generate more
15 * random data, by adding noise, stirring well, and resetting
16 * `poolpos' to point to just past the beginning of the pool (not
17 * _the_ beginning, since otherwise we'd give away the whole
18 * contents of our pool, and attackers would just have to guess the
21 * `incomingb' buffers acquired noise data, until it gets full, at
22 * which point the acquired noise is SHA'ed into `incoming' and
23 * `incomingb' is cleared. The noise in `incoming' is used as part
24 * of the noise for each stirring of the pool, in addition to local
25 * time, process listings, and other such stuff.
28 #define HASHINPUT 64 /* 64 bytes SHA input */
29 #define HASHSIZE 20 /* 160 bits SHA output */
30 #define POOLSIZE 1200 /* size of random pool */
33 unsigned char pool
[POOLSIZE
];
36 unsigned char incoming
[HASHSIZE
];
38 unsigned char incomingb
[HASHINPUT
];
42 static struct RandPool pool
;
43 int random_active
= 0;
45 static void random_stir(void)
47 word32 block
[HASHINPUT
/ sizeof(word32
)];
48 word32 digest
[HASHSIZE
/ sizeof(word32
)];
51 noise_get_light(random_add_noise
);
53 SHATransform((word32
*) pool
.incoming
, (word32
*) pool
.incomingb
);
57 * Chunks of this code are blatantly endianness-dependent, but
58 * as it's all random bits anyway, WHO CARES?
60 memcpy(digest
, pool
.incoming
, sizeof(digest
));
63 * Make two passes over the pool.
65 for (i
= 0; i
< 2; i
++) {
68 * We operate SHA in CFB mode, repeatedly adding the same
69 * block of data to the digest. But we're also fiddling
70 * with the digest-so-far, so this shouldn't be Bad or
73 memcpy(block
, pool
.pool
, sizeof(block
));
76 * Each pass processes the pool backwards in blocks of
77 * HASHSIZE, just so that in general we get the output of
78 * SHA before the corresponding input, in the hope that
79 * things will be that much less predictable that way
80 * round, when we subsequently return bytes ...
82 for (j
= POOLSIZE
; (j
-= HASHSIZE
) >= 0;) {
84 * XOR the bit of the pool we're processing into the
88 for (k
= 0; k
< sizeof(digest
) / sizeof(*digest
); k
++)
89 digest
[k
] ^= ((word32
*) (pool
.pool
+ j
))[k
];
92 * Munge our unrevealed first block of the pool into
95 SHATransform(digest
, block
);
98 * Stick the result back into the pool.
101 for (k
= 0; k
< sizeof(digest
) / sizeof(*digest
); k
++)
102 ((word32
*) (pool
.pool
+ j
))[k
] = digest
[k
];
107 * Might as well save this value back into `incoming', just so
108 * there'll be some extra bizarreness there.
110 SHATransform(digest
, block
);
111 memcpy(pool
.incoming
, digest
, sizeof(digest
));
113 pool
.poolpos
= sizeof(pool
.incoming
);
116 void random_add_noise(void *noise
, int length
)
118 unsigned char *p
= noise
;
125 * This function processes HASHINPUT bytes into only HASHSIZE
126 * bytes, so _if_ we were getting incredibly high entropy
127 * sources then we would be throwing away valuable stuff.
129 while (length
>= (HASHINPUT
- pool
.incomingpos
)) {
130 memcpy(pool
.incomingb
+ pool
.incomingpos
, p
,
131 HASHINPUT
- pool
.incomingpos
);
132 p
+= HASHINPUT
- pool
.incomingpos
;
133 length
-= HASHINPUT
- pool
.incomingpos
;
134 SHATransform((word32
*) pool
.incoming
, (word32
*) pool
.incomingb
);
135 for (i
= 0; i
< HASHSIZE
; i
++) {
136 pool
.pool
[pool
.poolpos
++] ^= pool
.incomingb
[i
];
137 if (pool
.poolpos
>= POOLSIZE
)
140 if (pool
.poolpos
< HASHSIZE
)
143 pool
.incomingpos
= 0;
146 memcpy(pool
.incomingb
+ pool
.incomingpos
, p
, length
);
147 pool
.incomingpos
+= length
;
150 void random_add_heavynoise(void *noise
, int length
)
152 unsigned char *p
= noise
;
155 while (length
>= POOLSIZE
) {
156 for (i
= 0; i
< POOLSIZE
; i
++)
157 pool
.pool
[i
] ^= *p
++;
162 for (i
= 0; i
< length
; i
++)
163 pool
.pool
[i
] ^= *p
++;
167 static void random_add_heavynoise_bitbybit(void *noise
, int length
)
169 unsigned char *p
= noise
;
172 while (length
>= POOLSIZE
- pool
.poolpos
) {
173 for (i
= 0; i
< POOLSIZE
- pool
.poolpos
; i
++)
174 pool
.pool
[pool
.poolpos
+ i
] ^= *p
++;
176 length
-= POOLSIZE
- pool
.poolpos
;
180 for (i
= 0; i
< length
; i
++)
181 pool
.pool
[i
] ^= *p
++;
185 void random_init(void)
187 memset(&pool
, 0, sizeof(pool
)); /* just to start with */
191 noise_get_heavy(random_add_heavynoise_bitbybit
);
195 int random_byte(void)
197 if (pool
.poolpos
>= POOLSIZE
)
200 return pool
.pool
[pool
.poolpos
++];
203 void random_get_savedata(void **data
, int *len
)
205 void *buf
= snewn(POOLSIZE
/ 2, char);
207 memcpy(buf
, pool
.pool
+ pool
.poolpos
, POOLSIZE
/ 2);