2 * cryptographic random number generator for PuTTY's ssh client
7 void noise_get_heavy(void (*func
) (void *, int));
8 void noise_get_light(void (*func
) (void *, int));
11 * `pool' itself is a pool of random data which we actually use: we
12 * return bytes from `pool', at position `poolpos', until `poolpos'
13 * reaches the end of the pool. At this point we generate more
14 * random data, by adding noise, stirring well, and resetting
15 * `poolpos' to point to just past the beginning of the pool (not
16 * _the_ beginning, since otherwise we'd give away the whole
17 * contents of our pool, and attackers would just have to guess the
20 * `incomingb' buffers acquired noise data, until it gets full, at
21 * which point the acquired noise is SHA'ed into `incoming' and
22 * `incomingb' is cleared. The noise in `incoming' is used as part
23 * of the noise for each stirring of the pool, in addition to local
24 * time, process listings, and other such stuff.
27 #define HASHINPUT 64 /* 64 bytes SHA input */
28 #define HASHSIZE 20 /* 160 bits SHA output */
29 #define POOLSIZE 1200 /* size of random pool */
32 unsigned char pool
[POOLSIZE
];
35 unsigned char incoming
[HASHSIZE
];
37 unsigned char incomingb
[HASHINPUT
];
41 static struct RandPool pool
;
42 static int random_active
= 0;
44 void random_stir(void) {
45 word32 block
[HASHINPUT
/sizeof(word32
)];
46 word32 digest
[HASHSIZE
/sizeof(word32
)];
49 noise_get_light(random_add_noise
);
51 SHATransform((word32
*)pool
.incoming
, (word32
*)pool
.incomingb
);
55 * Chunks of this code are blatantly endianness-dependent, but
56 * as it's all random bits anyway, WHO CARES?
58 memcpy(digest
, pool
.incoming
, sizeof(digest
));
61 * Make two passes over the pool.
63 for (i
= 0; i
< 2; i
++) {
66 * We operate SHA in CFB mode, repeatedly adding the same
67 * block of data to the digest. But we're also fiddling
68 * with the digest-so-far, so this shouldn't be Bad or
71 memcpy(block
, pool
.pool
, sizeof(block
));
74 * Each pass processes the pool backwards in blocks of
75 * HASHSIZE, just so that in general we get the output of
76 * SHA before the corresponding input, in the hope that
77 * things will be that much less predictable that way
78 * round, when we subsequently return bytes ...
80 for (j
= POOLSIZE
; (j
-= HASHSIZE
) >= 0 ;) {
82 * XOR the bit of the pool we're processing into the
86 for (k
= 0; k
< sizeof(digest
)/sizeof(*digest
); k
++)
87 digest
[k
] ^= ((word32
*)(pool
.pool
+j
))[k
];
90 * Munge our unrevealed first block of the pool into
93 SHATransform(digest
, block
);
96 * Stick the result back into the pool.
99 for (k
= 0; k
< sizeof(digest
)/sizeof(*digest
); k
++)
100 ((word32
*)(pool
.pool
+j
))[k
] = digest
[k
];
105 * Might as well save this value back into `incoming', just so
106 * there'll be some extra bizarreness there.
108 SHATransform(digest
, block
);
109 memcpy(pool
.incoming
, digest
, sizeof(digest
));
111 pool
.poolpos
= sizeof(pool
.incoming
);
114 void random_add_noise(void *noise
, int length
) {
115 unsigned char *p
= noise
;
122 * This function processes HASHINPUT bytes into only HASHSIZE
123 * bytes, so _if_ we were getting incredibly high entropy
124 * sources then we would be throwing away valuable stuff.
126 while (length
>= (HASHINPUT
- pool
.incomingpos
)) {
127 memcpy(pool
.incomingb
+ pool
.incomingpos
, p
,
128 HASHINPUT
- pool
.incomingpos
);
129 p
+= HASHINPUT
- pool
.incomingpos
;
130 length
-= HASHINPUT
- pool
.incomingpos
;
131 SHATransform((word32
*)pool
.incoming
, (word32
*)pool
.incomingb
);
132 for (i
= 0; i
< HASHSIZE
; i
++) {
133 pool
.pool
[pool
.poolpos
++] ^= pool
.incomingb
[i
];
134 if (pool
.poolpos
>= POOLSIZE
)
137 if (pool
.poolpos
< HASHSIZE
)
140 pool
.incomingpos
= 0;
143 memcpy(pool
.incomingb
+ pool
.incomingpos
, p
, length
);
144 pool
.incomingpos
+= length
;
147 void random_add_heavynoise(void *noise
, int length
) {
148 unsigned char *p
= noise
;
151 while (length
>= POOLSIZE
) {
152 for (i
= 0; i
< POOLSIZE
; i
++)
153 pool
.pool
[i
] ^= *p
++;
158 for (i
= 0; i
< length
; i
++)
159 pool
.pool
[i
] ^= *p
++;
163 static void random_add_heavynoise_bitbybit(void *noise
, int length
) {
164 unsigned char *p
= noise
;
167 while (length
>= POOLSIZE
- pool
.poolpos
) {
168 for (i
= 0; i
< POOLSIZE
- pool
.poolpos
; i
++)
169 pool
.pool
[pool
.poolpos
+ i
] ^= *p
++;
171 length
-= POOLSIZE
- pool
.poolpos
;
175 for (i
= 0; i
< length
; i
++)
176 pool
.pool
[i
] ^= *p
++;
180 void random_init(void) {
181 memset(&pool
, 0, sizeof(pool
)); /* just to start with */
185 noise_get_heavy(random_add_heavynoise_bitbybit
);
189 int random_byte(void) {
190 if (pool
.poolpos
>= POOLSIZE
)
193 return pool
.pool
[pool
.poolpos
++];
196 void random_get_savedata(void **data
, int *len
) {
198 *data
= pool
.pool
+pool
.poolpos
;