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c5895ec292
This is another cleanup I felt a need for while I was doing boolification. If you define a function or variable in one .c file and declare it extern in another, then nothing will check you haven't got the types of the two declarations mismatched - so when you're _changing_ the type, it's a pain to make sure you've caught all the copies of it. It's better to put all those extern declarations in header files, so that the declaration in the header is also in scope for the definition. Then the compiler will complain if they don't match, which is what I want.
342 lines
8.8 KiB
C
342 lines
8.8 KiB
C
/*
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* cryptographic random number generator for PuTTY's ssh client
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*/
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#include "putty.h"
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#include "ssh.h"
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#include <assert.h>
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/* Collect environmental noise every 5 minutes */
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#define NOISE_REGULAR_INTERVAL (5*60*TICKSPERSEC)
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/*
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* `pool' itself is a pool of random data which we actually use: we
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* return bytes from `pool', at position `poolpos', until `poolpos'
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* reaches the end of the pool. At this point we generate more
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* random data, by adding noise, stirring well, and resetting
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* `poolpos' to point to just past the beginning of the pool (not
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* _the_ beginning, since otherwise we'd give away the whole
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* contents of our pool, and attackers would just have to guess the
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* next lot of noise).
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*
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* `incomingb' buffers acquired noise data, until it gets full, at
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* which point the acquired noise is SHA'ed into `incoming' and
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* `incomingb' is cleared. The noise in `incoming' is used as part
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* of the noise for each stirring of the pool, in addition to local
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* time, process listings, and other such stuff.
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*/
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#define HASHINPUT 64 /* 64 bytes SHA input */
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#define HASHSIZE 20 /* 160 bits SHA output */
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#define POOLSIZE 1200 /* size of random pool */
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struct RandPool {
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unsigned char pool[POOLSIZE];
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int poolpos;
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unsigned char incoming[HASHSIZE];
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unsigned char incomingb[HASHINPUT];
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int incomingpos;
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bool stir_pending;
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};
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int random_active = 0;
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#ifdef FUZZING
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/*
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* Special dummy version of the RNG for use when fuzzing.
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*/
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void random_add_noise(void *noise, int length) { }
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void random_add_heavynoise(void *noise, int length) { }
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void random_ref(void) { }
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void random_unref(void) { }
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int random_byte(void)
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{
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return 0x45; /* Chosen by eight fair coin tosses */
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}
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void random_get_savedata(void **data, int *len) { }
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#else /* !FUZZING */
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static struct RandPool pool;
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long next_noise_collection;
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#ifdef RANDOM_DIAGNOSTICS
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int random_diagnostics = 0;
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#endif
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static void random_stir(void)
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{
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uint32_t block[HASHINPUT / sizeof(uint32_t)];
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uint32_t digest[HASHSIZE / sizeof(uint32_t)];
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int i, j, k;
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/*
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* noise_get_light will call random_add_noise, which may call
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* back to here. Prevent recursive stirs.
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*/
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if (pool.stir_pending)
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return;
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pool.stir_pending = true;
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noise_get_light(random_add_noise);
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#ifdef RANDOM_DIAGNOSTICS
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{
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int p, q;
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printf("random stir starting\npool:\n");
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for (p = 0; p < POOLSIZE; p += HASHSIZE) {
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printf(" ");
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for (q = 0; q < HASHSIZE; q += 4) {
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printf(" %08x", *(uint32_t *)(pool.pool + p + q));
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}
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printf("\n");
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}
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printf("incoming:\n ");
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for (q = 0; q < HASHSIZE; q += 4) {
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printf(" %08x", *(uint32_t *)(pool.incoming + q));
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}
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printf("\nincomingb:\n ");
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for (q = 0; q < HASHINPUT; q += 4) {
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printf(" %08x", *(uint32_t *)(pool.incomingb + q));
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}
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printf("\n");
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random_diagnostics++;
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}
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#endif
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SHATransform((uint32_t *) pool.incoming, (uint32_t *) pool.incomingb);
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pool.incomingpos = 0;
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/*
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* Chunks of this code are blatantly endianness-dependent, but
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* as it's all random bits anyway, WHO CARES?
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*/
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memcpy(digest, pool.incoming, sizeof(digest));
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/*
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* Make two passes over the pool.
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*/
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for (i = 0; i < 2; i++) {
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/*
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* We operate SHA in CFB mode, repeatedly adding the same
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* block of data to the digest. But we're also fiddling
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* with the digest-so-far, so this shouldn't be Bad or
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* anything.
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*/
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memcpy(block, pool.pool, sizeof(block));
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/*
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* Each pass processes the pool backwards in blocks of
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* HASHSIZE, just so that in general we get the output of
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* SHA before the corresponding input, in the hope that
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* things will be that much less predictable that way
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* round, when we subsequently return bytes ...
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*/
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for (j = POOLSIZE; (j -= HASHSIZE) >= 0;) {
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/*
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* XOR the bit of the pool we're processing into the
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* digest.
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*/
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for (k = 0; k < sizeof(digest) / sizeof(*digest); k++)
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digest[k] ^= ((uint32_t *) (pool.pool + j))[k];
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/*
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* Munge our unrevealed first block of the pool into
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* it.
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*/
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SHATransform(digest, block);
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/*
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* Stick the result back into the pool.
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*/
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for (k = 0; k < sizeof(digest) / sizeof(*digest); k++)
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((uint32_t *) (pool.pool + j))[k] = digest[k];
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}
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#ifdef RANDOM_DIAGNOSTICS
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if (i == 0) {
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int p, q;
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printf("random stir midpoint\npool:\n");
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for (p = 0; p < POOLSIZE; p += HASHSIZE) {
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printf(" ");
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for (q = 0; q < HASHSIZE; q += 4) {
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printf(" %08x", *(uint32_t *)(pool.pool + p + q));
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}
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printf("\n");
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}
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printf("incoming:\n ");
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for (q = 0; q < HASHSIZE; q += 4) {
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printf(" %08x", *(uint32_t *)(pool.incoming + q));
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}
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printf("\nincomingb:\n ");
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for (q = 0; q < HASHINPUT; q += 4) {
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printf(" %08x", *(uint32_t *)(pool.incomingb + q));
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}
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printf("\n");
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}
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#endif
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}
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/*
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* Might as well save this value back into `incoming', just so
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* there'll be some extra bizarreness there.
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*/
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SHATransform(digest, block);
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memcpy(pool.incoming, digest, sizeof(digest));
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pool.poolpos = sizeof(pool.incoming);
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pool.stir_pending = false;
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#ifdef RANDOM_DIAGNOSTICS
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{
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int p, q;
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printf("random stir done\npool:\n");
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for (p = 0; p < POOLSIZE; p += HASHSIZE) {
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printf(" ");
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for (q = 0; q < HASHSIZE; q += 4) {
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printf(" %08x", *(uint32_t *)(pool.pool + p + q));
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}
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printf("\n");
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}
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printf("incoming:\n ");
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for (q = 0; q < HASHSIZE; q += 4) {
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printf(" %08x", *(uint32_t *)(pool.incoming + q));
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}
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printf("\nincomingb:\n ");
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for (q = 0; q < HASHINPUT; q += 4) {
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printf(" %08x", *(uint32_t *)(pool.incomingb + q));
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}
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printf("\n");
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random_diagnostics--;
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}
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#endif
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}
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void random_add_noise(void *noise, int length)
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{
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unsigned char *p = noise;
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int i;
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if (!random_active)
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return;
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/*
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* This function processes HASHINPUT bytes into only HASHSIZE
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* bytes, so _if_ we were getting incredibly high entropy
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* sources then we would be throwing away valuable stuff.
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*/
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while (length >= (HASHINPUT - pool.incomingpos)) {
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memcpy(pool.incomingb + pool.incomingpos, p,
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HASHINPUT - pool.incomingpos);
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p += HASHINPUT - pool.incomingpos;
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length -= HASHINPUT - pool.incomingpos;
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SHATransform((uint32_t *) pool.incoming, (uint32_t *) pool.incomingb);
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for (i = 0; i < HASHSIZE; i++) {
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pool.pool[pool.poolpos++] ^= pool.incoming[i];
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if (pool.poolpos >= POOLSIZE)
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pool.poolpos = 0;
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}
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if (pool.poolpos < HASHSIZE)
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random_stir();
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pool.incomingpos = 0;
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}
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memcpy(pool.incomingb + pool.incomingpos, p, length);
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pool.incomingpos += length;
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}
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void random_add_heavynoise(void *noise, int length)
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{
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unsigned char *p = noise;
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int i;
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while (length >= POOLSIZE) {
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for (i = 0; i < POOLSIZE; i++)
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pool.pool[i] ^= *p++;
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random_stir();
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length -= POOLSIZE;
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}
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for (i = 0; i < length; i++)
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pool.pool[i] ^= *p++;
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random_stir();
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}
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static void random_add_heavynoise_bitbybit(void *noise, int length)
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{
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unsigned char *p = noise;
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int i;
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while (length >= POOLSIZE - pool.poolpos) {
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for (i = 0; i < POOLSIZE - pool.poolpos; i++)
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pool.pool[pool.poolpos + i] ^= *p++;
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random_stir();
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length -= POOLSIZE - pool.poolpos;
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pool.poolpos = 0;
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}
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for (i = 0; i < length; i++)
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pool.pool[i] ^= *p++;
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pool.poolpos = i;
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}
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static void random_timer(void *ctx, unsigned long now)
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{
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if (random_active > 0 && now == next_noise_collection) {
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noise_regular();
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next_noise_collection =
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schedule_timer(NOISE_REGULAR_INTERVAL, random_timer, &pool);
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}
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}
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void random_ref(void)
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{
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if (!random_active) {
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memset(&pool, 0, sizeof(pool)); /* just to start with */
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noise_get_heavy(random_add_heavynoise_bitbybit);
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random_stir();
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next_noise_collection =
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schedule_timer(NOISE_REGULAR_INTERVAL, random_timer, &pool);
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}
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random_active++;
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}
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void random_unref(void)
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{
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assert(random_active > 0);
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if (random_active == 1) {
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random_save_seed();
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expire_timer_context(&pool);
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}
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random_active--;
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}
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int random_byte(void)
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{
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assert(random_active);
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if (pool.poolpos >= POOLSIZE)
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random_stir();
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return pool.pool[pool.poolpos++];
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}
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void random_get_savedata(void **data, int *len)
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{
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void *buf = snewn(POOLSIZE / 2, char);
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random_stir();
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memcpy(buf, pool.pool + pool.poolpos, POOLSIZE / 2);
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*len = POOLSIZE / 2;
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*data = buf;
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random_stir();
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}
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#endif
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