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https://git.tartarus.org/simon/putty.git
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d159a6efac
This prevents an assertion failure when random_ref() tries to create a new PRNG instance and finds there already is one. It also exposes bugs in which some code path forgot to initialise the PRNG when it was going to need it, such as the one fixed in the previous commit.
139 lines
3.2 KiB
C
139 lines
3.2 KiB
C
/*
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* sshrand.c: manage the global live PRNG instance.
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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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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(NoiseSourceId source, const void *noise, int length) { }
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void random_ref(void) { }
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void random_setup_special(void) { }
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void random_unref(void) { }
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void random_read(void *out, size_t size)
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{
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memset(out, 0x45, size); /* 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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/* Dummy structure for the sake of having something to expire_timer_context */
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static struct random_timer_context { int dummy; } random_timer_ctx;
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static prng *global_prng;
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static unsigned long next_noise_collection;
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void random_add_noise(NoiseSourceId source, const void *noise, int length)
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{
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if (!random_active)
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return;
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prng_add_entropy(global_prng, source, make_ptrlen(noise, length));
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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,
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&random_timer_ctx);
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}
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}
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static void random_seed_callback(void *noise, int length)
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{
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put_data(global_prng, noise, length);
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}
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static void random_create(const ssh_hashalg *hashalg)
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{
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assert(!global_prng);
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global_prng = prng_new(hashalg);
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prng_seed_begin(global_prng);
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noise_get_heavy(random_seed_callback);
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prng_seed_finish(global_prng);
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next_noise_collection =
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schedule_timer(NOISE_REGULAR_INTERVAL, random_timer,
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&random_timer_ctx);
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/* noise_get_heavy probably read our random seed file.
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* Therefore (in fact, even if it didn't), we should write a
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* fresh one, in case another instance of ourself starts up
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* before we finish, and also in case an attacker gets hold of
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* the seed data we used. */
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random_save_seed();
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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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random_create(&ssh_sha256);
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}
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void random_setup_special()
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{
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random_active++;
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random_create(&ssh_sha512);
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}
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void random_reseed(ptrlen seed)
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{
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prng_seed_begin(global_prng);
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put_datapl(global_prng, seed);
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prng_seed_finish(global_prng);
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}
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void random_clear(void)
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{
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if (global_prng) {
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random_save_seed();
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expire_timer_context(&random_timer_ctx);
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prng_free(global_prng);
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global_prng = NULL;
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random_active = 0;
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}
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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 == 0)
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random_clear();
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}
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void random_read(void *buf, size_t size)
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{
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assert(random_active > 0);
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prng_read(global_prng, buf, size);
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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(global_prng->savesize, char);
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random_read(buf, global_prng->savesize);
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*len = global_prng->savesize;
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*data = buf;
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}
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size_t random_seed_bits(void)
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{
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assert(random_active > 0);
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return prng_seed_bits(global_prng);
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}
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#endif /* FUZZING */
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