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seedrng: do not hash in a constant string, it's not adding entropy

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function                                             old     new   delta
seedrng_main                                         906     880     -26
.rodata                                           104899  104873     -26
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(add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-52)             Total: -52 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2022-05-03 12:48:50 +02:00
parent 3bfbcb5807
commit 67fd6be0bb
1 changed files with 8 additions and 8 deletions
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16
miscutils/seedrng.c
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@ -169,7 +169,7 @@ int seedrng_main(int argc UNUSED_PARAM, char **argv)
uint8_t new_seed[MAX_SEED_LEN]; uint8_t new_seed[MAX_SEED_LEN];
size_t new_seed_len; size_t new_seed_len;
bool new_seed_creditable; bool new_seed_creditable;
struct timespec timestamp; struct timespec timestamp[2];
sha256_ctx_t hash; sha256_ctx_t hash;
enum { enum {
@ -197,19 +197,19 @@ int seedrng_main(int argc UNUSED_PARAM, char **argv)
* Avoid concurrent runs by taking a blocking lock on the directory. * Avoid concurrent runs by taking a blocking lock on the directory.
* Not checking for errors. Looking at manpage, * Not checking for errors. Looking at manpage,
* ENOLCK "The kernel ran out of memory for allocating lock records" * ENOLCK "The kernel ran out of memory for allocating lock records"
* seems to be the only one which is likely - and if that happens, * seems to be the only one which is possible - and if that happens,
* machine is OOMing (much worse problem than inability to lock...). * machine is OOMing (much worse problem than inability to lock...).
* Also, typically configured Linux machines do not fail GFP_KERNEL * Also, typically configured Linux machines do not fail GFP_KERNEL
* allocations (they trigger memory reclaim instead). * allocations (they trigger memory reclaim instead).
*/ */
flock(dfd, LOCK_EX); /* would block while another copy runs */ flock(dfd, LOCK_EX); /* blocks while another instance runs */
sha256_begin(&hash); sha256_begin(&hash);
sha256_hash(&hash, "SeedRNG v1 Old+New Prefix", 25); //Hashing in a constant string doesn't add any entropy
clock_gettime(CLOCK_REALTIME, &timestamp); // sha256_hash(&hash, "SeedRNG v1 Old+New Prefix", 25);
sha256_hash(&hash, &timestamp, sizeof(timestamp)); clock_gettime(CLOCK_REALTIME, &timestamp[0]);
clock_gettime(CLOCK_BOOTTIME, &timestamp); clock_gettime(CLOCK_BOOTTIME, &timestamp[1]);
sha256_hash(&hash, &timestamp, sizeof(timestamp)); sha256_hash(&hash, timestamp, sizeof(timestamp));
for (i = 0; i <= 1; i++) { for (i = 0; i <= 1; i++) {
seed_from_file_if_exists( seed_from_file_if_exists(