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random-seed: make the logic to calculate the number of bytes read from the random seed file clearer

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We want the size to lie within [/proc/sys/kernel/random/poolsize,RANDOM_POOL_SIZE_MAX]
interval. Let's make it more obvious.

Also move the logic in a dedicated function.
This commit is contained in:
Franck Bui
2022-10-20 08:45:02 +02:00
parent 0d0c6639d4
commit 205138d88a
1 changed files with 19 additions and 10 deletions
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29
src/random-seed/random-seed.c
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@@ -115,6 +115,22 @@ static CreditEntropy may_credit(int seed_fd) {
return CREDIT_ENTROPY_NO_WAY;
}
static int random_seed_size(int seed_fd, size_t *ret_size) {
struct stat st;
assert(ret_size);
assert(seed_fd >= 0);
if (fstat(seed_fd, &st) < 0)
return log_error_errno(errno, "Failed to stat() seed file " RANDOM_SEED ": %m");
/* If the seed file is larger than what the kernel expects, then honour the existing size and
* save/restore as much as it says */
*ret_size = CLAMP((uint64_t)st.st_size, random_pool_size(), RANDOM_POOL_SIZE_MAX);
return 0;
}
static int help(int argc, char *argv[], void *userdata) {
_cleanup_free_ char *link = NULL;
int r;
@@ -193,7 +209,6 @@ static int run(int argc, char *argv[]) {
_cleanup_free_ void* buf = NULL;
struct sha256_ctx hash_state;
size_t buf_size;
struct stat st;
ssize_t k, l;
int r;
@@ -205,8 +220,6 @@ static int run(int argc, char *argv[]) {
umask(0022);
buf_size = random_pool_size();
r = mkdir_parents(RANDOM_SEED, 0755);
if (r < 0)
return log_error_errno(r, "Failed to create directory " RANDOM_SEED_DIR ": %m");
@@ -261,13 +274,9 @@ static int run(int argc, char *argv[]) {
assert_not_reached();
}
if (fstat(seed_fd, &st) < 0)
return log_error_errno(errno, "Failed to stat() seed file " RANDOM_SEED ": %m");
/* If the seed file is larger than what we expect, then honour the existing size and save/restore as
* much as it says */
if ((uint64_t) st.st_size > buf_size)
buf_size = MIN(st.st_size, RANDOM_POOL_SIZE_MAX);
r = random_seed_size(seed_fd, &buf_size);
if (r < 0)
return r;
buf = malloc(buf_size);
if (!buf)