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seedrng: avoid needless runtime strlen() call

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- Avoid needless runtime strlen() call, bloating binary.
- Replace failed seed string with series of nulls.

function                                             old     new   delta
.rodata                                           108350  108338     -12
static.seedrng_prefix                                 26       -     -26
seedrng_main                                        1000     948     -52
------------------------------------------------------------------------------
(add/remove: 0/1 grow/shrink: 0/2 up/down: 0/-90)             Total: -90 bytes
   text	   data	    bss	    dec	    hex	filename
 975919	   4227	   1816	 981962	  efbca	busybox_old
 975829	   4227	   1816	 981872	  efb70	busybox_unstripped

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
This commit is contained in:
Jason A. Donenfeld 2022-04-20 15:38:46 +02:00 committed by Bernhard Reutner-Fischer
parent ce9a345632
commit 3cb40f89de
1 changed files with 3 additions and 5 deletions
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8
util-linux/seedrng.c
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@ -21,7 +21,7 @@
*/ */
//config:config SEEDRNG //config:config SEEDRNG
//config: bool "seedrng (2.1 kb)" //config: bool "seedrng (2 kb)"
//config: default y //config: default y
//config: help //config: help
//config: Seed the kernel RNG from seed files, meant to be called //config: Seed the kernel RNG from seed files, meant to be called
@ -173,8 +173,6 @@ static int seed_from_file_if_exists(const char *filename, int dfd, bool credit,
int seedrng_main(int argc, char *argv[]) MAIN_EXTERNALLY_VISIBLE; int seedrng_main(int argc, char *argv[]) MAIN_EXTERNALLY_VISIBLE;
int seedrng_main(int argc UNUSED_PARAM, char *argv[]) int seedrng_main(int argc UNUSED_PARAM, char *argv[])
{ {
static const char seedrng_prefix[] = "SeedRNG v1 Old+New Prefix";
static const char seedrng_failure[] = "SeedRNG v1 No New Seed Failure";
char *seed_dir, *creditable_seed, *non_creditable_seed; char *seed_dir, *creditable_seed, *non_creditable_seed;
int ret, fd = -1, dfd = -1, program_ret = 0; int ret, fd = -1, dfd = -1, program_ret = 0;
uint8_t new_seed[MAX_SEED_LEN]; uint8_t new_seed[MAX_SEED_LEN];
@ -218,7 +216,7 @@ int seedrng_main(int argc UNUSED_PARAM, char *argv[])
} }
sha256_begin(&hash); sha256_begin(&hash);
sha256_hash(&hash, seedrng_prefix, strlen(seedrng_prefix)); sha256_hash(&hash, "SeedRNG v1 Old+New Prefix", 25);
clock_gettime(CLOCK_REALTIME, &timestamp); clock_gettime(CLOCK_REALTIME, &timestamp);
sha256_hash(&hash, &timestamp, sizeof(timestamp)); sha256_hash(&hash, &timestamp, sizeof(timestamp));
clock_gettime(CLOCK_BOOTTIME, &timestamp); clock_gettime(CLOCK_BOOTTIME, &timestamp);
@ -236,7 +234,7 @@ int seedrng_main(int argc UNUSED_PARAM, char *argv[])
if (ret < 0) { if (ret < 0) {
bb_simple_perror_msg("unable to read new seed"); bb_simple_perror_msg("unable to read new seed");
new_seed_len = SHA256_OUTSIZE; new_seed_len = SHA256_OUTSIZE;
strncpy((char *)new_seed, seedrng_failure, new_seed_len); memset(new_seed, 0, SHA256_OUTSIZE);
program_ret |= 1 << 3; program_ret |= 1 << 3;
} }
sha256_hash(&hash, &new_seed_len, sizeof(new_seed_len)); sha256_hash(&hash, &new_seed_len, sizeof(new_seed_len));