seedrng: further reduce size

- Remove all games with errno to further reduce code size.
- Combine error messages that don't benefit from being separated.
- Lock directory fd instead of separate file.

function                                             old     new   delta
static.longopts                                       38      26     -12
seed_from_file_if_exists                             426     413     -13
packed_usage                                       34519   34480     -39
.rodata                                           108484  108407     -77
seedrng_main                                        1088    1000     -88
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/5 up/down: 0/-229)           Total: -229 bytes
   text	   data	    bss	    dec	    hex	filename
 976208	   4227	   1816	 982251	  efceb	busybox_old
 975979	   4227	   1816	 982022	  efc06	busybox_unstripped

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>

1 files changed, 22 insertions, 55 deletions

diff --git a/util-linux/seedrng.c b/util-linux/seedrng.c
index 53be5048a..bc6ae5cb4 100644
--- a/util-linux/seedrng.c
+++ b/util-linux/seedrng.c
@@ -21,7 +21,7 @@
  */
 
 //config:config SEEDRNG
-//config:       bool "seedrng (2.4 kb)"
+//config:       bool "seedrng (2.1 kb)"
 //config:       default y
 //config:       help
 //config:       Seed the kernel RNG from seed files, meant to be called
@@ -33,12 +33,11 @@
 //kbuild:lib-$(CONFIG_SEEDRNG) += seedrng.o
 
 //usage:#define seedrng_trivial_usage
-//usage:        "[-d SEED_DIRECTORY] [-l LOCK_FILE] [-n]"
+//usage:        "[-d SEED_DIRECTORY] [-n]"
 //usage:#define seedrng_full_usage "\n\n"
 //usage:        "Seed the kernel RNG from seed files."
 //usage:        "\n"
 //usage:        "\n     -d, --seed-dir DIR      Use seed files from specified directory (default: /var/lib/seedrng)"
-//usage:        "\n     -l, --lock-file FILE    Use file as exclusive lock (default: /var/run/seedrng.lock)"
 //usage:        "\n     -n, --skip-credit       Skip crediting seeds, even if creditable"
 
 #include "libbb.h"
@@ -65,14 +64,7 @@
 #define GRND_INSECURE 0x0004 /* Apparently some headers don't ship with this yet. */
 #endif
 
-#if ENABLE_PID_FILE_PATH
-#define PID_FILE_PATH CONFIG_PID_FILE_PATH
-#else
-#define PID_FILE_PATH "/var/run"
-#endif
-
 #define DEFAULT_SEED_DIR "/var/lib/seedrng"
-#define DEFAULT_LOCK_FILE PID_FILE_PATH "/seedrng.lock"
 #define CREDITABLE_SEED_NAME "seed.credit"
 #define NON_CREDITABLE_SEED_NAME "seed.no-credit"
 
@@ -116,8 +108,6 @@ static int read_new_seed(uint8_t *seed, size_t len, bool *is_creditable)
                 return 0;
         if (open_read_close("/dev/urandom", seed, len) == (ssize_t)len)
                 return 0;
-        if (!errno)
-                errno = EIO;
         return -1;
 }
 
@@ -155,34 +145,29 @@ static int seed_from_file_if_exists(const char *filename, int dfd, bool credit,
 {
         uint8_t seed[MAX_SEED_LEN];
         ssize_t seed_len;
-        int ret = 0;
 
         seed_len = open_read_close(filename, seed, sizeof(seed));
         if (seed_len < 0) {
-                if (errno != ENOENT) {
-                        ret = -errno;
-                        bb_simple_perror_msg("unable to read seed file");
-                }
-                goto out;
+                if (errno == ENOENT)
+                        return 0;
+                bb_simple_perror_msg("unable to read seed file");
+                return -1;
         }
         if ((unlink(filename) < 0 || fsync(dfd) < 0) && seed_len) {
-                ret = -errno;
                 bb_simple_perror_msg("unable to remove seed after reading, so not seeding");
-                goto out;
-        }
-        if (!seed_len)
-                goto out;
+                return -1;
+        } else if (!seed_len)
+                return 0;
 
         sha256_hash(hash, &seed_len, sizeof(seed_len));
         sha256_hash(hash, seed, seed_len);
 
         printf("Seeding %zd bits %s crediting\n", seed_len * 8, credit ? "and" : "without");
-        ret = seed_rng(seed, seed_len, credit);
-        if (ret < 0)
+        if (seed_rng(seed, seed_len, credit) < 0) {
                 bb_simple_perror_msg("unable to seed");
-out:
-        errno = -ret;
-        return ret ? -1 : 0;
+                return -1;
+        }
+        return 0;
 }
 
 int seedrng_main(int argc, char *argv[]) MAIN_EXTERNALLY_VISIBLE;
@@ -190,8 +175,8 @@ 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, *lock_file, *creditable_seed, *non_creditable_seed;
-        int ret, fd = -1, dfd = -1, lock, program_ret = 0;
+        char *seed_dir, *creditable_seed, *non_creditable_seed;
+        int ret, fd = -1, dfd = -1, program_ret = 0;
         uint8_t new_seed[MAX_SEED_LEN];
         size_t new_seed_len;
         bool new_seed_creditable;
@@ -202,22 +187,18 @@ int seedrng_main(int argc UNUSED_PARAM, char *argv[])
         int opt;
         enum {
                 OPT_d = (1 << 0),
-                OPT_l = (1 << 1),
-                OPT_n = (1 << 2)
+                OPT_n = (1 << 1)
         };
 #if ENABLE_LONG_OPTS
         static const char longopts[] ALIGN1 =
                 "seed-dir\0"    Required_argument       "d"
-                "lock-file\0"   Required_argument       "l"
                 "skip-credit\0" No_argument             "n"
                 ;
 #endif
 
-        opt = getopt32long(argv, "d:l:n", longopts, &seed_dir, &lock_file);
+        opt = getopt32long(argv, "d:n", longopts, &seed_dir);
         if (!(opt & OPT_d) || !seed_dir)
                 seed_dir = xstrdup(DEFAULT_SEED_DIR);
-        if (!(opt & OPT_l) || !lock_file)
-                lock_file = xstrdup(DEFAULT_LOCK_FILE);
         skip_credit = opt & OPT_n;
         creditable_seed = concat_path_file(seed_dir, CREDITABLE_SEED_NAME);
         non_creditable_seed = concat_path_file(seed_dir, NON_CREDITABLE_SEED_NAME);
@@ -229,16 +210,9 @@ int seedrng_main(int argc UNUSED_PARAM, char *argv[])
         if (mkdir(seed_dir, 0700) < 0 && errno != EEXIST)
                 bb_simple_perror_msg_and_die("unable to create seed directory");
 
-        lock = open(lock_file, O_WRONLY | O_CREAT, 0000);
-        if (lock < 0 || flock(lock, LOCK_EX) < 0) {
-                bb_simple_perror_msg("unable to open lock file");
-                program_ret = 1;
-                goto out;
-        }
-
         dfd = open(seed_dir, O_DIRECTORY | O_RDONLY);
-        if (dfd < 0) {
-                bb_simple_perror_msg("unable to open seed directory");
+        if (dfd < 0 || flock(dfd, LOCK_EX) < 0) {
+                bb_simple_perror_msg("unable to open and lock seed directory");
                 program_ret = 1;
                 goto out;
         }
@@ -271,26 +245,19 @@ int seedrng_main(int argc UNUSED_PARAM, char *argv[])
 
         printf("Saving %zu bits of %s seed for next boot\n", new_seed_len * 8, new_seed_creditable ? "creditable" : "non-creditable");
         fd = open(non_creditable_seed, O_WRONLY | O_CREAT | O_TRUNC, 0400);
-        if (fd < 0) {
-                bb_simple_perror_msg("unable to open seed file for writing");
-                program_ret |= 1 << 4;
-                goto out;
-        }
-        if (write(fd, new_seed, new_seed_len) != (ssize_t)new_seed_len || fsync(fd) < 0) {
+        if (fd < 0 || full_write(fd, new_seed, new_seed_len) != (ssize_t)new_seed_len || fsync(fd) < 0) {
                 bb_simple_perror_msg("unable to write seed file");
-                program_ret |= 1 << 5;
+                program_ret |= 1 << 4;
                 goto out;
         }
         if (new_seed_creditable && rename(non_creditable_seed, creditable_seed) < 0) {
                 bb_simple_perror_msg("unable to make new seed creditable");
-                program_ret |= 1 << 6;
+                program_ret |= 1 << 5;
         }
 out:
         if (ENABLE_FEATURE_CLEAN_UP && fd >= 0)
                 close(fd);
         if (ENABLE_FEATURE_CLEAN_UP && dfd >= 0)
                 close(dfd);
-        if (ENABLE_FEATURE_CLEAN_UP && lock >= 0)
-                close(lock);
         return program_ret;
 }