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authorJason A. Donenfeld <Jason@zx2c4.com>2022-04-20 15:27:29 +0200
committerBernhard Reutner-Fischer <rep.dot.nop@gmail.com>2022-04-20 15:42:53 +0200
commit31ec481baf106cf9c6d8f34ae6a55ab1738dea6f (patch)
tree1e7b88e2a22092d635a7c68e03b7b87da5205f57 /util-linux
parent453857899616acf1c77d0d02a4c2989b2cf5f1eb (diff)
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seedrng: hoist bb_strtoul out of min/max
- Hoist bb_strtoul out of min/max to prevent quadruple evaluation. - Don't use separate variables for boottime/realtime. - Make use of ENABLE_FEATURE_CLEAN_UP where appropriate. - Order hash initialization after lock taking per Bernhard's taste. - Add comment description of theory of operation. function old new delta seed_from_file_if_exists 533 456 -77 seedrng_main 1218 1086 -132 ------------------------------------------------------------------------------ (add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-209) Total: -209 bytes text data bss dec hex filename 976445 4227 1848 982520 efdf8 busybox_old 976236 4227 1848 982311 efd27 busybox_unstripped Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
Diffstat (limited to 'util-linux')
-rw-r--r--util-linux/seedrng.c46
1 files changed, 32 insertions, 14 deletions
diff --git a/util-linux/seedrng.c b/util-linux/seedrng.c
index d82a942aa..1bceae405 100644
--- a/util-linux/seedrng.c
+++ b/util-linux/seedrng.c
@@ -2,11 +2,26 @@
2/* 2/*
3 * Copyright (C) 2022 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. 3 * Copyright (C) 2022 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
4 * 4 *
5 * SeedRNG is a simple program made for seeding the Linux kernel random number
6 * generator from seed files. It is is useful in light of the fact that the
7 * Linux kernel RNG cannot be initialized from shell scripts, and new seeds
8 * cannot be safely generated from boot time shell scripts either. It should
9 * be run once at init time and once at shutdown time. It can be run at other
10 * times on a timer as well. Whenever it is run, it writes existing seed files
11 * into the RNG pool, and then creates a new seed file. If the RNG is
12 * initialized at the time of creating a new seed file, then that new seed file
13 * is marked as "creditable", which means it can be used to initialize the RNG.
14 * Otherwise, it is marked as "non-creditable", in which case it is still used
15 * to seed the RNG's pool, but will not initialize the RNG. In order to ensure
16 * that entropy only ever stays the same or increases from one seed file to the
17 * next, old seed values are hashed together with new seed values when writing
18 * new seed files.
19 *
5 * This is based on code from <https://git.zx2c4.com/seedrng/about/>. 20 * This is based on code from <https://git.zx2c4.com/seedrng/about/>.
6 */ 21 */
7 22
8//config:config SEEDRNG 23//config:config SEEDRNG
9//config: bool "seedrng (2.6 kb)" 24//config: bool "seedrng (2.5 kb)"
10//config: default y 25//config: default y
11//config: help 26//config: help
12//config: Seed the kernel RNG from seed files, meant to be called 27//config: Seed the kernel RNG from seed files, meant to be called
@@ -71,12 +86,14 @@ enum seedrng_lengths {
71static size_t determine_optimal_seed_len(void) 86static size_t determine_optimal_seed_len(void)
72{ 87{
73 char poolsize_str[11] = { 0 }; 88 char poolsize_str[11] = { 0 };
89 unsigned long poolsize;
74 90
75 if (open_read_close("/proc/sys/kernel/random/poolsize", poolsize_str, sizeof(poolsize_str) - 1) < 0) { 91 if (open_read_close("/proc/sys/kernel/random/poolsize", poolsize_str, sizeof(poolsize_str) - 1) < 0) {
76 bb_perror_msg("unable to determine pool size, falling back to %u bits", MIN_SEED_LEN * 8); 92 bb_perror_msg("unable to determine pool size, falling back to %u bits", MIN_SEED_LEN * 8);
77 return MIN_SEED_LEN; 93 return MIN_SEED_LEN;
78 } 94 }
79 return MAX(MIN((bb_strtoul(poolsize_str, NULL, 10) + 7) / 8, MAX_SEED_LEN), MIN_SEED_LEN); 95 poolsize = (bb_strtoul(poolsize_str, NULL, 10) + 7) / 8;
96 return MAX(MIN(poolsize, MAX_SEED_LEN), MIN_SEED_LEN);
80} 97}
81 98
82static int read_new_seed(uint8_t *seed, size_t len, bool *is_creditable) 99static int read_new_seed(uint8_t *seed, size_t len, bool *is_creditable)
@@ -130,7 +147,8 @@ static int seed_rng(uint8_t *seed, size_t len, bool credit)
130 ret = ioctl(random_fd, RNDADDENTROPY, &req); 147 ret = ioctl(random_fd, RNDADDENTROPY, &req);
131 if (ret) 148 if (ret)
132 ret = -errno ? -errno : -EIO; 149 ret = -errno ? -errno : -EIO;
133 close(random_fd); 150 if (ENABLE_FEATURE_CLEAN_UP)
151 close(random_fd);
134 errno = -ret; 152 errno = -ret;
135 return ret ? -1 : 0; 153 return ret ? -1 : 0;
136} 154}
@@ -171,7 +189,7 @@ static int seed_from_file_if_exists(const char *filename, bool credit, sha256_ct
171 if (ret < 0) 189 if (ret < 0)
172 bb_simple_perror_msg("unable to seed"); 190 bb_simple_perror_msg("unable to seed");
173out: 191out:
174 if (dfd >= 0) 192 if (ENABLE_FEATURE_CLEAN_UP && dfd >= 0)
175 close(dfd); 193 close(dfd);
176 errno = -ret; 194 errno = -ret;
177 return ret ? -1 : 0; 195 return ret ? -1 : 0;
@@ -187,7 +205,7 @@ int seedrng_main(int argc UNUSED_PARAM, char *argv[])
187 size_t new_seed_len; 205 size_t new_seed_len;
188 bool new_seed_creditable; 206 bool new_seed_creditable;
189 bool skip_credit = false; 207 bool skip_credit = false;
190 struct timespec realtime = { 0 }, boottime = { 0 }; 208 struct timespec timestamp = { 0 };
191 sha256_ctx_t hash; 209 sha256_ctx_t hash;
192 210
193 int opt; 211 int opt;
@@ -217,13 +235,6 @@ int seedrng_main(int argc UNUSED_PARAM, char *argv[])
217 if (getuid()) 235 if (getuid())
218 bb_simple_error_msg_and_die("this program requires root"); 236 bb_simple_error_msg_and_die("this program requires root");
219 237
220 sha256_begin(&hash);
221 sha256_hash(&hash, seedrng_prefix, strlen(seedrng_prefix));
222 clock_gettime(CLOCK_REALTIME, &realtime);
223 clock_gettime(CLOCK_BOOTTIME, &boottime);
224 sha256_hash(&hash, &realtime, sizeof(realtime));
225 sha256_hash(&hash, &boottime, sizeof(boottime));
226
227 if (mkdir(seed_dir, 0700) < 0 && errno != EEXIST) 238 if (mkdir(seed_dir, 0700) < 0 && errno != EEXIST)
228 bb_simple_perror_msg_and_die("unable to create seed directory"); 239 bb_simple_perror_msg_and_die("unable to create seed directory");
229 240
@@ -234,6 +245,13 @@ int seedrng_main(int argc UNUSED_PARAM, char *argv[])
234 goto out; 245 goto out;
235 } 246 }
236 247
248 sha256_begin(&hash);
249 sha256_hash(&hash, seedrng_prefix, strlen(seedrng_prefix));
250 clock_gettime(CLOCK_REALTIME, &timestamp);
251 sha256_hash(&hash, &timestamp, sizeof(timestamp));
252 clock_gettime(CLOCK_BOOTTIME, &timestamp);
253 sha256_hash(&hash, &timestamp, sizeof(timestamp));
254
237 ret = seed_from_file_if_exists(non_creditable_seed, false, &hash); 255 ret = seed_from_file_if_exists(non_creditable_seed, false, &hash);
238 if (ret < 0) 256 if (ret < 0)
239 program_ret |= 1 << 1; 257 program_ret |= 1 << 1;
@@ -270,9 +288,9 @@ int seedrng_main(int argc UNUSED_PARAM, char *argv[])
270 program_ret |= 1 << 6; 288 program_ret |= 1 << 6;
271 } 289 }
272out: 290out:
273 if (fd >= 0) 291 if (ENABLE_FEATURE_CLEAN_UP && fd >= 0)
274 close(fd); 292 close(fd);
275 if (lock >= 0) 293 if (ENABLE_FEATURE_CLEAN_UP && lock >= 0)
276 close(lock); 294 close(lock);
277 return program_ret; 295 return program_ret;
278} 296}
generated by cgit v1.2.3-55-g6feb (git 2.39.1) at 2025-03-17 08:41:19 +0000