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Add evutil_secure_rng_set_urandom_device_file

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This experimental function is needed for some seccomp2 hackery to
work, and should have no effect for systems that don't use it.
This commit is contained in:
Nick Mathewson 2013-08-06 17:06:23 -04:00
parent b8f59807ce
commit 2bbb5d7612
3 changed files with 57 additions and 14 deletions
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32
arc4random.c
View File

@ -293,21 +293,17 @@ arc4_seed_proc_sys_kernel_random_uuid(void)
#ifndef WIN32
#define TRY_SEED_URANDOM
static int
arc4_seed_urandom(void)
static char *arc4random_urandom_filename = NULL;
static int arc4_seed_urandom_helper_(const char *fname)
{
/* This is adapted from Tor's crypto_seed_rng() */
static const char *filenames[] = {
"/dev/srandom", "/dev/urandom", "/dev/random", NULL
};
unsigned char buf[ADD_ENTROPY];
int fd, i;
int fd;
size_t n;
for (i = 0; filenames[i]; ++i) {
fd = evutil_open_closeonexec(filenames[i], O_RDONLY, 0);
fd = evutil_open_closeonexec(fname, O_RDONLY, 0);
if (fd<0)
continue;
return -1;
n = read_all(fd, buf, sizeof(buf));
close(fd);
if (n != sizeof(buf))
@ -316,6 +312,22 @@ arc4_seed_urandom(void)
memset(buf, 0, sizeof(buf));
arc4_seeded_ok = 1;
return 0;
}
static int
arc4_seed_urandom(void)
{
/* This is adapted from Tor's crypto_seed_rng() */
static const char *filenames[] = {
"/dev/srandom", "/dev/urandom", "/dev/random", NULL
};
int i;
if (arc4random_urandom_filename)
return arc4_seed_urandom_helper_(arc4random_urandom_filename);
for (i = 0; filenames[i]; ++i) {
if (arc4_seed_urandom_helper_(filenames[i]) == 0)
return 0;
}
return -1;

17
evutil_rand.c
View File

@ -43,6 +43,12 @@
#include <stdlib.h>
#include <string.h>
int
evutil_secure_rng_set_urandom_device_file(char *fname)
{
(void) fname;
return -1;
}
int
evutil_secure_rng_init(void)
{
/* call arc4random() now to force it to self-initialize */
@ -123,6 +129,17 @@ evutil_secure_rng_global_setup_locks_(const int enable_locks)
}
#endif
int
evutil_secure_rng_set_urandom_device_file(char *fname)
{
#ifdef TRY_SEED_URANDOM
_ARC4_LOCK();
arc4random_urandom_filename = fname;
_ARC4_UNLOCK();
#endif
return 0;
}
int
evutil_secure_rng_init(void)
{

14
include/event2/util.h
View File

@ -675,6 +675,20 @@ void evutil_secure_rng_get_bytes(void *buf, size_t n);
*/
int evutil_secure_rng_init(void);
/**
* Set a filename to use in place of /dev/urandom for seeding the secure
* PRNG. Return 0 on success, -1 on failure.
*
* Call this function BEFORE calling any other initialization or .
*
* (This string will _NOT_ be copied internally. Do not free it while any
* user of the secure RNG might be running. Don't pass anything other than a
* real /dev/...random device file here, or you might lose security.)
*
* This API is unstable, and might change in a future libevent version.
*/
int evutil_secure_rng_set_urandom_device_file(char *fname);
/** Seed the random number generator with extra random bytes.
You should almost never need to call this function; it should be