1
1
mirror of https://github.com/urbit/shrub.git synced 2024-12-30 15:44:03 +03:00
shrub/pkg/ent/ent.c
Benjamin Summers 9618f37965 Add 'pkg/ent/' from commit '31ac2913f14c6f7631f5792ad942605fb2d9fb87'
git-subtree-dir: pkg/ent
git-subtree-mainline: 1207c204cb
git-subtree-split: 31ac2913f1
2019-03-04 16:49:14 -08:00

63 lines
1.5 KiB
C

// Use `getentropy` from unistd.h //////////////////////////////////////////////
#if defined(ENT_GETENTROPY_UNISTD)
#include <stddef.h>
#include <unistd.h>
int ent_getentropy(void* buf, size_t len) {
return getentropy(buf, len);
}
// Use `getentropy` from sys/random.h //////////////////////////////////////////
#elif defined(ENT_GETENTROPY_SYSRANDOM)
#include <stddef.h>
#include <sys/random.h>
int ent_getentropy(void* buf, size_t len) {
return getentropy(buf, len);
}
// Use the `getrandom` syscall /////////////////////////////////////////////////
#elif defined(ENT_GETRANDOM_SYSCALL)
#include <stddef.h>
#include <errno.h>
#define _GNU_SOURCE
#include <unistd.h>
#include <sys/syscall.h>
#define ENTFAIL { errno=EIO; return -1; }
int ent_getentropy(void* buf, size_t len) {
if (len > 256) ENTFAIL
int r = syscall(SYS_getrandom, buf, len, 0);
if (r < 0) return r;
if (r != len) ENTFAIL
return 0;
}
// Use `/dev/urandom` //////////////////////////////////////////////////////////
#elif defined(ENT_DEV_URANDOM)
#include <stddef.h>
#include <errno.h>
#include <stdio.h>
#define ENTFAIL { errno=EIO; return -1; }
int ent_getentropy(void* buf, size_t len) {
if (len > 256) ENTFAIL;
FILE *f = fopen("/dev/urandom", "re");
if (!f) return -1;
int r = fread(buf, 1, len, f);
(void) fclose(f);
if (r != len) ENTFAIL
return 0;
}
#else
#error "One of these must be set: ENT_DEV_URANDOM, ENT_GETENTROPY_UNISTD, ENT_GETENTROPY_SYSRANDOM, ENT_GETRANDOM_SYSCALL"
#endif