Permalink
Find file Copy path
Fetching contributors…
Cannot retrieve contributors at this time
135 lines (118 sloc) 3.92 KB
/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
* Copyright (C) 2001, 2002, 2004, 2007, 2008, 2010 by the Massachusetts Institute of Technology.
* All rights reserved.
*
*
* Export of this software from the United States of America may require
* a specific license from the United States Government. It is the
* responsibility of any person or organization contemplating export to
* obtain such a license before exporting.
*
* WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
* distribute this software and its documentation for any purpose and
* without fee is hereby granted, provided that the above copyright
* notice appear in all copies and that both that copyright notice and
* this permission notice appear in supporting documentation, and that
* the name of M.I.T. not be used in advertising or publicity pertaining
* to distribution of the software without specific, written prior
* permission. Furthermore if you modify this software you must label
* your software as modified software and not distribute it in such a
* fashion that it might be confused with the original M.I.T. software.
* M.I.T. makes no representations about the suitability of
* this software for any purpose. It is provided "as is" without express
* or implied warranty.
*/
#include "crypto_int.h"
krb5_error_code KRB5_CALLCONV
krb5_c_random_seed(krb5_context context, krb5_data *data)
{
return krb5_c_random_add_entropy(context, KRB5_C_RANDSOURCE_OLDAPI, data);
}
/* Routines to get entropy from the OS. */
#if defined(_WIN32)
krb5_boolean
k5_get_os_entropy(unsigned char *buf, size_t len, int strong)
{
krb5_boolean result;
HCRYPTPROV provider;
/* CryptGenRandom is always considered strong. */
if (!CryptAcquireContext(&provider, NULL, NULL, PROV_RSA_FULL,
CRYPT_VERIFYCONTEXT))
return FALSE;
result = CryptGenRandom(provider, len, buf);
(void)CryptReleaseContext(provider, 0);
return result;
}
#else /* not Windows */
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
#ifdef __linux__
#include <sys/syscall.h>
#endif /* __linux__ */
/* Open device, ensure that it is not a regular file, and read entropy. Return
* true on success, false on failure. */
static krb5_boolean
read_entropy_from_device(const char *device, unsigned char *buf, size_t len)
{
struct stat sb;
int fd;
unsigned char *bp;
size_t left;
ssize_t count;
krb5_boolean result = FALSE;
fd = open(device, O_RDONLY);
if (fd == -1)
return FALSE;
set_cloexec_fd(fd);
if (fstat(fd, &sb) == -1 || S_ISREG(sb.st_mode))
goto cleanup;
for (bp = buf, left = len; left > 0;) {
count = read(fd, bp, left);
if (count <= 0)
goto cleanup;
left -= count;
bp += count;
}
result = TRUE;
cleanup:
close(fd);
return result;
}
krb5_boolean
k5_get_os_entropy(unsigned char *buf, size_t len, int strong)
{
const char *device;
#if defined(__linux__) && defined(SYS_getrandom)
int r;
while (len > 0) {
/*
* Pull from the /dev/urandom pool, but require it to have been seeded.
* This ensures strong randomness while only blocking during first
* system boot.
*
* glibc does not currently provide a binding for getrandom:
* https://sourceware.org/bugzilla/show_bug.cgi?id=17252
*/
errno = 0;
r = syscall(SYS_getrandom, buf, len, 0);
if (r <= 0) {
if (errno == EINTR)
continue;
/* ENOSYS or other unrecoverable failure */
break;
}
len -= r;
buf += r;
}
if (len == 0)
return TRUE;
#endif /* defined(__linux__) && defined(SYS_getrandom) */
device = strong ? "/dev/random" : "/dev/urandom";
return read_entropy_from_device(device, buf, len);
}
#endif /* not Windows */