/* -*- 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 */