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Annotation of qemu/roms/ipxe/src/crypto/crandom.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 2009 Joshua Oreman <[email protected]>.
        !             3:  *
        !             4:  * This program is free software; you can redistribute it and/or
        !             5:  * modify it under the terms of the GNU General Public License as
        !             6:  * published by the Free Software Foundation; either version 2 of the
        !             7:  * License, or any later version.
        !             8:  *
        !             9:  * This program is distributed in the hope that it will be useful, but
        !            10:  * WITHOUT ANY WARRANTY; without even the implied warranty of
        !            11:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
        !            12:  * General Public License for more details.
        !            13:  *
        !            14:  * You should have received a copy of the GNU General Public License
        !            15:  * along with this program; if not, write to the Free Software
        !            16:  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
        !            17:  */
        !            18: 
        !            19: FILE_LICENCE ( GPL2_OR_LATER );
        !            20: 
        !            21: /** @file
        !            22:  *
        !            23:  * Cryptographically strong random number generator
        !            24:  *
        !            25:  * Currently the cryptographic part is not implemented, and this just
        !            26:  * uses random().
        !            27:  */
        !            28: 
        !            29: #include <ipxe/crypto.h>
        !            30: #include <stdlib.h>
        !            31: 
        !            32: /**
        !            33:  * Get cryptographically strong random bytes
        !            34:  *
        !            35:  * @v buf      Buffer in which to store random bytes
        !            36:  * @v len      Number of random bytes to generate
        !            37:  *
        !            38:  * @b WARNING: This function is currently underimplemented, and does
        !            39:  * not give numbers any stronger than random()!
        !            40:  */
        !            41: void get_random_bytes ( void *buf, size_t len )
        !            42: {
        !            43:        u8 *bufp = buf;
        !            44: 
        !            45:        /*
        !            46:         * Somewhat arbitrarily, choose the 0x00FF0000-masked byte
        !            47:         * returned by random() as having good entropy. PRNGs often
        !            48:         * don't provide good entropy in lower bits, and the top byte
        !            49:         * might show a pattern because of sign issues.
        !            50:         */
        !            51: 
        !            52:        while ( len-- ) {
        !            53:                *bufp++ = ( random() >> 16 ) & 0xFF;
        !            54:        }
        !            55: }

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