/*	$OpenBSD: arc4random.c,v 1.58 2022/07/31 13:41:45 tb Exp $	*/

/*
 * Copyright (c) 1996, David Mazieres 
 * Copyright (c) 2008, Damien Miller 
    
 * Copyright (c) 2013, Markus Friedl 
     
 * Copyright (c) 2014, Theo de Raadt 
      
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/*
 * ChaCha based random number generator for OpenBSD.
 */

#include 
       
#include 
        
         #include 
         
          #include 
          
           #include 
           
            #include 
            
             #include 
             
              #include 
              
               #include 
               
                #define KEYSTREAM_ONLY #include "chacha_private.h" #define minimum(a, b) ((a) < (b) ? (a) : (b)) #if defined(__GNUC__) || defined(_MSC_VER) #define inline __inline #else /* __GNUC__ || _MSC_VER */ #define inline #endif /* !__GNUC__ && !_MSC_VER */ #define KEYSZ 32 #define IVSZ 8 #define BLOCKSZ 64 #define RSBUFSZ (16*BLOCKSZ) #define REKEY_BASE (1024*1024) /* NB. should be a power of 2 */ /* Marked MAP_INHERIT_ZERO, so zero'd out in fork children. */ static struct _rs { size_t rs_have; /* valid bytes at end of rs_buf */ size_t rs_count; /* bytes till reseed */ } *rs; /* Maybe be preserved in fork children, if _rs_allocate() decides. */ static struct _rsx { chacha_ctx rs_chacha; /* chacha context for random keystream */ u_char rs_buf[RSBUFSZ]; /* keystream blocks */ } *rsx; static inline int _rs_allocate(struct _rs **, struct _rsx **); static inline void _rs_forkdetect(void); #include "arc4random.h" static inline void _rs_rekey(u_char *dat, size_t datlen); static inline void _rs_init(u_char *buf, size_t n) { if (n < KEYSZ + IVSZ) return; if (rs == NULL) { if (_rs_allocate(&rs, &rsx) == -1) _exit(1); } chacha_keysetup(&rsx->rs_chacha, buf, KEYSZ * 8); chacha_ivsetup(&rsx->rs_chacha, buf + KEYSZ); } static void _rs_stir(void) { u_char rnd[KEYSZ + IVSZ]; uint32_t rekey_fuzz = 0; if (getentropy(rnd, sizeof rnd) == -1) _getentropy_fail(); if (!rs) _rs_init(rnd, sizeof(rnd)); else _rs_rekey(rnd, sizeof(rnd)); explicit_bzero(rnd, sizeof(rnd)); /* discard source seed */ /* invalidate rs_buf */ rs->rs_have = 0; memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf)); /* rekey interval should not be predictable */ chacha_encrypt_bytes(&rsx->rs_chacha, (uint8_t *)&rekey_fuzz, (uint8_t *)&rekey_fuzz, sizeof(rekey_fuzz)); rs->rs_count = REKEY_BASE + (rekey_fuzz % REKEY_BASE); } static inline void _rs_stir_if_needed(size_t len) { _rs_forkdetect(); if (!rs || rs->rs_count <= len) _rs_stir(); if (rs->rs_count <= len) rs->rs_count = 0; else rs->rs_count -= len; } static inline void _rs_rekey(u_char *dat, size_t datlen) { #ifndef KEYSTREAM_ONLY memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf)); #endif /* fill rs_buf with the keystream */ chacha_encrypt_bytes(&rsx->rs_chacha, rsx->rs_buf, rsx->rs_buf, sizeof(rsx->rs_buf)); /* mix in optional user provided data */ if (dat) { size_t i, m; m = minimum(datlen, KEYSZ + IVSZ); for (i = 0; i < m; i++) rsx->rs_buf[i] ^= dat[i]; } /* immediately reinit for backtracking resistance */ _rs_init(rsx->rs_buf, KEYSZ + IVSZ); memset(rsx->rs_buf, 0, KEYSZ + IVSZ); rs->rs_have = sizeof(rsx->rs_buf) - KEYSZ - IVSZ; } static inline void _rs_random_buf(void *_buf, size_t n) { u_char *buf = (u_char *)_buf; u_char *keystream; size_t m; _rs_stir_if_needed(n); while (n > 0) { if (rs->rs_have > 0) { m = minimum(n, rs->rs_have); keystream = rsx->rs_buf + sizeof(rsx->rs_buf) - rs->rs_have; memcpy(buf, keystream, m); memset(keystream, 0, m); buf += m; n -= m; rs->rs_have -= m; } if (rs->rs_have == 0) _rs_rekey(NULL, 0); } } static inline void _rs_random_u32(uint32_t *val) { u_char *keystream; _rs_stir_if_needed(sizeof(*val)); if (rs->rs_have < sizeof(*val)) _rs_rekey(NULL, 0); keystream = rsx->rs_buf + sizeof(rsx->rs_buf) - rs->rs_have; memcpy(val, keystream, sizeof(*val)); memset(keystream, 0, sizeof(*val)); rs->rs_have -= sizeof(*val); } uint32_t arc4random(void) { uint32_t val; _ARC4_LOCK(); _rs_random_u32(&val); _ARC4_UNLOCK(); return val; } DEF_WEAK(arc4random); void arc4random_buf(void *buf, size_t n) { _ARC4_LOCK(); _rs_random_buf(buf, n); _ARC4_UNLOCK(); } DEF_WEAK(arc4random_buf);