util-src/crand.c

   1 /* Prosody IM
   2 -- Copyright (C) 2008-2017 Matthew Wild
   3 -- Copyright (C) 2008-2017 Waqas Hussain
   4 -- Copyright (C) 2016-2017 Kim Alvefur
   5 --
   6 -- This project is MIT/X11 licensed. Please see the
   7 -- COPYING file in the source package for more information.
   8 --
   9 */
  10
  11 /*
  12 * crand.c
  13 * C PRNG interface
  14 *
  15 * The purpose of this module is to provide access to a PRNG in
  16 * environments without /dev/urandom
  17 *
  18 * Caution! This has not been extensively tested.
  19 *
  20 */
  21
  22 #define _DEFAULT_SOURCE
  23
  24 #include <stdlib.h>
  25 #include <string.h>
  26 #include <errno.h>
  27
  28 #include "lualib.h"
  29 #include "lauxlib.h"
  30
  31 #if defined(WITH_GETRANDOM)
  32
  33 #ifndef __GLIBC_PREREQ
  34 /* Not compiled with glibc at all */
  35 #define __GLIBC_PREREQ(a,b) 0
  36 #endif
  37
  38 #if ! __GLIBC_PREREQ(2,25)
  39 /* Not compiled with a glibc that provides getrandom() */
  40 #include <unistd.h>
  41 #include <sys/syscall.h>
  42
  43 #ifndef SYS_getrandom
  44 #error getrandom() requires Linux 3.17 or later
  45 #endif
  46
  47 /* This wasn't present before glibc 2.25 */
  48 int getrandom(void *buf, size_t buflen, unsigned int flags) {
  49         return syscall(SYS_getrandom, buf, buflen, flags);
  50 }
  51 #else
  52 #include <sys/random.h>
  53 #endif
  54
  55 #elif defined(WITH_OPENSSL)
  56 #include <openssl/rand.h>
  57 #elif defined(WITH_ARC4RANDOM)
  58 #ifdef __linux__
  59 #include <bsd/stdlib.h>
  60 #endif
  61 #else
  62 #error util.crand compiled without a random source
  63 #endif
  64
  65 #ifndef SMALLBUFSIZ
  66 #define SMALLBUFSIZ 32
  67 #endif
  68
  69 int Lrandom(lua_State *L) {
  70         char smallbuf[SMALLBUFSIZ];
  71         char *buf = &smallbuf[0];
  72         const lua_Integer l = luaL_checkinteger(L, 1);
  73         const size_t len = l;
  74         luaL_argcheck(L, l >= 0, 1, "must be > 0");
  75
  76         if(len == 0) {
  77                 lua_pushliteral(L, "");
  78                 return 1;
  79         }
  80
  81         if(len > SMALLBUFSIZ) {
  82                 buf = lua_newuserdata(L, len);
  83         }
  84
  85 #if defined(WITH_GETRANDOM)
  86         /*
  87          * This acts like a read from /dev/urandom with the exception that it
  88          * *does* block if the entropy pool is not yet initialized.
  89          */
  90         int left = len;
  91         char *p = buf;
  92
  93         do {
  94                 int ret = getrandom(p, left, 0);
  95
  96                 if(ret < 0) {
  97                         lua_pushstring(L, strerror(errno));
  98                         return lua_error(L);
  99                 }
 100
 101                 p += ret;
 102                 left -= ret;
 103         } while(left > 0);
 104
 105 #elif defined(WITH_ARC4RANDOM)
 106         arc4random_buf(buf, len);
 107 #elif defined(WITH_OPENSSL)
 108
 109         if(!RAND_status()) {
 110                 lua_pushliteral(L, "OpenSSL PRNG not seeded");
 111                 return lua_error(L);
 112         }
 113
 114         if(RAND_bytes((unsigned char *)buf, len) != 1) {
 115                 /* TODO ERR_get_error() */
 116                 lua_pushstring(L, "RAND_bytes() failed");
 117                 return lua_error(L);
 118         }
 119
 120 #endif
 121
 122         lua_pushlstring(L, buf, len);
 123         return 1;
 124 }
 125
 126 int luaopen_util_crand(lua_State *L) {
 127 #if (LUA_VERSION_NUM > 501)
 128         luaL_checkversion(L);
 129 #endif
 130
 131         lua_createtable(L, 0, 2);
 132         lua_pushcfunction(L, Lrandom);
 133         lua_setfield(L, -2, "bytes");
 134
 135 #if defined(WITH_GETRANDOM)
 136         lua_pushstring(L, "Linux");
 137 #elif defined(WITH_ARC4RANDOM)
 138         lua_pushstring(L, "arc4random()");
 139 #elif defined(WITH_OPENSSL)
 140         lua_pushstring(L, "OpenSSL");
 141 #endif
 142         lua_setfield(L, -2, "_source");
 143
 144         return 1;
 145 }
 146