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smg_comms_c_wrappers    1 #include <stdio.h>
smg_comms_c_wrappers    2 #include <stdlib.h>
smg_comms_c_wrappers    3 #include <string.h>
smg_comms_c_wrappers    4 
smg_comms_c_wrappers    5 #include <fcntl.h>
smg_comms_c_wrappers    6 #include <unistd.h>
smg_comms_c_wrappers    7 #include <termios.h>
smg_comms_c_wrappers    8 #include <errno.h>
smg_comms_c_wrappers    9 
smg_comms_c_wrappers   10 #include "smg_rsa.h"
smg_comms_c_wrappers   11 
smg_comms_c_wrappers   12 
smg_comms_c_wrappers   13 int set_usb_attribs(int fd, int speed) {
smg_comms_c_wrappers   14 	struct termios tty;
smg_comms_c_wrappers   15 	if (tcgetattr(fd, &tty) < 0) {
smg_comms_c_wrappers   16 		return -1;
smg_comms_c_wrappers   17 	}
smg_comms_c_wrappers   18 
smg_comms_c_wrappers   19 	/* input and output speeds */
smg_comms_c_wrappers   20 	cfsetospeed(&tty, (speed_t)speed);
smg_comms_c_wrappers   21 	cfsetispeed(&tty, (speed_t)speed);
smg_comms_c_wrappers   22 
smg_comms_c_wrappers   23 	/* raw */
smg_comms_c_wrappers   24 	tty.c_lflag &= ~(ECHO | ECHOE | ECHOK);
smg_comms_c_wrappers   25 	tty.c_oflag &= ~OPOST;
smg_comms_c_wrappers   26 
smg_comms_c_wrappers   27 	/* read at least one octet at a time; BLOCK until at least VMIN octets read */
smg_comms_c_wrappers   28 	tty.c_cc[VMIN] = 1;
smg_comms_c_wrappers   29 	tty.c_cc[VTIME] = 0;
smg_comms_c_wrappers   30 
smg_comms_c_wrappers   31 	if (tcsetattr(fd, TCSAFLUSH, &tty) != 0)
smg_comms_c_wrappers   32 		return -1;
smg_comms_c_wrappers   33 
smg_comms_c_wrappers   34 	return 0;
smg_comms_c_wrappers   35 }
smg_comms_c_wrappers   36 
smg_comms_c_wrappers   37 int open_entropy_source(char* source_name) {
smg_comms_c_wrappers   38 	int in, err;
smg_comms_c_wrappers   39 
smg_comms_c_wrappers   40 	in = open(source_name, O_RDONLY | O_NOCTTY | O_NDELAY);
smg_comms_c_wrappers   41 	if (in == -1) {
smg_comms_c_wrappers   42 		printf("ERROR: failure to open entropy source %s: %s\n", source_name, strerror(errno));
smg_comms_c_wrappers   43 		return in;	//failed to access entropy source
smg_comms_c_wrappers   44 	}
smg_comms_c_wrappers   45 
smg_comms_c_wrappers   46 	fcntl(in, F_SETFL, 0);
smg_comms_c_wrappers   47 
smg_comms_c_wrappers   48 	err = set_usb_attribs(in, B115200);
smg_comms_c_wrappers   49 	if (err==-1) {
smg_comms_c_wrappers   50 		printf("Error setting attributes on %s: %s\n", source_name, strerror(errno));
smg_comms_c_wrappers   51 		return err;
smg_comms_c_wrappers   52 	}
smg_comms_c_wrappers   53 
smg_comms_c_wrappers   54 	return in;	//source opened, return its descriptor
smg_comms_c_wrappers   55 }
smg_comms_c_wrappers   56 
smg_comms_c_wrappers   57 int get_random_octets_from(int noctets, unsigned char *out, int from) {
smg_comms_c_wrappers   58 
smg_comms_c_wrappers   59 	int nread;
smg_comms_c_wrappers   60 	int total = 0;
smg_comms_c_wrappers   61 
smg_comms_c_wrappers   62 	while (total < noctets) {
smg_comms_c_wrappers   63 		errno = 0;
smg_comms_c_wrappers   64 		nread = read(from, out+total, noctets-total);
smg_comms_c_wrappers   65 		//on interrupt received just try again
smg_comms_c_wrappers   66 		if (nread == -1 && errno == EINTR)
smg_comms_c_wrappers   67 			continue;
smg_comms_c_wrappers   68 		//on error condition abort
smg_comms_c_wrappers   69 		if (errno != 0 && (nread == -1 || nread == 0)) {
smg_comms_c_wrappers   70 			printf("Error reading from entropy source %s after %d read: %s\n", ENTROPY_SOURCE, total, strerror(errno));
smg_comms_c_wrappers   71 			return total;		//total read so far
smg_comms_c_wrappers   72 		}
smg_comms_c_wrappers   73 
smg_comms_c_wrappers   74 		if (nread > 0)
smg_comms_c_wrappers   75 			total = total + nread;
smg_comms_c_wrappers   76 	}
smg_comms_c_wrappers   77 	return total;	//return number of octets read
smg_comms_c_wrappers   78 }
smg_comms_c_wrappers   79 
smg_comms_c_wrappers   80 int get_random_octets(int noctets, unsigned char *out) {
smg_comms_c_wrappers   81 	int in;
smg_comms_c_wrappers   82 	int nread = 0;
smg_comms_c_wrappers   83 
smg_comms_c_wrappers   84 	in = open_entropy_source(ENTROPY_SOURCE);
smg_comms_c_wrappers   85 	if (in > 0) {
smg_comms_c_wrappers   86 		nread = get_random_octets_from(noctets, out, in);
smg_comms_c_wrappers   87 		close(in);
smg_comms_c_wrappers   88 	}
smg_comms_c_wrappers   89 	return nread;
smg_comms_c_wrappers   90 }
smg_comms_c_wrappers   91 
smg_comms_c_wrappers   92 int rng_dirty_float(float *n) {
smg_comms_c_wrappers   93   int status;   /* for aborting in case of error */
smg_comms_c_wrappers   94   uint32_t r;   /* a random value on 32 bits */
smg_comms_c_wrappers   95   uint32_t maxval = 0xffffffff; /* maximum value on 32 bits */
smg_comms_c_wrappers   96 
smg_comms_c_wrappers   97   /* obtain a random number on 32 bits using ENTROPY_SOURCE */
smg_comms_c_wrappers   98   status = rng_uint32( &r );
smg_comms_c_wrappers   99   if ( status < 0 )
smg_comms_c_wrappers  100     return status;
smg_comms_c_wrappers  101 
smg_comms_c_wrappers  102   /* calculate and assign the floating-point random value as (r*1.0)/max val */
smg_comms_c_wrappers  103   /* multiplication by 1.0 IS NEEDED to do float division rather than int div*/
smg_comms_c_wrappers  104   *n = ( r * 1.0 ) / maxval;
smg_comms_c_wrappers  105 
smg_comms_c_wrappers  106   return 1;
smg_comms_c_wrappers  107 }
smg_comms_c_wrappers  108 
smg_comms_c_wrappers  109 int rng_float_754_1985(float *n) {
smg_comms_c_wrappers  110   /* Single float ieee 754/1985 has 23 bits that can be set for the mantissa
smg_comms_c_wrappers  111    * (and one implicit bit=1).
smg_comms_c_wrappers  112    * Full single float ieee 754/1985 representation takes 4 octets in total.
smg_comms_c_wrappers  113    */
smg_comms_c_wrappers  114   int noctets = 4; /* number of octets to read from ENTROPY_SOURCE */
smg_comms_c_wrappers  115   int nread;       /* number of octets *read* from ENTROPY_SOURCE  */
smg_comms_c_wrappers  116   unsigned char bits[ noctets ]; /* the random bits from ENTROPY_SOURCE */ 
smg_comms_c_wrappers  117   int oSignExp, oExpM;/* offsets for sign+exponent octet, exponent+mantissa*/
smg_comms_c_wrappers  118 
smg_comms_c_wrappers  119   /* obtain random bits */
smg_comms_c_wrappers  120   nread = get_random_octets( noctets, bits );
smg_comms_c_wrappers  121 
smg_comms_c_wrappers  122   if (nread != noctets )
smg_comms_c_wrappers  123     return -1;  /* something wrong at reading from ENTROPY_SOURCE, abort */
smg_comms_c_wrappers  124 
smg_comms_c_wrappers  125   /* set offsets for bit diddling depending on endianness of iron */
smg_comms_c_wrappers  126   if (is_bigendian()) {
smg_comms_c_wrappers  127     oSignExp = 0;
smg_comms_c_wrappers  128     oExpM = 1;
smg_comms_c_wrappers  129   }
smg_comms_c_wrappers  130   else {
smg_comms_c_wrappers  131     oSignExp = 3;
smg_comms_c_wrappers  132     oExpM = 2;
smg_comms_c_wrappers  133   }
smg_comms_c_wrappers  134 
smg_comms_c_wrappers  135   /* set sign=0; exponent=127; explicit mantissa = random bits (23 bits) */
smg_comms_c_wrappers  136   *(bits+oExpM) = *(bits+2) | 0x80;  /* one bit of exponent set */
smg_comms_c_wrappers  137   *(bits+oSignExp) = 0x3f;           /* sign=0; exponent bits for 127 */
smg_comms_c_wrappers  138 
smg_comms_c_wrappers  139   /* now copy the bits to the result var (i.e. as a float's representation */
smg_comms_c_wrappers  140   memcpy( n, bits, noctets );
smg_comms_c_wrappers  141   return 1;
smg_comms_c_wrappers  142 }
smg_comms_c_wrappers  143 
smg_comms_c_wrappers  144 int rng_uint32( uint32_t *n ) {
smg_comms_c_wrappers  145   int noctets = 4;  /*  32 bits aka 4 octets to read from ENTROPY_SOURCE     */
smg_comms_c_wrappers  146   int nread;        /*  the number of octets read from ENTROPY_SOURCE        */
smg_comms_c_wrappers  147   unsigned char bits[ noctets ]; /* for storing the bits from ENTROPY_SOURCE */
smg_comms_c_wrappers  148 
smg_comms_c_wrappers  149   /* read random 32 bits from ENTROPY_SOURCE */
smg_comms_c_wrappers  150   nread = get_random_octets( noctets, bits );
smg_comms_c_wrappers  151   if ( nread != noctets )
smg_comms_c_wrappers  152     return -1;
smg_comms_c_wrappers  153 
smg_comms_c_wrappers  154   /* copy the random bits to n, to be interpreted as uint32 */
smg_comms_c_wrappers  155   /* endianness is irrelevant here - the bits are random anyway */
smg_comms_c_wrappers  156   memcpy( n, bits, noctets );
smg_comms_c_wrappers  157 
smg_comms_c_wrappers  158   return 1;
smg_comms_c_wrappers  159 }
smg_comms_c_wrappers  160 
smg_comms_c_wrappers  161 int rng_uint64( uint64_t *n ) {
smg_comms_c_wrappers  162   int noctets = 8;  /*  64 bits aka 8 octets to read from ENTROPY_SOURCE     */
smg_comms_c_wrappers  163   int nread;        /*  the number of octets read from ENTROPY_SOURCE        */
smg_comms_c_wrappers  164   unsigned char bits[ noctets ]; /* for storing the bits from ENTROPY_SOURCE */
smg_comms_c_wrappers  165 
smg_comms_c_wrappers  166   /* read random 64 bits from ENTROPY_SOURCE */
smg_comms_c_wrappers  167   nread = get_random_octets( noctets, bits );
smg_comms_c_wrappers  168   if ( nread != noctets )
smg_comms_c_wrappers  169     return -1;
smg_comms_c_wrappers  170 
smg_comms_c_wrappers  171   /* copy the random bits to n, to be interpreted as uint64 */
smg_comms_c_wrappers  172   /* endianness is irrelevant here - the bits are random anyway */
smg_comms_c_wrappers  173   memcpy( n, bits, noctets );
smg_comms_c_wrappers  174 
smg_comms_c_wrappers  175   return 1;
smg_comms_c_wrappers  176 }