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ch2_truerandom          1 #include <stdio.h>
ch2_truerandom          2 #include <stdlib.h>
ch2_truerandom          3 #include <string.h>
ch2_truerandom          4 
ch2_truerandom          5 #include <fcntl.h>
ch2_truerandom          6 #include <unistd.h>
ch2_truerandom          7 #include <termios.h>
ch2_truerandom          8 #include <errno.h>
ch2_truerandom          9 
ch2_truerandom         10 #include "smg_rsa.h"
ch2_truerandom         11 
ch2_truerandom         12 
ch2_truerandom         13 int set_usb_attribs(int fd, int speed) {
ch2_truerandom         14 	struct termios tty;
ch2_truerandom         15 	if (tcgetattr(fd, &tty) < 0) {
ch2_truerandom         16 		return -1;
ch2_truerandom         17 	}
ch2_truerandom         18 
ch2_truerandom         19 	//input and output speeds
ch2_truerandom         20 	cfsetospeed(&tty, (speed_t)speed);
ch2_truerandom         21 	cfsetispeed(&tty, (speed_t)speed);
ch2_truerandom         22 
ch2_truerandom         23 	tty.c_cflag |= (CLOCAL | CREAD);	//ignore modem controls
ch2_truerandom         24 	tty.c_cflag &= ~CSIZE;
ch2_truerandom         25 	tty.c_cflag |= CS8;			//8 bit characters
ch2_truerandom         26 	tty.c_cflag &= ~PARENB;	//no parity bit
ch2_truerandom         27 	tty.c_cflag &= ~CSTOPB;	//only need 1 stop bit
ch2_truerandom         28 	tty.c_cflag &= ~CRTSCTS;	//no hardware flow control
ch2_truerandom         29 
ch2_truerandom         30 	//non-canonical mode
ch2_truerandom         31 	tty.c_cflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP | INLCR | IGNCR | ICRNL | IXON);
ch2_truerandom         32 	tty.c_cflag &= ~(ECHO | ECHONL | ICANON | ISIG | IEXTEN);
ch2_truerandom         33 	tty.c_cflag &= ~OPOST;
ch2_truerandom         34 
ch2_truerandom         35 	//read at least one octet at a time; timeout 1 tenth of second between octets read
ch2_truerandom         36 	tty.c_cc[VMIN] = 1;
ch2_truerandom         37 	tty.c_cc[VTIME] = 1;
ch2_truerandom         38 
ch2_truerandom         39 	if (tcsetattr(fd, TCSANOW, &tty) != 0)
ch2_truerandom         40 		return -1;
ch2_truerandom         41 
ch2_truerandom         42 	return 0;
ch2_truerandom         43 }
ch2_truerandom         44 
ch2_truerandom         45 int open_entropy_source(char* source_name) {
ch2_truerandom         46 	int in, err;
ch2_truerandom         47 
ch2_truerandom         48 	in = open(source_name, O_RDONLY | O_NOCTTY | O_NDELAY);
ch2_truerandom         49 	if (in == -1) {
ch2_truerandom         50 		printf("ERROR: failure to open entropy source %s: %s\n", source_name, strerror(errno));
ch2_truerandom         51 		return in;	//failed to access entropy source
ch2_truerandom         52 	}
ch2_truerandom         53 
ch2_truerandom         54 	fcntl(in, F_SETFL, 0);
ch2_truerandom         55 
ch2_truerandom         56 	err = set_usb_attribs(in, B115200);
ch2_truerandom         57 	if (err==-1) {
ch2_truerandom         58 		printf("Error setting attributes on %s: %s\n", source_name, strerror(errno));
ch2_truerandom         59 		return err;
ch2_truerandom         60 	}
ch2_truerandom         61 
ch2_truerandom         62 	return in;	//source opened, return its descriptor
ch2_truerandom         63 }
ch2_truerandom         64 
ch2_truerandom         65 int get_random_octets_from(int noctets, unsigned char *out, int from) {
ch2_truerandom         66 
ch2_truerandom         67 	int nread;
ch2_truerandom         68 	int total = 0;
ch2_truerandom         69 
ch2_truerandom         70 	while (total < noctets) {
ch2_truerandom         71 		nread = read(from, out+total, noctets-total);
ch2_truerandom         72 		//on interrupt received just try again
ch2_truerandom         73 		if (nread == -1 && errno == EINTR)
ch2_truerandom         74 			continue;
ch2_truerandom         75 		//on error condition abort
ch2_truerandom         76 		if (nread == -1 || nread == 0) {
ch2_truerandom         77 			printf("Error reading from entropy source %s: %s\n", ENTROPY_SOURCE, strerror(errno));
ch2_truerandom         78 			return total;		//total read so far
ch2_truerandom         79 		}
ch2_truerandom         80 
ch2_truerandom         81 		if (nread > 0)
ch2_truerandom         82 			total = total + nread;
ch2_truerandom         83 	}
ch2_truerandom         84 	return total;	//return number of octets read
ch2_truerandom         85 }
ch2_truerandom         86 
ch2_truerandom         87 int get_random_octets(int noctets, unsigned char *out) {
ch2_truerandom         88 	int in;
ch2_truerandom         89 	int nread = 0;
ch2_truerandom         90 
ch2_truerandom         91 	in = open_entropy_source(ENTROPY_SOURCE);
ch2_truerandom         92 	if (in > 0) {
ch2_truerandom         93 		nread = get_random_octets_from(noctets, out, in);
ch2_truerandom         94 		close(in);
ch2_truerandom         95 	}
ch2_truerandom         96 	return nread;
ch2_truerandom         97 }
ch2_truerandom         98