path: root/src/onetimebluh.c

#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>
#include <openssl/rand.h>
#include <unistd.h>
#include <errno.h>
#include <error.h>

void xor(int ed, char* mess, char* keyf, char* outp);		/* operates the bitwise XOR between mess and keyf and puts the output to outp */
void keyrand(int nb, char* outp);				/* generates random numbers using RAND_bytes from openssl and puts them into outp */
void help(char* av[]);						/* prints the help message */

int main(int argc, char* argv[]) {

	int opt = 1;
	int command = 0;
	int comm = 0;
	int tear = 0;
	char* message = NULL;
	char* keyfile = NULL;
	char* output = NULL;
	int nbytes = -1;	// must be resolved temporary workaround (ho sonno)

	/* The following while cycle parses the argv vector to find commands, options and relative arguments
	   using the function getopt_long */

	while (opt) {
		int option_index = 0;
		static struct option options[] = {
			{"decrypt",	required_argument,	0,	'd'},
			{"encrypt",	required_argument,	0,	'e'},
			{"key-file",	required_argument,	0,	'k'},
			{"key-gen",	no_argument,		0,	'g'},
			{"help",	no_argument,		0,	'h'},
			{"nbytes",	required_argument,	0,	'b'},
			{"output",	required_argument,	0,	'o'},
			{"tear-page",	no_argument,		0,	't'},
			{0,		0,			0,	0},
		};

		if ((opt = getopt_long(argc, argv, "b:d:e:ghk:o:t", options, &option_index)) == -1)
			break;

		switch (opt) {
		case 'b':
			nbytes = atoi(argv[optind-1]);
			break;
		case 'd':
			message = argv[optind-1];
			command++;
			comm = 'u';
			break;
		case 'e':
			message = argv[optind-1];
			if (access(message, F_OK) == -1) {		/* checks the existence of the file and eventually exits */
				error(errno, errno, message);
			}
			command++;
			comm = 'e';
			break;
		case 'g':
			command++;
			comm = 'g';
			break;
		case 'h':
			help(argv);
			command++;
			break;
		case 'k':
			keyfile = argv[optind-1];
			if (access(keyfile, F_OK) == -1) {		/* look at the comment before */
				error(errno, errno, keyfile);
			}
			break;
		case 'o':
			output = argv[optind-1];
			break;
		case 't':
			tear = 1;
			break;
		case '?':
			break;
		default:
			printf("carachter code returned 0%o \n", opt);
		}
	}

	/* Next section performs some input checks */

	if (command == 0) {
		printf("No command called \n");
		exit(EXIT_FAILURE);
	} else if (command > 1) {
		printf("Multiple commands called \n");
		printf("%s [COMMAND] [OPTIONS] ... \n",argv[0]);
		exit(EXIT_FAILURE);
	}

	if (optind < argc) {
		printf("Too many arguments \n");
		exit(EXIT_FAILURE);
	}

	/* Next section detects the functions to call */

	if (comm == 'e' || comm == 'u') {
		if (keyfile == NULL) {
			printf("No key specified: exit! \n");
			exit(EXIT_FAILURE);
		}
		if (tear == 1) {
			comm++;
		}
		xor(comm, message, keyfile, output);
	} else if (comm == 'g') {
		keyrand(nbytes, output);
	}

	exit(EXIT_SUCCESS);
}

void xor(int ed, char* mess, char* keyf, char* outp) {

	char* defenoutp = "critt";
	char* defdeoutp = "decritt";

	/* In absence of input by users nex block sets the default values */

	if (outp == NULL) {
		if (ed == 'e' || ed == 'f') {
			printf("WARNING no output name specified using default value 'critt' \n");
			outp = defenoutp;
		} else if (ed == 'u' || ed == 'v') {
			printf("WARNING no output name specified usign default value 'decritt' \n");
			outp = defdeoutp;
		}
	}

	FILE* mex = fopen(mess, "r");
	FILE* keyx = fopen(keyf, "r+");
	FILE* critt = fopen(outp, "w");

	long mess_size;
	long pad_size;

	fseek(mex, 0L, SEEK_END);
	mess_size = ftell(mex);
	rewind(mex);
	fseek(keyx, 0L, SEEK_END);
	pad_size = ftell(keyx);
	fseek(keyx, (pad_size - mess_size), SEEK_SET);

	int i = 1;
	char a, b;

	while (i != EOF) {
		i = fscanf(mex, "%c", &a);
		fscanf(keyx, "%c", &b);
		if(i != EOF) {
			fprintf(critt, "%c", a^b);
		}
	}

	if (ed == 'f' || ed == 'v') {
		ftruncate(fileno(keyx), (pad_size - mess_size));
		fseek(keyx, 0L, SEEK_END);
		long new_pad_size = ftell(keyx);
		printf("Your pad is now %li bytes shorter \n", mess_size);
		printf("You now have %li bytes left \n", new_pad_size);
	}

	fclose(mex);
	fclose(keyx);
	fclose(critt);

	if (ed == 'e' || ed == 'f') {
		printf("Message successfully encrypted \n");
	} else if (ed == 'u' || ed == 'v') {
		printf("Message successfully decrypted \n");
	}

	return;
}

void keyrand(int nb, char* outp) {

	char* defoutp = "default.key";

	/* Next block controls the inputs and eventually sets the default values */

	if((nb == -1) && (outp == NULL)) {
		printf("WARNING no option specified usign default values... \n");
		nb = 256;
		outp = defoutp;
	}
	if (nb < -1) {		// orribile
		printf("Negative byte value inserted! \n");
		printf("Exiting... \n");
		exit(EXIT_FAILURE);
	} else if (nb != 0) {
		if(nb == -1) {
			printf("No byte number specified... using default value: 256 \n");
			nb = 256;
		}

		unsigned char key[nb];
		RAND_bytes(key, nb);

		if (outp == NULL) {
			outp = defoutp;
			printf("No output name specified... using default value: default.key \n");
		}

		FILE* file = fopen(outp, "w");
		fwrite(key, sizeof(char), nb, file);
		fclose(file);
		printf("Created key file %s of %d bytes \n", outp, nb);
	} else {
		printf("Byte number specified is 0. \n");
		printf("Doing nothing! \n");
	}

	return;
}

void help(char* av[]) {
	fprintf(stdout,"ONETIMEBLUH USAGE: \n"
	"%s [COMMAND] [OPTIONS] \n \n"
	"COMMANDS: \n"
	"-d, --decrypt=FILE	decrypt message (input) same ad --encrypt, just for the feeling \n"
	"-e, --encrypt=FILE	encrypt message (input) \n"
	"-h, --help		print this help \n"
	"-g, --key-gen		create key file \n \n"
	"OPTIONS \n"
	"-k, --key-file=KEY_FILE	use key (input) \n"
	"-b, --nbytes=NUM	number of bytes \n"
	"-o, --output=FILE	output name \n"
	"-t, --tear-page		deletes from the pad file the bytes used to encrypt/decrypt \n \n"
	"Onetimebluh project repository at https://git.eigenlab.org/Seppia/onetimebluh \n", av[0]);

	return;
}