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aestool.c
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aestool.c
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/***********************************************************************
aestool : an AES encryption utility
Copyright (C) 2013 David Harper at obliquity.com
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see [http://www.gnu.org/licenses/].
***********************************************************************/
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <gcrypt.h>
#include "aestool.h"
#define BUFSIZE 1024
static void printUsage(FILE *fp, char *progname, const char *version) {
fprintf(fp, "aestool : an AES encryption utility\n");
fprintf(fp, "\n");
fprintf(fp, "Copyright (C) 2013 David Harper at obliquity.com\n\n");
fprintf(fp, "This program comes with ABSOLUTELY NO WARRANTY.\n\n");
fprintf(fp, "This is free software, and you are welcome to redistribute it\n");
fprintf(fp, "under certain conditions. Please refer to the GNU General\n");
fprintf(fp, "Public License V3 [http://www.gnu.org/licenses/].\n\n");
fprintf(fp, "Usage: %s -e|-d [input filename] [output filename]\n\n", progname);
fprintf(fp, "MANDATORY EXCLUSIVE PARAMETERS:\n");
fprintf(fp, "\t-e\t\tEncrypt input\n");
fprintf(fp, "\t-d\t\tDecrypt input\n");
fprintf(fp, "\n");
fprintf(fp, "INPUT AND OUTPUT FILES\n");
fprintf(fp, "If no named input files are specified, the program will try to\n");
fprintf(fp, "encrypt/decrypt data from standard input and write the result to\n");
fprintf(fp, "standard output. The symbol - may be used to denote standard input\n");
fprintf(fp, "in place of an input file name or standard output in place of an\n");
fprintf(fp, "output file name.\n");
fprintf(fp, "\n");
fprintf(fp, "PASSPHRASE FILE\n");
fprintf(fp, "If the environment variable AESPASSFILE is defined and refers to a file\n");
fprintf(fp, "which cannot be read or written except by the user, then the passphrase\n");
fprintf(fp, "will be read from that file.\n\n");
fprintf(fp, "Otherwise, the passphrase will be read from /dev/tty. In this case, if\n");
fprintf(fp, "the input file is being encrypted, the user will be prompted for the\n");
fprintf(fp, "passphrase twice, and the operation will be abandoned if the two versions\n");
fprintf(fp, "do not match.\n");
fprintf(fp, "\n");
fprintf(fp, "ENCRYPTION STRENGTH\n");
fprintf(fp, "If the environment variable AES256 is defined, AES-256 encryption will be\n");
fprintf(fp, "used. Otherwise, AES-128 encryption will be used.\n\n");
fprintf(fp, "The encryption strength is NOT stored in the output file, so it is the\n");
fprintf(fp, "user's responsibility to remember whether AES-128 or AES-256 encryption was\n");
fprintf(fp, "used to create any given file.\n");
fprintf(fp, "\n");
fprintf(fp, "This program uses libgcrypt version %s\n", (version ? version : "[unknown]"));
}
static int exists(char *filename) {
struct stat stat_buf;
int rc;
rc = stat(filename, &stat_buf);
return (rc == 0) ? 1 : 0;
}
int main(int argc, char **argv) {
FILE *infile = NULL;
FILE *outfile = NULL;
unsigned char buffer[BUFSIZE];
unsigned char IV[16];
unsigned char key[32];
int mode = UNKNOWN;
char *infilename = NULL;
char *outfilename = NULL;
char *progname= argv[0];
int rc;
gcry_error_t error;
const char *version;
version = gcry_check_version(GCRYPT_VERSION);
if (argc < 2) {
printUsage(stderr, progname, version);
return 1;
}
if (!version) {
fprintf(stderr, "libgcrypt version mismatch: expected %s, found %s\n",
GCRYPT_VERSION, version);
return 99;
}
gcry_control(GCRYCTL_DISABLE_SECMEM, 0);
gcry_control(GCRYCTL_INITIALIZATION_FINISHED, 0);
if (strcmp(argv[1], "-e") == 0)
mode = ENCRYPT;
else if (strcmp(argv[1], "-d") == 0)
mode = DECRYPT;
else {
fprintf(stderr, "You must specify either -d or -e as the first command line option\n");
printUsage(stderr, progname, version);
return 1;
}
rc = getPassphrase((char *)buffer, sizeof(buffer), mode);
switch (rc) {
case BUFFER_TOO_SHORT:
fprintf(stderr, "%s: passphrase was too long\n", progname);
return 2;
case PASSPHRASE_MISMATCH:
fprintf(stderr, "%s: the passphrase did not match\n", progname);
return 3;
}
rc = strlen((char *)buffer);
error = createPassphraseHash(buffer, (size_t)rc, key, sizeof(key));
if (error != GPG_ERR_NO_ERROR) {
handleGcryptError("An error occurred whilst hashing the passphrase", error, stderr);
return 98;
}
memset(buffer, '\0', sizeof(buffer));
infilename = argc > 2 && strcmp(argv[2], "-") != 0 ? argv[2] : NULL;
infile = (infilename != NULL) ? fopen(infilename, "rb") : stdin;
if (infilename != NULL && infile == NULL) {
perror("Failed to open input file");
return 5;
}
outfilename = argc > 3 && strcmp(argv[3], "-") != 0 ? argv[3] : NULL;
outfile = (outfilename != NULL) ? fopen(outfilename, "wb") : stdout;
if (outfilename != NULL && outfile == NULL) {
perror("Failed to open output file");
return 6;
}
if (mode == ENCRYPT) {
gcry_create_nonce(IV, sizeof(IV));
} else {
fread(IV, 1, sizeof(IV), infile);
}
error = (mode == ENCRYPT) ?
encryptFile(infile, IV, key, outfile) :
decryptFile(infile, IV, key, outfile);
if (error != GPG_ERR_NO_ERROR) {
handleGcryptError("An error occurred whilst processing the data", error, stderr);
return 97;
}
return 0;
}