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#include "config.h"
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#if defined (__linux__) \
|| defined (__APPLE__) \
|| defined (__FreeBSD__) \
|| defined (__OpenBSD__)
# define USE_GETENTROPY
#elif defined (_WIN32) && ! defined (__MINGW32__)
# define USE_WINCRYPT
#endif
/* getentropy() vs rand()+time()+getpid() */
#ifdef USE_GETENTROPY
#if defined (__linux__) || defined (__APPLE__)
# include <sys/random.h>
#else
# include <unistd.h>
#endif
#elif defined (USE_WINCRYPT)
# define WIN32_LEAN_AND_MEAN
# include <Windows.h>
# include <wincrypt.h>
#else
# include <time.h>
/* getpid() on Windows */
# if defined (_WIN32) && ! defined (__MINGW32__)
# include <io.h>
# else
# include <unistd.h>
# endif
#endif
#define CLASS(ch, chars) \
{ \
.c = ch, \
.letters = chars, \
.size = sizeof(chars) - 1, \
},
struct grammar_class {
char c;
char *letters;
int size;
};
struct grammar_class classes[] = {
CLASSES
};
int const classes_n = sizeof(classes) / sizeof(classes[0]);
#ifdef USE_WINCRYPT
HCRYPTPROV win_rng = NULL;
#endif
bool init_rng(void)
{
#ifdef USE_WINCRYPT
CryptAcquireContext(
&win_rng,
NULL,
NULL,
PROV_RSA_FULL,
CRYPT_VERIFYCONTEXT | CRYPT_SILENT
);
if (!win_rng)
return false;
#elif ! defined (USE_GETENTROPY) && ! defined (USE_WINCRYPT)
/*
* TODO: seed better RNG
* this isn't very good, but it's enough(?) for now
*
* anything else we could use on general posix systems?
* perhaps /dev/urandom is a better fallback before doing this
*/
srand(time(NULL) + getpid() % 420 - 69);
#endif
return true;
}
unsigned int get_rng(void)
{
unsigned int r;
#ifdef USE_GETENTROPY
getentropy(&r, sizeof(r));
#elif defined (USE_WINCRYPT)
/* TODO: This could fail. Figure out how to handle */
CryptGenRandom(win_rng, sizeof(r), (BYTE *) &r);
#else
r = rand();
#endif
return r;
}
char grammar_buf[STATIC_BUFFER_SIZE + 1] = DEFAULT_GRAMMAR;
char password_buf[STATIC_BUFFER_SIZE + 1];
char *build_grammar(int triplets, int specials, int numbers, int *grammar_size)
{
*grammar_size = triplets * 3 + specials + numbers;
char *build = grammar_buf;
if (*grammar_size > STATIC_BUFFER_SIZE) {
build = malloc(*grammar_size + 1);
if (build == NULL) {
perror("malloc");
return NULL;
}
}
build[*grammar_size] = 0;
if (triplets > 0) {
memcpy(build, "Cvc", 3);
for (int i = 1; i < triplets; ++i)
memcpy(build + (i * 3), "cvc", 3);
}
memset(build + (triplets * 3), '!', specials);
memset(build + (triplets * 3) + specials, '#', numbers);
return build;
}
int main(int argc, char *argv[])
{
bool err = false;
char *grammar = grammar_buf;
int grammar_size = sizeof(DEFAULT_GRAMMAR) - 1;
char *password = password_buf;
if (argc == 2) {
if (strcmp(argv[1], "--help") == 0) {
printf("\
passgen - a small, customisable password generator\n\
Usage: %s\n\
%s <grammar>\n\
%s <#triplets ('Cvc')> <#symbols> <#numbers>\n\
Hints:\n\
- No arguments generates with the default grammar.\n\
- If three numbers are provided, a password will be generated in the 'standard form', <triplets><symbols><numbers>.\n\
Compile-time options (edit `config.h` to customise!):\n\
- Default grammar: %s\n", argv[0], argv[0], argv[0], grammar_buf);
printf(" - Grammar mappings:\n");
for (int i = 0; i < classes_n; ++i) {
printf(" - '%c' => \"%s\"\n", classes[i].c, classes[i].letters);
}
return 0;
}
/* Take first argument as the grammar */
grammar = argv[1];
grammar_size = strlen(grammar);
} else if (argc == 4) {
/*
* Take arguments as triplets, specials, numbers
* atoi might be scuffed but so be it (it just goes = 0 if invalid input)
*/
grammar = build_grammar(atoi(argv[1]), atoi(argv[2]), atoi(argv[3]), &grammar_size);
if (grammar == NULL) {
fprintf(stderr, "ERROR: Could not initialise memory for password grammar.\n");
err = true;
goto cleanup;
}
}
if (grammar_size > STATIC_BUFFER_SIZE) {
password = malloc(grammar_size + 1);
if (password == NULL) {
perror("malloc");
err = true;
goto cleanup;
}
}
password[grammar_size] = 0;
if (!init_rng()) {
fprintf(stderr, "ERROR: Could not initialise RNG.\n");
err = true;
goto cleanup;
}
for (int i = 0; i < grammar_size; ++i) {
char c = grammar[i];
bool caps = false;
if (c >= 'A' && c <= 'Z') {
caps = true;
c += 'a' - 'A';
}
struct grammar_class *class = NULL;
for (int j = 0; j < classes_n; ++j) {
if (c == classes[j].c) {
class = &classes[j];
break;
}
}
if (class == NULL) {
fprintf(stderr, "ERROR: Invalid grammar character '%c'.\n", c);
err = true;
goto cleanup;
}
do {
password[i] = class->letters[get_rng() % class->size] - (caps ? 'a' - 'A' : 0);
} while (i != 0 && password[i] == password[i - 1]);
}
printf("%s\n", password);
cleanup:
#ifdef USE_WINCRYPT
CryptReleaseContext(win_rng, 0);
#endif
if (grammar != grammar_buf)
free(grammar);
if (password != password_buf)
free(password);
if (err)
return 1;
return 0;
}
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