/* Package Name    : twhttpd
 * File Name       : htpasswd.c
 * Author          : Sam NG <samng@computer.org>
 * All rights reserved.
 *
 * This package is an secure HTTP application proxy writen by Sam Ng.
 * The software is free for commercial and non-commercial use as long as
 * the following conditions are aheared to.
 * 
 * Copyright remains Sam NG's, and as such any Copyright notices in
 * the code are not to be removed.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY SAM NG ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * 
 * The licence and distribution terms for any publically available version or
 * derivative of this code cannot be changed.  i.e. this code cannot simply be
 * copied and put under another distribution licence
 * [including the GNU Public Licence.]
 */

#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <pwd.h>

#define MAX_PASS 32

/* generate DES password */
char *encrypt_passwd(char *passwd)
{
    int i;
    char salt[3] = {'0', '1', '\0' } ;
    char *ascii_table = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789./" ;
    char *encrypt;

    srand(time(0));

    // generate salt
    i = (int) (64.0*rand()/(RAND_MAX+1.0));
    salt[0] = ascii_table[i];
    i = (int) (64.0*rand()/(RAND_MAX+1.0));
    salt[1] = ascii_table[i];
    
    encrypt = (char *) crypt(passwd, salt);
    return (NULL == encrypt) ? "!" : encrypt;
}

/* 
 * check if the string is in ASCII char only 
 * range 
 */
int non_ascii(char *fname)
{
    char *ptr;
    
    ptr = fname;
    
    while ( '\0' != *ptr )
    {
        // allowed char set is 
        // between 0d32 (space) to 0d126 (~)
        if ( *ptr < ' ' || *ptr > '~' ) return 1;
        ptr++;
    }
    
    return 0;
}

int main(int argc, char *argv[])
{
    int i=0;
    char *user, *pass;
    char pass1[MAX_PASS], pass2[MAX_PASS];
    char field1[MAX_PASS], field2[MAX_PASS];
    char format_string[64];
    char *fname;
    FILE *fp;
    
    if ( argc < 3 ) 
    {
        fprintf(stderr, "HTTP password generator\n");
        fprintf(stderr, "Usage: %s htpasswd_file user_name\n", argv[0]);
        return 0;
    }
    
    fname = argv[1];
    user = argv[2];
    
    /* check username */
    for ( i=0; i<strlen(user); i++) 
    {
        if ( !isalnum(*(user+i)) ) 
        {
            fprintf(stderr, "User name can only be alpha-numeric\n");
            exit(-1);
        }
    }
    
    /* read from file to check if the user already exit */
    if ( NULL == (fp=fopen(fname, "rt")) )
    {
        fprintf(stderr, "fopen(%s): %s\n", fname, strerror(errno));
        return -1;
    }
    
    /* setup format string, used in fscanf() */
    if ( snprintf(format_string, sizeof(format_string)-1, "%%%d[^:]:%%%ds\n", MAX_PASS, MAX_PASS) < 0 )
    {
        return -1;
    }
    while ( 2 == fscanf(fp, format_string, field1, field2) )
    {
        if ( !strcmp(user, field1) )
        {
            fprintf(stderr, "User \"%s\" already exist\n", user);
            exit(-1);
        }
    }

    /* close and reopen it in append mode */    
    fclose(fp);
    if ( NULL == (fp=fopen(fname, "at")) )
    {
        fprintf(stderr, "fopen(%s): %s\n", fname, strerror(errno));
        return -1;
    }
    
    /* OK this user is new */
    i = 0;
    do 
    {
        if ( i >= 3 ) 
        {
            fprintf(stderr, "Too many errors\n");
            return 0;
        }
        if ( 0 != i ) fprintf(stderr, "Passwords do not match\n");
        i++;
        strcpy(pass1, getpass("Input Password: "));
        if ( non_ascii(pass1) )
        {
            fprintf(stderr, "Password can be ascii characters 32-127 only\n");
            continue;
        }
        strcpy(pass2, getpass("Confirm Password: "));
    } while ( strcmp(pass1, pass2) );

    pass = encrypt_passwd(pass1);
    
    fprintf(fp, "%s:%s\n", user, pass);
    
    return 0;
}