memgen.c

/****************************
 * MemGen: Version 1.0      *
 * Author: Michael Warren   *
 * Date: November 8-9, 2018 *
 ****************************/

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

void generate( void );
void memorize( char * );
void mode_switch();
void command( char * );
void nl_strip( char * );
void input( void );
void prompt( void );

int length;

char password[64];

#define MEM_MODE 0
#define CMD_MODE 1

int mode = MEM_MODE;

/* Switch between Command and Memorization modes */
void mode_switch(){
    printf( "\e[2J\e[H" );
    if( mode == MEM_MODE ){
        printf( "Command Mode\nType \"help\" to see a list of available commands.\n" );
        mode = CMD_MODE;
        putchar( '\n' );
    }
    else{
        mode = MEM_MODE;
        putchar( '\n' );
    }
}

/* Replace newline character with null character */
void nl_strip( char *str ){
    int len = strlen( str );
    for( int i = 0; i < len; i++ ){
        if( str[i] == '\n' ){
            str[i] = '\0';
            break;
        }
    }
}

int main( int argc, char **argv ){
    length = (argv[1] && atoi( argv[1] )) ? atoi( argv[1] ) : 12;
    generate();
    input();
    return 0;
}

/* Generate truly random password */
void generate(){
    FILE *fp = fopen( "/dev/random", "r" );
    unsigned int c;
    for( int i = 0; i < length; i++ ){
        fread( &c, 4, 1, fp );
        c = c % 62;
        if( c < 26 )
            password[i] = 'A' + c;
        else if( c < 52 )
            password[i] = 'a' + c - 26;
        else
            password[i] = '0' + c - 52;
        password[length] = '\0';
    }
    putchar( '\n' );
    fclose( fp );
    printf( "\e[2J\e[H" );
    printf( "Generated password: %s\n", password );
    puts( "Press Enter to continue..." );
    getchar();
}

/* Portion aids in memorizing a password */
void memorize( char *buf ){
    if( !strcmp( buf, ":command" ) ){
        mode_switch();
        goto end;
    }
    else if( !strcmp( buf, password ) ) printf( "Correct\n" );
    else if( !strncmp( buf, password, strlen( buf ) ) ) printf( "Partially correct\n" );
    else printf( "Incorrect\n" );
    sleep( 1 );
end:
    sleep( 0 ); // Placeholder for label
}

/* Print prompt based on what mode you're in */
void prompt(){
    if( mode == CMD_MODE ){
        printf( "> " );
    }
    else{
        printf( "\e[2J\e[H" );
        printf( "Memorization Mode\nEnter :command to switch to Command Mode.\n" );
        printf( "Enter password: " );
    }
    fflush( stdout );
}

/* Input loop */
void input(){
    char buf[64];
    buf[63] = '\0'; // Prevents buffer overflow attacks
    for(;;){
        prompt();
        fgets( buf, 63, stdin );
        nl_strip( buf );
        if( mode == CMD_MODE ) command( buf );
        else memorize( buf );
    }
}

/* Input loop for Command mode */
void command( char *buf ){
    if( !strcmp( buf, "generate" ) ){
        generate();
    }
    else if( !strcmp( buf, "change-length" ) ){
        printf( "Enter new length: " );
        fflush( stdout );
        fgets( buf, 63, stdin );
        length = atoi( buf ) ? atoi( buf ) : 12;
    }
    else if( !strcmp( buf, "select-new" ) ){
        printf( "Enter new password: " );
        fflush( stdout );
        fgets( buf, 63, stdin );
        strncpy( password, buf, strlen( buf ) );
        nl_strip( password );
    }
    else if( !strcmp( buf, "print" ) ){
        puts( password );
    }
    else if( !strcmp( buf, "memorize" ) ){
        mode_switch();
    }
    else if( !strcmp( buf, "exit" ) ){
        exit( 0 );
    }
    else if( !strcmp( buf, "help" ) ){
        FILE *help;
        if( !(help = fopen( "memgen_help.txt", "r" )) ){
            puts( "Could not locate help file." );
        }
        int c;
        while( (c = fgetc( help )) != EOF ){
            putchar( c );
        }
    }
}