random array index returning values not contained Post: 302278557

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Top Forums Programming random array index returning values not contained Post 302278557 by VRoemer on Tuesday 20th of January 2009 02:58:11 PM

01-20-2009

Registered User

random array index returning values not contained

For kicks I wrote up a Password generator after lunch. Let me start with the code:

Code:

unsigned int x,y,z,c;

unsigned int KISS();
unsigned int devrand();

int main( int argc, char** argv )
{
    int i, j = 1;
    char pwd[] = "abcdefghijklmnopqrstuvwxyz"
                 "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                 "1234567890"
                 "!@#$";
    char password[12];

    if( argv[1] )
        j = atoi(argv[1]);

    do {
        memset( password, '\0', sizeof(password) );
        for( i = 0; i < sizeof(password); ++i )
            password[i] = (char)pwd[(KISS() % strlen( pwd ))];
        printf("%s\n", password);
        --j;
    } while( j );

    return 0;
}
/*
 * Fairly popular Random Number generator
 */
unsigned int KISS()
{
    x = devrand();
    while(!(y=devrand())); // y must not be zero
    z = devrand();
    c = devrand();

    unsigned long long t;
    unsigned long long a = 698769069ULL;

    x = 69069*x + 12345;

    y ^= (y<<13);
    y ^= (y>>17);
    y ^= (y<<5);

    t = a*z+c;
    c = (t>>32);

    return x+y+(z=t);
}


/*
 * using a perfectly fine generator to generate a seed >.>"
 */
unsigned int devrand( void )
{
    int          f;
    unsigned int r;
    f=open("/dev/urandom", O_RDONLY);

    if( f == -1)          exit(-1); // ERROR?
    if( read(f,&r,4)!=4 ) exit(-1); // ERROR?

    close(f);
    return r;
}

( all there upon request )

Now this works just fine without issues but if I specify my array 'password' to be of say size 9 the program starts returning values not within the 'pwd' array.

Ive had it return quotes brackets and a bunch of various non printables.

Any idea's?

Last edited by VRoemer; 01-20-2009 at 04:57 PM..

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LEARN ABOUT OSF1

randomword

randomword(3)						     Library Functions Manual						     randomword(3)

NAME

       randomword, randomchars, randomletters - Generate random passwords (Enhanced Security)

LIBRARY

       Security Library - libsecurity.so

SYNOPSIS

       int randomchars(      char *string,	unsigned short int minlen,	unsigned short int maxlen,	boolean restrict,      long seed);
       int  randomletters(	 char  *string,       unsigned	short int minlen,      unsigned short int maxlen,      boolean restrict,      long
       seed);
       int randomword(	    char *word,      char *hyphenated_word,	 unsigned short int minlen,	 unsigned short int  maxlen,	   boolean
       restrict,      long seed);

PARAMETERS

       Points at a user-supplied space to contain a null-terminated password.  Specifies the minimum length that a generated word can have.  Spec-
       ifies the maximum length that a generated word can have.  Specifies whether restrictions are to be imposed on the generated word.  This	is
       a  boolean  integer, where a non-zero integer indications restrictions and a 0 (zero) indicates no restrictions.  Specifies an initial seed
       for the random number generator.  Points at a user-supplied space to contain a null-terminated random pronounceable password.  Contains the
       hyphenated version of the generated word.

DESCRIPTION

       These  functions  generate random passwords for use in password selection.  All of them are generated by the system, based on seeds and set
       in the function.  Such seeds can be created with the drand48(), rand(), or random() functions.

       The randomchars() function places a null-terminated password composed of random printable ASCII characters into the  string  parameter  and
       returns	the length of the generated string.  The minlen parameter can equal maxlen, but cannot be greater than maxlen, and cannot be nega-
       tive.  The user space preallocated is at least maxlen for string.  The smaller minlen and maxlen are, the smaller the  selection  space	of
       random words.

       The  restrict parameter is 0 (zero) when no restrictions are placed on the generated word.  It is nonzero when the words generated pass the
       tests of the acceptable_password() function.

       The seed parameter is used by the function only on the first time it is called; the parameter is ignored on subsequent calls.

       The randomletters() function places a null-terminated password composed of random lower-case letters into the string parameter and  returns
       the length of the generated word.  The minlen, maxlen, restrict, and seed parameters are the same as for the randomchars() function.

       The randomword() function places a null-terminated random pronounceable password into the word parameter and returns the length of the gen-
       erated word.  The minlen, maxlen, restrict, and seed parameters are the same as for the randomchars() and randomletters()  functions.   The
       user space preallocated is at least 2*max - 1 for hyphenated_word.

NOTES

       The  password  generator  relies on a random number generator that produces uniformly distributed integers.  Because the password generator
       invokes the random number generator many times even for one word, the random number generator has to produce a uniform  distribution.   The
       period  (distinct  numbers produced given a particular seed) and number space (range of possible numbers) must both be large. The drand48()
       functions are used for this purpose.

       Programs using these functions must be compiled with -lsecurity.

FILES

       System password file.  System group file.

RELATED INFORMATION

       Functions: acceptable_password(3), drand48(3), rand(3), random(3).

       Commands: login(1), passwd(1).  delim off

																     randomword(3)