crypt() isn't generating a valid md5/shadow password

[Peter Jay Salzman]

sorry, but i'm trying to write some tools for beowulf administration.

consider the program:

        #include<stdio.h>
        #include<string.h>
        #include<crypt.h>

        int main(int argc, char **argv)
        {
                char password[50];
                char salt[50];

                if (argc != 3) {
                        printf("Usage: encrypt salt password\n\n");
                        exit(1);
                } else if (strlen(argv[1]) != 8) {
                        printf("Usage: encrypt salt password\n");
                        printf("The salt must have 8 characters.\n\n");
                        exit(1);
                } else if (strlen(argv[2]) < 5 || strlen(argv[2]) > 10) {
                        printf("Usage: encrypt salt password\n");
                        printf("The password must be 5-10 characters.\n\n");
                        exit(1);
                }

                strncpy(salt, "$1$", 3);
                strncat(salt, argv[1], 46);
                strncpy(password, crypt(argv[1], salt), 49);
                printf("%s\n", password);
                return(0);
        }

here's an example:

        # ./a.out 12345678 mypassword
        $1$12345678$f8QoJuo0DpBRfQSD0vglc1

this is suspicious to begin with.  the salt appears in the encrypted
password?    ok, whatever.   i put it in /etc/shadow and try to log in using
a password of "mypassword"

        $ su testuser
        Password:
        su: incorrect password

i typed in the password correctly.   i was hoping this would give me
something i could use for /etc/shadow to create a new user.

what's going on with the password?  why isn't it working?

pete