# Administration Reference

## kpwvalid

Purpose

Checks quality of new password

Description

The kpwvalid command checks the quality of a new password passed to it from the kpasswd or kas setpassword command. It is optional. If it exists, it must reside in the same AFS directory as the binaries for the kpasswd and kas command suites (create a symbolic link from the client machine's local disk to this directory). The directory's ACL must extend the a (administer) and w (write) permissions to the system:administrators group only. These requirements prevent unauthorized users from substituting a spurious kpwvalid binary.

The AFS distribution includes an example kpwvalid program that checks that the password is at least eight characters long; the code for it appears in the following Examples section.

The script or program must accept a sequence of password strings, one per line, on the standard input stream. The first is the current password and is ignored. Each subsequent string is a candidate password to be checked. The program must write the following to the standard output stream for each one:

- `0` (zero) and a newline character to indicate that the password is acceptable

- A non-zero decimal number and a newline character to indicate that the password is not acceptable

Further, it must write any error messages only to the standard error stream, not to the standard output stream.

Examples

The following example program, included in the AFS distribution, verifies that the requested password includes eight or more characters.

       #include <stdio.h>
       /* prints 0 if the password is long enough, otherwise non-zero */
       main()
       {
       char oldpassword[512];
       char password[512];

       if (fgets(oldpassword, 512, stdin))
          while (fgets(password, 512, stdin)) {
             if (strlen(password) > 8) { /* password includes a newline */
                fputs("0\n",stdout);
                fflush(stdout);
             }
             else {
                fputs("Passwords must contain at least 8 characters.\n",
                      stderr);
                fputs("1\n",stdout);
                fflush(stdout);
             }
       return 0;
       }

Related Information

kas setpassword

kpasswd

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