PAM password change failed on HPUX

[Ravi Avunoori]

I have a Pluggable Authentication Modules (PAM) based native tool called "ValidateUser" to:
a) Validate userName & password combination
b) Change password for newly created user

PAM function to change password:
int r_value = pam_chauthtok(pamh, PAM_SILENT);
Where r_value ccould be:
PAM_PERM_DENIED, PAM_AUTHTOK_ERR, PAM_AUTHTOK_RECOVERY_ERR, PAM_AUTHTOK_LOCK_BUSY, PAM_AUTHTOK_DISABLE_AGING, PAM_USER_UNKNOWN, PAM_TRY_AGAIN

The password change feature b) is causing "PAM_PERM_DENIED" error while trying to set a password on HPUX machine. I observed this issue on all three HPUX machines I tried so far. I tried it on HPUX OS levels B.11.31 and B.11.22. Also, I ran this tool as "root" and non-root user. However, the same feature is working fine on RedHat, Suse-x, AIX and Solaris platforms.

I suspect that the default PAM configuration on HPUX machine might have caused this issue.

Could anyone help me resolve this issue?
Thank you.