Is it possible to use CHAP authentication with pam_radius?

[Dan Swartzendruber]

I'm trying to implement external authentication for an appliance running 
CentOS 7.  My research turned up the easiest solution as simply 
installing pam_radius from the repository.  I did, and it works just 
fine (tested against a Freeradius 3.0 server with a single test user.)  
Running freeradiux with '-X' indicates that is using PAP:

(0)   User-Name = "XXX"
(0)   User-Password = "XXX"
(0)   NAS-IP-Address = XXX.XXX.XXX.XXX
(0)   NAS-Identifier = "sshd"
(0)   NAS-Port = 15050
(0)   NAS-Port-Type = Virtual
(0)   Service-Type = Authenticate-Only

...

(0) Found Auth-Type = PAP
(0) # Executing group from file 
/etc/freeradius/3.0/sites-enabled/default
(0)   Auth-Type PAP {
(0) pap: Login attempt with password
(0) pap: Comparing with "known good" Cleartext-Password
(0) pap: User authenticated successfully
(0)     [pap] = ok
(0)   } # Auth-Type PAP = ok

For security reasons, I'd really like to use CHAP instead, but it 
doesn't seem to support that?  The man pages and such don't mention 
CHAP.  I went as far as downloading 1.4.0 and extracting the tarball and 
looking at the code.  User-Password is Radius attribute 2, and looking 
at the source:

0 radius.h          <global>             71 #define PW_PASSWORD 2

and

1 pam_radius_auth.c add_password        541 attr = 
find_attribute(request,
                                             PW_PASSWORD);
2 pam_radius_auth.c add_password        543 if (type == PW_PASSWORD) {
3 pam_radius_auth.c build_radius_packet 721 add_password(request, 
PW_PASSWORD,
                                             password, 
conf->server->secret);
4 pam_radius_auth.c build_radius_packet 727 add_password(request, 
PW_PASSWORD,
                                             "", conf->server->secret);
5 pam_radius_auth.c talk_radius         975 add_password(request, 
PW_PASSWORD,
                                             password, old_password);
6 pam_radius_auth.c talk_radius         978 add_password(request, 
PW_PASSWORD,
                                             password, server->secret);

Am I missing something?  Or am I out of luck?  Thanks!